Astronaut Ron Garan, currently on board the International Space Station, was taking pictures of our home world out the window — and how cool is it to be able to say that? — when he took this amazing picture of a meteor burning up in our atmosphere:
Wow! [Click to bolidenate.] How cool would it be to look down to see a falling star?
He took this shot (according to the header info in the picture) on August 13 at 7:17 p.m. UT, when the ISS was above the Mongolia/China border. This was during the annual Perseid meteor shower, but that doesn’t guarantee this meteor Ron saw was a Perseid. It probably was, though. For an observer on Earth, the Perseids rain down at a rate of about 60 per hour or so. You can usually see about 5 meteors per hour that are just random bits of cosmic detritus. So only 1 meteor in 12 is not a real Perseid, making it likely this one was.
But that got me thinking… [WARNING: math ahead. Cool, tasty, refreshing math that will lead to insight, wonder, potential party conversation (assuming you go to the same dorky parties I do), and other nifty things.]
Meteors burn up roughly 100 kilometers (60 miles) above the Earth’s surface. To make the math simpler, let’s say they burn up at exactly that height, so that any meteor coming in hits this barrier and evaporates. You can picture it as a thin shell of air surrounding the Earth 100 km high, like a force field, or better yet as an umbrella that rain hits (it’s a meteor shower, after all, ha!) and stops cold.
When you look straight up, that barrier is 100 km directly above your head. When you look to the horizon, that distance is actually a little over 1000 km away, because the atmosphere follows the curve of the Earth (you can get an idea of this in the diagram above). The top of this umbrella is then 100 km up and over 1000 km to the sides.
From the space station, though, looking down from orbit at a height of roughly 350 km, more of the atmosphere can be seen because the station is higher up (just like you can see farther if you go to the top of a building). Read More