I saw a video today of a NASA supercomputer’s simulation of the collision of two spiral galaxies. It is less than two minutes long but simulates the passage of nearly 2 billion years. I am amazed at how much the behaviour of these truly giant structures resembles the swirling of smoke from an extinguished candle. After the galaxies collide and pass through each other there is a period before they collide again (at about 0:50-1:00) where what appears to be gas is being thrown out, away from the galaxies into the rest of the universe. What amazed me so much about this video was that the gas was actually a whole bunch of stars. Stars much like the sun.
The Milky Way is going to collide with its neighbour galaxy, Andromeda, in about four billion years. While the Sun will be near the end of its life at that point (and so the Earth will no longer be inhabitable because the oceans will have boiled off), it will still be burning. It’s possible that the Sun could be one of those stars that gets blown out into the universe. This might seem like a big deal, but I don’t think it would have much of an effect on the solar system. The Sun is so far from the nearest star anyways that its position in the Milky Way has negligible effects. Our solar system would behave the same way whether or not it was in a galaxy.
This makes me glad that life evolved on Earth when it did. Had it happened 5 billion years later, we might not have been able to observe anything else in the universe. There might not have been stars in the night’s sky and astronomy would not exist as we know it. We wouldn’t know about galaxies or the universe, but I bet we would get to know our solar system a lot better. I guess there is a bright side to everything.