If you believe in myths and superstitions, this Friday, September 23, might be a good day to try and balance an egg on its end, avoid drinking water, or celebrate Persephone's return to the Underworld.

All those myths are associated with the September Equinox, which takes place at 9:04 a.m. coordinated universal time (2:04 a.m. MST) this Friday.

Whether the myths associated with the September Equinox hold any weight is up for debate, but here's what science says happens in the sky:

During the September Equinox (also known as the autumnal or fall equinox in the northern hemisphere), the sun crosses the celestial equator and moves south in the northern hemisphere. The sun will be directly over the equator during the equinox, and many people believe the result is 12 even hours of day and night.

But the "12 hours of daylight" notion isn't hard fact. Here's why, according to skywatcher website timeanddate.com:

"During the equinox, the length of night and day across the world is nearly, but not entirely, equal. This is because the day is slightly longer in places that are further away from the equator, and because the sun takes longer to rise and set in these locations."

And the sun doesn't set down in a clean line, either - it sets in a horizontal direction. But in Arizona, the amount of daylight and night time will be nearly equal. The sun is scheduled to rise on September 23 at 6:17 a.m., and set at 6:24 p.m. So we'll have about seven minutes more daytime than night time -- plenty of time to try balancing that egg.

To add to the fun, the planet Jupiter will reportedly be shining all night on the equinox, rising over the eastern horizon just after nightfall, and reaching its highest point after midnight.