That’s special relativity. General relativity is the theory of the curvature of spacetime as the mechanism for gravity. Large masses curve spacetime more than small masses. Under GR, gravity is not a force.
Good point but why “no bowling ball on a trampoline nonsense”? That’s not a correct analogy, since it deforms “space” different from how gravity transforms space, but it’s good enough to understand how that works, I think
Oh because that incorrect analogy is the most common “lay person” analogy for describing gravitational curvature of spacetime. The most common reply from children is that it’s the earth’s gravity pulling down on the bowling ball so that the trampoline demonstration wouldn’t work in space.
Also the trampoline analogy doesn’t show us how gravitational lensing works, nor does it even touch how different gravitational reference frames affect the passage of time (GR generalizes special relativity, after all).
Affecting passage of time looks like a difficult idea to come up with an analogy.
For the better gravity analogy, I think a rubber sheet that has something pulling together at a “gravity well” and lines drawn on it may work better, but I’m not sure 😅
The harder thing to convey is the full dimensionality of it. With the rubber sheet (or trampoline) you can show a small ball orbiting around a larger one but only in a single plane (around the “equator” of the large ball). However in reality you can orbit in any direction you like and many satellites actually orbit over the poles. Trying to show that with a small model seems extremely difficult!
Furthermore, most children are raised on the idea that gravity is pulling them down. They intuitively understand the idea that when they climb a ladder and drop a ball from the top, the earth pulls the ball down. General relativity tells us that this is not happening at all! That there us nothing pulling us down whatsoever. I have yet to see anyone provide a lay person GR explanation for the ladder problem.
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That’s special relativity. General relativity is the theory of the curvature of spacetime as the mechanism for gravity. Large masses curve spacetime more than small masses. Under GR, gravity is not a force.
Good point but why “no bowling ball on a trampoline nonsense”? That’s not a correct analogy, since it deforms “space” different from how gravity transforms space, but it’s good enough to understand how that works, I think
Oh because that incorrect analogy is the most common “lay person” analogy for describing gravitational curvature of spacetime. The most common reply from children is that it’s the earth’s gravity pulling down on the bowling ball so that the trampoline demonstration wouldn’t work in space.
Also the trampoline analogy doesn’t show us how gravitational lensing works, nor does it even touch how different gravitational reference frames affect the passage of time (GR generalizes special relativity, after all).
Affecting passage of time looks like a difficult idea to come up with an analogy.
For the better gravity analogy, I think a rubber sheet that has something pulling together at a “gravity well” and lines drawn on it may work better, but I’m not sure 😅
The harder thing to convey is the full dimensionality of it. With the rubber sheet (or trampoline) you can show a small ball orbiting around a larger one but only in a single plane (around the “equator” of the large ball). However in reality you can orbit in any direction you like and many satellites actually orbit over the poles. Trying to show that with a small model seems extremely difficult!
Furthermore, most children are raised on the idea that gravity is pulling them down. They intuitively understand the idea that when they climb a ladder and drop a ball from the top, the earth pulls the ball down. General relativity tells us that this is not happening at all! That there us nothing pulling us down whatsoever. I have yet to see anyone provide a lay person GR explanation for the ladder problem.
Not in Australia, though