Was Newton wrong?
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29-05-2013, 04:24 AM
Was Newton wrong?
Often you get on a forum and some people are claiming that Einstein proved Newton wrong. Well, not exactly. Einstein Field Equations reduces to Newton's law of gravity at low gravity and low velocity. I've made the calculations available. So any time you get to meet those people, you can refer to it.

Is Newtonian Gravitational Fields Valid Within General Relativity?
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29-05-2013, 09:54 AM
RE: Was Newton wrong?
To commemorate Newton, we should have t-shirts showing:

Rμν = (8πG/c^4)[Tμν – ½Tgμν] → ∇^2φ = 4πGρ
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29-05-2013, 10:18 AM
RE: Was Newton wrong?
Looks like Greek to me. Math and calculations... not my finer suit. But the basic science I do understand.

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29-05-2013, 10:27 AM
RE: Was Newton wrong?
Indeed, I always explain this with the law of cosines and pythagora's theorem: Einstein's equations are to Newton's law as the Law of cosines is to pythagora's theorem Big Grin

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29-05-2013, 12:12 PM
RE: Was Newton wrong?
Yeah, Newton was wrong about all kinds of things. Some of it due to lack of knowledge (the nature of light, for example). Some of it because he was kind of a jerk (suppressing Hooke's work after taking over the Royal Society set back geology by decades, among other fields). Most of it due to the silly religious convictions he held (there's a reason nobody talks about his later years as a crazy old man with his alchemy and his prophecies).


Er, but anyway. I've read the post now. Someone saying Einstein "proved Newton wrong" is indeed silly. Rather, he proved Newton incomplete - but still valid in many cases, as indeed you show. I'm not sure the distinction is necessarily important; I guess it would depend on the conversation.

Are you by chance an astrophysicist, zaybu? They're the only ones I've seen regularly treat gravity as a potential. In quantum mechanics we can just ignore it 99.9% of the time.

(29-05-2013 10:18 AM)smidgen Wrote:  Looks like Greek to me.

There are as many Greek characters as Latin there, to be sure...
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29-05-2013, 02:59 PM
RE: Was Newton wrong?
(29-05-2013 12:12 PM)cjlr Wrote:  Yeah, Newton was wrong about all kinds of things. Some of it due to lack of knowledge (the nature of light, for example). Some of it because he was kind of a jerk (suppressing Hooke's work after taking over the Royal Society set back geology by decades, among other fields). Most of it due to the silly religious convictions he held (there's a reason nobody talks about his later years as a crazy old man with his alchemy and his prophecies).


Er, but anyway. I've read the post now. Someone saying Einstein "proved Newton wrong" is indeed silly. Rather, he proved Newton incomplete - but still valid in many cases, as indeed you show. I'm not sure the distinction is necessarily important; I guess it would depend on the conversation.

Are you by chance an astrophysicist, zaybu? They're the only ones I've seen regularly treat gravity as a potential. In quantum mechanics we can just ignore it 99.9% of the time.

(29-05-2013 10:18 AM)smidgen Wrote:  Looks like Greek to me.

There are as many Greek characters as Latin there, to be sure...

I guess alchemy and religion is always a bad mix. LOL.

Problem often I get on the web from theists is the old miscontrued argument that scientific theories are disproved by other theories, hence Einstein disproved Newton. Therefore, science is unreliable, but my religion isn't... that kind of nonsense. So trying to dispel this is like trying to move mountains with these theists.

No, I'm not into astrphysics. I'm more into QFT, and lately I've been delving into QFT in curved spacetime, which has forced me to brush up and sharpen my knowledge of GR.
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29-05-2013, 05:25 PM
RE: Was Newton wrong?
(29-05-2013 02:59 PM)zaybu Wrote:  I guess alchemy and religion is always a bad mix. LOL.

Problem often I get on the web from theists is the old miscontrued argument that scientific theories are disproved by other theories, hence Einstein disproved Newton. Therefore, science is unreliable, but my religion isn't... that kind of nonsense. So trying to dispel this is like trying to move mountains with these theists.

No, I'm not into astrophysics. I'm more into QFT, and lately I've been delving into QFT in curved spacetime, which has forced me to brush up and sharpen my knowledge of GR.

Newton totally went off the rails in his later years. By all accounts he managed his political appointments well enough, but he sure wasn't doing any science. Well, except for letting personal relationships screw with some of his rivals, most notably (as I mentioned) the contemporary and equally brilliant Hooke.

Ah, right - the old "someone was wrong once, therefore everything is wrong always" argument. The best tack there is probably pointing out the changes in religious doctrine over time. Not that that'll help against the True Believer.

There are those theories which are proven wrong, but you'll know as well as I do that's not usually the case. A theory which only describes a narrow range of situations never stops describing those (quantum and relativistic descriptions should have a classical limit - that's one of our best tests for consistency!). And so that's then supplanted by something more widely applicable.

So you are a physicist, then? I am only a new grad student, you see. My textbooks on quantum field theory are firmly at the bottom of my "uh, maybe I'll figure that out later" pile.
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30-05-2013, 05:07 AM
RE: Was Newton wrong?
(29-05-2013 05:25 PM)cjlr Wrote:  My textbooks on quantum field theory are firmly at the bottom of my "uh, maybe I'll figure that out later" pile.

If I have one suggestion that would be: pull out that QFT book and start digging. There is nothing that compares to it. I would further suggest Peskin and Schroeder for QFT in flat spacetime, and Parker for QFT in curved spacetime. I garantee your life won't be the same. Smile
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30-05-2013, 07:18 PM
RE: Was Newton wrong?
(29-05-2013 02:59 PM)zaybu Wrote:  No, I'm not into astrphysics. I'm more into QFT, and lately I've been delving into QFT in curved spacetime, which has forced me to brush up and sharpen my knowledge of GR.

Working towards a theory of quantum gravity are we?

2.5 billion seconds total
1.67 billion seconds conscious

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02-06-2013, 08:08 AM
RE: Was Newton wrong?
(30-05-2013 07:18 PM)Adenosis Wrote:  
(29-05-2013 02:59 PM)zaybu Wrote:  No, I'm not into astrphysics. I'm more into QFT, and lately I've been delving into QFT in curved spacetime, which has forced me to brush up and sharpen my knowledge of GR.

Working towards a theory of quantum gravity are we?

No, if anything, I see gravity is more like a fictitious force - like a coriolis force is in a rotating moving frame. In the case of gravity, it is fictitious in a curved spacetime.
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