The Universe - Time Travel

Today on Far Future Horizons we present another episode of the acclaimed documentary series “The Universe”. This instalment of the series looks at the possibility of time travel and how it could one day become a reality.

The twin paradox asks why the traveling twin ages less than the Earth-bound twin. That is the prediction we obtain if we consider the Earth-bound twin’s frame. In the astronaut’s frame, however, the Earth is moving and time runs slower there. Who is correct?

Einstein's theories of special and general relativity both allow for the possibility of travelling through time. Travelling into the far distant future is a definite certainty within special relativity. All you need to do is travel very fast at speeds that are a significant fraction of light speed and time slows down for you. This relativistic effect is known as time dilation.

This effect is a well established fact and has already been proven experimentally here on Earth and in space. 

One only has to look at the behaviour of a short lived subatomic particle known the muon. A muon only has a lifetime measured in microseconds (μs).

If one compares the lifetimes of two muons at different speeds we see some very surprising results. In the laboratory, slow muons are produced, and in the atmosphere very fast moving muons are made when cosmic rays bombard atoms in the tenuous upper atmosphere that exists on the very fridges of outer space above the Earth’s surface.

A muon’s lifetime at rest in the laboratory is 2.22 μs, the lifetime of a cosmic ray produced muon travelling at ninety-eight percent of the speed of light is about five times longer, in perfect agreement with calculations made using the theory of special relativity.

In this experiment the "clock" is the time taken by processes leading to muon decay, and these processes take place in the moving muon at its own "clock rate", which is much slower than the laboratory clock.

Time dilation would make it possible for passengers in a fast moving space vehicle to travel further into the future while aging very little; since their great speed slows down the rate of passage of on-board their spaceship.

Thus the very first astronauts who venture forth to the stars will also be the first bona fide time travellers.

Yet, even more bizarre would be the mind-boggling paradoxes that would arise if travelling to the past ever became possible.

The Universe is available on DVD from Amazon.com and the History Channel’s online store.

The Universe Time Travel

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