Recent content by kevindin

Given that the gravitational field falls to zero at the centre of a large body (e.g. the earth), what happens to the pressure curve? (Assuming no effects due to high temperature.) Does it ease off too? What would the curve look like and what would the formula be?

Cosmology textbooks aren't so good at answering 'what if' questions and isolated scenarios - that's why I hoped someone here could help. I'm not suggesting a Milne model, because we obviously do have matter/energy density, etc. What I'm hearing is that we can't currently differentiate between...

OK, I did mean "spatially flat" rather than "spacetime is flat" - I understand that matter curves spacetime - that wasn't the main question. What I'm looking for is evidence that space is expanding, and not just changing its shape because of the movement of matter. Redshifts on their own isn't...

Could you provide references for those assertions please? (Trying to learn here.) If you're referring to the FLWR model, then doesn't that contain theoretical assumptions and approximations? Is there any observational evidence, since Oridruin is saying that it isn't measurable? Thank you.

Can you please explain the "theoretical grounds"? Yes, spacetime is locally curved by the presence of matter. But that's not the same as expanding or contracting - isn't expansion just a theoretical possibility/assumption? And recent observations suggest that spacetime is flat.

Can you expand on why that is, or can you point me at links? (I have tried to look, but it's not easy separating the wheat from the chaff.) Thanks

Imagine that the CMB did not exist. What observational evidence exists to support the theory of the metric expansion of spacetime, as opposed to having a static spacetime and it's the matter distribution that is expanding - as it would in an explosion?

Is it possible to use the Kruskal-Szekeres metric? My gut feeling is yes, but I'm not sure of how to transform it into the expression I'm looking for. Thanks

That's what I'm not confident of - my maths is a bit rusty. Someone must have done this already.

I'm looking for an expression for the deflection of light in a static gravitational field. Referring to 'deflection of star light past the sun' in Sean Carroll's "Spacetime and Geometry" - equation 7.80 for the "transverse gradient": \nabla\perp\phi = \frac{GM}{(b^2 + x^2)^{3/2}}\vec b...