Questions Show: Moons and the Drake Equation, Stars in the Void, and Rings Around Stars

Europa, a moon with liquid water. Image credit: NASA/JPL

Europa, a moon with liquid water. Image credit: NASA/JPL

This week we find out if moons around other planets could support life, if there’s anything out there between galaxies, and whether stars form rings.
If you’ve got a question for the Astronomy Cast team, please email it in to and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

  • Moons and the Drake Equation, Stars in the Void, and Rings Around Stars
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    Could there be other moons in the Universe, could they habitable, and how would that affect the Drake Equation?

    Are there lone stars – and planets – in the voids in space?

    Are there stars with rings?

    Is dust a big problem for spacecraft?

    How do we determine the mass of celestial objects?

    Are all planets in the ecliptic?

    How are complicated astronomical computer simulations run?

    Is There Dark Antimatter?

    If you were in a spaceship traveling at the speed of light and you shone a flashlight on the wall, would you see any light on the wall?

    Transcript:Moons and the Drake Equation, Stars in the Void, and Rings Around Stars

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    Fraser Cane: Welcome to the AstronomyCast question show where we answer your questions about space and astronomy. We’re going to record these questions as quickly as possible Pamela so you can get out into the nice weather.

    Dr. Pamela Gay: Sounds good.

    Fraser: This week we find out if moons around other planets could support life, if there is anything out there between galaxies and whether stars can form rings like planets.

    If you have a question for the AstronomyCast team please e-mail it in to and we’ll tackle it for a future show. Please include your location and a way to pronounce your name and please include your name.

    Let’s get on with the first question. This comes from Clinton Edwards in Perth, Western Australia. “We have numerous moons in our solar system and surely it can be assumed that there are numerous moons in other solar systems. Does that affect the Drake’s Equation?”

    I guess what Clinton is saying here is we’ve found planets here; we’re finding planets around other stars. We can assume we’ve got moons here there are probably going to be moons out there. I think that’s a fairly safe assumption. What impact does this have on the Drake Equation? The Drake Equation of course is that (we did a show on this) and that’s the calculation of how many habitable worlds there are out there.

    I guess what Clinton is wondering is if those moons could support life does that totally change the equation with the Drake Equation numbers because instead of just having a couple of planets you have a whole pile of moons as well that might be supporting life. How do you feel about the: are there moons in other solar systems?

    Pamela: Totally. There is absolutely no reason to think there aren’t and every way that we look at it we’re sort of planning that they are there.

    Fraser: Right, haven’t found any yet but we can kind of assume that they’re out there.

    Pamela: They’re kind of small kind of hard to see.

    Fraser: Could moons be habitable?

    Pamela: Yes and in fact we kind of are hoping that in our own solar system we might be able to find life someday on the moon Europa or perhaps Titan or one of the other moons that has active geology in our own solar system.

    Fraser: I guess if the moon is big enough and can hold on to its water and it is in the right part of the solar system, then that water can be liquid. If you’ve got liquid water and you’ve got an energy source from the sun and you’ve got the chemicals that you need you could have a shot at having life.

    Pamela: For all we know it is possible that perhaps liquid methane in other liquids other than water that life might be possible as well. So, there’s absolutely no reason to think that there isn’t life on moons.

    In fact, in trying to figure out the Drake equation for the future we need to start figuring out what numbers of planets do we expect, what is the distribution of sizes of those planets that we expect with the distribution of sizes of the moons we expect. What is the distribution of orbits we expect?

    Only after we start finding out what these distributions are can we actually do a legitimate calculation of the Drake Equation. At this point we just don’t have enough observational evidence to be able to get a handle on any of those numbers. It’s still guessing and turning the crank.

    Fraser: It essentially makes either the equation a lot more complicated if you add a whole pile of variables that you just mentioned or you just multiply planets by the number of moons that you’re going to be finding as well. You increase that number. I guess in the end it gives you a lot more shots at life.

    Pamela: That’s kind of cool.

