Travel to the Andromeda Galaxy

In Physics today, Bickers lectured on Einstein’s Theory of Relativity. He ended class with this thought. Suppose you wanted to visit the Andromeda galaxy, and let’s say it’s 20 million light years away. You would say, no way, it’s impossible. Anything that has mass must always move at a speed less than that of the speed of light. That’s true, but the distance of 20 million light years is from the perspective of Earth.

(not drawn to scale)

When you travel at a speed near that of the speed of light, the distance gets shorter. And it can get infinitely short if you get infinitely closer to the speed of light (c). This is based on the Lorentz factor, which is equal to 1/sqrt( 1 – v^2 / c^2 ).

So let’s say you go so fast that the distance becomes just one light year. That means a round trip will take 2 light years. This way, you actually could visit the galaxy. It would take you just 2 years for a round trip.

However, for your friends back on Earth, 2 million years would have passed, so there’s no way you would be able to tell them about it and all the amazing things you found in the Andromeda galaxy.

Two students sitting next to me said that for the person on the spaceship, his clock would show only 2 years, but his body would age 2 million years. What the heck?! People are not very smart. I talked with them about it, and I could not manage to convince them that your body would age at the same rate as the clock that’s traveling with you. Apparently, Bickers said something earlier in the lecture that they interpreted as stating that everyone’s body always ages at an absolute (and equal) rate. Hogwash (nonsense)! It’s times like these that I feel smart. Of course, it won’t be long until something happens that makes me humble again.