General Relativity : Einstein vs. Newton

What people said

Strong rec WillO · 2025-05 · Physics Stack Exchange · on “Interpreting Curved Spacetime”

This extremely short video is excellent, and clarifies why we need to talk about the curvature of space**time**, not just of space: [this video]

Recommends answerman · 2013-02 · Physics Stack Exchange · on “How exactly does curved space-time describe the force of gravity?”

As others mentioned, the main problem with the common visualization is, that it omits the time dimension. In the animation linked below the time-dimension is included to explain how General Relativity differs form Newton's model. [this video]

Recommends answerman · 2013-02 · Physics Stack Exchange · on “Alternate layman's metaphors for illustrating curved space-time”

Check out this links for better visualizations of curved space-time, which explain Einstein's gravity model in a non-circular way, and actually include the time dimension (not just space like the common rubber-sheet). [this video] [LINK] [LINK] [LINK]

Recommends answerman · 2014-01 · Physics Stack Exchange · on “Curvature of Spacetime”

The reason why space-distortion alone cannot describe gravity, is that space-distortion can only affect objects which already move through space. But gravity also affects objects which are initially at rest in space. Objects at rest in space still advance in time, so you have to combine space & time into one structure, like shown here: [this video] The distortion on the time axis describes the gravitational time dilation. Clocks placed lower in the gravitational field, run slower: [LINK]

Recommends anna v · 2014-03 · Physics Stack Exchange · on “Questions about spacetime curvature and gravity”

have a look at this video which maps space time in one dimension [this video] .Note the comment in the frame where both Newtonian plot and GR plot are given. In GR there are no gravitational forces, but there are the rest of the forces , like the electromagnetic ones keeping the apple on the branch.

Recommends answerman · 2014-03 · Physics Stack Exchange · on “Naive visualization of space-time curvature”

You have the right basic idea. But it gets simpler to visualize if you just drop the ball, or throw it vertically. Then there is just one spatial dimension to consider, and you can directly compare the paths in space and in space-time, like shown here: [this video] But note that this doesn't involve any intrinsic space-time curvature. Such curvature is related to tidal effects (geodesic deviation), which are negligible over small distances (like the height of an apple tree or a ball throw). However, over larger distances intrinsic curvature is inevitable, as shown in the last link of the video description: [LINK]

Recommends answerman · 2014-03 · Physics Stack Exchange · on “Questions about spacetime curvature and gravity”

How exactly has the spacetime curved or tilted for the apple at A due to the presence of the Earth at E, and how does the apple move to the earth by following the geodesic in free fall? (assume only one spatial dimention) Spacetime is not "tilted", like you show it, because the two dimension must be orthogonal everywhere. This is shown here: [this video]

Recommends ilikeyoyo · 2017-07 · Physics Stack Exchange · on “Spacetime curvature around a black hole”

I recently got an understanding of general relativity and what it means for spacetime to be bend, and what 4d spacetime really is ( [LINK] ). I understand that due to the equivalence theorem in GR, and since the magnitude of the four-velocity is always the speed of light, as time slows down near an object, movement in the x, y, and z. In addition, this animation was good at giving some visuals, explaining how the geodesics apply here. [this video] . My question is, in a black hole, what would happen to the curvature of the spacetime in the video link directly above. When I looked at the answer to this question, Spacetime around a Black Hole [LINK] , it has these pictures that aren't very helpful.

Recommends Doradus · 2020-08 · Physics Stack Exchange · on “Does the curvature of spacetime theory assume gravity?”

Gravity is not as important to the rubber-sheet analogy as one might think. It is needed for two things: Causing the weights to curve the sheet Causing the weights stay on the sheet as they move Anything that made these two conditions true would work for the demonstration. In fact, gravity is not an ideal mechanism for #2 because it has a component in the direction of the sheet, and so it causes acceleration along the sheet that actual general relativity does not exhibit. In any case, the rubber-sheet analogy only shows how space curves due to mass. In reality, most of the effects we observe are due to the curvature in the time direction. To visualize that, a cone- or horn-shaped curvature i

Recommends Eric Smith · 2021-05 · Physics Stack Exchange · on “Gravity is not a force - how does "accelerating up" work for the entire earth?”

If there were no forces acting between atoms, then all the particles making up the Earth (and us) would continue on their paths towards the Earth's center of mass. The Earth would get smaller and smaller, eventually forming a black hole, and everything would keep falling forever (roughly speaking... I don't want to get into black hole physics here). Fortunately for us, there are other forces at play, such as electrostatic repulsion between atoms, forces due to the Pauli exclusion principle, and pressure due to heat. All of these provide an upward force that accelerates matter away from its normal path towards the center of mass. And these are what keep you glued to the ground... or more accu