Bilaam’s Star Prophecy

In Parashat Balak, among the prophecies of Bilaam, we find this astronomically themed verse:

אֶרְאֶנּוּ וְלֹא עַתָּה אֲשׁוּרֶנּוּ וְלֹא קָרוֹב דָּרַךְ כּוֹכָב מִיַּעֲקֹב וְקָם שֵׁבֶט מִיִּשְׂרָאֵל וּמָחַץ פַּאֲתֵי מוֹאָב וְקַרְקַר כָּל בְּנֵי שֵׁת

I see it, but not now; I behold it, but not near. A star shall come forth from Jacob, and a scepter will arise from Israel that will crush the corners of Moab and uproot all the sons of Seth. (Numbers 24:17)

In this prophecy for the far future, the “star” from Jacob, is generally assumed to be a great Jewish ruler – depending on your choice of commentator, usually either King David or the Messiah. Rashi, the great medieval scholar, comments:

דרך כוכב: כתרגומו, לשון דרך קשתו (איכה ב ד), שהכוכב עובר כחץ, ובלע”ז דישטנ”ט (מזנק) כלומר יקום מזל

A star has gone forth: As the Targum [Onkelos] renders, an expression similar to “He has bent his bow” (Lam. 2:4), for a star shoots out like an arrow; in old French, destent; as if to say, his star [or good fortune] shall rise.

Rashi’s explanation sounds like a description of not just any star, but a “shooting star” – i.e. a meteor – or perhaps a comet! (Perhaps more on that idea another time…) Rashi continues to comment on the Moab part of the verse that this verse refers to King David (based on 2 Samuel, 8:2.) According to his interpretation, the subsequent verses prophecy about the future Messiah.

However, Ralbag, a.k.a. Gersonides, great medieval astronomer and rabbi, says thus:

darach kochav - ralbag

A star has gone forth: This is a hint to the King Messiah, whose actions will be revealed and seen at the ends of the earth. This is why he is likened to a star that is revealed and seen by all – to show also his loftiness and majesty. Also, since as a star’s influence will be felt in many actions in the world without actually reaching those feeling its influence, so the Messiah’s influence will be felt in many actions without actually meeting those feeling his influence. As it says (Isaiah 11:4) “and he shall smite the earth with the rod of his mouth and with the breath of his lips he shall put the wicked to death.” This is why is says “shall go forth” – his deeds will spread out to the ends of the earth.

Ralbag is, at least in part, focusing on the radiation – i.e. the light – of a star by which it is seen and its influence felt very far away from its source. (OK, that might be my slightly modern slant on his explanation…)

Note that this explanation seems to perhaps be based on (or alluding to) Devarim Rabbah 1,20:

?אמרו ישראל לפני הקב”ה: רבש”ע! עד מתי משועבדים אנו בידו

אמר להם: עד שיבא אותו היום שכתוב בו (במדבר כד): דרך כוכב מיעקב וקם שבט מישראל. כשיצא כוכב מיעקב וישרף קשו של עשו

מנין? שנאמר (עובדיה א): והיה בית יעקב אש ובית יוסף להבה וגו

Israel said before the Holy One Blessed Be He: Master of the Universe! Until when will we be subjugated in his hand? He said to them: Until the day comes that is written of it “A star has gone forth from Jacob and a sceptre will arise from Israel.” When a star comes forth from Jacob and burns the straw of Esau. From whence? As it says “And the House of Jacob shall be a fire and the House of Joseph a flame, etc.” (Obadiah 1)

With some modern knowledge of astronomy, we can understand other possible meaning included in this verse, similarly focused on the light from stars, based on understanding how the Sun and other stars shine.

Stars, including the Sun, produce their energy by nuclear fusion (see this earlier post), deep in the core of the star, the only part where the temperature (roughly, 15 million degrees) and pressure is high enough to enable nuclear fusion to occur. The energy travels outwards to the surface where it “shines freely” through space. The radiation zone and convection zones through which the energy travels to the surface are defined by which process is the dominant mode of the energy being transported: radiation (i.e. photons/light propagating) or convection (i.e. mixing of fluids, like in a boiling pot.)

Cutaway diagram of the Sun showing the core, radiation and convection zones.
Cutaway diagram of the Sun showing the core, radiation and convection zones. (from Pearson, Cosmic Perspective)

However, when photons (light) are produced by fusion, it is of such high energy that the light is gamma rays, not visible light. Despite their high energy, those photons take a very long route out of the star, over the course of which they are transformed into many less energetic photons of (partially) visible light.

As they travel through the radiation zone immediately surrounding the core, they “bounce” around between electrons (primarily) a LOT! The typical distance they travel between bounces is considerably smaller than a millimeter! Each time they “bounce” their direction of travel will change, and thus the path that they travel is a very convoluted “random walk.” In a random walk, the total distance traveled is related to the average length of each step (known as the mean free path, i.e. the average distance the photon will travel before colliding with another particle) by the square root of the number of bounces: distance = √N  x M.F.P.

Diagram of a random walk of a photon from the center to edge of radiation zone (not to scale!) (From Pearson, Cosmic Perspective)
Diagram of a random walk of a photon from the center to edge of radiation zone (not to scale!) (From Pearson, Cosmic Perspective)

The distance to travel out of the Sun’s (or other similar sized stars’) radiative zone is a few hundred thousand kilometers (the Sun is HUGE!), and thus the time required is on the order of 100,000 years! (Some astronomical models calculate it even higher – like a million years! Which, even if not necessarily correct for our own Sun, surely is the case for some much larger stars.)

So the light we are seeing today from the Sun and other stars was actually the result of fusion processes that took place 100,000 or more years ago! It just took the light that long to escape and shine freely through space. (Once it does, it becomes much faster to travel through space; sunlight reaches the Earth from the surface of the Sun in only about 8-9 minutes!)

This provides interesting lessons by analogy to think about with respect to Bilaam’s prophecy regarding the Messiah. Just like the light from a star is actually generated long before it becomes “visible”, so too the shining forth of the (spiritual) light of the Messianic era was “generated,” in some way, in generations past. Perhaps, even in the time of Jacob the Patriarch, when the conflict alluded to in the following verse in this prophecy began:

וְהָיָה אֱדוֹם יְרֵשָׁה וְהָיָה יְרֵשָׁה שֵׂעִיר אֹיְבָיו וְיִשְׂרָאֵל עֹשֶׂה חָיִל

Edom shall be possessed, and Seir shall become the possession of his enemies, and Israel shall triumph.

Another idea: Throughout the long (sometimes seemingly random…?) walk of Jewish history all along the way since then, every time there seems to be a “step backwards” it is part of an overall travel in the upwards direction; the “negative” steps will be overtaken by the positive ones, and they will eventually add up to go the distance.

Or to think of it another way, the light of the future days is already here, just temporarily hidden, slowly making its random walk to be revealed. It could begin to shine freely any day now… as it says  היום אם בקולו תשמעו – today, if you hearken to My voice.” (Psalms 95:7; cf. b. Sanhedrin 98a and y. Taanit 3b, 1:1)


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