Einstein, Kip Thorne, Professor discussed on Exploration
Now, I'd like to introduce our very special guest today. Once again, we have with us professor j Richard Gott the third he's a professor at Princeton University. And he's the author of a book called time travel in Einstein's universe. The physical possibilities of travel through time. Now, just remember that we're not talking about some inventor in a laboratory in his basement creating a time machine by which you can race certain rather embarrassing events in your history. We are in fact, talking about hard physics. We're talking about perhaps one day a civilization much more advanced than ours are perhaps maybe even are descendants thousands of years from now may have the ability to manipulate the energy of a star in which case they may be able to create a time machine capable of changing the past. And so the question is is time. Travel possible. Given the fact that there are all sorts of horrible paradoxes, you can get if you go backwards in time, for example, and shoot your parents before you're born. So once again today, our guest is professor j Richard Gott third professor at Princeton University. And we are talking about time machines and time travel. The first question for you. Professor God is how did you first get interested in physics? Well, I got interested in the strana me when I was about eight years old I belong to a stargazer group that was organized by junior astronomical society. And so I did telescope and as trying to me was a hobby of mine and in high school, and when I became interested in physics in high school and so forth. I I later decided to take my physics and work on astrophysics because that had always been a hobby of particular interest to me, and was there anything about the remains of the stars of anything about for example, looking for intelligent life in outer space or are wondering where the universe came from was there anything specific about astronomy that fascinated you? Well, I was particularly interested in the big bang theory. At that time. This is a bet before Penzance and Wilson discovered the cosmic microwave background radiation. So I was always a fan of the big bang theory versus the as opposed to the steady state theory. And I understand today your -ffiliated with the Intel science talent search or formerly known as the Westinghouse science talent search so tell us a little bit about your experience judging high school kids well for many years, I was the judge had chairman of the judges for the first Westinghouse. And then it's now sponsored by Intel Intel talent search in. This is a wonderful fives competition, that's the oldest and most prestigious competition for a high school didn't since signs in the country and five of its winters. Have gone on to win Nobel prizes. So it's a wonderful contest and ask you to do a piece of real research into Mitchell research, just like you would write a research paper and so forth. So unlike a test of some sort it's really you just try research, and we look at your research. So it's it's kind of like if you're a baseball camp, you know, you could you could test people out, but I've seen how fast they ran down to first base. That would give you some idea of how they might play baseball. But baseball scout would tell you that it's really scouting for the major leagues you really wanna see people actually play baseball. So this gives Dinsdale chance to do real research projects, which are fine and many people that enter this contest, they fall in love with doing research and for the rest of their lives and many of the winners of this contest of gone onto wonderful. Careers in science. So I would encourage people to apply for forty. Winter's come to Washington each year, and they give out very large scholar college scholarships. And it's a very exciting thing cannot let's talk about time travel in particular. There's a movie hitting the silver screen right now called Terminator three where killer robots from the future come back to harass in the past. So which started your romance with time machines because in the area of physics most physicists tend to at least in the old days scoff at the whole notion of going backwards in time. Well, I got interested in time travel by exploring some solutions to Anton equation. Einstein developed his theory of general relativity, which is his theory of curved based time to explain gravity, and we take this theory, very seriously. Because when he when he finally solve the equations for this nineteen fifteen they made prediction predictions about light bending, or is it would pass near the sign, and these are checked experimentally, and Einstein was found to be right and Nitin was found to be wrong. So since then people have been interested in exploring exact solutions to and fans equations, and you've heard of probably the most famous one is the black hole solution. That's the exact solution to an equation. So we take black hole seriously. Even though they're quite extraordinary objects because they do solve and Dan's equations of gravity, so hours in I got interested in cosmic strings. These are theoretical object. That are dance threads of energy leftover after the big bang that are predicted in about half the theories of unified particle physics and early universe. We we haven't found them yet. But we are searching for them. And I found an exact solution for a one cosmic Strang what the geometry around one cosmic string would look like and William Hiscock found the same solution independently of Maine to were given joint credit for this pollution dance dance equation. And then later I investigated to moving cosmic strings what an exact solution would look like if two strings were to pass each other. And I did found an exact solution for that JAMA tree. And it turned out that if the strings were moving fast enough, but still slower than the speed of light that this was a solution. That would allow you to circle around the cosmic strings and arrived back home. Before you started. So it would allow time travel to the past and there've been a number of general relativity solutions like this. The first one was found famous mathematician, Kurt girdle in nineteen forty nine rotating universe. But we don't live in that kind of universe. But it's an interesting solution to the equation that allows time travel to the past. And if there's one pollution like that there could be others, and then Kip Thorne and his associates found wormhole solutions that allowed time travel to the past. So it's extremely interesting that these equations of and fans of general relativity themselves, and this is our best theory of gravity at the time. Famed allows pollutions that allow time travel to the past. So I got interested in it just from trying to understand and stands equations with objects that we were interested in. Okay, now, let's talk about the move. Everyone likes the movies and people have seen a lot of movies where we have black holes that are rotating very rapidly. Right. And according to mathematician, ROY Carr in nineteen sixty three he did find it solution of Einstein's equations where if you pass through the ring not a point. But a ring spinning very rapidly you'd wind up on a parallel universe, perhaps even a distant point in time. So could you elaborate about what happens if you haven't forbid fall through a black hole and make it quote to the other side, unquote? Well, this was an unperturbed Blackhall is the solution to and fans equations, and this is one that's left alone complete lane, you ignore the effect of hawking radiation, which