# What will happen if we travel faster than the speed of light?

I know this is not practically possible because it requires infinite energy, but theoretically if the speed of light exceeded, the time will turn back, so what would happen to the traveler? I mean, will he see himself when he was young and he can meet himself as an older person or will he be young himself and also can meet himself? or he will be the same person he was back then?

### 10 Answers

- 1 month ago
If you traveled faster the speed of light, you would experience time dilation, which means time will run slowly

You would also experience visual consequences called aberration refers to your whole field of view would shrink down.

In addition, you would notice an extreme Doppler effect, which would cause light waves from stars in front of you to crowd together, making the objects appear blue. Light waves from stars behind you would spread apart and appear red. The faster you go, the more extreme this phenomenon becomes until all visible light from stars in front of the spacecraft and stars to the rear become completely shifted out of the known visible spectrum (the colors humans can see). When these stars move out of your perceptible wavelength, they simply appear to fade to black or vanish against the background.

- cosmoLv 71 month ago
If you can travel faster than light, you can also travel backwards in time by travelling outside your original lightcone and then accelerating the right way.

- VamanLv 71 month ago
Nothing. If you are moving with a constant velocity, then it is as good as sitting in your house. All problems start during the change in velocity.

- Andrew SmithLv 71 month ago
Once you start imagining what is possible if the impossible was possible then you are in the realm of absolute fantasy. But if you had an infinitely powerful telescope then you would indeed see the past. In fact if you continued you would see everything happening in reverse AND you would see it in front of you not behind you.

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- formengLv 61 month ago
Unless we want to overthrow Einstein, we won't be travelling through space faster than the speed of light. I would be remiss if I didn't say that space can expand faster than the speed of light, so far as is known. So, if you can figure out some way to create a bubble of space and make it expand faster than the speed of light and move through space, then maybe you can travel through space faster than the speed of light. On the other hand, maybe not. lol

- 1 month ago
It is an intriguing proposal. Assuming the 'hand of god' reaches into the universe and changes the description of an object, such that it was moving fast than light (without accelerating that that point), it does raise questions regarding it's impact on gravity, time and so on.

- Jeffrey KLv 61 month ago
First, it is impossible to go faster than light.

Now, if you found some way to do it, you would not automatically go back in time. But if went faster than light from point A to B, then move into a frame of reference that is moving near the speed of light away from A and travel back to A at a speed faster than light relative to the new frame of reference, you could arrive back at A before you left. You would meet your previous self. And you could create all kinds of paradoxes. But remember what I said at first. Superluminal speed is impossible.

- PhilomelLv 71 month ago
I don't know Ive never done that. No one else knows either because they haven't either. They can only guess what would happen. You can guess what would happen and no one can argue with it. Be brave and theorize.

- UserLv 71 month ago
1) What will happen if we travel faster than the speed of light?

We don't know.

2) I know this is not practically possible because it requires infinite energy, but theoretically if the speed of light exceeded, the time will turn back

No.

If we mathematically present how quickly time passes on a graph

- to the right, time passes more quickly for the object in motion

- the the left, time passes more slowly for the object in motion

- the origin of the graph is at x=zero

Then (according to Einstein's theory)

as the object increases speed

time for the speeding object passes more and more slowly (relative to the frame of reference)

until at the speed of light time stops (how quickly time passes = zero).

What happens

according to these same equations

when you exceed the speed of light?

You, like many people, assume that the progress continues to the left

and that as speed increases past the speed of light

time passes even MORE slowly, passing at a NEGATIVE rate, so that the object moves backward in time

but

***the equations indicate something quite different***.

On our graph

as speed increases above the speed of light

we do not (as you assume) move farther and farther left along the negative X axis

but, rather

***along the Y axis*** (where x STILL = 0).

This state is undefined. We don't know WHAT it is or what it means

or if it is possible to achieve it.

Explanation: the equations, as one approaches the speed of light, produce a smaller and smaller number "rate that time passes", but that is the result of a ratio of a square root

rate time passes for moving object / rate time passes for frame of reference =

SQRT(1 - velocity-squared/c-squared)

at velocity = zero

the ratio of rate of time passes = 1

i.e. rate of time passing for the object is the same as rate of time passes for frame of reference

at velocity = 0.5c

the ratio of rate of time passes = SQRT(0.75) = 0.86

i.e. the rate of time passing for the object is 0.86 the rate of time passing in the frame of reference

as speed increases, ratio decreases

at velocity = c we get a ratio of zero. the rate of time passing for the object = 0.

at velocity = 2c we get a ratio = SQRT(-3)

!!!

the square root of a negative number is not a negative number

but

rather

***an imaginary number***

ratio = 1.7i

(which is by convention charted along the Y axis)

as velocity increases

example: velocity = 3c

we get a larger ratio = SQRT(-8) = 2.8i

but still along the Y axis, X is still equal to zero!!!

As I said: we simply don't know what that means.

- billrussell42Lv 71 month ago
as it is impossible to reach the speed of light, let alone exceed it, any comments on that are purely science fiction and have no basis in science. Like asking what does negative mass look like.

"if the speed of light exceeded, the time will turn back" that is false, there is no reason for that to be true.