Ep. 126 From Skeptics Guide with Questions

Transcript: From Skeptics Guide with Questions

Bob Novello: Hello Pamela thank you for having me on AstronomyCast.

Pamela: Thank you for coming in on such short notice. We had hoped that Fraser would be back and he’s not dying, he’s not really sick, he just has no voice and it is hard to do an audio show with someone with no voice. So thank you Bob.

Bob: My pleasure, I’m a Podcast junkie and this show is absolutely one of my favorites.

Pamela: We’ve really enjoyed having the opportunity to be on your show with you and your brothers and Rebecca and everyone else so many times.

This week Bob is going to pepper me with questions, testing my ability to leap from tidal forces to gravitational waves to well, the Higgs boson. We’ll see where this takes us on this skeptical journey through what is known and what we’re trying to learn about this Universe.

So, I guess Bob this is where I say ask away! Let’s see what happens.

Bob: like electromagnetic radiation do they follow the inverse square law?

Pamela: Let’s step back and say a little bit about what gravity waves are. When anything with mass moves through space, its gravitational pull distorts the space and time around it. Our planet Earth, it’s not that big, it doesn’t create that big of distortion, we’re never going to be able to measure the distortions, in fact from anything within our solar system.

When you get two extremely high mass objects like binary neutron stars or binary black holes they warp the space around them so much that it’s like two balls running around each other in a lake leaving wakes and creating waves as they swing around. We’re able to see in the decay of their orbits the radiation is getting radiated away in these gravitational waves. In some cases we think if it is really gigantic events like the mergers of black holes for instance occur they’ll send waves that are big enough propagating through space that we’ll be able to maybe be able to detect them here at the planet Earth.

The problem is these waves as they expand away from their origin the total energy contained in the waves stays constant. More or less, they do lose energy as they interact with different things and affect them.

Just like the wave from the pebble radiating through water, the wave might start with a large amplitude. But as the wave covers a larger and larger radius of the surface of the lake, the amplitude of the wave, the height that it is above the average layer of the surface of the lake gets smaller and smaller until at a large distance from where that pebble went in you can’t even see where the wave is.

So, yeah gravitational waves do have this problem with as they spread out they end up having the energy in one given section of the wave get lower and lower with the one over r squared law.

Bob: I would imagine then that the waves near their origin could be quite substantial then.

Pamela: Yes and in fact if you were near a merging black hole the distortions could pretty much snap you apart as they went across your body and stretched you to and fro.

We have nothing nearby generating that sort of a gravitational wave so we’re pretty safe.

Bob: I wonder what the kill zone would be for something like a merger of two black holes or neutron stars. I wonder how far the really nasty affects would be. Would it be a light year or just a million miles?

Pamela: This is actually something I haven’t looked the number up on. There is a kill zone around these things where interesting effects like spagetification but not as bad as falling into a black hole just stretching you a lot in one dimension does kill you. It’s not that big of a kill zone. It’s order of light years.

Bob: it would also be affected by the expansion of the Universe and they would be Doppler shifted?

Pamela: We don’t really think about them so much as getting Doppler shifted. With the Doppler shift what we’re worrying about is you have a whole bunch of waves and the separation between peaks, the separation between one wave peak in a wavelength and the next wave peak in the wavelength changes and you see a change in color as an affect in normal light. You see light getting shifted from the blue to the red as the Universe expands and spreads that entire wave out.

With gravitational waves the amplitude isn’t quite as well spaced and the separation between peaks, yes that separation is getting spread out due to the expansion of the Universe. Depending on the physics of what’s going on you could have this single isolated wave?

We see the rogue waves in the ocean. You can end up with gravitational waves through the Universe with this single rogue wave of space time distortion passing through space. When you have just a single wave it’s kind of hard to talk about Doppler shifting.

Bob: Okay, very interesting. The Large Hadron Collider that was probably for me it was one of the biggest science news items of last year. It’s such an incredible effort that all these scientists throughout the world were going through.

Then of course they turned it on last year everything looked good and then soon after that there was a problem. They had some helium leakage I believe? They were delayed.

Initially they were saying that they were going to open this spring but now just very, very recently they’re saying that they probably won’t be able to open until September and maybe no collisions until October. Do you know why there is that delay?