we can mention later, but this first solution for a rotating black holes show that if you traveled inside the black hole instead of a singular point in the center, you would find as. You said a rings thing you Larry if you pass through the ring, you could navigate your spaceship in such a way that you could travel back in time. And then after leaving this region, you could go and pop out into another universe sorta like getting on an elevator store and going up to the first going from the first Florida the second, and you could get out on the second floor universe than later. You could go out and go up to the third floor university over, but there is no getting back to the first floor. Once you went in there rotating black hole. It was not possible to come back outside and brag to your friends about your ventures. But quite interestingly, there was a region of time travel that was trapped inside the rotating Blackhall incurs pollution. Okay. Now, let's say you go through the black hole and you're not crushed by gravity because it's gravity spread. Got a little bit throughout the ring. However, there are some naysayers who say, wait a minute. Let's not go so fast. And you mentioned that the black hole was not perturbed. So could you tell us a little bit about some of the naysayers who say that maybe you can't make it quite all the way through that black hole. Well, the trouble is that they when you pass inside the black hole and you pass into the region of time travel. If you're looking back outside you're watching the you're saying the history of the external universe is you're passing outside and in in Mr. car solution as you pass the end of the region of time travel. You would be able to see the entire future history of the universe pass before your eyes. Now, you might say, well, this is a good thing. Very interesting for historians. You get to see a whole future history of the universe in a finite amount of time. But the trouble is those photons coming in would be infinitely blue shifted and and. Become instead of visible so times, they would become ultraviolet than gamma Ray photon. So these could kill you. You have to pass them on your way into the region of time travel. Other effects need to be considered to like the fact that the black hole may evaporate. Would it be expected to evaporate from hawking radiation, which cuts off your view of the very late history of the universe? But also in other effects were quantum effects on the inside of the black hole. So the situation is that some people have explored this situation, Mr. berko for one Amos Ori, and they have found that that you traveling to the region of time travel, you you would probably pass this thing you Larry the the the curvature of FaceTime would would would become infinite. However, it takes a very brief amount of time for this to occur. So the singularity may be maybe weak in the sense that it that it may not tear your body completely apart and also quantum effects would be expected to knock out. Any 0's and the solution? So the trouble is that we don't really know exactly what happens to you. When you go inside a rotating black hole, and we we may need of quantum gravity to explain this. We know how gravity behaves on macroscopic ordinary scales. Einstein's theory gives us a wonderful and very well. Check theory of that. But we don't know how gravity behaves on microscopic scales. And to understand what would really happen going into a black hole. We may need to know that. Okay. Well, we have had on this radio show several people who work in superstring theory. Like, I do and look at these things. However, the theory is not very well developed yet. So let's ask a hypothetical question. Let's say you are an advanced civilization. Like we see in the movies an advanced civilization that can move planets and move stars. I mean, really powerful. Technology. We're having here now with that kind of technology. Do you think that someone could go through the ring to perhaps a parallel universe or perhaps in time or is just simply not known in terms of what we know about quantum gravity or do most people think Bah, humbug, you just can't do it. Well, I think that the if you're using my cosmic strings, what is duper civilization would try to do is find a loop of cosmic strings cosmic strings, either infinite they have no answer either their infinite if we found them either infinite or they come in loop things think of spaghetti or spaghetti O's. Find one of the spaghetti O's one of the loop manipulated. So that it collapses vow large factor, and you could you could arrange it with your massive spaceship flying around it. So that the two sides of the string would pass each other at the speed required to make a time. Machine. But I was able to show in that case. This would also be in grave danger of forming a black hole. In fact, it would likely form a black hole. So the region of time travel would likely be trapped inside just as we've talked about in that rotating black. Okay. So I think one thing they have sizes that. These are projects that really this. Loop would weigh half the mass of our own galaxy. So we're talking about projects that really only a super civilization could attempt. But as you say, we're interested in finding out whether a civilization with arbitrarily large powers, but but still operating under the laws of physics could do it. And I think probably until we really get a theory of quantum gravity. We can't say for sure whether they would succeed or not. Okay. Now, let's talk about the wormhole because on Star Trek, they simply zapped through wormholes to the other side of the galaxy. Now, if you had a black hole there is a problem there. And that is it's a one way ticket is basically a Roach motel you go in and you never check out again. A one way trip. However, these wormholes that we see on Star Trek are transversal, you go back and forth back and forth. It's like taking a Sunday drive right through a wormhole. So tell us a little bit about wormholes and whether or not they're practical. Well, the worm. Oh, God idea got started. When Carl Sagan who was writing this book contact with later became a famous movie he wanted to use a wormhole to get Jodie Foster from one part of the galaxy to another and so he called up his friend, Kip Thorne, instead, listen, I I'd like to get the physics right here. What about the physics the warm halt? So aren't in is associates investigated this and they found out that in order to transverse it back and forth. You had the prophet open with what we call negative, energy density stuff. This is stuff that weighs less than zero. In other words, you'd have to add mass to this to get back to zero it does it weighs less than zero. Well, that's very strange stuff. But you might say, well, that's strange. You wouldn't expect to find that? But occurs we do know a quantum mechanical sacked the Casimir. Effect which is one where if you take two parallel metal can conducting plates, and you put them very close together the quantum vacuum state in between the two plates, actually acquires a negative energy density weighs less than zero. So Kempthorne was proposing and and and and somewhere effects occur in and connected with hawking radiation and black holes and so forth. So we know of quantum effects that can induce negative energy density state. So what kept soaring proposed to do was to cover the mouth of each wormhole with a conducting plate and put them close to each other in the wormhole tunnel tend to the man is ten centimeters apart. So they introduced a large negative energy density..