# Is time in the universe constant?

1. Nov 10, 2005

### cosmic time

I'm thinking of a way to defend my authroity against a peer who has threaten to take me down in a debate (LOL).
Im Im thinking, say your moving close at the speed of sound, and then you suddenly stop, time around you is supposed to get slower, and potentially go back in time. How would it seem to be an observer? WOuld you seen slower than you actually are moving? Would everything int he universe get slower to keep up with you speed? That would form a paradox, just about everything int he universe is moving at different speeds, how would this be possible?

My question is would it be possible to have 2 different times in two different places? If not... then say after this 'trip' the two people (observer and the runner) meets up, would the runner meet the observer in the past? This concept, i jsut cant understand.

2. Nov 10, 2005

### Staff: Mentor

Most of the first half of your post doesn't make a whole lot of sense, but...
Certainly. Time is observer dependant.
Two people who start out next to each other with synchronized clocks may or may not have synchronized clocks at the end of their "trip".

3. Nov 11, 2005

### jackle

Sounds like you are thinking of the speed of light.

Sounds like you are recalling something someone told you about travelling faster than light (just not very well).

I understand relativity by thinking of two types of time dilation. One that is symmetrical, caused by relative motion where you see each other's clocks go slower than your own. One that is asymmetrical in that you can both agree on who is running slow, caused by gravity. Your own clocks never seem odd until you compare it to someone elses, going at a different speed.

When a physicist says "clock" in relativity, it normally means the underlying time-system rather than just a mechanical device prone to error.

Through the behaviour as described by the theories of relativity.

According to relativity, if they both travel at sub-light speeds there is no time travel going on. Aging at different speeds is allowed though.

4. Nov 12, 2005

### .:JimmY:.

apparently you are confussing time with a bus ride, when a bus stops suddenly every thing falls forward. well it is way complicated then that