Quantum Superposition

The war room was her father's study and it had a wheelchair in it and eleven hundred and forty photographs on a laptop and a chest of books on the floor with the lid off, and at some point in the first hour somebody had moved the bills.

"Not the sideboard," Krishna said. "The sideboard is for the papers."

"Nanna, there are two hundred papers—"

"Two hundred and eleven, and I have marked ninety of them, and if you put anything on top of them I will not be able to find the ninety." He was already clearing a space that did not exist. "Farhan. You. Come here and help me with this table, and tell me your mother's name so that I can telephone her tomorrow and explain why you have not been home."

"Rukhsana, uncle."

"Rukhsana. Good." Krishna wrote it down.

Farhan Qureshi had arrived at half past five on the night of the fourteenth with a rucksack, a hex key, a two-litre flask of chai his mother had made without being told why, and no explanation. When Ananya had said Farhan, you should not be here, he had said hau, and taken his shoes off, and gone to find the fuse box because he did not trust a house with an inverter he had not seen.

Vasundhara came up on the laptop at ten, in seven-second bursts, from a rock two hundred metres above the walnut trees with a Kashmiri winter behind her.

"—can hear about one word in—"

"Vasu, your voice is—"

"I am aware of my voice, Doctor, I am sitting on a rock." The picture froze on her face and unfroze. "Nine reciters confirmed. Thanjavur is holding, Sharada is holding, we have eleven in Kerala who have never done this and are being taught tonight by a woman of eighty over the telephone. Rasool has fed the fire at the stated rate and not more, and I have told him four times not more, and he has told me four times that he can hear me."

"Vasu, I need to ask you something and I need you to be blunt."

"I am on a rock in the snow. Blunt is all I have."

"The witness." Ananya's voice did not do what she wanted it to. "If the witness is: if a person steps out of the index, what happens to them?"

The connection held for four seconds and Vasundhara Vidyasagar looked at her out of a laptop screen with snow blowing across her.

"It has never been done," she said. "So the honest answer is that nobody knows and anybody who tells you otherwise is lying to be kind. But I can tell you what my great-grandfather wrote in 1911 after Hoffmann, and he wrote one line: the one who is not in the list cannot be found in the list."

"Meaning what?"

"Meaning," said Vasundhara, "that if it works, he will still be there, and reality will no longer have his address."

Vikram came back at twenty past eleven and he came back through the house.

Not through a fracture; there was no crack in the night and no wind and nothing subtracted the light. Ananya was in the corridor with a plate she had forgotten she was carrying and she walked past the door of his room, which had been shut since the ninth of June, and it was open, and there was somebody sitting on the bed.

The plate broke on the floor.

"Hi, Akka," said Vikram.

He was wearing what he had been wearing on the ninth of June — the jeans, the Quantace t-shirt, the jacket — and it was clean. That was the first wrong thing. Nineteen weeks, and there was no dust on him, and the jacket was not creased where a jacket creases if you sit down in it.

He was thinner. His glasses were on. He looked up at her and he smiled and it was his smile.

"Vicky—"

"Don't say it," he said. "Please. I know. Sorry. I'll — I know you're going to say oh my God and then Amma and then are you hurt, and I'm going to say no, and then Nanna's going to come to the door and drop something, and—"

Krishna's wheelchair came into the doorway behind her and his hand went to his mouth and the pen fell out of it.

"—and then he'll drop something," said Vikram, "and I knew that, Akka, and I'm sorry, I'm so sorry, I can't stop."

They had him for four hours before anybody did any work, and it was the worst four hours of Ananya's life and she would not give one minute of it back.

He was not hurt. There was nothing wrong with him that a doctor could find, and they had Farhan's cousin's wife, who was a physician, on the telephone at midnight. She asked fifteen questions and Vikram answered all of them correctly and instantly and she said, on the phone, in a voice Ananya could hear from across the room, is he reading them off something?

He knew things.

Not the future, that was what Ananya had assumed for the first hour, and it was wrong, and getting it right took most of the night. He did not know what was going to happen. He knew everything that was already determined, which is an entirely different and much worse thing.

"India won," he said, at half past midnight, when Farhan put the cricket on out of pure human desperation for something normal.