Pamela: With the poor Large Hadron Collider, they had a helium leak. This giant donut of an accelerator essentially consists of a tube that runs in a big circle and then a parallel tube that runs in another big circle that are kept at complete vacuum. This means all the particles that we can are sucked out of these two many kilometer long tubes.

In order for everything to work the vacuum has to be maintained and everything has to be completely clean inside of these tubes. Then they put the particles in, use magnetic fields to accelerate the particles and if there wasn’t a vacuum then these accelerating particles that are racing around, racing around inside these giant tubes would end up colliding with particles that are just hanging out being atmospheric before they hit the detectors.

Unfortunately there was a flaw that caused a large helium leak into one of the collider’s tunnels. This means they couldn’t keep everything as cold as they wanted. This meant that they ended up soot in places that they didn’t want it. It’s a really complex problem. They have to clean up the mess and fix and repair the segments. Initially they thought they could be done repairing everything by spring but as they got into it they realized that they had a couple of different options.

They could replace a series of segments of the tunnel and get everything up and working again but perhaps since this might actually be a problem with the pressure system it would be good to redesign, step back and redesign the system and make sure this problem never occurs again.

They’re proceeding cautiously. They’re trying to make sure they do everything right. This is the most expensive science experiment that’s ever been done. It has the potential to make some of the most interesting discoveries of our lifetime in terms of allowing us to understand the fundamental particles that build this Universe.

Perhaps even allowing us to not only understand why it is that you and I have mass and light doesn’t but to also maybe discover the lightest weight dark matter particles. We want to do this right.

Bob: That leads into my next question. One of the big hopes for the LHC is that it finds evidence as you alluded to the Higgs boson which is theorized to imbue all particles with mass.

I was thinking where does the Higgs boson itself get mass? Is it interacting with itself?

Pamela: In a way. The way that I think about this is that the Higgs boson exists to couple people to the Higgs field a couple of atoms to couple anything that has mass to this scale or field. This is sort of like I hold onto a bracket on the wall. I attach myself to the wall, I reach out I grab your arm and I couple you to the wall using my hand to hold you and my other hand to hold the wall.

I’m perfectly capable of coupling myself to the wall if I feel like it. So, the Higgs boson is both able to couple other things to the Higgs field via the Higgs mechanism but it is also able to couple itself and imbue itself with mass. Unfortunately it did this with a large enough mass that we need the Large Hadron Collider to work before we can find it.

Bob: Is it okay that I’m having trouble visualizing a particle being stuck to a scale or field? [Laughter] I can’t do it.

Pamela: The pictures that we use in our brain really make no sense. The whole idea that the Universe is permeated with a field that imbues everything with mass is just kind of out there New Age sounding.

The reality of the Universe is sometimes far more strange than what any New Age psychic might decide to make up.

Bob: Just look at quantum mechanics.

Pamela: Exactly and who would ever have wanted to create that to define our Universe? It’s probabilistic and there’s nothing set in stone as “this will happen in this instance”. The actual Universe has fields that it’s the fields that allow things to happen.

Our planet Earth has a gravitational field. The planet doesn’t reach up and grab my keys when I let go of them. It’s the gravitational field of the Earth that curves space and my keys fall down the curvature of space to land on my floor with a loud chunk – I’m not going to drop them right now.

There’s this field permeating everywhere. Not just where the Earth is but everywhere that imbues everything with mass. It is something that doesn’t make any sense to visualize but you know we’re just human beings and we can’t hold the whole Universe in our brain. That’s okay.

Bob: Okay, well let’s wish luck for the LHC and hope that they get everything fixed by this fall or late summer and hopefully we’ll be talking more about the Hicks boson later this year. That would be great.

Pamela: It is something that I’m really looking forward to what they discover.

Bob: Oh yeah. Okay let’s see on to cosmic rays. I remember reading a Scientific American article about in the last year or so about cosmic rays and how they are essentially deal killers for manned interplanetary missions in the near future such that before we could even think of taking a manned trip to Mars we have to solve this problem.

Launching the shielding that is required to protect the astronauts is really not practical because the launch costs would just be so huge that it would be almost undoable. I remember reading years ago about a spacecraft that is capable of potentially generating its own magnetic field kind of like the protective magnetosphere around the Earth.

Wouldn’t this solve that problem and how come I can’t find any new information about it? [Laughter] I guess it must be impractical or maybe there’s a fatal flaw, but I just can’t find anything new about that technology.

