Equinox is the midway point between solstices.
Equinox represents balance whether it is Spring or Fall Equinox.
The day of equinox has the same number of hours of light and dark. It is exactly even, thus equinox. The day that is the balance between summer solstice and winter solstice is called Fall Equinox. The day that is exactly between winter solstice and summer solstice is Spring Equinox.
You can balance an egg on its end on Equinox Days.
Here’s a fun activity. Try balancing an egg on equinox. The spin of the Earth is ‘just right’ that you can balance an egg on Equinox. I have witnessed this with friends. It’s a fun activity to try with kids too. You can add some science teaching and show them some videos from NASA as to why the spin of the Earth helps them balance an egg.
Balance is the theme for Equinox because the daytime and nighttime are exactly even.
Equinox marks the CENTER of the next season.
Spring Equinox marks the center of Spring (not the beginning of it). Fall Equinox marks the center of Fall (not the beginning of it).
A ‘weather person’ says it is the beginning of a season because they must mathematically cut the year into exact days and thus you will see meteorlogical seasons which are different than sidereal seasons.