Edwin Hubble

You might know the name "Hubble" because of the Hubble Space Telescope. But this phenomenal observatory was named after one of the most influential astronomers in modern history. Hubble discovered that galaxies are speeding away from us in all directions, leading to our current understanding of an expanding Universe. Let's learn about the man behind the telescope.

Ep. 112: Death from the Skies, Interview with Phil Plait

Phil's Bad Astronomy website

All about Phil

Order a copy of "Death From the Skies!"

Death by Asteroid

• Will blowing up an asteroid work? – MSNBC
• Bad Idea:  Blowing Up Asteroids with Nuclear Missiles – Universe Today
• Movies w/bad science that Phil debunks on his Bad Astronomy site
• B612 Foundation
• The B612 Foundation's solution to potential asteroid strike
• Gravity Tug
• Pan-STARRS
• Large Synoptic Survey Telescope
• Dan Durda
• Apophis – Universe Today
• Mining Asteroids — How Stuff Works

Death from the Sun

• The Sun's magnetic field – Goddard Space Flight Center
• How to project the sun onto a piece of paper — Standford University
• Solar Maximum of 2003 -- Space. com
• Alpha Particles — Wiki
• Solar Flares, or Coronal Mass Ejections — Marshall Space Flight Center
• The Quebec Blackout of March, 1989 – Windows to the Universe
• History of the Sun – Universe Today
• 2012: No Killer Solar Flare -- Universe Today

Misc.

• Moving the Earth — New Scientist
• Gamma Ray Bursts — Goddard Space Flight Center
• Eta Carinae – APOD
• WR 104 — Universe Today

Don't forget to vote for Astronomy Cast in the People's Choice Podcast Awards! The Technology/Science section is near the bottom of the page.

Download the transcript

Transcript: Death From the Skies, Interview with Phil Plait

Dr. Pamela Gay: With me this week is ‘The Bad Astronomer’ Dr. Phil Plait. How are you doing Phil?

Dr. Phil Plait: I’m doing just fine.

Pamela: How does it feel to be an author nowadays?

Dr. Plait: Well, I’ve been an author before but when you do it once it could be a fluke. If you do it a second time then that’s showing that you might have a little bit more credibility. So I’m pretty happy to have another book out. It seems to be doing fairly well so I’m excited.

Pamela: Well and we’re excited to have you here today. As we’ve talked about a lot on this show, the Universe is trying to kill you, me, and everyone in the world. Death can come in many forms but thus far the planet Earth has managed mostly to make it out okay. So far at least we have – as long as you don’t happen to be a dinosaur.

Today you and I are going to talk about a few of the most likely and most interesting ways we may not be able to avoid death in the future. I guess the best place to start is what’s the most likely way that we could all die?

Dr. Plait: [Laughter] Actually calculating statistics on Astronomical events is a little tricky. The Sun IS going to turn into a Red Giant and it IS going to fry the Earth but not for another 6 billion years. So, the odds of you and me dying in this are zero. That’s the most likely kind of thing that’s going to happen – something inevitable as far as us listening to the Podcast or just living our lives today, far and away the most likely event is an Asteroid or a Comet impact simply because there are so many of them out there and it doesn’t take a really big rock coming in to cause a lot of damage.

So, the smaller the rock the more of them there are. There might not be that many dinosaur killers out there, the rocks that are 10 kilometers across (6 miles) but there are lots of little ones you know, a hundred yards across. Those can’t wipe out all life on Earth but if they come over a city, that would be bad.

Pamela: Now, we’ve all seen in movies and we can name these movies (although we shouldn’t because that would give them attention they don’t deserve)…

Dr. Plait: [Cough, cough – Armageddon]

Pamela: [Laughter] We’ve all seen these movies where they try and get rid of the problem by blowing up the rock. This is a really bad idea.

Dr. Plait: Well, yeah it’s bad for a lot of reasons. One of which is like imagine this thing is the size of Mt. Everest, 6 miles across something like that and it’s made of iron. A lot of Asteroids are made of iron. You can drop bombs on something like that all day long and it’s just going to laugh all the way down.

All you’re going to have happen is now you’ve turned an Asteroid impact into a radioactive Asteroid impact. That’s not very good. [Laughter] If we see an Asteroid coming in we may not know what it’s composed of. It might be iron; it might be rock; it might be what they call a rubble pile. Some of these Asteroids are basically shattered in place by low speed impacts. It’s like a bag of rocks or gravel. You can lob bombs at that and it just absorbs the impact and nothing happens.

So this argues that we should really be studying these things so we understand them better. We should be funding this better. We just don’t know enough about these kinds of Asteroids. So really just trying to blow it up isn’t a good idea especially if like at the end of the movie ‘Deep Impact’ which I watched actually last night as we were recording this they blew up a Comet 6 miles across when it was minutes away from impact. All you’re doing is taking one giant impact and turning it into a gazillion somewhat smaller impacts spread out all over the Planet. So you’re not really helping any.

The thing you REALLY want to do with these is to make them not hit [Laughter] the whole problem is they’re hitting us. If you make them not hit then you’re okay. You want to push them out of the way. You can think of a lot of ways of doing this. You can land a rocket on one and stick the back end of it straight up and use that to push it.

The problem with that is these rocks are spinning or tumbling and so you can’t really control which way your rocket is blasting and you want to be able to control this. You can in fact blow a bomb up on the surface of an Asteroid and then you’ll vaporize part of it and that vapor will expand and act like a rocket and push the Asteroid in the other direction.

Pamela: But again if it’s tumbling you’re still going to have problems.

Dr. Plait: That’s right and you can’t really control how much you’re pushing it. You might push it into an orbit that is only marginally dangerous into an orbit that’s VERY dangerous.

There’s a group of people called the B612 Foundation. They’re named after the little Prince who came from an Asteroid called B612. They want to put a Space Probe, a rocket off the side of an Asteroid not physically touching it but near it. This probe might have a mass of a couple of tons something like that so its own mass gives it Gravity. That Gravity can pull on the Asteroid.

So the Probe very gently fires its rockets and can tug the Asteroid out of the way using nothing but its own Gravity. It’s called a Virtual Tether or a Gravity Tug. This is a cool idea – it sounds ridiculous – but in fact these guys at B612 were talking – Astronauts, Astronomers, Engineers, smart folks – and they’re really out there trying to get this done, trying to figure out how to do it. It’s a brilliant idea and honestly I think it will work.

Pamela: And the nice thing about this is Gravity doesn’t care if the Asteroid is tumbling. Gravity doesn’t care in fact about anything other than where the heck is the center of Mass of the Asteroid.

So you launch something roughly the size of a fully-loaded semi-truck which you might have to do in 2 or 3 different trips to get all the pieces into orbit and we can practice ahead of time. We don’t have to wait for something to be on its way to destroy the Planet.

You take something out to the Asteroid Belt and just rearrange the Asteroid Belt a little bit to test out how well this process works. It’s completely straightforward. The math is completely straightforward. The hard part is figuring out how well we can maneuver in that sort of a situation.

Dr. Plait: Yeah, so the other thing it cares about too is the mass of the Asteroid. So if you have a REALLY big Asteroid you need a lot more time to be able to move it where you want as opposed to something smaller which you might just be able to move a lot more quickly.

The thing is these guys are threading the needle. These Asteroids are coming in and the Earth is 8,000 miles across so the earlier you can push this thing out of the way, the wider it’s going to miss the Earth by when it passes. What you really want is a lot of lead time so you don’t have to push it so hard and the lower mass Asteroid the better because then you don’t have to push as hard to get it out of the way in the first place.

The problem is we cannot control those things. Whatever is going to hit us is going to hit us. We have to keep our eyes open, check for these things and get as much lead time as we can.

Pamela: Well one of the problems about Asteroids in general is the Earth-crossing ones are often on highly elliptical orbits and that has some rather severe consequences. It means the one that’s likely to hit us is likely to come out of the Sun or at least the Sun’s direction. Those are kind of hard to see.

Dr. Plait: Right, a lot of the times you’ll read the newspapers and it’ll say we were just missed by an Asteroid last night. That’s really irritating. If you draw yourself a picture, if an Asteroid is coming past the Earth the only time we can really see it well is when it’s already on its way by.

When it’s coming towards us it might be coming from the direction of the Sun or it’s coming from a direction where the geometry makes it look like the Crescent Moon does – it’s not lit very well. So, it’s dark and just coming from a funny direction.

A lot of the times we really don’t discover these things until after they’re passed us. Look that’s a bit of a worry. We need to be searching for these things with even more eyes on the Sky than we have now to make sure we don’t miss them.

Pamela: So coming on-line in December is this wonderful system called Pan-STARRS that is going to be basically observing all of the Sky that it can every night, night after night after night and automatically subtracting one night’s images from the previous night’s to see if there is anything new or if anything moved. This system is going to be able to find Super Nova; it will be able to find Asteroids. It will be able to identify Variable Stars that we never knew about. It’s going to basically look at our inconstant Sky and nail everything that’s not constant very rapidly.

Hopefully this is going to be a way that we can find things that reflect light effectively. Once it is going, a few years later there is another system called the Large Synoptic Survey Telescope that is even bigger and will be able to find even smaller rocks.

Between these two systems, we should be able to get to the point that we’ve found close to all of the Earth-killing Asteroids and hopefully order of (I think they’re tasked with something like 90 percent of the Continent-destroying size rocks) it’s not everything.