Pamela: Yeah, it is actually work that is currently being worked on at Dick tock dick, I can’t say this correctly as an American. It’s a British; it’s Rutherford Appleton Station in a city with a name that sounds crude when my American accent tries to pronounce it over in the UK.

There’s this huge power plant that looks just like a nuclear plant and it’s not. It burns coal and it really confused me. But that’s a different story. [Laughter]

There is a group of people led by Ruth Bamford who have been working to do two different things. One is to better understand how is it that particles flow off of the Sun in our Solar System to flow out and potentially harm astronauts a lot?

What type of magnetic field is required in order to protect astronauts on the Moon on their way to Mars? What was originally thought and this is something people have been trying to figure out since the sixties was that you have to generate an artificial magnetic field that’s at least a hundred kilometers in size in order to get the plasma flowing off of the Sun to flow around the spacecraft rather than radiating on to the spacecraft and irradiating astronauts.

What we realized is the solar plasma doesn’t behave like a normal fluid. It doesn’t behave like water. It’s actually extremely turbulent. You can essentially just reach out with almost a refrigerator magnet and create a small sphere of safety. So it is possible with a moderate field that you can lift into space using a moderate sized basically magnet that you can protect an astronaut-sized volume of space.

The original problem was if you’re going to protect a hundred kilometers of space you need giant magnets and giant magnets weigh a lot. Or you need giant electromagnets which still weigh a lot and now have huge energy consumption. Now that we can do this with smaller magnets, it is thought that maybe by 2020 when we’re starting to plunk people down on the Moon we’ll be able to protect them.

These artificial magnetospheres they are creating are good at protecting astronauts from solar irradiation but they’re still not powerful enough to deflect the most high energy cosmic rays. To deflect those you need the Earth’s magnetic field. You need the Earth’s atmosphere. That we can’t recreate in space so we’re still out of luck.

Bob: Then even it would take more than modest technical improvement then to shield against high energy cosmic rays.

Pamela: Yeah.

Bob: That’s too bad. The other aspect of this that I found is really, really interesting when I was reading about this was that the magnetic field that they are generating they speculated that they could actually use that magnetic field as a solar sail of sorts that the solar radiation would impinge upon and actually allow for velocities greater than anything even the shuttle could achieve.

That was just another aspect that we talk about getting a bang for your buck. It would protect the astronauts and you [Laughter] could use it for propulsion. Maybe they still could in some way.

Pamela: Right we just need to figure out how is it that you stop the highest energy particles without having the Earth’s atmosphere. It’s this wonderful for every force there is an equal and opposite force.

If particles are going to get slowed down as they hit this giant magnetic field that we’ve created around the spacecraft that energy that came out of the particles is going to go into the spacecraft. So you can use it to push things around but it’s kind of hard to control your direction affectively.

It is things that we’re thinking about. We’ve come a long way since the 1960s. We’re starting to actually make progress and the folks over at Rutherford Appleton Station are doing a good body of research.

They’ve actually been able to do some of this here on Earth in artificial environments where they can generate sun-like fields and actually protect small spaces as needed. They’re working to scale it up to protect astronauts-sized spaces.

Bob: I just keep waiting for new technology for space propulsion because chemical rockets are great but if you really want to travel to the outer planets they’re just not efficient enough.

I keep thinking that they should just plunk down the money that’s required to create nuclear engines or something that is just much more efficient than the chemical rockets. I was hoping that this maybe could fill that role partly but I guess we’ll be waiting still.

Pamela: Solar sails are the way of the future. Nuclear engines one of the problems that we deal with there is there’s just a very limited supply of nuclear fuel here on the planet Earth.

This is one of the problems NASA is having right now. They just don’t have anymore nuclear engines or the material to make nuclear engines for satellites. Just like with oil we’re dealing with consumable resources.

With solar sails, the Sun is just going to keep doing its thing for another several billion years so we’re fine. Use it like a sailboat. The wind is still blowing and the solar wind is still blowing.

Bob: Absolutely, now on to inflation. Pamela you stated in the inflation episode awhile back that we can see 3 or 4 percent of the Universe.

I’ve always had trouble though trying to reconcile that idea with observations of the earliest stars or galaxies really deep time getting close to the actual Big Bang itself. How do you reconcile those two things?

Pamela: It’s all like imaging that you’re in the bottom of the ocean. What you’re able to see is limited by what your headlight is able to illuminate. Your normal diver’s headlight is only going to illuminate a certain size sphere around you.