    Fraser: It’s very cool. It’s interesting that this is something that when Drake first did the equation I’m sure the thought of there being life on moons was impossible because we look at all our moons and just see balls of rock.

    Now we see that they’re a lot more complicated and a lot more possibly life-sustaining. You look at Enceladus, you look at Europa, and these are not your grandfather’s cold dead asteroid moons. These are places with liquid water perhaps.

    Pamela: Now that we’re finding Jupiter and way larger than Jupiter-size planets near stars the possibility of a habitable moon with an Earth-like climate near a star is completely feasible. George Lucas’ Endor could exist somewhere out in the galaxy.

    Fraser: No Ewoks please. [Laughter] Okay so the next question comes from Brandon Stuart “Is it possible that there are planets or dim stars between galaxies or is it just empty space?”

    I guess what he is wondering is once you get outside the reaches of the Milky Way are there just open spaces where there is absolutely nothing? Or could there be lone stars, balls of rock, etc.?

    Pamela: Yes, and in fact it doesn’t even have to be dim stars. There are a lot of things that we know have been torn out of galaxies. Bright stars that probably in some cases have planets, through galaxy mergers, through galaxy collisions, you end up with stars strewn out about the space between galaxies.

    Fraser: But that’s an ejected star, right?

    Pamela: Yeah.

    Fraser: Which I think is sort of a little bit of a special creature. Are there naturally occurring stars out there?

    Pamela: That could get a little bit more complicated. This is where we have to start trying to draw the line between what’s a cluster of stars and what’s a baby galaxy.

    There’s not an easy way to form one star all by its lonesome out in the middle of nowhere between galaxies. Galaxies tend to form in clusters. They tend to, well they in fact always form out of giant molecular clouds.

    If we do have star formation occurring between the galaxies with giant molecular clouds collapsing down, at what point do we say that we’ve now formed a dwarf galaxy and we’ve now formed an isolated star cluster? It starts to get very hard to make these distinctions.

    We do know that there are giant molecular clouds, giant clouds of neutral gas in general in the spaces between galaxies. It’s out there; we see it in what’s called the Lyman Alfa Forest.

    Some of this will eventually collapse down into forming stars. Individual stars all by their lonesome those we can’t really get there unless we eject them we strip them we knock them out of existing galaxies.

    Fraser: I guess in the same way that we have clusters of stars in the Milky Way where they’re forming in their big cloud and then they’re being broken up and spread around over time you’d probably get something kind of similar. They would form and they would eventually drift away from each other.

    Then a few billion years down the road if you were standing on one of those stars you might not even be able to see the other stars that were originally part of your cluster. I guess you don’t have the motions of the Milky Way which kind of jiggles things up, right?

    Pamela: Yes, there is absolutely nothing to break that group of stars apart. This is where we can look at the systems of stars that are orbiting our own Milky Way galaxy and say, well there’s things like the little tiny Ursa Minor dwarf spheroidal galaxy which isn’t that different from a globular cluster except in structure of the stars.

    This is a single cloud of gas and dust that in isolation underwent probably one single burst of star formation and formed an itty bitty little tiny itsy bitsy galaxy that gravitationally fell into our Milky Way. All those stars are still together.

    If we do have these isolated pockets of gas and dust forming isolated pockets of stars, they’re probably going to look like these dwarf galaxies and gravitationally stay bound together.

    Fraser: That’s pretty cool. This is a question of serious scientific inquiry and the search is on for these clouds of cold gas with the question being are they forming something? Where are stars? Are they just in galaxies? That’s a great question. It’s a very serious question that scientists are asking too.

    Let’s move on to the next question. This one comes from Joseph: “Do stars ever get rings similar to Saturn?” Well Pamela, are there stars out there with beautiful majestic rings like Saturn?

    Pamela: You might call our own asteroid belt a ring of sorts although it kind of a varied not dense.

    Fraser: What are Saturn’s rings made of?

