The Arrival of Autumn
By Scott Stransky
Autumn arrived early this past Saturday morning. It is a common misconception to believe that on the day of the equinox, there are twelve hours of sunlight and twelve hours of night. By definition, at the equinox, there are twelve hours between when the center of the sun’s disk rises above the horizon and when the center falls below the horizon. Due to atmospheric refraction, even when the sun is completely below the horizon, some light still reaches the ground. Together, these effects add about fifteen minutes of daylight to each day.
Although the equinox itself was three days ago, today is the day with equal amounts of daylight and darkness. (To be precise, there is one less minute of day than night, but it will not get any more even than that this year.)
The Cambridge area should experience nice weather over the next couple of days. We might see some showers later this week.
Today: Sunny. High 74 F (23 C).
Tonight: Clear. Low 50 F (10 C).
Wednesday: Sunny. High 70 F (21 C).
Wednesday night: Clear. Low 55 F (13 C).
Thursday: Showers possible. High 70 F (21 C).
Thursday night: Showers possible. Low 60 F (15 C).