There are two moments each year when the Sun is located directly above the Equator and the Earth’s axis is neither tilted toward or away from the sun, making the hours of day and night relatively equal in length. These days are the spring and fall equinoxes.

The fall equinox occurs on Monday, Sept. 22, 2025 at 2:19 p.m. and marks the official beginning of fall in the northern hemisphere. The equinox is celebrated as a daylong event, but it’s really just a moment in time when the sun crosses the celestial equator. The equinox often brings on the northern lights, which also is known as the aurora borealis. Auroras are caused by the interaction of solar winds with the Earth’s magnetic field.

Disturbances in the Earth’s magnetic field are strongest and more likely in spring and fall. Folklore says that only on an equinox can an egg be balanced on its ends. However, it actually can be done on other days as well.