# Back in time by going faster than light?

1. Aug 21, 2004

### Zeteg

Well, I guess I should introduce myself first. I'm 15, and in Canada. It's pretty hard to find answers to questions that relate to physics at this age, over the summer, so I've turned here. =)

Okay, I've been interested in physics for quite some time, and I've always wondered... I've been given the impression that when anything should surpass the speed in which light travels, the certain object will travel negatively in time?

While I understand the argument of why nothing can travel faster than that of light, I fail to understand how travelling faster than it, would allow one to travel back in time.

If anyone can explain this to me, I'd be quite glad =)

2. Aug 21, 2004

### canopus

Hi! I know the only way traveling back in time by using tachyons. However this idea againts the principle of causality. You see the death of a star before it borns.

3. Aug 21, 2004

### robphy

4. Aug 21, 2004

### Zeteg

So pretty much, we won't travel back in time, and it's all a myth? Rather, we will sense what was back in time, right? =)

5. Aug 22, 2004

### aekanshchumber

I think if you are saying that one can go backin time by traveling fasterthan light is possible then you are wrong . Traveling faster than light is firstly not possible and second reason is by the S.T.Relativity when speed higher than light is reached the time will be the imaginary not negative, b'coz acording to relation
T=t/{1 - (v/c)^2}^1/2
T will be imaginary as it is going to be underroot of a negative number.

6. Aug 22, 2004

### Zeteg

Ah okay, thanks =)
Yeah, it's that I heard that you would go back in time, but I failed to find any reason. That's why I asked =) Thanks.

7. Aug 23, 2004

### ArmoSkater87

I've heard that many times too, but never understud why either. I think its a bunch of crap when they say that. I think the only reason they say you will "go back in time" is because the the maximum speed at which information can be transfered is the speed of light. Going faster would mean you can tell people something that hasnt "happened" yet. For example, lets say you are next to the sun and you see it explode, then you go faster than light to earth and tell people, "oh i went back in time and saw the sun explode". Since the soonest the people can see the explosion is when the light gets there, in a sense you "went back in time" and saw it before it happened. It is similar when people say that you "look back in time" when looking at the stars, because you see them as they were when the light left them, which depending on the star is either several to millions of years younger than it actually is. And to you the star hasnt exploded, even if it actually has, but you wont know that until the light gets here.

Last edited: Aug 23, 2004