We’ve talked about stellar cannibalism and galactic cannibalism, but now it’s time to take this concept to its logical extreme – universe cannibalism. In the multiverse theory of physics we live in just one of a vast range of universes which might interact with each other. Let’s look for the evidence.
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Fraser Cain: Astronomy Cast episode 408 Universe Cannibalism. Welcome to Astronomy Cast where give you facts based journeys through the cosmos, we help you understand not only what we know but how we know what we know.
My name is Fraser Cain I’m the publisher of Universe Today and with me today I have Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville and the director of CosmoQuest. Hey Pam, how you doing?
Pamela Gay: I’m doing well. How are you doing Fraser?
Fraser Cain: I’m doing really well. So you made it back safety from the Lunar and Planetary Science Conference.
Pamela Gay: I did. I sadly had to leave all the awesome new science about Pluto, and Mars, and Ceres and everything behind. But now I’m home to work on awesome science, I hope.
Fraser Cain: What was the you know, 30 seconds, the biggest, coolest thing that was announced there?
Pamela Gay: There are 5 Kilometer high water mountains floating on a frozen nitrogen ocean on Pluto and no one knows why.
Fraser Cain: Whoa. Okay.
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Fraser Cain: So we’ve talked about Stellar Cannibalism and Galactic Cannibalism and now it’s time to take this concept to it’s logical extreme. Universe Cannibalism in the multiverse theory of physics we live in one of a vast range of universes which might interact with each other. Let’s look for the evidence.
Is there some kind of Walking Dead theme here, going on Pamela? Have you been like, really following along?
Pamela Gay: So, I have to admit, I’m a Loot Crate subscriber and last month’s Loot Crate was zombie themed and as I stared at Walking Dead figurine, it wasn’t actually zombie themed, but it had Walking Dead, Deadpool, it was death themed.
Fraser Cain: Death themed.
Pamela Gay: As I stared at this stuff sitting on my desk, I was like ‘And, we shall discuss cannibalism.’ Just, it was just the direction I decided to go. I love my Loot Crates.
Fraser Cain: You are super gross and such a nerd. And I say that with love. As always, we kinda like to take things up to their logical extreme. And I didn’t think you were going to go here. I thought you know, we were talking about galactic, vast galactic structures coming together within the very limits of gravity. That’s as much collision and cannibalism at a universal level as you could possibly pull off. But no, no. You upped the ante, so when you talk about universes eating other universes, what are you talking about?
Pamela Gay: So, this is actually still within our facts based journey through the cosmos. Where, when we look at the Cosmic microwave background we know that there is the potential to find evidence of our universe bumping up against other universes and getting, they call it bruised. Because we have to anthropomorphize everything, getting bruised in the process of bumping into other universes. And it’s theoretically possible that if we do more than just bump our neighbors, we’ll actually all die and this is kind of catastrophic way that we can destroy the planet. It’s not with an asteroid, it’s not with a gamma-ray burst, it’s via universe cannibalism.
Fraser Cain: Okay, okay, okay. So, first.
Pamela Gay: I don’t usually get to do this to you!
Fraser Cain: I know, I know. What you’re seeing is me not even knowing where to start. Okay, so the first step concept is the idea that there are multiple universes, right?
Pamela Gay: Yes.
Fraser Cain: And if I go back in time, and we talk to other Pamela’s in the past, perhaps in this universe and not other universes, she would say that the universe is all there is, the universe isn’t expanding into anything, there’s just the universe. The universe is fully self-contained, you know, it could be infinite in size, it could wrap around on itself if it’s finite in size, great. So how can you have multiple of these universes?
Pamela Gay: So, we have discussed multiverses in other shows, and the idea is that back during the age of inflation it is possible that, that pocket of inflation smoothed out our universe, didn’t necessarily stop everywhere or that it didn’t stay stopped everywhere. And over time, new pockets of inflations created entirely new pocket universes, bubble universes, side by side spawning off of our own. And we’re part of this multiverse foam of bubbles that each have slightly different physical perimeters.
