What made Einstein think the universe was steady?

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I have two questions.

Why did Einstein think the Universe was steady (unchanging)? What were his motives?

And two:
To make his universe steady (static) Einstein added the cosmological constant to his Theory of Relativity. Later he said that adding the cosmological constant was his biggest blunder. Why was it such a blunder?
 

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  • #2
epenguin
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Wasn't it just a prejudice, a habit of thought? Before relativity no other possibility had ever entered anyone's head, there was no reason to, and in a purely mechanical Newtonian Universe would I be right in saying the concept would be meaningless or an unnecessary multiplication of concepts? If everything including your measuring instruments expands or does anything else there are no consequences so forget it?
 
  • #3
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Wasn't it just a prejudice, a habit of thought? Before relativity no other possibility had ever entered anyone's head, there was no reason to, and in a purely mechanical Newtonian Universe would I be right in saying the concept would be meaningless or an unnecessary multiplication of concepts? If everything including your measuring instruments expands or does anything else there are no consequences so forget it?

Were there no other thoughts/reasons? Like for example religious ones?
Is there a site that explains it in just a few sentences if no one here can tell me?

And please don't forget to answer my second question!
 
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  • #4
Nabeshin
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Were there no other thoughts/reasons? Like for example religious ones?

It seems to me to be a holdover of the notion of a cosmos which is static and eternal. First, we thought this was true of the objects in our solar system. But then we found sunspots, storms on jupiters, and active volcanoes on moons. Perhaps, then, the galaxy as a whole is static and eternal? Well, we knew that it rotated, but the thing is -- before roughly the time of Hubble, we thought the galaxy was the entire universe. We had no evidence for thinking the "nebulae" in the sky were very far away. We did not really have any evidence that the structure as a whole was expanding or contracting. So it was both an extension of earlier prejudices and a complete lack of observational evidence to the contrary.

Of course, he called it his "biggest blunder" because it is a rather ugly blemish on the equations of general relativity. It's a rather ad-hoc parameter, and it's value must be chosen extremely precisely to lead to a static universe anyways (and even then, it is unstable!). So it is a blunder because Einstein failed to believe his own beautiful theory and instead caved to age-old prejudices about a static cosmos.
 
  • #5
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I have two questions.

Why did Einstein think the Universe was steady (unchanging)? What were his motives?

And two:
To make his universe steady (static) Einstein added the cosmological constant to his Theory of Relativity. Later he said that adding the cosmological constant was his biggest blunder. Why was it such a blunder?

To his credit (and I don't have a source for this, but read it somewhere during research on another subject) that Einstein actually inquired of several astronomers if there was any indication of expansion - unfortunately he asked the wrong astronomers - had he chosen sliper and a few others that were beginning to measure the redshifts, GR may have involved differently. I think it was Steven Weinberg that said: "his greatest blunder was in doing away with the cosmological constant"
 
  • #6
Chalnoth
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Of course, he called it his "biggest blunder" because it is a rather ugly blemish on the equations of general relativity. It's a rather ad-hoc parameter, and it's value must be chosen extremely precisely to lead to a static universe anyways (and even then, it is unstable!). So it is a blunder because Einstein failed to believe his own beautiful theory and instead caved to age-old prejudices about a static cosmos.
Well, I wouldn't say it's an ad-hoc parameter. If you look at the Lagrangian derivation of Einstein's equations, there simply isn't any reason not to put the cosmological constant in there. To this date, nobody has found any theoretical reason to exclude it. The best argument amounts to: observationally it has to be very small, therefore it must be zero.

I think the real blunder was just that it had to take an extremely precise value, and left an unstable universe. There was no blunder in proposing it at all.
 
  • #7
phyzguy
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I think the real blunder was just that it had to take an extremely precise value, and left an unstable universe.
I think this is the key point. While the cosmological constant allows a solution where the attraction of gravity is balanced by the repulsion of the cosmological constant, it is an unstable solution, and it is very difficult to believe that our universe is "balanced on a knife edge". So adding the cosmological constant didn't even really solve the problem Einstein set out to solve. I think this is why he considered it a a blunder.
 
  • #8
Nabeshin
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If you look at the Lagrangian derivation of Einstein's equations, there simply isn't any reason not to put the cosmological constant in there.

