Who knows sixty-six?
Please cite/link your sources, if possible. At some point in the next few days, I will:
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Accept the best answer.
Go on to the next number.
66 are the degrees of longitude from the "western edge of civilization" to Jerusalem. (In the Rambam's times only the Eastern Hemisphere was known to be inhabited, so they spoke only of 180° of longitude, centered on a line corresponding to about modern 59° east of Greenwich. Jerusalem is 24° west of that line.)
(Commentaries to Rambam, Hil. Kiddush Hachodesh 11:17)
66 C.E. was the beginning of the Jewish revolt against the romans, which ultimately led to the destruction of the Temple: First Jewish–Roman War (Wikipedia).
(Well, at least according to a historical account. We know that the Temple was destroyed because of sinas hinam, but the Romans acted out the decree, and used the revolt as justification.)