WEBVTT - How much does planet Earth weigh?

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<v Speaker 1>Welcome to brain Stuff from house stuff works dot com

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<v Speaker 1>where smart happens. Hi Am Marshall Brain With today's question

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<v Speaker 1>how much does planet Earth weigh? It would be more

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<v Speaker 1>proper to ask what is the mass of Planet Earth?

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<v Speaker 1>The quick answer to that is approximately six times ten.

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<v Speaker 1>To them, it weighs a lot. The interesting sub question

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<v Speaker 1>is how did anyone figure that out? It's not like

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<v Speaker 1>the planet steps onto a scale each morning before it

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<v Speaker 1>takes a shower. It turns out that you can calculate

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<v Speaker 1>the mass of something if you know the magnitude of

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<v Speaker 1>its gravitational pull. Any two masses have a gravitational attraction

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<v Speaker 1>for one another. If you put two bowling balls near

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<v Speaker 1>each other, they will attract one another Gravitationally, the attraction

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<v Speaker 1>is extremely slight, but if your instruments are sensitive enough,

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<v Speaker 1>you can measure that gravitational attraction that two bowling balls

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<v Speaker 1>have on one an other. From that measurement, you could

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<v Speaker 1>determine the mass of the two objects. The same is

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<v Speaker 1>true for two golf balls, but the attraction is even

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<v Speaker 1>slighter because the amount of gravitational force depends on the

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<v Speaker 1>mass of the objects. Newton showed that for spherical objects

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<v Speaker 1>you can make the simplifying assumption that all of the

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<v Speaker 1>objects mass is concentrated at the center of the sphere.

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<v Speaker 1>He then came up with an equation that expresses the

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<v Speaker 1>gravitational attraction that two spherical objects have on one another.

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<v Speaker 1>It's force equals the gravitational constant times the mass of

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<v Speaker 1>the first object times the mass of the second object

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<v Speaker 1>over the distance between the two objects squared. Assume that

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<v Speaker 1>Earth is one of the masses and that a one

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<v Speaker 1>kilogram sphere is the other. The force between them is

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<v Speaker 1>nine point eight kilogram meters per second squared. We can

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<v Speaker 1>calculate this force by dropping the one ram sphere and

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<v Speaker 1>measuring acceleration that the Earth's gravitational field applies to it,

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<v Speaker 1>which is nine eight ms per second squared. The radius

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<v Speaker 1>of the Earth is six million, four hundred thousand meters.

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<v Speaker 1>If you plug all these values in and solve for

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<v Speaker 1>M one, you find that the mass of the Earth

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<v Speaker 1>is six times ten to Do you have any ideas

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<v Speaker 1>or suggestions for this podcast? If so, please send me

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<v Speaker 1>an email at podcast at how stuff works dot com.

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