Dr. Plait: A friend of mine, Dan Durda, I’ve actually known him for many years, is an Asteroid Specialist. He’s actually president of the B612 Foundation. He and I were talking the other day and he said the goal is to find 90 percent of all Asteroids that can cross Earth’s orbit that are bigger than 140 meters by the year 2025.

One hundred forty meters is sort of a combination of the smallest ones that can do a lot of damage that are also findable basically. If they’re much smaller than that they don’t do much damage and they’re harder to find. You take all of these factors into account and 140 meters seems to be about the right size to be looking for. Finding 90 percent of them in the next 17 years or so is a pretty good goal.

Pamela: That’s where we’re headed and we’re getting better at finding these things all of the time with new technologies, new ways to automate the search. It’s a fun way to go out and basically protect the planet Earth.

We’re working on finding ways to tug these things out of place when they are on bad trajectories. The nice thing is we’ve found a lot of them already. We’ve found significant double digit percentages we think of them already using statistics. As far as we know there is absolutely nothing headed our way.

Dr. Plait: Not at the moment. There’s nothing with a reasonable chance of hitting in the next few decades. There are some like the one called Apophis which is about 300 yards across, 300 meters across that’s going to pass by the Earth in 2029. We don’t know exactly how far away from the Earth this thing is going to pass. It’s actually very hard to know that this far in advance. As it gets closer we’ll know better but right now we don’t know.

The point is if it passes a little too close to the Earth, the Earth’s gravity will swing it really widely around into a different orbit. If it doesn’t pass close enough to Earth, the Earth’s gravity will only bend its orbit a little bit. If it passes at just the right distance, what Astronomers call the Keyhole; it will come back in seven years and smack us in 2036.

We really don’t want that to happen because something 300 yards across is BIG. That’s bigger than a city-killer by far. You don’t need anything anywhere near that big to wipe out a city. We don’t want something that big hitting us anywhere.

They’re taking this Asteroid seriously even though the odds of it hitting us are like one in 45,000 or something like that, very small. But they want to put a radio beacon on it actually so we can track its orbit perfectly. If it looks like it’s going to come back and hit us, use a Gravity Tug, put one of these things together and move it out of the way.

One of the things I really like about this is besides being able to keep us from getting all killed – which is something [Laughter] I’m all for that –

Pamela: But it would sell your book so well [Laughter]

Dr. Plait: That’s true as a promo I couldn’t ask for anything more. But one of the things that’s good about this is if you can move an Asteroid out of the way, you can move it into an orbit that might help you.

If we see one that’s a couple hundred yards across and made totally of metal (these things are iron, nickel and things that are actually difficult to mine on the Earth) we can actually move it into an orbit which is beneficial.

You move it into an Earth orbit and take your time and 20 years later you go back to it and start mining it when you have the technology to do that. It would probably pay itself off in just a few years.

Pamela: So it could kill us or it could help us build the next generation of autos.

Dr. Plait: Right. There’s a third choice too. There’s a lot of international wrangling over this because what if we see an Asteroid that’s coming in. We know its orbit well enough and it’s going to hit in say Kansas. We use our Gravity Tug and the Gravity Tug gets it pulled out of the way and then fails.

Then we recalculate the orbit and we find out it’s going to hit in Munich. Oops! [Laughter] so, what do we do? There are literally international lawyers who are hashing this out right now to figure out what to do in these cases and how to figure this stuff out. It’s a very complex situation.

Pamela: Wow and it’s a situation we’re going to have to deal with in our lifetime.

Dr. Plait: Yeah.

Pamela: Well, that was a cheery thought [Laughter] and unfortunately there’s actually some rather even shorter term ways that not necessarily Planet death will occur but Planet inconvenience could occur from the Skies. Those problems tend to come from our Sun rather than some Asteroids.

Our Sun is currently at a particularly long period of minimum. We’ve all been eagerly awaiting a new round of Sunspots with baited breath. This new round of Sunspots just could bring some fairly interesting things Earthward. Can you tell us a little bit about what we might expect from our Sun?

Dr. Plait: The Sun is magnetic. It has a magnetic field a little bit like the Earth’s in that you have a magnetic field generated somewhere on the interior and it pierces through the surface. If you were standing on the Sun and you had a compass you could use that to navigate although not very well because unlike the Earth’s magnetic field which basically pops out at the North and South Pole, the Sun has a very complex twisted magnetic field. Like almost like a huge ball of rubber bands. It’s just a complete mess. It’s a very complicated situation.

The Sun’s magnetic field changes in strength. It goes from a minimum like it is now where the magnetic field is very weak and then over time – over the next 5 and a half years – it builds up to a maximum and it’s very tangled. There are loops of magnetic field energy popping out all over the surface. Then 5 and a half years later it dies down and goes to a minimum again. Right now, like you said, we’re at one of those minima.

What this means is that there are very few Sunspots where the magnetic field pierces the Sun’s surface. It actually lets that part of the Sun cool a little bit and it doesn’t glow as brightly and so we see that as a dark spot. The Sunspots are sort of an indicator of what the Sun’s magnetic field is doing. If you went out with a telescope and pointed at the Sun, projected the image of the Sun on a piece of paper (because you DON’T want to be looking at the Sun through a telescope folks) [Laughter] you won’t see that many Sunspots. There have been very few in the past few months.

We are just now starting to see Sunspots from the new cycle. Nobody really knows what this means. It’s been awhile. It’s been an unusually long minimum and nobody knows what that means. Does that mean it’s going to be a weak maximum? Does that mean it’s going to be a really strong maximum? Nobody knows.

In 2003 we had just a rip-roaring maximum from the Sun. The magnetic field was a total mess and there were Sunspots all over the place. The way you want to think about this is to imagine having a net full of bedsprings. You pull these bedsprings until they’re all full of tension and then wrap them all around each other. They are then full of all this Potential Energy just waiting to snap. Then you poke it and when you poke it and one of them snaps and then it hits another one and that one snaps. They all start snapping all over the place. That releases a lot of energy.

Well, the same thing happens with the Sun. The magnetic field was all tangled up – it’s a bunch of springs – and if something happens on the Sun, one of them snaps or there’s some sort of disturbance, it can let loose all these magnetic field lines. They release all of their energy at once. The amount of energy [Laughter] that’s released is ENORMOUS, it’s VAST it’s terrifying!

Pamela: Well and it’s not just energy but these magnetic field lines as they twist and loop out through the surface are filled with plasma and high energy Electrons. The energy is released in the form of both high energy particles as well as in the form of light.

Dr. Plait: That’s right, basically they snap and their energy is blown downward and upward. They shoot particles straight up out of the Sun; they also blast downward and slam into the surface of the Sun. That can generate Gamma Rays which are the very highest form of energy of light. What happens is you get what is called a Solar Flare. It’s just a tremendous flare of energy. It can be several percent of the Sun’s total energy released in just this one little spot.

It’s an explosion that just totally dwarfs the entire nuclear arsenal of the Earth; it’s a tremendous amount of energy. It’s dangerous in two ways one of which is that the Gamma Rays come screaming out of the Sun and those can hit our satellites and they can cause a lot of damage to the satellites.

When they hit the metal of the satellite they basically blast the Electrons off the metal. The Electrons go scattering every which way inside the electronics of the satellite and can fry it.

Pamela: And there’s no warning that this is going to happen because well, light travels at the speed of light so we don’t get a chance to see the burst coming before it lets loose.

Dr. Plait: That’s right so basically the first notice you have of this is when your satellites die and that’s bad. This has happened in the past. We’ve had these Gamma Rays from Flares damaging satellites and shutting them down before.

But then the other problem is that traveling at tremendous speeds is a wave of subatomic particles, Protons, Electrons, Helium Nuclei, what are called Alpha Particles. They come screaming out of the Sun and they can be here in a day or two. Sometimes they’re moving a million miles an hour and sometimes they’re moving three or four million miles an hour. So they come screaming across the Solar System and slam into the Earth.

What this does is they hit our magnetic field and make the magnetic field sort of shake. All the subatomic particles in Space that are trapped in our magnetic field start slithering around like beads on an Abacus I guess you could think of it. The thing is when you do this you generate a huge electric current. That’s the thing to remember.

The details of this are very complicated. The point is a Solar Flare or what is also called a Coronal Mass Ejection which is another type of Solar Event which blasts out huge amounts of subatomic particles, interact with the Earth’s magnetic fields and they generate a HUGE current. They induce a current. Now that induces a current in the Earth’s surface, literally Electrons start to flow in the ground.

Over most of the Earth this isn’t too big of a deal. The problem is in North America – in Canada and the United States – the geography, the geology of the rock is such that you can get these tremendous currents generated there. This can affect our power grid.

In 1989 a tremendous Solar Event actually blew out power grids in the Northeast and in March in Quebec the power went out. Basically our power system was designed way back when to only have a certain amount of electricity flowing on it. In the intervening years we built more cities, more towns, we spread everything out and even though we have not upgraded our system, we’ve let more current flow on it.

If a current is induced by a Solar Event, there’s not as much leeway as there used to be and so in March of 1989 a Solar Event did this to our already maximally loaded grid, dumped a bunch more current into it – like trying to force more water into a pipe that already has as much water as it can bear, the pipe will burst if you do that – so that’s what happened to our grid.

