Reply To: Chidushim on Daf Yomi Shabbos 30

שבת לד,ב

We will discuss Ben Hashamoshos. There are three views in the duration of a מיל mil 2000 amos, a techum shabbos. It is measured by the time a middle stature individual walks it. In SA O’CH 261,1 the RMA says a mil is 1/3 of an hour minus a 1/30 of an hour which 20 – 2 = 18 min and the Mechaber in SA O’CH 459,2 says that a mil is a quarter hour and 1/20 of an hour that is 15 min plus 3 min = 18 min. In YD 69,6 says around 1/3 of an hour being 20 min. The GRA there hold that a 4 mil is 1 1/2 hr. or 90 min making a mil 22 1/2 min. The Rambam holds that a mil is 24 min. Ben Hashmoshas is 3/4 of a mil 3/4 (18) = 3 (4 1/2) = 13 1/2 min. according to the SA. There is a an argument when Ben Hashmoshas starts. The Yereim (Rav Eliezer Mimetz) holds that is by the shkiah, so ben hashmoshas would be 13 1/2 min before shkiah. The Geoinim hold that Tzetz Hakochovim (middle size stars determine night) so ben hashmoshas 13 1/2 min starts after shkiah until Tzetz Hakochovim. The Rabbenu Taam in Tosfas says that there are two shkias. One when the sun starts to set and the other coincides when the middle stars appear with night when the sun completely disappears. The four mil, 4(18) = 72 min starts from the first shkia and ends at the second shkiah.
According to the Behag, the women accept shabbos when they light candles and the ashkenazim who make a brocho on shabbos after lighting, place there hands on there eyes in order not to enjoy the light until after the brocho. The men accept shabbos through their davening.
There is a safek how to pasken, many are stringent before shabbos and after shabbos. Before shabbos we accept the Yereim with a mil of 24 min lighting 18 min before shkiah. After shabbos we follow the Rabbenu Taam using 18 min as a mil, so work is done 72 min after shkiah or 90 min from lighting candles which is easy to remember. Others hold like the Geonim. The Chabad Baal Hatanyeh paskens in his SA Harav like the Rabbenu Taam but changes his view like the Geonim in his siddur which was written later.