Any physics majors here? Discussion on general relativity.

[stankeylegjones]

First, I understand what everyone is saying about general relativity and how gravity is not a true force and due to mass curving spacetime, when falling in a gravitation field we are in fact an inertial frame. Obviously I only understand this as a layman’s level.

Let me try to simplify my question.

I am a physicist from 1850. I assert, because of the unique nature of of gravitational mass being the same as inertial mass, a closed system in free fall can be treated as if it is an inertial frame of reference. I wouldn’t asset that it is but that it can be treated as such.

That professor’s claim is perfectly valid and consistent with known science at that time. So I think people are wrong when they claim that treating freefall as an inertial frame of reference somehow breaks Newtonian/Galilean physics. It is just a quirk and the root of that quirk is the equality of gravitational mass and inertial mass.

Even if it might not be Einstein’s thought process, I think the first big question is why the quirk which leads to everything else.

But, more importantly, I don’t agree with the proposition that the falling man thought experiment somehow breaks the idea of Galilean frames of reference. It just means that that quirk exists.

It wasn't noticing this "quirk," it was reinterpreting this "quirk" as the key to a new framework of gravity. According to Newton, free fall mimics an inertial frame by the assumption of m_in = m_g; gravity is still a force. According to Einstein, gravity is not a force, it's curvature of spacetime, and free fall is inertial motion.

Let me know if that helps, or if I can say more/different things, and what you next question is.

 

[stankeylegjones]

Here's a good lecture/talk about the history:

 

[superrific]

What derivation are you referring to? I didn’t see any in your post. Did you modify it?

There was no reason to go into the electroweak force. In my writing I'm utilizing a lot of QFT but I am most interested in the Higgs interaction. The spontaneous symmetry issue sits in the background and I've not taken the time to understand it 100%. No idea why I tried to bring it in.

 

[stankeylegjones]

There was no reason to go into the electroweak force. In my writing I'm utilizing a lot of QFT but I am most interested in the Higgs interaction. The spontaneous symmetry issue sits in the background and I've not taken the time to understand it 100%. No idea why I tried to bring it in.

Ah, I see. How far along are you in your novel?

 

[superrific]

Ah, I see. How far along are you in your novel?

Kinda stalled out for a while. Too much stress in personal life and world affairs. Makes it hard to concentrate. Sitting down at my computer is like trying to concentrate in a parking lot, except translated into mental space. I'm making progress but it's been very slow for a while.

I am taking this opportunity to review what exactly symmetry means. It's a slippery concept for me because it's not how I learned it. We talked about whether I could relearn complex math at my age; whatever the answer to that may be, it's true that I have a much harder time retaining it. I've read about gauge symmetry twice and I understood it both times (I tested myself by making predictions) -- but then I sort of forgot it. I don't know how to explain. When I was younger, once I learned and understood something, I knew it cold. I mean, over a long time I can forget, but even things I learned when I was younger are fresher in my mind than things I learned at this age, say, two months ago. If I'm not using something consistently these days, it's harder to recall it.

Anyway, I realize now that I was earlier confusing global and local symmetries. I've made that mistake before. A lot of the terminology in this space is really not intuitive. Gauge symmetry just does not sound like what it means. Pair that with the math notation -- i.e. the super-abstract like SU(2) x U(1) -- and it's hard for this middle aged man to keep track of it all.