Our grid overloaded, transformers blew out and people in Quebec in March in Canada were without power for 3 days which is BAD.

Pamela: And it’s cold there.

Dr. Plait: Yeah, that’s really bad. That was twenty years ago now and we still haven’t done anything about this. So our grid is even more overloaded and we’re approaching a Solar Maximum. In 2003 we had HUGE Flares coming from the Sun, bigger than anybody had ever measured before since they started measuring them.

If something like that happens again – and we were lucky, none of them was aimed at us, we caught the edges of them – but if one of them is aimed right at us that could blow out the power grid over vast regions of the United States and Canada. If that were to happen again in November or December, or even in the summer when we’re trying to cool our houses and our office buildings that would be a disaster.

Pamela: And it’s a multi-level disaster because you can imagine we get one of these Coronal Mass Ejections that’s pointed straight at the Earth and it’s accompanied by a Flare of Gamma Rays headed toward the Earth, you knock out a few satellites, say cell phone connections. Then you knock out the power grid.

You now have people that have no electricity and no communications. It’s the multi-layered lack of all the things that our modern society has gotten used to having that could just not mass panic not mass death but some death, a lot of inconvenience and severe economic repercussions. That’s the place that we really need to worry.

Dr. Plait: And it’s even worse than that. If you’re an Astronaut in Space, those Gamma Rays can be very serious. They could be strong enough to give you radiation poisoning which would be bad.

Not only that but it affects the Earth’s magnetic field and it means that any airplanes that are flying at the time (for example) if they are using GPS satellites and the GPS satellites go down they could go to compasses but then their compasses and some of their navigational equipment won’t work very well because the Earth’s magnetic field is bouncing around like a super ball.

So, this could be really bad. It’s hard to really know exactly what will happen until it happens. We don’t want to have to go through that to find out. The thing is, like Asteroids, we can minimize this problem by upgrading our grid. We can put in more cables, we can try to insulate them better, there are a lot of things we can do.

The problem is it costs a lot of money. We’re talking billions of dollars to do this. The thing is, at what cost is this? Is it better to insulate things now (and I mean insulate against the disaster) by spending money now or waiting until after it happens losing people and losing billions or even hundreds of billions of dollars of economic growth in business?

Pamela: We never know and so I think this is where upgrading the power grid is definitely something that if anyone ever bothers to ask an Astronomer we probably need to be doing.

Dr. Plait: Right.

Pamela: Let’s see how long it takes the Sun to come out of minimum and maybe we’ll get lucky and have a really boring maximum. Now these aren’t the only ways that the Earth can be destroyed, they’re just the most likely.

Dr. Plait: That’s just chapters one and two.

Pamela: [Laughter] that’s just chapters one and two. So we don’t have time to go into this much depth on all the chapters of your book but what are your favorite ways to contemplate the destruction of the Planet Earth?

Dr. Plait: When I was researching the book, well it was fun. The book is not supposed to scare the pants off of you. I don’t want people lying awake at night panicking. This is more like a rollercoaster ride or a scary movie where after it’s over you, ‘phew’ you feel better, you don’t have to worry about these things so much.

I’ll throw this out there even the most statistically likely event like getting killed by an Asteroid, your chance of being killed by an Asteroid is one in 700,000. Really all of these things as scary as they are, are very low likelihood events. And some of them like the death of the Sun or when we collide with the Andromeda Galaxy and all kinds of disasters can happen then, they will happen but not for billions of years.

The death of the Sun was one of my favorites to write about and to research because even though I knew a little bit about it, I didn’t know the precise timing. I was able to find a timeline of what’s going to happen to the Sun when it swells up into a red giant.

The current thinking right now is that – you know everybody always says the Earth is going to get consumed by the Sun. The Sun will expand out and go past the Earth and we’ll die that way. But in fact, as the Sun starts to expand, the Solar Wind this constant stream of particles coming from the Sun, is going to increase as well. That means that the mass of the Sun is going to get lower, it’s losing mass. If it’s losing mass, it’s losing Gravity. If it’s losing Gravity, its hold on the Earth isn’t as strong.

So, over the next billion years as the Sun is getting warmer, the Earth will very slowly spiral away from the Sun. It’s hard to say right now and there are people arguing back and forth but right now it looks like we’ll just barely escape the Sun. Mercury and Venus, sorry it’s lights out for them. [Laughter] Um but we may make it.

Of course though having what’s essentially a charcoal briquette at several thousand degrees occupy half of your Sky is bad. The Earth will still be toasted it just won’t be totally vaporized. [Laughter] You can be happy about that or not. But one of the reasons I really like this is because I read a paper that said we can actually save the Earth by moving Asteroids around. If you swing an Asteroid past the Earth, the Asteroid gets moved by the Earth. The Earth’s gravity will move the Asteroid. But the Asteroid’s gravity will move the Earth as well.

It’s a variation of the Asteroid Gravity Tug. You can drop Asteroids past the Earth and actually move it out from the Sun. It takes a long time. It might take you know hundreds of thousands or even millions of years but the Sun doesn’t get hot that quickly so you have that much time.

Every few thousand years you can swing an Asteroid past the Earth and it would pull the Earth out. We could actually prolong the life of the Earth a long time by doing this. I thought that is AWESOME. That is such a cool idea. I was really thrilled with that.

Pamela: And that helps prolong the life of the Earth in a lot of different ways. One of the things that we’re looking at is as the Sun gets older it’s going to get hotter and it’s going to do bad things to the planet Earth. This is because as the world gets hotter the oceans begin to evaporate which causes the Planet to get hotter which causes the oceans to evaporate more which causes the Planet to get hotter – it’s this horrible cycle.

If you can find a way to move the Earth further and further from the Sun, it’s a way of compensating for the fact that the Sun is getting hotter. It’s always neat to consider turning your Planet into a spaceship and that’s basically what we’re talking about.

Now there are still other ways that you can destroy the planet. Were there any others that just stuck in your mind as just ooh cool?

Dr. Plait: Well my very favorite far and away is Gamma Ray Bursts. I’ve been studying Gamma Ray Bursts for a few years so that was probably one of the most difficult to research. We still don’t know that much about these events, their total energies and how it all works.

Basically in a nutshell you have a Super Massive Star a hundred times the mass of the Sun. The core of that Star runs out of fuel and collapses. It will probably form a Black Hole and this creates a huge Blast Wave which blows the outer layers of the Star off. So you’ve got like octillion tons of gas expanding outward at some fraction of the speed of light. It generates a HUGE amount of energy and that’s a Super Nova, an exploding Star.

But in the core of this thing, the Black Hole is formed from the very innermost part of the Star. There are just all kinds of things going on there. There’s friction and gravitational energy and magnetic energy and there’s just what I like to call a ‘witches brew’ of Forces.

All kinds of things happen but the end result is that you can focus two beams of energy that come out of the top and the bottom of this thing basically, in two different directions like a lighthouse.

But instead of swinging around, they just go straight out from the Black Hole. They might last a few seconds up to a minute or two. That’s how long this event lasts. But the amount of energy in these beams is beyond human comprehension.

Pamela: [Laughter] It’s a wonderful… there’s more light in that few ten to maybe a couple hundred seconds than the Sun gives off in many lifetimes.

Dr. Plait: Yeah, it’s basically all the lifetime energy of the Sun compressed into a few seconds and I like to tell people this, if it’s a sunny day go hold your hand up to the Sun and feel the energy hitting your hand. Now think about the surface of the Earth compared to your hand and how much energy is hitting the Earth. Now remember that the Earth is only one two-billionth of the sphere surrounding the Earth at the Earth’s distance.

In other words, the sunlight hitting the Earth is only one two-billionth of the amount of light the Sun is putting out. The Sun has been doing this for 5 billion years; it will continue to do this for another 5 billion years. Now compress all of that into 10 seconds, alright. That’s a Gamma Ray Burst. The energy is out of control.

We see these things happening billions of light years away and yet some of them are putting out so much energy that if you were looking at the right spot at the right time you would SEE them! You could stand out in your front yard and ask yourself look at that Star, what was that? That was a Gamma Ray Burst 8 billion light years away. It’s just unbelievable.

Pamela: There’s a chance that we’ll have front row seats to one of these – although it’s not going to be pointed directly at us.

Dr. Plait: That’s right, if you actually calculate how close a Gamma Ray has to be to do physical damage to the Earth – and that sort of damage is usually destroying our Ozone layer, creating a radiation shower or a particle shower in our Atmosphere that can kill you through the radiation. It turns out that they have to be roughly seven or eight thousand light years away. Anything farther away than that doesn’t really hurt us.

It turns out there are two Stars that close. One of them is Eta Carinae or Eta Car as some people call it. You’ve seen this picture; it’s a famous Hubble picture. It looks kinda like a dumbbell. This is a Star that nobody is really sure, has something like a hundred times the mass of the Sun. The thing is when it blows up it may be a Gamma Ray Burst. It may not be but it might be.

But we know it’s aimed the wrong way. We can see the geometry of the system and that beam is going to miss us by quite a bit, by thousands of light years. So even if Eta Car blows up, we’re safe from it. It’s going to be a very bright light in the Sky and probably it’s not going to be a big deal.