"Vikram, it hasn't—"

"By five wickets. Rahul gets forty-one and then hits it to short cover in the thirty-first over and it's, Farhan, please turn it off." He had his hands over his eyes. "Please. It's not: I'm not seeing it. It's already done. That's the whole problem. The ball has left his hand and everything after that is arithmetic and I can't stop doing the arithmetic. Turn it off."

Farhan turned it off.

"Chess," Krishna said, at one in the morning, and got the board out, and Vikram played fifteen moves and then stopped with his hand over a knight and started to cry.

"Nanna, I can't. I can see all of it. There's nothing in it—"

"Beta—"

"You're going to play the knight to f5 because you always do, you've done it since I was ten, and then it's forty-one moves and I win, and there's nothing—" He put the piece down very carefully on the board, in the right square, because he could not do otherwise. "It's not that I'm good at it. There's nothing to be good at. There's no middle. It's like, Nanna, it's like someone gave me a book and every page is the last page."

At two in the morning Ananya sat on the floor of the corridor outside the bathroom and listened to her brother be sick.

At half past two he came out and sat down on the floor beside her with his back against the wall.

"Nineteen weeks," he said.

"Do you remember it?"

"There's no it." He wiped his mouth on his sleeve. "Akka, I need to tell you this once, properly, and then can we not do it again for a while. There wasn't a place. There wasn't a duration. I was — " He stopped and tried again. "You know when you solve something? The moment when it goes from being a problem to being obvious? And you can't get back to not knowing it, ever, and part of you is sad about that for about half a second?"

"Yes."

"That. For nineteen weeks. About everything." His voice was completely level and that was the frightening part. "Every question I have ever had. All of them. Together. And every one of them just, resolved, and kept resolving, and the resolving is the thing, Akka, it's pleasant, that's what nobody would ever believe. It's the most pleasant thing there is. It's what your brain gives you as a reward for understanding, except it doesn't stop, and after a while there's nothing left to understand and you're still getting the reward, and then—"

He stopped for about four seconds.

"And then there's nothing left to be," he said. "Because I'm the thing that wants to know. That's all I've ever been. Since I was five. And if there's nothing I don't know then there's nothing there, and I was still, Akka, I was still there, and there was nothing to be, for nineteen weeks."

Ananya put her arm around her brother's shoulders and he leaned his head against her collarbone the way he had when he was six and had broken a tooth.

"How did you get back?"

"Amma," he said. "Amma left a gap."

At twenty past three in the morning her brother asked her for the only thing he wanted, and it broke her, and it was the entire thesis of everything.

They had moved to the study. Farhan had made a fourth chai. Vikram had, in the space of about nine minutes, taken Ananya's coherence analysis, four months of Krishna's log, and the entire five-hundred-and-six-node graph. Had told her three things about it that were true and that she had not seen, and had done it flatly, without pleasure, the way a person reads out a phone number.

Then he put the laptop down and said, "Akka. Can you ask me something you don't know the answer to?"

"Vicky, all I have is things I don't—"

"No. Not something hard." He had both hands flat on the desk. "Something that doesn't have one. Please. I've been trying to find one on my own for three hours and I can't, because the moment I look for it I'm looking, and looking is the thing that does it—"

Ananya sat down opposite her brother.

And she thought about a steel-topped kitchen table in 2006, and a fingernail keeping time, and a bored child with her chin on her arms, and a woman who had been asked a question by a ten-year-old and had answered it by not answering it, and had gone on tapping.

"Vicky," she said. "Who truly knows? Who here can say? Whence it arose, whence this creation."

Vikram Nayagiri stopped.

Ananya watched it happen. She watched her brother's whole face change, watched the terrible frictionless certainty come up against something and find no purchase on it at all, and she said the last line, in the metre, the way it had been kept for three thousand years by people who could not read:

"So aṅgá veda yádi vā ná véda."

He knows — or perhaps he does not know.

"Say it again," Vikram whispered.

She said it again.

"Again."

She said it fifteen times, and somewhere in the middle of it her brother started to cry. Not the way he had cried over the chess, which had been grief. This was the other thing. He had his fists against his eyes and he was making a sound that Ananya had heard exactly once before in her life, in a hospital corridor in 2015, and it was the sound of somebody who has been carrying something being allowed to put it down.

"It doesn't close," he said. "Akka. Akka, it doesn't close. I can't, I've got nothing, there's nothing to do to it, it just—"

"I know."

