I was taught years ago that one of the many conditions that make the Earth stable enough for complex life is that our “big brother” Jupiter works as a vacuum cleaner, clearing out wayward comets and asteroids from the inner solar system so fewer of them have a chance to contact Earth. Makes sense, Jupiter is big.
I recently learned, however, that Jupiter’s “surface gravity” is only 2.5x that of the Earth. No offense to Jupiter, but that feels less like a Kirby and more like a Swiffer.
Is there some different measurement of gravity (other than “surface gravity) that I’m not aware of that’s doing the heavy lifting? Or is it possible that in another, hypothetically similar solar system, a rocky planet 2.5x the size of earth positioned roughly the same distance Jupiter is from Earth would do the same “vacuuming” work?
In: 1661
surface gravity isn’t that important for acting as a “vacuum cleaner”. By the time something’s at the surface, the job is done. What’s more important is a sense of how much space it influences, and that’s determined by its mass.
Jupiter is 318 times as massive as earth. If earth’s “influence” dies off after, say, some distance, then Jupiter’s extends almost 18 times further, affecting a region of space over 5500 times as large as earth’s sphere of influence.
The only reason Jupiter’s “surface gravity” is comparable to earth’s is that as well as being massive, Jupiter is huge: its surface is over 10 times as far from the centre as earth’s is, so gravity there should be 100 times weaker, and yet it still manages to beat us.
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