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 firstname.lastname@example.org and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.
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
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 email@example.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?
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.
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.
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 fromfrom 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 everom 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.
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?
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.
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 homathematically 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.
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.
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. Mitchellom 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. 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.
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.
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.
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.