In fact, the ancient Rabbis dove deep into the very first verses of Genesis to understand their roles.
The Book of Genesis (1:14) tells us, "God said: Let there be lights in the firmament of the heavens to distinguish between the day and the night; let them be for signs, for appointed times, for days, and years.” This verse sparks a fascinating discussion in Bereshit Rabbah, a classical collection of rabbinic interpretations of Genesis.
Rabbi Yoḥanan starts us off by quoting Psalms 104:19, “He made the moon for appointed times.” But then he makes a startling claim: only the sun was actually created to illuminate! So, why the moon? Rabbi Yoḥanan explains that the moon exists for "appointed times," specifically to help us determine the Rosh Chodesh (New Moon) and the years.
Rabbi Shilo of Kefar Tamarta, also speaking in Rabbi Yoḥanan's name, adds another layer. Even though the verse says, "He made the moon for appointed times," the sun still "knows its setting" (Psalms 104:19). What does that mean? Well, we don’t start counting the month based on the moon until after the sun has set. This is a nuanced point about how the Jewish calendar works. Even if the astronomical new moon appears during the day, the calendrical New Moon isn't fixed until the following sunset, marking the start of a new day.
Yusti Ḥavra, quoting Rabbi Berekhya, brings in the Exodus from Egypt to illustrate this point. Remember the verse, "They traveled from Rameses in the first month, on the fifteenth day of the month" (Numbers 33:3)? The Rabbis had a tradition that the astronomical new moon of the Exodus month happened after noon on a Wednesday. The Exodus itself occurred two weeks later, on a Thursday.
The question is, how do we reconcile this with the lunar calendar? If we counted the New Moon from the first visibility of the moon on Thursday night, the Exodus would have happened after only fourteen sunsets, making it seem like it should be the fourteenth of the month, not the fifteenth! The conclusion? We only start counting the moon after the sun sets. This little calendrical puzzle highlights the intricate relationship between lunar cycles and the solar day in Jewish timekeeping.
Rabbi Azarya, in the name of Rabbi Ḥanina, offers a different perspective. He reiterates that only the sun was created to illuminate. So again, why the moon? Rabbi Ḥanina suggests that God foresaw that people would be tempted to worship the sun and moon as gods. By creating both, and essentially "pitting them against each other" in the sky, God diminished the likelihood of either one being elevated to divine status. If there had only been one luminary, the temptation to worship it would have been overwhelming!
But Rabbi Berekhya, citing Rabbi Simon, offers a more harmonious view: both the sun and the moon were created to illuminate. As Genesis 1:15 states, "They shall serve as lights," and Genesis 1:17 adds, "God set them in the firmament of the heavens to illuminate upon the earth."
Finally, the passage circles back to the original verse, explaining what those "signs" and "appointed times" are for: Shabbatot (Sabbaths), the three pilgrimage festivals (Passover, Shavuot, and Sukkot), Rosh Chodesh (New Moons), and the sanctification of years – the process by which the religious court determines when a new year should begin.
So, what do we take away from this ancient discussion? It’s more than just a lesson in astronomy or calendrical calculations. It's a reflection on the delicate balance in the cosmos, the dangers of idolatry, and the profound way that time itself is woven into the fabric of Jewish life. The sun and the moon, seemingly simple celestial bodies, hold within them layers of meaning, reminding us of God's wisdom and the beauty of the natural world. And perhaps, the next time you glance at the night sky, you'll remember this ancient debate and see the sun and the moon in a whole new light.