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Is time travel possible?

I've been very interested in astronomy, especially with time. I just wanted to know if humans will ever be able to figure out time travel as well as faster then light travel. (Einstein said nothing can accelerate to speed of light, so how do we do it?)

Literature is full of stories about time travel, and people have imagined countless machines and devices to achieve it. However, most of these rely more on magic than on physics! When you ask me if time travel is possible, I can think of one way to do it based on the laws of physics. And yet, it would only allow one to get to the future, not by getting in a time machine and immediately jumping in the future, but by traveling in a space ship or some other vehicle that could travel at very great speeds.

In order to travel through time, one must travel at the speed of light, or at least at speeds very close to the speed of light. The problem is, as you mention, that it is not possible to accelerate something up to the speed of light. This comes from the theory of special relativity. In that theory, Einstein has shown that as something accelerates and travels at great speeds its mass increases. And the larger the mass of the object, the harder it is to give it a push to make it accelerate some more. So when the speed of the object gets really close to the speed of light, its mass becomes almost infinite making it impossible to actually give it the speed of light (or speeds faster than the speed of light).

But you don't need to travel exactly at the speed of light to "travel to the future". This also comes from Einstein's special relativity. When things travel at speeds close to the speed of light, time slows down. For example, if you were travelling for 10 years in a spaceship that could go at 95% the speed of light then 32 years would go by for the people that stayed on Earth. So in that sense you could say that you have traveled in the future. However we do not have the means to accelerate our space shuttles to speeds even close to that. The space shuttle travels at about 17,500 miles per hour which is 40,000 times slower than the speed of light. At that speed, an astronaut would have to travel a billion years in his space ship in order to jump one year in the future!

This means that time travel will be impossible until we develop some means of accelerating space ships at speeds very close to the speed of light.

December 2002, Amelie Saintonge (more by Amelie Saintonge) (Like this Answer)

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