The Spring and Autumn Equinoxes



A diagram showing how the Sun moves through the sky on an equinox.
Click on image for full size (20K GIF)
The spring and autumn equinoxes occur around March and September 21. These are special points in the Earth's orbit when the Sun appears directly above the Earth's equator. Day and night are the same length, about 12 hours.

The diagram to the left shows how the Sun may appear to move through your sky on an equinox, if you live at a latitude of 40° N, around Topeka, Kansas for instance.

The Sun is in between its altitude on the summer solstice (the highest point) and its altitude on the winter solstice (the lowest point). In a similar way, spring and autumn are in between summer and winter; the temperatures are neither very hot nor very cold, and the weather is not as extreme as in summer and winter.

Compare the Sun's height to what you would see in the winter or in the summer.

The Vernal and Autumnal Equinoxes



A diagram showing how the Sun moves through the sky on an equinox.
Click on image for full size (50K GIF)
We're still pretending that you're the person standing on the Earth in the picture to the left, living in Topeka, Kansas, around 40° N latitude. The picture on the left shows the view from the solar system (upper panel), and from on the surface of the earth (lower panel). Notice that some of the same features are labelled on each panel. In the upper panel, the Earth's axis is pointing into your computer screen.

The upper panel shows that on an equinox (which occurs around March and September 21), neither half of the Earth points directly towards the Sun. In fact, the Sun is at the equator, so both halves of the Earth are getting about the same amount of sunlight. For you in Topeka, the altitude of the Sun is about 50°, in between its altitude on the solstices. The bottom panel shows how this looks to someone standing on the ground in Topeka.

Equinox literally means "equal night". On the vernal (spring) and autumnal (fall) equinoxes, day and night are the same length. Neither hemisphere gets more sunlight than the other, so both have similar seasons (fall in one hemisphere and spring in the other).

How high the Sun gets in your sky, and how long it is above the horizon during the day, depend not only on the season, but also on your latitude.

The Vernal and Autumnal Equinoxes



A diagram showing how the Sun moves through the sky on an equinox.
Click on image for full size (50K GIF)
We're still pretending that you're the person standing on the Earth in the picture to the left, living in Topeka, Kansas, around 40° N latitude. The picture on the left shows the view from the solar system (upper panel), and from on the surface of the earth (lower panel). Notice that some of the same features are labelled on each panel. In the upper panel, the Earth's axis is pointing into your computer screen.

The upper panel shows that on an equinox (which occurs around March and September 21), neither half of the Earth points directly towards the Sun. In fact, the Sun is at the equator, so both halves of the Earth are getting about the same amount of sunlight. For you in Topeka, the altitude of the Sun is about 50°, in between its altitude on the solstices. The bottom panel shows how this looks to someone standing on the ground in Topeka.

Equinox literally means "equal night". On the vernal (spring) and autumnal (fall) equinoxes, day and night are the same length. Neither hemisphere gets more sunlight than the other, so both have similar seasons (fall in one hemisphere and spring in the other).

How high the Sun gets in your sky, and how long it is above the horizon during the day, depend not only on the season, but also on your latitude.


Last modified prior to September, 2000 by the Windows Team

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