Einstein's Theories: Fact or Fiction? Research Q&A

[Charles Shahar]

Please let me know if this statement is correct, too vague, or blatantly wrong. I am doing research for an article I am writing, but am not a physicist, nor have I ever taken any physics instruction. If you have suggestions to fix it, please let me know! Thanks!

Einstein thought the initial predictions made by his general theory of relativity about the fate of the universe were wrong, so he introduced a fudge factor that accounted for the expansion of the universe. That fudge factor turned out to be correct, the representation of a yet unseen force (dark energy) that can be observed only indirectly and which is causing the universe to expand ever more rapidly into oblivion.

 

[PeterDonis]

First, welcome to PF!

Second, you do not need to use bold text. That's the Internet equivalent of speaking loudly and is not necessary. I have used magic moderator powers to un-bold your post.

Third, the cosmological constant, which is what you are talking about, is not really a "fudge factor". Einstein did originally write his field equation without the cosmological constant term, and then realized that that equation did not allow for a static solution for the universe as a whole; it said the universe would have to be either expanding or contracting. At that time there was no evidence known that indicated that the universe was expanding or contracting, and most people believed that it was static, i.e., unchanging on large scales over long periods of time.

Einstein realized that if he added the cosmological constant term to his equation, it would allow a static universe; but to call it a "fudge factor" implies that it somehow didn't really belong in the equation, which is not the case; it does belong there, Einstein just didn't realize that when he wrote his original version of the equation. The reasons why it does belong there are rather technical, but they were already suggested by the alternate derivation of Einstein's equation that was done by David Hilbert at the same time Einstein was working on his derivation.

It is correct that the cosmological constant, aka dark energy, is currently known to be small and positive and that this is causing the expansion of the universe to accelerate.

 

[Bandersnatch]

But one should also note that dark energy is not what is causing the expansion as such - as I think the last sentence might suggest. It's only what makes the expansion accelerate.
All the standard models prior to 1990s had the universe expanding without accelerating - in the absence of evidence to think otherwise - which means that the dark energy term was thought to be zero.

 

[Charles Shahar]

Thank you for your response. I am sorry, but I didn't even realize I was bolding anything. I see that may statement contains numerous inaccuracies. I will do further research using your corrections as a springboard! By the way, the cosmological constant appears in Wikipedia as one of the greatest fudge factors in history, so at least in common parlance it is regarded as such. Thank you again for your help.

-Charles

 

[PeterDonis]

the cosmological constant appears in Wikipedia as one of the greatest fudge factors in history

Which is just another illustration of why Wikipedia is not always a reliable source.