This is my personal thoughts, opinions and musings place. I will also rant about things, especially politically-correct things that irritate me. And sci-fi. Did I mention sci-fi? There'll be lots of sci-fi stuff here. And movies, too. Mmmmm... Movies

Thursday, June 09, 2005

Looking into the past

One of the interesting aspects of astronomy is the fact that whenever you look at anything in the sky, you're basically looking directly into the past. Even when you're looking directly at the sun, which is one(1) AU away from Earth, you're looking into the past. Five hundred(500) (150,000,000km divided by 300,000(speed of light)) seconds into be the past, to be relatively exact, or just over 8 minutes. Which means, when all is said and done, that if our sun were to just blow out one sunny day(like, say, somebody dropping an active stargate into it), it would take more than 8 minutes for us to find out about it. And that's just the sun, which is so close to us, astronomically speaking.

Now, look at something a little further away, something like the Andromeda galaxy, which is 2.9 million light years away. Since a light year is the distance travelled by light in one year, this means that when you look at the Andromeda galaxy, you're really seeing it as it was 2.9 million years ago. In that time, it have been completely destroyed, but we wouldn't know about it until the light of that even reached us, which if it happens today, won't be for 2.9 million years. Of course, all this assumes that physics in the world wide universe behave the way we expect, and there aren't any weird space warps or light accelerants out there, and that light really does travel at 300,000km/s.

What does all this mean? It means that any time you look up at the night sky, you're stepping into a time machine that can only go backwards. The further the object is from Earth, the longer it's light takes to reach us, and the further back in time you go when you look at it. This has a serious impact on the Seti@Home Project, which attempts to utilize the idle CPU cycles of thousands of home and office computers to analyze signals detected in the sky in an effort to find extraterrestrial civilizations.

Since the project looks at radio waves, and radio waves travel at, or slightly slower than, the speed of light(300,000km/s), that means that the project is actually trying to detect signals from civilizations that would've been using radio thousands, and possibly tens of thousands, of years ago. If there were no such civilizations, and they are only now using radio, their signals won't reach us for a very long time, unless we make contact some other way.

So remember this: any time you want to escape into the past, simply look up at the sky on a clear night, preferably away from the city. When you do that, you truly are looking at a galaxy far away, a long time ago.


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