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According to this video, faster than light travel is analogous to time travel. Does this mean that if I could instantly teleport 1 light year away, and then sent a laser pulse to my friend, my friend would interpret the event as happening in the past?

Would it take him a year to see the pulse? Or would he see it immediately and interpret that the event occurred 1 year ago? The video I mentioned seems to suggest that my friend would interpret the event as happening in the past, I wanted to confirm.

What do they mean when they say that faster than light travel analogous to time travel?

https://www.youtube.com/watch?v=HUMGc8hEkpc

Qmechanic
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Marc DiNino
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1 Answers1

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It depends what you mean by "instantly."

A working definition of teleporting instantly is that your departure and arrival are simultaneous. But simultaneity is relative in special relativity, so what is instantaneous to one observer is not to another. To all other observers, you would disappear and then reappear in the past or the future.

The answer to when the light reaches your friend depends on whose definition of simultaneity you use. If you use your friend's, then the light will show up one year after you left. But using another definition of simultaneity it could instead appear immediately or more than a year in the future.

Emilio Pisanty
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Chris
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