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This Week: We’re Closest to the Sun

This Week: We’re Closest to the Sun

One misconception we often read in letters, emails, and comments from our readers is the idea that it’s cold in the winter time because the Earth is father from the Sun. While this assertion may sound good, unless you live in Australia, or some other location “down under” the Equator, it’s actually just the opposite.

This week, (on January 4, 2012, at 8 p.m., Eastern Time, to be exact) the Earth will reach perihelion, its closest point to the Sun for the year.

Perihelion can fall anywhere between January 2 and January 6 in a given year. At that point in its orbit, the Earth is 91,407,282 miles from the Sun, a difference of about three million miles from its farthest point, or aphelion. Earth will reach aphelion on July 5, 2012, at 4 a.m., Eastern Time, at a distance of 94,509,130 miles from the Sun.

It may seem strange to learn that, while the U.S. and Canada are experiencing their coldest temperatures of the year, the Earth is actually closer to the Sun than at any other time during the year.

Even though most of us learned in school that seasons are controlled by the tilt of the Earth’s axis, rather than by its distance from the Sun, many people forget. We experience summer or winter conditions based on whether our half of the Earth is pointed toward the Sun or away from it. While we’re battling ice and snow in the Northern Hemisphere, our neighbors to the south are enjoying summer, and vice verse.

A three million-mile change in relative distance may sound like a lot, but our overall distance from the Sun is so great that this otherwise large figure amounts to a drop in the vast astronomical bucket of infinite space. This slight change in distance has virtually no effect on our weather throughout the year.

So, while you’re shivering and scraping the ice off of your car’s windshield this winter, try to remember that the Sun is actually three million miles closer than it was in July. Maybe that will help you feel a little warmer.

5 comments

1 Jaime McLeod { 01.10.12 at 9:06 am }

Robert,
Here is an answer to your question from our astronomer, Joe Rao:

If I am interpreting this question correctly, the reader is asking why it is that the Sun is setting later each day, but not rising earlier each day . . . at least during early January?

There are three reasons: the tilt of the Earth’s axis, the Earth’s elliptical orbit around the Sun and the fact that the Earth rotates in 23 hours 56 minutes and 4 seconds and not exactly in 24-hours. As a result of these three factors, astronomers have devised a “mean” or “fictitous” Sun that we use to set our clocks.

But as those who have sundials in the yards can tell you, if you use the actual Sun to tell time, it sometimes will be off by as much as 10 or 15 minutes . . . either too slow or too fast relative to your clock or watch. In fact, if you do have a sundial, it’s likely you’ll also have a plaque or sign next to it which provides you with corrections that you would make to your sundial readings, so that it will more accurately conform with your clock.

Such corrections are called “The Equation of Time.”

Okay . . . so basically what was happening was, that back in early December — about 2-weeks before the winter solstice — the Sun was running “fast.” That is . . . it was crossing the meridian about 10 minutes before local noon. As a result, it was getting to the western horizon early and was setting earlier than at any other time of the year. But as December wore on, the difference between sundial and clock time diminished. On Christmas Day, they actually were the same (Equation of Time = 0). But since then, the Sun has been lagging some minutes behind the clock, so it is now crossing the meridian after 12 Noon (so it’s now running “slow”). So it is also taking a bit longer to reach the eastern horizon to rise.

That’s why the earliest sunsets and the latest sunrises do not coincide with the winter solstice. And that is why those who carefully watch the sky probably have noticed that while the afternoons have gotten a little brighter in recent weeks, the mornings have actually gotten a little darker. Again . . . the earliest sunsets come about two weeks before the winter solstice and the latest sunrises come about two weeks after the solstice. Look in the Almanac and compare the times of sunrise and sunset on December 7 against the times on January 4.

The shortest amount of daylight still is measured on the solstice day, but the time scale for sunrise versus sunset ends up a bit lopsided because of the three factors that I mentioned above.

In the calendar pages for the Almanac, I have always provided the dates of the earliest and latest sunrises and sunsets as well as those dates when the Equation of Time = 0. Sadly, in recent years this information has instead been replaced with historical or other data.

With Kindest Regards,
– joe

2 Jaime McLeod { 01.06.12 at 9:18 am }

Hi Robert,
I’m not ignoring you. We’re working on getting an answer to this from our astronomer.

3 Jaime McLeod { 01.05.12 at 10:42 am }

Maggie, It’s not the wobble that changes the seasons (the axis does wobble somewhat, but it’s only noticeable over the course of tens of thousands of years). As we revolve around the Sun, the Northern and Southern Hemispheres take turns being inclined toward the Sun, but it’s not because the axis shifts, it’s because of the angle in relationship to the sun. Here’s an animation that should help you visualize it better.

4 maggie { 01.04.12 at 2:31 pm }

I’ve always had a problem with ‘spatial’ concepts and the one which I wish someone would help me to understand is, if the earth sits at a constant 26-or-so degree tilt, it seems that we would not have seasons because of the fixed angle of our planet — why doesn’t the earth’s ‘wobble’ (the seasons) change the degree of the earth’s tilt? Anyone?

5 Robert Duff { 01.04.12 at 9:44 am }

Dear Jamie,
As the days begin to lenghten in January, (for us here in the northern hemisphere)
the seconds are added at the end of the day and not equally between morning and
evening? Why is that?
Thanks,
Robert

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