Astronomy Cast » Your Questions http://www.astronomycast.com Take a weekly facts-based journey through the cosmos with Astronomy Cast. Mon, 15 Mar 2010 19:33:33 +0000 http://wordpress.org/?v=2.9.1 en hourly 1 Questions Show: Imaging Extrasolar Planets, Infinite Universe, Inside a Black Hole http://www.astronomycast.com/listeners/questions-shows/questions-show-imaging-extrasolar-planets-infinite-universe-inside-a-black-hole/ http://www.astronomycast.com/listeners/questions-shows/questions-show-imaging-extrasolar-planets-infinite-universe-inside-a-black-hole/#comments Mon, 27 Jul 2009 17:58:01 +0000 Astronomy Cast http://www.astronomycast.com/?p=842 Photo of an extrasolar planet

Photo of an extrasolar planet

What will we eventually be able to see on extrasolar planets? What does an infinite Universe mean? And what's down there, inside a black hole?

If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Imaging Extrasolar Planets, Infinite Universe, Inside a Black Hole

Could we theoretically image continents on extrasolar planets?

What does an infinite universe mean?

What is your opinion of what is in a black hole?  Could we be inside one?

If I'm standing still at the Earth's equator, how fast am I moving?

Is there any limit to when photons would experience time?

What's Fraser's life story?

How likely are the planets in sci-fi where the moons are huge and can be see during the day; or binary planets?

In rocketry what does specific thrust measure?

Download the transcript

Transcript: Questions Show: Imaging Extrasolar Planets, Infinite Universe, Inside a Black Hole

Fraser Cain: Welcome to the AstronomyCast questions show where we answer your questions about space and astronomy. If you have a question for the AstronomyCast team please email it in to info@astronomycast.com and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Hi, Pamela, how you doing?

Dr. Pamela Gay: I’m doing well. This has been a marathon session. The people out there listening don’t realize that we are on episode 4 for today.

Fraser: So this is what we have to do when you’re not traveling.

Pamela: I know. I know

Fraser: Maybe we’ll get to 6, who knows? One little note is thanks for everyone sending in questions. Someone mentioned that they hoped that their question makes it into the question lottery. And that’s actually a pretty good way to describe it. [Laughter] From last night to this morning, I counted like seven or eight questions. When I last checked my e-mail at 11 o’clock at night, to when I woke up this morning around 7 and looked at my e-mail again, there was about seven or eight questions that had piled in.

We do get a lot of questions. We apologize if we don’t get to everyone’s questions. I don’t know what the ratio is, but we get through as many of them as we can. The best way to get your question answered is to make me – I get to be the question chooser – for me to go “Hah, that’s a really good question. I want to know the answer to that too.”

So, if you have a question do a quick search on the site because many of the questions have already been answered and if we feel like we’ve already answered that question, we’ll skip it. The other way is if I can’t quite understand the question, and I’ll put it off because I don’t really get it. Sometimes I’ll sit down and rewrite it but in some cases I don’t get it and I’ll avoid it. That’s maybe to help you make your way through the question gauntlet and win the question lottery.

Alright, so this week, what will we eventually be able to see on extra solar planets? What does an infinite universe mean? What is down there inside the black hole?

Our first question comes from Andrew Branch from Rochester, NY: “Based on our ability to image extra solar planets, especially Earth-like planets over the next 100 years, could we theoretically image continents, rivers, canyons, or even cities on other planets? Are there just not enough photons reaching us?”

Alright, Pamela, how far will we be able to go with imaging extrasolar planets?

Pamela: Well, the problem comes down to two different things. One is contrast. Just how easy is it to tell this bit of orange rock from that bit of red rock?

The other problem is resolution. How small of an object can we see? It will probably be feasible for us to go ooh, land versus ocean on planets that don’t have too many clouds or to say what fraction of the planet might be covered in clouds.

When it comes to getting down to city sizes, that starts to get beyond reasonable resolution abilities.

Fraser: Now, we’re saying reasonable. We’re thinking terrestrial planet finder?

Pamela: Yeah.

Fraser: Technology right? Where you’ve got like a bunch of really big telescopes connected as an interferometer trying to glimpse some planet.

Pamela: Right. Even with potentially using something on its way out to Jupiter in conjunction with something orbiting the Earth where you start getting into really difficult fringe problems.

With radio you might still be able to do it. Even with that getting to city sizes with things that are nearby it starts to become intractable. Continent sizes, that’s nominally feasible in the next 100 years.

Fraser: I think what’s neat though is that scientists are ahead of the curve on this. Figuring out clues on how you might know what is on a planet. It’s the same way that scientists first discovered extrasolar planets, right?

Originally, they were like eventually we’ll have to build a telescope big enough to see Jupiter going around another planet, another star. In fact they figured out well no we just have to detect the motion of the star and detect the planet’s influence through its gravity. We can’t see the planet, but we know it’s there.

It’s very similar to some of the things that are being figured out for actually resolving things on the surface of extrasolar planets, right? Just by the changes of the brightness of the planet we might be able to know where the continents are and where the oceans are.

Pamela: That is the easiest way to start picking these things apart. You look for periodic changes in brightness, and you say ah ha, I get the exact same within a couple of percent change in brightness every day. That tells us the continent versus ocean or at least the bright versus dark albedo difference between different parts of the planet.

Fraser: How it is changing, you would be able to tell whether there is cloud cover. You could, for example, here on Earth we have the heat islands around cities so maybe you could detect strange points of heat going around at a regular basis.

[Laughter] Well you couldn’t see the buildings but maybe you could detect that there is a heat island there.

Pamela: That’s still awful tiny. We’re really looking at continent size things where you might be able to tell the difference between oh I know that half of the planet is supposed to be cold and we have a imagine the density of London or Mexico City spread over all of Europe.

On that scale it really isn’t that dense. If it was that we might be able to see. What we have currently on the planet Earth if we imagine other worlds with that density of humans, we can tell the difference between land not land, forest not forest, on continent size of blobs.

Fraser: You know and that is sort of the reasonable technology. Are there any real limits? Could I build a telescope that is on the moon and is a kilometer across?

Pamela: Even a kilometer is not enough to get there.

Fraser: Really.

Pamela: To be able to discern a 3000 mile wide blob just a couple of light years away you start needing to have telescopes that are hundreds of thousands of miles separated.

Fraser: Right, or a hundred thousand kilometers across.

Pamela: Right.

Fraser: A great big mirror.

Pamela: Yes and I don’t think we’re going to build a mirror that big just due to that we don’t have that many resources. Separating them that much is feasible, but that only gets us to 3000 miles. We want to get to 3 miles. So we have to just keep increasing the size, and increasing the size. Eventually you run out of solar system.

Fraser: I’m going to put my bet on scientists being able to figure out clever tricks to figure out that stuff’s there. [Laughter] Not necessarily to see it like you’re looking at a photograph and there is a city on another world, but to infer that a city is there.

That’s where my bet is going to be. They are going to infer pollution into the atmosphere [laughter] and try to figure out what is going on.

Pamela: I’m with you that they are going to be able to say oh there’s light pollution on that planet. It should be way darker than it is right now.

However, being able to say ah ha, there is a city on that continent. There is another city on that continent. I don’t see us getting there in the next 100 years.

Fraser: Okay. Then the challenge is on. [Laughter] I can’t wait to find out which way it goes. The next question comes from Ninako Shirashi from Tokyo, Japan: “I often hear that in an infinite universe anything is possible. I don’t understand how anything is possible logically follows infinite universe.”

Okay. We have had this conversation before. Is the universe finite or infinite? If it’s infinite, we imagine there are an infinite number of Frasers and Pamelas having an infinite number of podcast recordings on an infinite number of worlds and every gradiation from there. Every slight minor change is also there. There are also an infinite number of Freds and Pamelas recording their podcasts, spacecasts. So, how does this work?

Pamela: The basic idea is there are two different ways of looking at this. First of all there is the Oxford interpretation of quantum mechanics that says that every decision that ever could be is made, and when it is made the universe splits. This is part of the premise of the WebMage book by Kelly McCullough.

There is also the if you make enough planets; every possible type of way of making that planet will happen. In terms of you and me, there you are looking at all the different possible mutli-verses in an infinite universe.

When you start looking at eventually I am going to sit on a chair and you’re going to sit in a chair, and someone else is going to sit in a chair, and somewhere in the universe someone is going to sit on a chair and all of the atoms are going to line up and they are going to fall through the chair.

That one comes with just if you roll the dice enough times, you get every possible combination including if you roll 40 dice simultaneously enough times eventually they are all going to come up ones, even if they’re not loaded. So in an infinite universe, you have the space to roll the dice as many times as you want and have them come up with a world with green eared vulcans.

You have the possibility of having all sorts of just random combinations that we say due to quantum mechanics are very improbable; due to genetics are very improbable. Eventually, given enough worlds, given enough time, given enough space, everything that could be will be.

Fraser: I guess using your dice analogy is a good one, right? If I give you 40 dice and say roll ones and roll it once, chances are you’re not going to get it. But if I say you are allowed to roll those dice as many times as you like, you will eventually come to a point where they will all be ones.

It will require a certain number. I’m sure someone can do those calculations. Because we’re here having this conversation, recording this podcast, means that it’s possible.

Pamela: Yeah.

Fraser: Because it’s possible, it means that it can happen an infinite number of times with every variation that possible. I guess the trick is that you can’t do things that are impossible, right?

We can’t have this conversation and then realize that there is a way that we can move faster than the speed of light and go make a spaceship, right? [Laughter] If from what we understand right now the laws of the universe prevent any than faster than light travel so that will never happen, right?

Pamela: Yeah.

Fraser: I guess the mind kind of boggles at the size and scale of the universe that might be required. The distance you would have to travel to find another Fraser/Pamela having a conversation on that other world.

It’s just enormous. Yet, if the universe is infinite, it has to be happening an infinite number of times. Whoa.

Pamela: [Laughter]

Fraser: Peter McLaughlin from Northern Ireland asks a similar question: “If the universe is infinite, would it be infinite in all directions?” When we have this conversation, we are thinking yeah, head up, head down, head right, head left, North, South infinitely.

Pamela: The thing is infinite does not require that. In mathematics it would be still an infinite universe if it was only infinite in north and south.

Fraser: So there would be a boundary right and left, or up and down, but one dimension could go infinitely.

Pamela: The only thing is I can’t think of any theory that would lead to an infinite universe that wasn’t infinite in all directions.

So, simply saying the universe is infinite isn’t saying it’s infinite in all directions. However, I can’t find a way for physics to build an infinite universe that isn’t infinite in all directions.

Fraser: Right. Okay. Jacob Friday from Ingleside, Texas, asked: “I know there are many theories on what is in a black bole, but what are both your opinions on this matte? What’s in the center? What can it do time wise? What are the possibilities that we are inside it?”

For me, I think my opinion doesn’t matter one iota. It matters nothing. I’m not an astrophysicist. I haven’t done the research. I think that opinion in science can give you some insights and maybe some directions.

A lot of the times your own opinion is kind of a too much opinion is a dangerous thing. I have no opinion. I only have an accumulation of the articles that I’ve written about it. That’s sort of all I’ve got right now. Where do you stand?

Pamela: Yeah. Opinion only comes in when you’re looking at two possible realities that both match experiment, both match theory and you need to run a few more tests. Then you can say my gut tells me this one is more likely to be correct once we’re done running tests.

You can’t base anything on that other than saying this is the one I’m hoping for. You still have to go with whatever the actual final experiment says is true.

Fraser: I’ve got an analogy: it’s like baking a cake and you’re following the recipe and someone forgot to tell you what temperature to bake it at and how long to bake it. So you don’t know.

Should you bake it at 350 or 375 or 400, and for 20 minutes, for an hour? You don’t really know. You have some opinions. You think well probably 375, and probably and hour, but you don’t know until you bake it. Then you bake it and you’re like uhh, I burnt it. That didn’t work.

Pamela: And there’s only one right answer for the perfect outcome.

Fraser: Right. And your opinion can guide you a bit but at the end of the day it doesn’t really matter. You could be totally wrong.

Pamela: And, as far as black holes go, once you’re inside the event horizon we don’t know.

Fraser: Then if you could synthesize the opinion held by astrophysicists, what’s in the middle?

Pamela: The best that we’ve got currently is that there is a new state of matter. Something that is denser than neutron gas.

Something that is denser than anything that we know how that's mathematically handled. There are people who say it’s a quark soup. There are people who say it is just something we don’t know. I can tell you what it’s not.

Fraser: Right, and we have to stay in that place until an experiment has been devised that will get at the answer. Of course, the big problem is that with a black hole nothing comes back out.

Pamela: Right. The best we can really do is to try and replicate the densities using things like the Large Hadron Collider and the future accelerators that will follow it and see if we can achieve that new state of matter.

