Light the Way

I'm not sure how to slide into this subject.

'In the beginning there was darkness upon the face of the void...'

Before I run face first into this post, I have to wonder- was this just an expression in poetiic terms or did it intimate that people knew more about the universe than we have ever given them credit for? I suppose it was the former... I guess I'll go ask the Dogon People. Considering that the phrase was written circa 410 A.D., it leaves the question open to at least a teensy bit of wonder.

Now. It's suddenly 2.5 and something million years ago. Somewhere out there, a galaxy the size of our own is just as it is when we look at it right now and it's about to hit ours.

HMMM???

Yes, I thought that might cause you to stop dead. I haven't done the math all the way through; I do have a few other things to do besides sit here and write. Consider that  our neighbor M-31 (fondly known as the Andromeda galaxy) is going to 'hit' ours. That's a fact, so I'm assured. That galaxy was 2.54+- light years away when the light we see it by left that body of stars, etc. So... it's not really  where we see it, right? It's been trotting along during all that time. It's more complicated than that. I think there's some doppler effect there (the light is blue-shifted) and that may affect when we're seeing it.

Where does that leave us? Or when? I'm not at all sure, but I have this sneaky feeling that it's quite a few miles closer than it looks through Mr. Hubble's namesake. Now, I don't think we need to duck for cover just yet. Given the space between stars, we may not have to worry even comes the day the collision happens. It is, however, at least interesting to think about that day when the leading edge comes this way. Makes me wonder if anyone has calculated where the solar system will be in relation to the wedge-point. I couldn't find an intelligible reference for how fast M-31 is going relative to us, which doesn't make it any easier.

And this little exercise can be applied to other things. I speak of local stars. I don't have any idea if any  are headed this way, but given how close they are, I'd be real interested to know. If we saw something 4 lightyears from here, headed this way at half light-speed, I might be willing to get nervous. What's giving me a headache is trying to figure out just how much closer that thing would be. And just how long until we really do need to duck or run.

Remembrer what I said about building starships?