Saturday, July 9, 2011

Strangest Facts of Physics: Time Travel to the Future

When I was a child and was only starting to learn physics, one thing for me was stranger than anything else. You might guess it was the strangeness of quantum mechanic. But actually (even though quantum mechanics is very very strange and fascinating) the thing that really caught my attention was time travel.

Time travel is one of the most popular subjects of science fiction. Starting with Star Trek ending with newer shows like Lost most of the sci-fi shows have a fare share of time travel. But have you ever wondered if time travel is possible? Well the answer is yes! And that is our strange fact of today.

First let's look at time travel to the future. Even though Einstein's special theory of relativity is a part of high school course, not many people know that time travel to the future is actually a scientifically proven fact. It's not only proven, it's a big part of communication technology, as even GPS services wouldn't work without the precise calculations from the special and general theories of relativity. But what does this have to do with time travel?

Einstein back in 1905, when his special theory of relativity was created, showed, that time runs slower for fast moving bodies. To get a grasp of how this works, let's check out this mechanism called photon clock. It consists of two mirrors with a photon (particle of light) trapped between them. Every time the photon hits the mirror a unit of time passes.


When the clock is not moving, the photon just bounces up and down vertically. However, if the clock is moving, as you can see in the image, the photon needs to go diagonally from the upper mirror to the lower one and vice versa. It's clear that when the clock is moving, the photon has to travel a greater distance from one mirror to another. In other words, time passes slower for a moving photon clock. But the interesting thing is that this is true not only from photon clocks, but for any moving objects, as Einstein showed in his theories. Even the photons in the atoms of our bodies must travel a longer distance between the nuclei and electrons when our bodies are moving.

This simply means that the faster some object moves, the slower time runs for it. This gives rise to the famous twin paradox. It goes like this. Let's say there are two twins. One of them decides that life on Earth is boring, so he jumps on a fast rocket and flies away for let us say 50 years at a speed of 75% of light speed. Then after 50 years, he get's back to Earth, and is amazed, as his twin brother appears to be 25 years older than him.What happened was that time ran slower for the brother, who was in the rocket, which basically made him travel to the future, as time on Earth was running faster.

A video about Twin Paradox:

You might be wondering does this have any proof? The answer is yes. Two super precise atomic clocks measured time, while one of them was in a plane flying around the world, whereas the other clock was stationary on the ground. The difference in the clocks, when the plane completed its journey, was a very very small (nanoseconds), but it agreed with Einstein's theories.

So time travel to the future is really possible, though our current technology is not advanced enough to make use of it. Rockets, travelling at almost the speed of light would be required to travel to actually travel to the future. Also going back from the fancy future would be much more difficult (some believe even impossible), but more about that next time.

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For more about time travel check out these books:


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