Large Hadron Collider is not going to get there. The future colliders that get to the as dense as the center of the black hole with significant enough mass to experiment with new states of matter.

Fraser: Right. Jacob wanted to know: “What a black hole can do time wise?” That I think we have more information, right? How a black hole interacts with time.

Pamela: Basically once you’re inside you’re going fast enough that time is approaching zero. It’s one of those neat quandaries. The closer to death you get the less time is passing for people watching you fall in. You’re slowly experiencing time as though nothing strange has happened.

Fraser: What are the possibilities that we are living in a black hole right now?

Pamela: Yeah, we’re not.

Fraser: We’re not. Okay. There you go. What are the possibilities that we are living inside a car crusher right now? A trash compactor right now? Yeah, you could imagine what the possibilities would be. I think you would know.

Pamela: Yes.

Fraser: If you were living inside a trash compactor as it is crushing you? You’d go hmmm. Jason Davis from Springfield, Illinois (isn’t he from The Simpson’s?) [Laughter]: “If I were standing still at the equator, how fast am I moving? Not just the Earth’s rotation, but all the movements into consideration, like Earth’s rotation, Earth’s orbit around the sun, the galaxy, expansion of the universe. How fast am I going?”

Pamela: The question really comes down to how fast are you moving relative to what? This is one of those problems that we run into is how fast relative to what. The ultimate frame of reference is really the cosmic microwave background.

It’s the farthest away thing that is in all directions and we can measure our motion with them. Relative to the cosmic microwave background, we’re moving about 10 kilometers per second. That’s I guess the best thing to go with.

Fraser: Right. Because everything else is relative to what? If we want to talk about standing on the surface of the Earth, how fast are you moving compared to in orbit around the Earth as it were?

Pamela: If you’re standing at the equator and just hanging out on the surface of the planet, you’re moving about a half a kilometer per second, so it’s nothing to sneeze at.

Fraser: Right, okay. But as you look at all of those numbers, the orbit around the sun, the galaxy, etc., it all averages out to 10 kilometers a second relative to the background radiation of the universe.

Pamela: Right.

Fraser: In some cases they cancel each other out. I guess that movement is so great it really overcomes all the other movements.

Pamela: It’s the one we can measure against a solid non-moving fence.

Fraser: Right, okay. Mitchell Shaiat from Oakland, CA asked: “If there is no time for a photon then the frame of reference of the photon it is both at its place of origin and its destination simultaneously. So, is there a limit at how far away this destination could be?”

This is one of those big head scratchers that we’ve talked about. That because a photon is moving at the speed of light it experiences no time. I guess it experiences when it begins and when it ends at the same time. Is there any limit until it would finally experience time if you created a photon year, let it travel for 13 billion years, would that change the no experience of time?

Pamela: Nope.

Fraser: Nope?

Pamela: Nope. It goes splat. As far as a photon is concerned, it’s created, it goes and it splats. And that going part is instantaneous.

Fraser: So if you were a photon you would experience creation and destruction.

Pamela: And nothing in between.

Fraser: And nothing in between.

Pamela: It goes splat.

Fraser: Is there any time from the creation to the destruction? When a photon is emitted let’s say, is there any time there, or is that instantaneous as well?

Pamela: It’s all one breath in a way. It’s created, it’s destroyed. It experiences no time between those two instances.

Fraser: The time from when it is created to when it is destroyed, it doesn’t accelerate. It just goes from zero to speed and then back again.

Pamela: Right. And since it’s never moving at the speed other than in vacuum 300,000 kilometers per second, it never experiences time, ever.

Fraser: Alright. Kyle Lee from Charlottesville, Va., asked: “We know a lot about Dr. Pam’s past and what she does when she’s not recording Astronomycast, but what about Fraser? What’s your story, Fraser? Is running Universe Today your full time job, and how did you go about it? And can you support a spouse and kids doing that? Any tips for the rest of us who are looking to leave our regular jobs?”

You can Google me. You can Google my history. I ran a bunch of software companies. I worked for a web development agency and was doing Universe Today in the part-time. Over sort of enough time, I was having so much fun with it that I just sort of transitioned over to a full time job thanks to my wife continuing to work.

Can I support a spouse and kids doing that? Half. I support this half of the household, and she supports the other half. It’s not a great salary. I definitely was making a lot more money doing software development, but there is some money.

I make money from advertising on Universe Today. I think I beat 99 percent of the bloggers out there in being able to do that. So that’s great. It took 10 years to get from nothing to having this site, be able to support me as my only job. So, that’s pretty cool, I’ve got to say.

Do I have tips for anyone else looking to leave their regular jobs and be bloggers? [Laughter] I think that another blogger, Pamela, can tell me sort of, and can say what it’s like. Do you make a lot of money from Starstryder?

Pamela: I have to admit the International Year of Astronomy has all but killed Starstryder. It’ll come back, it really will. So the year when I was regularly, regularly, posting Starstryder was paying for itself.

Fraser: Like its hosting fees?

Pamela: It was paying all of its own host fees and was paying enough money that I went out and bought buttons from ButtonStar. I love buttons from ButtonStar. That’s not really enough to do anything with other than poke people with stick pins which can be fun, but it’s not useful.

The real side effect for me has been, I’ve gotten to travel to a whole bunch of really cool places because of the doors that being a blogger has opened for me. I think for many of us that is really the biggest benefit.

It’s not that we’re earning a living through blogging. There are a few people out there who are. I’m not one of them, never have been. But it does open up doors to things like Dragon*Con and that’s just cool.

Fraser: Uh, huh. Yeah, I think, as you said, the benefits are that you’re in this great community. You make all these friends. You get to have these great conversations with people and you get to spend your day thinking about the things that most interest you, and the places where you want to play a part.

Pamela: There are times when I think all of us have had that day where we’re the first to find some really cool story, and we blog about it. We don’t just blog the story. We blog what we feel about the story and we encourage action.

Then to see people go out and act on that or think about it or engage in conversation in the comment sections and to start dialogs, that’s one of the really powerful things. The blogosphere is a community where you can start threads of conversations scattered across the Internet and across your comments and you can affect people’s actions. That’s a lot of fun.

Fraser: Uh, huh. So I would think that I have 10 years of experience doing this and I started doing it early enough where I was able to get a lot of links and traffic and stuff like that.

At the same time, there is enough, everyone has these experiences that you can learn from other people’s mistakes. If you wanted to start up today, you could absolutely make a name for yourself in either blogging or news or in the space industry, or any of that. Because everything is so transparent that you can see what we all did, you can see what we’re doing, do it better, and start to attract readers. And…

Pamela: And, join the carnival of space.

Fraser: And there is money to be made. It’s hard to catch up to me and Phil, but at the same time, you can learn what we’ve done and do a better job and do as good as job, and be able to jump up to the top of the queue.

There are a lot of bloggers that have only started a couple of years ago and they are doing really well. It is absolutely possible to make your living through the Internet. There are some wonderful benefits of doing that. All it requires is that you work really, really hard.

Pamela: Yeah.

Fraser: You put in a lot of time, and are able to think long term and able to chip away at what you’re doing. I think we all have to, I know this is going to sound really dopey here, but you have to do what you love.

Pamela: Yeah.

Fraser: If you do what you love and you do it long enough, the money starts to show up. That’s just the reality. If you don’t do what you love, then it’s really hard to get ahead.

So, for everyone listening to the show, just try to do in your life more of what you love and less of what you hate. If there are things you feel like you have to do, you’d be surprised at how you can chop those out and minimize the amount of time of stuff that sucks, and really emphasize doing the stuff that you really enjoy.

In some cases it has to be a hobby and you’ve got to do your job and then that funds your hobby, or sometimes your hobby can be your job. So, they both work.

Alright. Aaron Goodkin from Seattle, WA asked: “Sci-Fi flicks often show Earth-sized, life-supporting planets with multiply gravitationally rounded moons, some orbiting so near that they are visible during the day time. So how likely are these kinds of systems to form? Is it just Sci-Fi?”

I know what Aaron is talking about. You’ve got these you’re standing on the surface tattooing this gigantic moon in the sky. If you go and actually hold out your hand the moon covers the size of your pinky finger now. That’s it. Sometimes it seems like it’s truly big but it’s actually teeny tiny in the sky. So is that possible?

Pamela: Well, it comes down to densities, and it comes down to probabilities. It comes down to how big is the star. Sure, it should be totally possible. In fact, we should be able to even have binary systems where you have two planets that are the same size co-orbiting a central point between the two planets.

We just haven’t found a system like that yet. Now, one thing I do have to point out though is the Earth’s moon is visible during the day. You just go out and look at a quarter moon. It rises at noon or sets at noon, depending on if it’s first or third quarter. You can see the moon most of the day in a crescent form of one shape or another. You’re just never going to see it as more than a quarter during the day except during the summer when the sun stubbornly refuses to set.

This means if you go far enough north you can see a full moon and daylight at the same time during the summer. Or far enough south you can see it during the other summer.

Fraser: Right. But if you get a big moon that is orbiting very close so that it’s huge in the sky, it’s probably not going to be that stable or last that long, right?

Pamela: Well, there’s actually no reason to think that. What it comes down is that you end up with tidal forces and you end up with the two planets tidally locked, but as long as the atmosphere of the one planet isn’t creating drag on the moon, you’re fine.

If the two objects are big enough you can stick them far enough apart that you can still have this amazing size in the sky for an observer, but the two objects are far enough apart that there isn’t any of this drag due to atmospheres.

Fraser: Right we talked about this before. The trick is that the moon can’t orbit the planet faster than a day on the planet, right? If you get below that then that same tidal process that’s happening with the Earth and the moon, where the Earth is slowing down and the moon is drifting away from us, you get that in reverse.

Pamela: Right.

Fraser: The planet speeds up and the moon spirals inward. So that just doesn’t last. As long as your moon orbits slower than a day of the planet, you’re good.

Pamela: Right and, like I said, you also have to be out of the atmosphere. That one kind of comes without saying.

Fraser: Right. That is the situation you have with phobos and Mars. Phobos is within it and it goes around the planet more quickly than the planet takes a turn once on its axis and so it’s on a decaying orbit. In a few million years it’ll crash into Mars.

Pamela: It’s on a death spiral.

Fraser: A death spiral. Austin Adams, from Brisbane, Australia, asked: “I actually had a fairly long question, but I tried to shorten it down. In rocketry, what does specific thrust measure?” So, what is specific thrust?

Pamela: If you look at the total change in velocity and momentum, which aren’t the same thing. Change of momentum is: I have this mass and this velocity at the beginning, and I have this mass and this velocity at the end, which with a rocket your mass is changing and your velocity is changing, so your total change in momentum is a little bit different than we’re normally used to thinking about.

If you take that total change in momentum, that gives you the total force that happened. If you divide that force by your original mass that gives you a mass corrected sense of just how much oomph your rocket has. The specific thrust is: take that total change of momentum, divide it by the original mass of the system, and that gives you the specific thrust.

If you have something that was able to have this enormous change of velocity and very small change in mass, it’s going to have a giant specific thrust. However, if you have a system that has this huge change in mass for the exact same change in velocity, it is going to have a much smaller specific thrust.

Fraser: Right. Okay. What is something then that gives more specific thrust? Is that when we look at say an ion engine versus a chemical rocket?

Pamela: Well, chemical rockets, you’re throwing everything out. But with an ion drive you’re accelerating some sort of an ion, some sort of a charged particle using magnetic fields and spitting it out the back at extremely high velocities.

The amount of mass you’re throwing out isn’t that much. You’re able to given a long enough distance, a long enough time, get your spacecraft going extremely fast. Specific thrust for an ion drive is very high. Specific thrust for a chemical rocket is very low.

Fraser: Alright. I think that’s all we have time for this time. So we’ll talk to you on the next show. Maybe we’ll record more today.

This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.

]]> http://www.astronomycast.com/listeners/questions-shows/questions-show-imaging-extrasolar-planets-infinite-universe-inside-a-black-hole/feed/ 6 Questions Show: Matter Balance, Jumping Light Speed and Black Hole Star Formation http://www.astronomycast.com/listeners/questions-shows/questions-show-matter-balance-jumping-light-speed-and-black-hole-star-formation/ http://www.astronomycast.com/listeners/questions-shows/questions-show-matter-balance-jumping-light-speed-and-black-hole-star-formation/#comments Thu, 23 Jul 2009 16:03:46 +0000 Astronomy Cast http://www.astronomycast.com/?p=829 Black Hole Formation. Image credit: NASA

Black Hole Formation. Image credit: NASA

Why was there a difference between the amount of matter and antimatter at the beginning of the Universe? Mathematics lets us travel faster than light speed, so why can't we? And are there stars forming around black holes?

