How is faster-than-light travel time travel? Regardless of energy concerns, why is it impossible?

Answer 1

The reason why it is time travel is because just because of Einstein's equations (in special relativity). If you have a starting destination and time and travel to a different destination faster than the speed of light, and plug this information into his equations, you end up finding that the time you reach your destination is before the time you left.

This is *assumed* impossible because it violates causality (the principle that a cause must always go before an effect). This is only an assumption though, many particles do actually appear to travel backwards through time.

Answer 2

Assuming you have a damn good telescope :), if you travel faster than the speed of light you overtake the photons reflected from objects. So if you keep focussed on an object (say your house) and speed off into space at a speed greater than that of light, provided you can still see your house well enough (hence the need for a telescope, lol!) you will be observing photons that were reflected from your house before you left, hence you will see the house at some time in the past.

This is the idea behind looking at stars, etc. When you look at the sun, you are seeing what the sun looked like eight minutes previously.

As for why it's impossible...regardless of energy concerns, um...that is the reason; energy concerns. The only things that can travel at the speed of light is pure energy. As an object approaches the speed of light it will convert into a purely energetic particle(s).

Answer 3

Many explained the first part.
Simply if you travel faster then light you will see the light of the past that has not reached you so you are watching things which happened earlier. You are ahead of your time. But everything about time travel is rubbish if you cannot reach the speed of light.

Physic's laws don't allow us to travel faster then light. Because as you approach the speed of light your mass increases, so you require More energy to accelerate. And as you reach the exact speed of light your mass becomes infinite which is impossible, furthermore if you travel faster than speed of light then your mass becomes negative, which again is impossible. So here you go, we cannot travel at the speed of light let alone faster then it.

Einstein's theory of relativity tell us this.

Answer 4

There are a lot of silly answers here explaining why going faster than light amounts to time travel. If you obtain an introductory modern physics textbook, it will very likely explain it thoroughly.

For a fundamental understanding, you just have to accept that 2 events that happen at the same time to one person dont (in general) happen at the same time to another person. This 'relativity of simultaneity' means that two lightning bolts that strike at the same time in my reference frame, happen with a pause between them in your reference frame if you're moving close to light speed relative to me. However, as long as you're not traveling faster than c (the speed of light), an even that CAUSES another event will always precede it, as well it should. If you start going faster than c though, then effects can come before causes. Thus if event A is you leaving earth, and event B is you arriving, by moving faster than C, you could make your arrival precede your departure. This is generally taken as nonsense to real physicists who have better things to do than answer questions on yahoo. Beyond the energy concern, acceleration to c would be problematic because an an arbitrarily long amount of time would lapse for the rest of the universe while you accelerated. So by the time you "got" to c, an infinite amount would have lapsed (not for you, but for everyone else), which would suck.

Answer 5

As a body approaches the speed of light its mass gets greater and greater and its dimensions shrink. You simply cannot get enough energy to accelerate the mass to c.

PS That's relativity in a nut shell

Answer 6

We can't just throw away the kingpin of our universe's physics and then discuss anything rationally. However, on a quantum level just seeing this query brings me such ennui that I will now curl up inside a sub-Planck length Calabi-Yau dimension and ponder it for a few millenea. Be back in just a picosecond. I'm fading, I'm fading..........

Answer 7

According to relativity it's not actually impossible, just very improbbable (due to the energy stuff you mentioned).

Answer 8

its because the amount of energy you need at the point of light speed becomes infinite...simple as that

although check out this weeks new scientist for matter that reaches its destination BEFORE it leaves!!

Answer 9

there would be a server probability that you would not get to the target destination at the time you initially expected. this and the object travelling would be ripped apart dispute what the fantasy films say.

Answer 10

It is not impossible.
The speed of light can and has been broken by using two casimer created wormholes. One is accelerated near the speed of light and one parked.