    Pamela: It is very small mostly chunks of ice covered in dust. The rings of Saturn in some cases are made up of material that is blasted out of moons like Enceladus which has water geysers. In other cases, we’re not entirely sure where the source material came from.

    Perhaps some of it is crunched up comet. Perhaps some of it is failed moons. In general though the material is quite small, the belt itself is only a few meters thick to a few kilometers thick depending on where you’re looking.

    Fraser: So could a ring like you’ve got around Saturn and you put it around a star, what would happen?

    Pamela: We’d call it a protoplanetary disk or a dust ring. We do see this, particularly in images from the Spitzer Space Telescope.

    Fraser: Wouldn’t it just be like a comet? Wouldn’t it just be blasted away?

    Pamela: The material itself if you put it far enough from the sun won’t get blasted away. Our own Quiper belt is made of similar material it’s just not that dense. Before the star has a chance to blow all of its stuff away pretty much the whole disk of the solar system is a lot like but much, much, much thicker scaled up to stellar proportions very similar to the rings of Saturn.

    In fact, as we look at some young stars we see a dust disk around them that has gaps in the disk similar to the gaps that we see in Saturn’s rings. We speculate that those gaps in the disk are actually the places where planets are forming just like the gaps in Saturn’s disk are the places that the moons are located.

    Fraser: You see the artist’ impressions associated with stories about the discovery of new protoplanetary disks. We don’t have really good photographs but there are beautiful artist’ impressions and they kind of look like a ring, a set of rings around the star.

    But in this case they don’t last long, right? They’re in the process of forming something else while Saturn’s rings have been going on for potentially billions of years.

    Pamela: This again depends on whose theories you read. We’re pretty sure that Saturn’s rings are transitory but there are astronomers who have models that have them lasting for a long period of time.

    We’re pretty sure that in general the disks around planets are transitory but then it could be that in some situations they last a long time. We just don’t have enough thousands of year’s worth of data to really get a handle on the lifetimes of these stars. We’re still learning how to detect them around other stars.

    As we get more and more data from the Spitzer Space Telescope we’ll be able to say hey this star has been around a long time and it still has a disk around it. That will give us a sense of how long these things can last.

    Fraser: But if I took the sun and sort of put it in the sort of the same proportion to the rings around Saturn, with the sun being 1.4 million kilometers across and Saturn only being 80,000 kilometers across, if you have the proportions right and you took a nice ice crystal ring that looked exactly the same around the sun that wouldn’t last would it?

    Pamela: I don’t know. I haven’t done that calculation. The question is does the point where the rings start lie outside the ice barrier, the freeze-frost line which is currently in our own solar system’s asteroid belt? You can imagine as long as the gap was basically the size between the surface of the sun and out in the asteroid belt beyond that you could have rings like Saturn’s rings in our own solar system.

    Fraser: It’s like if you had enough material…

    Pamela: And that’s the key.

    Fraser: You would have rings. As soon as you get within that frost line then unlike Saturn, the sun is a blazing ball of energy; it would turn them into comets. So anything inside that frost line would be like a comet would be whisked away and anything outside of that would be maintained as a ring.

    You’d have a beautiful set of rings if you had planets and planets and planets worth of water ice. [Laughter] That would be amazing to see. I wonder if there is such a star up there that just lucked out in the water department.

    Pamela: We just need to keep looking.

    Fraser: Gotta keep looking. Next question comes from Martin Halloran from Sydney, Australia: “You often mention that the main sequence of stars, but I don’t think you ever define what the main sequence is.”

    Alright Pamela, define the main sequence of a star.

    Pamela: The main sequence stars are stars that are undergoing the first phase in nuclear energy generation in the core of the star. For stars roughly the size of the sun and a little bit bigger and as small down as you want to go this initial phase is burning hydrogen in the core.

    As you get to sufficiently larger stars this first phase includes burning carbon-nitrogen-oxygen in the core as well. During this first phase, they’re nice, they’re stable, they keep burning happily for the longest period they will ever burn anything.

