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Name:  Marsha Carlisle
Status: Educator
Age: 40s
Location: N/A
Country: N/A
Date: N/A 


Question:
I am trying to find the current time in Antarctica. It is 2:30 p.m. Nov. 15, in Montgomery, Alabama USA. What time would it be in Antarctica? Is the time the same for the entire continent, or do different regions have different time zones? Thanks for the information.



Replies:
Perusal of a globe will be helpful. The Earth is divided into 360 orange-segment-like segments, each a degree of longitude. 0 degrees is that straight line which goes from North to South pole through Greenwich, England. Proceeding West from there we find New York at longitude 75 degrees West, Los Angeles at 120 degrees West, the International Date line at 180 degrees West, Tokyo at 145 degrees East, Cairo at 30 degrees East, and then back to jolly old England.

By habit we have two forms of timekeeping. We can measure time starting from one fixed event, for example the instant when the Sun was directly overhead at Greenwich ten days after the fourth winter solstice following the birth of Jesus of Nazareth. That would be Greenwich Mean Time (GMT) in the Gregorian Anno Domini calendar. 12 PM GMT December 10, 1999 A.D. Gregorian is thus a wholly unambigous time which occurs at the same instant for everybody everywhere.

We can also measure time by our local schedules, which revolve around the Sun. That is, we can call lunchtime 12 PM. That is, we set the time when the Sun is directly overhead for us, which is when we eat lunch, to be 12 PM local time.

Looking at the globe, we see that local time will be different for folks living at different points on the Earth's surface. When it is 12 PM local time for me in Los Angeles, the Sun is overhead. But the Sun is not overhead at that instant if you live in New York -- indeed, it is halfway between lunch position (overhead) and dinner position (setting). To see this you really must look at your globe, and image shining a flashlight at it. When the flashlight shines directly on California, it shines on New York at an angle. So when it is 12 PM local time in L.A. it is after 12 PM local time but before 6 PM local time (dinnertime) in New York. In fact it turns out to be tea-time, 3 PM.

Ordinary folks tend to use local time, so that, for example, the head of Alcoa can say the workdays for Alcoa workers worldwide starts just after breakfast = 9 AM local time, and so McDonald's can order beef patties on standby everywhere at dinnertime = 6 PM local time. What a pain it would be if McDonald's had to specify a different GMT time for the patties to go on standby for every store located in a different part of the world!

On the other hand, the military, ship and airplane navigators, and radio operators, and other folks who interact regularly with other folks at quite different points on the Earth's surface need to be sure everyone agrees on when certain things occur (flaps up, gear up, nose down, engines off -- oops!). So they tend to use GMT.

Now look at the globe and notice that, at any instant of GMT, you can find someone somewhere on Earth for whom local time is every conceivable minute from 12 midnight to 12 noon. All you need to do is find the correct longitude.

Also notice that Antarctica, lying as it does athwart the South Pole, contains all the lines of longitude. Hence, for any instant of GMT, you can find someone in Antarctica for whom local time is also every conceivable minute from 12 midnight to 12 noon.

So the answer to your question is: it can be whatever local time you wish to pick, varying from about 8:30 AM 11/15/99 (the local time on the East side of the International Date Line) to 8:29 AM 11/16/99 (the local time on the West side of the International Date Line). At the same longitude as Montgomery (somewhere in the Bellinghausen Sea, for example), the local time in Antarctica is the same as it is in Montgomery. At McMurdo Sound in the Ross Sea, it is a couple of hours earlier, and in the Weddell Sea it is a number of hours later.

Grayce



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