Flying Over The Dateline

[dirah]

1. This is amazing.
2. MyZmanim calculated that with a departure time of 11-1110am Japan time, tzeis would come at 3:46pm Japan time, which is 2:46am EDT.
Based on the flightaware coordinates for that time, you'd be at 56.0653   -178.7757.

Seems like that generates a true Tzeis, right?
https://www.chabad.org/calendar/zmanim_cdo/additional/true/bdef/0/before/18/coords/56.0653%2C-178.7757/locationtype/3/n/SomethingFishy2/save/1/tdate/5-26-2022/tzname/America*Anchorage/jewish/Halachic-Times.htm

3. How relevant is Tzeis here? In other words, if this route flew polar (which it can't now) and there was no tzeis, would that be a sfek sfeika to not count an extra day of sefira as you cross the dateline?

Here are civil twilight times (6-degree Tzeis) for those coordinates:
https://aa.usno.navy.mil/calculated/rstt/year?ID=AA&year=2022&task=2&lat=56.0653&lon=-178.7757&label=&tz=4&tz_sign=-1&submit=Get+Data
You can see the 6-degree Tzeis for that place and date is 5:16 or 5:18 EDT (UTC-4).

At 2:46 EDT the sun would not have even set:
https://aa.usno.navy.mil/calculated/rstt/year?ID=AA&year=2022&task=0&lat=56.0653&lon=-178.7757&label=&tz=4&tz_sign=-1&submit=Get+Data

MyZmanim uses 8.5 degrees for default Tzeis, which would have been even later.

I punched in a bunch of more coordinates and checked times, and it does increasingly look that the period of dark on this flight coincided with being in Polar region where there was just sunset, but no Tzeis. [As per above link about Polar Zmanim, it could still be that there was a Halachic night, depending on Shittah.]

I am assuming the discrepancy with MyZmanim tables is that it uses average of last five flight paths, and in this case it probably ended up assuming a more southerly path. Using Zmanim charts to predict Zmanim works pretty well for most flights, but up far north its like trying to gaze into a crystal ball. Minor flight variations make major changes.

Here is an older article about polar flights at length: https://goo.gl/v5mf4d (see page 28 specifically about flight paths).
Needs updating and some corrections, hopefully it will happen one day iyh.

[Dan]

Here are civil twilight times (6-degree Tzeis) for those coordinates:
https://aa.usno.navy.mil/calculated/rstt/year?ID=AA&year=2022&task=2&lat=56.0653&lon=-178.7757&label=&tz=4&tz_sign=-1&submit=Get+Data
You can see the 6-degree Tzeis for that place and date is 5:16 or 5:18 EDT (UTC-4).

At 2:46 EDT the sun would not have even set:
https://aa.usno.navy.mil/calculated/rstt/year?ID=AA&year=2022&task=0&lat=56.0653&lon=-178.7757&label=&tz=4&tz_sign=-1&submit=Get+Data

MyZmanim uses 8.5 degrees for default Tzeis, which would have been even later.

I punched in a bunch of more coordinates and checked times, and it does increasingly look that the period of dark on this flight coincided with being in Polar region where there was just sunset, but no Tzeis. [As per above link about Polar Zmanim, it could still be that there was a Halachic night, depending on Shittah.]

I am assuming the discrepancy with MyZmanim tables is that it uses average of last five flight paths, and in this case it probably ended up assuming a more southerly path. Using Zmanim charts to predict Zmanim works pretty well for most flights, but up far north its like trying to gaze into a crystal ball. Minor flight variations make major changes.

Here is an older article about polar flights at length: https://goo.gl/v5mf4d (see page 28 specifically about flight paths).
Needs updating and some corrections, hopefully it will happen one day iyh.

So, how does the potential lack of tzeis affect tefilos and sefira as you cross the dateline?
Or how would taking a polar route from HND-JFK without sunset affect sefira as you cross the dateline?

