Consider the Universe. Now, Subtract Time and Gravity.

8:02 minutes

You may have read news recently that we’re living in a giant hologram. That the universe is just an illusion, projected holographically from a two-dimensional reality.

Mind-blowing, right?

Those click-bait headlines may have gotten a little carried away with that sci-fi scenario. But holographic cosmology is a real thing. It’s a different way to push the numbers around, as cosmologists model the Big Bang and other phenomena like black holes.

The models work by eliminating gravity, and one dimension—either time, or a dimension of space—to simplify the calculations. It’s just unclear whether those holographic models will ultimately prove to be any better than the ones we already have, such as the Standard Model.

Astrophysicist Niayesh Afshordi and his team wrote about their models of the Big Bang in the journal Physical Review Letters. In this segment, he explains how holographic math could help us bridge some common conundrums in cosmology.

Segment Guests

Niayesh Afshordi

Niayesh Afshordi is an associate professor at the University of Waterloo and the Perimeter Institute in Waterloo, Ontario, Canada.

Segment Transcript

IRA FLATOW: Next up, you may have read the news recently that you and I, well, we’re living in a giant hologram, that the universe, it’s just an illusion projected holographically from a two-dimensional reality. Mind-blowing stuff, right? Well, let’s just say those reports may have gotten a little carried away with that sci fi scenario, but there is some useful information here. Holographic cosmology is a real thing, and it is a way of simplifying the equations, a different way to push the numbers around.

And my next guest is one of the lucky cosmologist who gets to do that math. Niayesh Afshordi is associate professor at the University of Waterloo and the Perimeter Institute in Ontario, Canada. He and his team wrote about their models in the journal Physical Review Letters. Welcome to Science Friday, Dr. Afshordi.

NIAYESH AFSHORDI: Thank you, Ira. Good to be with you.

IRA FLATOW: It’s good to have you. Are all of those stories about we live in a holographic universe really just going a little bit too far?

NIAYESH AFSHORDI: Maybe, maybe not. Depends on how high your imagination, how imaginative you are. I guess that’s the way to put it.

IRA FLATOW: What do you mean?

NIAYESH AFSHORDI: So that’s good. I think there is a lot of it that’s imagination and fiction, but there is some truth into it, and that’s actually something that physicists have been thinking about for actually for the past 20 years if not longer. And that goes back to one of the deepest mysteries in science, how do quantum mechanics and gravity work together? And that’s a mystery that has been with us since Einstein.

Since Einstein discovered relativity and others discovered quantum mechanics, we never really know, we never really learned how they talk to each other, and it’s been 100 years since then. So the holography is this new language we learned in the past 20 years or so that maybe there’s a way for these two to talk to each other. But for that you have to lower at the number of dimensions.

IRA FLATOW: So yes, you have to either take out what, time, or–

NIAYESH AFSHORDI: Good. So you could take out one dimension. You could take out one dimension of a space or you can take out time. It really depends on the situation what makes the calculations easier. So what we have looked at and with our collaborators and my student Beth, we looked at how this thing works out during the Big Bang.

Big Bang is one of those places where the universe is very complicated, because that’s one of those places where everything becomes very massive but also very small so that you need to use both gravity and quantum mechanics. And we think holography can be actually applied there and we can understand what’s happening during Big Bang.

IRA FLATOW: So if you take out some of those dimensions and you apply holography, do you arrive at any new insights into the nature of the Big Bang– what it was, what happened, that sort of stuff?

NIAYESH AFSHORDI: That’s our proposal. That’s our proposal. So, if you look yourself right now, it looks like there are three dimensions, and everything seems consistent with that notion of three dimensions. There is time, that’s one dimension, and [INAUDIBLE] spatial dimensions. You can go back and forth, you can go left and right, and you can go up and down– or jump up and down, if you will.

If you go to earlier and earlier in time, so sometime around 14 billion years ago, we have lots of great data, observational data, that tells us Big Bang or something like that happened. So the universe was very hot, very dense, and everything was much smaller than we see today.

At that time, this notion of number of dimensions, three are space and one time, looks like it doesn’t work very well because quantum mechanics doesn’t talk to gravity. And it looks like if you take out one of those dimensions, like for example time, then it’s much, much easier to understand what’s going on. And what’s amazing is that you can actually make predictions and fit the data, observational data, that come out of the Big Bang.

IRA FLATOW: I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. So what you just said, what you were saying, is that even if you– so you take out some of the dimensions and then suddenly the data fits.

NIAYESH AFSHORDI: Suddenly the data fits.

IRA FLATOW: Does that mean that you are better at the standard model, equally relevant to what you’re saying? Or one is better than the other.

NIAYESH AFSHORDI: The problem is there is no standard model when it comes to conditions like that of the Big Bang. We have different ideas, different fictions, if you will, or different histories, different models what might have happened, but we really don’t have any way of testing them directly because we don’t have time machine that could take any scientists back to the Big Bang.

Even if we did have time machine, I don’t think people want to send a scientist back to extreme conditions. It’s probably much worse than the conditions you were talking about in your previous section. And so that’s why we don’t really know which of these stories or histories might be right. What we discovered is that it is actually simple as if you just take out time, or any dimension, then you can come up with a very simple model that fits all the data that we have.

IRA FLATOW: But you’re not quite ready to replace the standard model.

NIAYESH AFSHORDI: Well, good. So the question is what is the standard model good for? And the standard model is good for everything that we see around us. At the early times, then it’s still is a question of what will the preponderance of evidence point to? And right now the standard model is roughly the same point as the holographic picture is. But there will be much better data very, very soon, and hopefully we can pick which one is better.

IRA FLATOW: So you’re saying it all falls apart when we get that far back.


IRA FLATOW: And by using your method, you and eliminating time or some of the dimensions, you might be able to probe that spot that no one really knows about. And I know that you spoke with one of my colleagues and you didn’t use the word history when we talked about it. You used the word story.

NIAYESH AFSHORDI: Well, I used the word a story, which is like what you tell your kids when you want them to go to bed. And that’s the way I really think about it is that history is something that kind of you’re confident about, but the stories are kind of things that might have some reality in them, but you don’t really know.

And I think we have lots of those stories that we can tell our kids or tell other scientists about. But it’s very hard to be sure of which story is the right one. And we are proposing let’s just take out the story and just stick to the facts. And that’s basically what holography is when it comes to the Big Bang.

IRA FLATOW: Do you think that the holographic map could bridge quantum mechanics and gravity, the two that are not bridgeable yet?

NIAYESH AFSHORDI: That’s the hope of this program, and we’ve been pushing this and lots of other scientists have been pushing this. And what we are happy about is this is the first time we can actually connect this with real, hard observations. But in the future I think there will be much more progress, and hopefully by learning the language of holography better we can say more about how quantum mechanics and gravity talk to each other.

IRA FLATOW: So we’re not actually living in a hologram.

NIAYESH AFSHORDI: I think it’s all in your mindset. I think if you feel happier living in a hologram, then, all power to you.

IRA FLATOW: That’s the great quote of the week, and I want to thank you very much, Dr. Ashfordi.

NIAYESH AFSHORDI: You’re welcome. It was fun talking to you.

IRA FLATOW: Niayesh Afshordi is an associate professor at the University of Waterloo and Perimeter Institute up there in our friends in Ontario, Canada.

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