# Our past is not our past?

1. Jun 17, 2009

### aaryan0077

Our past is not our past? Or Does past changes when we travel fast enogh?

We have a light cone
http://img7.imageshack.us/img7/6463/lightcone3.jpg [Broken]
Vertical and horizontal axis representing time and space respectively.
Here L1, L2 & L3 represent path allowed for massive bodies, light and path not allowed respectively.
I know we can't get to speed of light or more ( atleast for now, unless we don't have any sort of startrek or skynet technology :tongue2: ) but we know that when we get closer and closer to c, time starts to dilates (& I know there are many threads on time dilation here, but my question is different) and we are "said to" (whatever this means) travel into future (remember twin paradox) and if (by any means) we cross the speed limit of c we'll travel back into the past, atleast that is what is supposed to happen.
But any object (here WE) faster than light will follow L3 (or any path between L2 and horizontal axis) and so we'll get to else where region and not our past, contrary to what is supposed that we'll travel to past.
So will that elsewhere be our past if we travelled like this?
Or is our own past not our "own" as we accept it to be?

Last edited by a moderator: May 4, 2017
2. Jun 17, 2009

### tiny-tim

Hi aaryan0077!
No, that's mathematical rubbish.

The time-dilation formula is √(1 - v2/c2) …

if the formula was (1 - v2/c2),

then you'd be right … for v > c, time dilation would be negative, and a traveller would go back into the past

but it isn't, and for v > c, the correct time-dilation formula becomes imaginary, not negative …

I suppose you could say that means that a traveller goes into imaginary time!