B Analogies for Gravitational Attraction in Physics

geordief
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We have the trampoline to be sure but are there others?
I am thinking of the mechanism that causes mass-energy to curve spacetime

We have the Wheeler (was it ?)description, viz approx "mass tells spacetime how to curve and spacetime tells matter how to move...".

Are there any analogous circumstances in other areas of physics where all (or a subgroup of)objects attract each other and never repel?

I am just asking for the sake of being able to get some kind of intuition as to the effect and not in any hope that this might offer any real insight...
 
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The trampoline is a terrible analogy because it's demonstrating spatial curvature, which is only a tiny part of gravity in all but the most extreme circumstances. The ##tt## component of the Schwarzschild metric, which is responsible for almost all day to day gravitational effects, is not illustrated at all.

@A.T. produced this video, which is a much more honest illustration. I believe he says it is based on representations in the book "Relativity visualised" by Lewis Carroll Epstein.
 
Ibix said:
The trampoline is a terrible analogy because it's demonstrating spatial curvature, which is only a tiny part of gravity in all but the most extreme circumstances. The ##tt## component of the Schwarzschild metric, which is responsible for almost all day to day gravitational effects, is not illustrated at all.

@A.T. produced this video, which is a much more honest illustration. I believe he says it is based on representations in the book "Relativity visualised" by Lewis Carroll Epstein.

Yes,I have seen that one.

I would class that as an analogy too (and yes,I am asking for analogies) but I was fishing for some kind of a circumstance where all (or all of a class of) objects exert a force of attraction on each other-no repulsion involved.

As I say ,it is just a request based on personal curiosity rather than based on anything of threal importance.

Edit: see you have changed the video.Will have a look at it later

Edit#2 the video seems to have "reverted back" Apologies.

Seems to be a smorgasbord of related videos showing .I can't keep up with this new fangled youtube thing.
 
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I asked a question here, probably over 15 years ago on entanglement and I appreciated the thoughtful answers I received back then. The intervening years haven't made me any more knowledgeable in physics, so forgive my naïveté ! If a have a piece of paper in an area of high gravity, lets say near a black hole, and I draw a triangle on this paper and 'measure' the angles of the triangle, will they add to 180 degrees? How about if I'm looking at this paper outside of the (reasonable)...
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...

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