In my high school German class, someone use the term "die Hengst", which elicited peals of laughter from the teacher. Trying to catch her breath and seeing the blank stares on our faces, she tried to explain, "Hengst is a male horse
and die is
feminine! ..." Ok, I never did get it, but I did have moment like that this morning. I mentioned to a good friend of mine -- a kohein with very solid yichus -- that I didn't read news papers and therefore could not comment. He replied, "No problem, I'll be your weekday goy to relate current events." It was at least as funny to us as "die Hengst" was to that high school teacher.
Part of the discussion touched on how big a k'zayis is. We have all suffered through both stuffing our mouths with more matzah than you can shake a stick at and then feeling doubly miserable realizing that we have (yet again) possibly failed to fulfill the mitzvah d'oraisa of achalis matzah. ("Possibly" is not much comfort when it comes to d'oraiso's, actually.) Why do we do that? Because, as we all know, our eggs are half the size the were in the good ole days back in Bavel, but a k'zayis is still half the volume of an egg. Actually, there is a lot that goes into this conclusion; enough so that they Mishna Brura calls this an extreme chumra (but one that impinges on a d'oraisa, so what can he do).
So... how, in fact, do we know that our eggs have shrunk? The Biur Halacha (271, dh shel r'vi'is) explains that Tz'lach (whom the Biur Halacha calls a genius) made a very careful experiment in which he measured the volume of an egg by using the fact that the shiur of flour from one needs to take chala is 43 eggs worth. He then measured that shiur using two different methods. First, according to the calculation given by the Rambam in chapter 6 of Bikurim regarding the size of a mikveh. Secondly, the Tz'lach used the method of the Tur OC 656 of measuring the volume of water displaced by 43 eggs. (Apparently, Archimedes both learned from the sages and did not feel compelled to reveal his sources.) The measurement with eggs was half the size of the measurement of flour, so the Tz'lach concluded that our eggs are half the size of Chazal's.
The Biur Halachah goes on to say that while the demonstration of the Tz'lach is compelling, there are other factors that play an important role. For example, Chazal also tell us that an average size person ought to be able to fit more than the volume of three eggs in his mouth at one time. Maybe cool hand Luke would be ok with that, but most of us would find that a daunting task, to say the least. The Biur Halacha thus concludes (in suppport of his p'sak in the Mishna Brura) that one should try as much as possible to be machmir like the Tz'lach (especially when it comes to d'oraisos), but also meikel when there are other factors.
This, by the way, is a beautiful and accurate application of the scientific method. Whereas modern "science" has quite an agenda. (After all, why is evolution in biology? Did you learn about Kantor Sets and the Axiom of Choice in your algebra class?!?) Modern "Science" is hell bent (literally) on proving there is no absolute source of morality to permit folks to do whatever they please. Our sages, on the other hand, take the evidence they are given and work with it. When they find an area where they are unable to penetrate into the subtleties required to gain a full understanding, they admit that and move on. We go with chumros (even extreme chumros) where we can, and we work with our deficiencies.
Only One is perfect. Only a mench can accept that.