Rabbinic Responses to the Transit of Venus

Originally posted on Rationalist Judaism, June 1, 2012.

It’s hard not to have noticed that a remarkable celestial event will occur this Tuesday.  The blogs have been discussing it, and new books have been published to commemorate the event. The event if the transit of Venus, and if the weather cooperates and the clouds stay away, you will be able to witness an event that will not occur again for another one hundred and five years. You’ll need the right equipment too, but that need not cost more than a few dollars.[1] With it, you will be able to see the planet Venus pass in front of the sun. Seen as a small black dot, it will make its way across the face of the sun over a period of several hours. The exact length of time depends on where you are located; in New York City the transit of Venus will be visible at 6.04pm, while in Jerusalem it can be seen at 7.37am.[2]

The transit of Venus was of huge scientific importance in the nineteenth century, because by observing it from various locations and using some clever trigonometry, it allowed astronomers estimate the distance from the Earth to the sun more accurately than had ever been done before.[3]  Knowing this distance would allow the distance of other planets from the Earth to be calculated, which would then give the answer to one of the most important unanswered astronomical questions of the time: Just how big is the solar system?

The transit of Venus occurs twice in eight years, followed by a gap of 105.5 or 121.5 years[4].  The first time it could be viewed was in 1639, but that transit was witnessed by only two observers. By the time of the paired transits of 1761 and 1769, scientific instruments were accurate enough to provide the data needed for the all-important calculations. So in 1760 and again in 1768 the major European nations including Britain, France, Spain and Russia, sent teams across the globe to measure the transit times of Venus.  Perhaps the most famous expedition was that led by Captain James Cook, who sailed from London to Tahiti and made a series of accurate measurements that allowed the all-important calculations to be made.

Much less well known are the Jewish responses to all this. Although Jews had been taking a keen interest in astronomy since Talmudic times, the Copernican revolution had challenged the notions of the centrality and immobility of the Earth.   However the arguments for the truth of heliocentric system of Copernicus were still largely theoretical (and would remain so until the discovery of stellar parallax in 1836 and the demonstration of Foucault’s pendulum in 1853).  The transit of Venus offered some indirect support for the Copernican model, in that it would allow an accurate measurement of the size of the solar system.


The first Hebrew book to discuss the transit of Venus was Sefer Haberit, The Book of the Covenant,first published in 1797 in Brno. The author was Pinhas Hurwitz, a self-educated Jew from Vilna.  Sefer Haberit was divided in two parts; the first, consisting of some two hundred and fifty pages is a scientific encyclopedia, addressing what Hurwitz called human wisdom (hokhmat adam) and focuses on the material world. The second part, shorter than the first at only one hundred and thirty pages, is an analysis of divine wisdom (hokhmat elohim), and focuses on spiritual matters.[5] Sefer Haberit was an encyclopedia, and contained information on astronomy, geography, physics, and embryology. It described all manner of scientific discoveries, from the barometer to the lightening rod, and gave its readers up to date information on the recent discovery of the planet Uranus, and the (not so recent) discovery of America. Sefer Haberit was also incredibly popular; it has been reprinted some thirty times, was translated into Yiddish and Ladino, and remains available today.

In a section on solar and lunar eclipses, Hurwitz recalled the transit of Venus in 1769. He described how Cook’s expedition had almost been in vain when some of their scientific instruments were stolen the night before the transit, and how, thanks to the team’s valiant efforts, the stolen instruments were returned.  Here is the original text:

This was a fairly accurate recounting of the facts, although in actuality the theft occurred a month before the transit.  (Despite guards that were placed to patrol the camp, a local had managed to slip in and steal a vital piece of equipment.) What is of interest here is that Hurwitz did not inform his readers of the real reason that the transit was to be observed.  There is no mention of the way in which the transit of Venus could be used to determine the size of the solar system or the distance from the sun to the Earth, which were of course the real reasons for all the time and effort being spent in observing it.  Why did Hurwitz leave all this out, and suggest instead that the reason for sending Captain Cook all the way from London to Tahiti was to see if the predictions for the time of the transit were accurate?

The answer lies in the fact that Hurwitz was somewhat conflicted about his belief in the model suggested by Copernicus in which the Earth and all the planets revolve around a stationary sun.  In some places in Sefer Haberit he was supportive of the Copernican model. For example, he noted that Copernicus provided

proofs and supports for his position [that] are clearly written in his book. He was remarkably successful in this matter, for today virtually all of the wise men of the world agree that this opinion is in fact correct. His model is used to understand all matters of astronomy, the phases of the moon and the movement of the stars. Any calculation involving their appearance can be understood far more clearly and simply than if we accept the earlier model…[6]

