Saturday, October 22, 2011

Spaceship Earth

A buddy of mine (thanks Cory) works in a planetarium.  Recently, he emailed me some things he'd learned while doing research for a new exhibit. 

Our sun, and indeed our entire solar system, revolves in a big ellipse (much like a race car track) around the center of our galaxy the Milky Way.  Even though we're moving very fast, the distances involved are huge so it takes 225 to 250 million years to take ONE trip around the galaxy.  To scale it down a bit, we can say it takes about 1,190 years to travel one light year.

To put that into perspective in terms of distance, the nearest star to us is Proxima Centauri at 4.24 light years away.  And the brightest star we see in the night sky is Sirius, which is 8.7 lights years off.  Thinking about these distances helps us understand why scientists and science fiction writers are so interested in faster-than-light speed travel.

Cory also sent me data that helps put this journey around the galaxy in historical terms, which is sometimes easier to wrap my brain around than the distances.  Since 821 AD, we've traveled approximately 1 light year.  We've sailed about 2 light years since 368 BC, which would be the time of ancient Greece.  From the time the Egyptians built the Great Pyramid, we've traveled 5 to 6 light years.  And since people were engaged in organized farming in the Indus Valley 9500 years ago to now, we've made it about 8 light years.

Cory also mentioned a theory that when our solar system moves through the more densely packed spiral arms of the Milky Way, these visits may coincide with mass extinctions on Earth due to what he called 'impact events.'  This ties in with the idea that a massive meteor may have killed off the dinosaurs.  Don't freak out, though.  We won't revisit those areas for many, many years.

When we sit and think about all this, we may realize the scope of human history is very small.  And the universe around us is vast.  But here we are, zooming through space in an amazing, perfect little cocoon--planet Earth.     

(Thanks to Cory for the facts.  Hopefully I didn't mangle them.  The pic is of the center of the Milky Way and is from:  Stephane Guisard at


  1. As we are able to take a closer look at other suns (stars) we are finding that most if not all of the stars have planets in orbit. This was tantamount to sacrilege just a mere twenty years ago in the scientific community and perhaps the religious arena as well. There are about 300 billion (BILLION!) stars in our Milky Way galaxy. How many planets are there?

    There is a documentary in the programming mix of PBS right now that discusses many of the missions that NASA has done in the last decade or two. It really discusses our search for life. For instance, NASA sent a probe right through the head of a comet and brought the probe back to earth! The damn thing had glycine in it, one of the simplest amino acids that is a 'building block for life.' We've dug down into asteroids in the Kuiper Belt and found other life supporting stuff. One of the outer planets has oceans on it. Oceans I tell you! With tides, waves, erosion, and rivers leading to them. They are oceans of methane but we've found freaky organisms that live in high molarity sulfuric acid and others that live off of those vents at 20,000 leagues under the sea. Who's to say that some organism can't live in very cold methane lakes. There is most certainly water on Mars. It would have to be underground and it may be all ice unless it is quite deep underground. The polar caps of mars are dry ice, but there is evidence that the edges melt into liquid carbon dioxide...
    I often like to believe that we are unique on a unique, life supporting planet and I think we may be Then there's a part of me that looks at a Hubble photo showing countless galaxies each with a trillion or more planets and I think of the posibilities.
    It's certainly worth investigating!

  2. Yeah, it's weird that scientists used to think that most stars didn't have planets. I guess because they couldn't see them because of the stars' brightness. Really, when you look at the math, the sheer, staggering number of galaxies and stars would seem to make it inevitable that there are other planets out there that support life. Let's just hope they're friendly...