RENEE MONTAGNE, HOST:
The Perseid Meteor shower is an annual event. It starts sometime in July and peaks in mid-August. Maybe you caught some of it this weekend. It's just one of the many meteor showers that occurs during the year. As part of our series Summer Science, we asked NPR science correspondent Joe Palca to explain what happens in meteor showers. He told us the best way to explain it was to go the beach. Somehow Joe manages to pull the tough assignments, but we said okay, and the next thing we knew, he was out here in Southern California.
JOE PALCA, BYLINE: This is great. I'm on the boardwalk at Venice Beach in California. The sun is shining, there's people skateboarding and rollerblading, and there's wind and surf. It's fantastic. And yes, I know what you're thinking, but there really is a reason that I've come here to talk about meteor showers. You see, meteors are pieces of space debris that plow into the Earth's atmosphere. Most of this debris is no bigger than a grain of sand on the beach here, but sometimes they're big chunks of rock.
Often these meteors come from junk spewed out by comets as they orbit the sun. Now, comets are basically balls of ice and small clumps of dirt. Think of them as a kind of cosmic dump truck whizzing around the sun shedding their load as they go. To understand meteor showers, let's try this analogy.
(SOUNDBITE OF SHOWER)
PALCA: Imagine this outdoor shower represents the band of dirt streaming around the sun, and the water drops represent the individual grains of dirt. And now you have to imagine that I, Joe Palca, am the Earth, and every once in a while my earthly orbit takes me through this circling band of dirt. Whoo. The water droplets are the particles of broken comet streaming past me. Aah. Okay. I'm out now. I've passed through the droplets. And that's how you get a meteor shower.
The Earth passes through the grains of dirt as they stream into the atmosphere and blow past the air molecules in the atmosphere at supersonic speeds. This makes the air glow, so you get a streak of light until the grain burns itself up. Now, in a real meteor shower, it's not really a shower of dirt particles, maybe one or two a minute, more of a drip, drip, drip, really, but you get the idea. The Perseid shower peaked on August 12th, so you mostly missed that one. The next really big one is the Geminid shower in December. Hey, that gives me an idea. I could come back here and do this again. Joe Palca, NPR News, reporting from Venice Beach, California. Can I get a towel now? Transcript provided by NPR, Copyright National Public Radio.