# Talk:Observable universe

## Need a physics expert to verify the article.

Mandruss  22:51, 13 October 2017 (UTC)

Article Observable universe features a claim: "higher estimates implying that the universe is at least 101010122 times larger than the observable universe". I have checked the given reference but a referred scientic paper talks about megaparsecs as units (one megaparsec is around 3 and ¼ million light years) in its annotation rather than times thr observable universe. Also, it's not exactly clear if the paper's author meant about parsecs of length (of radii or diameter) or cubic parsecs of volume but it didn't seem to be a comparison to observable universe's magnitude (a ball of ~45.7 billion light years in diameter, ~399.8 trillion cubic light years in volume). Can someone recheck the original PDF and say if it's a mistake.Fixmaster (talk) 22:25, 13 October 2017 (UTC)

I don't think we need a physics expert for this, per se. I'm not sure what PDF is being referred to, but when you're talking about 101010122, you really almost don't care about the units. If the units are off by a factor of, say, a googol, you won't be able to see the difference in the 122:
101010122·(1 googol) =
101010122·(10100) =
10(1010122+100)

I could carry this calculation out further, but hopefully you already see the point — 100 is completely negligible next to 1010122. By the time you propagate it up to the 122, you'll have to go out a huge number of digits to see the difference. --Trovatore (talk) 05:28, 14 October 2017 (UTC)

## Mistake in critical density

In the article I came upon this sentence:

"Critical density is the energy density where the expansion of the Universe is poised between continued expansion and collapse." This however is false - it is only correct for a universe without dark energy. Because of dark energy for example a universe with density higher than the critical can expand forever. So I recommend this line be removed. — Preceding unsigned comment added by 77.70.29.135 (talk) 20:54, 10 November 2017 (UTC)

Content in Wikipedia is based on reliable sources. If you have a source to drive this change please cite it. Thanks. Jytdog (talk) 16:36, 11 November 2017 (UTC)
The objection is correct, I'll fix the problem. Banedon (talk) 00:16, 13 November 2017 (UTC)