If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Matter Balance, Jumping Light Speed and Black Hole Star Formation

Why was there a difference between the amount of matter and antimatter at the beginning of the Universe? Do black holes have something to do with this?

Mathematically, we can have a velocity greater than the speed of lights lets us travel faster than light speed, so why can't we?

Can stars form in accretion disks around black holes?

How much precision is needed to keep space telescopes focused on one spot?  I have a hard enough time keeping my camera steady!

How can matter exist with antimatter?

What causes sunspots and do they influence Earth in any way?

How do we know what the speed of light is?  How can we measure something that fast and how did scientists figure that out?

Would life as we know it be able to survive around a Red Dwarf?

Could matter escape from the event horizon of two black holes colliding?

Why is it so bright in the center of the galaxy with a black hole there?

What is behind a black hole?

Download the transcript

Transcript: Questions Show: Matter Balance, Jumping Light Speed and Black Hole Star Formation

Fraser Cain: Welcome to the AstronomyCast questions show where we answer your questions about space and astronomy. If you have a question for the AstronomyCast team please email it in to info@astronomycast.com and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Why was there a difference between the amount of matter and antimatter at the beginning of the universe? Mathematics lets us travel faster than light speed so why can’t we? Are there stars forming around black holes?

The first question comes from Scott Wells from Grand Forks, ND: “Is it possible that the slight imbalance in matter and antimatter was created not at the moment of the big bang but shortly after the universe formed by primordial black holes?”

That’s a complex question there. We’re talking about the slight imbalance at the beginning of the universe where all the matter and antimatter were generated and there was like one part per billion off and so they all collided, turned into energy but there was a little bit of matter left over and that’s what our whole universe is. Scott is asking could that matter actually be formed by primordial black holes. What?

Dr. Pamela Gay: This sort of falls into the let’s use black holes as a cure. [Laughter] They’re not. Black holes don’t care if you’re matter or antimatter. They eat you either way.

When they evaporate they give off matter and antimatter in equal parts. Black holes are kind of the ultimate neutral destruction device. They just destroy everything and then they spit out everything. They don’t care.

Fraser: Right, that’s kind of like that question that we had before. What if a black hole and an anti-black hole collide? You would just get a double the size black hole. [Laughter]

Pamela: Yeah you just get a lot of mass.

Fraser: Double the mass black hole, right.

Pamela: No, sadly we’re still stuck with for whatever reason this one part of physics is asymmetric and we have an asymmetric universe. It worked out for us.

If it wasn’t for that asymmetry everything would have annihilated and our universe would be pure energy and we wouldn’t have life. So we’re kind of glad for whatever went wrong in those beginning moments.

Fraser: Right. Shaun Crandall from San Antonio, TX asked: “According to special relativity we know that nothing with mass can reach the speed of light because the math and physics break down at velocity equals light speed. But at least mathematically it is quite simple to have a velocity of greater than the speed of light. Is it possible that you could jump over the velocity equals light speed and be able to move faster than the speed of light?”

Pamela: No.

Fraser: No. Even though the mathematics works out?

Pamela: Math allows lots of things. Math has no boundaries on it other than certain rules like 2 plus 2 must equal 4. Math isn’t constrained by physical reality. It doesn’t care that you have infinite mass. It doesn’t care that you’re dividing by zero. It simply is.

So while the math will let you have whatever velocity you want the reality of the universe says no c is the ultimate speed and you can’t go any faster than that. It’s very unsatisfying.

Fraser: It’s not that math and physics break down it’s that our understanding is what’s doing the [laughter] breaking down.

Pamela: In this case physics simply says you can’t go faster than the speed of light and the math will let you play but once you start looking at the mass you now have nonsense.

Fraser: Dawn Hoverson asked: “Since black holes can generate temperatures and pressures in their accretion discs is there an appreciable amount of nucleosynthesis taking place?”

I guess what Dawn is asking is around black holes can you have the accretion disc get hot enough and have high enough pressure that you get nucleosynthesis like we have at the core of our sun or even more hotter stars?

Pamela: Yeah and what’s really cool is you don’t even need a black hole. When white dwarfs get too close to a companion star in binary systems – we call this a cataclysmic variable because they’ll start gravitationally grabbing matter off of their companion star sucking it toward them and filling up an accretion disc. Periodically this accretion disc will fill up and undergo nuclear reactions.

We can end up with these nuclear reactions going on not just in the accretion discs of black holes but in the accretion discs of neutron stars and the accretion discs of white dwarfs. When you ask is there appreciable Nucleosynthesis that’s a kind of vague adjective.

It’s like asking have I drunk a lot of water today. I’m not sure. It depends on whose definition you use. There is a fair amount of nucleosynthesis in terms of given how long reactions take place and how much matter is involved. It’s kind of like dealing with a star and that’s kind of cool.

Fraser: Ronald Chan asked: “How much precision is needed to take those long exposures with a space telescope in orbit? I have enough trouble keeping a camera from moving around on Earth with a sturdy tripod and sandbags. How can you keep a space observatory pointed at a subject with enough precision to get a clear image?”

That’s absolutely true you may have Hubble staring at the same object for hours and hours and hours. In some cases with the deep field, it was hundreds of hours. How can you get it not even jiggling just a tiny little bit?

Pamela: It’s a combination of gyroscopes and more gyroscopes – well you can do it with two gyroscopes. They also use a fine guidance camera. The gyroscopes if you’ve ever taken a bicycle tire and held on to both sides of it while it’s not touching the ground and spun it and then tried to rotate it, it’s really hard. Things that are rotating are naturally stable.

On the Hubble space station they have a set of six different gyroscopes that can control the space station very precisely using any two of them. They also have a Fine Guidance camera. The Fine Guidance camera locks on a bright star and it stays centered.

The gyroscopes can be used to make fine corrections to the space telescope’s position. So, you’re constantly imaging using the Fine Guidance camera and you’re using the gyroscopes to keep yourself locked in position.

Fraser: Those gyroscopes actually resist the movement. It’s almost like you’re trying to push the telescope uphill away from where it wants to be to actually make it to move.

Pamela: These gyroscopes are floating in fluid and they actually use the fact that the gyroscopes don’t want to move to rotate the space telescope around the gyroscopes.

Fraser: That’s why you need at least two so you can move in two directions, right?

Pamela: Yes.

Fraser: Three is better.

Pamela: Three is better but they’ve figured out how to use things like the Earth’s magnetic field and other stuff to keep track of where we are in that third dimension.

Fraser: Right but without the gyroscopes those long images would be really hard to take.

Pamela: It would never happen.

Fraser: Okay, next question comes from Joshua Eagles from Australia: “How can matter exist? Shouldn’t we be annihilated by antimatter so that there is no overall net force? Are we in a small unfortunate part of the universe that may have large quantities of matter but over the universe as a whole there is no net value?”

I guess what Joshua is asking is is it really that the universe is all matter? You know after that original – we talked about early in the show – you have the matter, you have the antimatter, they collided and there was a little bit of matter left over and that’s why the whole universe is matter.

Is that the case? Or is it like pockets of matter here and pockets of antimatter over there and later on we might get overrun by a pocket of antimatter.

Pamela: As far as we know we actually live in a universe that is dominated by regular matter. While we do actually interact with antimatter all the time there are only certain reactions that are allowed.

For instance, antimatter neutrinos don’t react at all with normal matter electrons or protons. You probably have antimatter neutrinos of one variety or another flying through your body all the time and your body’s matter just doesn’t care.

You can have positrons and electrons, the antimatter version of the electron and the regular matter version of the electrons. They’ll instantly annihilate against each other.

Proton, antiproton – instantly annihilate against each other. There are only certain types of reactions that are allowed.

What antimatter is flying around all the time we don’t generally have to worry about too much? We live in a matter-dominated universe so we’re okay.

Fraser: We can see matter and antimatter collisions happening around the universe. It gives off very specific energy characteristics. If we looked up in the universe and we saw that kind of energy happening we would say oh wow there’s still lots of matter and antimatter colliding all around us. Get ready for a cloud of antimatter to come through the solar system.

We don’t see that at all. We see some places where there is matter and antimatter colliding but it’s more like it is being caused by something else. We see some around the center of the Milky Way.

Pamela: This is just a matter of different places are producing antimatter and the universe takes care of it for us. We’re okay.

Fraser: Paul Williams from Hong Kong asked: “What causes sunspots and does it influence our Earth in any way?”

Okay a sunspot is a black spot on the sun, what’s causing those?

Pamela: Those are actually places where the sun’s magnetic field has for one reason or another decided to poke itself up to the surface. The sunspots pretty much always appear in pairs.

One has basically a north magnetic pole and the other one has a south magnetic pole. You can imagine the magnetic field arcing between the two different locations on the surface of the sun.

They look dark but they’re actually just a thousandish degrees cooler than their surroundings. If you could see one of these sunspots all by its lonesome they are hotter than an arc welder.

Fraser: Right, they’re only 5,000 degrees Kelvin as opposed to almost 6,000 degrees Kelvin. [Laughter]

Pamela: Right. These are places where the energy has gotten all tangled up in the magnetic field. Periodically these magnetic field lines disconnect and reconnect in the process giving off huge amounts of energy.

They release vast amounts of plasma and high energy particles and high energy electrons all into the space around the sun. That stuff sometimes does head our way and create if we’re lucky, just nice northern lights, nice aurora that we can observe; southern lights.

Sometimes there is too much stuff and it can be dangerous for astronauts. It can wipe out satellites. If the magnetic field of the Earth gets whacked too hard the oscillating magnetic field can generate electric current in already overburdened power lines and take out the power grid.

That is a rather dramatic bad thing, so we generally try and keep an eye on the sun so that we can moderate where the astronauts are, what is the power on the power grid? All of this is in response to the sun’s activities.

Fraser: Right but the sunspots are often the sources of these flares. The coronal mass ejections so they don’t influence us temperature-wise or things like that.

Yes you sometimes get these flares and sometimes these flares give us a pretty light show. They influence our hearts. [Laughter]

John Painter from Millbrook, Ontario asked: “How do we know what the speed of light is? How is it possible to measure something going that fast? It seems as if scientists have known what the speed of light is for at least 100 years, so how did they discover it?”

Okay Pamela, so what is the speed of light?

Pamela: The speed of light is 299792.458 kilometers per second.

Fraser: Is that from memory?

Pamela: No. From memory it’s 300,000 kilometers per second.

Fraser: That’s fast. That’s here to the moon in a second.

Pamela: By definition we have actually defined a meter using and thus defined a kilometer as well, using the speed of light. By definition, the speed of light is 299792.458 kilometers per second. It’s fast.

Fraser: Right, that is fast. You can’t – Channel 9 okay and then I press a stopwatch [laughter] and then the light comes past me and I press the stopwatch again, because the speed of me seeing the light is the speed of light.

Even if I had a car going the speed of light I wouldn’t know to press start until it had just got past me. [Laughter] How on Earth, a hundred years ago did these people figure out the speed of light?

Pamela: It was actually more than a hundred years ago. People first started making measurements of the speed of light back around 1676.

Fraser: Wow.

Pamela: [Laughter] That’s kind of amazing to think about. First we needed the telescope but once we had the telescope it started to become practical.

I’m going to pronounce this poor soul’s name; someone whose name vaguely resembles Ole Rømer was looking at eclipses of the moons of Jupiter. What he noticed was if the moons were traveling toward us the eclipses lasted one amount of time and if they were moving away from us they lasted another amount of time.

He didn’t know the distance to Jupiter very precisely and thus didn’t know the sizes of the orbits very precisely. What he was able to figure out was that the light travel time would be longer if the object was moving in one direction than the other because it would have gotten further away by the time the eclipse ended or gotten closer by the time the eclipse ended.

This ends up changing the duration of the eclipse. He ran all the math and ended up with the speed of light at 214,000 kilometers per second which isn’t bad.

Fraser: That’s not bad at all.

Pamela: No, so that was simply based on looking at the moons of Jupiter. A more precise way is to instead use basically a spinning wheel and mirrors. The first particularly precise measurement that was made was by Armand Fizeau in 1849.

He took a mirror eight kilometers away from where he was planning to stand and had a wheel with teeth – think of a gear basically. He started it rotating and shined a light through it. If he had the rotation rate of the wheel just right, the light would go through the tooth and reflect right back through the next tooth.

He was able to essentially send a pulse of light and measure the pulse coming back. He was looking for basically the travel time for a ball of light which is something that you can figure out.

Fraser: His was very accurate, right?

Pamela: Yeah he was able to actually get 298,000 kilometers per second. He was able to get very precise.

Fraser: This was still a couple hundred years ago so this is an experiment that you could probably do in university? If you had enough careful manufacturing and set up the experiment it’s something that you could replicate, right?

