Ask A Scientist© Environmental Earth Science Archive

 >
 >    name         Marsha Carlisle
 >    status       educator
 >    age          40s
 >    EMAIL
 >    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.
 >

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    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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