What is the Explanation for Gravity and the Role of Lovelock's Theorem?

[Mark R Jacobson]

I'm a new member. I am not a scientist but have been studying physics and paleoanthropology for i guess 30 years. I am particularly interested in what is going on at the edge of the universe; the continuing unfolding of space/time that began with the big bang. I think the same forces that caused the big bang may still be at work there. I suspect that the non-dimensional void just beyond (or at) the edge has something to do with the accelerating expansion of the universe. As the universe grows, there is more time/space fabric, and this increase may be part of the reason for the accelerating expansion. (I am somewhat skeptical of the dark matter/dark energy hypotheses) Anybody who has some ideas/info on this is welcome to let me know.

 

[Greg Bernhardt]

Welcome to PF Mark!

Please note we have strong rules against speculation. We are a mainstream science education community. We stick to discussion of material found in peer reviewed journals and textbooks. Thanks!

 

[Mark R Jacobson]

But, dark matter, dark energy are speculations. they may be published, but they are really just guesses.

 

[Greg Bernhardt]

But, dark matter, dark energy are speculations. they may be published, but they are really just guesses.

I'm not going to argue with you, but let's make it clear that speculation outside of peer reviewed material is not allowed. If you can't back your statement up with peer reviewed material don't post it. We are mainstream.

 

[Mark R Jacobson]

ideas are not allowed? my knowledge of physics comes from reading journals and studying for many years. i cannot cite anything, because i have not been keeping track.

I am a former US Peace Corps volunteer (Lesotho), an MBA (Carlson School, MN), and have 30 years of experience working as a development director for national nonprofit organizations lobbying on Capitol Hill and elsewhere. I hitchhiked across Africa and have more life experience than anyone that i know. "Peer reviewed" does not impress me because so much of our society's widely accepted "facts" and information is just plain wrong.

Right off the bat, the physics community has failed to explain gravity to the masses and it continues to talk about gravity as if it was a real force in nature. But, mass does not attract other mass, but rather curves space. Yet, if you asked 10,000 science teachers at the high school and college level to explain gravity. 99% would get it wrong. And the science journals continue to talk about gravity in the traditionally accepted, Newtonian manner. Peer reviewed? I don't trust this at all.

 

[Greg Bernhardt]

I think you are confused what kind of community you joined. We have a clear mission and purpose. That is to discuss and educate within mainstream science. There are other science communities that allow speculation and personal theories. You may want to search for them.

 

[Mark R Jacobson]

I think you are confused what kind of community you joined. We have a clear mission and purpose. That is to discuss and educate within mainstream science. There are other science communities that allow speculation and personal theories. You may want to search for them.

So, you are okay with how physics, gravity in particular, is explained? This is not me speculating. Your community of experts has failed entirely here. But you won't hear of it because you have rules that keep new or alternative ideas out (because I don't have a PhD.)

 

[Mark R Jacobson]

BTW, please get a different photo of yourself. It is too revealing.

 

[Greg Bernhardt]

So, you are okay with how physics, gravity in particular, is explained? This is not me speculating. Your community of experts has failed entirely here. But you won't hear of it because you have rules that keep new or alternative ideas out (because I don't have a PhD.)

Mark, I have explained that our community has a specific purpose. You joined us. I have sent you a few other places where they allow speculation. Good luck!

 

[bhobba]

I'm not going to argue with you, but let's make it clear that speculation outside of peer reviewed material is not allowed. If you can't back your statement up with peer reviewed material don't post it. We are mainstream.

To be clear well respected textbooks are fine as well. I only say it because, while obvious, I have had a couple of PM's over the years regarding the issue. Material outside this is allowable in a few circumstances as determined by the Mentors eg arxiv content where it is a small field and that is generally considered the usual form of publication, and where the paper has been cited by many other reputable sources. It really is just common sense actually - but if unsure drop a note to a mentor.

Thanks
Bill

 

[bhobba]

So, you are okay with how physics, gravity in particular, is explained?

All the mentors and science advisers know how gravity is explained - I will even explain it just so you understand the people here are quite knowledgeable, many are doctorates/professors of physics. Rest assured if you want to find our about REAL physics you are in the right place.

Here is the explanation of gravity. Particles move according to the Principle Of Maximal Time - which is just Newtons First Law in general coordinates. This leads to something called the metric guv (a 4X4 matrix) determining the motion of particles. This means guv acts like a field and we should be able to use field theory to see what equations it obeys. This is where a not very well known, but a truly amazing theorem, called Lovelocks Theorem comes in:
https://en.wikipedia.org/wiki/Lovelock's_theorem

This gives the Einstein Field Equations that, similar to Maxwell's Equations describing the electromagnetic field, describes the gravitational field guv. It is: Euv = Tuv. (I am ignoring the so called cosmological constant and use units so that there is not a constant in front of Tuv). Euv, another 4X4 matrix, is called the Einstein tensor and depends on guv as Maxwell's equations depend on the electric and magnetic fields, and Tuv is called the stress energy tensor:
https://en.wikipedia.org/wiki/Stress–energy_tensor.

The Einstein tensor, it turns out, is a measure of space-time curvature so we get that gravity is space-time curvature.

Take my word for it, we have people here that really know just about any area of science or engineering you can imagine. However that is what we discuss, not wild speculation.

Thanks
Bill