Pamela: You don’t even need careful equipment. This is stuff that people were making prior to having big fancy machine shops. It’s possible to basically go out, buy yourself a nice big mirror, get yourself a chunk of wood and cut notches out of it and attach it to an axle and start it spinning very precisely.

You just need to have some sort of a mechanism to measure the frequency at which it is spinning. You can do that simply by counting how many times does it rotate per minute using an egg counter of some sort.

Fraser: I love it. This is one of the how do we know what we know questions. I think it’s great that people call us on it and ask how do we know and we can go back and look up the history and see the experiments and explain them.

Steve Davis from Rico, Australia asked: “I want to know if life as we know it would survive on a planet orbiting a red dwarf. With the advantage of a long life a red dwarf would seem like a logical place to find advanced life and if so, perhaps we should be listening to them with SETI.”

Red dwarf stars are stars with a fraction of the mass of our own sun. I guess since we have planets going around the sun and one of those planets happens to have life and it is likely there are planets going around a red dwarf.

Red dwarfs are thought to last hundreds of billions maybe even a trillion years. That might be the place where life could really get a chance to take time and evolve and become advanced. Are there any problems with that idea?

Pamela: Yeah, red dwarfs are very angry in their youth. These are stars that when they’re in the process of forming give off massive amounts of x-rays. That’s fine, stars do that no big deal but with a star like our own sun planets like Earth got to keep their distance.

We were a fair distance away from our angry young sun. The planets around red dwarfs that are going to be capable of eventually supporting life have to be just about on top of their parent star. They have to be in extremely close to get enough warmth to be able to have liquid water.

The angry youth of a red dwarf lasts about a million years. It is going to destroy any proto-life that starts to form on a planet that is close enough to have liquid water for those billion years of anger.

It is possible that a planet close to one of these red dwarfs could eventually form life or could be seeded with life from someplace else. We can’t rule them out.

The other thing we do have to worry about though is the planets are so close to their parent star that the probability that they get tidally locked, that just like our moon only one side of the planet ever faces its star is pretty great.

When you end up with tidally locked planets you end up with really weird, really harsh weather patterns. That would make life much more difficult to evolve. But, it’s non-zero. It’s just another place with another set of challenges.

Fraser: But I think a few years ago everyone was like no, there’s no point. It’s not hot enough or the stars are too violent. I know that even at the last couple of AAS meetings there were some really interesting discussions. I saw some neat poster presentations where people were talking about maybe it is not quite so violent.

Maybe you could have a planet move in from further away after the violent period and then settle into a nice orbit. I think there is some really interesting research that’s going on right now to answer that exact question.

You’re right, the implications are if it does seem that they are viable places for life there is lots more regular stars out there than there are stars like the sun. Some of them are very close.

They would make really good candidates for pointing your SETI telescopes out to listen for communications. I think that’s a really good path that scientists are considering.

Pamela: And at the end of the day what we’re finding is any type of a star pretty much can support planets. It’s just a matter of always looking everywhere.

Fraser: Peter Kajodik from Serbia asked: “Is it possible for matter or energy to escape from an event horizon during the collision of two black holes?”

Hmm I guess you’ve got normally, nothing no matter, nothing no light, no energy, no matter can ever escape from within the event horizon of a black hole. But if you have two black holes colliding could you get a scenario where something could escape and leak out?

Pamela: I have to admit I was doing back of the envelope force diagrams. From what I can figure out if you have in isolation two black holes that are in the process of merging, they’re spiraling and spiraling in toward each other. You will end up with things that had had an escape velocity that was speed of lightish and was thus inside of an event horizon.

Because you now have the gravitational pull of the two black holes that escape velocity will sink down so that it is lower and thus you could, if you were able to fire off rocket engines or something, escape. The problem is I couldn’t think of any way to easily induce the force necessary to get that sucker to escape.

You have things spiraling together, spiraling together in the event horizons will move. But I couldn’t figure out how to get something that had previously been inside an event horizon happily orbiting or at least as happily orbiting as you can happily orbit inside of event horizons.

Fraser: Terrified, leave orbiting. [Laughter]

Pamela: Right. I couldn’t figure out how to get any of these terrified orbiting objects to get a force to suck them out in a different direction.

So, yeah you can have something that suddenly is no longer within an event horizon but then I wasn’t sure how to get it out of the system.

Fraser: Right, I guess I don’t know, instinctively and I know when you’re talking about black holes and relativity it’s all pointless, but it feels like if you’ve got an event horizon for one and you have an event horizon for another and you put them together..

Pamela: What you end up with is..

Fraser: Something bigger with a bigger event horizon but it would still encompass both objects, am I right?

Pamela: No that actually, so back of the envelope again what you can imagine is one black hole in isolation ignoring spin is going to have a nice symmetrical event horizon around it.

Another black hole in isolation is going to have a nice spherical event horizon around it. If you imagine bringing these objects closer and closer together what you end up with is basically a flattened event horizon on the sides closer to the two objects because they’re both trying to yank from the other one the point at which you have to exceed the speed of light to escape ends up getting closer to the black hole on the side where the two are closest to one another.

It ends up going out in a teardrop shape away from the center of the two systems. You can imagine basically two teardrops coming toward each other trailing the droppy bits to the outsides.

As they get closer and closer the event horizons flatten more on the side that are facing each other until they reach the point that you end up with one event horizon around both objects. It’s complicated and then once you start adding motion in, it gets even more complicated.

Fraser: You’re saying then that maybe it is theoretically a way you could extract something back out of a black hole. Hit it with a bigger black hole.

Pamela: Well, the problem is then where you get the extra force that gets the thing to come out and a third direction going.

Fraser: Right so it has to be able to use energy then to get out. You’re not going to get it just from the collision itself.

You would have to have something with an antimatter drive that is going to try and push at the right moment [laughter] to take advantage of this unique situation.

Pamela: Or something. The fact of the matter is in general, once something is inside the event horizon it is spiraling towards its death.

Bringing two black holes together you’re going to muck up the distribution of the event horizons and it is possible you’ll move one in.

It’s possible you can yank something around somehow but setting it completely free of the system – no. Not without extra forces.

Fraser: Justin Song from Chicago, IL asked: “Why is it so bright in the centers of galaxies if there are supermassive black holes that suck up that light?”

I know we’ve answered this question in various flavors before but this is an easy one, we’ll tackle it. So Pamela, there’s a black hole at the center of a galaxy, why is the center of a galaxy bright?

Pamela: Because there’s stuff in there other than the black hole that gives off light.

Fraser: Right, stuff waiting to die; stuff being mushed around the black hole.

Pamela: Stuff waiting to die. Even in our own Milky Way as you look towards Sag A stars – you look towards the constellation Sagittarius through all the dust and gunk between here and the center of the galaxy. The inner part of the galaxy is really dense with stars.

It’s that density of swarming stars that in normal galaxies makes the quark quite bright. In quasars in active galactic nuclei that center is even brighter because you have an accretion disc in there that could potentially be so dense that it is undergoing nuclear reactions.

Even if it is not, it is being frictionally heated and generating its own lights. So, it is stuff waiting to die that’s giving off a lot of the light.

Fraser: The black hole itself – it is totally black. Everything around the black hole – we use that analogy of the water going down the drain, right? There’s only so much water that can go down the drain of your bathtub and the rest of the bathtub water starts to spin around the drain waiting for its turn to go down the drain.

The light that we see from the center of a galaxy is that stuff waiting for its turn to be destroyed by the black hole. Black holes are greedy but they’re just only so greedy.

Pamela: Just to make it clear though the center of our galaxy is bright because there is lots of stuff happily orbiting there.

It is waiting to die because everything dies eventually but it’s not necessarily all going to fall into the center of the supermassive black hole.

Fraser: That’s the difference between an actively feeding black hole and a quiet black hole. I guess the center of galaxies there is just a lot of stuff there. There’s a higher concentration of stars, more stars, brighter.

Pamela: It’s like looking at the downtown district of a city. Why is the downtown area so bright? Well there are lots of people with lots of light.

Fraser: Even if someone goes and turns off the lights at the biggest building downtown you’re still going to see all the other buildings. That’s a good analogy. We’ll go with that one.

Mario Massera asked (one of our favorite questions): “What’s behind a black hole? In other words if you go inside a black hole what will you see on the other side? What is on the other side?”

I guess this is sort of a two part question. I guess on the one hand Mario is asking let’s see, I’m standing and looking at a black hole and I orbit around to the other side, what do I see?

Pamela: The same thing.

Fraser: The same thing.

Pamela: Yeah, ignoring spin black holes are nice symmetric round blobs we don’t know what.

Fraser: [Laughter] Blobs of no light escaping, right.

Pamela: Exactly.

Fraser: So anywhere I want to look at it, what I’ll see is nothing. In fact I’ll see sort of a ring of light being pulled in towards it.

The second question is if I actually hop into the black hole what’s on the other side? Like the black hole is a tunnel and I go through my tunnel and I come out the other side, what do I see?

Pamela: You’re just dead.

Fraser: It’s not a tunnel.

Pamela: No it’s death. The big thing is black holes are just big things. They squish you a lot. They squish you to the point that your atoms are no longer atoms.

They’re some extra state of matter that we haven’t figured out how to define yet. So you’re just dead and a new form of matter.

Fraser: Once again helpful analogies, what’s on the other side of that blender? What’s on the other side of that trash compactor? What’s on the other side of that tree trimmer? [Laughter]

Nothing, horrible death is what’s on the other side of it. You won’t be able to get through the other side of that blender and really consider your surroundings.

All it is is a place where a black hole is just a place where things get squished together. Trash compactor, we’ll go with that. What’s on the other side of that trash compactor?

Pamela: Yeah, the trash compactor that never gets emptied, it just gets bigger.

Fraser: Right. That’s all the time we have for questions this week Pamela so we’ll talk to you again later.

Pamela: Sounds good Fraser.

This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.

]]> http://www.astronomycast.com/listeners/questions-shows/questions-show-matter-balance-jumping-light-speed-and-black-hole-star-formation/feed/ 1 Questions Show: Black black holes, Unbalancing the Earth, and Space Pollution http://www.astronomycast.com/listeners/questions-shows/questions-show-black-black-holes-unbalancing-the-earth-and-space-pollution/ http://www.astronomycast.com/listeners/questions-shows/questions-show-black-black-holes-unbalancing-the-earth-and-space-pollution/#comments Sun, 05 Jul 2009 21:48:14 +0000 Astronomy Cast http://www.astronomycast.com/?p=815 Artist's impression of a black hole

Artist's impression of a black hole

Why are black holes black? Can a huge mass of humanity make the Earth wobble? And what's so bad about space pollution anyway?

If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Black black holes, Unbalancing the Earth, and Space Pollution

Why are black holes black?

Can a huge mass of people jumping at once make the Earth wobble?

  • Short answer: no
  • Earth's Mass: 5.9736×1024 KG

What's so bad about space pollution anyway?

What measurements do astronomers use to measure distances in space?

  • Lightyear = 9.4605284 × 1015 meters(distance light travels in one year)
  • Astronomical Unit 1 AU = 149,597,870.691 kilometers (distance from the Sun to Earth)
  • Parsec = 3.08568025 × 1016 meters (distance from the Sun which would result in a parallax of 1 second of arc as seen from Earth.
  • Kiloparsec (kpc): = 1,000 parsecs
  • Megaparsec ( Mpc) = 1,000,000 pc
  • How are distances measured in space — Ask an Astrophysicist

How can we tell the difference between gravitational pull between objects and the expansion of the Universe?

Could energy condensed in a small space create a black hole with its own event horizon?

If you had a flashlight in space and turned it on, could it propel you?

How can you use degrees from Swinburne Astronomy Online and other online courses?

The closer an object accelerates to the speed of light, the more mass it has; if an object accelerates away from the speed of light it should loose mass.  Photons have no mass, so what happens?

If a black hole can have spin doesn't that imply that the mass distribution inside has a finite radius and not a true point singularity?

Could we get the technology to look for planets around other stars and to see pictures of life on those planets and could they look back at us?

Download the transcript

Transcript: Questions Show: Black black holes, Unbalancing the Earth, and Space Pollution

Fraser Cain: Welcome to the AstronomyCast questions show where we answer your questions about space and astronomy. If you have a question for the AstronomyCast team please email it in to info@astronomycast.com and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Hi Pamela, another batch of questions – let’s roll. Why are black holes black? Can a huge mass of humanity make the Earth wobble? What’s so bad about space pollution anyway? From Dave Johnson: “Why are black holes black?” So, are black holes black?

Dr. Pamela Gay: Yes.

Fraser: They are black, okay why are they black?

Pamela: Basically black is defined as the absence of all light. In the case of black holes, light can’t get through them. It can’t come out of them. They just sit there and to use an internet term pwning the light.