[gozalim]

1. Regarding places with questionable dates /times there is a difference between staying there (מקום יישוב) vs passing through. Note that the first אג"ק to discuss this (תש" ט) makes this distinction between the boat and arrival in Australia...
2. Sefira is supposed to be counted after tzeis. No bracha is made in those other locations.
3. AFAIK satmar follows some of the later shitos for tzeis (for sure RT not AR/GRA)

[dirah]

1. Regarding places with questionable dates /times there is a difference between staying there (מקום יישוב) vs passing through. Note that the first אג"ק to discuss this (תש" ט) makes this distinction between the boat and arrival in Australia...
2. Sefira is supposed to be counted after tzeis. No bracha is made in those other locations.
3. AFAIK satmar follows some of the later shitos for tzeis (for sure RT not AR/GRA)

1. That letter is something else entirely. The question there was not whether it is day or night, but which day of the week (Shabbos). Day of week is not an empirical fact, i.e. there is nothing in nature or astronomy to say its Monday or Tuesday, (i.e. days are just clones). Rather, days of the week are a human convention, i.e. people decide what day is Sunday, Monday … Shabbos, (hence places where people changed day of the week, with a recent example here,) and why a Dateline became necessary, and lehavdil, for Jews, all of that is with the Koach of Torah. It is about this that the Rebbe says (as expanded more in various Sichos, and LA’s Rosh writes about it at length in Migdal Ohr) that there is a connection between Shabbos and the way it was first established (perhaps even unwittingly) by the first Yidden who lived there, and hence the dilemma for one who is in a place without a community, or passing very briefly through a place with a community.
However, day / night is an empirical matter and has nothing to do with human convention. Therefore, whether there is a community and how long you stayed is irrelevant. This is true even in the Polar according to the Shittos that day / night is determined by the position of the sun (which is certainly the Rebbe’s position), day / night remains an empirical matter, and not subject to human convention. Thus, the above letter is not relevant here at all.

2. Incorrect. Sefirah is counted at לילה. In “normal” locations, Tzeis is לילה. In unusual locations, it may be something else… in fact your next point demonstrates this… did the Jews of far Northern Europe who followed RT not count Sefirah?

3. Correct, but I believe they do this as 72 minutes and not 16.1 degrees.

[AsherO]

1. That letter is something else entirely. The question there was not whether it is day or night, but which day of the week (Shabbos). Day of week is not an empirical fact, i.e. there is nothing in nature or astronomy to say its Monday or Tuesday, (i.e. days are just clones). Rather, days of the week are a human convention, i.e. people decide what day is Sunday, Monday … Shabbos, (hence places where people changed day of the week, with a recent example here,) and why a Dateline became necessary, and lehavdil, for Jews, all of that is with the Koach of Torah. It is about this that the Rebbe says (as expanded more in various Sichos, and LA’s Rosh writes about it at length in Migdal Ohr) that there is a connection between Shabbos and the way it was first established (even unwittingly) by the first Yidden who lived there, and hence the dilemma for one who is in a place without a community, or passing very briefly through a place with a community.
However, day / night is an empirical matter and has nothing to do with human convention. Therefore, whether there is a community and how long you stayed is irrelevant. This is true even in the Polar according to the Shittos that day / night is determined by the position of the sun (which is certainly the Rebbe’s position), day / night remains an empirical matter, and not subject to human convention. Thus, the above letter is not relevant here at all.

2. Incorrect. Sefirah is counted at לילה. In “normal” locations, Tzeis is לילה. In unusual locations, it may be something else… in fact your next point demonstrates this… did the Jews of far Northern Europe who followed RT not count Sefirah?

3. Correct, but I believe they do this as minutes and not degrees.

There were Jews in Northern Europe that followed RT, or just hypothetically speaking?

[dirah]

So, how does the potential lack of tzeis affect tefilos and sefira as you cross the dateline?
Or how would taking a polar route from HND-JFK without sunset affect sefira as you cross the dateline?

