The last part of Parashat Pinchas provides an overview of the additional sacrifices (korban mussaf) that are offered on Shabbat and on the festivals. The Torah begins with Shabbat, segues to Rosh Chodesh (New Moon) and then makes its way through the entire Jewish Calendar of festivals. The Torah’s wording for Rosh Chodesh is strange [Bemidbar 28:11]: “On the beginning of your months (uv’Roshei Chodsheichem), you shall offer up a burnt offering to G-d…” The Torah uses the possessive “your months” and not simply “months” (uv’Rashei Chodashim). Why does the Torah not use a similar possessive form when describing the Shabbat or the festivals ? For instance, in its discussion of the holiday of Pesach, the Torah says [Bemidbar 28:16] “In the first month, on the fourteenth day of the month, there shall be a Passover sacrifice for G-d”. Why does it not say “a Passover sacrifice for you”?
Rabbi Chaim ben Attar, the “Ohr HaChaim HaKadosh”, suggests that the reason for this has to do with the way in which the new moon is – or was – determined. Until the fourth century, the new moon was determined via witnesses. Two witnesses would see the smallest slice of the lunar crescent and they would travel to High Court in Jerusalem to testify. If their testimony was accepted, the High Court would proclaim a new moon. The Ohr HaChaim HaKadosh suggests that the possessive “your months” is used here because it is the Jewish People who determine when a month begins. The problem with this solution is that the dates of the festivals are derived from the date of Rosh Chodesh. For instance, the Talmud in Tractate Rosh HaShanah [20a] teaches that the date of Rosh Chodesh can be “modified” to prevent Yom Kippur from falling on Friday or Sunday, so as not to cause the undue duress of two consecutive days in which all work is forbidden. The date of Rosh Chodesh can be altered either by disregarding testimony or, believe it or not, by inventing it. The upshot is that just as Rosh Chodesh “belongs” to the Jewish People, so do the rest of the festivals.
A fascinating explanation is found in the commentary of Rabbi Ovadiah Seforno, who lived in Italy during the first half of the sixteenth century. Typically, the commentary of Rabbi Seforno, or simply “the Seforno”, is short and pithy. With this verse, however, the Seforno is more verbose than nearly anywhere else in the Torah: “It was an ancient custom among the Israelites to treat the day of the new moon as a semi-festival… This is why this day has retained a special significance for the Jewish People, i.e. the Torah describes it as ‘the beginning of your months’… The reason for this ancient custom of treating the day of the new moon almost like a festival is that historically, success of the Jewish People in terrestrial matters has always been linked to the lunar cycle. The moon is a phenomenon which has no light of its own, a phenomenon which depends on receiving and reflecting light from an external source… Jewish history reflects the situation of the moon with its periods of ascent and decline month after month. When the moon is not directly exposed to the light of the sun it becomes invisible… The Jewish people do not generate light of their own, do not work at being masters of their own fate, but rely entirely on G-d to guide their fates. They receive this Divinely emanated light when their deeds are pleasing to G-d. Whenever the Jewish people are in a state of sin, their sins act as a barrier between them and their G-d so that they are deprived of their source of light. Whenever the Jewish people’s fortunes are at low ebb this represents a desecration of G-d’s name…”.
According to the Seforno, the reason that the Torah uses the possessive “Your Rosh Chodesh” is because Rosh Chodesh – the new moon – had always held symbolic meaning for the Jewish People, even before they were commanded by the Torah to observe it. According to this symbolism, G-d is the sun, the Jewish People are the moon, and our sins are the earth, blocking the sun’s light from reaching the moon.
While the Seforno’s explanation does address our question concerning the possessive “your new moons” and while from a symbolic perspective it is admittedly quite beautiful, from an astronomic perspective it, well, strays from pure scientific fact. The phases of the moon result from its revolution around the earth at a rate of about once every twenty-nine and a half days. The instantaneous phase is determined by the amount of solar light reflecting off the moon as seen by an observer on earth. When the earth is situated between the moon and the sun, sunlight reflects off the moon and the observer on earth sees a full moon. The reason the earth does not cast a shadow on the moon is because the plane of the moon’s rotation around the earth and the plane of the earth’s rotation around the earth are not coplanar. They are off by about 5.1 degrees. Conversely, when the moon is situated between the earth and the sun, sunlight reflects off the opposite (far) side of the moon, where it cannot be seen by a terrestrial observer, who sees no moon at all, or, better yet, he sees the Dark Side of the Moon.
Here is where the Seforno’s explanation clashes with astronomy: On the Rosh Chodesh, the moon (the metaphor for the Jewish People) receives maximal solar light because the earth (the metaphor for our sins) is not located between the sun (the metaphor for G-d) and the moon. The problem is that this instance of maximal exposure to solar light cannot be seen by an observer on earth. To the observer on earth, the new moon is dark. On the other hand, during a full moon, the earth (our sins) is located directly between the sun (G-d) and the moon (the Jewish People). But because of the offset between the orbit of the moon around the earth and the earth around the sun, the moon appears fully illuminated. Why, according to the Seforno, do we celebrate the new moon, a moon that appears “deprived of its source of light”? Isn’t this symbolic for a “desecration of G-d’s name”? Shouldn’t we be celebrating the full moon, an object that lights up the night sky? The metaphor seems backwards.
I was discussing my problem with a friend who happens to have a firm background in astronomy and he told me something that blew me away. The next time you look at the new moon, take a closer look. Sometimes, you can glimpse a pale glow on the unlit part of the crescent moon. The glow is strong enough so that features on the moon – craters and the like – can be discerned. Where does this light come from? It cannot come from the diffusion of the sunlight that forms the crescent because the moon has no atmosphere with which to diffuse the light. Rather, the moon is being lit by sunlight that is being reflected off of the earth. The astronomical term for this phenomenon is “earthshine”. Since the light that generates earthshine is reflected twice, once off the earth’s surface and then off the moon’s surface, this light is much dimmer than the lit portion of the moon. Earthshine gives new meaning to the explanation of the Seforno: On Rosh Chodesh, the earth (our actions) reflects the light of the sun (G-d) and illuminates the moon (Jewish People). On Rosh Chodesh, we celebrate not the direct light that we cannot see but the indirect light that we can see – the light that we create. Our actions do not have to form a barrier between ourselves and G-d. They can serve as a source of light. Each month we are reminded that we are inherently good, that we can shine, if not with our own light then by reflecting the light of the Divine. And that is reason for celebration.
There is no dark side of the moon, really. Matter of fact, it’s all dark…
Ari Sacher, Moreshet, 5779
Please daven for a Refu’a Shelema for Yechiel ben Shprintza.
 The astute reader will recall that the possessive “Roshei Chodsheichem” is used in one other place in the Torah, in its discussion of the silver trumpets that Moses was commanded to fashion [Bemidbar 11:11]: “On the days of your rejoicing, on your festivals and on your new-moon celebrations, you shall blow on the trumpets…” However, in this particular verse, the Torah also uses the possessive festivals (mo’adeichem) and so Rosh Chodesh does not stand out.
 Hillel II replaced the determination of the new moon via witnesses with the perpetual Jewish Calendar still in use today. The Moslems, who also use the lunar calendar, still use witnesses.
 This prevents lunar and solar eclipses from occurring on a monthly basis.
 Some have proposed that the fact that certain festivals – Pesach and Sukkot – fall on the fifteenth of the month suggest that they are in some way celebrating the full moon. See, for instance, https://www.chabad.org/multimedia/video_cdo/aid/3406278/jewish/The-Secret-of-the-15th-of-Av.htm