I sank down my seat, phone in hand. The handsfree attachment was in my ear.

"Negative temperature? What, Celsius scale?"

"Kelvin."

"That's not possible, you know matter can't cross absolute zero. Do the laws of thermodynamics mean anything to you?"

"Hey, hey hey. Here. Benj, listen. Lemme try to convince you. What's the definition of temperature?"

"Change in energy with respect to entropy — or something. Thermo class was years ago, I can barely remember anything — but what of it? Having a negative temperature would imply a greater than infinite entropy that isn't—"

"Energy, it... it rolls over."

Silence. I wondered what he meant by 'rolling over.' The speaker crackles as I sensed his frustration. I probably sounded really smug, as well. What could I do? It had been years since I last opened a textbook on thermodynamics. I never ended up in a career in science anyway; I couldnt chain myself to a desk and pussy up to a superior, either.

"I'll spare you the details," he said, breaking the silence. "I know you've been out of the academe for a while. But, uhh, wait. Here, do you know the kill screen, in Pac-Man?"

"Vaguely?"

"The counter for the levels of Pac-Man are stored in just one byte, meaning that it has a limit to the unique numbers it can represent; 255 numbers in this case. When you kick into 256, you just add one to the binary representation of 255. But without another leading bit to increase your number of representations, it would just roll over and effectively become zero, messing up a lot of stuff."

He really loved the arcades in his youth.

"Well guess what," he continued. "The same thing happens for entropy and energy, somehow. Adding infinite entropy lowers the temperature so much, but at this critical value, it peaks! It peaks, Benj!"

The enthusiasm was clear in his voice.

"No, no, that's really not possible. It's Physics."

"Wait, listen to me! you've gotta listen, gotta give it time. The temperature readings I got were high, almost infinite, when I should be already at a negative value! I mean, think of the implications! I'm excited, I simply can't keep it, inside no, I can't keep it in... I've already written the editors of Nature for my breakthrough. This is going to be big, I'll be in the papers again!"

"Dad-dad-dad. Dad. Get a hold of yourself. What are you talking about?"

"The implications! Think! Pac-Man!"

"What about Pac-Man?"

"Our universe is like Pac-Man. It's a machine! It only makes sense: even speed is capped by c, the speed of light. That's a constraint in representation, only in computers!"

"Dad, I'm going to have —"

"We are a simulation —"

"Dad, you're going to have to — you're speaking nonsense."

I was shouting. Why did I have to shout? It didn't make the situation any better.

"Listen to me, dad," I said, in a calmer tone, "and I'm sorry I have to bring it up like this. I'm not Benj. Your colleague, Benjamin, he died five years ago. I'm your son, Ian. You've been out of the lab for years. There were no experiments, it's all in your head. None of what you're saying is possible, and — I don't even know if you understand me, if you're listening to me now, with your condition, and I know it's hard..."

I knew putting the truth in the face of someone with dementia could mess them up a bit. Most care facilities deck out their rooms and halls in the familiar livery of public areas, cafes, and parks, just to give them a sense of familiarity and a venue to make the most of their delusion.

"I've been recording this call," I reveal, "For doctor Sherman, so he can help in your next checkup. I'll be at the appointment."

He was dead silent. There was always something off in that silence.

"I'll see you next week, dad. Me and Nessa, we'll be with you, okay?"

"I'm sorry I was such a bother, son."

"It's alright, dad. It was good you knew the truth. Well, I'll see —"

"Thank you for always checking up on me. Always know that I'm proud of you."

A flowing sensation came over me, warm yet chilling, even now. That was the first time he had called me son in years.

"I love you, son."

click

Fingers grace my shoulder as the earpiece flicks out, freeing one more of my senses to the outside world. It was Nessa.

"Ian, it's been two months."

"I know."

It's only now that I realize the area below my shirt collar was streaked with tears. I close the media player on my phone and slump back down onto the couch. She sits down beside me and takes my hand: she knew what I had been listening to. It's all I've listened to nearly every night.

"You know, dad probably died still believing we were in a simulation."

"Yeah," She said, softly.

"It's a little comforting now that at least he knows the truth."