# What does the speed of light have to do with time travel?

Wow, how long have you got? Are you referring to Time Dilation or good old HG Wells "time machine" type stuff?

Time dilation, where time runs at a different speed for a body that is accelerating, is a proven (experimentally) effect. If you accelerate to close to the speed of light, you will "age" more slowly relative to a stationary object. Of course you have to consider who is actually moving, since the acceleration could be considered to be happening to either body (if you are standing on the accelerating body the stationary body will appear to be accelerating away from you). If you have a clock in both places, it will appear to be running slowly to an observer on the other body. Gravity can also cause time dilation - but that is not what the question is about.

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Yo Kass commented
Interesting explanation. So in an example where a vehicle is speeding away from space at close to the speed of light, time on that object will appear to be moving slower to observers. Is the same true for someone on the vehicle looking back at the destination planet? Or am I just getting all muddled up?
Ray Dart commented
Yes, and no you are not - even Einstein had problems explaining this (although presumably not in understanding it.) I like this quotation:
“The total number of people who understand relativistic time, even after eighty years since the advent of special relativity, is still much smaller than the number of people who believe in horoscopes.”

Also note that it is technically possible to move "forward" in time the closer you get to the speed of light (as a result of relativistic time dilation as above).

However, you cannot go "back" in time.

There is, however, a way around this:

If two wormhole links are built - one is kept stationery at one location, while a spaceship carries another worm hole travelling close to the speed of light, and returns to the original location, in theory by the time it returns, due to relativistic time dilation, a link to a time from the point the spaceship left will be linked to the new "future" time of the travelling wormhole.

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