Gravity & Dark Energy: Newton, Einstein & Beyond

[Dennis Plews]

TL;DR Summary

Are Gravity and Dark Energy the same?

What gravity is, as pointed out by Newton and Einstein, is still a mystery. Adding to that conundrum is dark energy which continues to inflate the cosmos. Both Newton and Einstein, and every one else as far as I am able to discern, assume that gravity works by drawing massive bodies together through space-time warping. I have not yet been able to find any writer who can explain how gravity forces mass and energy to follow geodesic lines.

Adding to my confusion is the finding that dark energy causes space-time to expand, most rapidly in the intergalactic voids and at the edge of our ability to see. It’s opposite sign to that of gravity may be explained by the Friedman equations but I have a speculation that I have not seen addressed or posited anywhere.

In one of the science books I have read I recall that Einstein is quoted as having said that “matter is lumpy bits of space time.” Assuming that to be true and adding the ideal gas law to the mix, I have wondered whether the existence of matter/energy lowers the pressure of dark energy in its immediate vicinity so that space-time moves towards the matter in a flow akin to that of a gas moving to a low pressure region from a high pressure region. Can anyone direct me to a paper that addresses this speculation?

 

[PeroK]

Summary:: Are Gravity and Dark Energy the same?

What gravity is, as pointed out by Newton and Einstein, is still a mystery. Adding to that conundrum is dark energy which continues to inflate the cosmos. Both Newton and Einstein, and every one else as far as I am able to discern, assume that gravity works by drawing massive bodies together through space-time warping. I have not yet been able to find any writer who can explain how gravity forces mass and energy to follow geodesic lines.
Adding to my confusion is the finding that dark energy causes space-time to expand, most rapidly in the intergalactic voids and at the edge of our ability to see. It’s opposite sign to that of gravity may be explained by the Friedman equations but I have a speculation that I have not seen addressed or posited anywhere.
In one of the science books I have read I recall that Einstein is quoted as having said that “matter is lumpy bits of space time.” Assuming that to be true and adding the ideal gas law to the mix, I have wondered whether the existence of matter/energy lowers the pressure of dark energy in its immediate vicinity so that space-time moves towards the matter in a flow akin to that of a gas moving to a low pressure region from a high pressure region. Can anyone direct me to a paper that addresses this speculation?

You could start here:

https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/

Most of your questions are based on misunderstanding modern cosmology.

 

[PeterDonis]

Both Newton and Einstein, and every one else as far as I am able to discern, assume that gravity works by drawing massive bodies together through space-time warping.

That's not how Newton said gravity works. He said gravity was a force.

Einstein's General Relativity includes solutions in which massive bodies are attracted to each other because of the spacetime geometry caused by their mass, but those aren't the only solutions it includes.

I have not yet been able to find any writer who can explain how gravity forces mass and energy to follow geodesic lines.

You must be joking. Do you know how many GR textbooks there are?

dark energy causes space-time to expand

No, it doesn't. Spacetime doesn't expand or contract. It just is.

The effect of dark energy is sometimes described as causing an accelerated expansion of space, but this is only a heuristic picture and can be misleading if taken too literally.

It’s opposite sign to that of gravity may be explained by the Friedman equations

For "may be" read "is".

I have a speculation that I have not seen addressed or posited anywhere.

Please review the PF rules regarding personal speculation. We do not discuss personal speculations here.

In one of the science books I have read I recall that Einstein is quoted as having said that “matter is lumpy bits of space time.”

Please give a specific reference (and to me by PM, since this thread is going to be closed). Just a vague allusion to "one of the science books I have read" is not sufficient.

 

[PeterDonis]

The OP question is based on personal speculation and is off limits for PF discussion. Thread closed.

 

[Nugatory]

Both Newton and Einstein, and every one else as far as I am able to discern, assume that gravity works by drawing massive bodies together through space-time warping. I have not yet been able to find any writer who can explain how gravity forces mass and energy to follow geodesic lines.

You won't be able to - that answer does not exist. We could try explaining why mass follows geodesics in spacetime by saying it's just a restatement of Newton's first law, but that just leads the next "why?" question: Why does Newton's first law work? The only answer to that question is "Because that's the way the universe we live in works". Physics is about knowing what laws govern the behavior of the universe, not why the universe behaves according to those laws.

The forum rules do not allow discussion of personal theories and speculation, so this thread is closed.

 

[PeterDonis]

You won't be able to - that answer does not exist.

To be clear: the question you're responding to is "why"; but the OP asked "how". GR does explain how the trajectories of objects are determined. It just doesn't explain why (because, as you note, physics doesn't answer those kinds of "why" questions).