We've got a doubleheader of astronomical action Wednesday: The spring equinox, which marks the beginning of spring, along with the final "supermoon" of the year.
Both will occur on Wednesday: The equinox at 5:58 p.m. EDT and the full moon/supermoon less than four hours later at 9:43 p.m. EDT, EarthSky reported.
The equinox is the precise moment the sun's rays shine directly on the equator.
It's one of two days out of the year – the other being the autumnal equinox in September – when the Earth's axis is tilted neither toward nor away from the sun, resulting in roughly 12 hours of daylight and 12 hours of darkness almost everywhere on Earth.
So it's an "equal night," which is where the word equinox originated: the two Latin words aequus (equal) and nox (night), according to the National Oceanic and Atmospheric Administration. Each day for the next three months, the sun will continue to get higher in the sky – and the daily amount of daylight longer – until the summer solstice in June.
It's also one of only two days each year that almost every spot on Earth – except the poles – experiences a sunrise at due east and a sunset at due west.
Meteorologists, who define the seasons differently, said spring began on March 1.
And for the folks down under in the Southern Hemisphere, the autumnal equinox will be Wednesday, marking the first day of autumn.