What is time?
Dr. Maureen Hunter | TLT President's Report January 2015
A 10-year-old’s question sparks a metaphysical journey from Plato to Dante to Einstein.
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BEING FROM THE NEW WORLD and a reader of western philosophy, I realize just how much we are all influenced by our western history and heritage. And one of the interesting things about having a child so much younger than her siblings is how adult she seems just from the exposure and influence of the older kids. This really hit home for me after eating dinner one recent evening.
My 10-year-old asks, “What exactly is time? Dante said in the underworld people can see the past and the future, but they can’t see the present.”
Thinking she’s referring to her friend named Dante, I look at her in confusion. “Dante said that? He’s only 10 years old.”
“Not that Dante!” she laughs. “Laura said that there was this guy named Dante who lived a long time ago, and he said that.”
“Oh, the Inferno Divine Comedy Dante. I haven’t read that book since college,” I chuckle.
“So what exactly is time?” she asks again.
I paused. I feel like the 4th Century philosopher Augustine when he wrote, “What is time? If no one asks me, I know. If I want to explain it to someone, I don’t know.” But then I think—
I’m a scientist, so I proceed.
“Well, Einstein said that the universe is not just space, that it’s also time. They’re part of one thing—a four-dimensional universe called spacetime. All events, places, moments in history, actions and so on are described in terms of their location in spacetime. Spacetime doesn’t evolve, it simply exists. But we perceive time as having an arrow.”
“What?” she retorts, scrunching her face.
“Time has a direction. It isn’t governed by the laws of physics, but it is set by the boundary condition of the Big Bang 13.7 billion years ago. As we move toward the future, entropy always increases. It didn’t need to start low, but for some reason it did. That’s the second law of thermodynamics.”
“Speak English to me, Mom,” she shrieks. “I don’t even know what you’re saying.”
“That’s why your room always gets messy. Things change positions. Species evolve. We perceive time as passing.” Then I think back to my favorite writing by Plato, his dialogue the Timaeus. “Have you ever heard of Plato?” I ask.
“Of course, Mom. That’s Laura’s code name for you, but she spells it P-l-a-y-D-o-h,” she answers.
“Oh, yeah, right,” I say. “Well, Plato defines time as the moving image of eternity. It’s like a movie reel. Time comes into existence, there’s a moment when it happens, and then it disappears into the past.”
“So how long does the present last?” she asks.
“Well, I don’t think it’s quantized,” I answer.
“English, Mom!” she croaks.
“If we could identify a moment of time that couldn’t be further divided into even the smallest time frame, that would be called the present,” I say. “But time seems to be continuous.”
“I guess that’s why you say time flies,” she exclaims.
“It does seem like the present’s only claim to its momentary existence is that it will soon cease to be.” Then I think back to Dante’s 10th canto of his epic poem Inferno: “In eternity, if there is no past and future, which is the only thing those people can see, then there is just the present—an eternal present. And that is what they can’t see. It’s what they lack.”
“I guess time’s just a mystery,” I say.
“I thought so,” she says and walks away seeming satisfied.
Maureen Hunter is the technical service manager for King Industries, Inc., in Norwalk, Conn. You can reach her at mhunter@kingindustries.com.