    Once they end that first phase of energy generation and go on to something involving heavier elements and then they burn a little less and in fact a lot less. So we say main sequence because that’s the longest period of life for the star.

    Fraser: So when would a star like the sun, say a star is born, how long until it enters the main sequence?

    Pamela: I think it is a few million years. Then they stay in the main sequence for about 10 billion years.

    Fraser: Ten billion years, right and then they have all the red giant stuff at the end but that’s why it is the main sequence because it’s the bulk of its life.

    Pamela: Right.

    Fraser: Okay, there you go. There’s your definition. Next question comes from Josh: “Do spacecraft need to worry about dust? I’d imagine one of the difficulties of near light speed travel is that a grain of dust would be devastating at those speeds. Even a GPS satellite I’d imagine smacking dust can’t be good for it.”

    Let’s move away from near light speed travel because I would imagine that smacking into a particle moving at nearly the speed of light would be bad.

    Pamela: Yeah, we actually call these things cosmic rays. Generally it’s like a lone proton.

    Fraser: One proton.

    Pamela: They can like blow out pixels on digital detectors.

    Fraser: Or give you cancer.

    Pamela: They can flip charges inside of computer systems. These things actually make it all the way through the Earth’s atmosphere and randomly destroy things on the planet Earth as well.

    You don’t have to worry about them generally destroying the outsides of spacecraft and things like that because they’re so small that they pretty much just move between the atoms.

    Unless they hit something just right like flipping a unit of memory, sort of like we saw if you watched Battlestar Galactica this was in one of the most recent episodes.

    Fraser: Don’t spoil anything for anybody.

    Pamela: It was actually a webisode too. But, that’s all you need to know. Where you have to start worrying about actually causing failure of the spacecraft because its hull has gotten destroyed or something like that is where you start worrying about things that are bigger than the largest snowflakes but not a lot bigger than the biggest snowflakes.

    Once you start getting into these many molecule things, once you start getting some weight behind you is when you have to start worrying. We call these micro-meteorites. This is where you can get things as big as peas, big as pieces of gravel.

    Fraser: These are meteors, right? You look up in the sky and you see a blaze of light clear across from horizon to horizon. That is a pea size object burning up through the atmosphere. Imagine the energies involved.

    Pamela: The space shuttles, the space station all periodically get whonked with these things. They do periodically cause damage but so far nothing has been destroyed this way.

    Fraser: So far, [Laughter] and no people, right?

    Pamela: We do build our spacecraft, our spacesuits all with enough protection to withstand normal types of collisions.

    Fraser: You get to a certain size and if the spacecraft can’t handle it, you’re toast. Ouch, right? A pea-sized chunk of rock just went right through me.

    Pamela: There have been even cases here on the surface of the planet Earth where a random human has been hit by object falling out of the sky. That’s just not good.

    Fraser: Right but you’ve had the atmosphere to slow your object down a bit.

    Pamela: And the roof of the building you’re in.

    Fraser: Yeah, out in space you just like when a bullet going through the spacecraft and then you lose pressure and all that.

    Pamela: So again, not good.

    Fraser: Next question. This comes from Marco Leone: “My question has to do with how we determine the mass of a celestial object. We talk about the mass of the sun and the mass of the Earth and the mass of those stars and that black hole. How do astronomers determine the mass of an object in space?”

    Pamela: In general we look at the way objects move around each other. We need to be able to first see how long it takes to go all the way around, but we also need to be able to get a measure of the size of the system.

    Here one of the best things to use is binary stars to use orbits in general. With binary stars in particular you can estimate the distance to them. You can then measure the physical size of the orbit.

    If you know the distance to something and you know how far left to right, up and down in the plane of the sky the orbit is, you can then say aha this orbit has a given radius.

    We have orbital mechanics equations that given the size of the orbit and the amount of time that it takes to go all the way around the orbit we can make calculations of what the gravity involved in this system has to be.

    Fraser: I think I learned this in grade eleven.