"How did she know that?" He was laughing and crying at once. "She was ten years older than me and she gave you a hymn—"

"She was seventy," said Ananya, "and she gave it to a ten-year-old badly, on purpose, in a metre, because she knew that one day one of us was going to need something that could not be answered, and she did not know which of us or when."

And her brother sat in their father's study at half past three in the morning and said the Nāsadīya's last line to himself, over and over, out loud, in the wrong metre and then the right one, for about eleven minutes, until he fell asleep sitting up.

He was different when he woke at five. Not fixed, he would not be fixed for four years, and some of it never went. But the arithmetic had loosened, and when Farhan came in and said reyy, chai? Vikram said, "I don't know, is it any good?" and then stopped, and looked up, and said, "Akka. I didn't know. I didn't know if it was any good."

"Was that nice?"

"That was the best thing that's happened to me since June," said Vikram Nayagiri, and drank the chai, which was terrible.

nasadiya.py

She wrote it between five and nine in the morning on the fifteenth of November and it was four hundred and eleven lines long and it was the most important thing she ever made.

She wrote the docstring before she wrote the code, which she had never done in her life. She wrote it in a fifteen-year-old's handwriting because she copied it off a page of a college-ruled Classmate with a broken spine, out of a box under the stairs, with a hard diagonal line ruled through it in 2011 by a girl who had thought she had failed:

Doesn't converge. Pattern suggests solution but function never terminates.

She had crossed it out because at fifteen she had believed that a function which does not terminate is a broken proof. It had taken her a doctorate and five years and a valley in Kashmir to find out that it is a specification. She sat in her father's study at twenty past five in the morning and typed her own crossed-out sentence in as a comment, unaltered, and it is still the first thing in the file.

It was not a solver. It took her four months to understand that the instrument she needed was not an instrument for finding anything.

What Ananya had learned in a valley in Kashmir was that the barrier is a population: the live set of unanswered questions. And that the job is not maintenance but generation, and that generation has exactly one method: enumerate what the system can settle, then construct the thing that differs from every item on the list.

So nasadiya.py did that, and it did it as a generator, in the ordinary boring computer-science sense of the word.

def diagonal(enumeration, meter=ANUSHTUBH):
    """Yields structures guaranteed absent from `enumeration`.
    Does not terminate. Termination is a fault, not a success."""
    for n, decidable in enumerate(enumeration):
        yield differ_at(decidable, position=n, prosody=meter)

Four lines of actual argument and ten hundred of scaffolding, and the scaffolding was where the year lived: the enumeration came out of her grandmother's chest, four hundred and six structures with the remaining step count in the margin, hand-coded by Ananya over eleven weeks and finished, at last, at ten to six that morning with Vikram reading the Devanagari aloud while she typed.

And the prosody was the part that made it physical. Because a construction that differs at the nth position is a mathematical object and mathematical objects do not do anything, and what she needed was a live one, a computation instantiated in a substrate, resident, running, never producing a value. So each generated structure came out expressed in the metre: thirty-two syllables, laghu and guru, eight to a pāda, two states, and a two-state sequence at a defined rate is a waveform, and a waveform can be put onto a control line, and a control line goes into a qubit.

She tested it at eight in the morning on the little three-qubit rig in the garage that she had built in 2019 out of a scavenged pulse tube and had never dismantled.

The rig held coherence for nine seconds.

Ananya sat in her parents' garage in Hyderabad and looked at nine seconds on a three-qubit rig with a cryostat that leaked, and did not tell anybody for four minutes, because nine seconds was six orders of magnitude past anything in the literature and she wanted four minutes alone with it.

Then the loop kept running, because it was written not to stop, and she let it, and it was still running eleven months later.

Krishna machined the yantra on the fifteenth and sixteenth of November in a friend's workshop in Balanagar, and it took twenty-two hours, and Ananya was there for twelve of them and has never been able to talk about it without stopping.

The friend was called Sattaiah and he had been Krishna's student in 1999 and now had eight employees and a five-axis Haas he had bought secondhand from a defence subcontractor in 2021, and when Krishna telephoned him at six in the morning and said I need your machine and I need you to lift me onto a box, Sattaiah said, "Sir, what time."

