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Cyber Space
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Is space time like a bowling ball on a trampoline or does it surround all matter like water does a submerged object?
DaleSpam said:Neither analogy is very good. I think that it is probably best to learn about spacetime directly rather than by poor analogies to other things which do not reflect most of the properties of spacetime.
Cyber Space said:i was just using those as example because it is most seen and worded as space time being one dimensional and the water one was just an example of it being surrounding and 3d that surrounds the matter.
phinds said:As Dale said, the analogies are seriously flawed. Space-time isn't a THING at all, it is a framework in which matter and energy exist. It's just like length. It isn't a thing, but you can measure the relative positions of things in it.
Cyber Space said:what i was trying to refer to was the concept of the gravity of matter bending space time and how it would be, since most diagrams show it as only bending space/time on one side.
Cyber Space said:Is space time like a bowling ball on a trampoline or does it surround all matter like water does a submerged object?
In my opinion any static picture might be misleading as the function of time being part of "space-time" is missing. I therefore prefer to identify the action of gravity with the motion of neighbouring inertial bodies. If their geodesics are bent towards or away from each other (due to relative acceleration) then the space-time in this region is curved, otherwise it is flat.Cyber Space said:Is space time like a bowling ball on a trampoline or does it surround all matter like water does a submerged object?
If time is a dimension of the diagram, then the diagram itself can be static and yet show the development over time. That is the whole point of a space-time diagram. But it still can be helpful to animate a space-time diagram, to show the progress of time:timmdeeg said:In my opinion any static picture might be misleading as the function of time being part of "space-time" is missing.
The trampoline is not a space-time diagram, just a space diagram. But the worldlines of free fallers are geodesics in space-time, not space.timmdeeg said:If their geodesics are bent towards or away from each other (due to relative acceleration) then the space-time in this region is curved, otherwise it is flat. In this sense you can use the trampoline picture by watching how the distance between some balls which are rolling towards the center develops over time.
The mathematical language used to describe spacetime is called Riemannian geometry.Cyber Space said:i was just using those as example because it is most seen and worded as space time being one dimensional and the water one was just an example of it being surrounding and 3d that surrounds the matter.
That's right. In case my wording wasn't correct, kindly let me know.A.T. said:The trampoline is not a space-time diagram, just a space diagram. But the worldlines of free fallers are geodesics in space-time, not space.
Every time I see someone use the phrase fabric of spacetime it makes me ill. As stated above, there's no such "thing" as the "fabric" of spacetime. The term "fabric" is a term used as an analogy to allow one to visualize something which is curving.Cyber Space said:Is space time like a bowling ball on a trampoline or does it surround all matter like water does a submerged object?
But in every theory of (quantum) gravity there is a "mathematical entity" like a 4-manifold, a Hilbert space of spin networks etc.PhysicistMike said:Every time I see someone use the phrase fabric of spacetime it makes me ill. As stated above, there's no such "thing" as the "fabric" of spacetime.
Yes. That's quite right. Spacetime is very much a mathematical construct, a manifold. It's just not something which is made of paper and fig leaves or any other kind of matter exotic or otherwise.tom.stoer said:But in every theory of (quantum) gravity there is a "mathematical entity" like a 4-manifold, a Hilbert space of spin networks etc.
I fully agreePhysicistMike said:It's just not something which is made of paper and fig leaves or any other kind of matter exotic or otherwise.
The fabric of space-time is not made of any physical material that we are familiar with. It is a theoretical concept used to describe the structure of the universe.
Space-time is a combination of the three dimensions of space (length, width, and height) and the dimension of time. It is used to explain how objects move and interact in the universe.
According to Einstein's theory of general relativity, the presence of massive objects, such as planets or stars, can cause space-time to curve. This curvature affects how objects move, and explains the force of gravity.
No, we cannot physically see or touch space-time because it is a theoretical concept. However, we can observe its effects on the movement of objects in the universe.
According to Einstein's theory, space-time is not constant and can be affected by the presence of mass and energy. It can also be affected by the expansion of the universe. However, on a small scale, it is considered to be relatively constant.