Fraser Cain: Okay, stop. I’m going to do this a lot today. Just, like, prepare yourself for this. So we’ve got, like, the universe.
Pamela Gay: Yes.
Fraser Cain: And it’s not the universe as we understand it. What we understand as the universe when we look back, when we follow back to the big bang, as like, the singularity leading to inflation and then the expansion that is actually just one bubble universe embedded in a larger framework of whatever is out there?
Pamela Gay: Yes.
Fraser Cain: Okay, alright. No problem, I got this, fine. So these things across this larger expanse are just, you know, expanding from singularities and forming universes, maybe with the same rules we’ve got, maybe with different rules?
Pamela Gay: Probably with different rules. What’s really cool, so the whole idea of inflation was something that came from Alan Guth. He actually figured out while he was in, I think it was his 9th year being a postdoc that point in your career where you’re like, ‘I’m never going to get tenured.’ And then he kind of figured out the key to cosmology, life, the universe, and everything.
A few years later, other people including Andrei Linde, perhaps most famously figured out that the inflation doesn’t have to stop. You can end up with these multiple universes. And this takes care of the problem that it appears that physics and our universe is fine tune to life. Because we don’t want anything to be fine tuned. We want just old straight old either underlying physics, dictates the way things are your can tweak things around a lot and you still get close to the same results.
The fact that if you change things like fine structure constant just the tiniest amount no more universe really bugs people. But with this multiverse possibility, each different universe can be a different rolling of the dice you might say. And so we’re no longer finely tuned, we just happen to be in the right dice roll.
Fraser Cain: Right. If my parents hadn’t met, I wouldn’t be here to think about my parents meeting.
Pamela Gay: Yes, but way more to the point, we have just the right balance of dark energy, dark matter and baryonic matter that stars, galaxies, and humans could form.Whereas in other universes it might have just gone ‘crunch.’ So, we’re finely tuned to life instead of a crunch.
Fraser Cain: I mean this idea is very satisfying. From, you know, because it’s sort of a great idea that you have like this vast expanse of something and at some point, some event sets off a big bang. And you know, there’s this great idea of, even with quantum theory that if you wait long enough, long enough, like you know, you don’t have enough zeros to wait long enough. You will get a universe’s worth of matter all at one location, appearing spontaneously, right?
Pamela Gay: Right.
Fraser Cain: And then, as you say, you roll the dice. Like here you go, there’s no such thing as gravity. There’s only anti-gravity and fine search con you know, number is 12. So, and you get one of these universes popping off. It just, it really blows your mind to put to scale in terms of time, in terms of size, in terms of number of times you’d have to roll the dice to get a universe with the kinds of constants we have in ours.
Pamela Gay: And folks who try to use string theory to come up with an underlying physics would require the set of parameters we see in our universe, actually got flummoxed because they found I believe it was 10 to 500 different possible perimeter sets, and none of them were required by the underlying physics. So, there is at least according to some string theory theories, and we all know how I feel about string theory, but their finding order 10 to the 500 different combinations of ways you can build a universe.
Fraser Cain: Right, and so, you know, and that’s just the multiverse theory. And we have done a whole show on this, you just have to search for Astronomy Cast Multiverse, you can go back and find that we talk about this and other kinds of multiverses. This is just one theory of a multiverse.
But now, let’s talk about the cannibalism portion of this. So, where does these universes colliding or interacting come from?
Pamela Gay: Well, what’s kind of interesting is the mathematics behind it, in some ways actually comes from a scientist getting a phone call from a journalist asking, ‘so, what would happen if universes collide?’ and people hadn’t really thought in a lot of detail about this. And it was Anthony Aguirre, sorry if I mispronounced it. Who actually got this phone call and did this thinking, and he realized that this is actually something that is kind of cool to think about, that has a really low probability, probably but could lead to observable side effects.