Correct me if I'm wrong, I very well might be, but didn't Einstein not arrive at his equations in this manner? Specifically, I was under the impression he sort of "heuristically" arrived at what the simplest form of the covariant equations must be, rather than deriving them from a lagrangian. From this point of view, throwing in a constant times the metric has no physical interpretation or meaning (certainly, at least, it did not in Einstein's day), which is why I think it was ad-hoc.

From the lagrangian formalism, of course, it's strange to exclude it.

Does anyone have a clarification on the exact route Einstein took to his equations? I am aware that Hilbert was doing similar work at the same time, but from the lagrangian perspective...
 
  • #9
Chalnoth
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Correct me if I'm wrong, I very well might be, but didn't Einstein not arrive at his equations in this manner? Specifically, I was under the impression he sort of "heuristically" arrived at what the simplest form of the covariant equations must be, rather than deriving them from a lagrangian. From this point of view, throwing in a constant times the metric has no physical interpretation or meaning (certainly, at least, it did not in Einstein's day), which is why I think it was ad-hoc.
I believe this is correct. It is my understanding that the Lagrangian derivation didn't come until later.

From the lagrangian formalism, of course, it's strange to exclude it.

Does anyone have a clarification on the exact route Einstein took to his equations? I am aware that Hilbert was doing similar work at the same time, but from the lagrangian perspective...
Sorry, I'm just not that familiar with the original derivation.
 
  • #10
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I think this is the key point. While the cosmological constant allows a solution where the attraction of gravity is balanced by the repulsion of the cosmological constant, it is an unstable solution, and it is very difficult to believe that our universe is "balanced on a knife edge". So adding the cosmological constant didn't even really solve the problem Einstein set out to solve. I think this is why he considered it a a blunder.

It is an unstable solution for a static universe - its a beautiful solution for an accelerating universe - if the cosmological constant is viewed as defining the expansion acceleration, a la de Sitter, then the inertial reaction of masses to this isotropic global acceleration is the gravitational counter force "gravity" - in other words G derives from the cosmological constant ... the two accelerations will always be intrinsically counterpoised in an accelerating universe
 
  • #11
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Yogi, I work with a Yogi who is also a radio design engineer up here in Northern NY state. That isnt you is it?
 
  • #12
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Yogi, I work with a Yogi who is also a radio design engineer up here in Northern NY state. That isnt you is it?

Sorry, not the same fellow. I am an ex engineer, Yogi is a stage name here on PF. Not even smarter than the average bear.
 
  • #13
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Ok thanks Yogi, it seemed unlikely, but you never know.
I am almost an "x" RF Designer here.

Regards
Bo Bo!
 
  • #15
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I believe this is correct. It is my understanding that the Lagrangian derivation didn't come until later.

I disagree, if I remember correctly Hilbert actually came up with the Einstein equations a little before Einstein, using the Lagrangian derivation and Einsteins previous work. But since Einstein did all the heavy lifting, they are attributed only to him.


The the "blunder" part: We only know that Einstein said that to Gamow. According to my knowledge it remains unclear weather Einstein regretted making such an ad-hoc modification or weather he was disappointed that he didn't have enough confidence in his equations to predict an expanding universe himself. I like to believe in the latter.

Again, as said in the other thread, for this topic I recommend the book "Big Bang" by Simon Singh to the OP.
 
  • #16
Chalnoth
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I disagree, if I remember correctly Hilbert actually came up with the Einstein equations a little before Einstein, using the Lagrangian derivation and Einsteins previous work. But since Einstein did all the heavy lifting, they are attributed only to him.
Ah, interesting. My history of relativity is a little bit sketchy. Looking through what I could find on Wikipedia, it looks like Einstein was pursuing one path, and Hilbert another. It looks like Einstein is largely credited with General Relativity in part because he produced correct equations earlier, in part because he connected those equations to experiment (specifically, the advance of the perihelion of Mercury). There may have been other, non-science-related reasons why Einstein is primarily credited.

The the "blunder" part: We only know that Einstein said that to Gamow. According to my knowledge it remains unclear weather Einstein regretted making such an ad-hoc modification or weather he was disappointed that he didn't have enough confidence in his equations to predict an expanding universe himself. I like to believe in the latter.
Well, I, for one, don't care all that much what Einstein himself was thinking in that comment. From the much clearer view of the theory we have available to us today, there is a clear mistake there, that assuming a static universe and producing an ad-hoc and unstable solution to it. Whether that is or is not what he thought his mistake was is, in my mind, pretty much irrelevant.
 

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