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notjoematheis asked:

I'm confused on the nature of gravity in space. Why is it called "zero gravity"?


First, there’s gravity everywhere. We’ve got a whole episode on it. But we also have this unit of force called the g-force, sometimes abbreviated as G (though this isn’t a technical SI unit.) One G is the amount of force we all experience because of the Earth’s gravity all the time. Two Gs would be double that…we can experience this much force if we’re accelerating away from earth or on a planet two-times more massive than earth (but the same size.) Likewise, if we are in constant freefall (as astronauts are when they orbit the earth) they will experience no Gs at all.  We would call that “Zero G” which is not, oddly enough, the same thing as “zero gravity.” Gravity is a force…not amount of force, and just because you are under the influence of gravity (as everything in the universe is (as far as we know)) does not mean you are feeling “G forces.”


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