The proof had taken eleven years. It was built on a formalism she had begun developing in her early thirties, working from the foundations laid by the participatory universe interpretations and the decoherence literature, and it addressed a question that had been considered more philosophical than mathematical: whether the universe's persistence was conditional on being observed, or whether observation was merely a way of accessing a reality that would exist regardless. What she had shown, through a chain of argument that had required three major published papers to establish the necessary foundations, was that the conditional version was correct, and that "observation" in the relevant sense was broader than anyone had assumed. It included biological sensory systems. It included unconscious neural processing. It included, at very fine resolutions, processes in single-celled organisms. Eight billion humans, plus all complex life, plus a significant fraction of simpler life, constituted an observational apparatus so redundant that any gap in conscious attention was covered many times over.
The world was not in danger. That had been her first concern, years ago, and she had spent considerable time confirming that the redundancy made danger essentially impossible. If every human on Earth fell asleep simultaneously, the remaining biological observers would sustain the system. Even that scenario was physiologically implausible. Someone was always awake.
So the proof changed nothing, practically. She had known this before she finished it. The philosophical implications were substantial, but practical life was unchanged: the sun would rise, objects would persist, the laws of physics would continue to operate as they always had. The difference was only this: it was now formally true that everyone who had ever been alive had been, without knowing it, participating in the maintenance of the world. Every act of perception was also an act of sustenance.
She had verified the final step at eleven-seventeen. She had closed the laptop. She had stood up and walked to the window.
The street below was an ordinary street at midnight. A car passed. A light was on in the apartment across the way. The city made its usual sounds. None of it looked different. She had known it would not look different, and she had stood here for an hour anyway, looking at it.
There were stars visible above the building across the street, three or four of them through the city haze. She looked at them for a while. They had been there before she was born and would be there after she died, sustained by the looking of billions of people who had no idea that was what they were doing.
She did not go to bed. She stood at the window. There were stars to observe.