Light just can’t get away from them and without light being able to get away they can’t shine so they define the absence of light.

Fraser: Alright, that’s it. They won’t let light go so you don’t see any light and so you don’t see any color. You just see nothing.

T.J. from Ft. Worth, TX asked: “Let’s say in a hundred years there are ten times as many people on the Earth and a vast majority of them were to move over to one side of the planet. Would the weight of those people change the axis of the planet? Would that have any affect on the rotation of the Earth? Would the Earth get thrown out of orbit and go hurtling through the cosmos?”

Let’s imagine a hundred years there’s ten times – so we’ve got 60-70 billion people and they all move over to one side of the planet would that significantly change the rotation of the planet?

Pamela: No. Your typical average not overweight American is about 60 kilograms in mass. The planet Earth is six times ten to the twenty-four kilograms in mass.

When I opened up the calculator on my computer and did 60 billion times 60 and divided it by six times ten to the twenty-four, my calculator came back and said zero. It’s such a small percentage of the Earth’s total mass that it has absolutely no affect on anything.

Fraser: I think there are probably mountains that weigh more than that.

Pamela: Yeah, pretty much.

Fraser: You can’t say nothing because everything has an effect. If you did gather that many people over it would have an affect. It would just be impossible to measure. An impossible to measure number wouldn’t throw the Earth out of orbit.

Pamela: It would be a negligible effect. It’s sort of like the difference in your mass between now and the half a second from now when a grain of dust has settled on the tip of your nose.

Fraser: I think that question of could you throw something out of orbit is even interesting. If you somehow found three more Earths and glommed them onto the size of our existing Earth that would affect our rotation but would it affect our orbit?

Pamela: It wouldn’t actually affect our orbit; now if you whacked the Earth with them.

Fraser: No, no gently sort of pack them together like a bunch of snowballs.

Pamela: Right so say that you had four or six – six is probably a friendlier number – you had 6 more Earth-massed objects that come in and gently attach themselves to the planet Earth. Coming in exactly on the x y and z plus and minus axis so all the momentum cancels out.

If you had this miraculous absolutely no transfer of momentum, no forces, everything sums to zero the Earth plus 6 more Earths would continue orbiting the sun exactly the way we’re orbiting it now. Our mass actually has absolutely nothing to do with it.

Fraser: So where the mass moves over to has no affect. Nothing can kick us out of our orbit from on the Earth. It would have to be some body hitting us from outside the Earth.

Pamela: Right. Some sort of a force would need to be imparted upon the planet with violence.

Fraser: Jordan Jamison from Nashville asked: “Why is pollution in space bad? It’s better than polluting the Earth, right? Aren’t there much worse things in the universe than a relatively small amount of Earth metal, plastics and anything else we might leave? What’s the worst that could happen if we shot our trash to the sun or out into the depths of space?”

Pamela: Trash into the sun actually isn’t all that bad of a thing in terms of just wow, okay that’s one way to get rid of really nasty polluting awful chemical things.

Fraser: That’s also one way to really spend your money.

Pamela: Yeah, it’s kind of expensive. It’s also one of these things of eventually we’re probably going to have to mine our garbage dumps to get resources from them. We only have so many easily accessed resources on the planet Earth.

Everyday we throw away metal. Everyday we throw away rare elements just in our old cell phones, old computers and even the nails in our shoes when we toss them out. Someday that may be necessary material.

If we start shooting all of our garbage off toward the sun, we’re going to be depleting our planet of natural resources. So, yeah garbage is horrible. It smells bad, looks bad and takes up real estate that could be used for other more interesting things.

Someday we’re going to need that stuff. Let’s keep it. The organics will recycle themselves, the metals at least we’ll know where they are. Recycling is by far the best thing anyone can ever do.

Fraser: I actually did an article about this about a year back. I actually did the math. The U.S. produces 208 million metric tons of garbage every day. I figured out that to launch that would cost about 208 trillion dollars a day to launch the garbage.

It worked out to about 5,800 times the United States gross domestic budget just to launch trash into space – all of its trash that it generates. I think the issue is if you fire garbage into the sun, great you’ve gotten rid of it and it is no problem. The sun doesn’t care. The sun has all that stuff already and it will dismantle the chemicals, no problem.

It’s outrageously expensive so it’s not really a great idea. I think when they talk about space pollution we really think about the stuff right around the Earth which is colliding and crunching into each other and breaking up into smaller pieces. Really it’s a risk for astronauts. It’s a risk for the vehicles that we launch out.

Every time the space shuttle comes back down from space it’s got little nicks and dings. A lot of times they have to move the International Space Station or the space shuttle because some glove is going to be coming within [laughter] a kilometer of the space station and they have to move it a little bit to make sure that it’s safe.

The thinking goes that the more junk that gets up there the more cluttered the area is going to be and the more chances there are that something is going to get hit catastrophically. It would really be awful if the astronauts were killed because somebody didn’t clean up their garbage very well.

Pamela: A lot of people will say well space is a big place. So are the oceans of the world and any of you who have ever gone out on a ferry or on a cruise ship there is garbage everywhere. It’s really discouraging to for instance when I’ve taken the ferry from Bar Harbor to Nova Scotia, you’ll be out where you can’t really see land and there are soda bottles everywhere.

If we can manage to systematically cover our oceans in garbage it’s not that hard to systematically fill the space around our planet with garbage. While a cruise ship versus a soda bottle the ship wins, in space you’re dealing with much larger velocities. That soda bottle-sized chunk of satellite that hits the U.S. space station could destroy it.

Fraser: I think the last issue is that a lot of people are worried about spacecraft and stuff from Earth happening to land on Mars or Europa or any of the icy moons around Saturn. The risk here is that life on Earth could contaminate these places.

You might get some bacteria that hitched a ride on a spacecraft, made its way maybe over a million years slowly orbiting the solar system happen to crash land on Europa. It might negatively affect the environment there. While that’s a long shot of course, why take chances?

Pamela: We are our own worst enemy in some ways. We could create biohazards and go off and start all sorts of interstellar inbreeding of bacteria. Yeah, it’s just not something to do. We avoid it as best we can.

Fraser: Lynn Long asked: “What are the measurements astronomers use to measure distances in the universe other than the speed of light?”

Do astronomers use the speed of light as a measurement? I get light years, right?

Pamela: Right. In general we use the speed of light to create our meter stick. Light goes this far in a nanosecond, it goes this far in a day, and it goes this far in a year. You know human beings don’t think in terms of the speed of light.

We do things like within our solar system we measure things in terms of astronomical units. That’s the distance from us to the sun. We also in space tend to measure things in a distance called a parsec. One parsec is a little more than 200,000 times the distance from the Earth to the sun.

Then we just start throwing words in front of it. We have things like kilo-parsecs which is a thousand parsecs. We have mega-parsecs which is a million parsecs.

You can still if you dig through the literature occasionally find really silly to my mind references to huge distances measured in centimeters just because the math doesn’t care.

Fraser: Right this is the number of ten to the power of 27 by all means do it in meters or whatever. It makes the math easier.

Pamela: We don’t generally use feet or miles but everything from centimeters to astronomical units to kilometers to mega-parsecs. All these different things are fair game.

Fraser: There you go. Ahmed Arsen from Chicago, IL asked: “How can we tell the difference between everything being slowly pulled towards a large unseen mass by gravity versus the universe expanding?”

I guess because we see all of these galaxies moving away from us the theory goes that this is the result of the big bang and the universe is expanding. How would that be different from these galaxies it’s almost like they’re sliding off a table towards some mass and that’s why they’re pulling away from us?

Pamela: We can’t actually tell this difference. This is actually one of the new questions that have recently come up. It’s possible if our universe is small enough and you believe in amazing coincidences. If all the right things lined up we could be in the center of basically a bubble of mostly empty universe.

The other stuff in our mostly empty section would be attracted outwards toward things that we can’t see. It’s that gravitational mass of the higher density parts of this giant universe that could exist that things could be attracted to. That could happen. It’s a void hypothesis.

I personally have some problems with this because it does require a huge coincidence. It requires that there is a void that we are roughly centered in that’s at least the size of the visible universe. If we’re not centered in it, it’s absolutely huge. It can incorporate everything in the visible universe.

Fraser: That would be almost like imagine you took a whole bunch of marbles and you put them on top of a beach ball and held one at the very top and let go of all the other marbles. They’re all going to roll away down the hill of the beach ball.

The marble on top is going to say everyone’s moving away from me! I’m at the center of this. That would be true, right? Those marbles all would be moving away from you. That says I guess I’m at the center of the universe. I’m important.

Pamela: [Laughter] Right and just the whole coincidence of it all that it is more than just the expansion of the universe. This is actually the acceleration of the expansion of the universe and is caused by this freak alignment.

That’s a bit hard to stomach when so many of us have spent our entire careers teaching okay they used to think the Earth was the center of the universe but it’s not.

Then they thought the sun was the center of the universe – but it’s not. Then we thought the Milky Way – again it’s not. This would suddenly have us going but we are the center of this giant void. That just is uncomfortable.

Fraser: I guess the solution to that then is to very precisely measure the speed that things are accelerating away from us to see if there is some kind of asymmetry.

Pamela: Asymmetry.

Fraser: Yeah, a lack of symmetry. Then if it is perfectly symmetrical you can feel pretty comfortable that we’re not at the center of anything. If it is asymmetrical then you can say wait a minute it’s kind of weird.

Pamela: We need more supernova observations in all directions so that we can systematically recreate the measurements of the expanding universe more importantly the accelerating expanding universe along many different directions.

Fraser: Krishna from University, MI asked: “Einstein showed us that matter and energy are two sides of the same coin. Does that mean that energy itself if made to condense in an extremely small space can form a black hole with its own event horizon?”

Whoa.

Pamela: Yes.

Fraser: Yeah so if you could squeeze energy down you could make a black hole.

Pamela: In fact the Large Hadron Collider produces enough energy to do this. That’s kind of cool. We can do this with stuff here on the planet Earth we think.

Fraser: Wow, that’s pretty crazy. That’s when they talk about how the Large Hadron Collider is going to be creating black holes.

It’s going to be taking the energy of the particles that it’s smashing together and it will generate enough energy in a small enough space that it will in theory make a teeny weenie black hole for a second.

Then it will dissipate. It’s not even theoretical, it’s like we’re gonna do it.

Pamela: What’s cool is these black holes would, we believe decay very rapidly. This might be that final little bit of experimental evidence that’s needed to give Hawking a Nobel Prize. That would be cool too.

Fraser: I think he totally deserves one so that would be great. David Biltcliff asked: “If you took a flashlight into space and turned it on would the light coming out push the flashlight?”

I guess could it push you? Could you use it as a little propulsion system if you’re out in space?

Pamela: Yes you would just get propulsed – if that’s a word – very, very slowly. In fact you don’t even have to be in space. It’s just here on the planet Earth the friction is a bit much to overcome.

Anytime you emit light in one direction you create a force in the opposite direction. This is a serious problem with some of the big mega-lasers that they build here on the planet Earth.

We have the pettawat lasers for instance that some of the military and research facilities here in the United States when they fire those lasers it makes the entire building shake.

This happens because you have light momentum going in one direction and conservation momentum trying to push the laser in the opposite direction.

Fraser: We don’t want to make people do math but what is the calculation that you might want to make for how much force you’re feeling?

Pamela: The way to look at it isn’t so much with force as with momentum. You have your energy going in one direction at a velocity you know. Take that energy, convert it to mass using the whole e=mc2 thing. Use the speed of light and get the velocity.

Then figure out the momentum of that light going in one direction. Then look at your own mass and solve for what velocity you might end up going in the other direction. It’s kind of sad, pitiful.

Fraser: You would be able to calculate at least how much force it’s emitting back on to your laser or your flashlight while you’re in space.

Pamela: Yeah.

Fraser: That’s how a solar sail works right? A light beam striking the solar sail imparts a force as well.

Pamela: It’s all in something had to either stop moving or get absorbed and the velocity and the momentum imparted by that had to go somewhere.

Fraser: Yeah. You’re going to love this next question. Conley Deacon from Brisbane, Australia asked: “My son is only 8 and recently asked me to explain what e=mc2 means as it has been on the wall at school this term. I have enough trouble understanding relativity and anything mathematical that I am unable to explain to him that he will understand. We don’t want to put him off astronomy for good so can you help me?”

Okay Pamela, can you explain e=mc2 to an 8 year-old?

Pamela: I hope so.

Fraser: Maybe I should get Chloe to come into the room and have her just like [laughter] watch us and then if she gets it she can give you the thumbs up.

Pamela: Here’s how I look at it. Energy and mass is the same thing with a constant. One good way to look at it is if you want to have a bowl of jello you need water and powder. There’s always the same ratio between the jello and the water.

