Today (22 September) is the September equinox — we call it the autumnal or fall equinox in the northern hemisphere, but in the southern hemisphere it’s the vernal or spring equinox. The autumnal equinox is (astronomically speaking) the first day of fall, just as the vernal equinox is (astronomically speaking) the first day of spring.
❡ Little lessons: “‘Vernal’ and ‘autumnal’ are beautiful words. Let’s look them up in our dictionary (riverhouses.org/books).”
Whenever you’re investigating things temporal or calendrical, timeanddate.com is always a good place to start:
The seasons occur because the earth’s axis of rotation is not quite perpendicular to the plane of the earth’s annual orbit around the sun (it’s tilted by about 23º). The two solstices occur at the points in the orbit when the axis is tilted most directly away from the sun (in December, on the first day of northern-hemisphere winter), and most directly toward the sun (in June, on the first day of northern-hemisphere summer). The two equinoxes, in March and September, occur when the earth’s axis is “sideways” to the sun (so to speak), making the intervals of daylight and darkness equal (or very nearly so).
What calendrical events and astronomical transitions will you be marking in your homeschool this season? 😊