More about צאת הכוכבים
The Daf Yomi shiur that I go to is given by a big Talmid Chacham who is UO (he has been learning in Kollel for 12+ years). It was interesting to see how he dealt with R' Tam being against reality. Basically he threw up his hands and said the simplest answer is to say נשתנה הטבע. To me this is difficult to accept, there is absolutely zero evidence for that (certainly not since R' Tam's time which is less then 1000 years ago). I would rather say that R' Tam made a mistake in science. The fact is that one of the main acharonim who discusses this topic, the Minchas Cohen, made a clear error in science. He writes that even thought where he lived in Europe reality contradicts R' Tam, but it must be that in Israel R' Tam corresponds to reality. Of course, in fact, twilight is shorter in Israel then Europe and therefore contradicts R' Tam even more. In other words, the Minchas Cohen made a mistake in science. R' Tam lived in France and very possibly made the same error.
What amazes me more is that in America so many people are machmir for 72 minutes. Besides what I pointed out in my previous post (that 72 minutes is probably not shitas R' Tam), R' Tam's shita is against reality, it is pitch black out well before 72 minutes. I understand that this is the shita of many Rishonim and the Shulchan Aruch, but it is not a halacha l'moshe m'sinai, the Gemara gives astronomical signs which we are 100% certain come well before 72 minutes.
Am I being arrogant or anti-Torah in thinking that R' Tam made a mistake? It isn't just me, that Gra made the same point (that R' Tam contradicts reality). I can't help it, I have been brought up to think logically and shitas R' Tam just makes no sense.