But there’s another one called WR104 – it’s got this catalog name – that’s at about the same distance. From what we can tell it’s kinda sorta aimed at us. We don’t know exactly. We don’t know if it’s going to be a Gamma Ray Burst. We don’t know when it’s going to blow up. We don’t know if it’s aimed at us.

All of these things together make me think ah, I’m not too concerned about it. But you know it’s interesting. If it blew up it’s just close enough to do minimal damage to our Ozone layer. If this happened at a time when the Ozone hole was already kinda hurting, this could exacerbate the problem.

It’s not going to kill anybody but you could get a slightly worse suntan. That’s kinda funny to think that an object that’s trillions and trillions of miles away, quadrillions of miles away really, could actually physically hurt you. That’s amazing to me.

Pamela: So we definitely live in a Universe that’s trying to kill us and we’re out of time. So, if people want to learn more, what should they do?

Dr. Plait: Well, they can go to my website, www.badastronomy.com . I’ve written quite a bit about this. Of course, they can buy the book “Death from the Skies” …..

I do want to leave you with one thought. While researching this book I came up with everything I could think of to wipe out life on Earth and I have a pretty vivid imagination. I was coming up with some crazy stuff. [Laughter]

And then I would research and find out yeah, you know this could work. But, I’m not running around in panic. I’m not screaming in circles yelling “the Sky is falling”. The thing is the odds of these things happening are really, really low.

The point of this book is to look at the really cool things that are going on in the Universe. Black Holes and Galaxies are colliding and all of that kind of stuff happening. Have a little fun with it; yeah, you might get a LITTLE scared from this stuff, but you don’t have to worry.

There are a lot more important things in life to be concerned about. We should be at least looking at Asteroid impacts. We should be looking at the active Sun, but everything else you won’t have to worry about too much. It’s just kind of fun to read about them and think about what might happen.

Pamela: Your book is a fun read and it’s been a great pleasure talking to you Phil.

Ep. 104: Science Fiction at Dragon*Con with Plait and Grazier

Who's Who:

Real people:

• Phil Plait
• Phil's Bad Astronomy Blog
• Kevin Grazier
• More on Kevin from the Cassini mission site

Real people discussed

• Larry Niven
• Arthur C. Clarke
• Richard Hatch
• Michael Bay
• Katee Sackhoff
• BAUT Forum

Show Roll:

• Zula Patrol
• About Zula Patrol
• Battlestar Galactica (official site)
• Battlestar Galactica (SciFi Channel)
• Star Trek (official site)
• Virtuality
• Eureka (SciFi Channel)
• Eureka (Wikipedia)
• Firefly
• Dr. Who (BBC site)
• Dr. Who (SciFi Channel)
• Space 1999 – and the Eagle spacecraft
  
• Babylon 5 (SciFi Channel)
• Babylon 5 (Wikipedia)
• Armageddon (movie)
• Phil Plait's review of Armageddon
• War of the Worlds (original radio broadcast)
• War of the Worlds (original 1953 )movie
• War of the Worlds (2005 movie)
• 2001 (Wikipedia)
  
• 2010 (Wikipedia)

Characters discussed

• Dr. Pulaksi
• Dr. Who
• new Dr. Who
• Donna Noble
• Victor Bergman
• Sheriff Jack Carter
• Spock
• Mr. Data
• Captain Janeway
• Boltar

Real Science Discussed:

• Pulsars
• Star Clusters
• Expansion of the sun
• mass loss rates of the sun
• Mt. Vesuvius
• Dyson Sphere
• Coronal Mass Ejections
• nucleic acids
• Iapetus
• Jupiter turning into a sun? (not going to happen)

Download the transcript

Transcript: Science Fiction at Dragon*Con with Plait and Grazier

Episode 80: Craters (16.3MB)
Types of meteorites:

• Iron
• Stony
• Stony-Iron
• Chondrites — these rocky meteorites do actually hit the ground frequently, as about 80-90% of meteorites found on Earth are chondrites.  The chances of reaching the ground intact are lower for a chondritic asteroid than an iron-nickel of a small size, but a sufficiently large enough chondrite will easily reach the surface of Earth intact.  And as for bodies without atmospheres, there's no difference.
• Arizona State University site on meteorites

Parts of a crater:

• Rim
• Floor
• Wall
• Ejecta
• Rays
• Central Uplifts

All About Craters

• All about craters – Hawaii Space Grant Consortium
• Pamela's Star Stryder post about the crater sessions at the Lunar and Planetary Conference
• Lunar Impact Craters Geology and Structure — Lunar and Planetary Institute
• Craters are not always round –if the angle of impact is ~<5°, then an ellipsoidal crater will form. See examples at the Planetary Blog (Mars), and Enchanted Learning (moon)
• Earth Impact Database website (Search for craters by continent, age, diameter and name)
• Earth Impact Database FAQ's
• Earth's 10 Most Impressive Impact Craters — Universe Today
• Recent impact crater in Peru — Peruvian Meteorite May Rewrite Impact Theories — Universe Today
• Lake Titicaca
• Meteorites from Mars – NASA
• Abstract:  Shock Magnetism and Demagnetism
• Impact Theory for the origin of the Moon — Planetary Science Institute
• Chicxulub Crater
• Asteroid Impact Simulator – Universe Today
• Determining the age of a planetary surface using craters — Malin Space Science Systems
• PowerPoint from Lunar and Planetary Institute about Surface Dating using Craters
• Fluvial Processes on Mars — HiRISE
• Dichotomy of Mars' Hemispheres Possibly Explained by Giant Impact – Universe Today
• Water Ice on the Moon? – NASA
• Water Ice on the Moon? – Universe Today
• Possible Telescopes at Lunar Poles – Universe Today
• Movie of Landing Near a Crater Rim on the Moon — Universe Today

Books:

• Impact Cratering: A Geologic Process by H.J. Melosh
• See a list of more books on impact craters from Amazon

Transcript

Download the Transcript

Astronomy Cast Episode 80:

Craters

Fraser Cain: Welcome to Astronomy Cast our weekly fact-based journey through the

cosmos. Pamela is in Houston, Texas.

Dr. Pamela Gay: Fraser, it's been a sad conference without you here with us.

Fraser: There you go but someone's got to hold the fort down back in Vancouver.

Pamela: Keeping Canada safe.

Fraser: Right, from space. But how's the conference been going?

Pamela: My brain is full. It's been an amazing week of all sorts of content. My

background is astrophysics, it's not geophysics and I have learned more in the

past week than I think I've read reading journal articles in the past several

months. It's just been an amazing experience of well science concentrate.

Fraser: Can you talk the planetary lingo now?

Pamela: No. But I at least know what the people who can speak the lingo are saying

most of the time.

Fraser: So you're able to translate a little better. That's good. Now the results of all your

work is being posted to astronomycast.com/live

We have pictures and audio and text and video, interviews, and all kinds of stuff

so if you haven't already, go to astronomycast.com/live which is where all of

the coverage for this event is.

Pamela: And it's not just me. We had help from Emily Lakdawalla of the Planetary

Society; Rebecca Bemrose-Fetter our producer has been doing a lot of blogging

and photography. We also got a special guest correspondent.

One of my students, Scott Miller, went to see STS-123. He went to see the last

night launch of the shuttle program and we have his Geeks Pilgrimage

documented over on astronomycast.com/live.

Fraser: Awesome. I saw some video of the launch and I really want to see that. Have

to see that launch before it stops launching. Let's get on with the show.

As you know, Pamela is attending the 39th Lunar and Planetary Sciences

Conference in Houston, Texas. That means the moon and planets. When you

think of the moon, you think of craters.

In fact a big theme this week at the planet is craters. Pamela has taken it as an

inspiration so this week is the week we drive the show into the crater. Pamela,

why don't you give us the basic explanation of how we get a crater. Although I

think we can kinda guess.

Pamela: Well you start with a rock, although rocks have more words than I ever knew

existed. You can have a rock that is from the moon or Mars or you can an

asteroid and these can have all sorts of different names.

Most typically the ones that end up hitting planets they were calling chondrites.

You get iron meteors that hit planets. When they impact they can come in at all

sorts of different angles. The angle of impacts affects what direction the ejecta

travels. This is the cloud of material that gets thrown out of the ground and

spewed in different directions.

But you always get a round crater. That's one of the cool things that you can

knock a planet and you can do it from all sorts of crazy angles and the crater is

always going to be a nice happy little perfect circle.

Fraser: Why?

Pamela: It's just the way the physics works.

Fraser: Right, like the rock just gets consumed when it strikes the ground and it's

always in a circle?

Pamela: There are a lot of really complicated processes that go into this. There's

conservation of energy; conservation of momentum. You hit downward and

material gets flung upwards as the energy is being released. It just ends up

leading to this nice happy little perfectly round crater.

You can get craters that end up with multiple rings of material around them. You

end up with craters that have neat layers layered through them with all sorts of

different morphologies depending on where you hit.

In some cases you can actually create an instant lake if you hit someplace on the

planet Earth and the crater happens to break through to the water table. This

actually happened last September. In Peru there is a crater formed about 15

meters across when a fairly good-sized rocky asteroid in this case, which we

didn't think those could actually reach the ground, which is a bit troubling.

But, a rocky asteroid came crashing through our atmosphere. People saw it

while they were hanging out on the roof of a hotel looking up when the asteroid

turned meteor turned meteorite hit the side of a riverbank. It poked through to

the water table and within minutes this crater turned into a little tiny watering

hole.

