A Matter of Tremendous Gravity. Or Not.

Sep 01, 2003

RAY: All of us remember from our high school or junior high school physics, that the Moon has a fraction of the Earth's gravity. In fact, we were all told that it's a sixth the gravity of the Earth.

When those NASA guys faked the landing on the Moon, they were very careful to show the astronauts bounding from one spot to another, like they were kangaroos.

TOM: How DID they fake it?

RAY: Springs. Invisible wires. You've never seen Peter Pan? Anyway… for example, if you had a bathroom scale, and you put your 600-pound...

TOM: mother-in-law?

RAY: I knew you were going say that! If you put your 600-pound Bengal tiger on this bathroom scale, and then transport the tiger and the bathroom scale to the Moon, the Bengal tiger (or the mother-in-law), would weigh 100 pounds.

You with me?

TOM: I'm with you.

RAY: Here's the question. Is there anything you can think of that, if measured in the same way, would weigh more on the Moon than it does on the Earth? Now, I have an answer in mind, but there may be more than one right answer.


TOM: My answer was a helium balloon.

RAY: There you go. You're right. That's the answer. Any balloon with lighter-than-air gas, such as helium or hydrogen, would work for an answer. Because on the Earth it wouldn't weigh anything on the scale, right?

TOM: Right.

RAY: In fact if you were standing on the scale and holding a big enough helium balloon --

TOM: It could make you weigh less.

RAY: It could make you weigh nothing. If you tried to put it on the scale it wouldn't register because it would float away. But on the moon, because there is no atmosphere, in addition to being not much gravity, there's nothing for the balloon to float on. Therefore, if it doesn't explode, it'll sit on the scale and it'll actually weigh something, whereas on the earth it doesn't weigh anything.

So do we have a winner?

TOM: Yeah, we do have a winner. The winner is Rochan Sharusta, from Kathmandu, Nepal.

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