MELISSA BLOCK, HOST:
Today, of course, is Labor Day, a day we honor the contributions of American workers. It's also unofficially end of summer - pools close, vacations end and kids return to school. Technically though, autumn doesn't begin until September 22 - another three weeks from now. Astrophysicist Adam Frank reflects on these two different dates and what they reveal about how we understand time.
ADAM FRANK: When it comes to experience, we all know that summer really ends on Labor Day. And in that division between the ways we meter time for science or business and the way we actually live time, there is a Labor Day lesson we might keep close to our hearts all year long. My first experience of this truth came when I was just a kid of ten. It was a warm, lazy late summer afternoon at the Newark YMCA day camp my sister and I attended. I was sitting by the swimming pond, looking up at the trees and the blue sky when it happened. A single falling leaf spun downward into my vision. It fell in a slow spiral until it dropped silently on to the water's surface. It was at that moment that I knew. I knew without anyone telling me or showing me a calendar that summer was over. I had never had that kind of experience of time before. I had never been old enough to feel the transition from one season to the next so explicitly, so concretely. For a kid who was already obsessed with astronomy and cosmic time that single leaf served as an introduction to time's other reality - the one that tells stories through our own most intimate experience. There's always a tension between how a culture measures time and how people experience it for themselves. Every society finds its own way to organize the day into useful divisions for getting basic needs accomplished. Every culture divides the year up into calendars pockmarked with festivals and holidays. Today, we find our time sliced up into ever-finer increments and with ever-higher expectations for how much we can produce in a given bundle of minutes or hours. But our bodies know differently. Born of the natural world, evolved across hundreds of thousands of generations in field and forest, rock and water's edge, we have within us another understanding of time. There is always that morning in late summer when you step outside and you can smell autumn. It's just a hint of a change, a certain kind of coolness and the color of the light but you know it as soon as it hits. Some half-year later the same recognition will hit again when the first scent of warm soil and growth tells you you're standing at the undefined cusp of late winter and early spring. These days can't be set down on a calendar a year in advance. They can't be planned for. Their appearance is a testament to fact that we more than rational calculating machines lifted miraculously above the natural world. Instead, we are always woven into the fabric of that world.
BLOCK: That's Adam Frank. His book, "About Time: Cosmology and Culture at the Twilight of the Big Bang," will be out in paperback this month.
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BLOCK: This is NPR News.
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