The constant that allows you to get from the water to the jello is the box of powder. Jello and water, same thing with a constant that causes them to change basically you go from liquid to mostly solid stuff.

With e=mc2 the constant that allows you to figure out how much energy can you get out of this mass is the speed of light squared. It’s just a constant, it’s a special constant but it’s just a number.

The way you’re able to figure out how much jello you get out of a thing of water is you have to multiply it by the of powder. Does that work?

Fraser: I think I get it but then I sort of went into it. I think what you’re driving at is that matter and energy are two sides of the coin – they’re the same thing. They’re just two different ways to look at it, right?

Pamela: There’s always this multiplier of if I mixed water a larger amount with a box and a half of powder I’ll get more jello.

You always have to have things in the exact right amounts. If I mix half as much water with the box of powder I don’t get jello.

Fraser: Right you get very weak jello.

Pamela: [Laughter] You get slime going across your counter.

Fraser: Let me take a shot at it too. I think that if you could take matter, anything, sugar cubes and you could convert that into pure energy that would be like nuclear bombs going off. That would be like electricity to run your house. That would be pure energy, rocket launches.

The e=mc2 just tells you how much matter, if you take a sugar cube how much energy you’re going to get out of that. Matter, energy, what’s the number? If you have a car it will give you more energy. If you have a sugar cube it will give you less energy.

I think the most amazing thing is how much energy, because the speed of light in the calculation is so big. You get an enormous amount of energy out of that transformation.

Pamela: Last time I ran the calculations, admittedly New York City was a bit smaller but we were also more energy polluting, but the last time I ran the numbers you could power an entire city off of the energy in basically one potato’s worth of mass.

Fraser: Mark Fritz asked: “Can you offer any advice on Swinburne or any other astronomy programs available? I’m looking for something that is more technical and mathematical.”

Mark already has a PhD.

Pamela: And it’s in the form of engineering.

Fraser: In engineering, yeah. Swinburne – we should disclaim that Swinburne is a sponsor of AstronomyCast.

Pamela: Also I’m one of their instructors and have been one of their instructors since 2000.

Fraser: Right.

Pamela: So we’re fully .

Fraser: Absolutely. Working with Swinburne, anything we say about Swinburne should be taken with a kilogram of salt [laughter] which could then be turned into energy.

Pamela: All of that said, I keep running into past students at science conferences. They’ve gone off, they’ve done great things. They’re still involved in the community in a variety of ways.

They’re mostly involved in the community either teaching at community colleges, working at science centers, working in education and public outreach with a few exceptions. There are some amazing exceptions.

The majority of people who go to Swinburne Astronomy Online are getting a degree because they want to do outreach in education work, not because they want to be research astronomers.

As someone who has a strong technical and mathematical background a terminal Masters Degree designed to help you teach astronomy to non-majors might frustrate you because it will teach relativity from a conceptual standpoint with math.

It won’t go into all of the hard-core math that you need if you’re going to become a researcher in relativity. If you’re looking for the level of mathematical rigor that you’d get in courses that are designed for people who might potentially go on to become researchers in each of those fields versus people who are interested in learning about it and interested in being able to teach things at a popular level and communicate it very effectively to the public so they understand it.

If you want that extra level of mathematical rigor, check out your local state university. There are a lot of universities – my own being one of them – that offer their graduate courses as night courses so that the graduate students can teach classes during the day and do research during the day.

Fraser: If you already had a PhD in a math-intensive area something like engineering, you’ve got to be pretty close to being able to then turn around and go get your PhD in astronomy or astrophysics.

You don’t have to go back from square one, right?

Pamela: No but you do need to go back to day one of graduate school. There is a lot of content knowledge where once I hit graduate school I didn’t take any more math courses except on how to statistically analyze my data. That was a very specialized stats cap class.

Other than that I was doing things like the quantum mechanics of the interstellar media, evolution of galaxies, stellar atmosphere, and stellar evolution. All of these things from a very detailed take the courses you learn as an undergraduate that are general across all of the physics, astronomy and engineering majors and apply them very specifically to astronomy.

There are series of courses that pretty much all astronomers end up taking at the graduate level with varying levels of mathematical rigor depending on what your goal is. People who are going into astronomy education research or education public outreach or people who are going into science communications need enough mathematical rigors to understand the concepts of their core.

They don’t need that extra layer of mathematical rigor that you need if you’re then going to be applying those concepts to going in new directions that no one else has ever gone before. It sounds like Mark might be interested in that extra evil step of okay let’s figure out how to do things no one has ever done before.

Fraser: Would you think he would have to go back to get a new Masters or do you think he could just start with his Doctorate?

Pamela: He’d need a new Masters. Unfortunately in fact astronomy is pretty evil in general where say I had after I got my Masters at the University of Texas had I wanted to go to the University of Arizona to do my PhD, nine out of ten times they’re going to make me redo my Masters.

Masters aren’t generally transferable. You start over. It’s kind of sad but that’s the way it is.

Fraser: Something like Swinburne might be a little more not mainstream I’m trying to think. There’s more focus on outreach and education and rounding you out to be a better communicator for astronomy and teaching what you’re already doing.

You really would need to go back and redo the Masters and redo your PhD switching from Engineering over to Astronomy. That would be like how many more years? Another 2 years for your Masters and another 3+ years for your PhD?

Pamela: Yeah.

Fraser: Another five years at least to get a PhD in astronomy.

Pamela: It’s more typically six to eight actually.

Fraser: [Laughter] Right.

Pamela: It’s kind of bad.

Fraser: Would any of the courses that Mark has with a PhD in engineering be applicable to astronomy?

Pamela: At the graduate level? Only if you wanted to build instruments.

Fraser: Okay, so, Swinburne or go get another PhD. Rack ‘em up.

Pamela: It’s fun. That’s what the astronauts do.

Fraser: Next question comes from Nathan Dye: “I know that the closer something accelerates towards the speed of light the more mass it has. It seems to make sense then that an object that accelerates away from the speed of light loses mass. But photons have no mass and they travel at the speed of light. If a photon is slowed down it can’t lose mass so what happens?”

Can a photon be slowed down?

Pamela: No. They’re quite nice about traveling at the speed of light. There is a caveat here and that is speed of light changes depending upon what media you’re going through.

Fraser: Right so vacuum or atmosphere or water a glass or some ruby crystal.

Pamela: Yes so if you want really slow moving light shoot it through some sort of Iridium gases. Once you compensate for the fact that the speed of light changes from media to media the speed of light is the speed of light is the speed of light.

You can’t slow down photons except by changing what they’re moving through which doesn’t actually change their mass.

Fraser: So, can’t slow them down, so don’t worry about it. Joe Conti from Newton, MA asked: “If black holes can have spin doesn’t that imply the mass distribution inside a black hole has a finite radius and not a true point singularity? So if it was a true point singularity could it not have spin because it doesn’t’ have a radial dimension? There would be nothing to spin.”

Okay I guess this is the question that’s like what is a black hole deep down inside? Is it a singularity where mass is continuing to compress down infinitely small or does it sort of gets to some small size and then just stop into some new exotic form of compressed matter? Would there be a difference between whether those things would spin? Do we know that answer yet?

Pamela: No we don’t. We do know that black holes can spin. In the case of a singularity, it’s actually they’re dragging space time around. You can end up basically twisting up space time which is kind of cool.

What’s spinning is everything. Space, time, frame of reference, everything is getting squinched up and it actually ends up changing the shape of the event horizon depending on how fast it is rotating.

Fraser: Black holes definitely spin. I know that we’ve done a bunch of articles about supermassive black holes that are spinning at the limits predicted by Einstein.

Einstein said here’s how fast a black hole should be able to spin and what do you know, astronomers have found them. Einstein – right again. They’re spinning but how do they know that they’re spinning?

Pamela: We know that black holes are spinning because of the effects of the interface between the event horizon which would be spinning with the black hole and the stuff that’s falling into the black hole.

Depending on the rate of rotation of the black hole itself and the frame of reference around it and everything else it’s able to do neat and interesting things to the accretion discs around it. The way to think of it is if you stick a blender into the center of a thing of cake mix – apparently I’m hungry while talking about this episode – if you stick a cake mixer into the center of a thing of non-moving cake batter and you turn it on and start it rotating first the center is going to start rotating.

Then frictionally it will cause more and more of the cake batter to rotate until pretty much you get this nice rotating cake batter. It’s rotating faster at the center than it is out at the edges. We see the same thing with material falling into a black hole where at the very center the rate at which it’s rotating has to do with the rate at which the black hole is rotating.

Fraser: The fact that we see a black hole spinning doesn’t tell us whether it’s a singularity or it’s some small ball of exotic matter.

Pamela: No.

Fraser: Either one could spin.

Pamela: Yes.

Fraser: Even if a singularity has no width it can still spin.

Pamela: Yes.

Fraser: There you go. The conservation of energy has to happen. The conservation of momentum has to happen. Adam Cordova asked: “We’re seeing light from stars emitted four to13 billion years from the time they were emitted and so then the reverse would be true. From other vantage points our sun is being observed in the past. Could we get the technology to observe planets around other stars and look for evidence of life? Could other civilizations look at us and see evidence there’s life here and even see it in the past?”

Yeah we know that astronomy is a great big time machine. Any star that we look at we’re just looking at what that star looked like in the past. If we look for the light we’re seeing the universe as it looked at that point in time. If you’re looking 12 billion light years away you’re seeing the universe just a billion and one half years after it was formed. So, could we see cities on other planets?

Pamela: No.

Fraser: Like not ever, or just not today?

Pamela: Probably not ever because this is where you start getting into the finite speed of light problem. You need to have such high angular resolution that you’re starting to talk about putting two different spacecraft so far apart trying to image the exact same thing that it’s no longer really useful. Just trying to communicate with the two satellites, get everything lined up it’s just not going to happen.

That said even though we can’t feasibly start looking for individual cities on the surface of distant worlds what we can do even today is start looking at their atmospheres. Right now with little tiny planets we’re not going to really be able to even find them.

With Jupiter-size planets that are close enough into their stars we can start looking at their atmospheres and measuring what’s the composition of the atmosphere. We look for pollution. We look for the signs of organics. We look for loose oxygen.

Oxygen is produced by plants and doesn’t tend to hang out by itself in the atmosphere unless it’s being readily produced on a regular basis. The other thing we can do that’s a bit sad is if the alignments are just right we can start looking for light pollution from other planets. [Laughter]

We can start looking for planets that when we look at them they’re giving off more light than they should. That might be a way to be able to say aha, I found something that appears to have cities on it.

Fraser: Maybe even match it up to additional light to continents and map out the continents. I think once again you’re being trapped by boring reality [laughter] and you’re not really thinking this through to its logical conclusion.

It would be hard but not impossible just hard if you filled the solar system with spacecraft and figured out a way timing perfectly to have an image with a great big telescope you could get some pretty cool angular resolution.

Maybe you would even see something on Alpha Centauri. Maybe the image of the planet’s surface if there’s a planet there. If you could wouldn’t you be seeing what life was like on Alpha Centauri four years ago?

Pamela: If you could overcome all the technical difficulties and all the time lags and everything else including

Fraser: It’s done, I just did it.

Pamela: Okay. If you can overcome all of those difficulties and get the spacecraft far enough apart yet you could image stuff on the surface of other planets given large enough telescopes.

Fraser: You would see it in the past?

Pamela: Yes.

Fraser: Right and so let’s say that the poor folk on Alpha Centauri for some reason lost their history couldn’t we looking at their planet right now be able to record it and go oh well here’s what happened four years ago if they came and asked us.

Pamela: [Laughter] If we knew that we needed to do that.

Fraser: If we knew that we needed to, right, of course. Once again information has to travel the speed of light so they have no way to tell us that they needed us to make a back-up for them. The further out we look a hundred light years away we’d be looking at planets imaging their surface a hundred years ago.

Pamela: Using an even bigger telescope.

Fraser: An even bigger telescope, yeah whatever. It’s the size of ten solar systems whatever. Here, done there I just imagined it so it’s real. The technical problems obviously are staggering, astonishing and a much easier feasible solution is to look for chemical compounds and measure amounts of light and all that.

There are some really amazing research articles being done. I try and write these up whenever I see them. They are really cool ideas on how you might recognize that there is life on a world. They figured out ways to map out the continents and the oceans by the reflected light bouncing off of a moon going around a planet.

As you say, chemical ways to say if you see this chemical compound it has to be pollution. It has to be an industrial civilization. There’s like no other way that could be in the atmosphere of that planet.

You don’t need to see a city. You don’t need to see a car if you see the right pollution in the atmosphere which you could see with a telescope then that’s all you need to know. There are cars, alien space cars but it’s got to be pollution.

