Earth just got another dazzling glamor shot, thanks to a satellite that snapped its photo on March 20, spring equinox. This image shows half of the planet illuminated in light and the other permeated in the dark, like a black and white cookie.
This beautiful symmetry is no surprise to anyone who knows anything about the equinox. In Latin, equinox means "just night". Twice a year, in March and September, the equinox occurs when the amount of daylight and darkness is almost the same at all latitudes, according to the National Oceanic and Atmospheric Administration (NOAA).
Why aren't equinoxes more common? The answer has to do with Earth's tilt. Because the planet is tilted on its axis about 23.5 degrees, daylight is usually unevenly distributed across the planet. Depending on where the soil is in its orbit around the sun, the northern hemisphere or southern hemisphere will have longer days or nights. [Earth Pictures: Iconic Images of Earth from Space]
"During two special times twice a year, the tilt is actually perpendicular to the sun, which means that the earth is just illuminated in the northern and southern hemispheres," said C. Alex Young, vice president of science of Heliophysics Science. Division at NASA's Goddard Space Flight Center, which previously told Live Science.
In other words, the sun is directly above the equator at noon during an equinox.
Last week, equinox happened at 5:58 EDT Wednesday (March 20), marking the first astronomical day spring to the northern hemisphere. However, the new image was taken several hours before 8:00 am EDT at the GOES EAST satellite.
Then, GOES satellites, also known as the geostationary operational environmental satellite system, are a network of Earth observation satellites operated by NOAA. They collect information on weather forecasts, severe storm tracking and meteorology research.
Originally published on Live Science .