Gravity does negative or positive work with cosmos redshift?

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doudou
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Based on the fact of observed cosmological redshift, scientists have proposed different ideas to explain. One interesting question is whether gravity does negative or positive work now:

According to universe expanding in Big Bang theory (Lemaitre, 1927), obviously gravity does overall negative work.

According to De Sitter's model (Willem de Sitter, 1917), redshift is caused by expansion of space itself, in this model, distance is no longer an intuitional concept, that makes it more complicated.

According to Dicke's model (Dicke, 1948-1949), it seems that gravity doesn't do overall negative or positive work in steady-state universe.

According to Tired Light theory (Zwicky, 1929), redshift could be explained by a contracting universe, in which gravity does positive work.

How to answer this question?

Thank you.
 
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Both Lemaitre and de Sitter spacetimes are solutions to the Einstein Field Equations. They don't model gravity as a force and they are neither stationary nor asymptotically flat, so I would say that "gravity does work" is not a useful concept.

I'm not familiar with Dicke's gravitational theory, but his Wikipedia page notes that he argued that the universe was near critical density, and hence spatially flat not steady state.

Zwicky's tired light is not consistent with observation, so its predictions aren't important.
 
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PeroK said:
Read an up-to-date cosmology book?
Wishing you can propose something remarkable in physics, by reading up-to-date books and posting sarcasm in forum.
 
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Ibix said:
Both Lemaitre and de Sitter spacetimes are solutions to the Einstein Field Equations. They don't model gravity as a force and they are neither stationary nor asymptotically flat, so I would say that "gravity does work" is not a useful concept.

I'm not familiar with Dicke's gravitational theory, but his Wikipedia page notes that he argued that the universe was near critical density, and hence spatially flat not steady state.

Zwicky's tired light is not consistent with observation, so its predictions aren't important.
Thank you Ibix for kind reply :)

You are right, using language should be more careful here.

Those theories or solutions are mentioned, just because they represent typical prediction about the fate of Universe, expanding, steady, or contracting.

This is a last-lasting debate, and seems no wide agreement yet. One of my consultants, he is a physicist, who support Big Bounce. However, even among its supporters, they do not agree on which phase the universe is undergoing.

In history, it is not rare that for many years, one explanation to a certain observation is in favor, then another is, so probably, we will not be shocked if mainstream changes in the future.

Personally, which theory about the fate of Universe you prefer?
 
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doudou said:
Personally, which theory about the fate of Universe you prefer?
Our current best fit model is a flat or very nearly flat universe with eternal expansion. That may change as we get more data.