For us the size of that sphere that we can see is limited by how far away are the objects that have had time for the light to reach us. That has nothing to do with how big the actual Universe is. The Universe could be infinite. We don’t think it is but that’s a guess.

When the Universe formed it underwent this period of inflation, this period of wild rapid inflation. If the Universe were finite in size then because we know lots of crazy things about its geometry a star radiating light, if the Universe were small enough the light would have a chance to wrap around the Universe and basically smack the star back in its face. We don’t have any stars old enough to have done that.

What astronomers have done is they’ve looked at the cosmic microwave background. They’ve looked for places where they can see two places that are reflecting the basically the situation of the same object, the same density profile in the early Universe. We’re looking for those reflections in the cosmic microwave background.

We’re not finding them and because we don’t see these places where in a finite Universe the cosmic microwave background could essentially say “these two points widely separated have both experienced the same density profile, the same waves propagating.” Because we don’t see that light that has wrapped all the way around the Universe we can say the Universe is at least 156 billion light years wide.

What we see is just the small volume of this vast ocean that is illuminated by the stars whose light have had a chance to reach us. The Universe that that small bubble is imbedded in we can get an idea of how big that Universe is based on the fact that we don’t hear the echoes of other divers reflecting off of different places. Without those echoes we know the Universe must be far, far bigger than what we can actually see.

Bob: Okay that definitely helps. I liked your analogy with the headlights. That’s a really good analogy. Would that mean then that the very edges of the light of our headlights would that be the edge of our observable Universe?

Pamela: Yes.

Bob: Okay but that would coincide with say what point after the Big Bang? Would it be at the point where radiation was what do they call it, photon decoupling where light was able to go through without interacting?

Pamela: That’s the moment of the cosmic microwave background release. That’s actually about 300,000 years after the Big Bang.

We look back and we can see the moments that atoms first formed and light was able to fly free without constantly interacting with electrons and protons and nuclei. We’re able to see that moment when the light first flew free as the cosmic microwave background.

Bob: Then the reason we can’t see beyond our observable Universe is because of the expansion of the Universe and the light from areas beyond that just haven’t reached us yet. Plain and simple and because they’re expanding faster than the speed of light then we never will.

Pamela: Right what we see is that cosmic microwave background which is opaque but it’s being emitted by every single point in Space. Somewhere else in the Universe someone sees a different cosmic microwave background, radiation, and sphere around them than we see. Just like two scuba divers are going to see two different spheres of water around them.

That edge of the cosmic microwave background that we see corresponds to a point 300,000 years after the Big Bang. The sphere that is enclosed by that cosmic microwave background is limited by the age of the Universe which is 13.7 billion years.

Bob: If you then extrapolate that into the future then because of the increasing expansion of the Universe then that sphere is pulling farther and farther away such that in the deep, deep future we really won’t be able to see that at all. It will be outside of the observable Universe. Is that right?

Pamela: Yeah, that’s one of the complex sadnesses of the Universe that we’re in. If we were in a Universe that was expanding slower you can imagine that we’d constantly see a bigger and bigger sphere around us. What’s actually happening is the Universe is expanding so rapidly that things are essentially running away from our ability to see them.

As the sphere which we can see gets bigger and bigger with each moment passing, the objects inside that sphere are bailing out the edges. As they bail out the edges with the expansion of the Universe they reach a point where they’re getting carried away by the expansion faster than the speed of light.

This is the analogy we use all the time: you’re standing on the sidewalk trying to walk, trying to run but the sidewalk is getting longer and longer and longer. If you and I start ten sidewalk blocks apart and each of those blocks doubles in size each minute I’d have to be able to run faster than that sidewalk is growing to eventually get to you.

If I start only two blocks away from you then after a second that’s four blocks and I might have a chance of in that period of time being able to run those four blocks and get to you. If I start ten blocks away from you then after a second we’re 20 blocks apart after another second we’re 40 blocks apart. This huge increase in distance between the two of us makes it impossible for me to ever reach you.

Bob: I remember Lawrence Krauss recently painted a very sad portrait of what it would be like far, far into the future when we reach a point where we literally couldn’t see beyond our local group of galaxies or I guess the super galaxy that we all will merge into.

