2 upvotes, 3 direct replies (showing 3)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
How does gravity work?
I understand the concept that two bodies will attract each other, and the force will vary with mass and distance, but I don't understand where that force is coming from.
The best image I got so far was objects on a trampoline. Heavier object will curve the plane toward, causing other close objects to fall toward it, but what does that plane represent?
Comment by uselessscientist at 26/04/2023 at 19:51 UTC
3 upvotes, 0 direct replies
The plane represents spacetime. As for how it works from an underlying perspective (intermediary particles, whatever else), that's still a great unknown.
Practically, we understand that mass distorts spacetime. Light travelling in a straight line will continue to do so, however that straight line would appear curved to an outside observer
Comment by vvtz0 at 27/04/2023 at 13:52 UTC
1 upvotes, 0 direct replies
There is no such force as gravity, basically. Gravity is distortion of spacetime caused by mass.
The problem that stands in the way of intuitive understanding of this is that we the humans can sense and understand the "space" part of the spacetime, but not really the "time" part - we only see the consequences of it, but not the "time" itself.
If you imagine yourself staying (floating) still in space for a split second near a massive object - you can say that you're not moving. That's only partially true, because you're indeed not moving in space, but you are at the same moment moving very fast through time. Now because the massive object distorts the spacetime, your path through the spacetime is not straight anymore, it is curved.
The closer it is to the massive object, the more is the curvature of the spacetime. Which means that at a larger distance from the object you move faster through time than at a closer distance. Which in turn means that your head is moving faster through time than your feet (if you're floating in space oriented in such a way that your feet are closer to the object than the head). So there's a gradient, a difference, in your speed through time between your feet and your head.
Provided that your head is still attached to your feet via your body, this action causes your whole body to turn in time dimension towards space dimension and causes you to start gaining speed in space towards the massive object.
It's like when you're moving in a car in a straight line in a forward direction, and then suddenly left side of your car slows down compared to the right side - this will cause the car to turn and you won't be going straight forward anymore, you'll start turning to the left gaining speed in left-wise direction and losing speed in forward-wise direction. The same thing with moving through spacetime: when moving in curved spacetime near massive object, one part of you slows down in time dimension and "turns you around" in time causing you to gain speed towards the object in space dimension and lose the speed in time dimension.
Some sci-pop channels on youtube that explain this without going into math:
Science Asylum https://youtu.be/F5PfjsPdBzg[1][2]
1: https://youtu.be/F5PfjsPdBzg
2: https://youtu.be/F5PfjsPdBzg
PBS Space Time https://youtu.be/UKxQTvqcpSg[3][4]
3: https://youtu.be/UKxQTvqcpSg
4: https://youtu.be/UKxQTvqcpSg
Comment by juklwrochnowy at 26/04/2023 at 20:40 UTC
0 upvotes, 0 direct replies
Reaserch Einstein's theory of general relativity. It answers exactly this question, but we aware that it is very convoluted for an amateur physics fan.