Fraser Cain: Okay, such as?
Pamela Gay: Well, if you have 2 galaxies, not galaxies, if you have 2 universes, much more interesting than galaxies. If you have 2 universes, that have roughly the same energy colliding. It’s sort of like 2 bubbles that have the same pressure on the inside and have fairly good surface tension bumping. They’re going to actually just bounce off of each other. If one of them is weak walled, if there’s a huge difference in internal energy, they’re going to eat each other.
But, if they’re reasonably similar they’re going to bounce off of each other but there’s going to be deformation that occurs at that point where they bump into each other. And theorist, after theorist, after theorist, in different ways has looked at this bump and come up with the idea that you end up with a bruise in the cosmic background.
Literally in the cosmic microwave background radiation, you potentially see a place where there’s less energy than you would expect. And it turns out, that in our cosmic microwave background there’s a cold spot where there’s less energy than you would expect.
Fraser Cain: Huh, okay, okay. So, you’ve got this like, 2 bubbles. I’m just sort of imagining, bubbles and I’m sure this is the best our poor meat and monkey brains can imagine, right?
Pamela Gay: Yes.
Fraser Cain: Is bubbles expanding and when the 2 bubbles come together, you get this region where they’re not necessarily kind of overriding each other but they’re at least cooling each other down a little bit.
Pamela Gay: Yes, and it’s a loss of energy through the collision, a cool spot. And this is something that we can go and look for. And another thing that has been predicted, in this case, by Kate Land, and there’s some debate on this, but it looks like there’s the potential that you could actually have gravity leak is word that they use from one of the colliding universes to the other and create some sort of a galaxy flow. That would be observable within our universe as a part of the sky that appears to be moving in ways that it otherwise probably shouldn’t.
Fraser Cain: Right. Okay, okay. And that would explain, one of those ideas, that would explain why gravity is just not on the same scale as the rest of the universe. So would that-
Pamela Gay: That’s a different kind of gravity leakage. This is literally like, take a part of the universe, looks like there’s something pulling on that part of the universe. Only that part of the universe, that isn’t pulling everywhere else.
Fraser Cain: Right. Okay. So then, what would that look like? Say that we, I’m assuming that we’re going to look at the cosmic microwave background radiation.
Pamela Gay: You can actually look at the galactic scale structure for this one. And so what you’re looking for, is a part of the sky that appears to be moving in ways that can’t be explained when you add up all the visible and dark matter mass up there. And so what we need to do is go and look for some sort of a large scale flow in the motions of objects in the universe. Which incidentally we have also found.
Fraser Cain: Well isn’t that The Great Attractor or we looking for something on a way bigger scale than The Great Attractor?
Pamela Gay: This is a bigger scale. This is something we refer to as the Axis of Evil just because we like to give things weird names. So this is again, Anthony Aguirre refers to it as the Axis of Evil it’s an area on the sky where we see a large scale flow.
Now, the problem is that all of these things that we are observing, don’t necessarily have to be explained this way and there’s lots of reasons not to explain them this way. But, we’re at the edge of our understanding. And this is where it’s cool to look at what are all the possible ways to try and understand what we’re observing in our universe. What is factually possible, and what is most probable and least probable.
Fraser Cain: Okay. So what is most likely?
Pamela Gay: So most likely is all of this is bollocks and we can’t actually observe any signs of a collision and this cold spot in the cosmic microwave background that has been observed both the Wilkinson microwave and anisotropy probe and with plank and other large scale anisotropies that we see is just a matter of incomplete foregrounds, subtraction, and other biases. And how we’re doing the data reduction not in the instrument, because we’ve seen with 2 different instruments but other biases, we’re trying to understand the universe that are causing us to not correctly understand the data.
Fraser Cain: Right, okay, okay. It’s like, you know, with the discovery of primordial gravitational waves. There’s something in the way, that messed up your data and what you thought was a huge chunk of the universe sliding towards another universe is actually just, you know, some dust in front of your telescope.
