I often hear that gravity is not a force, but simply the curvature of spacetime. A common example given is having a heavy ball placed on a rubber sheet. The ball sinks, distorting the sheet. Therefore, other “orbiting” objects will also tend to roll towards the sunken part.
What I can’t understand is, what causes the objects to “fall” anyway? On earth, that’s just the planet’s gravity. If you did the same experiment on space the objects wouldn’t roll down. So how is this an explanation of gravity as a curvature, when it requires a *force* to work? Is there a better explanation? Am I just missing something?
In: Physics
Gravity is just a force in classical physics. If you start to venture down General Theory’s perspective of gravity, the 5-year-old could get lost. And you might be ready for a book on general relativity.
The ball rolling in the sheet is 4-dimensional model of physics where we only see the universe in 3-D but the sheet is actually a 4-D surface and each mass’s gravity distorts space away from a 4-D plane. However 4-D space / time is just a model that provides a solution to general relativity.
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