Halley's comet

Horayot 10a ~ Halley's Comet, or Rabbi Yehoshua's Comet?

הוריות י,א

כי הא דר' גמליאל ורבי יהושע הוו אזלי בספינתא בהדי דר' גמליאל הוה פיתא בהדי רבי יהושע הוה פיתא וסולתא שלים פיתיה דר' גמליאל סמך אסולתיה דרבי יהושע אמר ליה מי הוה ידעת דהוה לן עכובא כולי האי דאיתית סולתא אמר ליה כוכב אחד לשבעים שנה עולה ומתעה את (הספינות) [הספנים] ואמרתי שמא יעלה ויתעה אותנו]

Rabban Gamliel and Rabbi Yehoshua were traveling together on a ship. Rabban Gamliel had sufficient bread for the journey, while Rabbi Yehoshua had bread and also some flour. [The journey lasted longer than expected, and] when Rabban Gamliel’s bread was finished he relied on Rabbi Yehoshua’s flour for nourishment. Rabban Gamliel said to Rabbi Yehoshua: How did you know from the outset that we would have such a substantial delay that you would need more flour? Rabbi Yehoshua said to Rabban Gamliel: There is one star that rises once in seventy years and misleads sailors at sea, causing their journeys to be extended. And I said: Perhaps that star will rise during our journey and mislead us.

Rabbi Yehoshua knew that a comet would likely be visible during his sea voyage, and that its light would confuse the sailors who navigated by the stars.  That comet returned about once every 70 years.  Does that remind you of anything?

Halley's Comet

Halley's comet last made an appearance in 1986. I remember looking up at the night sky with my father, and being thoroughly disappointed. Alas, the comet and the earth were on opposite sides of the sun, which made the quality of the appearance "the worst in two thousand years." 

Comet over 5th ave and Broadway.jpg

Other visits from Halley's comet were far more spectacular. In 1066 the comet was so bright that it was threaded onto the the 230 foot-long Bayeux Tapestry recording the Norman conquest of England. In 1531 it was seen for three weeks, and was visible even when the moon was full. And in 1910 the comet shone so brightly that it made its way onto postcards commemorating the spectacle.

The orbit of Halley's Comet. From  here .

The orbit of Halley's Comet. From here.

Renaming the comet for Rabbi Yehoshua

There are several claims for the oldest written description of Halley's Comet. The Chinese described its appearance as early as 240 BCE, and the Babylonians noted its appearance in 164 BCE on a on a cuneiform tablet now in the British Museum in London. The current record is a Greek sighting of the comet from 467BCE.  In contrast there is apparently no dispute about the earliest description of the length of the comet's orbit.  That accolade has been awarded to Edmund Halley who, using data from comet sightings in 1531, 1607 and 1682 suggested that the eponymous comet had a periodicity of about 76 years. But today's page of Talmud is clear: a comet with an orbit of about 70 years was identified by Rabbi Yehoshua. We know that "Halley's" Comet appeared in 66CE, when both Rabbi Yehoshua and Rabban Gamliel (II) were young men, and it must be to this comet that Rabbi Yehoshua referred.  Therefore it is Rabbi Yehoshua who should be honored with first describing the periodicity of the comet, and not Halley.  This is both self-evident and beyond question. It is also another of several examples which we have mentioned elsewhere in which scientific principles or facts were not properly attributed to the talmudic rabbis who first identified them. And so Talmudology is delighted to rename the comet Yehoshua's Comet.

Here's another fun fact about Rabbi Yehoshua's Comet of 66CE. It was described by the Jewish historian Josephus, who wrote that "a star resembling a sword stood over the city; a comet persisted for a long time." Josephus also recorded that the comet was seen during Pesach in 66CE. He wrote that it was taken as a good omen by those who started the Jewish rebellion against the Romans which lasted until the destruction of the Temple in 70CE.  And who was it who led another rebellion some sixty years later? Why, it was Bar Kochvah - the Son of the Star.

1835 - The First Hebrew Book about Halley's Comet

Hayyim Zelig Slonimski aged seventy-five. From   The Jewish Encyclopedia   ,  New York, Funk and Wagnalls, 1912.

Hayyim Zelig Slonimski aged seventy-five. From The Jewish Encyclopedia, New York, Funk and Wagnalls, 1912.

To coincide with the appearance of Halley's Comet in 1835, a Hebrew book called Kokhava Deshavit (The Comet) was published in Vilna. It described where and when the comet would be visible with precise coordinates for the inhabitants of Bialystok, as well as an explanation of the nature of comets and their orbits. The author was the remarkable Hayyim Zelig Slonimski, (1810-1904), the founding editor of Hazefirah (The Dawn), a weekly Hebrew-language newspaper first published in Warsaw in 1862. He also wrote Mosdei Hokhmah (The Foundation of Wisdom), a work on algebra, and struck up a friendship with the famed German naturalist and explorer Alexander von Humboldt (1769–1859). Not content with all this, Slonimski invented a method to send two telegraphs simultaneously over one wire (which was a very big deal at the time,) and developed a calculating machine that he later presented to the Imperial Academy of Sciences in St. Petersburg. It was so successful that in 1845 the Russian minister of education made Slonimski an honorary citizen, a remarkable honor given the general oppression faced by the Jews at the time.

Orbit of Halley’s Comet from  Kokhava Deshavit,  Vilna, 1835. Note that the outermost planet is Uranus. The second edition of the book (1857) described the discovery of Neptune in 1846. From the  Talmudology Library .

Orbit of Halley’s Comet from Kokhava Deshavit, Vilna, 1835. Note that the outermost planet is Uranus. The second edition of the book (1857) described the discovery of Neptune in 1846. From the Talmudology Library.

In Kokhava Deshavit Slonimski  explained Kepler's three laws of planetary motion, outlined Newton’s law of universal gravitation, and described the discovery of stellar aberration by the British astronomer James Bradley, which was an early, indirect proof of the validity of the heliocentric model of the solar system. After a description of each of the planets, Slonimski returned to the nature of comets in general and Halley’s Comet in particular. He described some of the astronomers whose findings helped explain what comets were, and ended with a depiction of the expected path of the comet.

In 1909 Mark Twain famously wrote that

I came in with Halley's Comet in 1835. It is coming again next year [1910], and I expect to go out with it. It will be the greatest disappointment of my life if I don't go out with Halley's Comet. The Almighty has said, no doubt: "Now here are these two unaccountable freaks; they came in together, they must go out together."

And he was right. He died on April 21, 1910, one day after the comet's closest approach to Earth. Twain thought the story of Halley's Comet was personal.  But Hayyim Slonimski knew that the story of the comet was national. He hoped that its reappearance would be celebrated by his descendants who had returned to their Jewish homeland. He ended his book describing how the comet would pass by the Earth, then circle behind the Sun, and then reappear sometime in March 1836. After that,

...it will continue along its path gradually becoming dimmer to the inhabitants of the Earth as it follows its orbit, until it will reappear [in 1910]. May it be then as a sign and wonder for our children after us in the Holy Land. Amen.

And so it was.


[For more about Hayyim Zelig Slonimski and his life as orthodox Jewish scientist, Talmudology is glad to offer this excerpt, taken from here.]

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