## Monday, October 15, 2012

### Space Is Big

Imagine yourself sitting by one of those globes from school showing a scaled-down Earth -- they're usually about 12" to 18" in diameter.  Now answer these two questions by imagining yourself waving your hand near the globe to indicate how far away you think is correct:

- Where does space begin?
- How far away is the Moon?

Where does space begin?  I'd guess that you're probably going to wave your hand somewhere around 1 or 2 ft away from the little planet.  But for what we popularly consider to be "space": if you smacked your hand right onto the globe you'd have been closer.

Compared to a 12" globe: Sunday's (amazing) skydive began 0.04" above the surface.  That's about half of a ruler's little tick-mark.  The International Space Station is 0.10", which is just one tick-mark.  Most satellites are put into Low Earth Orbit, which maxes out at just under 2 inches away.  The upper limit of Medium Earth Orbit -- which is home mostly to fancier & more expensive satellites -- goes up to only about 3 ft away.

How far away is the Moon?  You probably waved your hand in the range of 3-5 ft distant from the globe, which is convenient since in your mental image of sitting/standing by this globe that's well-within an easy reach.  Well... the Moon would actually be 30 feet away.  Next time you're asked this question: leave the room and go next door.

The Sun?  That's more than 2 miles away.  Our nearest stellar neighbor, Alpha Centauri?  By the scale of that 12" classroom globe, Alpha Centauri is well over twice the *actual* distance between Earth and the Moon.  But since we already can't fathom that distance correctly in the first place- it's best to just call it a day at that.

Space is big. Our planet is small and we're even smaller.