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Fraser: Wasn't it making people sick?

Pamela: That was actually one of the stories that were in the news. Several different

teams of scientists a few weeks and a few months later went down to study it.

They interviewed the people involved, took pictures, documented everything.

It appears that it was a psychosomatic reaction. There was a lot of fear when

this happened that it was actually a missile from a neighboring country or just

some other country that for whatever reason decided to throw a missile at the

middle of Peru.

This was a fairly remote area near the Bolivia border and somewhat near Lake

Titicaca. There was a lot of fear and paranoia and no it was just a rock.

Fraser: Why don't you walk me through the steps nice and slow like for as a rock

strikes the ground – space to crater.

Pamela: Okay. The most typical case is you have what starts as an iron asteroid. A

happy little friendly object on an orbit around the sun minding its own business,

but its orbit happens to intersect the orbit the Earth. It can intersect it at all

different angles.

You can end up with an asteroid that hits our atmosphere head on where its path

is going straight from space straight down towards the earth. That's kind of

rare. Most of the time you're at some crazy angle.

Just probability says that its' more likely you're going to be somewhere

between zero and 90 degrees than at 90 degrees when you hit the atmosphere.

Depending on the angle that it hits the atmosphere it's going to deal with

differing amounts of slowing down from the atmosphere.

Different frictional effects as it passes through the atmosphere will slow it down,

heat it up, dissipate some of its energy and dissipate some of its mass through

all sorts of different burning up processes. This is what you see when you look

up in the sky and see this really bright streaking object. It is melting,

evaporating, ionizing all these things depending on its composition.

So it's getting smaller and smaller and so you might start off with something

that is several meters in size that ends up the size of a football by the time it hits

the surface of the earth. Then when it hits all that energy is transferred into the

ground.

You can end up with instantaneous melting. You can end up with shocks, but

the basic result is you end up with this great big splash of materials that shoot

straight up.

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Fraser: Does the asteroid always hit? Can't they explode in the air?

Pamela: No. It doesn't. They can explode in the air, or they can vaporize in the air. The

vast majority of stuff in the air that hits our atmosphere is pebble and dust grain

size. Things like that aren't going to make it to the surface of the earth. It's

only the larger objects and how large is required really depends on the angle

that the object impacts on our atmosphere and the difference in velocity

between them.

You can imagine that you have this asteroid that is on an orbit that causes it to

just hit our atmosphere and is going just fast enough that it is mostly gravity

sucking it in. You could also end up with an asteroid that is perhaps going

around the sun in the opposite direction so it could hit the Earth's atmosphere

with the exact same angle.

Because of the difference in its' orbital velocity and our orbital velocity where

we have basically a head-on collision, it's screaming in at tens of kilometers per

second and this huge extra velocity ends up making it a much more dangerous

object.

Fraser: Okay so the rock has transferred its energy to the ground. What happens to the

ground?

Pamela: It depends on how big the object is. There are some really cool models that

have been done at Los Alamos National Lab where they have a super

computing facility. In some of these models, there are simulated scenarios of

large object hits the ocean and the splash of the ocean water is so great that a

column of water goes through our atmosphere.

So we're actually if we get hit by something large enough and hopefully this

would never happen because the tidal waves would be devastating and as would

many other things. If you hit our oceans just right, you can splash ocean water

into orbit basically. That's just really cool.

You can do the same thing if you hit land but it would be much more

devastating. This is actually how we end up getting Mars rock hitting the Earth

as meteors and being found as meteorites all over the planet.

At some point in Mars past it was hit by something big and chunks of Mars was

sent into space on orbits that carried them to Earth where they passed through

our atmosphere, survived and landed somewhere on the planet just waiting for

some geophysicist or some farmer to find it.

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Anyone can find a meteor. They are all over the planet. They are easiest to find

in deserts and in Antarctica. But you could find one in your back yard if you're

lucky.

Fraser: Now either you're on a tangent or you're avoiding my question. I think you're

on a tangent.

Pamela: It's also after midnight where I am and also very late where Fraser is.

Okay, so the rock hits the planet and you can get dirt or water thrown into the

air depending on where it hits. The energy as it propagates through the soil can

take a chunk of the soil and actually flip it over.

You can end up with inverted layers stacked up on top the soil, dirt, or glacier

around wherever the impact occurs.

Fraser: You mean like dinosaurs on top, then newer rock, then finally topsoil?

Pamela: That's exactly what happens, it's a complete flip. If there is enough energy, it

can liquefy as it hits. Soil is made up of silicates, organic materials, because we

have earthworms here on our planet. Organic materials form just about

everywhere but they don't always have earthworms and microbes in them.

An organic material is just something that has carbon atoms and molecules. But

you take this stuff and if it has silicate in it that basically melts to glass, which is

cool and you can melt it and get these fascinating structures around it.

There is also all of the material that is in the meteor that has now turned

meteorite and that can shatter on impact and you end up with ejecta fields that

are filled with quartz crystals. You can end up with all these various blobs of

shiny glass strewn all around where the central crater is located.

You also get the pieces of the meteor if it chooses to shatter, which can be

chunks of metals. So you have this ejecta field around a crater rim that includes

inverted materials.

In some cases depending on what you hit, if you're hitting something that's rich

in metals, you might actually in the process be able to whack them hard enough

or melt them just right that you end up creating magnetic fields within the

materials that you've just knocked really hard

Fraser: All right, I know that if you hit a piece of iron really hard you can give it a

temporary magnetic field, right? Because you are aligning all the little jiggled

up iron atoms so that they're all pointing in essentially the same way and they

get that magnetic field going. So a large enough rock can do that to dirt and to

iron ore in the ground?

6

Pamela: Exactly. This is actually something that we think has happened in some cases

on the moon. If you look at the lunar craters there are some amazing maps of

the moon's magnetic fields from the lunar Prospector.

When you look at these maps, there is a little bit more magnetic field in one

place than another and is coincident with the centers of craters where there is

little upwellings of material which sometimes happens for reasons that we're

still trying to figure out.

It is thought that these magnet fields are either induced through shock, like

hitting it as you would hit a nail with a hammer, which is something anyone can

try. Go get a real metal nail and whack it a few times with a hammer really

hard and you can use it to pick up paper clips.

Either that or perhaps in some really ancient cases there was an intrinsic

magnetic field around and by heating the material, you randomize the atoms in

it if it is material capable of becoming a magnet.

As those heated up atoms cool they align along any magnetic field that happens

to be around. This is why in different parts of the planet Earth we can actually

figure out the history of the Earth's magnetic field by looking at the way the

magnets are aligned, natural ferromagnetic materials.

With the moon we have these neat little lumps and bumps of magnetic fields

that are coincident with craters. And that's just cool.

Fraser: Right, you get some lava that pours out of the ground or is created in an asteroid

strike and it is liquid enough that all of its atoms can align while it is cooling in

the magnetic field.

Then the magnetic field is cooled and they are locked in place and maintain a

record of the magnetic field that was there at the time.

Pamela: In some cases if you whack something hard enough with an object that is large

enough you can even do things like create the Earth's moon.

Our planet once upon a time was hit by another object and we go into this in our

"How the Moon was Created" episode.

Fraser: That's like a big crater there, mighty big.

Pamela: Actually, it's more like an ejecta. So the splash of material I told you about can

sometimes make it up through the atmosphere, that would be our moon.

Fraser: A really big collision.

7

Pamela: It's a really big collision. But in these really big collisions you don't always get

moons. In fact, it looks like both Mercury and Mars have giant basins. In

Mars' case one that is about half the planet – the whole hemisphere.

Both Mercury and Mars appear to have been clobbered by something of double

digit percentages of their own size at some point in their past. This had huge

morphological affects on the entire planet.

Fraser: Now what good have craters done for us?

Pamela: Well, they probably got rid of the dinosaurs which some would argue allowed

mammals to evolve on the planet Earth and thus reign supreme and destroy the

planet in new and interesting ways.

At the same time, it's a way of distributing material around the solar system and

there also a tool that geophysicists can uses to measure the ages of other objects.

For instance on the moon you can look around and there are lava fields on the

moon. The moon actually had a much more liquid core in its past and lava was

able to escape through various different types of dyke features.

There are also all sorts of very neat little underground effects of lava going

underground where we could see it and creating neat geographical formations.

We can date different features on the moon such as the highlands, the mare

based on how many craters there are in different areas. We could also measure

the depth of lava using the craters.

The way this works is you look at an area and count how many craters there are

in different areas and we can also measure the depth of lava using craters. The

way this works is you look at an area and count how many craters of different

sizes there are within that area.

You can make a plot of number of craters versus size of craters and you'll end

up with a bazillion little tiny craters and very, very few giant craters and you

can fit a pretty much straight line to those relationships.

Now in an area that has a ton of craters, where you end up with the entire line

shifted so that it intersects the Y-axis is really high number. That is a really old

surface, one that has been around for along time getting whacked with rocks

from space.

Fraser: So you just count the number and the size of craters in some region and then you

consult some geophysicists chart somewhere and it tells you how old that region

is. I guess you might have regions that are right at almost the beginning of the

solar system while other places might just be a few million years old.

8

Pamela: They actually define different geological periods based on the crater number.

