3387 —זמן בין השמשות ותפקיד ראיית הכוכבים

B"H, 5th of Nissan, 5715.

Brooklyn.

Haraha"g vavac"h iy"a nu"n etc. Chaim Menachem Shlomo

Shalom u'Vrachah!

In response to your letter from the 28th of Adar ... regarding your comment on the tzt"z responsa Yoreh Deah siman 214, where it rules in a case of doubt whether birth occurred before or after sunset, that since no stars were visible in the sky at the time of birth, it is still considered day. You question this—since according to Rabbeinu HaZaken in his Siddur, bein hashmashot begins when the entire sun sets and after three-quarters of a mil it is night, so according to this view, star visibility makes no difference.

But regardless of how we interpret the baraita about "one star—day, two—bein hashmashot..."—whether it applies only to Rabbi Yosi or also to Rabbi Yehuda (and this has already been discussed at length in several books; this is not the place for it)—if no stars are visible in the sky—not even one, not even among the large ones—it is still considered day (and sunset has not yet occurred). Therefore, the poskim leave this matter undefined as brought in the above responsa, and this is unrelated to the dispute between Rabbi Yehuda and Rabbi Yosi. Because by not seeing any stars at all, one can determine whether sunset has occurred or not (such as when a mountain or cloud blocks the western horizon).

With blessing,
M. Schneersohn

Summary

The Rebbe explains that if no stars are visible—even large ones—it remains day regardless of differing opinions about bein hashmashot. The absence of visible stars serves as a practical indicator for determining whether sunset has truly occurred.