Weather forecasts for the Fourth of July week are predicting high temperatures in the 90s and even 100s across much of the country. So it may surprise you to learn that at 1:00 p.m. EDT on Friday, July 6th, Earth will reach that point in its orbit where it is farthest from the Sun in space, known as aphelion.
Aphelion: Earth’s Distance From the Sun
At the moment of aphelion, the Sun will be 94,507,803 miles away (measured center to center), or 3,105,820 miles farther as compared to when the Earth is closest to it (called perihelion), which occurred last January 3rd. So we are 3.3% farther, from the Sun than we were in January; a change of only 1 part in 30, and makes a difference in radiant heat received by Earth of nearly 7%.
If you ask most people which month of the year they think Earth is closest to the Sun, most would probably say during June, July, or August. But our warm weather doesn’t relate to our distance from the Sun. It’s because of the 23.5-degree tilt of the Earth’s axis that the Sun is above the horizon for different lengths of time at different seasons. The tilt determines whether the Sun’s rays strike us at a low angle or more directly.
At New York’s latitude, the more nearly-direct rays at the Summer Solstice of June 21st, bring about three times as much heat as the more slanting rays at the Winter Solstice on December 21. Heat received by any region is dependent upon the length of daylight and the angle of the Sun above the horizon. Hence the noticeable differences in temperatures that are registered over different parts of the world.
A Climatological Fallacy
When I attended Henry Bruckner Junior High School in The Bronx, my ninth grade earth science teacher, Mr. Shenberg, told all of us that because we were farthest from the Sun in the July and closest in January, that such a difference would tend to warm the winters and cool the summers—at least in the Northern Hemisphere.
And yet the truth of the matter is that the preponderance of large land masses in the Northern Hemisphere works the other way and actually tends to make the winters colder and the summers hotter.
Interestingly, the times when the Earth lies at its closest and farthest points from the Sun roughly coincide with two significant holidays: we’re closest to the Sun around New Year’s Day, and farthest from the Sun around Independence Day. Actually, depending on the year, the date of perihelion can vary from January 1 to 5; and the date of aphelion can vary from July 2 to July 6.
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