Gravitational collapse

[brucep]

Lemaître was a brilliant physicist, but he too was initially dismissed by Einstein.

This kind of nonsense really gets to me. He wasn't the first to propose the universe could be expanding. The Friedmann cosmological metric predicts the universe could be expanding, static, or contracting. The first cosmological metric of GR. He didn't discover the universe was expanding. It was Edwin Hubble, the astronomer, that DISCOVERED the universe is expanding. That's why he gets the credit. I was responding to the 'wiki thing' somebody linked.

 

[Robittybob1]

.... The Friedmann cosmological metric predicts the universe could be expanding, static, or contracting. The first cosmological metric of GR.....

How many other options are there? If I made a prediction I could win or lose the lottery, surely that is barely a prediction. Not in my use of the word prediction in any case.

 

[brucep]

How many other options are there? If I made a prediction I could win or lose the lottery, surely that is barely a prediction. Not in my use of the word prediction in any case.

That's the prediction Friedmann's metric makes. The fact you can't figure out what that means isn't surprising to me. If you can't say something that makes sense go away.

 

[Robittybob1]

That's the prediction Friedmann's metric makes. The fact you can't figure out what that means isn't surprising to me. If you can't say something that makes sense go away.

So is that like saying if the initial conditions are altered we could get any one of the three outcomes? Is that equivalent of saying I will win the lottery if I buy all the tickets, I could win or lose if I bought a few but I won't win if I don't buy any.
Is that a valid prediction?

 

[Tach]

Hmm. Well, perhaps the "discussion" between Tach and hansda has reached the conclusion that Einstein didn't make any mistakes in his original paper, except for assuming the universe was static and unchanging.

There was no "static universe" in the original (1916) Einstein GR papers. I already explained that to hansda.

 

[arfa brane]

There was no "static universe" in the original (1916) Einstein GR papers. I already explained that to hansda.

So when did he add the cosmological term, and why?
Why did he later call it his "greatest blunder"? Why do you get more than a million hits when you google "Einstein static universe"?
Should they all say that Einstein didn't think the universe was static?

 

[Tach]

So when did he add the cosmological term, and why?

I already explained this to hansda: in a paper published a year later, in1917, in order to counter the EFE prediction of an inflationary universe that did not sit well with his intuition.

Why did he later call it his "greatest blunder"? Why do you get more than a million hits when you google "Einstein static universe"?
Should they all say that Einstein didn't think the universe was static?

Why don't you take a class? We have already seen that you aren't doing very well by "learning by Google".

 

[arfa brane]

Why don't you take a class? We have already seen that you aren't doing very well by "learning by Google".

Why don't you shut the hell up? Instead of making the same tired comeback over and over again, thereby displaying either that you have no response because you don't know what you're talking about, or that you just can't be bothered?
Why do you think you have anything to contribute when everyone else thinks you haven't?

Maybe this forum is just a vehicle for sad pathetic people who want to cling to the idea they do have something to say? People like you, for instance.

 

[brucep]

So when did he add the cosmological term, and why?
Why did he later call it his "greatest blunder"? Why do you get more than a million hits when you google "Einstein static universe"?
Should they all say that Einstein didn't think the universe was static?

I think he was like everybody else unsure about the universe. I think he figured out that if the universe was static GR predicted it would collapse without a cosmological constant term in the metric. The physics demanded it.

 

[brucep]

I think he was like everybody else unsure about the universe. I think he figured out that if the universe was static GR predicted it would collapse without a cosmological constant term in the metric. The physics demanded it.

It's interesting to speculate about it. Newton didn't know about Maxwell's equations and Einstein didn't know about Inflation. I'm speculating he called it 'a blunder' because he didn't know about inflation and this universe requires a cosmological constant. If he knew about inflation he would realize it wasn't a mistake but a moment of brilliance. The physics of this universe demanded a cosmological constant. Mind boggling brilliant stuff. Further speculation. Einstein would be stoked about Inflation and the set of 'great' modern experiments. Newton to.

 

[Tach]

Why don't you shut the hell up? Instead of making the same tired comeback over and over again, thereby displaying either that you have no response because you don't know what you're talking about, or that you just can't be bothered?
Why do you think you have anything to contribute when everyone else thinks you haven't?

Maybe this forum is just a vehicle for sad pathetic people who want to cling to the idea they do have something to say? People like you, for instance.

I answered your question, it is not my fault that you keep trying the method of "learn by Google" instead of taking a class or reading a textbook.

 

[arfa brane]

I answered your question,

No you didn't. You gave your personal and somewhat restricted opinion.

it is not my fault that you keep trying the method of "learn by Google" instead of taking a class or reading a textbook.

It isn't my fault that a quick google search usually turns up evidence that your opinion is wrong.

The implication that I or anyone else should trust your opinion instead of google is quite a humorous one. And it's not my fault that you think you're the only person on the planet who can read textbooks..

 

[Tach]

No you didn't. You gave your personal and somewhat restricted opinion.

There is nothing personal in the FACT that the 1916 version predicts an expanding universe and that the 1917 version introduced the cosmological constant.

It isn't my fault that a quick google search usually turns up evidence that your opinion is wrong.

It is not my fault that you are an ignorant who's too lazy to crack open a book.

 

[arfa brane]

It is not my fault that you are an ignorant who's too lazy to crack open a book.

But you can't possibly know that I don't read textbooks. You don't know how lazy I am.

Therefore you are only expressing an opinion, which is all yours. You have no way of knowing that your opinion is correct.
Hence you're just being an asshole.

 

[Tach]

But you can't possibly know that I don't read textbooks. You don't know how lazy I am.

You don't read any books on relativity, you try to get your education, on the cheap , from this forum or from google. You are clearly ignorant on subjects on relativity , yet you argue. It is very simple, really, the 1915 original version of the EFEs (reprised in 1916) looks like this:

$$R_{\mu \nu} - {1 \over 2}g_{\mu \nu}\,R = {8 \pi G \over c^4} T_{\mu \nu}$$

while the 1917 version (reprised in 1922) looks like this:


$$R_{\mu \nu} - {1 \over 2}g_{\mu \nu}\,R + g_{\mu \nu} \Lambda = {8 \pi G \over c^4} T_{\mu \nu}$$

Interestingly enough, the current version has a small, non-zero cosmological constant, so, Einstein made no "blunder" after all. Only crackpots like hansda insist on "Einstein's mistake".

 

[arfa brane]

You don't read any books on relativity, you try to get your education, on the cheap , from this forum or from google.

If you say so. After all, you're the only one capable of seeing "the truth".

You are clearly ignorant on subjects on relativity , yet you argue.

I know I'm ignorant, that's why I read textbooks.
On the other hand, you know everything.

As to your "very simple" explanation: there is plenty of literature about the appearance, disappearance and reappearance of the cosomlogical constant. It's inclusion in the equations is a matter of historical record; your interpretation of that history is just that, an interpretation.
Otherwise, as usual, you have nothing to contribute.

So, I'm going to be ignoring you, don't know about anyone else. Mostly what you have to contribute is classified as trolling, which means you intend to inflame a discussion, demean others and generally act like a douchebag.
And that's all I have to say about that . . . (because I won't be saying anything about your contributions again, or bothering to read them).

I mean, post away by all means, just be aware that you'll be talking to yourself if you address any of them to me.

Get fucked, etc.

 

[hansda]

I think he was like everybody else unsure about the universe. I think he figured out that if the universe was static GR predicted it would collapse without a cosmological constant term in the metric. The physics demanded it.

I wonder, why TACH is not able to understand this simple point.