[Avodah] The "New" Egg Finding

[Micha Berger]

I asked the parallel question about R Natan Slifkin's post abut the
kezayis, but now frum media is all abuzz about Prof. Zohar Amar's paper
in JSIJ, bringing yet another proof to what bioligists always said:
today's eggs are bigger than those in use when the unit of measure
was named a kebeitzah.
https://www.jewishpress.com/news/israel/jerusalem/israeli-scientist-reveals-first-temple-period-eggs-differ-little-than-todays-fare-on-the-passover-plates-of-jerusalem-residents/2019/04/14/

Just as our olives are bigger than those of the original kezayis.

First, there is always R Chaim Volozhiner, and (I believe) the Aruch
HaShulchan: a kezayis is measured by the median olive in your time and
place, and a kebeitzah by contemporary eggs. So, the shiurim were never
the huge ones many follow, but do grow as the eggs and olives are bred
to larger sizes.

The Noda biYhudah's problem is the source of most followed rulings. He
saw that the comparing of units of kezayis, kebeitzah and volume measured
in etzbaos don't work. And the NbY's solution was to assume that eggs
had shrunk over time, thus enlarging the kebei'ah.

Scientifically speaking, this assumption was proven wrong. What does
that say about all of our pesaqim that take his position into account?

Briskers would say that only halakhah defines halakhah, and new evidence
shouldn't change the ruling. For example, this is one version of Rav
Chaim Brisker's reason for not donning the Radziner Rebbe's candidate
for tekheiles. A scientific identification of the chilazon doesn't even
qualify as a safeiq. Only mesorah matters in determining halakhah.

But again, what about the rest of us? Should the kezayis and revi'is
similarly shrink in light of the evidence? Can we simply overturn years
of accepted practice, or does acceptance itself mean that we simply have
a different shiur nowadays than Chazal did? Does the fact that part of
the reasoning was proven wrong matter? And if any of these questions
are answered "yes", does it also change lequlah? It's one thing to say
we were wrong to have been lenient all these years, for example, telling
people how much they can eat on Yom Kippur, or eat without making a final
berakhah. But what about stringencies? Did they become binding as Minhag
Yisrael even though they were based on an incorrect historical assumption?

I think this idea that the halakhah must change as we know more about
the facts assumes that halakhah is a fact finding mission. But it isn't,
it's a task of legal interpretation. And so we need to look at how
binding law relates to facts. Making these questions much more subtle
and answers less obvious.

:-)BBii!
-Micha

-- 
Micha Berger                 Man is capable of changing the world for the
http://www.aishdas.org/asp   better if possible, and of changing himself for
Author: Widen Your Tent      the better if necessary.
- https://amzn.to/2JRxnDF          - Victor Frankl, Man's search for Meaning