Because of that future astronomers won’t be able to determine or learn anything about the true nature of the Universe, the Big Bang or any of that. We should be happy we live in an era where we can learn about the Universe and what it’s really like in the Big Bang because in the deep future astronomers won’t be able to.

Pamela: One of the uncomfortable things is one of the rules of cosmology is we don’t live in a special time. We don’t live in a special place. The reality is we do live in something of a special time.

We live during that period of the Universe’s evolution where we can see back to the cosmic microwave background. Where we can still observe the Universe around us and see a good chunk of the Universe and see super clusters, see the large scale structure of the Universe.

There is a distant future where all of that is erased by the expansion of the Universe. It gets even more bleak than that. If you hang around enough trillion years you actually reach the point where all the stars have died and even protons start to decay and we’re left with nothing but dilute energy being the only thing our mostly empty Universe.

Bob: It’s the heat death. So everybody look out into the sky and be happy [Laughter] because in a few trillion years you won’t be able to do that.

Pamela: Right so enjoy it while you can.

Bob: Okay so now let’s see, let’s talk about tidal forces. You did two episodes a while back on tidal forces. I really enjoyed them. One thing I would have liked to hear about the second daily tide on the opposite side of the Earth.

For years I tried to read various explanations that I would come across and nobody could really make sense. I found a website that made sense to me but I’ll leave it to you to tell me if it is actually accurate or not. [Laughter]

They described it as the second big tide caused by the rotation of the Earth around the very center of the Earth-Moon system; the point deep in the Earth where at the Earth and the Moon both rotate around.

This guy claimed that it created a centrifugal force which kind of pushed out, puffed out the ocean on the opposite side. Can you comment on that? Is that how it is or is there another explanation?

Pamela: I have a drawer in my desk that I put photocopies of test exam answers that are very wrong and nonetheless creative into. That website unfortunately belongs in that drawer. It’s just not quite right.

Bob: Okay.

Pamela: So the reality of the situation is the Moon’s gravity, it has a gradient. The closer you are to the Moon the stronger the gravity. The further from the Moon the less the gravitational pull that you experience. It is this one over r squared law.

Here on the planet Earth when you’re closer to the Moon you experience a greater pull from the Moon. When you’re further from the Moon, say 180 degrees around the planet such that if you could look straight through the center of the planet you’d see poking out the other side the Moon off in the distance.

On that distance side of the Earth the gravity from the Moon is a lot less. When we look at what the oceans experience on the side closest to the Moon, you have a high tide because well the water is getting yanked toward the Moon. Then as you start to move around the planet going 90 degrees in each direction you hit the point where you have a low tide.

This is an intermediate point where the Earth’s gravity is pulling the waters in and the Moon has an affect but the overall affect is less. The water is either flowing toward the side where it is getting yanked toward the Moon or it is actually flowing around to the other side where the gravitational attraction from the Moon is a lot less.

With the less force pulling the water toward the center of the planet on the far side you’re able to have high tides here because you’re not being compressed as much. You have the two tides, one on the side where the Moon’s gravity is the greatest and the other on the other side where the Moon’s gravity is the least. It’s all about the gradient of the Moon.

In reality because everything is in motion all of the time, the tides get carried by the Earth’s rotation out of being perfectly lined up with the Moon. That’s a minor effect, what we’re really worried about is this gradient from the gravitational pull of the Moon.

Bob: That’s an interesting point how the tide, the Earth is kind of pushing it away from being directly under the Moon. The effects of that are really interesting because that high tide and the Moon are pulling on each other which speeds up the Moon a little bit. Because it is speeding up it has to go into a higher orbit and therefore it is moving farther and farther and farther away.

Then back on Earth that pull is, the sloshing of the oceans is actually increasing the friction which slows down the Earth giving us a longer and longer day. Eventually for I don’t know how many millions or billions of years it would take we would be tidally locked and one lucky side of the Earth will always face the Moon – which would be pretty far away I would imagine. The other side of the Earth would never see the Moon again. Is that correct?

Pamela: Yes, that’s completely correct. This is all about the torques. Because the Moon’s tidal forces actually deform not just the water but actually the planet Earth itself, mountains get a little bit higher.

We just don’t think of it that way. This elongation of our planet gives a slight handle for the Moon’s gravity to yank on. The Moon is trying to slow the Earth’s rotation. Since our planet isn’t a perfect sphere, it experiences torques.