This gives us the relative age. Trying to get at the actual age of a planet, a

moon, whatever requires you to actually go out, grab a rock and do radioisotope

counting. Look at what different elements have had a chance to decay in that

particular rock.

We can't do that with Mars yet. But we sent Apollo astronauts to the moon and

they landed in different places. By taking those rocks and looking at the

radioisotopes in them and what has decayed and what is left, we're able to say

this part of the moon has this age; this part another age; and use that to scale our

understanding, at least with the moon, this crater rate corresponds to this date in

the past. That's kinda cool.

With Mars, we're not at a point yet where we can do the radioisotope work and

say we know exactly how old this part of the surface is. Although we have

some fair guesses based on our understanding and on the Rovers we have sent

there so far.

However, with Mars we do the same thing. We age different surfaces and also

age things like stream beds, filuvial systems cut out by liquid we think and they

look like deltas and we're able to say this section is older or younger than this

other section based on how craters are layered on top of or not layered on top of

based on these filuvial systems.

Fraser: Now we look in the sky and we see the moon just wracked by craters and yet

here on Earth, I think there are meteor crater for well-known crater? Why isn't

the Earth as hammered as the moon?

Pamela: It rains. We are hammered just as much as the moon. The difference is that as

you look at the surface of the Earth you're not seeing any rocks that are 3.5

billion years old unless it's a rock you happen to find and pick up and test and

just happened to survive.

There are a few places on the Earth where we find old rocks but it's not the

whole surface of the planet. When we look at Mars; when we look at the moon,

we're looking at surfaces that have rocks on their surfaces that are billions of

years old and they haven't been eroded by rain or dust and the plate tectonics on

both the moon & Mars are much less.

Mars has the Tharsis Bulge, it has Olympus Mons, it has all these volcanoes that

are problematic. They raised a whole chunk of the surface. To understand

those parts of the surface we have to do all sorts of crazy other stuff. In general

the surface of both of these worlds haven't been rained on.

Already with the crater that recently formed just last September in Peru, 15-

meter diameter crater is almost gone. It rains, and the rain washes soil in,

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flattens things back out. Anyone who has ever dug a hole in their back yard

knows the hole is going to fill itself back in rather quickly.

Our planet erodes. It kinda sucks.

Fraser: So you just wonder how many enormous craters are just gone.

Pamela: There is actually thought that things like the Yucatan are crater edges. As we

look more and more at satellite images we're finding more and more giant

craters from their rims all over the planet.

Fraser: That's right, there's like the latest satellite missions are able to measure the

contours of the Earth such precision that they are able to find these enormous

craters just by the tiny little difference in the height of the rim.

It's been eroding for a hundred million years but there is still just enough of the

rim remaining that they would know there was a crater there, that there was a

huge collision there. Only just now they are able to discover these craters.

Pamela: The other way that we're finding it is using gravity measurements. This is one

of the coolest things. I learned about this a few years ago. I thought this was

really cool and I don't geek out too much about gravity.

There is the ability to measure gravity with some instruments so precisely that

you can tell the difference in gravitational acceleration between someone's foot

and their head using this instrumentation.

It's possible to go around with gravity detectors and if you know your distance

from the center of the planet, which you can get from GPS systems, and you

measure the acceleration of gravity at that altitude from the center of the planet,

you can roughly figure out the amount of material that has to be between you

and the center to cause that acceleration. Doing this, they go out and find things

like petroleum reserves.

But working in South America, a group of geophysicists actually found a big

impact basin this way because the densities versus shape of the terrain just

didn't make sense for any other process. Gravity allowed them to find a hidden

crater.

Fraser: They're using that technique to measure ice loss from glaciers to see how the

ground such as in Canada is bouncing back after the last Ice Age. They can

measure how the ground is moving back up after the Ice Age. It's pretty

amazing.

Pamela: It was actually using these gravity measurements that we've recently been able

to figure out that the reason that you get this weird dichotomy between the

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northern and southern hemispheres of Mars is because Mars got whacked by a

really big object. We didn't know about what had happened for a long time

because of the volcanic system that spews volcanic material all over the

boundary between the highlands and the lowlands. We had to figure out how

does that boundary move beneath the lava flows.

A group of geophysicists combined topographical maps that show the altitude

of the terrain with gravity maps that were extremely precise. They were able to

determine that if we assume that the crust of Mars has this density and the lava

flows have this density, what do the boundaries between these have to look like

in order to get the gravity we observe and the altitude of the land that we

observe.

When they did this, they could basically peel off all the volcanoes and see what

the crust looked like beneath them. They were able to find that the boundary

between the highlands and the lowlands is basically a perfect ellipse around

Mars. You pretty much can only get that shape if you whack Mars and you

make an impact basin.

There are ways that you can work really hard with other models and twist

parameters and other things and jump through lots of hoops and ignore

Ockham's razor and get this to happen other ways. But the easiest way to

explain those results is to say that Mars got whacked with something over 2,000

kilometers in diameter and didn't end up producing a moon in the process but

instead created this dichotomy between the highlands and lowlands.

Fraser: Wow, so a couple more things. One was just to talk a bit about how the gravity

and structure of what gets hit changes the nature of the crater itself.

Pamela: It's not just the gravity, it's also the surface that's getting hit. So if you impact

on top of a bunch of ices and say you dig up the soil beneath the ices and spread

them out on the top of the ice.

Then you can get these really neat plateau craters where over time the ice

around the crater in this ejecta blanket might vaporize or sublimate away and as

this ice goes straight to gas where the soil has been dug up and plopped down

onto the ice it can't do that. You end up with that layer of ice basically

protected by the ejecta that's on top of it and everything else around it gets

lower and lower and vaporizes into the atmosphere.

You also have depending on the gravity the amount of stuff that gets flown up is

going to differ. If you hit a really big heavy object with a rock, the gravity of

that object is going to hold on to the material and make it not fly out quite so

much.

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But if you hit something much smaller you launch rocks from Mars to Earth.

So the height of the crater walls is going to be a function of the density of the

material you're hitting and the gravity of whatever it is that you're hitting. It all

plays together.

Fraser: I know we mentioned when we were doing our tour through the solar system

some of the bizarre crater formations in some of Saturn's moons.

Pamela: The death star.

Fraser: Yeah, where it almost looks like it's hitting a real spongy material and the

material is just collapsing. I think there's one last really good use for craters

that we haven't talked about which is when the astronauts return back to the

moon one of the things that they will be looking at is the craters at the southern

pole of the moon which are in some cases eternally in sunlight and in other

cases eternally in shadow and may even hold water ice.

Pamela: One of the things that is amazing that I just learned this week is the difference in

altitude between the base and the rim of some of these craters is like four

kilometers. That's about two miles.

We talk about Denver, the mile high city. Imagine standing on the edge of

something twice the altitude or more of Denver looking down. There is an

amazing movie they showed us of a little tiny sad little lander craft coming in

and just perching on the very edge of one of these craters.

Fraser: Nancy, one of the writers did a story about that on Universe Today. We've got

the video on the site. It's kind of scary.

Pamela: The reason that we're looking to do this is when you land at the equator of the

moon, in daylight you're several hundred degrees. When in darkness, you're at

minus a couple hundred degrees. Pick Fahrenheit or Celsius it really doesn't

matter it's really huge swings in temperature either way you go.

Once you get down into one of the craters in constant darkness the temperatures

stay constant. One of the things about electronics is they don't really like to

have their temperature messed with. We can engineer things that work at a

couple hundred degrees and we can engineer things that work at a negative

couple hundred degrees. It's hard to engineer things that can survive huge

temperature swings.

If we go to one of the poles of the moon you can stick your habitats down in the

shaded part and just keep people warm and stick your solar panels straight up

and they will be in constant daylight. So you have constant power and thermal

regulation. It's just a lot easier to function that way.

12

Fraser: You could have the sunlight just a few tens of meters away from your habitat

and still be safe.

Pamela: One of the ways they phrased it was you can be down in a constant darkness

area and just raise your hand and the simple act of raising your hand that is

above your head, your hand will be in perpetual sunlight.

Fraser: I can't wait until that exploration starts happening.

Pamela: Just a few more years.

Fraser: Just a few more years. The missions are going to be launching just within the

next year and it seems like it will start steamrolling from there.

Pamela: We have LCROSS and LRO are launching on the same rocket in I think

October of this year. LCROSS is this really cool mission that they're going to

basically plow objects into the surface of the moon making artificial craters,

making our own space craft into meteorites and see what dust gets chewed up

into the air. It's going to be neat work.

Fraser: All right, well I think we'll be covering that as we go for a much, much future

show.

Pamela: It was a great experience and next year you need to come with us Fraser.

Fraser: Will do.

Episode 70: How to Win a Nobel Prize (13.9MB)

Pre-print Servers

• lanl.arXiv.org – Open access to 457,583 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology and Statistics
• The SAO/NASA Astrophysics Data System – Digital Library for Physics and Astronomy

Peer-Reviewed Journals

• The Astronomical Journal
• The Astrophysical Journal
• The Astrophysical Journal Letters
• The Astrophysical Journal Supplement Series
• Publications of the Astronomical Society of the Pacific
• Monthly Notices of the Royal Astronomical Society

Shiny Magazines

• Nature Magazine
• Science Magazine

 

 
Download the transcript
 

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Transcript:

Fraser: Just a couple of shows ago we showed you how to get a career in Astronomy. Now you have your career as a research astronomer. Obviously, the next goal is win a Nobel Prize. We’re here at the American Astronomical Society Meeting in Austin, which is just one tiny step a person has to take to win that Nobel Prize.

