R' A & C Walters wrote:<br><Royv hold that there is no difference in the oyfek.<br><br>I am not so sure that this is true. There are a number of important acharonim who hold that ofek does count. <br><br>The truth is that it is an absolute peleh to say that ofek doesn't count. The Gemara in shabbos gives a number of astronomical simanim of when tzeis hakochavim is including visible stars, hichsif haleyon v'hichsif hatchton, etc. From these simanim it is patently clear that tzeis hakochavim is based on astronomical reality and therefore I don't see how you can ignore differences in location and times of year when these do change the astronomical reality.
<br><br>The Briskers hold that tzeis is 1/8 of the day after shkia because a person can walk 32 mil in a day and from shkia to tzeis is 4 mil so it is 1/8. This also contradicts reality. In a place like Brisk in the summer the day is about 16 hours long meaning 1/8 of the day is 2 hours. In the winter the day is about 8 hours long meaning 1/8 of the day is only 1 hour. In reality, it does not take twice as long for the sun to set and become dark in the summer then in the winter. How do the Briskers figure out the 1/8 of a day?
<br><br>R' Tam's shita has always really bothered me. The Gra's question of
החוש מכחיש is so powerful and obvious I don't understand how the
Rishonim could have said what they said. Did they never go outside an
hour after sunset and see that it was pitch black and you could see
hundreds of stars? <br><br>