These torques are slowing the rotation of the planet and yeah over time we’re going to all end up locked together. The Sun is going to destroy us about the same time so I think we really don’t need to worry about it. [Laughter]

Bob: Right, I’ve read that there are actually atmospheric tides as well. A little more subtle than even the ground tides but they are there.

Pamela: It’s all about the gradient and the gravity.

Bob: Yes.

Pamela: Anytime you have things that can be flexed, be moved, be yanked around you’re going to end up with these deformations due to tidal affects.

Bob: I love tidal forces.

Pamela: They destroy things quite easily.

Bob: Yes, very dramatic. Okay, next topic. This one is a little whacky it was in the news. It’s a recent hubbub recently over the possibility of a holographic Universe. In a nutshell let me see if I can quickly do this justice.

The idea is that our three-dimensional Universe is actually potentially a projection from the cosmological horizon which is essentially the boundaries of the observable Universe. I was wondering what you thought of that Pamela. Is that as crazy as it sounds?

Pamela: Yeah, no. [Laughter] There are people who I actually really respect who’ve been working to try and figure out how to take what’s called the Holographic Principle which is a property of quantum gravity which doesn’t work yet to figure out string theory and the black hole information paradox.

There are some really high-powered guys working to figure this out. There are also some really New Age cranks working to propagate the notion. It is sometimes hard to decouple where the science is and where the crazy people are. So when you start talking about projections reality? We live in a Universe with a lot more dimensions than the one that we experience.

We experience up down, left right, forward backwards three spatial dimensions as well as the dimension of time. But, if string theory is correct, the idea that the different properties of many subatomic particles are actually just us looking at something that has its different aspects spread across multiple dimensions that we’re just seeing one side of it or the other. You can imagine a sphere passing through a two-dimensional surface and that if you existed only in a two-dimensional world a sphere would appear as a circle that got bigger and smaller over a period of time. A rectangle would appear as all sorts of different sizes, different shapes depending on how it passes through that plane.

What we might see is spin up versus spin down depending on which side of the string happens to be poking into our three-dimensional plus time Universe. At a certain level string theory of the Holographic Principle is talking about well there’s other dimensions than these.

Then crazies come along and they start talking about things that basically make it sound like there is the man behind the curtain throwing the switches to make our Universe appear the way it is; that we are some sort of a crazy projection of some other set of actions. That is where you start getting into crazy talk.

Bob: Okay, I was trying to imagine what would be projecting us. You think of a normal hologram where you have light reflecting off of the surface and creating a three-dimensional structure.

Maybe this is just a poor analogy but what’s doing the projecting? It’s really, really out there.

Pamela: Right and the best we can come to try and understand the idea of all these other dimensions is if you read the classic book “Flatland”. It is the ideas of in order for things to exist in two-dimensions that are three-dimensional you’re only seeing part of their aspects at any given moment.

You might only be seeing the cross-section of a human stomach but depending on where the human gets cut through in this different two-dimensional realities see different aspects of them.

It’s complex to try and sort out and then there’s also the idea that well perhaps in reality all of these extra dimensions are just rolled up and things that we’re incapable of getting any access to so it’s not really we’re taking cuts. It’s just that those different dimensions just behave differently.

There’s still not a precise mathematical language for trying to understand this. There are almost more theories of string theory than there are string theorists building new theories. It’s a new field. It’s still being developed. We don’t know if it is true. We don’t really have any tests yet to figure out if it is true.

It is something that is being experimented with in terms of people that are doing math because we know the theory of General Relativity is incomplete. What it does describe it describes accurately. It’s not a false theory; it’s just an incomplete theory. It breaks when we try and apply it to the regimes that are described through quantum mechanics.

It breaks down when we use it to try and understand the centers of black holes. We need to figure out how to bridge gravity in quantum mechanics and the math of string theory is the closest we’ve gotten but that doesn’t mean we’re right.

Bob: It’s just like Newtonian mechanics. It is fine in its own domain, low energy, low gravity low velocity but you need relativity if you start going too fast or getting too massive.

Pamela: Yeah.

Bob: You could launch a rocket and have it go right to Pluto and orbit it using just Newtonian mechanics. It is fine, relativity doesn’t replace it, it is just a special case.

Pamela: Right so things like our basic launching the space shuttle. No GR required. Things like the GPS systems that like what I use to navigate when lost in other cities. That does actually start to require general relativity. General relativity works or GPS wouldn’t.

