# Correlating Newtonian Model with Einstein's GR

Discussion in 'Alternative Theories' started by hansda, May 8, 2017.

1. ### NotEinsteinValued Senior Member

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Erm, because 8pi is the right value, and 100000 and 0.0000001 are not?

What do you mean by that exactly? If you mean that using those other values instead of 8pi also will lead to Newtonian physics, you would be incorrect: the resulting formulas would be similar, but off by various constant factors. In other words, you do not end up with Newtonian physics.

3. ### The GodValued Senior Member

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You did not get, your dimensional analysis is true with any dimension less constant, if you find why 8pi, then it will lead you to Newtonian.

5. ### NotEinsteinValued Senior Member

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The only explanation I've been able to find so far is that it's 8pi because then it leads to Newtonian physics; it's a normalization of the theory in the Newtonian limit.

I find that explanation quite unsatisfying. Anybody know of a better, more fundamental explanation?

But that's actually neither here nor there. Your original comment was:
This has now been conclusively debunked by the link to that derivation I gave above. You can only argue that the choice of normalization is arbitrary, but it obviously matches what we see in nature. We can perhaps not derive it from the equations themselves, so we call it a "constant of nature" (for now).

In fact, that's exactly what happens in Newtonian physics with G. It's just a normalization parameter of the model that we set to a value to make the theory give answers that match reality.

7. ### The GodValued Senior Member

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I will wait for answer to your question in the first part of your above post. More or less you have hit the Bull's eye, quite close.

8. ### NotEinsteinValued Senior Member

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Ah, so you now agree with me that one can derive Newtonian physics from GR. Good. Going back on topic: what's your opinion on hansda's claim that his text correlates Newtonian physics with GR?

In fact, perhaps hansda can explain to us where this factor of 8pi exactly comes from!

9. ### The GodValued Senior Member

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No, no....but if that pleases you after you made lot of dramatics in last few posts.

You read my first post again and get back what I said.

10. ### NotEinsteinValued Senior Member

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So you have found a mistake in the derivation I posted a link to? Please point me to it!

Ok:

Well, both have to actually describe reality; their answers have to be right in order for the model to be useful. If you call that a forced connection, then yes.

This is clear: there has to be a constant there, because of dimensional analysis. The value cannot be derived from the theory (unless somebody can demonstrate otherwise), so we have to select some value that makes it match what we see in reality. This constant happens to match 8piG, so instead of inventing another constant, we simply write 8piG. Quite straight-forward, if you ask me.

Incorrect; it's due to reality.

This I already responded to in post #43.

Now would you please respond to the question I asked you in post #45?

11. ### The GodValued Senior Member

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I am not speaking in support of Handsa, so I cannot say anything about him.

Before you continue with your song and dance, why don't you seek answer for the question you raised in your #43.

You do not even understand that both GR and Newtonian are conceptually different, still support the view that GR in limiting case gives Newtonian. This was a forced necessity to flick G not your funny dimensional analysis excuse. Ok, I will give you one more hint ...list down three differences between GR and Newtonian.

12. ### NotEinsteinValued Senior Member

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I see you've ignored the first part of my post. May I conclude you actually haven't found a mistake in the derivation I posted, and that it thus is a good example of how Newtonian physics can be derived from GR?

So you haven't read his text, where he (allegedly) makes the connection between GR and Newtonian physics?

You haven't bothered to read hansda's text, so you are also guilty of this.

And I actually have been looking for this; I just haven't found it. And clearly, you don't have an answer either.

Please refrain from making unfounded assumptions about what I understand and what I don't. Even if they are conceptually different, that doesn't mean you can't derive one from the other.

You have shown a complete lack of arguments in support of the claim that it doesn't. In fact, you've dodged that question in this very post of yours.

Please give an argument as to why the derivation I linked is incorrect.

"My" funny dimensional analysis? Please look it up; it's a well-establish principle in science, so it's not mine. But please explain to me why dimensional analysis is an "excuse".

No, you are the one claiming they are different; the burden of proof is on you. You list three differences between GR and Newtonian physics.

13. ### The GodValued Senior Member

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Ok, they are same, if that pleases you and you can conclude anything you like. "Shrug"

14. ### NotEinsteinValued Senior Member

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I never said that. Please stop putting words in my mouth.

15. ### NotEinsteinValued Senior Member

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I have managed to find this, by Sean Carroll: http://www.preposterousuniverse.com/blog/2014/03/13/einstein-and-pi/

It actually explains it quite nicely! Mystery solved.

Now back on-topic: hansda, why have you misled me?

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18. ### originHeading towards oblivionValued Senior Member

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The God acts like the classic anti-science troll, he likes to argue from a position of ignorance. Waste of time...

19. ### The GodValued Senior Member

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So what's your point? What are you opposing?

Anyway, find out the answer of these questions for yourself...

True or False questions for you.

1. Newtonian theory has nothing to do with geometry of spacetime.
2. GR is about geometry of spacetime.
3. In GR, the gravity is not a force.
4. In Newtonian the gravity is a force.
5. In GR the speed of gravity is c.
6. In Newtonian the speed of gravity is infinite.

Last Hint : actually Newtonian was used to get G (and other factors in GR), because Newtonian was and still the reality in general usages.

20. ### NotEinsteinValued Senior Member

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Judging on his/her behavior in the last couple of posts I get that feeling too, but I'll just engage him/her as (s)he is, and let the moderators worry about it.

21. ### The GodValued Senior Member

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Oh, so origin, contribute pl. Back to one liners?

Why not attempt questions in #56. Let me see what you know.

22. ### The GodValued Senior Member

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No, except two less than upto the mark links, your argument is nothing but follow the authority.

You are still confused why 8piG.

23. ### NotEinsteinValued Senior Member

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My point is that hansda misled me when he said that his TOE explained the connection between Newtonian physics and GR.
My other point is that Newtonian physics can be derived from the theory of relativity.

False. Originally of course it wasn't brought up, but then the theory of relativity showed us about the geometry of spacetime, and we started interpreting Newtonian theory in that light too.

True, though perhaps not solely.

True.

True.

True.

Unclear. Often it's taken as such, but I don't think it's a requirement of it. The limited speed of gravity was known well before the theory of relativity came along, and I don't remember scientists claiming this debunk Newtonian physics.

But that has no bearing on whether one can derive Newtonian physics from GR. In fact, it signals the two are connected, in that in specific cases Newtonian physics is "good enough". I.e., GR is a more general case of Newtonian physics.