Was Einstein’s “cosmological constant” a correction/corrective mathematical component for expansion or collapse of the universe?
I understand that his General Theory of Relativity predicted an expansion of the universe (which he later found out to be true after his observations in the US) but went along with the prevailing scientific opinion of the day that the universe was static.
It turns out also that the “cosmological constant” is useful to astrophysicists today. Perhaps someone can tell me why.
I look forward to your feedback.
davidmich
His original theory without the Cosmological Constant wasn’t necessarily expanding, but it was certainly dynamic in some way. Without the CC, you get a universe with a negative acceleration: This might be one that’s expanding but slowing down, or one that’s contracting and speeding up, or one that’s momentarily between expansion and contraction, but it won’t be a static one. A cosmological constant allows for the possibility of a balanced universe, which could stay the same size indefinitely.
The difficulty here is that it’s an unstable balance, like a pencil balanced on its tip. If a fly sneezes in such a universe, it’ll upset the balance, and the universe will either start collapsing anyway, or it’ll start expanding without bound, at an ever-increasing rate.
Which brings us to the present state of the art. A variety of independent measurements have all shown that the Universe we live in is, in fact, expanding at an ever-increasing rate. A cosmological constant, or something like it, (nowadays usually called “dark energy”) appears to be the best explanation for this behavior. In fact, it appears to be more than twice as significant as all of the matter in the Universe combined, including the dark matter.
“His original theory without the Cosmological Constant wasn’t necessarily expanding, but it was certainly dynamic in some way. Without the CC, you get a universe with a negative acceleration: This might be one that’s expanding but slowing down, or one that’s contracting and speeding up, or one that’s momentarily between expansion and contraction, but it won’t be a static one. A cosmological constant allows for the possibility of a balanced universe, which could stay the same size indefinitely.”
Chronos, what is you opinion of Walter Isaacson’s biography of Einstein. I find it oversimplified in places and possibly wrong in others.
Walter Isaacson “Einstein” p. 254
"To keep the matter in the universe from imploding, Einstein added a “repulsive"force:a little addition to his general relativity equations to counterbalance gravity in the overall scheme”.
Is Isaacson wrong or giving overgeneralized/incomplete information here?
p.255
"Later, when it was discovered that the universe was in fact expanding, Einstein would call it his “biggest blunder”.
This is debatable. Any thoughts on that?
"Astrophysicist and author Mario Livio can find no documentation that puts those words into Einstein’s mouth (or, for that matter, his pen). Instead, all references eventually lead back to one man, physicist George Gamow, who reported Einstein’s use of the phrase in two sources: his posthumously published autobiography My World Line (1970) and a Scientific American article from September 1956.
Here the CC is referred to as:
"repulsive force to counteract the gravitational attraction that otherwise would make the universe collapse. " Is this wrong?
"repulsive force to counteract the gravitational attraction that otherwise would make the universe collapse. "
The idea of an expanding universe was first proposed in 1927 by the astronomer Georges-Henri Lemaître. Although Lemaître’s calculations showed that an expanding universe was consistent with Einstein’s general relativity theory, Einstein disagreed and reportedly told Lemaître, “Your math is correct, but your physics is abominable.” Einstein still held the traditional belief that the universe is a static “firmament,” as implied in the Bible and most other scriptures that present creation myths. “Static” here does not mean that objects are all at rest. They are moving about, but their average distance apart stays the same.
Victor J. Stenger
Einstein had inserted into his gravitational equation a factor called the cosmological constant that provided a …
repulsive force to counteract the gravitational attraction that otherwise would make the universe collapse.
…Although the cosmological constant is often referred to as a “fudge factor,” that is a misnomer. Such a constant is required in Einstein’s equation, although no value is given for it. If positive, it produces a gravitational repulsion. If negative, we have an attraction added to that of normal gravity.
I don’t think Isaacson was wrong there. Einstein’s CC acted just as we see it today, as a small repulsive force. Einstein added it to maintain a static universe, though as Chronos points out it wouldn’t have really worked since it would be in an unstable equilibrium.
I don’t know if Einstein actually called it a blunder or not (that qz.com link is interesting), but in any case the CC did not seem to be necessary after Hubble discovered that the universe was expanding. It’s possible that he had a tinge of embarrassment for adding a parameter only to satisfy his own unscientific predisposition that the universe should be static.
