The coming of autumn at 9:29 EDT last night (which I was pleased to see featured in today’s Google Doodle) serves as the perfect segue to a theme of mine as Executive Director of the National Science Teachers Association: We must teach students to understand that there are testable predictions about that physical world that together comprise a body of knowledge known as “science.” And we cannot debate those “facts.” But what we can do, and must do better, is teach our students how those facts can be used to make societal decisions, such as whether daylight savings time is a benefit or not to our society.

Autumn began last night at 9:29 PM EDT as the sun crossed the equator. For those of us living at mid latitudes, the hours of daylight will now be fewer than those dark. Indeed the rate at which the day disappears is at its quickest, slowing only as we approach the dark and cold days of December and January.  Our understanding of the tilt of the Earth’s axis and its motion around the Sun allows us forecast these changes with a high degree of confidence, a simple example of how science leads to testable predictions about the physical world.

Daylight Saving Time ends at 2:00 AM on Sunday November 2, at least here in most of the United States. But not everywhere, which leads to the debate over the use of daylight saving time–something that has been controversial since Benjamin Franklin proposed it. Arguments in favor point to better use of daylight and energy conservation. Opponents argue against the nuisance of changing clocks, disrupted sleep schedules, the risk to school children due to poor visibility in the early hours, the conflict with religious law and practice, and the fact that farm animals don’t use clocks at all.

Daylight saving time is based on the science mentioned above but in itself is not science. While we can debate the costs and benefits of changing our clocks twice a year, we can’t ignore or legislate against the seasonal change in the number of hours of daylight. We can debate how we will respond and we can use the science to inform that discussion, but we may decide that other factors are more important and accept the predictable consequences of our decision.

As the Sun continues its southward trip and the days shorten, we turn back the air conditioning and turn up the heat against winter’s chill. For over a hundred years science has told us that increased combustion of fossil fuels will lead to a change in the planet’s climate. In 1896 Svante Arrhenius calculated a value of the amount of that change that is quite close to modern estimates. And just as we measure the days shortening, so we have we measured the planet’s beginning to warm. We can and must debate what to do with that information but we cannot pretend that it does not exist any more than we can deny the solstice.