Monday, February 27, 2017

How far can you see?

     Can you see five miles?  Ten?  A hundred?  A thousand?

     Even with just your naked eyes, you can see vastly farther than you may have ever thought possible.  And at the same time you can become a phenomenal time traveler.

     Whenever you look up at a moonless night sky, no matter how clear or dark it is, every star you see lies only within our own Milky Way galaxy, a glittering spiral disc of billions of suns and their attendant planets.  Yet our cherished Milky Way is only one of billions of galaxy islands scattered throughout the universe. 

     The clearest, farthest object you’ll ever see with just your eyes from the northern hemisphere is another spiral galaxy of some trillion suns.  It’s Andromeda.  When you look at that faint fuzzy oval, it’s difficult to believe that the ancient light you’re seeing left there 2.5 million years ago.

    Put another way, Andromeda is 2.5 million light years away from your retinas.  Since light travels 186,000 miles PER SECOND, that means Andromeda is 15 quintillion miles away, or 15 followed by 18 zeroes—that’s how many miles you’re seeing. 

     Your eyes are also taking in Andromeda light that is from a time well before any homo sapiens (human beings anatomically similar to us) inhabited our earth.

     So you can see pretty far, indeed, in both miles and time.

     Incidentally, our beautiful Milky Way and stunning Andromeda share a frightening mutual gravitational attraction.  The two galaxies are hurtling directly toward each other at an astonishing 250,000 miles per hour.  Yet the distance is so incredibly vast that they won’t merge into one giant galaxy for another four billion years.

     So not to worry.


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