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Gravity

Scientific discovery and discussion
scotia
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Re: Gravity

#188280

Postby scotia » December 20th, 2018, 11:30 am

colin wrote:the equations necessary to use general relativity to make predictions are said to be among the hardest in physics, it takes years of study to be able to make sense of a few blackboards worth of scribbles.

Eddington was one of the foremost proponents of Einstein's General Relativity theory - and his experimental work in 1919 was one of the earliest confirmations of a General Relativity prediction . A story is told (hopefully not apocryphal) of him being interviewed, where the interviewer suggested that there were only three people in the world who understood General Relativity - and the response was "I'm trying to think who the third person could be".
Maybe that's why I didn't follow up my course on Special Relativity ( a lot simpler) with a course on General Relativity.

colin
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Re: Gravity

#188320

Postby colin » December 20th, 2018, 12:59 pm

Ah but the question I ask is...is it that hard to understand General Relativity or is it hard to be able to use the equations necessary to be able to make practical use of the theory, are we not confusing one with the other.
After all did not Einstein 'understand' general relativity before any one developed the equations necessary to use it?

XFool
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Re: Gravity

#188407

Postby XFool » December 20th, 2018, 4:48 pm

Stonge wrote:Science cannot explain, it can only describe.

Well... yes and no!

A systematic description of phenomena, based on some general principle, is a "description" but it is also surely an "explanation" of those phenomena? Of course, it is based on whatever principle is being used to systematise the explanation. It doesn't "explain" that principle in itself. Though somebody may later comes along and explain that in terms of some more general and fundamental principle, etc.

Also, what is new in a scientific description/explanation is that it can explain previously inexplicable phenomenon and even predict new, previously unobserved phenomena.

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Re: Gravity

#188412

Postby XFool » December 20th, 2018, 4:58 pm

colin wrote:Ah but the question I ask is...is it that hard to understand General Relativity or is it hard to be able to use the equations necessary to be able to make practical use of the theory, are we not confusing one with the other.

I tend to agree - possibly foolishly.

The mathematics of Special Relativity is elementary, that of General Relativity isn't (and pretty well unknown to me). Yet, I have never really felt I genuinely understood SR, in the intuitive sense. Whereas GR, once you accept the idea of matter distorting the geometry of spacetime, does seem to make sense in an intuitive way. I like those rubber sheet analogies, they feel very convincing!

Of course, I realise this everyday intuitive notion of GP may be far from the understanding of professionals.

Dod101
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Re: Gravity

#188418

Postby Dod101 » December 20th, 2018, 5:11 pm

XFool wrote: I like those rubber sheet analogies, they feel very convincing!.


As in Topology?

Dod

stewamax
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Re: Gravity

#189224

Postby stewamax » December 24th, 2018, 7:45 pm

XFool wrote:
colin wrote:Ah but the question I ask is...is it that hard to understand General Relativity or is it hard to be able to use the equations necessary to be able to make practical use of the theory, are we not confusing one with the other.

The mathematics of Special Relativity is elementary, that of General Relativity isn't (and pretty well unknown to me). Yet, I have never really felt I genuinely understood SR, in the intuitive sense. Whereas GR, once you accept the idea of matter distorting the geometry of spacetime, does seem to make sense in an intuitive way. I like those rubber sheet analogies, they feel very convincing!

Einstein himself had difficulty mastering the necessary maths of covariance - roughly the principle that the relationships between moving bodies held within all frames of reference if they held within any of them - and looked to his friend Marcel Grossmann for tuition in tensors.
Google for "Lost in the Tensors: Einstein's Struggles with Covariance Principles" for more.


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