Speaker 1: Welcome to brain Stuff from house stuff works dot com
Speaker 1: where smart happens. Hi Am Marshall Brain With today's question
Speaker 1: how much does planet Earth weigh? It would be more
Speaker 1: proper to ask what is the mass of Planet Earth?
Speaker 1: The quick answer to that is approximately six times ten.
Speaker 1: To them, it weighs a lot. The interesting sub question
Speaker 1: is how did anyone figure that out? It's not like
Speaker 1: the planet steps onto a scale each morning before it
Speaker 1: takes a shower. It turns out that you can calculate
Speaker 1: the mass of something if you know the magnitude of
Speaker 1: its gravitational pull. Any two masses have a gravitational attraction
Speaker 1: for one another. If you put two bowling balls near
Speaker 1: each other, they will attract one another Gravitationally, the attraction
Speaker 1: is extremely slight, but if your instruments are sensitive enough,
Speaker 1: you can measure that gravitational attraction that two bowling balls
Speaker 1: have on one an other. From that measurement, you could
Speaker 1: determine the mass of the two objects. The same is
Speaker 1: true for two golf balls, but the attraction is even
Speaker 1: slighter because the amount of gravitational force depends on the
Speaker 1: mass of the objects. Newton showed that for spherical objects
Speaker 1: you can make the simplifying assumption that all of the
Speaker 1: objects mass is concentrated at the center of the sphere.
Speaker 1: He then came up with an equation that expresses the
Speaker 1: gravitational attraction that two spherical objects have on one another.
Speaker 1: It's force equals the gravitational constant times the mass of
Speaker 1: the first object times the mass of the second object
Speaker 1: over the distance between the two objects squared. Assume that
Speaker 1: Earth is one of the masses and that a one
Speaker 1: kilogram sphere is the other. The force between them is
Speaker 1: nine point eight kilogram meters per second squared. We can
Speaker 1: calculate this force by dropping the one ram sphere and
Speaker 1: measuring acceleration that the Earth's gravitational field applies to it,
Speaker 1: which is nine eight ms per second squared. The radius
Speaker 1: of the Earth is six million, four hundred thousand meters.
Speaker 1: If you plug all these values in and solve for
Speaker 1: M one, you find that the mass of the Earth
Speaker 1: is six times ten to Do you have any ideas
Speaker 1: or suggestions for this podcast? If so, please send me
Speaker 1: an email at podcast at how stuff works dot com.
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