Geography Reference
In-Depth Information
Why is Christmas celebrated on December
25th?
Scripture is silent about the date of Christ's birth, which only began to be celebrated sev-
eral centuries after the event. In pre-Christian Northern Europe, there was widespread
belief in a sun god whose birth date was celebrated on the winter solstice. On that date,
the sun is lowest in the daytime sky in the Northern Hemisphere, but rises somewhat
everyday thereafter until the summer solstice. Thus, the date on which the sun began
to rise symbolized the sun god's birth. As Christianity spread into those lands, mixing of
religious beliefs occurred, one of which was to substitute Christ's birth for the sun god's
on the winter solstice. Subsequent refinement of the calendar resulted in the few-day's
lapse that now separates Christmas and the winter solstice.
Hot or Cold? Adjust Your Altitude
Altitude has an important impact on climate. The rule of thumb is that temperature and elev-
ation are inversely related. Or in every day speech, “the higher you go, the cooler it gets and
vice versa.” Thus, highland areas have cooler climates than lowland areas.
Consider this example: Fewer than 200 miles separate Guayaquil and Quito, the two largest cities in
Ecuador. But the annual average temperature is 77° F in Guayaquil and only 56° F in Quito. The ex-
planation is that Guayaquil is virtually at sea level while Quito is up in the Andes at an elevation of
about 9,250 feet. Despite being nearly on the equator, the city does not experience the warm climate
one would normally expect at that latitude, due to the altitude factor. How does that work? Glad you
asked.
Warming the atmosphere
Part of the answer concerns how the atmosphere obtains heat. A portion of the solar energy that
reachestheEarth(18percent)isabsorbeddirectlybytheatmosphere, whileanevenlargerpercentage
(32 percent) reflects back into space. The largest portion by far (50 percent), however, is absorbed by
the Earth, which then re-radiates that heat into the atmosphere. Thus, solar energy turns Earth's sur-
face into something like a giant frying pan that heats the atmosphere above it. Generally, therefore,
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