    Pamela: Probably.

    Fraser: I’ve got these equations in like grade twelve.

    Pamela: Yeah you can do this using Kepler’s equations and Newton’s laws. It is mathematically it is straightforward algebra.

    The trick is finding objects that are politely aligned well enough that we can make these estimates.

    Fraser: What if you don’t have something orbiting?

    Pamela: If you don’t have anything orbiting then all you can do is resort to theory. For instance we know that certain size stars, certain mass stars give off certain colors of light. To get a star of a given temperature on the main sequence which we just talked about, you have to be burning a certain fuel in your core to get the right combination of pressures and densities in the core of the star to be giving off that particular color of light that corresponds to that particular temperature.

    You have to have a certain amount of mass, so you resort to lots of scary equations that tell us a lot about stellar atmospheres and tell us what color the star should be. There’s a lot more air. Binary stars are a much more straightforward way to approach this problem.

    Fraser: Right, to use an analogy here you’re looking through your telescope and you see a cat half a kilometer away and you say how much does that cat weigh? You go like well it’s a cat so it probably [Laughter] weighs a few kilograms in this range. You can’t really know.

    Pamela: Exactly so we can say within a certain range a star of a given temperature weighs foo.

    Fraser: Right but I think that the difference between that and when you’ve got the orbiting is dramatic. Take Pluto for example, I know that before astronomers had discovered Pluto’s companion moon Charon they had no real idea of what the mass of Pluto was.

    Pamela: No, we made vague guesses at what is its density. We know what its diameter is, let’s guess its weight.

    Fraser: Then you find Charon and you go okay now we can calculate it to within many decimal places of air. It is a dramatic difference. If you have the orbit, if two objects are orbiting one another it’s a very straightforward and very accurate calculation. If you don’t then all you can do is kind of guess as the best you can.

    Pamela: For planets like Venus and Mercury which don’t have any moons the only way that we’re able to get accurate measurements of their masses is to stick spacecraft or satellites in orbit around them. Without doing that it’s basically you’re making a guess at the density and we make a guess at the mass.

    Fraser: That’s amazing, so until they had actually put a spacecraft in orbit around Venus or Mercury they didn’t really know their mass to a high degree of accuracy.

    Pamela: Exactly.

    Fraser: Wow. The next question comes from Don Coquist who asks: “Pamela has mentioned that all of the planets orbit along the ecliptic of the solar system. Is it possible to have planets orbit outside the ecliptic? Has anyone actually looked outside the ecliptic to verify that there are no planets there?” Pamela, you said it so it must be true.

    Pamela: I did.

    Fraser: Are all of the planets in the solar system in the ecliptic?

    Pamela: In our solar system within our ability to discover them and define them using the International Astronomical Union, yes all the planets are in the ecliptic.

    Fraser: Right, so if it is a planet, it’s in the ecliptic. I think the point being, when we say the ecliptic this is this flat plane that is imagine like a plate around the sun and all of the planets are following in their orbits. They’re grooves of a record. Of course, kids don’t know what records are these days, right?

    Pamela: Originally our sun had a protoplanetary disk around it that filled the higher space where the planets are now located and the planets formed out of that disk of material. They just didn’t get flung out of it.

    At the same time once you start looking at Pluto, Sedna, and once you start looking at all the random objects that we’re still classifying out in the Quiper belt, these objects which weigh less and or have lower mass and can thus get flung around the solar system. Then it usually through collisions through interactions, they’re not all confined so politely to the ecliptic.

    If there were any Mercury-sized planets, if there were any Earth-sized or Jupiter-sized planets that had orbits that weren’t confined to the ecliptic we would know about them if they were close enough to be observed because even though they don’t stay the whole time in the ecliptic their orbits would cause them to go through the disk to go through the ecliptic at least twice per orbit.

    Fraser: If a planet the size and brightness of Jupiter was the same distance from the sun and just happened to be orbiting across the ecliptic it would still be as bright and shiny in the sky as Jupiter is.

