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Quick question about gravity.
DarwinsFavoriteTortoise
Registered User regular
Registered User regular
Ok here goes:
I know that energy cannot be created or destroyed, and that it is only transferred from one state to another. Where, then, does the energy needed for gravity come from? I mean, I'm assuming that energy is needed to hold all of us in place, yeah?
Thanks.
I know that energy cannot be created or destroyed, and that it is only transferred from one state to another. Where, then, does the energy needed for gravity come from? I mean, I'm assuming that energy is needed to hold all of us in place, yeah?
Thanks.
DarwinsFavoriteTortoise on
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Gravity is also something that we cannot explain yet. Matter just attracts other matter for some reason. There are some speculations with gluons and whatnot but nothing that explains why. It's more like models to calculate it, not explain it.
Gravity, like, just exists, man.
When Einstein was writing down his theory he guessed an equation of the form "geometry=matter", and ended up with http://bit.ly/FieldEquations
Which says that the presence of matter in space causes space to curve, and that curving tells the matter how to move. The more matter, the more curving, which we interpret as gravity. So the more curving, the more gravity.
So I would argue the energy due to gravity comes from the energy contained in masses.
The whole curvature thingymajigger isn't really an explanation, it's a theory that makes some calculations possible.
And I disagree that gravity=energy. If you "make" energy by dropping a ball, it's because the carbs from your ham sandwich lunch allows you to place the ball in a position to fall. It's more like you=energy.
So the answer to the question from the OP "Where, then, does the energy needed for gravity come from?" would be "the ham sandwich"
....sorta
Yeah people are excited because the LHC is meant to uncover 'physics beyond the standard model'. If we start to see things like supersymmetric partners and such, that would be really great. It would also be mind blowing if we didn't see anything new...
Why isnt general relativity an explanation? It is saying "Gravity is in fact a geometric effect and here is why".
Granted it is only relevant on astronomical scales, and is definitely not the final answer, But right now there is no nice theory of quantum gravity.
It doesn't say "Gravity is in fact a geometric effect and here is why". That's just the way it's simplified to make nice pictures, but that's not the point.
We're kind of heading into semantics here, which is almost always boils down to personal opinion. But for me an explanation is when we know why something happens. We don't know why gravity happens or how, that is sort of the end point of human knowledge.
At least, I think that's how it works.
For a science project waaaaay back I calculated the amount of dropped pencils it would take to move the earth 1 meter. Turns out the correct amount was "many"
I could suggests remediating to a high school physics textbook first, followed by something like "Relativity Simply Explained", which I very much enjoyed, and then on to things like "Gravity's Arc: The Story of Gravity from Aristotle to Einstein and Beyond"
It's closer to think of gravity as a spring. If you think of the Earth's surface as the neutral point of the spring, where it's not extended or contracted, no energy is required to keep us at that point. However, it takes energy to move us from the neutral point of the spring. This energy goes into the spring and is used to pull us back to the neutral position.
Of course, the actual neutral position is at the center of the Earth, but that makes my explanation a little harder to write :P