Pamela: And there are a few Nobel Prize winners floating around this meeting.

Fraser: So it’s not impossible.
 
Before you get that phone call in the middle of the night from Sweden you will need to come up with an idea, do some experiments, write a paper, get published, and a bunch of other stuff. I’m probably over-simplifying it Pamela.

Pamela: Oh, way over-simplifying it.

Fraser: Obviously not everyone is going to win a Nobel Prize, but why don’t we start somewhere and talk about how people can go from zero to getting their research done.

Pamela: Well, in general you have to start with an idea. You have to start with a question, a “what if� and work on trying to solve that “what if.� Nobel Prizes have gone to people who said, “what if you look at the Universe in the radio; what if you explore what is coming through galaxies by simply tuning your telescope to look at radio light instead of looking at optical light?�
 
There are all sorts of different people who have simply said “well what if� and then there’s the hard part; it’s easy to come up with the “what if�.
 
You then spend years following that “what if� with careful theoretical work with careful building of instrumentation, with carefully looking at your noise to see what is it in the noise that no one else has ever discovered.
 
The cosmic microwave background came from a group of scientists working to study the microwave emission of our galaxy and instead coming up with the microwave emission of the universe.

Fraser: I read that one of the ways that some of the greatest research happens is that it starts out with someone looking and going, “huh, that’s funny.�

Pamela: And most of us go huh that’s funny and we blame our instruments and move on. The truly great people won’t let things go. They just keep delving in and exploring deeper until they’re able to say, “well I’ve ruled out everything. This is something new. This is something exciting.� Then they followed up with figuring out what it is, and it’s a collaborative process with different people shaking ideas out on other people who can then go, “no that’s crazy but what if�…and you follow all the “what ifs� until you find the truth.

Fraser: Okay. Let’s start at the beginning then. Let’s say you have an idea or you look at your data and think, “huh, that’s funny.� What’s the next step?

Pamela: Math.

Fraser: Okay.

Pamela: The first step is you go through and do a statistical analysis. You see if you can repeat it. You have to be able to repeat something. If it happened only once never to be repeated again, it probably wasn’t real.

Fraser: Right, I guess what I’m saying is how will you get access to telescopes? How will you get access to the equipment you need to even follow your crazy ideas?

Pamela: Let’s say you’re not trying to figure out what the noise in your data is but rather you come up with this idea of “I think foo is true about galaxies� and you want to figure out how to prove to the rest of the entire scientific community that is true. Well the first step is you do a literature search and make sure no one else has ever studied foo.

Fraser: So where would you do a literature search?

Pamela: There are two places to go. There is the NASA ADS website which is pretty much a collection of all the published journals. Some of them unfortunately, you have to pay huge subscription fees to get access to the most recent articles. But there is hope.
 
There is another site XXX.lanl.gov It’s ArchiveX, it sounds like a porn site but it’s run out of Lawrence Livermore National Labs and it’s where pretty much everyone goes to dump a copy of their latest research. Often people dump a copy before it has even gone through peer review to get feedback from the community – what questions do people have and what ways can you make your paper better before you take it to publication?

Fraser: Right. These all have search engines you can put in key words, you can put in search of the text. It’s all available, you can read their research and make sure that whatever your idea is, nobody else has, or you find what everyone else thinks on the subject and you can decide whether your thinking is absolutely brand new or just a variation of what somebody else thought about.
 
I guess when you see what other people thought about it helps you search and refine your thinking and you come up with new ideas.

Pamela: Then you need some sort of an infrastructure to put your idea in. “I think Galaxies might have foo becauseâ€?… And then you go through and demonstrate what is the evidence that this could be out there waiting to be found. What are the breadcrumbs that are leading you to discover this new foo about galaxies?
 
Once you’ve put these breadcrumbs together and found the path through the woods, then you write telescope proposals. You write grant proposals. You try to get the time and the money that will allow you to study this effect. This is it’s own peer-review process.
 
You send out a proposal for telescope time and you’ll either get telescope time or you’ll get feedback that says, “well we didn’t give you time because we are concerned about the following things. Follow up on this. Tell us more; convince us better�.

Fraser: You have to sell to the telescope managers that your idea is worth exploring.

Pamela: It’s actually a committee of hopefully your peers or the people you hope to be peers with in the future. It’s a select group of scientists who sit down and it’s not always the same group of people every time. They go through all the proposals and sometimes hundreds of proposals looking for forest nights of telescope time to be available to them.
 
These people go through and use their wisdom and ability to use the scientific method to examine your argument. Think of them as the jury in a court case and you are the lawyer making your opening statement. You have to sell your idea and only once you’ve convinced them that your idea is worth pursuing do you get the ability to pursue it.

Fraser: But as you’ve said, there are other avenues you can go to. There are networks of amateurs and there are other ways. You make the same pitch to multiple missions to multiple telescopes.

Pamela: One of the best ways to do it is first you go to some easily accessed ground-based telescope and get some preliminary observations. With the preliminary observations you say either we have a hint of this being possible or we can’t eliminate this as being possible because the observations aren’t good enough using this telescope so clearly we need a bigger and better telescope.

 
They want you to first use the cheap, easily available resources before you can get the Hubble Space Telescope time – the very large telescope time. It’s a matter of did you do your homework or not. It’s big resources and there are not a lot of resources out there to share.

Fraser: So you have written your proposal, your peers have come back and said this sounds like it’s worth pursuing so they’ll schedule you time on the equipment?

Pamela: You get time on the equipment; they then often just ship the data to you. A lot of the telescopes now are what they call Q-based. You say, “these are the conditions that need to be met for my observations to be taken,� and a night assistant automatically gets your data and ships it to you either over the internet or perhaps on a DVD.

Fraser: So you don’t have to go to the telescope?

Pamela: No, not at all.

Fraser: You don’t have to head out to space to look through the Hubble?

Pamela: No, definitely not that one.

Fraser: But in many cases, the proposal is approved and you’re in. At the time that they promised your data will come to you and you can start crunching it.

Pamela: It’s all beautiful magic. Once you get your telescope data that is just the start. It can take months to get your data reduced to a point where you have numbers you believe are actually true.
 
You get your data, you reduce it, you play with it, try this, try that and a couple of months down the line you have something where you can make graphs and plots.
 
From your graphs and plots you have to try to figure out what does my graph and my plot mean? In some cases you can get completely new science just by graphing two variables no one every thought to graph before.

Fraser: But in many cases you have an idea of what you should be expecting with your galaxy theory and you are now looking through the data and checking to see if your theory matches reality.

Pamela: Yes.

Fraser: And as you are saying, there could very well be any number of interesting things that poke up in the data that are completely separate from what you’re working on and that probably must just work into brand new proposals to look for more information.

Pamela: Every new question you answer ends up creating ten, fifteen, twenty, a thousand more questions, more ideas, more things you just need another ten nights of telescope time to explore.

Fraser: But even if you get a no result, that’s still useful because that just means that your theory is wrong and that’s okay.

Pamela: Or sometimes you just simply haven’t come up with a better way to do something.
 
One of the more frustrating aspects of my doctoral dissertation is that I successfully proved that that if you look at one radio source you have roughly 23% probability of finding a cluster of galaxies around that. We already knew that. But if you look at a grouping of six radio sources, you have a 27% a whole 4% better chance of finding a galaxy cluster. It wasn’t really easy.

Fraser: Intriguing.

Pamela: It wasn’t really useful though because it takes a lot of time to find the clustering and prove that it is real. It was a very sad result, but is was a true result and it was worth sharing to prevent anyone else from following this bad avenue of exploration.

Fraser: All right, so let’s say that you got your data, you’ve crunched your numbers and you believe you now have a result.

Pamela: Then you publish. Often the first step is coming to a meeting like this one, the American Astronomical Society meeting and putting a poster presentation together.
 
This is where you have a 48-inch x 48-inch sheet of paper to convince everyone of the vague outline of your idea. Show your graphs. Give captions. Give a few hundred, maybe a thousand words of text in big enough letters that someone slinking past with their coffee trying not to attract any attention will be able to read as they slink past.

Fraser: I can’t overstate that it really looks like a kid’s science fair with posters around. It really seems like you would expect it was a lot fancier but it is like a big piece of paper with a bunch of pretty pictures on it and some graphs and a person standing beside it trying to get people to come take a look at it.

Pamela: It’s just amazing the diversity of people. My very first time I presented was at AAS in San Antonio, TX and the person hanging the poster next to me was Erica Bonvetnse (?) who had written the textbook I was using that semester and was another variable star astronomer and many, many other things. She’s just awesome.
 
I totally fan-girled over this woman older than my grandmother – that’s probably not true. But I made her sign her book and then she just stood there dutifully next to her poster just like I, the little meek undergrad did.
 
So you see everyone from high schools students in some rare cases to the most senior faculty standing quietly next to their poster waiting for someone to come by and actually care.

Fraser: So you have to do your time with your poster.

Pamela: Yes.

Fraser: All right. That’s only one part of the conference. The other parts are the meetings.

Pamela: There are meetings and oral presentations, but posters are the primary way to convey information. There are also 5-minute oral presentations.

