Throwback Thursday: The Earth’s Analemma (Synopsis)

“Life is tragic simply because the earth turns and the sun inexorably rises and sets, and one day, for each of us, the sun will go down for the last, last time.” -James A. Baldwin

But each day is a chance for hope, learning something new and experiencing something wonderful. In fact, in just a couple of days, it will be the June solstice here on Earth, where the Sun reaches its highest (or lowest) position in the sky for Northern (or Southern) hemisphere observers!

You might look at something like this and assume that the Sun -- if you took a picture of it at the same time every day -- would make the shape of a straight line, or possibly a curve. I wouldn't blame you if you thought that, but what we get instead is much more fascinating.

Image credit: Tunc and Cenk Tezel, via Astrosurf. Image credit: Tunc and Cenk Tezel, via Astrosurf.

This shape is known as an analemma, and is a figure-8 here on Earth. What causes it? Go read the whole story and find out!


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solstice: the point at which Earth’s axis is maximally tilted with respect to the plane of our orbit

The tilt is pretty much constant over a year, isn't it? And the precession takes tens of thousands of years, without changing tilt (inclination) very much.

By wereatheist (not verified) on 19 Jun 2014 #permalink

That should be "Earth’s axis is maximally tilted with respect to a plane normal to the line between Earth and the sun"

'Time' on a clock is such an artificial human concept, to compensate for the fact that the length of a day, a solar day from noon (the time when the Sun is at its highest point in the sky) one day to noon the next day, isn't 24 hours.

It ranges from 24 hours 20 seconds around the Summer and Winter solstices to 23 hours 59 minutes 40 seconds around the Spring and Autumn equinoxes, so the exact time of noon varies throughout the year.

If you took your 365 day photo at exactly noon each day (instead of, say, 12 midday) wouldn't the Sun trace a straight vertical line instead of a closed curve?

By Wayne Robinson (not verified) on 20 Jun 2014 #permalink

Wouldn't Uranus be something other than a figure 8, considering it's tilted pretty much sideways? And you wouldn't get much of any shape on Venus, only getting something like 2 solar days per year. Kind of sad that you didn't go into these weird cases with a bit more detail, but maybe that would have made the post way too long.

*It made me kind of sad that you didn't go into these weird cases...

Realized too late that as typed it didn't mean what I meant it to mean.