# Homework Help: Relativity : Traveling to Andromeda galaxy

1. Jan 20, 2007

### Delzac

1. The problem statement, all variables and given/known data
An astronaut wishes to visit the Andromeda galaxy 2 million light years from Earth. He wishes the one way trip to take him 30 years (ie in the frame of reference of the spaceship). Assuming that his speed is constant, how fast must he travel?

2. Relevant equations
$$L = L_0/\gamma$$
$$\Delta T = \gamma \Delta T_0$$

3. The attempt at a solution
I know that by increasing velocity of the spacecraft, you can effectively length contract the distance between earth and the galaxy, however, i do not know how i should equate the equations. Any help will be greatly appreciated.

2. Jan 20, 2007

### Delzac

Ermm....any help?