# Relative time space travel

1. Dec 9, 2011

### disneygirl828

1. The problem statement, all variables and given/known data
I have a twin brother, and we're 30 years old. If i travel for three years at 2.55 X 10^8m/s (0.85c) while my brother is a rest on Earth, how much older than me will my brother be upon my return?

2. Relevant equations

t=To/√1-v^2/c^2

3. Try to work out
To=3
T=?
V= 2.55 X 10^8 m/s
C= (.85c) 2.55 X 10^8 m/s
T= 3/ (all of this under a square root sign -->)1-(2.55 x 10^8)^2/(2.55 x 10^8)^2
t=3/0
*i get stuck here because you cant have a zero in the denominator*

Last edited: Dec 9, 2011
2. Dec 9, 2011

### BruceW

Hmm, you've done:
$$T= \frac{3}{\sqrt{1- \frac{v^2}{v^2}}}$$
I'm guessing you've accidentally done this?

3. Dec 9, 2011

### disneygirl828

Yes i used that equation, should I have used something different? If so what?

4. Dec 9, 2011

### BruceW

This was the right one, i.e. :
$$\frac{3}{\sqrt{1- \frac{v^2}{c^2}}}$$
c is the speed of light, but you used v instead, which is why the denominator came out as zero.

Last edited: Dec 9, 2011
5. Dec 9, 2011

### BetoG93

C = 3 x 10^8 m/s.
Remember this: the difference in ages will be the difference in the proper time and dilated time.