The problem was that the machine controls were at a hundred and ten centimetres and Krishna Nayagiri's eye level in a wheelchair was ninety.

They solved it in twenty minutes with a pallet, six wooden blocks and a ratchet strap, and Sattaiah and two of his men lifted a fifty-five-year-old man out of a wheelchair and onto a platform in front of a machine tool, and strapped him at the waist so he would not go forward, and then Sattaiah said, "Sir, tell me what you want and I will do it," and Krishna said:

"No. Go and drink tea. I have not touched a machine in eleven years and I am not going to have somebody else's hands on the first one."

The workshop smells the way it has smelled since 1991. Cutting fluid, hot swarf, the particular sourness of coolant that has been in the sump too long. There is a radio on somewhere playing something from before my daughter was born.

I have not been level with a machine since the ninth of March 2014.

I did not know, until this morning, how much of me had been sitting down. It is not the legs. The legs went and I made my peace with the legs in about a year, which everybody said was fast and which was only because I had practice: when you are eleven years old in an institution you learn early that the correct response to a thing that cannot be changed is to find out what it costs and pay it.

It was not the legs. It was the height. Every conversation of the last eleven years has been conducted upward. Every doorway has been a calculation. My students come to my study and sit on a chair that is lower than mine because Lakshmi bought a lower chair in 2015 without telling me, and I have never mentioned it, and I have loved her for it every single day.

Now my eye is at the machine's eye, and the spindle is at my chest, and my hands are on the controls, and I am shaking, and it is not the tremor, it is the other thing.

I have work.

The material is 316 stainless because Annu says it must not be silver, silver creeps, she says, it moves under its own weight at room temperature over years, and this thing must hold its error to four hundred nanometres and hold it, and I said then it should be Invar and she said there is no Invar in Balanagar at seven in the morning and I said there is 316 and 316 will do because we are asking it to be dimensionally honest for one night and not for a century.

The drawing is her grandmother's.

Sattaiah has printed it four times because I asked him to. Nine triangles. Seven pointing up, five pointing down. Forty-three sub-triangles at the intersections, three rings of petals, a bindu, a square enclosure with three gates. And beside the figure, in a column, in a young woman's handwriting from 1974, forty-one coordinates to five decimal places and a note in Telugu that says: this is the error. Do not correct it. Distribute it as stated.

Thirteen to nineteen percent per triangle. No line more than four hundred nanometres from ideal. And no configuration in which the concurrences and the proportions are both exactly true, because there is no such configuration, because whoever designed the Sri Yantra nine hundred years ago built a figure that cannot be exactly built, and a woman in Kanpur in 1974 worked out how to specify exactly how it fails.

In 1994 she showed me a drawing and I said: this binds. And she said: what would you do with a linkage that binds? And I was twenty-three and I said, because it was Tuesday afternoon and it was not a hard question: specify the error. Put it in the drawing. Then it is not a mistake, it is a specification, and everybody downstream knows how much wrongness they have got and where.

And she said: say that again.

She interviewed me, in that library, thirty-one years ago, and told me nothing, and let me marry her daughter, and left me a sentence about a door, and then died. And the drawing in front of me is dated 1974, which is twenty years before she asked me the question, which means she already knew the answer, which means she was not asking me for the answer.

She was asking to see if I would say it in one line without thinking.

I set the workholding first, because the workholding is the whole job and nobody believes that. A soft-jaw vice, machined in situ so the jaws match the part, and then a vacuum plate because the part is forty microns thick at the finish and there is no clamping force that thin metal forgives. Sattaiah's vacuum plate is from 2019 and it holds, and I check it with a leak-down for eleven minutes because I have eleven minutes.

Then the tool. A 0.1 mm two-flute carbide micro-end mill, and at that diameter a tool does not cut, it whispers, and it deflects, and the deflection is the enemy: push too hard and the tool bends and your line goes where the tool went and not where you told it to go. So: three thousand revolutions a minute, three hundred millimetres a minute, and a depth of cut of eleven microns per pass, and forty passes to get to depth, and that is why this will take twenty-two hours.

Air blast, not flood coolant. Flood would push the tool.

