If you can reach 99.9999999999995% of the speed of light, the time it takes to get to Andromeda is 2.5 years, 5 years round trip.
The problem is that if you go back, you will reach the Earth 5 million years later.
If you can reach 99.9999999999995% of the speed of light, the time it takes to get to Andromeda is 2.5 years, 5 years round trip.
The problem is that if you go back, you will reach the Earth 5 million years later.