Pamela Gay: And foreground corrections to the cosmic microwave background is one of the most finicky things that we have to do in science. Because you have to take into account all of the different stuff out there that is going to be gravitationally lensing this background, cosmic microwave background light and all the things that are going to be subtracting out energy, adding in energy, as essentially pollutants and it can be stuff as nearby as our Oort Cloud that affects what we’re seeing or as far away as the intervening dust and gas in the other galaxies out there.
Fraser Cain: Wow. Okay. So, that’s really the most likely, that you know, so bad data. What is sort of less likely, but cooler?
Pamela Gay: What’s less likely, but cooler. Is we’re actively observing the bruising of our universe that occurred when at some point in the past we gently bumped, ever so gently because we’re still alive, when our universe bumped up against another universe. And it bounced back off again, we’re still alive, and that bump left it’s literal impression in the cosmic microwave background.
Fraser Cain: Wow. But how, we see that as a cooler spot. But how would that sort of explain the Axis of Evil?
Pamela Gay: Well, so the idea, and again this isn’t necessarily, it doesn’t necessarily work this way. But the thought is, and there’s been several different people who worked on this but, each of them has either disproven themselves or been disproven by somebody else, and gone back to the drawing board.
But, the idea is for multiple different pathways you end up with this idea that you can have a bulk flow where an external universe one of the multiple, multiple, multi-universes out there, pulled during the collision on stuff inside our universe, and it’s left a remnant bulk flow that can’t be accounted for matter that’s in our universe.
And so this is where you go looking for these unaccountable bulk flows. And the Axis of Evil is one of those things that people keep going, ‘That. That, maybe that’s it!’ And then other people come along and go, ‘Mmm, maybe not.’ So that’s one of those things where in order to prove the extraordinary you have to have extraordinary evidence and people are going to go, ‘Mmm, probably not’ until absolutely every possible idea other than this was produced through colliding universes is ruled out.
Fraser Cain: So, I mean the way it seems right now it seems fairly harmless, you know. Like gravitationally, some galaxies are going to slide toward the mass the gravity of that other universe. But how can we make this catastrophic?
Pamela Gay: Well, so.
Fraser Cain: You know, that other universe is trying to kill you too.
Pamela Gay: Well so, the thing is, if we are seeing a bruise on the sky, and we’re going to keep looking for these in the future. All we have to do is find perfectly circular little blobs in the cosmic microwave background, and people are out there looking for them. If we find these evidences of bouncing off of other universe that evidence of low impact events. Well, if you can have low impact events, you can probably have high impact events.
And this is the case of when you see 2 bubbles collide, and instead of becoming 2 bubbles bounce off each other, or 2 bubbles that sort of hang out, making a giant blobby 8, but they instead become 1 new bubble. Well, one that 1 new bubble forms, when it’s the universe is doing it, you end up with, basically all the physical perimeters of 1 universe merging with the physical perimeters of the other universe and everything being destroyed. It’s described as seeing a giant reflective mirror, the size of the sky flying at you at near the speed of light. The law between one set of physical laws and the other essentially acts as a mirror.
Fraser Cain: I’m sort of imagining, like you take, you know, 2 liquids, 2 different colored liquids and you pour them together. But instead of it being liquids you’re talking about, you know, the measurements of gravity, fine structure constant, right?
Pamela Gay: Yes.
Fraser Cain: You know, like in our universe, gravity goes at the way that it goes. But in that other universe, gravity is repulsive or whatever, right? Or it’s green, you know? You know, oil and water going on here when the two gravities come together and for anyone’s caught in the mixture of that, you’ve essentially got new rules, and they’re not good ones.
Pamela Gay: This is essentially the great nothing of The Never Ending Story sweeping in and destroying everything. And screaming moon child is not going to rescue our universe.
Fraser Cain: Right. Or their other universe’s version of it. Yeah, that kid can’t help either. So, what would that look like? If we could see that out in the universe?
