Welcome to kiss myths and mysteries. I'm your host Kit Crumb. I'm continuing my investigation into the concepts of time travel yesterday. I mentioned three resources. Final countdown. A movie where you can watch. Martin Sheet explained the grandfather paradox of time to Kirk Douglas. Kind of a fun movie came out in the eighties and Christopher Reeves in his movie somewhere in time takes it to a mental intellectual level kind of away from what physicists would like to think when they think of time travel and of course. There's the book by She. Wells time travel Idea that you could just go to the future. Go to the pass by pulling a switch on a machine. One of the things that happened yesterday was I mentioned the grandfather paradox of time and I gave you a place to watch Martin. She talk about this. I got a lot of emails saying why. Don't you explain it? So here goes this kind of scattered a little bit but give you an idea. Besides a physical problem time travel may also come with some unique situations a classic example. Is the grandfather paradox. Which time travel? It goes back and kills his parents or his grandfather. The major plot line terminator movies interferes in their relationship. Now think back to the future so that he has never born or as life is forever altered. That's back to future if that were to happen. Some physicists say you would not be born in one parallel universe but still born and another others say that the photons it makeup light prefer self consistency and time lies which would interfere with your evil suicidal plan. Some scientists disagree with the options mentioned above. And say time travel is impossible no matter what. Your method. The faster than light. One in particular drew derision from American Museum of Natural History astrophysicist Charles Lou that simply mathematically doesn't work you said also humans may not be able to withstand time travel at all. And that's what we're lucky nap today. Several theories time travel traveling. Nearly the speed of light would be necessary and take some kind of centrifuge. But that would be lethal. So let's go back to the beginning and say what is time while most people think of time as a constant physicist Albert Einstein showed a time is an illusion it is relative it can vary for different observers depending on your speed through space to Einstein. Time is the fourth dimension space is described as a three dimensional. Orito and we know that we have up and down forward and back left and right those who are dimensions but he talks about a fourth dimension which provides traveler with coordinates such as length width and height showing location. And then that fourth dimension provides another coordinate or direction although conventionally it only moves forward. Einstein's theory of special relativity says time slows down or speeds up depending on how fast you move relative to something else approaching the speed of light. A person inside a spaceship would age much slower than his twin at home. Also under Einstein's theory of general relativity gravity can ban time picture a four dimensional fabric. Call Space Time. When anything that has mass sits on that piece of fabric it causes a dimple or bending of space time. Let's stop and talk about this fourth dimension for a moment if you look into a Koi pond and you see the fish and they have is on either side of their head they are two dimensional creature stay left and right and they can move forward and back. There is nothing about them. There is no third dimension so if I grabbed one of the Koi and lifted about of a pond that would introduce the Koi to a third dimension so what Einstein in his speaking of this fourth dimension or call what he calls Space Time. That is something that is above us. It is literally another dimension so there you have the idea of Space Time. What that is that is that fourth dimension that's above us like the third dimension this above a Koi pond for example objects move on a curved path in that curvature of space is what we know as gravity both general and special relativity theories have been proven with GPS Satellite Technology. That has very accurate time. Pieces on board the effects of gravity as well as satellites increase speed above the earth relative to observers on the ground. Make at the UN adjustable clocks gained thirty eight microseconds a day in a sense. This effect called time. Dilation means astronauts are time travelers as they returned to earth very very slightly younger than they're identical twins that remain on the planet. One possibility could be to go faster than light which travels at one hundred and eighty six thousand two hundred and eighty two miles per second. That would be a vacuum Einstein's equations though show that an object at the speed of light would have both infinite mass and a zero of length. Go figure that s beyond me.