“Imagine Chloe is in a steel chamber.”

I closed my eyes and nodded, imagining this terrible thing happening to our pudgy pet.

“Also inside the steel chamber is a device which contains a trace of radioactive material,” you continued. “There is so little of the material that in the course of an hour there is an equal probability that one of its atoms will decay as will not. Are you with me so far?”

I nodded.

“If one of the atoms does decay, the device will trigger a hammer that will smash a small flask of hydrocyanic acid inside the steel chamber, which will kill Chloe. Sadly.”

I opened my eyes and looked at our cat perched on the back of the chair in the living room.

“But if no atoms decay then Chloe will be fine. Well, she probably wouldn’t like being in a steel box, but she will survive. According to quantum physics both possibilities remain equally in play until Chloe’s body is observed. Until someone opens the steel chamber and looks inside. It’s the moment of observation which pins Chloe’s body to a fixed, perceived reality: dead or alive.”

“That doesn’t make sense,” I said, crossing the room to pet our cat, who seemed altogether unperturbed by the fate of her hypothetical self.

You nodded in agreement. “Quantum physics doesn’t seem to make a lot of sense. But we know through math that it’s true.”

Schrödinger also thought this alive-and-dead cat was ridiculous. He reasoned there was no way Einstein’s theory of quantum physics could apply to people and things in everyday life. If the chamber was lifted and the cat was found to be alive, it would have an unbroken memory of being alive. And it would certainly seem consistent with our perception of reality that we do not exist in multiple states in the same instant. Schrödinger’s thought experiment also raised the question: When exactly did a quantum superposition collapse into becoming one reality or another? And did the cat itself not qualify as an observer of the situation, or did its existence in a single state require an external observer? Einstein was chastened by Schrödinger’s provocations and wrote him a letter in 1950 basically saying: “Touché.”

“Nobody really doubts that the presence or absence of the cat is something independent of the act of observation,” he admitted, later adding: “Do you really believe the moon exists only when you look at it?”