Spring Equinox 2013 From Space

Yesterday, March 20 was the vernal equinox. That is, the moment in Earth’s orbit around the Sun where both hemispheres are equally lit. Not only did we get to experience an even 12 hours of daylight / 12 hours of night here on the surface, but it looked pretty cool in space as well:

GOES Satellite Captures Spring Equinox
Earth imaged by the GOES-13 satellite at 7:45 ET on March 20, 2013. Image credit: NOAA

As you can see, Earth is positioned with respect to the Sun in such a way that both the northern and southern hemispheres are equally lit. The image is a tad misleading as the straight line of the equator is oriented “directly” toward the Sun on the right, giving the impression that Earth’s axis is perpendicular to the plane of its orbit. But remember, Earth is tilted 23 1/2 degrees from the plane of its orbit, like this:

Axial Tilt of Earth. From Wikipedia
Axial Tilt of Earth. From Wikipedia

Putting all of this together and we have a representation of Earth in its orbit around the Sun, keeping its tilt in the same alignment year-round:

Earth's relative position to the Sun during its orbit. Not to scale, obviously. Source: Wikipedia
Earth’s relative position to the Sun during its orbit. Not to scale, obviously. Source: Wikipedia

So remember, Earth’s tilt is the reason for the season! Happy Spring!

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