Why?
“Because atmospheres are parts of living processes. The mixes of gases can tell us if the planet is alive.”
Like here?
“Exactly. My programs have even predicted the Earth’s atmosphere at different times in history.”
You can’t predict the past, Dad.
“You can if you don’t know it yet.”
So how do you tell what kind of gases a planet has from a hundred light-years away when you can’t even see it?
I exhaled, changing the atmosphere inside our tent. It had been a long day, and the thing he wanted to know would take ten years of coursework to grasp. But a child’s question was the start of all things. “Okay. Remember atoms?”
Yep. Very small.
“And electrons?”
Very, very small.
“Electrons in an atom can only be in certain energy states. Like they’re on the steps of a staircase. When they change stairs, they absorb or give off energy at specific frequencies. Those frequencies depend on what kind of atom they’re in.”
Crazy stuff. He grinned at the trees above the tent.
“You think that’s crazy? Listen to this. When you look at the spectrum of light from a star, you can see little black lines, at the frequency of those stairsteps. It’s called spectroscopy, and it tells you what atoms are in the star.”
Little black lines. From electrons, a gazillion miles away. Who figured that out?
“We’re a very clever species, we humans.”
He didn’t reply. I figured he’d drifted asleep again—a good end to a fine day. Even the whippoorwill agreed and called it a night. The hush in its wake filled with the bandsaw buzz of insects and the river’s surge.
I must have dropped off, too, because Chester was sitting with his muzzle on my leg, whimpering as Alyssa read to us about the soul recovering radical innocence.
Dad. Dad! I figured it out.
I slipped upward from the net of sleep. “Figured out what, honey?”
In his excitement, he let the endearment slide. Why we can’t hear them.
Half asleep, I had no clue.
What’s the name for rock-eaters, again?
He was still trying to solve the Fermi paradox—how, given all the universe’s time and space, there seemed to be no one out there. He’d held on to the question since our first night in the cabin, looking through our telescope at the Milky Way: Where was everybody?
“Lithotrophs.”
He smacked his forehead. Lithotrophs! Duh. So, say there’s a rocky planet full of lithotrophs, living in solid rock. You see the problem?
“Not yet.”
Dad, come on! Or maybe they live in liquid methane or whatever. They’re super-slow, almost frozen solid. Their days are like our centuries. What if their messages take too long for us to even know that they’re messages? Like maybe it takes fifty of our years for them to send two syllables.
Our whippoorwill started up again, far away. In my head, Chester, infinitely long-suffering, was still struggling with Yeats.
“It’s a great idea, Robbie.”
And maybe there’s a water world, where these super-smart, super-fast bird-fish are zooming around, trying to get our attention.
“But they’re sending too fast for us to understand.”
Exactly! We should try listening at different speeds.
“Your mother loves you, Robbie. You know that?” It was our little code, and he abided it. But it did nothing to calm his excitement.
At least tell the SETI listeners, okay?
“I will.”
His next words woke me again. A minute, three seconds, half an hour later: Who knew how long?
Remember how she used to say: “How rich are you, little boy?”
“I remember.”
He held up his hands to the moonlit mountain evidence. The wind-bent trees. The roar of the nearby river. The electrons tumbling down the staircase of their atoms in this singular atmosphere. His face, in the dark, struggled for accuracy. This rich. That’s how rich.
WHEN HE FINALLY LET ME SLEEP, I couldn’t. The two of us were doing fine, camping in the woods with a few cooked beans and a sketchbook. But the minute we returned to civilization, I’d be neck-deep in work and Robin would be back in a school he hated, surrounded by kids he couldn’t help spooking. Eden would be clear-cut again, back in Madison.
Everything about parenting terrified me, long before the day Alyssa burst into my office in Sterling Hall and shouted, “Ready or not, Professor—company’s coming!” I hugged her, to an ovation from my amused colleagues. But that was the last time I executed my paternal responsibilities with unambiguous success.