Fraser: Posters are the primary. It blows me away that standing beside a poster is the way that you communicate your research and your ideas to other astronomers.

Pamela: Well what’s great about is if your options are give a 5 minute oral presentation or present a poster, with your 5 minute oral presentation you have no time to say anything – that’s 3 overhead slides; 3 powerpoint slides.
 
At your poster, you can stand there and you can have a dialogue with your peers. You can find out who has data on this source that is sitting in a drawer unprocessed because they took it for some project they decided not to do. You can interact, you can get great ideas.
 
That is what’s important about doing these poster and oral presentations is dialoguing with other people. Finding out what don’t you know that is hidden in somebody else’s head or drawer or some journal article that you just missed because it is easy to miss one or two. There are thousands and thousands out there.
 
You go through this process of dialogue. Science is a collaborative effort. Very few people work in any sort of isolation and we generally refer to the people who work in isolation as cranks because science is dialogue. Each person’s idea is growing on everyone else’s ideas.
 
Once you’ve gone through these presentations, then you’re ready to sit down and spew out your five to ten page journal article that you then submit to a journal for final publication.

Fraser: So once you’ve gotten all the feedback from your poster presentation, you’ve sat in a bunch of meetings, you’ve had a chance to collaborate with some of your peers, you then go back to your quiet office space and write up your findings.

Pamela: Yes. You write up your findings.

Fraser: Now that you have a journal article what do you do with it?

Pamela: You hope that somebody reads it. This is where if you write a really good paper and it catches someone’s attention, if you have a really remarkable finding you might actually write a press release for it or go to your University Press Officer and get them to write a press release for it. If you’re lucky, people will read your paper and most papers really get read like ten times.

Fraser: Where will they read your paper?

Pamela: In the journals that come out.

Fraser: So your paper isn’t guaranteed to go in a journal.

Pamela: No, you take your paper and submit it. The step that we all painfully try and forget is when you get your referee’s report back.
 
So, you submit your paper to the journal. The journal then finds someone who’s not one of your direct collaborators and is quite often your direct competitor, sends your paper to them and asks them should we publish this? They will generally say, “yes, but make all of the following corrections.� Often you have to go through three rounds before you actually you get the yes.
 
The first round will be: this is worth publication but needs serious revision. You then revise. It then comes back and says: much better and if you’re really lucky that’s when they say yes fix these four sentences that you wrote stupidly.
 
Occasionally you have to go to a third before they finally say yes, this is worth publishing. Often referees are extremely useful since they are coming at it from outside of the problem they are able to say, I think I know where you’re going with this idea but I shouldn’t have to guess. Flesh this out so that anyone reading this knows what you’re thinking.
 
Sometimes they write just the most amazingly vague things like expand on paragraph six. And I think, what about paragraph six do I need to expand upon? You’re just wondering, how dumb can this person be?

Fraser: Of course, any of the people who would have worked on any of Pamela’s papers in the past they were wonderful.

Pamela: Right and the grant process is the exact same way. So you get back these referee reports, make all the changes, eventually get your paper accepted and then it often comes out several months later.

Fraser: And that’s the peer review process, right? You’re submitting your paper to your peers – in many cases your enemies – and they’re trying everything they can do to find a hole in what you’ve thought of. Trying to make sure the words you’re using are as clear as possible before the journal is willing to publish it.
 
So you run that gauntlet, you do the final edit; no one else can nitpick any other problem with your journal article; it gets published into a journal. What are the journals?

Pamela: The primary ones in astronomy are the Astronomy Journal, the Astrophysical Journal, the publications of the Astronomical Society of the Pacific, the monthly notices of the Royal Astronomical Society, Nature and Science and Astronomy and Astrophysics. Nature and Science are big only because they have the biggest press engines.
 
A lot of really great science comes out in the Astrophysical Journal that is totally worth being in Nature and Science but the authors just don’t feel like jumping through that hoop. Nature and Science are hard to work with.

Fraser: They want to make it all pretty slick with pictures.

Pamela: With the Astrophysical Journal, you know it’s going through peer review, it’s going out to your peers which doesn’t necessarily happen with Nature and Science. You get your journal article in Astrophysical Journal or one of the other journals and now you hope somebody reads it.
 
If you’re lucky and people read your work, that’s when you start getting invited to give university talks. You are invited to give talks at conferences like this one and at other conferences out there and your idea starts to build and is shared and starts to become a foundation of what we do.

Fraser: So what will happen is future researchers will be referencing your work in their work. Citations, is that right?

Pamela: Citations are sort of the thing that we all want the most. It’s one thing to publish ten journal articles a year, but if no one ever cites them or no one ever reads them, what good are they?
 
Given the choice of inviting a speaker who’s written three papers that each have a thousand references and that happens very, very rarely, but it occasionally happens, or someone who’s written a hundred papers that have never been cited by anyone other than the author, go with the person with a thousand citations. They clearly did something that somebody (and in this case a lot of somebodies), care about and need to know.

Fraser: Right and so it’s almost like the citations are the votes from other researchers that the work that you’ve been doing is of value and is a high contribution to the field.

Pamela: It’s just like how many links does the Podcast website have; how many links does the blog have pointing at it.

Fraser: It’s almost like the same model that Google works on that the more links to a website the more popular Google has decided that website is so the more likely it is to show up in future searches.

Pamela: The way it actually ends up happening in some cases is someone finds a cool effect and that cool effect ends up taking on the names of the authors. So you have the Butcher-Oemler effect in galaxy evolution. You have the Geller Hook diagram. These are all people and those are the names on the journal article that brought forward this new idea that now bears that idea’s name.

Fraser: You get to have your name just run along with it for the rest of the time that it gets used.

Pamela: Forever.

Fraser: That’s the way to go.

Pamela: Yes. So now anyone who is out there doing large-scale structuring Geller Hook…is still there. For a long time galaxy formation was the Agen Linden Bell model. I hope I got those names correct otherwise I’m going to be laughed at later. But Searles Zin model – there’s all these different it’s just the names of the people on the article and that’s what you remember and those names go on to sum up all the ideas in those journal articles, those key papers to our fields.

Fraser: If you want to be a working astronomer, how often should you be publishing?

Pamela: It depends on what you do. There are people out there who are amazingly prolific and put out one paper a month or more in some cases. All because you’re chewing out a whole lot of papers doesn’t mean you’re doing excellent science.

Fraser: No, but in some cases I guess – like Mike Brown at CalTech who is the person who found the tenth planet. I guess he’s got the right technique, the right team…

Pamela: And he’s just chewing out discoveries.

Fraser: Exactly. Oh, new planet, new large Kuiper Belt object and just keeps them coming out. In those cases I think you don’t really no need to slow down or stop. But if you’re going to come up with something really deep in foundation you might as well take your time and get the citation.

Pamela: It depends on what field you’re in. If you’re a theorist, you might spend a year or two carefully delving through the mathematics and get one publication out of it and you worked very hard the entire time.
 
In other cases you might be someone who is studying things that it takes two years worth of observations and then all of the analysis that goes in the observations.

Fraser: Think of the people on the Gravity Probe B mission where it will take two years or three years for that to finally gather all of the data to be able to decide and in the end it will be just one sentence like: Yes, Einstein was right again.

Pamela: The number of publications that makes sense for you is really going to depend on what type of science you’re doing. There are people like Michael Brown who just chew out papers at a phenomenal rate and then there are other people that two papers a year and they are highly respected scientists. You just have to put all the different pieces together.

Fraser: That’s kind of good for the regular folk but now the people who really want to win the Nobel Prize, are there any other further steps you can take or is it you’ve already done your bit?

Pamela: You’ve either got it or you don’t.

Fraser: So you either thought of something foundational that’s going to change everything or keep working.

Pamela: One of the key aspects that I’ve seen in all the Nobel Prize winners that I’ve interacted with is these are the people that when you walk through the University halls at 8 p.m. are at their desk. When you walk through the hallways at 6 a.m., they’re at their desk.
 
They go home for 6 hours maybe and they’re constantly dedicated, they run a tight ship in terms of keeping their grad students on track and keeping their undergrads on track. Everyone works hard, dots all their I’s, crosses all their T’s, pays attention and is thorough.

Fraser: There is a level of almost organization and hard work and focus and dedication that goes above and beyond the regular researching that happens.

Pamela: These are the type of people that in a few cases after they get the Nobel Prize, they decide to go and play in another field and within a matter of months they’ll be at the top of that field too. There’s just a level of both genius and dedication that qualifies someone to be capable of getting a Nobel Prize.

Fraser: In many cases I know the Nobel Prizes aren’t awarded until in some cases ten or twenty years. It’s almost like you have to wait until the research is totally incontrovertible, that everyone assumes it is completely true and they use it repeatedly.

Pamela: It becomes part of the canon.

Fraser: It’s not like you’re going think this year we came up with a wonderful discovery and later this year we’re going to get a call from Sweden. It’s this year we’ll come up with a wonderful discovery and then over the next ten years it’s proven and re-proven and everyone really thinks it is right.
 
Ten years after that if things have really settled down then you’ll get your call. You can almost, from what I’ve heard from people who’ve got it, you can start to feel that you’re in that zone; you’re starting to have a chance to win one of the prizes. I thought this could be easy, but I guess it’s not.

Pamela: No, it’s not.

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