Why was the 22nd the last day of summer? It didn't seem like it.

Why was the 22nd the last day of summer? It didn't seem like it.

— Betty L., Medford

So Betty, we're guessing that if you didn't put the shorts and sandals away then, you got the message Tuesday morning.

The season geeks at the Since You Asked Institute for the History of Science say there's some variation in this. The seasons are thought to start on different dates in different places based on astronomical stuff and the weather.

In the Northern Hemisphere, Sept. 22 was the autumnal equinox, the point halfway between the summer and winter solstices. Days are longest at the summer solstice and shortest at the winter solstice. By the equinox the days have been growing shorter for three months, or since the solstice, and are nearly equal to the nights.

That's because Earth's axis tilts about 231/2; degrees from being perpendicular to the plane of Earth's orbit, so that the Northern Hemisphere has longer days for about half the Earth's annual orbit around the Sun. The ancients were tuned in to all this. People from the Ancient Egyptians to American Indians to the builders of Stonehenge created structures aligned to the solstices and equinoxes.

Although we consider summer to run from solstice to the equinox, other cultures have used those times to mark the middle of seasons. The Chinese traditionally put the start of summer at May 5. That's close to the old Irish calendar. And don't forget that Shakespeare's "A Midsummer Night's Dream" puts midsummer at the shortest night of the year, the summer solstice.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to youasked@mailtribune.com.