He continued: “So you drop this person, and the gravity pulls on her, and you watch her fall, and like I said, it all seems pretty normal, until she gets close to that event horizon.”

“And then what?”

“Then she’s reached a point where space-time is curved so deeply by the black hole’s gravity that time goes wonky. From our point of view, it looks like she’s slowing down. Slowing and slowing and slowing, and just before she reaches that point of no return, she stops. She freezes, floating just outside the event horizon. We could sit there forever, but we’d never see her actually reach the black hole.”

“She stops?” I repeated.

“She does and she doesn’t,” Mark said, obviously delighted. “Out here, in our experience of time, we’d see her stop. But to her, everything seems normal: She keeps falling at the same speed and crosses the horizon. She enters the black hole and she either gets spaghettified—that’s when you get pulled into a string of atoms by the pressure of gravity—or she falls right into it and experiences something we can’t even begin to imagine! She’s both beyond the event horizon, inside the black hole, and she’s outside of it!”

“No one can be in two places at once.”

“But in a black hole, gravity’s so strong that all of space-time is infinitely curved,” he said. “For all intents and purposes, it’s a hole in space-time, where the laws of physics break down. Time inside a black hole isn’t like time out here. Right?”

“Pretty much,” Mom confirmed, smiling. “There’s a theory that if you did fall into a black hole, that because of the time dilation, you’d see everything that had ever fallen into it or ever would fall into it, all at once. All these pieces of our universe’s history that we’ve already lost—every cosmic body we ever will lose, and all the events that happened there—all occurring at the same time.”

“And then there are wormholes,” Mark chimed in. “Tunnels through space and time. If you fell into a black hole, you might travel through it and get spit out by a white hole on the other end. You could see everything that had ever fallen or will ever fall through—whole histories of planets and moons and stars, all playing out at once—and then get popped back to some other point in space-time before those things even fell in! Of course, wormholes are still just a theory, but black holes started out as a theory too!”

“Because of amazing math?” Arthur grumbled from the next room, where he was hunched over something at the coffee table.

“Sort of,” Mark answered. “The point is, nothing in our universe, even the stuff that’s supposedly deleted from time and space, is ever really lost. It’s just hidden from our sight.”

He smiled at me. “There are things about black holes that break all the rules—or expand them in a way we don’t understand yet. As if the universe wants to exist so badly it makes loopholes in its own rules. I find it comforting, like this is all meant to be somehow, and nothing can take any of it away. Like everything is forever.”

Mom smiled at him across the wasteland of greasy paper plates and crumpled napkins. “One of these days, I’m shipping your butt off to space camp, kid.”

Arthur jumped up and came into the kitchen carrying a piece of paper and slid it onto the table. “Look,” he said. “I drew Batman punching Superman.”

“Cool!” I said, but Mom eyed it with a suspicious smile.

“Isn’t that the cover on one of your comics?”

“Batman Versus Superman,” he said.

“Then you traced it?” Mom asked.

Arthur’s face reddened. “No, I drew it.”

“Well, you copied it, buddy,” Mom said. “Maybe you should try making up your own characters? I’m sure you’ve got all kinds of ideas in that noggin.”

Arthur picked up the drawing and stared at it.

“Can I see?” I reached for it, but he jerked it away.

“You’ll get grease all over it.”

“I will not!”

“You ruined my controller by playing with it while you were eating popcorn,” he said. “You always mess up my stuff, and Mom lets you because you’re a small, dumb baby!”

“Arthur!” Mom said. “Apologize to your sister.”

Tears and shame rushed to my face. Just then Dad came through the back door, drenched in sweat and smelling like cut grass. He leaned over Arthur’s shoulder as he was opening a bottle of beer. “What ya got there, Arto? Did you draw that?” He bent to kiss Mom on the cheek, and she writhed away from his sweaty face. “Mower’s out of gas,” he said, settling back against the fridge.

“I thought you just filled it,” Mom said.

“There must be a leak.”

Arthur took his drawing back into the other room, and Mom and Dad fell into their conversation about the lawn mower, and the moment moved on, but I still felt small and incapable and embarrassed.

“Psst!” Mark hissed across the table. When I looked up, he was pulling the nautilus shell out from under his BLACK HOLES DON’T SUCK T-shirt. He’d fixed it to a chain and was wearing it as a necklace.

He tapped the center point of the shell. “Remember, Fran, it’s not the size of something that matters in this galaxy. It’s the gravity of a thing, how much it pulls on things and where it takes them. You’ve got gravity out the wazoo.”