Prologue

The measurement was the thing that broke him, and it took twenty-four years.

He had gone into the chamber to copy an inscription. That was all. Professor William Blackwood of Trinity College had a lantern, a folio of India paper, a soft pencil and a commission from the Asiatic Society to record whatever was carved on the north wall of a shrine above the Sindh valley that the district officer's report described as of no great antiquity, locally venerated.

He copied it on the fourteenth of October, 1899, and it took him forty minutes, and he was pleased with the copy.

He measured it on the fifteenth, because he measured everything.

The lantern threw his shadow up the wall beside the carving and the carving did not move. He wants that understood, in the journals, in the four different hands his writing became over the next two decades: the carving did not move. He set his rule against the third character and read off the width, and wrote it down, and set the rule against it again and read off a different width, and the difference was not a difference his hand could make.

He measured it eleven times. The rule was brass. The rule did not change.

"Acharya," he said. "This mark. Is it the same mark it was yesterday?"

Acharya Vidyasagar was sitting on the step with his beads and did not get up. "It is the same mark it has always been."

"That is not what I asked you."

"No," the old man agreed.

Blackwood put his palm flat against the stone, which he had done a hundred times in a hundred temples, and which was how he learned that the cold of stone tells you the thickness of the wall behind it. The stone was cold and rough and completely still. Everything his hand told him was ordinary.

Everything his eye told him was that the second character had a serif on it now, and that this made the sequence consistent, and that it had not been consistent four seconds ago.

"They are describing superposition," he said, later, in English, to nobody, because he had no other word for it and would not have one for twenty-eight years.

"They were not built, Professor." The beads had stopped. "They were contained. What you read as mathematics, we bind with mantras."

"Bind."

"A truth was written once. So complete that it would have ended the need for all questions." The old man said it the way a man reads out a river level. "Our ancestors broke it across a thousand temples and bound each piece, because a proof that answers everything removes the reason for anything to exist."

"And the men who tried to finish it?"

"They became simple," said Acharya Vidyasagar. "Not mad. I want you to hear the difference, because you will remember this wrongly otherwise, and you are the sort of man who writes things down. They were not mad. They answered every question anybody put to them, correctly, instantly, and identically, for as long as they lived. My grandfather's brother was one of them. He was the kindest man in this valley for thirty-one years and there was nothing behind his eyes at all."

The temple is still there. The fire has not gone out, and the arrangements by which it has not gone out are more interesting than the fire.

Blackwood went home to Cambridge, read a paper to the Society that was politely received, and did not publish the measurements. He kept twelve journals over twenty-four years, and the equation appears in all of them, in his own hand, on pages he had left blank. In 1904 he wrote that he had begun to suspect he was not the one dreaming. In 1923, on the morning of the day he died, he wrote out the correct statement of a theorem that would not be proved by anyone else for thirteen years, and noted underneath, in a hand that was not his:

Not the last one. Ask again in a hundred years.

A hundred years and some months later, in a laboratory in Hyderabad, a woman who has never heard of William Blackwood holds a single caesium atom in two places at once for three and a half seconds, and writes the time down, and telephones her brother.

Every equation is a window. Nobody has ever thought to ask which side of it we are on.