So. Three billion lightning strikes, Leslie said, slapping her thigh.

I liked Leslie. Where would the world be without A-type women slapping their thighs, keeping things on track?

Howard ran his index finger along his brow. Yes, so I was just saying—three billion lightning strikes a year, all over the world. A hundred every single second. That builds up a huge electromagnetic charge in the atmosphere. And this atmospheric charge resonates. And by resonates, I mean that it creates an actual sound wave. A very, very, very low hum at a frequency of 7.83 hertz.

You’re saying lightning is causing the atmosphere to hum? Seema asked.

Essentially, yes.

She lifted her feet off the ground, to sit cross-legged on the couch. And this is, like, accepted science? she asked.

Howard laughed. Yes, absolutely.

Well you never know. There’s a lot of bullshit out there.

Okay, I liked Seema too.

It’s called the Schumann Resonance, Howard said. We’ve known about it since the early fifties.

And it’s just, like, humming all the time, or—?

Exactly, so—Howard extended his arm towards Seema to apologize for cutting her off—you have these constant global electromagnetic resonances generated by lightning strikes in the cavity between the Earth’s surface and the ionosphere. Have you ever blown across the mouth of a bottle? he asked, addressing the question to Seema.

Uh, yup.

So just as the space inside a bottle has a specific resonant frequency, which you can hear when you blow across it, lightning, in the Earth’s case, is like the breath over the bottle. And the Earth’s resonant frequency is 7.83 hertz.

Tom raised his hand—I’m sorry, I know I came late to the conversation, but what the heck are we talking about here? Are you suggesting this is the sound we’re hearing?

Well I suppose that’s the controversial bit.

Tom frowned. Uh-huh.

Anything much below twenty hertz usually just drops off for humans, Howard said. I glanced at Kyle, but he didn’t turn my way. Below that range, we mostly just feel sound waves as a kind of physical pressure, Howard continued. Some mammals like whales can hear as low as seven hertz, but for humans to hear 7.83 hertz is—

Impossible, Tom said.

Most would say so, yes, Howard said, but there are some folks, myself included, who suggest it’s not. Just—exceedingly rare.

So hold on. Tom reached out into the middle of the circle like he was stopping traffic. This, this thing—and I’m sorry if I missed this—but is this something you read about in an article?

I was the dean of Virginia Tech’s Department of Geosciences for eighteen years, Howard said. I’ve published many articles about this.

This resonance?

Yes.

Oh wow, Emily murmured.

Howard’s a famous scientist, Leslie said, without irony.

Howard chuckled. Well I wouldn’t go that far but I—