Pamela: They’re burning up the same nasty hydrocarbons we’re burning up here on Earth.

Fraser: Then someday they’ll build some ridiculous telescope and really be able to see even better and better. They’ll just look further and further out. I think we’ve run to the end of these questions so we’ll talk to you next time Pamela.

This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.

]]> http://www.astronomycast.com/listeners/questions-shows/questions-show-black-black-holes-unbalancing-the-earth-and-space-pollution/feed/ 9 Questions Show: Avoiding the Heat Death, Orbiting Galaxies, and the Dangers of Space Radiation http://www.astronomycast.com/listeners/questions-shows/questions-show-avoiding-the-heat-death-orbiting-galaxies-and-the-dangers-of-space-radiation/ http://www.astronomycast.com/listeners/questions-shows/questions-show-avoiding-the-heat-death-orbiting-galaxies-and-the-dangers-of-space-radiation/#comments Sat, 04 Jul 2009 15:47:22 +0000 Astronomy Cast http://www.astronomycast.com/?p=804 Orbiting galaxies. Okay, colliding really. NGC 6050 by Hubble

Orbiting galaxies. Okay, colliding really. NGC 6050 by Hubble

Will robots be able to avoid the heat death of the Universe? Can galaxies orbit each other like binary stars? And what are the dangers of space radiation to astronauts on the Moon?

If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Avoiding the Heat Death, Orbiting Galaxies, and the Dangers of Space Radiation

Could we transfer our consciousness to robots so the human race could survive the destruction of the galaxy and the heat death of the universe?

If galaxies are near to each other, will they orbit each other or collide?

If solar radiation is a problem on Mars, isn't it a bigger problem on the Moon?

If I were located on one of the most distant galaxies from Earth, one  that is only exceeded by the Cosmic Microwave Background, what would the sky look like?

Why didn't you mention Herschel in Ep. #132?

I see pictures of stars with bowshocks around them.  Does our sun have one?

I'd like to pursue a career in science journalism — suggestions?

Would geostationary satellites work on other planets?

The Universe is expanding at an ever greater rate, so doesn't this constitute adding energy to the Universe?

If the redshifting of light indicates all matter is moving away from us, how do galaxies and superclusters collide?

]]> http://www.astronomycast.com/listeners/questions-shows/questions-show-avoiding-the-heat-death-orbiting-galaxies-and-the-dangers-of-space-radiation/feed/ 2 Questions Show: Galileoscope, Black Hole Time, and What Exactly is Energy? http://www.astronomycast.com/listeners/questions-shows/questions-show-galileoscope-black-hole-time-and-what-exactly-is-energy/ http://www.astronomycast.com/listeners/questions-shows/questions-show-galileoscope-black-hole-time-and-what-exactly-is-energy/#comments Fri, 26 Jun 2009 18:43:38 +0000 Astronomy Cast http://www.astronomycast.com/?p=793 Galileoscope Logo

Galileoscope Logo

How can you get a Galileoscope of your very own? What happens to time inside a black hole? And what exactly is energy anyway?

If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Galileoscope, Black Hole Time, and What Exactly is Energy?

How can I find a Galileoscope?

Does time stop inside a black hole?

What exactly is energy?

Can energy be converted back to matter?

Why don't we put space telescopes like the Hubble or JWST on the International Space Station so that it would be easier for astronuats to service them?

Is there a limit to how far in space we can see?

Why can't the most powerful photons like gamma rays and X-rays make it through our atmosphere, but on Earth we need lead to protect ourselves from them, while less powerful photons like light come through the atmosphere but can't make it through a piece of paper?

We've heard about the tidal heating of Europa, Enceladus and Io, but how much of Earth's internal heating is due to lunar and solar tidal forces, and how much is due to radiation energy and heat left over from the Earth's formation?

Download the transcript

Questions Show: Galileoscope, Black Hole Time, and What Exactly is Energy?

Fraser Cain: Welcome to the AstronomyCast questions show where we answer your questions about space and astronomy. If you have a question for the AstronomyCast team please email it in to info@astronomycast.com and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Hi Pamela, more and more questions. [Laughter]

Dr. Pamela Gay: They just won’t stop coming.

Fraser: Oh and I just wanted to give you a quick prop. There was a recent review of astronomycast on iTunes which was wonderful. Thank you everybody who has been sending them.

We may have like 600 and something. Someone said sometimes the shows seem a little scripted. I just want to make it clear – there’s no script.

Pamela: Yeah.

Fraser: We’re too lazy for scripts. That would be work. In many cases you have no idea what I’m going to ask you.

Pamela: No. I have absolutely no idea.

Fraser: In some cases we fix when we go down in some wild goose chase in editing and maybe we’ll re-record. But most of the time it’s one cut. I’m asking whatever I want and you are answering them from your vast repository of knowledge which I think is amazing. There’s no script.

It’s time to test you one more time. How can you get a Galileoscope of your very own? What happens to time inside a black hole? What exactly is energy anyway?

The first question comes from Chris Lingre “Fraser and Pamela mentioned a $15.00 telescope in a question show. What are they talking about? I haven’t been able to find one and had no luck locating one online.”

What are we talking about? We’re talking about the Galileoscope.

Pamela: Yes. This is a wonderful project that comes out of the International Year of Astronomy. A group of entirely volunteer folks sat down and designed an amazing telescope that is being sold for about $15.00 plus shipping through galileoscope.org.

We’ll have a link in my twitter feed and the astronomycast twitter feed and as well as on our website. This telescope comes with a Barlow lens, two different eyepiece lenses. You can do all of the observations that Galileoscope did with it and you can do better than Galileoscope.

What’s really cool about it is with one of the eyepiece combinations you’re looking through a system absolutely identical to Galileo’s. Everything is upright. It’s really bad eye relieve, really tiny field of view. It’s just miserable and gives you a real appreciation for what Galileo was able to accomplish.

Take that out, replace the eyepiece and all of a sudden you’re seeing through this really nice 50X telescope. What’s cool is we’ve had Alan Nagler look through it. He actually put one of his really nice eyepieces on it and he was amazed by the view that he saw.

Some really good folks including Rick Fienberg, Editor Emeritus of Sky and Telescope, Steve Pompea of the National Optical Astronomy Observatory, Doug Erin up in Wisconsin, a whole team of people worked together, tested this.

Not only is it a really good telescope but if you’re a school teacher you can also take the telescope apart and use it as an optical bench. You have an optical kit. You have a diverse telescope that mounts on a standard tripod. It’s just a really nice system. Like I said, it’s $15.00 plus shipping.

Fraser: And we’ve both tried them out. I tried it out at the last AAS in winter in California and it was great. It was just great. We looked at Jupiter and we could see the moons of Jupiter. We could see bands on the planet.

You can see the rings of Saturn. You can see beautiful craters on the moon. We looked at the Orion nebula. This is the real deal, it’s a $15.00 telescope, and it works.

Pamela: You can use it with a webcam. It’s really lightweight so if you’re trying to mount a heavy camera on it, not so good. For a standard webcam for a lightweight digital camera it works excellent.

They’re awesome. Buy them for your entire school. That’s the cool thing about this. There are a lot of communities that have gotten together as a community and bought a telescope kit for every single kid in say the 6th grade, in the 8th grade when they’re still young enough to be interested and enthusiastic.

At $15.00 each you can host a local star party for a local classroom of kids and get the local supermarket to sponsor sending the kids home with the telescope they used at the star party.

Fraser: Definitely check it out at www.galileoscope.org and order one, ten, the more people can order then that can help bring the cost down for the volume and make them really stick around.

I think this is going to be a great way to just get more and more people involved and interested in astronomy. It’s the International Year of Astronomy. This is a great way to get involved.

Pamela: Just like with the one laptop per child, you can buy a scope for yourself and buy a scope for a kid in a third world nation that otherwise would never get to use a telescope. Buy one for yourself and buy one for someone you don’t even know and give them a chance to look up and see the stars.

Fraser: Awesome. We have our second question from Nancy Atkinson. If anybody doesn’t know who Aunt Nancy is, she’s a senior editor over at Universe Today and does a lot of the writing on the Universe Today. She actually does the show notes for Astronomycast and is the producer for 365 Days of Astronomy. She’s a part of the team.

Pamela: She keeps us sane. [Laughter] We couldn’t do this without her.

Fraser: Oh yeah. But her other job is a librarian and she got this question at the library. “Does time stop in a black hole?” Which I guess is a good question.

Pamela: It’s a really good question.

Fraser: Why would it stop? Why is it even possible?

Pamela: In the limit that velocity goes to the speed of light the speed of time goes to zero. This is a kind of squirrelly way of saying that the passage of time for someone who is traveling at the speed of light – which you can’t ever do – but if you were able to go at the speed of light – which you can’t do – then your watch would stop ticking.

Your perception of time as neurons in your brain fire would stop as well because well everything would stop for you. Since things can’t actually go the speed of light as long as they’re regular matter time will still exist.

The thing is we don’t know what happens to matter when it becomes part of the black hole. There is stuff falling in – it’s still normal matter. It’s not traveling at the speed of light. It’s just stuck inside the event horizon. Once you start to get to the physical stuff that makes up the black hole, it’s not regular matter in any way that we understand.

We don’t know how to understand it. We know that with normal matter you have regular stars. You collapse it down and it becomes degenerate gas and you get white dwarf stars. Collapse it down more and you get neutron stars.

Collapse it down more and we don’t know what it is. It’s a black hole and it’s made of stuff. We don’t know what to call that stuff because quantum mechanics and gravity don’t speak nice to each other so we don’t know what to do.

As long as the stuff is stuff with mass it’s not traveling the speed of light. It still has some perception of time. It’s probably really slow because we’re dealing with gravitational red shifts.

We’re dealing with it is moving fast before it goes splat. If it becomes pure energy somehow, energy is light and light travels at the speed of light. Light does not experience time so if stuff that becomes part of a black hole becomes pure massless energy then time can stop.

Fraser: I guess part of it though is we don’t even understand does the contraction inside of a black hole ever stop, right? One idea is that the black hole is just some super exotic matter that just sits there and more gets munched on top of it.

It’s very small and very dense but we don’t really know what it is. Another theory is that it’s a singularity that it never stops collapsing.

Pamela: Right and we don’t know.

Fraser: We just don’t know. Good, we don’t know. Moving on, Robert Elms from Brisbane, Australia asked: “Can you please spend a few minutes to explain what exactly energy is?”

The universe is filled will all types energy including matter which we mention is frozen energy. Okay so let’s just deal with that. What is energy?

Pamela: That is one of the hardest questions. We were actually back the first year we were recording astronomycast on a morning radio show in Australia and they asked us this question and we stumbled over it for a while.

At the end of the day the best definition I have for what energy is would be it is something that can do work. It is something that can change direction. It is something that can change velocity. It is something that causes things to happen.

That’s rather unsatisfying but that’s really at the most general level. Energy creates light, causes vibrations, increases velocity and changes the direction of velocity. Energy does all those things.

Fraser: We can have potential energy which is just a rock sitting on the top of a hill, waiting to do work. It has energy in the system. If you let it roll down the hill and if you ignore friction, the waiting energy will turn into moving energy.

Then when it crunches into something it will turn into other kinds of energy. So, it is the ability to do work. I think then Robert is trying to ask “But what is it really?”

Pamela: [Laughter] that’s a question for a philosopher. At some point we need to store up all these questions and find a philosopher and hold them hostage.

Fraser: Naw, a philosopher would be no good to us. But so a photon is energy, a rock sitting at the top of a hill has energy. An elastic band stretched out has energy.

Pamela: The gas in the room that each of us is in – the gas that we’re breathing – it has energy.

Fraser: Yeah, now Robert has sort of a second question which is: “Can energy be converted back to matter?”

Pamela: Yes.

Fraser: It can?

Pamela: Yes. This is actually what happens in particle accelerators. You take two protons or two particles in general – you can do this with all sorts of different particles depending on which accelerator you use – but in general you can take two protons and get them in circles really fast in opposite directions.

One is going clockwise the other is going counterclockwise doing parallel donuts, going really, really fast. Then using magnetic fields you change their paths so they collide exactly head-on.

That’s what is really amazing is they can take two protons, accelerate them to a significant fraction of the speed of light and then get them to hit head on into one another. That’s just cool.

In the process of accelerating we’ve given them kinetic energy. The faster they go the more kinetic energy they have. Kinetic energy is defined in the classical sense as one half the mass times the velocity squared.

When they collide they come to a sudden grinding halt. In the collision all the energy that was in their kinetic energy as well as the energy that was tied up in their mass gets changed into all sorts of crazy stuff including in some cases we hope, the Higgs boson. This is what the Large Hadron Collider is hoping.