But it turns out to be necessary after all, because the universe isn’t simply expanding, but the expansion is accelerating. It’s a very mysterious thing that Einstein couldn’t have predicted, and it’s basically a coincidence that the CC would come in handy in this way. Scientists still have no clue about the origin of dark energy; the best hunch, quantum vacuum energy, gives an answer that’s about a factor of 10[sup]120[/sup] off from the actual CC. Obviously the theories still need work.
Thanks Dr. Strangelove. That clarifies things a lot. As for the issue of whether of not he actually used the words “greatest blunder” for his CC, this article is quite interesting:
Actually, I don’t think including the cosmological constant was a blunder at all, even given the data Einstein had available (though the way he used it was a blunder). It actually follows rather neatly from the math of general relativity, as something like a constant of integration. In my opinion, the intellectually-honest approach would be to say “the theory has this parameter in it, and we don’t know its value, but it might be zero”. Then future observations can attempt to determine whether it is in fact zero.
Can you please clarify the use of the word “constant” in the second paragraph given the way it is used in the first?
I’ve often seen in popular science writing the thread:
a) Einstein came up with CC to keep universe the same size
b) Works for years on the math; gives up; states it was his biggest blunder
c) Whoa! With the discovery of the accelerated expansion of the universe/the placeholder of dark energy he may have been right and there is a cosmological constant after all!
But doesn’t a “constant” imply stasis? So I don’t see how dark energy - which causes accelerated expansion - can being linked to a “cosmological constant”, which would create a static universe.
D18: Einstein’s CC was a constant in the mathematical sense of a fixed value added into a formula. Think like
The “3.2345” is the CC.
The “y” and the rest of the math tells us the stuff you’re talking about. The 3.2345 is just to make the “books balance” with observations.
On present knowledge I think a fair way to summarize Einstein on this is … “It turns out he was right, but for the wrong reason. We’re not quite sure what the right reason is yet, but we think there is one.”
I don’t find the tidbits reported by Mario Livio to be the least bit convincing and certainly not enough to impugn the credibility of George Gamow. Gamow said that Einstein called it his “biggest blunder” in a private conversation. That is completely plausible. The fact that Gamow was a clever and lovable trickster does not make him a liar and, if Einstein said that to his friend, it doesn’t mean he would want to put it in writing and certainly not in a formal publication.
Still, I never knew that the source for the tale was a personal recollection of Gamow’s, so in the future if I mention it, I should append, “according to George Gamow.”
The most famous incident was surely the “Alpher, Bethe, Gamow” paper, as mentioned in the qz article:
Once, for example, Gamow had teamed up with a student of his named Ralph Alpher to write a paper. “He then realized,” Livio told me, “that if he were to add as a co-author another known astrophysicist, whose name was Hans Bethe, then the three names would be Alpher Bethe Gamow, like alpha beta gamma, even though Hans Bethe had nothing to do with that paper.”
Gamow wrote an excellent book about the development of modern physics called “30 Years that Shook Physics.” It is a wonderful book filled with anecdotes about the great physicists of the era. In my recollection, I got the impression that Gamow was the life of the party in those days. I had a professor once who talked with great fondness of his friend “Geo,” who by then had passed away. My favorite book as a junior high school student was Geo’s book “One, Two, Three, Infinity.” I’m not a historian, nor did I ever meet Gamow, but his works were so influential in my life that I’d like to give him the benefit of the doubt.
On the other hand, Ralph Alpher was apparently bitter about the fact that his contributions to the work on nucleosynthesis in the early universe was diluted by Gamow’s prank of adding the great Hans Bethe to the author list.
David, Your welcome. Gamow (pronounced Gamoff) also wrote several books that imagined what would happen in a world in which the speed of light was much smaller or planck’s constant was much larger, the “Mr. Tompkins” series. Those were not as good as the two books mentioned above, in my opinion.
Whatever theory successfully unifies the Gravity with the other, already unified, fundamental forces will be a breakthrough. and likely revolutionary.
Electromagnetism, the Weak Nuclear Force, and the Strong Nuclear Force are all inherently Quantum Mechanical. The theories behind them are very successful in predicting what’s observed in nature to an astounding degree of accuracy.
Einstein’s General Relativity - his theory that includes Gravity - is very successful as well. But it’s incompatible with QM. Many very smart people have been working diligently for decades to try to join gravity with everything else. We humans have not yet succeeded. Whatever theory does unify all the fundamental forces is going to be strange. it will have to include all the wonderful oddities of GR with the deeply beautiful weirdness of QM. the result can’t possibly match human-scale common sense.
I was positive I had posted to this thread. Somehow I managed to put it in a completely different thread. I’ve never done that before. So long, mind, it was nice knowing you.