Tuesday, April 2, 2024

Eclipses in הלכה and מחשבה

In light of (no pun intended) the upcoming solar eclipse here in the USA, I thought I'd post a piece I wrote about eclipses a couple of years ago.

B’nei Yisrael are traditionally symbolized by the moon. The generations from Avraham are likened to the cycle of the moon. David and Shelomoh were the 14th and 15th generations from Avraham Avinu. It was during their reign that B’nei Yisrael was at its pinnacle. They conquered their enemies, stretched out their borders and built the beis hamikdash. This is just like the moon which is biggest on days 14 and 15. After Shelomoh, national stability began to deteriorate and B’nei Yisrael lost their splendour, just as the moon wanes after the 15th day.

There are many insights to be taken from this symbolism. The gemara (Rosh HaShanah 25a) quotes the pasuk (Tehillim 104:19) “shemesh yada mevo’o,” the sun knows its path. The gemara comments that the sun knows its path but the moon does not. The relative path of the sun as it changes from season to season is quite predictable and easy to figure out. The path of the moon, however, is erratic in nature and seems not to follow a specific pattern. We may understand this as analogous to the way in which the world is run. The nations of the world, traditionally symbolized by the sun, are governed, to a certain degree, by the laws of nature. There is a less focused Divine Providence that guides their everyday events. This is akin to the predictable path of the sun. One need not delve too deeply to realize that B’nei Yisrael are governed in quite a different manner. The great miracles that adorn our history, as well as the day-to-day twists and turns that befall our nation to this day are clear indications that there is nothing haphazard about the course of events that befall us. There are no patterns or laws of nature to rely on, just as the moon follows a seemingly unpredictable path.

The gemara (Sukkah 29a) tells us that when there is an eclipse of the sun, it is a bad sign for the gentiles. When there is an eclipse of the moon, it is a bad omen for B’nei Yisrael because we follow the lunar calendar and they follow the solar calendar. There is an intriguing insight that lies beneath the surface here as well. An eclipse of the moon happens when the moon moves into a position behind the earth such that the light of the sun cannot reach it. One might say that it is “the moon’s fault” that it was eclipsed. This is the way we must view calamities that befall us. We must search within for the causes and realize that it is our own deeds and actions that have brought them about.

An eclipse of the sun happens when the moon moves in front of the earth in such a way that it blocks the sun’s light from reaching certain spots on the earth. Here, too, we see that it is path of the moon that has caused the eclipse. The sun and earth are insignificant players in a solar eclipse. The lesson learned from this gemara is that everything that happens in this world is, in some way, connected to B’nei Yisrael. Despite our relatively insignificant size, like that of the moon to the sun, the world was created for us and continues to be governed according to our actions. This is not something to take advantage of but rather, a great responsibility that we must bear on our shoulders at all times.


Every month, on the Shabbos before Rosh Chodesh, as part of "Birkas HaChodesh," the time of the molad is announced. This time refers to the birth of the new moon on which Rosh Chodesh is based. Astronomically, this is when the moon passes between the earth and the sun, thereby completing its monthly cycle. Although the time of the molad no longer determines the exact day of Rosh Chodesh since our calendars are set, we use this figure to determine when we may recite kiddush levanah. Based on the gemara (Sanhedrin 41b), we may only recite kiddush levanah when the moon is new, that is, when it is waxing. Knowing the midpoint between the two molados allows us to determine this exact time (Rema OC 426:3). Also, we do not begin to say kiddush levanah until three whole days after the molad, when the moon is big enough to see.

The period of time from molad to molad (synodic period) that we use for these calculations is 29 days, 12 hours, 44 minutes and 3 and a third seconds. However, this is not an exact, constant figure. Rather, it is the average length of a synodic period as indicated by Rambam (Hilchos Kiddush HaChodesh 6:3). The time we use for the molad may differ from the time of the actual molad, lunar conjunction, by a couple of hours one way or the other. In general, we don't really know when it does differ and we just rely on the average synodic period for all halachic calculations. However, nature can sometimes tell us that our calculations are off - with an eclipse.

An eclipse of the moon happens when the moon is in a position behind the earth such that the sun's rays cannot reach it. Clearly, this can only happen at the exact middle of the month, lunar opposition, when the moon is exactly behind the earth with respect to the sun. An eclipse of the sun is when the moon moves directly in front of the sun, obstructing the view of the sun from earth. This will only happen at the exact beginning of the month when the moon is exactly between the earth and the sun, i.e. the molad.

The issue of eclipses is discussed in Beis Yosef and Darchei Moshe OC 426. The consensus there is that if an eclipse of the moon is witnessed, then kiddush levanah may no longer be recited, even if this is before the prescribed time for sof zeman kiddush levanah, the halfway point between molados. [9/26/2015: This halachah was especially significant in this area of the world this month. The official time for sof zeman kiddush levanah was 12:47 am EDT on Thursday night (Friday morning, officially). However, there was a much anticipated full lunar eclipse that night. According to NASA, the time of mid-eclipse, essentially the official middle of the month was 11:40 pm EDT. Therefore, kiddush levanah should have been recited before that time, despite whatever is written in the calendars.]

A solar eclipse, however, is not as simple. Beis Yosef writes that a solar eclipse may not be used to determine the proper time after which one may not say kiddush levanah. However, there does not seem to be any discussion about beginning to say kiddush levanah. If the time of the molad were preceded by a solar eclipse, as the molad of Teves 5761 was by eight hours, would that allow us to recite kiddush levanah earlier? Conversely, if the molad were to precede the eclipse, would that move back the time at which we may recite kiddush levanah? For our upcoming solar eclipse, the peak time is actually around a full half day before the recorded time of the molad.

Perhaps, the reasoning behind Beis Yosef's ruling with regard to sof zeman kiddush levanah would not apply to techilas zeman kiddush levanah. When a lunar eclipse indicates that we may no longer recite kiddush levanah it is because we may not rely on an average when there is a clear indication that the average is incorrect. When it is an average against a clear natural indication, we dispense with the average. However, the calculation for sof zeman kiddush levanah is achieved by adding half of the average synodic period to the previous molad. To allow a solar eclipse to determine sof zeman would be to combine the clear evidence with an average. We must rely on one or the other but we may not combine the two.

To allow the solar eclipse to determine when we may begin to recite kiddush levanah is relying only on the clear evidence of the eclipse and not on any other averages. Therefore, it would seem that we may adjust the time based on a solar eclipse. Furthermore, the apparent source for the custom to wait three days is Talmidei Rabbeinu Yonah (End of Berachos 4.) But the specific wording used is that one should recite kiddush levanah when people derive benefit from the moon's light - after two or three days. In fact, Yad Ramah on Sanhedrin writes that it may be recited after one day. Therefore, to be lenient in this regard when there is sufficient astronomical evidence on our side does not seem so farfetched.

It should be noted that Darchei Moshe adds his own rationale - that a lunar eclipse is more widely viewed whereas a solar eclipse is only visible in a very limited area of the world. With that explanation, we wouldn't use the solar eclipse in any way to modify our average figures.