Fraser: But you get a shower of particles that are frozen energy. The speed of the particle – the velocity – gets turned into new particles.

Pamela: Yes, new particles that flash out in all different directions. We catch them in webs of fiber optics and we measure the velocity, their passage through the fibers. We measure their mass. We measure as many different things as we can.

Then we backtrack and put the pieces together and go aha, there was one particle here. That one particle decayed into these two particles and light. We’re able to reconstruct how the matter and energy flashed back and forth between having mass and being light and being both mass and light throughout the process of the collision and the shower of particles and the decays that follow after.

Fraser: Right now with our current technology all you can do is smash protons together and get a shower of particles. It is theoretically possible that you could smash particles together out could come trucks and puppy dogs and water and sandwiches.

Pamela: Right. At a certain level you and I are converting mass into energy every moment. We’re just not doing it via nuclear processes. We’re doing it via chemical processes.

Fraser: That’s the other way, right? That’s the opposite. We’re talking about how we’re getting energy turned into matter.

Pamela: Right that’s true.

Fraser: Then obviously we can turn matter into energy using a chemical process or just take antimatter and matter – put them together.

Pamela: That’s a bit violent but it works.

Fraser: Don’t you get two pieces of matter turning purely back into energy? [Laughter]

Pamela: Right you get two bits of mass – one matter and one antimatter – that if you have the right channel so electron and positron work really well at this. You collide them together and you get pure energy.

Fraser: Or a sandwich and an anti-sandwich. [Laughter]

Pamela: Exactly.

Fraser: Those will turn into pure energy. We can go from energy to matter and we can go from matter to energy and in a nuclear explosion, right? That’s matter to energy.

Pamela: Right.

Fraser: I guess Robert’s last question: “Will energy that exists today turn into matter or will matter turn into energy, or are we just kind of stuck with what we’ve got?”

Pamela: It’s a little bit of both. We use energy in all sorts of different processes. Some of the stuff that exists as energy today – that’s getting generated and a star getting generated, nuclear processes – some of that energy is going to freeze out into different particles eventually.

At the same time when you look really long term, when you look at the inevitable death of the universe – which has to come up once per episode – one of the things that a lot of particle theorists think may be true is that protons will decay.

This means that we’re looking at an eventual future where all matter decays. We’re left with basically a fuzz of energy spread out across this extremely, extremely large cold, cold universe.

Fraser: Right and so that might be the future that all the matter will just turn into energy and then it all gets spread out and that’s that. Energy – what is it? [Laughter]

Let’s move on. Mitchell Shyat from Oakland, CA asked: “Why can’t we just attach telescopes like Hubble or James Webb to the International Space Station or at least placed in an orbit nearby and that way if something goes wrong it could be fixed immediately?”

So, why didn’t they attach Hubble to the International Space Station somehow? The astronauts could just stick their eyes up right up to the eyepiece of the Hubble Space Telescope and take a look. [Laughter]

Pamela: People move – that’s the real problem. Because people do things like bump into the sides of the International Space Station and tap their fingers on the side of the station, the station constantly is vibrating.

The station has fans to control the air processing system. It has fans to control the waste processing system. It has all these different things that generate all sorts of different vibrations. All those vibrations would wreck images. You don’t want to attach telescopes to anything that human beings are attached to.

In fact when we build big observatories here on the planet Earth they’ll actually build the telescope on its own pier that isn’t attached to the building. There is usually an air gap of several inches all the way down through the center of these big observatory buildings between the floors that people work on and the actual pier of the telescope which goes all the way down to bedrock.

You’ll have this separate foundation for your telescope and for the building built around that telescope just to isolate the vibrations.

Fraser: You’re going to have heat coming off the space station which is going to cause problems. There’s going to be light pollution perhaps coming off the station.

Pamela: And then there’s just the well you have to contend with astronauts. You have to contend with the space shuttle.

You have to contend with the different supply vessels. The International Space Station is pretty complicated. Let’s not add a telescope.

Fraser: They sort of split the difference with Hubble. They put it in Earth’s orbit and made it so that it could be picked up and serviced by the shuttle. I think with James Webb they just said what’s the best place to put a telescope? Let’s put it there and not think about how we’re going to repair it.

This is what was done with WMAP. It is out in the LaGrange Point. A nice stable, dark place free of electromagnetic radiation and heat and all that. That’s just a good place for a telescope.

I guess that’s it, right? Some places are good for telescopes and some places are good for you to go and work on them. In the case of those telescopes they’re going with best place for telescopes – science first.

Pamela: Exactly.

Fraser: Daniel Ebdriptasked: “In episode 136 Fraser said that there is no minimum to the wavelength of the radio spectrum but isn’t the Planck length a theoretical minimum of anything including radio waves?”

I had said that I guess no minimum wavelength. In other words you could go past gamma rays and get smaller and smaller wavelengths.

Pamela: Which we’d still call gamma rays.

Fraser: Which you’d still call gamma rays even if they were 100 times more powerful, 1000 times more powerful, a billion times more powerful. Those would still be gamma rays.

You could keep on going forever shortening the wavelength and still be well within the laws physics. Daniel says: “Whoa not so fast. Isn’t the Planck length the limit?”

So what’s the Planck length?

Pamela: The Planck length is length scale at which gravity should be quantized. This is when we start trying to figure out if I look for natural units, if I start figuring out at what point does everything get quantized? At what point does everything start behaving following quantum mechanics?

I end up with certain Planck masses, Planck times and a Planck length. In theory you can’t ever get smaller than any of these things without entering pure quantum mechanic chaos. Everything is determined by probabilities slant.

The Planck wavelength is four times ten to the minus 35th of a meter. It’s really, really tiny. He’s right, he caught us. We goofed. You in theory shouldn’t be able to have a wavelength that is smaller than this ten to the negative 35th of a meter.

Kudos to him. If you do go the other direction, if you start looking at longer and longer wavelengths, there I don’t think we have a limit other than the size of the universe.

Fraser: Right so a universe length. Ramez Nadum from London asked: “Is there a limit to how far into space we can see even if we built the most powerful telescope possible?”

Is there a limit?

Pamela: Yes.

Fraser: There is a limit. What is that limit?

Pamela: The cosmic microwave background. It is this kind of impervious wall behind which we can’t see. It’s where the universe becomes opaque. Prior to the cosmic microwave background radiation decoupling from matter the entire universe was as opaque as the densest fog that you’ve ever been in with your high beams turned on.

Light tried to move through space but it was constantly getting absorbed and readmitted by the extremely dense material around it. So you have this complete coupling of light and matter and we can’t see through that opaque dense period in the universe. We can only see the moment at which they decoupled and the cosmic microwave background is released.

Fraser: So we already have instruments that can see this limit.

Pamela: What we’re working to build now is instruments to allow us to see really well the stuff between us and that limit.

Fraser: Right and that’s where we can only see galaxies with any resolution out to a few billion light years away and use special tricks. The James Webb telescope is going to come along and extend that view much, much further out.

What would you say right now is sort of a limit for what we can see with our best telescopes? Like with Hubble doing its deep field view?

Pamela: We’re able to see things from a few million years after the cosmic microwave background. We’re limited to only being able to see the very brightest, very largest objects that are in the process of forming.

It’s the Holy Grail is being able to start seeing the normal objects at the beginning of the universe. To start seeing regular galaxies in their infinite stages as they’re just starting to collapse out of many different combining small blobs of gas.

Fraser: Right to try and get a sense of what those first stars were.

Pamela: Exactly. We’re struggling right now to be able to see the normal stuff at the beginning of the universe as well as the big giant really glowing bright stuff.

Fraser: Okay. John from Milbrook, Ontario asked: “Why is it that the most powerful photons, gamma rays and x-rays, can’t make it to the surface of the Earth through our atmosphere but they require lead to protect us on the ground? Why can the less powerful make it through the atmosphere but can’t get through anything thicker than a piece of paper, like light?”

That’s a good question. Gamma rays will blast your DNA out if you let it and yet it can’t make it through the atmosphere. Light can make it right through the whole atmosphere but can’t go through a piece of paper.

Pamela: The beauty of this is the depths of which we expect things to travel through. Our atmosphere is conveniently thick. This is one of those really nice things that allow airplanes to be able to fly several miles up.

The higher up you go on a mountain the more radiation you’re actually going to start encountering, the more UV you’re going to be able to pick up. We can actually fly balloons high enough still within the atmosphere that they’re starting to pick up microwaves that are otherwise blocked by our atmosphere. They’re able to start picking up gamma rays.

The reason that we don’t get blasted with gamma rays and x-rays here on the surface of the Earth is we have different characteristics of our atmosphere predominantly the ozone when it comes to things like the ultraviolet that are absorbing different colors of light.

If you only have the amount of air that is between me and my computer screen, between me and the other side of the room, that amount of air isn’t enough to guarantee that all the x-rays and gamma rays are absorbed. If instead I have several miles of atmosphere, this several miles of atmosphere are able to make sure that pretty much none of these dangerous particles reach the surface of the Earth. It just takes a lot of distance.

Now at the same time, those molecules in the atmosphere don’t care about visible light. They happily let all the visible light pass through. Water in the atmosphere is another one of those things that likes to absorb. Happily, visible light passes right through all of the water vapor in the atmosphere.

At the same time a piece of paper goes nope, visible light is too thick to go through me, the gamma rays and x-rays are able to snake right between the atoms and molecules in the piece of paper.

Visible light can’t do that. It’s all about what absorbs what colors. What absorbs what wavelengths? Molecules in the atmosphere specifically absorb the gamma rays and the x-rays but they let through the visible light. A piece of paper the stuff in the paper is dense enough to block the longer wavelengths the bigger wavelengths of visible light but the x-rays and gamma rays pass right through.

Fraser: Hmm. It is counterintuitive. You think it’s so powerful but in many cases it just comes down to what absorbs what.

Pamela: Exactly and there are very specific fingerprints of colors which we talked about a couple episodes ago that are absorbed by different atoms and molecules.

We got lucky and live on a planet that’s safe for life because the specific contents of our atmosphere absorb these dangerous wavelengths.

Fraser: Like a radio will go through a piece of paper.

Pamela: Radio will happily go through a piece of paper.

Fraser: So will infrared.

Pamela: Infrared actually won’t go through that piece of paper.

Fraser: Oh that’s right, but radio for sure.

Pamela: Radio for sure. You can’t block your cell phone signal with a piece of paper.

Fraser: Right and so on both ends of the spectrum ha-ha it gets through. That is kind of neat. Okay, let’s move on.

Dawn Hoverson asked: “We’ve all heard of the tidal heating of Io and Europa but what I want to know is how much of the Earth’s internal heating is due to the lunar and solar tidal forces and how much is due to radioactivity and leftover heat from its formation?”

Io is a great example, right? Io is locked in a tidal battle with Jupiter. It’s getting squished and squeezed and this tidal heating makes it the most volcanic object in the solar system.

It would be cold and dead but because it’s getting smushed and squished the friction of this is keeping it hot and very volcanic. Is that going on with the Earth at all?

Pamela: You know I did a quick search trying to find heat generated with the Mares Plate Tectonics due to tidal forces and I just couldn’t find anything that talked about this as being anything significant.

What it turns out is the major reason that the Earth is actually warmer than it should be based strictly on how much light we receive from the sun. It actually turns out that things like radon, the radiation released by decaying particles in granite just all sorts of random decaying stuff scattered all throughout the Earth’s crust is the major source of heat here on the planet Earth. We do still have residual heat from when the planet was formed.

Fraser: Okay so if you took the Earth as a blob of molten rock, let it cool but kept shining the sun on it to warm it up a little bit and let it cool and let it cool we’re hotter than we should be after 4.6 billion years because of radioactive rocks inside the Earth.

Pamela: It’s all about the energy released by all those nuclear decays that cause radon in your basement. Or at least radon in my basement, I don’t know if you have radon in your basement.

Fraser: I don’t think we have radon in our basement. [Laughter]

Pamela: So yeah our planet is rather radioactive and granite is one of the major sources at least of day to day background radiation. We have all sorts of pockets of radioactive materials scattered all through our crust. All of those decays are releasing heat and keeping our planet nice and toasty warm.

Fraser: If we were moved into the orbit of Io then it would switch over to tidal heating would be the major force that is going on.

Pamela: But luckily we’re not there and so we have a much more stable planet and we’re happy for this.

Fraser: Yeah. I think we have run out of time. We will pick this up next week with more questions and more regular shows. Thanks a lot Pamela.

This transcript is not an exact match to the audio file. It has been edited for clarity. Transcription and editing by Cindy Leonard.

]]> http://www.astronomycast.com/listeners/questions-shows/questions-show-galileoscope-black-hole-time-and-what-exactly-is-energy/feed/ 9