Despite this approval, Hurwitz ultimately sided with the Tychonic model in which all the planets except the Earth revolve around the sun, while the sun orbits a stationary Earth, dragging the planets along with it.  He did this for a number of scientific and theological reasons, including a belief that the Earth was the crowning glory of creation. “All of the planets were only created for the sake of this Earth, and everything was created for the sake of mankind on the Earth…even if the purpose of these other heavenly creations is not always clear to us.”[7] Since the Earth was the reason for creation, it was only fitting that it lay at the center of the universe.  Although he ultimately rejected the Copernican model, Hurwitz wrote that that a Jew may believe in it without fear of heresy:

any person of Jewish faith who strongly believes in this [heliocentric] theory should not be considered to be weak in his belief in the written Torah or the Oral Law, and certainly such a person should never be branded or suspected of  heresy.  Indeed he could be considered a zadik among Israel, so long as his other beliefs and practices follow both the written Torah and the Oral Law, and he fears God.[8]

However, Hurwitz felt that because there were a number of biblical verses that described the Earth as being stationary, that must in fact be the way it was in reality. One of the experimental supports that Hurwitz gave was the evidence from a stone dropped from the top of a tower. If the Earth was in motion the stone should, it was argued, fall some distance west of the tower, since during the time the stone was in free-fall, the Earth was moving from west to east. Hurwitz claimed that when a stone is dropped from a tall mast on a moving ship, it fell a small distance from the base of the mast. The fact that this did not occur on land was conclusive evidence that the Earth was in fact stationary.[9]

Hurwitz described the goal of Cook’s expedition to Tahiti as testing the predictions of the timing of the transit, when in fact its mission was far more important than that. But since Hurwitz ultimately rejected the Copernican model he likely chose not to discuss the real reason for Cook’s expedition, namely to provide data that would allow the size of the Copernican solar system to be calculated.  Instead, Hurwitz described the mission as one to verify the times of the predicted transit, as a sort of test of the ability of astronomers to predict these kinds of events.  Although he did not reveal the real goals of the expedition, he noted that is was a great success, and that transit of Venus occurred precisely the times predicted, or as he put it “כתבו אשר מכל דבר נפל לא.”


In 1835 a young Jew from eastern Poland called Hayyim Slonimski published a book called Kokhava Deshavit, (The Comet), to coincide with the return of Halley’s comet. Slonimski was a remarkable figure in the history of Jewish science. He was traditionally educated in yeshiva, yet earned recognition from the Russian government and a prize from the Imperial Academy of Sciences in St Petersburg for his work developing a calculating machine. Slonimski founded the famous Hebrew language weeklyHazefirah (Dawn), which focused on scientific and political issues, and he wrote several books on astronomy and mathematics.  Unlike Hurwtiz, Slonimski fully embraced the Copernican model, and had no problem with the biblical verses that suggested the Earth did not move. They were not to be interpreted literally, and scientific facts could never be in conflict with the truths of the Torah, “for both are true and given by the true God.”

Specifically, if we believe that the Earth has a daily revolution around its axis, and a yearly revolution around the sun, this does not contradict our Torah or our faith, Heaven forbid. For in his Torah God only revealed that which ensures eternal spiritual perfection, things that are far from the normal understanding of a person. But God did not reveal the secret detailed workings of creation. Instead he left this goal for the mind.[10]

It is no wonder then that Slonimski described the real importance of the transit of Venus for his readers, for it was not a threat to his pro-scientific worldview. Here is the original text:

Notice here how Slonimski had no hesitation in telling his readers the reason why the transit was so important: “if [Venus] happens to pass in front of the sun and we can see it, that would be the time for astronomers to measure the angle it subtends in front of the sun (solar parallax),[11] which is a fundamental and valuable [measure] for astronomy, as those who know these things understand. This is the reason that astronomers went to such lengths at that time to measure the moment of its [Venus’]  conjunctions at various locations  across the Earth. In 1769, when astronomers calculated that the transit would occur, they all prepared for this time in order to provide the most precise measurements…”


The last rabbinic text we will review was called Nivreshet Lenez Hahamah (The Chandelier of the Sunrise), published in Jerusalem in 1898.  Its author was Hiyyah David Spitzer, and he rejected Copernicus and his model, believing instead that the entire universe revolved around the Earth, because “everything, including the Sun, was created for the Earth and for Israel who dwell on it and keep the Torah.” Spitzer’s main interest was in determining the precise times of sunrise and sunset in halakhah, and he spent hours carefully measuring these times in and around Jerusalem.   His book was a summary of his findings, but included a criticism of Joseph Ginzburg’s Ittim Lebinah (Times for Wisdom) that had been published in Warsaw in 1886. Ginsberg had defended the heliocentric model and had included a folded pull out chart of the solar system.  Spitzer was outraged at Ginsberg’s suggestion that the new astronomy was acceptable to Jews.  “I saw things written in [Ittim Lebinah] that bring a person to heresy,” he wrote, and he was particularly incensed to see the colored illustration at the end of the book. “Woe to those eyes that must witness a universe turned upside down.”[12]

Spitzer did not directly address the transit, but rather the rejected all the calculations about the size of the solar system and the distance to the nearest stars, that had been calculated using the observations of the transit of Venus, as well as estimates of the speed of light that had been made in the nineteenth century.  He did so on both scientific and religious grounds. For example, if as astronomers claimed, some stars were 24,000 light years away from Earth, their light could not have reached the Earth that had only exited for some 6,000 years.  In addition, what purpose would there have been in creating such remote stars, whose light served no purpose for those on Earth?[13] Finally, since the speed of light is not mentioned in the Talmud, the notion that light has a finite speed cannot be correct. Here is the original text.[14] .

