It May Be Hot But The Sun Is Far Away

At about 11 a.m. EDT (1500 GMT) on the Fourth of July, the Earth will reach that point in its orbit where it is farthest from the sun. Called aphelion, this location in Earth’s orbit puts the planet about 94.5 million miles (152 million kilometers) from the sun. That’s about 3.1 million miles (4.9 million km) more than the Earth’s closest distance to the sun (called perihelion), which occurred on Jan. 3. 

The exact difference in the distance between Earth’s closest and farthest points from the sun is 3,104,641 miles (4 996 435 km), or 3.28 percent, which makes a difference in radiant heat received by the planet of nearly 7 percent. The average distance between the Earth and sun is about 93 million miles (150 million km). [10 Extreme Planet Facts]

Closer doesn’t necessarily mean hotter

If you ask most people in the Northern Hemisphere which month of the year they think the Earth is closest to the sun, they may likely say it happens in June, July or August, some of the hottest months of the year.  

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 21 bring about three times as much heat as the more slanting rays at the winter solstice on Dec. 21. Heat received by any region is dependent on the length of daylight and the angle of the sun above the horizon.

So there are noticeable differences in temperatures that are registered over different parts of the world, including the Southern Hemisphere, where it is winter right now.

A climate fallacy

The Earth is farthest from the sun in July and closest in December, 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. When Earth is closest to the sun around New Year’s Day and farthest from the sun around Independence Day.

Depending on the year, the date of perihelion can vary from Jan. 1 to 5, while the date of aphelion can vary from July 2 to July 6.

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Posted on July 5, 2011, in Public Health & Safety. Bookmark the permalink. Leave a comment.

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