I have attached a draft extract of hopefully future publication be"h.

[dirah]

There were Jews in Northern Europe that followed RT, or just hypothetically speaking?

What happened before the Gra and Alter Rebbe?

[AsherO]

What happened before the Gra and Alter Rebbe?

Good question. Was R”Ts Shkiya the normative practice, or is that something we surmise because we don’t have other documented Shittos? I really don’t know.

[dirah]

Good question. Was R”Ts Shkiya the normative practice, or is that something we surmise because we don’t have other documented Shittos? I really don’t know.

Yes it was the absolutely normative practice.
I always wonder how people of that generation must have felt to discover at some point in their lives that the times for Shabbos "changed", and Shabbos came in earlier that they were used to.
[Maybe it wasn't such a big deal because people brought in Shabbos early anyway?]

See the file here:

I have attached a draft extract of hopefully future publication be"h.

[dirah]

Using Zmanim charts to predict Zmanim works pretty well for most flights, but up far north its like trying to gaze into a crystal ball. Minor flight variations make major changes.

By the way, this is easily demonstrated with the two flights mentioned at the outset of this thread, that left within an hour of each other. MyZmanim would have presumably given similar times, but even one glance at the flightmap shows how different they were, ANA flight certainly had a night of few hours, whereas JAL gave us this whole discussion:

https://flightaware.com/live/flight/JAL6/history/20220526/0210Z/RJTT/KJFK
https://flightaware.com/live/flight/ANA110/history/20220526/0130Z/RJTT/KJFK

[gozalim]

1. That letter is something else entirely. The question there was not whether it is day or night, but which day of the week (Shabbos). Day of week is not an empirical fact, i.e. there is nothing in nature or astronomy to say its Monday or Tuesday, (i.e. days are just clones). Rather, days of the week are a human convention, i.e. people decide what day is Sunday, Monday … Shabbos, (hence places where people changed day of the week, with a recent example here,) and why a Dateline became necessary, and lehavdil, for Jews, all of that is with the Koach of Torah. It is about this that the Rebbe says (as expanded more in various Sichos, and LA’s Rosh writes about it at length in Migdal Ohr) that there is a connection between Shabbos and the way it was first established (perhaps even unwittingly) by the first Yidden who lived there, and hence the dilemma for one who is in a place without a community, or passing very briefly through a place with a community.
However, day / night is an empirical matter and has nothing to do with human convention. Therefore, whether there is a community and how long you stayed is irrelevant. This is true even in the Polar according to the Shittos that day / night is determined by the position of the sun (which is certainly the Rebbe’s position), day / night remains an empirical matter, and not subject to human convention. Thus, the above letter is not relevant here at all.

2. Incorrect. Sefirah is counted at לילה. In “normal” locations, Tzeis is לילה. In unusual locations, it may be something else… in fact your next point demonstrates this… did the Jews of far Northern Europe who followed RT not count Sefirah?

3. Correct, but I believe they do this as 72 minutes and not 16.1 degrees.

1. I know what that letter was about, but did not realize the extent to which the subjects differ from each other on this issue. Thanks.
are there no opinions that debate the application of inflight zmanim/apply מקום שיצא משם until landing?

2. true. yet from עלות we avoid a bracha מספק (and in siddur AR applies this to חצות in much of northern Europe, as discussed here). is there no ספק regarding a bracha before צאת?

general: I'm sure that, following AR approach to zmanim, the 'length of night' would not be relevant to this sha'alah on this flight. we're guessing at the possible considerations of a Rov who did come up with a ס"ס in this case. what factors or דעות יחידים would contribute a partial ספק here, and what role does "very short night" play in those?

[Something Fishy]

Sefirah is counted at לילה. In “normal” locations, Tzeis is לילה. In unusual locations, it may be something else… in fact your next point demonstrates this… did the Jews of far Northern Europe who followed RT not count Sefirah?