If you want to travel to the inside of a black hole – which I don’t recommend – then you start to have to understand quantum gravity and we don’t have that theory at all.

Bob: I’ve been waiting for that one. I don’t know what’s taking so long. [Laughter]

Pamela: We need more geniuses, that’s all. Get busy, have a genius child.

Bob: Okay, astronomers can’t escape the fact that as you observe more distant objects the further back in time you’re seeing because obviously it takes times for light to propagate these vast distances and that’s great.

It’s great for seeing the evolution of the Universe and looking back in time but I’ve always wondered what would the Universe look like right now? So my question is what would the Universe look like if the speed of light was infinite? What would we see?

Pamela: We’d see a lot of light. [Laughter] It would hurt. We have two problems and I’m going to explain one of them and then temporarily say we’re going to ignore that. The first problem is if light could travel instantaneously then some object 150 something billion light years away, its light would be shining on us right now.

With a Universe that big it is hard to imagine that there would be many directions that you could look in that wouldn’t have a line of sight that ended on a star. If we do live in a finite Universe which means that the light can wrap around and hit itself in the face, then the light would be doing that. That really makes it pretty much impossible to imagine a direction that doesn’t have light coming from it.

This constant flux of light would be like having a spotlight in your eyes all the time. You can’t make out anything else except for this light blinding you. That makes it hard to explore the Universe. But we have dust. Dust might be the saving feature.

Where the most distant light is actually getting absorbed and maybe, maybe there is enough dust that would hopefully allow us to see some amount of distance but maybe not. With all that light it would heat up the dust. It would ionize things and it is just a mess. But, let’s pretend – we’re going to pretend that this total flood of light doesn’t make it impossible for us to see out to some sort of a distance. In that case what we’d miss is being able to see the young Universe. What we’d see as we looked out is this consistent Swiss cheese large scale structure of the Universe.

Our Universe is slowly turning itself into a giant sponge with bigger and bigger voids between denser and denser junctions between the bubbles. Right now as we look out to greater and greater distances we see those bubbles filling in. We see them getting smaller, the voids getting smaller, the clusters getting smaller as the Universe goes towards a more uniform density back in the early days.

With an infinite speed of time we’d never see that evolution. We’d look out and it would be like looking out through a constant density sponge Universe. Take your kitchen sponge, replace the molecules with galaxies and that’s what we’d see.

Bob: Interesting. I know when you look back and you look at the space and you see back in time you see the young Universe and that’s great but I always wanted to know if you could somehow observe that everything at once.

What’s going on right now you know however many million, 20, 30, 40 billion light years away? What’s it like? What’s going on? You can’t know. We can never know, we can only speculate. [Laughter] It would be fun if we could just briefly see what’s going on.

Pamela: What is cool about this is right now if we saw civilization that was 5,000 light years away, we’d be seeing it 5,000 years ago. Now who wants to look at Earth’s civilization in terms of being able to communicate with it in a technologically advanced kind of way as we looked in oh 3,000 B. C.

Not much to communicate with via radio signals but radio is a color of light. If radio could travel instantaneously we could communicate instantly like in the Orson Scott Card books.

We could communicate instantly with these civilizations around distant stars. That’s the one cool thing. It would be nice if we could figure out how to make just a couple wavelengths go instantly.

Bob: That would be nice because now it would be “Hi, how are you?” wait 20,000 years. “Oh we’re fine. How are you guys doing?” [Laughter]

It’s kind of a lonely conversation, but then again they could be broadcasting the encyclopedia Galactica and we could just soak it all in. We could send them ours. They’ll just have to wait for it.

Pamela: Yeah, it has some interesting features; it’s just the whole going blind bit that might be a bit difficult to take.

Bob: Yeah, that’s nasty.

Pamela: Bob it’s been a pleasure having you on the show. Wow we went overtime which is us making up for the missing episodes. Fraser please get better, we miss you.

Bob: Yes Fraser. And I am very grateful for this opportunity. I had an awesome time. This time just flew by and you’re so easy to talk to Pamela, it was great. I really enjoyed it.

Pamela: It was my pleasure and we’ll have to have you back when Fraser is on the show as well and you both can pick my brain and torture me.

Bob: Yes, that would be fun.

Pamela: I do enjoy this and thank you. Do you want to give out the URL so that people can go listen to your show?