The autumnal equinox an event which is celebrated around the world and it's when day and night will be almost equal in most locations. Astronomers also see this as when autumn officially starts in the Northern Hemisphere - even though meteorologists regard it as starting on September 1. Like the spring equinox in March, the autumnal equinox marks an astronomical turning point of the seasons. On the equinox, however, the orbital plane of the equator becomes geometrically aligned with the center of the sun so that neither hemisphere is tilted away or toward the sun (visualize Earth’s axis going into the screen in the image below): 
 
 From our Earthbound perspective, the sun appears directly overhead along the equator, and day and night are roughly equal in length (emphasis added — see No. Rex Features 2 The autumn equinox signals the end of summer and start of autumn for the northern hemisphere 
 
 What is the autumnal equinox? Ghigo used four samples of a dozen eggs each, which he attempted to balance on their large ends on a Formica tabletop each day between Feb. 27 and April 3, 1984. The next time the date will fall on the 21st is 2092 and in 2393 the equinox will occur on September 24.
– An eventful day on the equinox front: We've entered autumn, as of 10:21am EDT, per National Geographic. That means that Sept. 22 will see 12 hours of day and 12 hours of night in the Northern Hemisphere, and our part of the Earth will start to lean further away from the sun as we head into winter. If the arrival of autumn is a depressing signal for you that we're hurtling toward the upcoming cold-weather solstice, the magazine points out it could be worse, a la Game of Thrones: The angle of Uranus' axial tilt is so extreme that its winters last 42 years at a time. Some other tidbits as the leaves start to fall: The Washington Post offers a scientific Q&A for all things autumnal. Don't miss Google's main page, where, per SearchEngineLand.com, its Doodle continues the story of a bunch of rocks who were there with us to witness March's vernal equinox. The Sun does some myth-busting about first-day-of-fall egg balancing. Bustle offers some ideas—some practical, some hedonistic—for celebrating the change of season. Circle back to National Geographic for a list of celestial viewings this week, including a brightly shining Saturn.