Exactly, which is why we counted at the "darkest" part if the night in Iceland a couple years back.

[Dan]

By the way, this is easily demonstrated with the two flights mentioned at the outset of this thread, that left within an hour of each other. MyZmanim would have presumably given similar times, but even one glance at the flightmap shows how different they were, ANA flight certainly had a night of few hours, whereas JAL gave us this whole discussion:

https://flightaware.com/live/flight/JAL6/history/20220526/0210Z/RJTT/KJFK
https://flightaware.com/live/flight/ANA110/history/20220526/0130Z/RJTT/KJFK

Oh boy.
MyZmanim is actually based on the ANA flight. They didn't have an option for the JAL flight...
Those route differences are wild. Was not expecting that.

[dirah]

are there no opinions that debate the application of inflight zmanim/apply מקום שיצא משם until landing?

In “normal” places? I am not aware of anyone who holds that in accepted practice with regards to Tefillos etc. There are many opinions who are meikal when flying west with regards to the four minor fasts specifically, but that is because the force of these fasts (שלא בשעת השמדות) is מכח מנהג, and the minhag never covered such a phenomenon.

2. true. yet from עלות we avoid a bracha מספק (and in siddur AR applies this to חצות in much of northern Europe, as discussed here). is there no ספק regarding a bracha before צאת?

Two big differences between עלות and צאת.
1. The time between עלות and sunrise is ודאי יום, but the חכמים instituted not to do מצוות של יום at עלות so as to avoid mistakes. Whereas (much of the time) between sunset and צאת is ספק יום ספק לילה.
2. According to the Alter Rebbe in the Siddur, עלות is at around 16.1 degrees but צאת is around 6 degrees. That is why up North, where the sun reached 6 degrees but not 16.1 degrees, there was night (after Tzeis of 6 degrees), but midnight was also עלות.

I'm sure that, following AR approach to zmanim, the 'length of night' would not be relevant to this sha'alah on this flight.

It seems that it would be relevant. The Alter Rebbe in the Siddur that you quote speaks of a place where the sun set below six degrees. That doesn’t seem to have happened on this flight.

[Dan]

In “normal” places? I am not aware of anyone who holds that in accepted practice with regards to Tefillos etc. There are many opinions who are meikal when flying west with regards to the four minor fasts specifically, but that is because the force of these fasts (שלא בשעת השמדות) is מכח מנהג, and the minhag never covered such a phenomenon.

I wish DDF was around when I flew to Hawaii on Taanis Esther 16 years ago   

[aygart]

1. The time between עלות and sunrise is ודאי יום, but the חכמים instituted not to do מצוות של יום at עלות so as to avoid mistakes. Whereas (much of the time) between sunset and צאת is ספק יום ספק לילה.

Isn't only 13.3 minutes safek?

[dirah]

Isn't only 13.3 minutes safek?

That is one opinion. There are tons more.

[aygart]

That is one opinion. There are tons more.

That holds bein hashmashos is more than 3/4 mil? Or that have the mil longer?

[dirah]

That holds bein hashmashos is more than 3/4 mil? Or that have the mil longer?

There are three shitos how long a Mil is - 24, 22.5, 18, which all affects how long 3/4 Mil is.
Then there is the question of when this time frame starts and ends.
And whether they are calculated as fixed times a whole year ("minutes") or represent a position of the sun at the equinox ("degrees").
All of this is the opinion of Rabbah according to R' yehudah who says that its 3/4 of a Mil.
Other Tannaim and Amoraim have different opinions, and there is further debate what they hold, and who the halacha is like, and how to resolve it with other Sugyos that imply differently.
That is why entire Seforim are written on this subject alone.

[MeirS]

https://onemileatatime.com/news/american-airlines-12-hour-flight-dfw-lax/

Someone was reading this during their flight, turned to the crew and said "Hey, wait a second. We've got an issue..."