    Pamela: Right and we would have noticed it by now, but we haven’t seen any of these.

    Fraser: To find a planet off the ecliptic it would have to be very, very distant. I think the question is a good one because astronomers are following the theory, right?

    They’re saying well planets are likely to form along the ecliptic so if we’re going to find more planets they’re going to be on the ecliptic. There are lots of unseen territories off the ecliptic while the ecliptic is a very well studied place.

    Pamela: There are teams like Michael Brownlee’s that do look off of the ecliptic, that do look in different directions trying to find other perhaps Pluto-sized perhaps a little bit larger than Pluto-sized objects that are out in the Quiper Belt and the Oort Cloud that are planet-like but not necessarily planets according to the IAU definition. If you want to learn more about that, go listen to our very first episode.

    Fraser: I guess the point is that there could very well be planets orbiting outside the ecliptic. What would make a planet orbit outside the ecliptic?

    Pamela: If it had a bad day or a bad few months and underwent a gravitational interaction with another object or a group of objects that changed its orbital direction. As we look around our solar system we find lots of things that we know have had a hard life.

    You look at Mars and it has huge craters. You look at Uranus and it appears to be turned on its side. These sorts of giant craters and odd alignments most likely come from fairly significant collisions.

    You can almost imagine what would happen if you had a Jupiter and a Saturn-sized object orbiting one another and something more the size of one of the rocky planets like Mars or Earth was co-orbiting with them. In this sort of a 3-body interaction it is possible to radically fling one of the objects out of the 3-body system perhaps flinging it into a really strange orbit.

    Fraser: So you could get an object, even a planet-sized object orbiting completely outside the ecliptic if it entered in a very bizarre 3-body interaction with other planets and was kicked out.

    Pamela: Yeah, a lot of violence would need to occur for this to happen but it’s not impossible.

    Fraser: There you go. This question comes from Matthew Kapp “How do people run simulations of events that have millions of objects and how is it possible they can complete the simulation in a few hours? How do they do the thousands of lines of coding?”

    Some of the simulations I guess that Matthew is thinking of are like supernova, galactic interactions and colliding galaxies and the formation of solar systems. How do they run these kinds of simulations with so many objects?

    Pamela: The coding part is easy. A lot of us know how to program. In fact a lot of astronomers know how to program really well. As you look across the field of astronomy when you start getting to know your local theorist, getting to know how they do their job, it turns out these are people that have all the skills of a systems administrator. They have all of the skills of the best industrial programmers but their forte isn’t writing operating systems.

    Their forte is designing solar system simulations, designing supernova simulations. They just get paid a tenth of what they might earn if they were in industry. There are a lot of astronomers who are professional level computer programmers within their specialty. The programming is easy. What is harder is getting your code to run.

    There are various super-computing facilities around the United States where you apply for time on the super-computer and then it runs your code. Sometimes these codes actually take days at a time to compile.

    Other places have what are called Beowulf Clusters which are where you cluster together a bunch of different processors often using the Linux operating system and distribute your process across all these different processors. There’s a variety of different ways and sometimes you just suck it up and you run it on your desktop as powerful as you can purchase computer and it runs for a few weeks and you hate yourself.

    There is a lot of patience involved in astronomy. You’ll spend a couple years in your life perfecting your code and then spend a couple months of your life waiting for it to fully process, having it crash a couple of times on you just so you can get that one publishable result.

    Fraser: There was a presentation at the American Astronomical Society meeting that we just attended. I was watching it and someone had done simulations to see in sort of newly forming planetary systems where Jupiters and Saturns and smaller planets might form and what would be the conditions to get something like what we have.

    After I’d talked to him I asked: “How did you do your simulations?” He had these beautiful animations. He had about a hundred simulations done that he could sort of show all at the same time. He said I use a Beowulf Cluster and it took many hours for each simulation.

    In a Beowulf Cluster we’re talking some of the most powerful super-computers on Earth are matched by some of the Beowulf Clusters. How do you run the simulation with millions of objects?