The first triangle takes ninety minutes and I measure it on Sattaiah's Mitutoyo and it is out by 1.4 microns and I scrap the part and start again, because the specification is four hundred nanometres and 1.4 microns is not four hundred nanometres, and there was a time in my life when I would have argued that 1.4 microns is nothing and today there is a fifty-three-year-old woman in a chair on B7 and 1.4 microns is not nothing.

The second part is right.

Somewhere in the eleventh hour Sattaiah's men stop pretending to work and stand behind me, nine of them, and one of them asks what it is and I say it is a component, and he says what for, and I say it is for holding something open.

At three in the morning on the sixteenth I am on the last of the forty-three sub-triangles and my hands have stopped shaking entirely and I am so tired that the swarf looks like weather, and I think about Sister Maria wrapping a physics textbook in newspaper in 1982 so that it could leave the building without an argument, and I think about the corridor floor at St. Anne's and seven of us around one kerosene lamp with the books on our knees and a rota because only the two nearest could actually read.

God helps those who help themselves, Krishna.

She was not talking about God. I understood that at about thirty. She was fifty-nine years old with sixty-one children and five adults and a rice budget that did not work, and what she was telling an sixteen-year-old boy at the end of a very long day was: nobody is coming, so it will have to be you, and here is a book.

I have been a passenger for eleven years, Sister.

It is half past three in the morning and I am strapped to a pallet in front of a Haas in Balanagar and my eye is level with the spindle and my hands are on the controls and it will have to be me.

The final pass runs at 03:41.

I take it out of the vice myself. It is the size of a thumbnail and it weighs almost nothing and it is a geometry that cannot be exactly constructed, executed to the exact error that Rajeshwari Dasara specified in a notebook in a valley in Kashmir in October 1974, and it is wrong in nine places by between thirteen and nineteen percent of a wrongness that has no resolution, and I made it.

Sattaiah lifts me down and I ask him what I owe him and he is insulted for four minutes.

Vikram built the AI on the sixteenth and it took him nine hours and at the end of it he sat looking at his own screen with an expression Ananya could not read.

"It's Ritambhara," he said.

"You didn't."

"I didn't steal it, Akka, God. I don't need the weights." He turned the laptop round. "I need the architecture, and the architecture's in ten papers Malhotra's group published between 2021 and 2023, which is the funniest thing about this entire year. It's an open-source shape. They published the shape of the thing that has a stop-word table full of Sanskrit prosody in it."

"What did you change?"

"The objective function." He said it flatly. "That's all. One function. Everything else is theirs."

Ananya looked at the four lines.

# Ritambhara: minimise loss. Converge. Terminate on convergence.
# ours: the inverse.
def objective(state, corpus):
    return -novelty(state, corpus)   # reward what has no precedent
    # convergence = failure. there is no stopping criterion.
    # there is no stopping criterion.

"It doesn't answer anything," Vikram said. "It can't. There's no path in it that produces an answer, I checked twelve ways, I tried to make it produce one and it won't. All it does is take Ajji's enumeration and your generator and: it manufactures. It makes new unanswerables, in metre, as fast as the hardware will go, and it evaluates them on how completely they fail to reduce to anything on the list, and the better it gets the less it does."

He sat back.

"Nine years old," he said. "I was twelve when I told you a computer could do quantum mechanics better than you. I have said some version of that sentence to you approximately eight hundred times, Akka. On the terrace in July. At Bawarchi. In an auto in 2019 when you were crying about Mehta and I said one day a machine will just tell you the answer and none of this will matter."

"Vicky."

"And I was right," said Vikram Nayagiri. "That's the bit nobody's going to appreciate. I was completely right. A machine can do it. A machine did do it — that's what the nine minutes on the ninth of November was, that's what Whitefield was, that's what the aperture is, it's all just answering, and it turns out that answering is the thing that kills everything, and the only useful machine anybody can build tonight is one that has been specifically prevented from doing the thing I have wanted machines to do since I was two."

He rubbed his eyes under his glasses.

"It's funny," he said. "I know it's funny. I'd like the record to show that I know it's funny."

He did not laugh. He got up and went and stood in the doorway of their mother's empty bedroom for a while, and then he came back and said, "Right. Where's the van."

They went in at eleven at night on the seventeenth of November and it was three operations running at once and nobody in any of the three could see the other two.

