Shelosha Veshiv'im - mi yodeya?

Question

Who knows seventy-three?

Please cite/link your sources, if possible. At some point in the next few days, I will:

• Upvote all interesting answers.

• Accept the best answer.

• Go on to the next number.

Answer 1

The molad (average synodic lunar period) is expressed by Rabban Gamliel (in Rosh Hashanah 25a) as 29 1/2 days, 2/3 of an hour, and 73 chalakim (1 chelek = 3 1/3 seconds).

Answer 2

73 may have been the Sanhedrin of Shamaya and Avtalyon.

Both were converts to Judaism; there's some discussion whether they were full voting members of the Sanhedrin, or only served in an advisory, non-voting capacity (in which case 71 +2 = 73).

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73 are the volumes of Schottenstein.

(It fits the beat!)

Answer 3

73 is the number of answers to shiv'im mi yodeya!

Answer 4

73 is the regular (alef = 1 ... tav = 400) gematria of "חכמה" (wisdom) and the reverse (in decimal representation) of the ordinal-value (alef = 1 ... tav = 22) gematria of the same word (37).