    You find the most powerful computers on Earth and convince the people who operate them to let you use them for hundreds of hours.

    Pamela: Sometimes you build your own. We have a professor in my own department at Southern Illinois University Edwardsville who has his own personal Beowulf Cluster for the research he’s doing on biophysics.

    There are lots of ways to get there. You have to learn how to program. You have to learn how to string computers together or to get time off of other people’s computers. And patience.

    Fraser: It would be nice to have a Beowulf Cluster here in the house. [Laughter] I think that would be very nice. I’m sure it will play my video games very fast.

    Let’s move on to the next question. Peter Gilmore asks: “Can you get dark anti-matter and if they collided would they destroy each other in the same way?”

    So Peter is going if there’s anti-matter – you’ve got matter and you’ve got anti-matter – if they meet they annihilate one another and generate a tremendous amount of energy.

    Pamela: Yes.

    Fraser: So if you took dark matter and anti-dark matter and put them together, would they destroy in the same way?

    Pamela: Yes. If we’re right that dark matter is perhaps – this is just one of the theories out there – is perhaps just super symmetric particles then there should be anti-matter colleagues to all of these different particles.

    Whatever it is that dark matter is made up of there’s probably – physics says it is at least – there should be anti-matter versions of all of the particles.

    Fraser: Right and if that creature exists then perhaps in a particle accelerator as you’re generating these showers of particles and if you’re getting dark matter and anti-dark matter particles colliding with each other I guess you would see a certain kind of energy signature, right?

    Pamela: Yes we’re just not there yet.

    Fraser: Right but this is exactly the kind of thinking that a theorist would do that a particle physicist would do and say if dark matter is what I think it is then there should be anti-dark matter particles and they should be like this.

    If I see them interacting, I should see this output. So, crash my particles please and let’s see if I see what I’m looking for. [Laughter]

    Pamela: We just can’t generate the energies necessary yet, we’re working on it to get to the lightest of the super symmetric particles. It is hoped that the Large Hadron Collider will get us there.

    Fraser: Right. That’s cool. This comes from Brock Hansen: “If you can travel at the speed of light or close to it and you were in a spaceship and you shine a flashlight on the wall of the spaceship would you see any light on the wall? Would the light have to move faster than the speed of light?”

    Oh, this is classic relativity here. [Laughter] Okay so you can’t travel the speed of light.

    Pamela: Right.

    Fraser: Let’s remove that part of it, okay? Brock we’re only going to let you go close to the speed of light. Let’s say that Brock is in a spaceship and going 99.999999 percent the speed of light.

    His spaceship is possibly the mass of the entire Universe [Laughter] shines a flashlight at the wall, what speed does the light go from the flashlight to the wall?

    Pamela: The speed of light.

    Fraser: The speed of light.

    Pamela: What’s cool is in order to perceive the speed of light the same for our fast moving astronaut and for a lonely individual on the planet Earth, time has to slow down for that really fast moving astronaut.

    His time has almost come to a stop. Because his time is passing so slowly he perceives light as moving the same speed and the second he turns on that flashlight to the eye, instantaneously light appears on the wall.

    It would appear exactly the same way it would appear here on the surface of the planet Earth.

    Fraser: Right and that’s relativity and that’s how it has to work. That’s crazy.

    Pamela: That’s the beauty of the speed of light. It’s always the speed of light and it is time that changes to accommodate it.

    Fraser: Yes so even in these crazy scenarios you’re going to get the light will always be appearing to move at the speed of light. We’ve done two shows on relativity. We’ve done a whole question show on relativity, so we’ve had many other question shows that included questions on relativity, so we’ve got lots of ways for people to be able to wrap their heads around relativity if they want to get more into it.

    I know we’ve been collecting another batch of relativity questions so we’re going to do another relativity question show. Stay tuned. Pamela, I think that wraps up our time for this week we’ll talk to you for the next show.

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