How to people above the Artic circle measure the start of a "jewish" day?

[kanicbird]

Or below the Antartic? Since they measure the start of the day at sundown?

[elmwood]

From soc.culture.jewish:

Question 7.6:
How do people know when to light candles in the Arctic?

Answer:

The established candle lighting times are based on the more temporate zones. For other zones, the Rabbis came up with a solution: use the established time for lighting candle currently employed in the largest city to your south (or north, if you are in the antartic… or your hometown, if you are in space) where it is possible to set up proper candle lighting charts.

Why is this? The idea of sanctifying Sabbath lights dates back to the Karaite controversy of the Eighth Century CE. In the controversy, a group of schismatics, led by Anan ben David, rejected the efficacy of the Oral Tradition, sticking to a literal interpretation of Torah. For example, when Torah said that one should not kindle fire in one’s habitation on Shabbat, the Karaites disallowed any flame at all, even one kindled beefore the Sabbath. In response, the Rabbanites declared that not only was it permissible to light candles before Sabbath and let them burn, they even instituted rules and regulations – and even a blessing – for their kindling in every Jewish home. And thus was the lighting of Shabbat candles “born”.

So what are we doing when we kindle these lights? We are separating a period of time and consecrating it to spiritual purpose. Thus, while some might focus on the exact time, others focus on the sanctification.

From phy6.org:

[snip]

We asked them, “How do you know when to light Shabbat candles if there is no sunset?”

[snip]

To estimate when the sun would be at its lowest point in Barrow, my husband did some rough calculations based on his reading of Barrow's location on the map, and came up with 2:33 a.m. As it turned out, the two sons had visited Rabbi Mordechai Premock, author of well-known zmanim charts just before embarking on the trip, and after feeding what they had as Barrow's coordinates into his computer, had come up with 2:32 a.m. for that date, July 8, 1994-only a minute off!

Based on that, local midnight (Chatzot Lailah), the time when the sun was at its lowest point in the sky would be 2:32 a.m. Since the sun never set, that moment was also used simultaneously as sunset, time when the stars are out, dawn, and sunrise. Plag Hamincha is the earliest time to bring in Shabbat. Plag Hamincha is 1* variable hours before sunset. Without the sun ever setting, each variable hour was 24 hours divided by 12 equal parts, or 2 hours long, so earliest candle lighting was 2* hours before local midnight, or 12:02 a.m. late Friday night!

Based on that also, latest Shma was 8:32 a.m., and havdallah could not be recited before 2:33 a.m. early Sunday morning! The Adler sons also brought with them something in Hebrew to learn that Shabbat-a commentary which addressed how to determine when Shabbat will occur in a place where the sun does not set! 

[snip]