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An issue I have with GR physics versus Newtonian physics


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#41 Lord Antares

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Posted 13 January 2017 - 10:09 PM

If there is no mechanism, then that changes the perspective a lot. The expansion would negate this notion of everything falling towards the center of mass, I would think.

So Newton could be wrong, right?

 

I know it doesn't matter what people think. I was trying to make the following point:

you said his theory would only be correct if the universe was infinite. Most people consider his theory to be correct. Most people consider the universe to be finite. That is a contradiction.


Edited by Lord Antares, 13 January 2017 - 11:08 PM.

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#42 swansont

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Posted 13 January 2017 - 11:26 PM

Considering whether a model is correct is based on evidence. Opinion about the universe being infinite or finite is not.
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#43 Strange

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Posted 14 January 2017 - 01:12 AM

If there is no mechanism, then that changes the perspective a lot. The expansion would negate this notion of everything falling towards the center of mass, I would think.

So Newton could be wrong, right?

 

 

There can be no expansion if Newton is correct. Therefore you can't use expansion to argue against (or for) Newton's ideas.

 

 

 

you said his theory would only be correct if the universe was infinite. 

 

No. Completely wrong.

 

If his theory were correct then the universe must be finite infinite.

 

 

 

Most people consider his theory to be correct. Most people consider the universe to be finite. That is a contradiction.

 

1. His theory is "wrong".

 

2. What evidence do you have that "most people consider the universe to be finite"?

 

3. As that belief is not based on any evidence it cannot conflict with science.

 

You might as well say that most people's favourite colour is red and this conflicts with the sky being blue. Opinions are not evidence. (Especially when I have no reason to believe that ,most people have this optinion.)


Edited by Strange, 14 January 2017 - 10:49 AM.

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#44 Lord Antares

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Posted 14 January 2017 - 10:33 AM

There can be no expansion if Newton is correct. Therefore you can't use expansion to argue against (or for) Newton's ideas.

 

How so? If there can be no expansion if Newton is correct, then if there is expansion, I car argue against his ideas, surely.

 

 

No. Completely wrong.

 

If his theory were correct then the universe must be finite.

 

But I am only saying this because you said:
 

 

Newton demonstrated exactly the opposite: that if his theory were correct, then the universe would have to be infinite.

 

Stop confusing me. How am I supposed to communicate with you if you keep giving me conflicting information. Maybe you meant something else, but it is not clear to me at all.

 

 

1. His theory is "wrong".

 

2. What evidence do you have that "most people consider the universe to be finite"?

 

3. As that belief is not based on any evidence it cannot conflict with science.

 

You might as well say that most people's favourite colour is red and this conflicts with the sky being blue. Opinions are not evidence. (Especially when I have no reason to believe that ,most people have this optinion.)

 

No. That's a ridiculous analogy, especially because you misunderstood what I was trying to say. But it is irrelevant, since you are now saying that his theory is wrong.

 

The only thing that you are right about is that I don't have evidence for point number 2. I spoke from experience; I've heard/read that the universe is finite more times than not, but that is not evidence.


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#45 Strange

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Posted 14 January 2017 - 10:53 AM

How so? If there can be no expansion if Newton is correct, then if there is expansion, I car argue against his ideas, surely.

 
 
Indeed. And that is what Einstein did: show how Newton's theory doesn't work in all cases by coming up with a better one.
 

Stop confusing me. How am I supposed to communicate with you if you keep giving me conflicting information. Maybe you meant something else, but it is not clear to me at all.

 
I apologise. Another typo. 
 
I meant to say: If his theory were correct then the universe must be infinite.
(Whereas you said "his theory would only be correct if the universe was infinite". This is a logical fallacy called "affirming the consequent".)

 

 

 

I spoke from experience; I've heard/read that the universe is finite more times than not, but that is not evidence.

 

I would guess I have heard about the same number of people insist it is finite and infinite. The evidence doesn't rule either out.


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#46 Lord Antares

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Posted 15 January 2017 - 12:46 AM

 

I meant to say: If his theory were correct then the universe must be infinite.
(Whereas you said "his theory would only be correct if the universe was infinite". This is a logical fallacy called "affirming the consequent".)

 

I see what you mean. I didn't intend to say that, it was just a wrong choice of wording, I guess.

 

 

 I would guess I have heard about the same number of people insist it is finite and infinite. The evidence doesn't rule either out.

 

One thing I really don't understand is how could the universe be infinite and expanding. The only way I can reconcile the expansion of the universe with an infinite universe is if the universe itself wasn't expanding, but if matter was simply getting further apart. But I would be completely baffled as to why this would be happening.


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#47 StringJunky

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Posted 15 January 2017 - 01:17 AM

 

I see what you mean. I didn't intend to say that, it was just a wrong choice of wording, I guess.

 

 

 

One thing I really don't understand is how could the universe be infinite and expanding. The only way I can reconcile the expansion of the universe with an infinite universe is if the universe itself wasn't expanding, but if matter was simply getting further apart. But I would be completely baffled as to why this would be happening.

Perhaps you are trying to visualise an outer edge to an infinite universe when you ought to just consider there is an increase in distance between cosmological groups that are not gravitationally bound; think locally rather than globally.


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#48 Lord Antares

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Posted 15 January 2017 - 01:45 AM

Yes, that's what I meant when I said 

 

The only way I can reconcile the expansion of the universe with an infinite universe is if the universe itself wasn't expanding, but if matter was simply getting further apart.

 

But why would this be happening?


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#49 Strange

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Posted 15 January 2017 - 08:43 AM

One thing I really don't understand is how could the universe be infinite and expanding. The only way I can reconcile the expansion of the universe with an infinite universe is if the universe itself wasn't expanding, but if matter was simply getting further apart. 

 

 

That's about it. It may be easier to think of it as a decrease in density rather than expansion. 

 

Here is an analogy: imagine the number line with all the integers going off to infinity (0, 1, 2, 3 ...). Now if you double all the numbers then they are twice as far apart (0, 2, 4, 6, ...) but the line still extends to infinity.

 

 

 

But I would be completely baffled as to why this would be happening.

 

John Baez's page has a good explanation. He explains it clearly enough that I think you can get something out of it even if the math goes completely over your head.

http://math.ucr.edu/.../baez/einstein/


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