The Torah ordained that the calendar date changes (for halachic purposes) at the onset of night. This important precept affects a broad range of mitzvos and also determines that the time of the arrival (and departure) of Shabbos and Yom Tov is at night. It is therefore essential to ascertain when ‘night’ halachically occurs. …In the context of astronomy, the phenomenon of nightfall is a process that occurs gradually, by degrees. One can observe how this takes place every day, from the beginning of dusk until when the rays of the sun disappear completely from the sky. This period of time, when day evolves into night, is colloquially referred to as twilight. The Talmud uses the term ‘bein hashmashos’ (lit. “between suns”) to describe the twilight period. Because bein hashmashos possesses some of the characteristics of both day and night, it is classified as a period of halachic uncertainty. The halachic demarcation of “absolute night” occurs sometime during this period of time, although the precise moment cannot be pinpointed.
[Ed’s 2-cents: This is not an accident, and no matter how smart we are or how scientifically or technologically-advanced we become, we will never be able to identify the exact point of ‘absolute night’. Rather, Hashem – through the halacha - ordained that every night will commence with a period of uncertain day/night (bein hashmashos) and then transition into absolute night. When does this bein hashmashos begin? When does absolute night begin? Those questions require complex discussion, and they are not the subject of our siman. Rather, our siman is here to teach that, although by and large, we must begin to observe all of the Shabbos prohibitions at the onset of bein hashmashos – certainly no later than sunset (Heb. ‘sh’kiyas hachama’ or just ‘shkiya’), and even earlier if Shabbos was accepted before shkiya – nevertheless, a few exceptions and leniencies apply during bein hashmashos up until the time that absolute night is determined to have set in, as follows:]
As a general rule, (even) the Rabbinic restrictions are forbidden during this time (i.e. bein hashmashos, and certainly the Torah restrictions.) However, under certain conditions, some Rabbinic restrictions are waived during this “grey area“ of time…
a) ‘Amira l’akum’ (lit. ‘instructing a non-Jew’). During the first 40-minutes (Ed. This time frame was given for New York. I suspect that in Atlants it is a bit shorter.) of the bein hashmashos period, one may instruct a non-Jew to perform melacha on behalf of a Jew if there is a compelling need, including:
- Shabbos or Yom Tov needs – e.g. lighting candles, warming Shabbos food, switching lights on or off, adjusting central heating or A/C, etc. - Mitzvah needs – e.g. lights, heating and air in a shul or beis midrash to enable people to daven or learn. - Significant financial loss – e.g. turning off a car that was still running, hiding valuables, locking a car or place of business, and even certain emotional needs, such as the lighting a yahrzeit candle, even though this is only a custom.
b) ‘Hatmana’ (i.e. insulating a pot of food with material) and ‘Eruv Chatzeiros’ (incorporating the residents of a courtyard to allow carrying therein). These two particular Rabbinic decrees were theoretically permitted during bein hashmashos. However, these examples are usually impractical, because in most situations, Shabbos was already accepted by most of the population in the city or community. At that point, Shabbos takes effect arbitrarily for everyone in the city. Even these Rabbinic restriction are forbidden after this time. Only if one happens to be in a secluded area away from any community, may he do Hatmana or set up an Eruv Chatzeiros until 40 minutes past shkiya. (Note: This is in contrast with Amira l’Akum that is permitted bein hashmashos – Ed. even though Shabbos was accepted – because the action is not directly that of the Jew himself.)