Solar Eclipse

QUESTION: The molad (“birth” - new cycle of the moon) for the month of Nissan was announced as being on Monday at 10:57 PM. Today, Monday, April 8th there will be a solar eclipse in NY at 2:20 PM. A solar eclipse is when the moon passes between the Sun and the Earth and begins a new cycle around the Earth. Shouldn’t the time we announced for the molad be the same as the time of the solar eclipse?

ANSWER: The molad is announced based on the time in Jerusalem when the moon begins its new cycle. Since Jerusalem is 7 time zones away, when we announce that the molad will take place at 10:57 PM, this is similar to saying it will take place in New York at 3:57 PM. Furthermore, the molad is announced in accordance with “Jerusalem solar time.” Ordinarily, when we refer to 12:00, we are referring to the time on the clock or, in other words, civil time. In contrast, according to solar time, noon is not 12:00 on the clock but the time when the sun reaches its highest position in the sky. This is called high noon (or Chatzos in halachic terms). There can be a significant disparity between the civil noon and solar noon. Today, chatzos in Jerusalem is at 12:41 PM, not at 12:00, a difference of 41 minutes. (The difference between what we announce and the actual molad is about 2 hours and 18 minutes!)

The reason for the discrepancy with the eclipse is because the molad is not announced based on the astronomical position of the moon but rather based on an average cycle. The exact length of a rotation of the moon around the Earth varies from month to month because the Earth travels in an elliptical orbit around the sun and not in a circle. The average length of the cycle is 29 days, 12 hours, and 793 chalakim (approximately 44 minutes, as a chelek is 3 1/3 seconds.) The announcement of the molad is based on this average lunar cycle. In other words, to compute the molad, we take the last molad and add to it 29 days, 12 hours, and 793 chalakim even though we know that this is not exact. That is why in a month such as this, there can be a significant difference.

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The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.