Gravity Sucks: Difference between revisions

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When it is mentioned at all, the force of gravity is often portrayed as a sort of cosmic quicksand, an intractable mire that can yank spacecraft out of the sky without any consideration of inertia. Frequently accompanied by exclamations like, "We're caught in the planet's gravitational field!" or "We're being sucked in!"
 
[[Useful Notes/Black Holes|Black Holes]] are particular offenders of this nature, not only in fiction but also in many people's perceptions in the real world. Few people seem to understand that a black hole will exert (roughly) the same amount of gravitational force as the star it was formed from<ref>When you're at the same distance from the center of the black hole as you were from the center of the original star, that is, assuming that distance is greater than the radius of the original star itself. If you go to a spot near the black hole that would have been inside the radius of the original star, the gravitational force will exceed that for the star at the same distance. And if you pass the black hole's event horizon, you can only go inwards, no matter how hard you try not to.</ref>.
 
The trope stems from a naive Aristotelian view of gravity, coupled with [[Space Friction]]. After all, a baseball falls to the ground; why shouldn't a spaceship? The answer, of course, is that the ship ''is'' falling, it's simply missing. If the ship is moving at any significant speed relative to the planet, in a direction other than straight up or straight down, its momentum will carry it past and it won't actually hit. This, boys and girls, is called an "orbit". Unless something like a gas cloud acts on the ship to slow it down, it will continue to miss the planet until slight variations in the path happen to bring it into the planet itself, which can take quite a long time.