It's interesting to note that two important holidays in the United States
fall roughly at the times when the Earth is closest to and furthest from the
sun.
This week, temperatures reached all-time highs.
The days after Independence Day saw unusually high temperatures in several
regions of the world. You might be surprised to learn that our Earth will
reach the point in its orbit when it is furthest from the sun in space on
Thursday (July 6), at 4:06 p.m. Eastern Daylight Time (2006 GMT).
The sun's distance from our Earth at that time, known as aphelion, will be
94,506,364 miles (152,093,250 km) from center to center, or 3,103,330 miles
(4,994,325 km) farther than on January 4 when the Earth was closest to it
(perihelion). The difference in distance is comparable to 3.29%, which
results in a shift of only one part in 30 in the amount of radiant heat that
Earth receives.
Indeed, it comes as no surprise that the majority of people, when asked
what month of the year they believe the Earth is closest to the sun, would
most likely respond June, July, or August. Our proximity to the sun,
however, has nothing to do with our mild climate. The sun is above the
horizon for varying amounts of time depending on the season due to the
Earth's axis' 23.5-degree tilt. Depending on the tilt, the sun's rays will
either hit us at a low angle or directly.
At New York's latitude, the summer solstice on June 21 produces around
three times as much heat as the winter solstice on December 21 due to the
more nearly direct sunlight. The amount of heat that every place receives
depends on the length of daylight and the sun's angle above the horizon,
which accounts for the observable variations in temperatures throughout the
globe.
a fallacy in climatology
Mr. Saul Shenberg, my Earth Science teacher when I was a student at Henry
Bruckner Junior High School #101 in The Bronx, explained to us that because
we were closest to the sun in December and farthest away in July, the
difference would tend to warm the winters and cool the summers, at least in
the Northern Hemisphere.
That certainly made sense, but the reality is that the Northern
Hemisphere's abundance of massive land masses really tends to operate the
other way, making our northern winters colder and the summers hotter!
We are closest to the sun around New Year's Day and we are furthest from
the sun around Independence Day. It's interesting to note that these periods
approximately correspond with two important holidays in the United
States.
Aphelion almost falls on July 1, the day before Canada Day, the country's
official holiday.
But in reality, the dates of perihelion and aphelion might vary depending
on the year, from January 1 to five, and from July 2 to six,
respectively.
