At the poles, there is no eastern or western direction
By MUNGAI KIHANYA
The Sunday Nation
Nairobi,
14 November 2021
Joseph Wanyoike has
been having sleepless nights wondering about the poles of the Earth. He
asks; “Is it true that, at the poles, there is no eastern or western
directions? If that is the case, then from where does the sun rise and
set each day?”
Having lived all my
life a short distance (about 100km south) from the equator, I was
shocked when I moved to England for University studies to find that the
length of daytime there varies greatly from one month to the next. It
can be anything between 6 and 18 hours: yes, there are months of the
year when the sun stays visible in the sky for 18h! Here in Kenya,
daytime is always about 12 hours long all the time.
The farther one moves
from the equator, the greater the seasonal variation of the length of
daytime. Indeed, if you are far enough, you reach a point where the sun
doesn’t set during one day in the year. That is, there will be 48 hours
of continuous sunlight.
The latitude at which
this phenomenon begins is called the Arctic circle (in the northern
hemisphere) and the Antarctic circle (in the south). Conversely, in
these regions, there is also a time when the sun won’t rise at all for a
continuous period of 48 hours.
In the northern
hemisphere, the 48-hour sunshine happens around the 21st of
June and in the south, it occurs in December. Now, the farther one
travels past the Arctic and Antarctic circles, the longer this
phenomenon of continuous sunlight becomes. Thus, at some point it will
be 3 days, the 4, then 5 and so on until one reaches the pole where it
is 183 days of sun!
Yes; at the poles,
the sun remains permanently in the sky for 6 months without ever
setting! Then it sets below the horizon and stays out of view for
another 6 months. For that reason, east and west directions cannot be
defined.
So, how does the sun
behave when it is in the sky when viewed from the poles? It moves in a
circle round the pole staying just above the horizon and completing one
cycle every 24 hours. In the north, the sun pops out around the 21st of
March and stays, without setting, until the 21st of September.
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