I know it's like partly a joke, but there are people who with a straight face really do say that. You guys said you'd wrap it up in five or seven years, what's going on? And I just have to keep educating them that science is not like, you know, a company where you lay out your product development timeline.
You have goals. And as you're going toward those goals, new ideas emerge and follow those new ideas. They take you to wonderful, crazy places.
And As long as you're not stuck, and we're far from stuck. When you put it that way, it kind of sounds like someone is saying to you, now the assignment was figuring out the entire universe. Why are you late? Why is your paper late? All he asked you to do was figure out the entire universe, and yet here you are saying you need more time.
I have said this publicly to Brian on stage. This is not differently mean-sounding than when I first said it. I've asked string theorists what's taking you so long? And they say, it's a hard problem. Wait, wait.
So I said, maybe you are all just too stupid. That's not a consideration here that we need a different crop of people to enter your field? Well, I would say it's somewhat differently. Could it be that the species, the human species is too stupid? That's a real possibility.
I mean, there's a lot of evidence to back that up. I'm just saying. Can you even take it out of our species, right?
I mean... I respect the intelligence of dogs. They do some remarkable things, but they don't do quantum mechanics.
So there's a species that has a limit on how well it can understand the deep laws of the universe. And so why would we be any different? I think it's a miracle. We're not at some limit of understanding here.
I think it's a miracle how far we've gotten. We all know a cocky physicist a century ago saying, physics is done. There's no more physics to be discovered.
Just a few decimal places and a few... touch up some constants and we should take on another field. Where do you see the field right now? Well, there's a huge amount of progress, but I can certainly envision that if we don't build new accelerators and if we were to stop building powerful space telescopes, we wouldn't have any new data.
And without new data, I can imagine, I don't know, 10, 20, 100 years of totally abstract theoretical research might grind to a halt. And it wouldn't be that we'd sort of reach the end. We'd simply reach the end in that era until we had the wherewithal to explore more fully.
There has to be an interplay between observation, experiment, and theorizing. We're far from there now, but can I envision that if we lose the will, could we reach an end for a while? Sure. Absolutely. So, Brian, can't we talk about a center of the universe?
And so we say that's the direction of the center of the universe. Go there and you'll see it. And that direction is... Back in time to T equals zero. Center, to most people's minds, is a special location within a larger reality.
That, we don't think, applies anywhere or any when. So if you even go back to the Big Bang, the conventional story, although there are modifications of this, but the conventional story is all of space is in this point. It's not as though it's a point in a pre-existing... rail once the expansion takes place it's like what is the center of a ball or the surface of a ball yeah on the surface that's the key thing because if you then imagine the center of it then you're misled but on the surface of a balloon all points are equal and there is no central point everyone knows e equals mc squared how is the formula actually used in practical terms where do you use that formula you don't use it much of course in everyday life but if you're Looking at a nuclear reactor and you want to know how much fuel needs to be put in, it gives you an order of magnitude sense, you know, of what it will require.
If you're trying to understand the sun and the amount of energy that's produced by fusion reactions, it gives you a sense of the scales that are involved. Now, how to actually use the formula? The key thing that you learn in science is you have to use consistent units. So, you know, kilogram meters per second is the... The units that we typically will use, and so if you want to use those for mass and for the speed of light, that's a really good way of getting an answer out in joules, which is a particular unit for measuring energy.
Does quantum mechanics prevent an infinitely small singularity inside of a black hole? I thought nothing could be smaller than a Planck length. So a Planck length is a very specific number.
It's about 10 to the minus 33 centimeters. Incredibly small. If you take the mathematics too seriously and you push it into infinitely small.
are infinitely dense, then you do run into the kind of questions that the questioner asks. Like, doesn't that conflict with the statement that you can't really go smaller than the plank length? So you're saying it's a mathematical singularity, not a physical singularity. That mathematics admits that there's a point beyond which general relativity does not apply. Yeah, especially when you put general relativity and quantum mechanics into a combined theory.
So it's only when you try to have a more complete description that you have. all of these ingredients, we are told from the math, hey, you've got to start thinking differently when you get to the plane claim. I do think that the universe evolves by laws that do not have an opportunity for humans to intercede. And so is there a kind of predestination built into physical laws, even with the probabilities of quantum mechanics?
Yeah, I would say yes, there is. So if a photon leaves the center of the galaxy, if I were able to watch it travel, and stick a mirror halfway through to just ascend it off in another direction, the photon on being emitted didn't know I was going to do that. Could that have had a different fate than the one I gave it?
No, but I would also say that your act of putting the mirror was also predetermined in the similar sense that you're a collection of particles governed by physical law, and I don't believe that you have intrinsic control over those. particles because you don't control Maxwell's equations. You don't control Einstein's equations.
So you think. When you look at Einstein's special relativity, something goes closer and closer to the speed of light and we're watching it. Time will lapse ever more slowly for it. So if you take that to its logical extreme, at the speed of light, no time would be elapsing for a photon. Poetically, that's true, but photon doesn't have any consciousness.
It doesn't have any means of reporting experience. Those ideas don't really have any relevance. So to say that time doesn't elapse, that photon doesn't age, is a very human description of what's going on.
And this is a perspective that we humans could never have because massive bodies can't ever travel at the speed of light. So there's a barrier for us to ever really know what that experience would be like. What do you think? will be the next major breakthrough with respect to the universe. I think that in the next, who knows, next few decades, we're going to have a much more refined understanding of the Big Bang.
We'll finally be able to answer questions that we began with, like what really do we mean by the singularity of the Big Bang? What really happened there? I think there's a chance that we'll have progress on questions like that.
Do you think there's any understanding we have that is at risk of being dismantled by... new or better observations. Quantum mechanics, many people are quite comfortable, been around for a hundred years and it works.
But there are unresolved questions that many physicists don't really spend much time thinking about. And I can imagine that in the coming years, those problems, and they are real, I assure you they are real problems, may flare up, causing us to rethink the foundations of quantum theory. String theory is an attempt to fill in the gap, to try to put... general relativity and quantum mechanics together. And at least on paper, and we've known this now for many decades, it succeeds in putting general relativity and quantum mechanics together.
There's a lot of progress that's happened. And now we realize that a lot of the qualities of string theory have a dual description, a sort of mirror image version in which point particles do play a role in that description. But we're beginning to learn.
That string theory is one language for describing this unification, but there are other languages and languages sometimes do invoke point particles. So it's all kind of coming together in a beautiful tapestry, and we're still trying to, you know, figure it all out. What does the subatomic world look like? This really challenges our intuition, because our brains and our eyes evolved for the purpose of survival.
And to survive, we just need to be able to see on the scales of everyday life. So when you're talking about an atom, we like to use language that resonates. We imagine we have an electron cloud.
It's a probability cloud. Now, what does that mean in terms of visualization? Mathematically, I know what it means.
There are a lot of locations where the electron might be found. But to actually see it, literally, I need to bounce some light off of it. When I bounce light off of it, Quantum mechanics tells me I have affected the thing that I'm observing.
So I'm not seeing the probability cloud any longer. I'm simply seeing the electron at whatever location the photon hit it. We don't feel the light bouncing off of us, but an electron feels the light bouncing off of it.
And that interaction affects how it then subsequently looks. And so it's really hard to give an everyday visualization that's at all accurate for what things are like in a realm. that we don't inhabit directly. I wish we could.