The discussion centers on the nature of space and spacetime, particularly whether space moves when it changes shape due to mass and gravity. Participants explore concepts related to relativity, the geometry of spacetime, and the implications of these ideas on our understanding of motion and shape.
Participants express differing views on whether space moves when it changes shape, with no consensus reached. Some maintain that spacetime does not move, while others question the implications of shape change.
There are limitations in the discussion regarding definitions of movement and shape, as well as the assumptions underlying the nature of spacetime and mass. The conversation reflects a range of interpretations and conceptual challenges without resolving these complexities.
That's a popsci description, and isn't really very helpful for understanding.ddjj77 said:Mass causes space to change shape, and that's what we see as gravity.
No. Relativity talks about spacetime. What you call "all of space at this time" is a slice of spacetime. What you call "all of space at a slightly later time" is a different slice of spacetime. It may well have a different "shape" from the earlier slice, but that's because it's a different part of spacetime, not because one piece changed shape.ddjj77 said:But does space move when it changes shape?
It's baffling how something can change shape without moving.Dale said:Spacetime does not have a velocity. So, no, it does not move.
It doesn't change shape, anymore than a film of a guy running actually moves. You are just looking at different parts of a static whole.ddjj77 said:It's baffling how something can change shape without moving.
That is because you are used to more or less rigid objects made out of a fixed amount of matter which change shape by having one part of the matter move relative to another. Spacetime isn’t like that at all.ddjj77 said:It's baffling how something can change shape without moving.
ddjj77 said:Mass causes space to change shape