Second, according to Eybeschutz, sunspots "have no known cause, and have no fixed period to their appearance". We can't fault Eybeschutz for his first claim, but - even by the science of his day - his second was not correct. In fact both Scheiner and Galileo knew - and wrote - that sunspots were permanent (at least for a while) and moved slowly across the face of the sun.
Sidebar: Eybeschutz, Sunspots and Copernicus
It's interesting to note that Galileo got very excited about the discovery that the spots moved across the face of the sun. This suggested (though it did not prove) that the sun itself was spinning. Galileo had also discovered that Jupiter was orbited by moons. Both of these discoveries now added further support to the Copernican model in which the Earth was spinning on its own axis, and was not the center of all the movement of objects in the sky. But Eybeschutz did not believe Copernicus was correct: "Copernicus and his supporters have made fools of themselves when they declare that the Earth orbits [the Sun]. They have left us with a lie, and the truth will bear itself witness that the Earth stands still for ever." Eybeschutz wanted to have sunspots explain away a talmudic mystery, but he dismissed the evidence that they provided in other matters - namely, that the earth moves.
Was the Plague of Darkness a Solar Eclipse?
Since we are only a couple of weeks before פסח, we will end with another look at an old theory, in which the Plague of Darkness was caused not by a miracle, but rather by a (conveniently timed) solar eclipse. In 1916 Eduard Mahler (d. 1945) suggested this explanation in his Handbuch der Jüdischen Chronologie, (Vienna 1887). According to Mahler, there was a solar eclipse visible in Egypt on Thursday March 13, 1335 BC. Since this was the only such eclipse, it would date the Exodus as occurring on March 27th, 1335 BC.
However, there's an obvious problem: the Torah describes the darkness lasting for three days. But a solar eclipse is over in a matter of minutes. Mahler has in interesting answer: instead of reading the verses (in Exod. 10) like this:
(22) there was a thick darkness in all the land of Egypt for three days. (23) They did not see each other, or get up from their places for three days.
read them like this:
(22) there was a thick darkness in all the land of Egypt. (23) For three days they did not see each other, or get up from their places for three days.
The eclipse lasted only a few minutes, but its effect on the Egyptians lasted three days. And what about the Jews in Goshen -why was there no Plague of Darkness there? Because they lived outside of the totality - the area in which the complete eclipse occurred - and would not have noted any significant darkening. Now there are some problems with this theory - like the fact that according to NASA, the solar eclipse to which Mahler referred seems to have been only a partial eclipse throughout Egypt. Still, it makes for a good discussion. Try that at your Seder Table.