 Even when judged by the scientific standards of his own time, Spitzer's work was astonishingly naive. using a thought experiment he proved to his satisfaction that starlight actually needed only a second to reach the Earth [15]. Furthermore, Spitzer asked how astronomers could possibly have performed the work necessary to claim that some starts were 3,000 light years from Earth.  Here is his rather sarcastic objection, aimed at Copernicus himself [16].  

Spitzer claimed that anyone could perform a simple experiment that would refute the notion that light took a finite time to travel vast distances.   If, during the day, the door to a house was suddenly closed, it should still be possible to see an image of the sun for some time since the light would take time to travel from the site of the now closed door across the room and into the eye of the observer. Similarly,

if we open a closed door or window…we should not be able to see sunlight for some time, and we should be forced to sit in darkness as if the doors had not been opened. What can be said of this idiocy and stupidity, at which any person would laugh?  Rather, as soon as a person opens his eyes he stops seeing nothing and when he opens his eyes at night he immediately sees all the stars, both those nearby that need sixteen years for their light to travel, and those far away whose light takes one hundred and twenty years to reach us.[17]

The motivation for Spitzer’s attack on science was his belief that the scientists themselves had but one goal in mind – to destroy the fundamentals of Jewish belief: “Their entire aim is to deny God’s Torah, to destroy religion, to confuse those who would disagree with them and to embarrass and belittle the sages of Israel.”[18] Here is the original:

These three rabbinic authors had three quite different ways of approaching both the history of the transit of Venus and the science that was deduced from it.  Hurwitz was certainly inquisitive about all things scientific, but did not reveal the real goals of the expeditions to observe the transit, because they would raise further questions about the model of the solar system in which he believed-   a model in which the Earth was the unmoving center.  Slonimski informed his readers of the real goals of the observations and had no issues – religious or scientific – with accepting a universe in which the Earth was not the center.  But for Spitzer, the enterprise of astronomy was a vast conspiracy to undermine Torah values.  He therefore stretched to reject any science that the transit of Venus bequeathed to future generations.

We’ve come a long way as a people since the transits of 1765 and 1882.  The next time this celestial event occurs will be in December 2117.  What the Jewish people will look like then is hard to guess, it seems likely that we will continue to argue over the religious meaning of natural events for many generations to come.


[1] For details see http://www.exploratorium.edu/eclipse/how.html#PIN2.

[2] Precise times of the transit and its visibility can be found at http://eclipse.gsfc.nasa.gov/OH/tran/TOV2012-Tab03.pdf and http://eclipse.gsfc.nasa.gov/OH/tran/TOV2012-Tab04.pdf.  See alsohttp://transitofvenus.nl/wp/where-when/local-transit-times/.

[3] For a good discussion which requires only a minimal understanding of the mathematics see Mark Anderson, The Day the World Discovered the Sun.  De Capo Press 2012; 231-240.

[4] Rarely, there is no second transit eight years after the first. The next this occurs will be in 3089.

[5] As somewhat of a disappointment for those for whom Hurwitz exemplified the rationalist movement, Hurwitz revealed that he had written his book to explain a sixteenth century kabbalistic work of Hayyim Vital entitled Sha’arei Kedushah  (The Gates of Holiness).

[6] Sefer Haberit Part one #9:8 (1990 ed. 149-150).

[7] Sefer Haberit Part one #3:3 (1990 ed. 50).

[8] Sefer Haberit Part one #9:8 (1990 ed. 52).

[9] There are other reasons that Hurwitz gave for rejecting the Copernican model. These are fully discussed in my forthcoming book.

[10] Slonimski, Kokhava Deshavit , fourth un-numbered page of the author’s introduction.

[11] Slonimski here is absolutely correct. Solar parallax is an angular measurement that is one-half of the angular size of the Earth as seen from the sun. The reason the measurement is so important is that the distance to the sun is the radius of the Earth divided by the solar parallax.

[12] Hayah David Spitzer, Nivreshet Lenez Hahamah (Jerusalem: Blumenthal, 1898). 30b-31a.

[13] Spitzer, Nivreshet Lenez Hahamah 33b-34a.

[14] Ibid. 35a.

[15] Ibid. 34b.

[16] Ibid.

[17] Ibid.

[18] Ibid.