From: Eugene Salamin <gene_salamin@yahoo.com> To: math-fun <math-fun@mailman.xmission.com> Subject: [math-fun] Does entropy increase because the universe is expanding? Will someone who holds an affirmative view on this question answer the following.

A chemist constructs two vessels separated by a closed stopcock.? One vessel is filled with gas, the other is evacuated.? The stopcock is opened.? In our expanding universe, the gas expands into the empty vessel until the pressures are equalized.? Entropy has increased.? What would be observed in a contracting universe?

? --? Gene

--quite. It used to be believed maybe 20 years ago the universe (quite possibly) was expanding but would eventually turn round and we'd get a "big crunch." Presently, though, with the supernova redshift evidence, it is believed that the expansion will accelerate due to EInstein cosmical constant and continue forever. Anyhow, in the turnaround/crunch universe, we'd all be observationally aware the turnaround had happened, same way we now are aware of the expansion... and the stars would keep getting older as usual, dropped balls would lose energy each bounce as usual, and the gas would keep expanding into vacuum when stopcock opened, and life would go on normally for billions of years, etc etc. Eventually, human life would become impossible as the crunch neared, and still later all life presumably would get killed, both due to high temperatures. It is difficult for me to comprehend the idiocy of anybody who asserts the contrary, they presumably have no understanding of the basics of statistical physics... if I could understand what they had in mind I could perhaps construct a genuine argument against them rather than merely branding them idiots. It's kind of like arguing against a flat-earther. In the case of H.Brady wondering about what the universe is "expanding into" etc, well, you have to learn general relativity, then you know. If you don't then it'll just sound like voodoo. I personally taught myself GR initially from Pauli's book, which is available in English from Dover, and I recommend it highly for beginners. But learning GR may be tough for somebody without the right background. Personally I feel I've learned GR pretty well, thank you, but for QFT (quantum field theory) I feel a lot less happy about my depth of understanding. And when it comes to string theory, AdS-CFT correspondence, and all that recent jive, my understanding is not much further along than "is great and strange voodoo, kemo sabe" and I fear I'll never surmount that.