The Inevitable Collision

The internet is currently buzzing after the official confirmation via observations with the Hubble Space Telescope that the Andromeda Galaxy will collide with our home galaxy, the Milky Way, in approximately 4 billion years.  When I was first learning about astronomy I remember reading about astronomers hypothesize that a head on collision with Andromeda was likely, so this news didn’t come as a shock to me.  However, it did give me pause, and made me think about an anthropocentric implication of this announcement.

What would this mean for human civilization?

I think this question may be something that has crossed a few people’s minds since the announcement.  Maybe it is the first thing someone thinks about when they hear about an inevitable collision between our home galaxy and an object twice its size.  And the answer about what this means for our civilization isn’t at all what you would think. First off, the collision is going to take place 4 billion years from now.  It is highly unlikely that our species will be around anyway, and if we are it will probably not be in our current form.  Modern humans have been experimenting with writing for 5,000 years; building cities for 10,000 years and have been in existence for only 200,000 years.  On universal time scales we have been in existence for a negligible amount of time.  Either biological or technological evolution will ensure that we will be nothing like we currently are in 4 billion years time.

However, let’s just say, for fun, that will be around, and that we will be a similar species biologically to what we currently are.  The collision with Andromeda will not be the first thing we would have to worry about over that course of time.  In 4 billion years our solar system will have become inhabitable.  This is because our sun will have become much brighter, larger and warming and may even be entering its final Red Giant phase, engulfing our entire planet.

It is unclear how our planet will react to our sun’s gradual warming over the next 4 billion years, or how/if humans can alter the natural processes that will occur if we don’t intervene.  However, what is clear, is that if we are around in 4 billion years time, we will have to have become a multi-star system species.

When we collide

Although becoming a multi-star system species saves us from becoming extinct via asteroid or a nearby black hole, would it also be an insurance policy against a galactic collision?  Is the collision with Andromeda an inescapable catastrophe that would devastate and eliminate any civilization unlucky enough to experience it?

Surprisingly, no, in all likelihood it would cause almost no disturbance whatsoever.

How, you might be asking, could a collision with a galaxy containing 1 trillion stars not devastate our galaxy?  Well, it comes down to scale.  The Andromeda Galaxy contains 1 trillion stars and our galaxy contains approximately 300 billion stars, but the key statistic is the distance between each of these stars.  Galaxies, just like solar systems, are mostly empty space.  And when an object that is mostly empty space collides with another object that is mostly empty space, the probability that any star will collide with another star is exceptionally improbably (although not impossible).  To put this to scale, if the sun was the size of a ping pong ball in Paris, the closest star to us would be a pea-sized object in Berlin, and our galaxy would extend out a third of a distance to Mars.

Furthermore, astronomers see galaxies throughout the universe that undergo galactic collisions all the time.  The star systems within these galaxies do not seem to be particularly disturbed and collisions between stars are exceptionally rare.  Finally, our Milky Way is technically subsuming a few dwarf galaxies at the moment.  These mergers happen without any increased chaos or danger on a galactic scale.



About Cadell Last
Hello. I'm probably drinking coffee and reading.

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