Pop quiz!  What star is closest to Earth?  Give up?  The sun, of course!  That one was east.  What's the next closest star?  Don't know?  Well, then pack your things.  We are off to find the next big ball of gas that shines just as brightly as our sun.  Right now, it's a small twinkle in the night sky.  I hope it isn't too far . . .


On Earth, you have all kinds of ways to measure.  That pencil might be inches away.  The door is a few feet away.  The backyard is seven meters away.  A meter is a little more than three feet long.  If you were walking, it would be equal to about one large step.  We use this unit to measure out short distances on Earth.  You could use a kilometer (that's a thousand meters) to figure out a place that's a bit farther away, like the store.  That will not work where we are going.  Space is so large even thousands of kilometers will get you pretty much nowhere.

Watch your step!

In space you have to take inches and feet and meters and throw them all out the window.  When you are in space, forget about them!  Interstellar means the space or things that happen between stars.  As we lift off from Earth, we are floating between stars.  I hope you used the bathroom before we left.  The next stop could be a long ways away.


Look!  The sun is coming up as we take off from Earth.  Say goodbye!  Even though it's big and bright and shining, the sun is still very far away.  92,960,000 miles!  Things are so far apart in space that we had to come up with a new way to measure.  An astronomical unit or an AU is how far the Earth is from the sun.  You can think of it as the meter of space.

An AU really doesn't look like it's that far.

With everything so spread out, how does anyone ever get anywhere?  Well, they don't!  People have made it to the moon, but space is so big, that might as well be inches away.  The only thing that can really cut through space is light, the fastest thing we know.  A light year is how far light travels in one Earth year.  Light moves about 300 million meters per second.  Wait, if nothing but light can move that far, what are we doing out here?

At 4.2 light years away, we'd better get an early start in the morning to visit our nearest neighbor, Proxima Centauri.

In the time it took you to read all of these words, we have only moved one mile into space!  That's right, we still have another 92,959,999 miles just to get to the sun.  That's the closest star!  I guess we should head back.  Space is too big for us to use the usual measurements we use on Earth.  We need to use astronomical units or light years to figure out how far away stars are.  I'm sorry, but we cannot go to the next star . . . yet.  The good news is, we're not light years from the next bathroom.



References:

Education.com.  "Interstellar Distance Measurement Help"  Education, 2010.  <http://www.education.com/study-help/article/trigonometry-help-interstellar-distance/>

Windows to the Universe.  "Proxima Centauri"  Windows to the Universe, 2012.  <http://www.windows2universe.org/cool_stuff/Proxima.html>