The Mishna (Berakhot 4:1) brings the opinion of R' Yehuda to the effect that the latest time for shacharit is the fourth hour of the day. In explaining R' Yehuda's opinion, Kehati elaborates upon the nature of halakhic hours (being equal divisions of the day-time, rather than fixed units of time) and brings an example that commences as follows:

למשל אם נקח יום מימי תמוז הארוכים, וכגון שעלה בו השחר ב-2 לפי שעוננו וזמן צאת הכוכבים היה ב-8, דהיינו שארכו של יום זה 18 שעות, נמצאת השעה הזמנית של אותו יום שעה ומחצה לפי שעוננו

My paraphrastic translation:

By way of an example, if we were to take a day from the month of Tammuz (in which the days are longer), in which the sun comes up at 2:00 by our watches and the stars come out at 8:00pm, then the length of such a day would be 18 hours and an halakhic hour would be found to be 1.5 hours in length (by our reckoning).

I have no problem with the calculation. What I do have a problem with is the assertion that the sun ever, anywhere, comes up at 2:00 in the morning. In fact, having spent no small amount of time at myzmanim.com, I cannot even find a habitable corner of the globe on which the sun ever comes up much earlier than 4:00am.

Is the halakhic definition of dawn such that it could ever be two hours (or more) before the first rays of sunshine?

  • Check Fairbanks, Alaska. Sunrise at 2:57 on June 21 – Double AA May 11 '14 at 4:42
  • @DoubleAA, sounds like an answer (especially if you find a city where usnrise is 2, not 2:57. Try Barrow, perhaps). Why not post it as such? – msh210 May 11 '14 at 5:46
  • @msh210 It doesn't sound like an answer to me – Double AA May 11 '14 at 5:48
  • @DoubleAA the question is wondering (implicitly) whether K'hasi can only be understood by existence of a long twilight; the fact you cite says otherwise. – msh210 May 11 '14 at 5:50

Firstly, Alot Hashachar is either 72 minutes (Rambam) or 90 minutes (other Rishonim) before sunrise, according to the times on my Lu'ach.

Considering that sunrise can be as early as 4:30 in Isreal (Winter time) that would put Alot at 3:00. I find it hard to believe that Alot is never as early as 2:00 - since some Northern countries don't even have a night during some of the summer months.

Using Kaluach, I see that during July the Halachic hour is 1:25 hours long and Alot is at 1:11

Secondly, Kehati is explaining the concept using an example that's easy to understand - he's not saying that such a place exists (though I'm sure it does).

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