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Joe Palca

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A scientist walks up to a cottonwood tree, sticks a hollow tube in the middle and then takes a lighter and flicks it. A jet of flame shoots out from the tube.

It seems like a magician's trick. Turns out, there's methane trapped in certain cottonwood trees. Methane is the gas in natural gas. It's also a powerful greenhouse gas.

So how does it get inside towering trees like the ones on the campus of the Oak Ridge National Laboratory in Tennessee?

It's easy to take corned beef sandwiches for granted. There's no mystery about them. They simply exist.

But corned beef sandwiches, along with everything else in the universe, raise a critical question in the minds of physicists: Why do they exist?

In the earliest moments of the universe, energy turned into matter. But matter comes in two forms, matter and antimatter. And when a particle of matter encounters a particle of antimatter, they annihilate each other — and all you're left with is light.

Small drones can do big jobs: Firefighters can use them to find hot spots in blazes, environmental monitors can find the source of hazardous chemical leaks. One just delivered a human kidney for transplant surgery.

But it takes lots of power to spin four helicopter blades fast enough to keep a quadcopter-type drone in the air. Most can only stay aloft for about 30 minutes.

ARI SHAPIRO, HOST:

A NASA probe on Mars is hearing things. And in this case, that's good news. The lander called InSight is supposed to listen for marsquakes, the Martian equivalent of earthquakes. Now it's heard one maybe. NPR's Joe Palca has more.

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