Thanks a million Rabbi Kornfeld. Each of your answers is an eye opener. You really have analysed all possibilies.
One question. though, seems you have not addressed: The Guemara asked how did King David knew when was mid-night? Why didn't he know it from the dogs barking at mid-night? And furthermore, according to your answers below, Moshe should have known too when was exactly mid-night that night, by listening simply when the dogs bark to the Mitsrim.
My impression is that you can't set your clock to exactly mid-night from the dog barking, although David did set it from his harp reacting to the mid-night wind. The problem with that conclusion is that the Guemara equates the time of dog barking to the other timing devices to determine the beginning and the end of the night, which both must be exact timing devices since they are needed to determine the beginning and the end of zman krias shema by night. Still puzzled, but hoping to hear your answer. Thank you and Chag Sameach.
Max Munk
Excellent question! I found that the SIFSEI CHACHAMIM on Berachos 3b asks your question, and leaves it unanswered. I didn't see other Acharonim that offered convincing answers either.
I thought at first that the Gemara is offering an answer that works even if the sign of dog-barking is for the end of the Mishmarah and not the beginning. But then I saw that the Vilna Gaon (3a) maintains that even if the other signs are for the end of the Mishmarah, the dog-barking is certainly at midnight.
I just was with my Rebbi, Rav Moshe Shapiro, and I asked him your question. He suggested a simple answer: The dogs do bark exactly at midnight -- but that is not when they begin or end their barking. Since they begin a bit before and end a bit after, David couldn't know the exact moment of midnight through them. The northerly wind, however, is an accurate herald of midnight. It begins exactly at midnight.
Stay in touch, and wishing you a nice Shabbos,
-Mordecai Kornfeld