Einstein's general relativity says gravity is spacetime curvature, but what does that mean? Let's take a look at how gravitational time dilation results in a...
One could be picky and say you’re explaining gravity with gravity. But for the sake of simplicity that’s OK.
I’ve once read an article where someone complained about that and tried to explain it with the actual cause, curvature of space time, like using a model car with glue attached to the wheels. But that was not really intuitive and simple to understand.
I found a video once where the guy built a device to demonstrate curving based on mass, to avoid the gravity simulating gravity problem, but I failed to find it again when searching. It was something he’d bend to show larger mass, and you’d see the effect with the bands along it or something. Even that isn’t accurate, but visualizing 4D can be challenging, especially if you then have to put it in 2D media.
Exactly that one. Thanks, I’m glad I said something. It wasn’t anything new, just a new way to present it, and when he did the warped version and the straight line, I was like, okay, makes sense. Then he returned it to our “viewpoint” on the warped space seeing things straight, and even though it was the same lines, it was amazing to see those paths go precisely where we expect. All because of a warped graph. I think it was more incredulous because it wasn’t some animation, but a physical demonstration.
I think of it as a 2d cross section of the experiment (it’s happening in every direction possible tangent to the ball), which necessarily breaks into a third dimension. In our 3-spatial-dimension reality that’s the best we can do.
Yes, but the smaller object is dragged into the valley formed by a heavier object due to gravity (of the earth), not due to following the curvature of the blanket.
Sure but it is still a cross-section of what it is — something with a mass of that bowling ball being gravitationally attracted to something the mass of Earth. The blanket is a demonstration of what spacetime is doing (how it’s being warped) by the gravitational attraction. It so happens that you can also sort of demonstrate how another object can be influenced by the bowling ball’s gravity as it’s being gravitationally attracted by something else (like how a small object would be attracted to the moon which is still being attracted to Earth). Given that nothing can really ever be gravitationally unbound, I think it’s a fine demonstration. I wonder if you’re expecting it would demonstrate something it isn’t demonstrating (like how an object in isolation would influence some other object in isolation).
One could be picky and say you’re explaining gravity with gravity. But for the sake of simplicity that’s OK.
I’ve once read an article where someone complained about that and tried to explain it with the actual cause, curvature of space time, like using a model car with glue attached to the wheels. But that was not really intuitive and simple to understand.
I found a video once where the guy built a device to demonstrate curving based on mass, to avoid the gravity simulating gravity problem, but I failed to find it again when searching. It was something he’d bend to show larger mass, and you’d see the effect with the bands along it or something. Even that isn’t accurate, but visualizing 4D can be challenging, especially if you then have to put it in 2D media.
Here, probably this one. The only good explanation I’ve seen.
Exactly that one. Thanks, I’m glad I said something. It wasn’t anything new, just a new way to present it, and when he did the warped version and the straight line, I was like, okay, makes sense. Then he returned it to our “viewpoint” on the warped space seeing things straight, and even though it was the same lines, it was amazing to see those paths go precisely where we expect. All because of a warped graph. I think it was more incredulous because it wasn’t some animation, but a physical demonstration.
I think of it as a 2d cross section of the experiment (it’s happening in every direction possible tangent to the ball), which necessarily breaks into a third dimension. In our 3-spatial-dimension reality that’s the best we can do.
Yes, but the smaller object is dragged into the valley formed by a heavier object due to gravity (of the earth), not due to following the curvature of the blanket.
Sure but it is still a cross-section of what it is — something with a mass of that bowling ball being gravitationally attracted to something the mass of Earth. The blanket is a demonstration of what spacetime is doing (how it’s being warped) by the gravitational attraction. It so happens that you can also sort of demonstrate how another object can be influenced by the bowling ball’s gravity as it’s being gravitationally attracted by something else (like how a small object would be attracted to the moon which is still being attracted to Earth). Given that nothing can really ever be gravitationally unbound, I think it’s a fine demonstration. I wonder if you’re expecting it would demonstrate something it isn’t demonstrating (like how an object in isolation would influence some other object in isolation).
I find the metaphor frustrating because of that.
https://youtu.be/DYq774z4dws
This video includes a much better representation of what gravity is IMO. The creator had the same issue with people describing gravity with gravity.
Thanks for the deep dive.