I want to wish yo a happy Fall Equinox Day. For a moment, 8:04 tonight to be exact, the earth’s axis will be oriented so no part of the planet is tilted toward or away from the sun. After that moment, the Equinox is over. Those of us here in the northern hemisphere start tilting away, heading for the Winter Solstice. Many people believe that earth’s seasons are caused by a change in our distance from the su; but, that distance doesn’t change much during the year. It’s all about tilt. For the past six month, our half of the planet has been tilted toward the sun, meaning more direct sunlight and longer days. Since the Summer Solstice in June, we’ve started to tilt back the other direction. Days get shorter and our sunlight gets shorter.
The Equinoxes and Solstices mark what are called “Astronomical” seasons. The dates and lengths of the seasons vary year to year, because of earth’s orbit around the sun. For meteorologists, that’s a problem. Temperature, rain and snow can’t be compared if the seasons don’t start and end at the same time every year. So, they use “meteorological” seasons which closely follow the calendar and match annual temperature changes. Meteorological Summer is the three warmest months of the year, on average, June, July and August. Winter is the three coldest months of the year, average, December, January and February. The three month periods in between are Fall and Spring.
There’s your science lesson for the day. Either way, Fall is definitely here now.