Pamela Gay: Everything that I’ve read said that it would either look like a giant mirror flying at you at close to the speed of light. Because the idea is that light hitting this physical barrier would refract off and reflect backwards. Or it would be a great nothing racing at you at close to the speed of light.
Fraser Cain: Right. And it could very well be that it’s the mixture of the 2 laws of gravity or everything?
Pamela Gay: Everything.
Fraser Cain: Or everything, anything, nothing.
Pamela Gay: I mean fine structure, perimeters changing, the bulk balance between matter and dark matter. Heck, it could be an anti-matter dominated universe decides it wants to become 1 with us and everything just needs to annihilate for sport.
Fraser Cain: But couldn’t you theoretically, though, have that be a different kind of universe inside of that. You know, that if the rules mix together, you end up with some other universe’s rules and maybe that would seemingly perfectly, you know, positioned for life?
Pamela Gay: Yeah, but you would die while it was in the process of forming.
Fraser Cain: Mm-hmm. Yeah, absolutely, no. It would not be for us, it would be for the next people.
Pamela Gay: Yes.
Fraser Cain: Yeah. Whoa, that’s crazy. But I like this idea, right? You would see a reflection in the cosmic microwave background. In the most distant parts of our observations. Perhaps James Webb would turn something up like that.
Pamela Gay: It’s really a Stephen King kind of way to die. And it’s not so much a James Webb telescope kind of problem as the successor to Plank. So one of the interesting things that they’ve done in trying to understand, ‘did we collide with something or not?’
A collision would leave a circular artifact on the cosmic microwave background. And simulations have been done to figure out, ‘okay, if you feed our modern data reduction software and instrumentation, and everything that alters reality to be what we observe, if you feed various kinds of simulated universes into the data reduction pipeline how many circular artifacts do you expect to randomly encounter?’ And the answer’s 10. Which is kind of cool, 10 random things should be produced.
And when you look at the actual universe, there’s 14 circular artifacts identified and 4 of those are in a part of the sky, it’s kind of squarely we’d kind of expect actually this part of the sky would easily produce circular artifacts. So, it’s something that we’re actively looking for and we have the data ability to do. But we’re still at the comparing simulated with actual to try and tease out, ‘well, what’s the probability that what we’re looking at is just an artifact.’
If we get better resolution, so that we’re not doing all of these simulations, to try and tweak out, ‘is this expected or is this bruising of the universe?’ It’s possible that we will with higher resolution, start to see, ‘why, yes we did indeed collide with something in the past and we need to worry.’
But as one of the scientists put it, he doesn’t generally worry about dying by getting hit by a car crossing the street in New York City. And so he’s not going to generally worry about dying because our universe collides with another universe. So yeah, it’s possible. Any given one of us might die crossing the street in New York City and people do die that way. But our entire planet, it’s pretty small fraction and it’s probably a very rare possibility that in the history of the universe we will die via universe collision.
Fraser Cain: Or if not, you know, when, the heat death universe everything cools down. Or when the universe randomly collapses to it’s final energy state. So, the universe has got so many ways to kill us.
Pamela Gay: To kill us.
Fraser Cain: Yeah. It really, it’s got it’s choice.
Pamela Gay: Yes. Fire, ice.
Fraser Cain: Yeah, and if it doesn’t come up with it, then other universes will do the work. If it doesn’t have the guts to take us out, those other universes are going to do it.
Pamela Gay: It’s true.
Fraser Cain: So, are we done with this series, Pamela? Can you take this any further or have we reached the end of the Cannibalism Series?
Pamela Gay: I think we’ve reached the end of our Cannibalism Series.
Fraser Cain: Okay. Alright, cool. That was really wonderful. You know I love to talk about this kind of stuff, so thank you so much for agreeing to stop by. And that was awesome. Thanks Pamela.
Pamela Gay: Thank you, Frasier.
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