# How long would it take to travel to another galaxy?

Oct 13, 2016

It depends...

#### Explanation:

There are some small satellite galaxies of the Milky Way galaxy, but let's consider our largest neighbour in the Local Group, namely the Andromeda Galaxy.

This is situated approximately $2.5$ million light years away.

That means that from the perspective of the people who stay at home, a round trip would take at least $5$ million years.

Note however, that the traveller(s) could experience significantly less time, if they travel with sufficient speed.

For example, if they used a spacecraft that accelerated constantly with an acceleration of $1$g (i.e. $9.8 m {s}^{- 2}$) for about $14$ years (ship time), then decelerated at $1$g for about $14$ years, that would be sufficient to travel from our galaxy to the Andromeda Galaxy.

Returning home the same way, the traveller(s) would experience another $28$ years of time, but arrive home to find that $5$ million years had passed.