Summer Solstice: A Celebration
of the Sun
by Ned Rozell
June 21, 2004
Alaska - In this colorful blur of frenzied fishing trips, sweaty
softball games, maniacally maturing vegetables, road-weary relatives,
and steadfast sleep deprivation we call summer, it's time to
reflect on the season's source - the sun.
At summer solstice, the sun
once again bakes Alaskans due to the tilt of the earth's axis
that leans us toward the sun. The longest day of the year officially
occurred June 21, and varied in length from 24 hours in Barrow
to just over 17 hours of possible daylight in Ketchikan.
'Summer Solstice Eve
Sunset in Ketchikan, Alaska'
photo by Tom
The word solstice comes from the Latin term "solstitium,"
which translates into English as "sun standing still."
Alaskans upon whom the sun sets this time of year can see the
sun standing still for three or four days around solstice, as
the sun rises and sets in nearly identical places before continuing
its race around the horizon.
Some sunny facts, gleaned from
a number of good books:
- The sun is our closest star,
at about 93 million miles away from the earth. The next closest
star, Alpha Centauri, is more than 250,000 times farther away
from us than is the sun.
- The sun is a medium-sized
star, measuring about 865,000 miles in diameter; it's about 109
times larger than the earth.
- The sun's energy comes from
its highly compressed core, where hydrogen nuclei collide at
incredibly high speeds, fusing to form helium nuclei and generating
temperatures of 40 million degrees F. This process generates
the sun's energy, which gradually works its way to the surface
and is radiated off.
- The earth receives only about
two billionths of the sun's total energy output, yet that tiny
fraction is enough to sustain life.
- Of the sun's energy that reaches
the earth without being bounced off by clouds or deflected by
other particles in the atmosphere, most is spent evaporating
moisture into clouds, and much of the remainder is converted
into carbon-based life by plants through photosynthesis.
- The sun is about 5 billion
years old, and should continue burning for another 5 billion
- Because the earth's path around
the sun is an ellipse rather than a circle, the earth is actually
closer to the sun in January (at about 92 million miles away)
than in July (94 million miles distant).
- Ancient cultures personified
the sun with names such as: Ra (Egyptians); Helios (Greeks);
Sol (Romans); and Tonatiuh (Aztecs).
- The Romans coined the term
"dog days of summer," believing high temperatures from
about July 3 to August 11 were the doings of Sirius, the dog
star, which is the brightest star in the summer sky (in areas
where you can see stars in summer).
- June 21 seems a fitting day
for the first day of summer in Alaska because hotter temperatures
often come in July and August despite the fact that the amount
of solar radiation we receive peaks on the solstice. This heat
lag happens because the earth still holds much of the cold of
winter, which won't be baked off until the summer wears on.
- If the beginning of summer
is defined as the onset of the three hottest months of the year,
it begins about May 25 in Arizona, New Mexico and Texas; about
May 27 in Nevada, Louisiana, Georgia and Florida; about June
7 in New England, North Dakota, Minnesota, Wisconsin and Michigan;
and about June 15 in northern Maine.
To close out this mini-celebration
of the sun, a quote from Pliny the Elder, a Roman naturalist
who lived from 23-79 AD. Of the sun, Pliny wrote: "He furnishes
the world with light and removes darkness; he obscures and he
illuminates the rest of the stars; he regulates in accord with
nature's precedent the changes of the seasons and the continuous
rebirth of the year; he dissipates the gloom of heaven and even
calms the storm clouds of the mind of man . . ."
This column is provided as
a public service by the Geophysical Institute, University of
Alaska Fairbanks, in cooperation with the UAF research community.
Ned Rozell, is a science
writer at the institute. First published in 1995....
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