[Avodah] Davening direction

[Micha Berger]

On Mon, Oct 31, 2022 at 05:24:38PM -0400, Zev Sero via Avodah wrote:
> Which achronim denied something that the entire world has agreed on since
> Chazal's day?  The Bavli Amora'im seem to have not yet heard of this "modern
> discovery", but in EY they had.   Certainly the Rishonim all knew.

The notion that lakes are heated at night because the sun was under
them implies a sun that goes under a flat earth. If the sun were in
orbit around a spherical earth, the sun would be further from pools of
water on this side of the planet than during the day -- the same height
of the orbit PLUS the diameter of the planet.

So, R Yehudah's "proof" that the Greeks were right that the sun goes
under earth because mist (which he took to be steam) rises from lakes in
the morning implies that even after meeting the Athenians, Rebbe still
thought the earth was flat.

I don't know indication that Chazal definitely kept up with the science
on this one. I think it is implied by how much their positions track
the most accepted theory of their mileau in general, but I can't really
prove that there is a maamar chazal about the world being round.

According to a tradition recorded by the Shitah Mequbetzes, Rabbeinu Tam
says that R Yehudah's "venir'in divreihem midevareinu" means that that
Athenian astronomy only looks more right than ours, but isn't actually
true. And numerous acharonim held like this. So there was a stream of
acharonim who trusted the gemara over their contemporaries' scientific
theories.

(Not counting the Rama. He believed the sun went around the earth only
because Tycho Brahe was the leading voice in astronomy in Warsaw in his
day. They even had acquiantances in common. So, it is unsurprising that
he embraced the Tychonic model (the sun, moon and stars go aroudn the
earth, but the planets go around the sun) rather than the Copernican
one.)

A bit more history of science... The Greeks were better theoreticians,
but the Babylonians had better star charts. In fact, their theory about
the sun stopping and reversing course at the end of the day (and the
beginning) was because of an observation that the Greeks had missed.

The closer the sun is to the horizon, the more its light is refracted.
(The effect that makes a spoon sticking out of a cup of water look
broken.) To the extent that we actually see the sun when it is already
somewhat below the horizon, but the light it bent so it looks like it
is still at it. The sun looks like it slowed down. In fact, you may
have noticed that the sun near sunset (or sunrise) looks like an oval;
the light from the side of the sun nearer the horizon is more refracted
than the light from the top.

The Babylonians didn't have a theory about light refraction. They just saw
the sun slow down, change shape, and vanish. It really would look like it
was changing directions, from traveling across the sky to moving the width
of the raqia. Their astronomy is a very logical error. One the Greeks
only avoided by not paying sufficient attention to what sunset looks like.

And that explains why the amoraim of Bavel were sticking with the science
as taught in the Sassanid Empire, while the amoraim of EY were using
the science as taught by the Greeks to the Romans. As I said earlier, the
general trend is that maamarei chazal are consistent with the accepted
theory in the speaker's surroundings.

Tir'u baTov!
-Micha

-- 
Micha Berger                 If a person does not recognize one's own worth,
http://www.aishdas.org/asp   how can he appreciate the worth of another?
Author: Widen Your Tent                - Rabbi Yaakov Yosef of Polnoye,
- https://amzn.to/2JRxnDF                author of Toldos Yaakov Yosef