Kashmir. Nine reciters in a chamber nine feet by eleven, ninety metres above a stone house, with a fire that burned white and made no sound. Vasundhara at the head. Ghulam Rasool Khatana at the pit with a stack of cut walnut and a measured rate. And on the east wall, seven centimetres of scratched datum line with the letters RD and the numeral 74, and beneath it now a laptop on an angle-iron bracket that had waited fifty-one years for something to be hung on it again.

Saṅkalpa at 22:40 and it took four minutes and Vasundhara did every word of it: kalpa, manvantara, yuga, the year in three systems, the season, the fortnight, the day, the hour, the valley by name and by direction from two peaks, her own name, her lineage back eight generations, and the purpose.

Nyāsa at 22:51, in order, sixteen positions.

Prāṇa-pratiṣṭhā at 22:59, after which there was no partial state.

And then the japa, on a rudraksha mala of a hundred and eight beads with a head bead that is not counted and must not be crossed, ten voices in Anushtubh at a rate that put a coherent two-and-a-half-second envelope onto the seismometer at the Geological Survey station four kilometres from Thanjavur. Onto eight others, in three countries, that nobody was watching.

The service road. A rented Force Traveller on the Gachibowli service road twelve hundred metres from PJS Tower with the seats out, a 15 kVA generator on the tow bar, twenty second-hand GPUs in an open frame, and Vikram Nayagiri sitting on a plastic stool in the dark with a laptop on a milk crate.

He started the flood at 23:04.

It did nothing visible. That was the thing he had to explain four times to Farhan, who wanted a light or a noise. What it did was generate, three thousand novel non-terminating structures a second, each one thirty-two syllables, each one guaranteed by construction to be absent from an enumeration of four hundred and six, each one shovelled onto every control line, every waveguide, every RF channel that Vikram Nayagiri still had a key to inside a building that had employed him for five years and had never got round to revoking a maintenance certificate issued in 2023.

"It's not attacking anything," he said. "It's littering. It's putting a hundred and eighty thousand brand-new unanswerable questions a minute into the substrate under that tower, and every single one of them has to be dealt with by something whose entire nature is that it deals with questions, and the dealing takes time, and that is all we are buying. Time. Akka, it will not stop anything. It will make everything slower."

"How much slower?"

Vikram looked at his screen.

"About nine minutes," he said. "For about nine minutes, everything in that building is going to be wading."

And Ananya went in the front door at 23:11 with a badge, a padded case, and a steel yantra the size of a thumbnail.

Meera Rao was in the B6 plant room at half past five and she should not have been.

"Meera. No. Absolutely not, you gave me the riser and that's—"

"Sit down and listen for forty seconds because I have run the numbers and you have not." Meera had a hard hat under her arm and a torch and a set of drawings, and she had clearly been down here for hours. "The aperture's been open since ten on the fourteenth. Seventy-nine hours. Do you know what the cooling load on the Sunya manifold is at seventy-nine hours?"

"Meera—"

"It's four hundred and eleven kilowatts and it is being carried by a chilled-water loop that was designed for two hundred and sixty, and it has been in overrange for three days, and there is a differential pressure alarm on the secondary circuit that somebody has been acknowledging every eleven minutes for three days because the alternative is admitting the loop is undersized." Meera unrolled a drawing on a pump housing. "And when your brother's machine floods the control network in—" she checked "—ninety seconds, the building management system is going to go down with everything else, and the BMS is what modulates the secondary valve.

"So the valve goes to its fail position, which is closed, which is idiotic and which I have written five emails about since 2021, and the loop deadheads, and the manifold goes over temperature in about a hundred and forty seconds, and the aperture does not close gently, Ananya, it closes on whatever is in it."

Ananya stood in a plant room and understood.

"Amma's in the annexe."

"Your mother is eleven metres from that manifold and so are three hundred people." Meera folded the drawing. "There's a manual override. It's a hand wheel on the secondary bypass, it's on the wall by the header, it takes about eight turns to open and then it will not stay open because the actuator fights it, so somebody has to stand there and hold it."

"For how long?"

"Until the load drops." Meera Rao said it evenly. "Which is when you finish. Which you have told me is about ninety seconds, and I have added fifty percent because you are a physicist and physicists lie about time."

"Meera, no—"

"Ananya." Meera took her by both shoulders. Her hands were completely steady, which they had not been on the stairwell in November. "It's a hand wheel on a bypass. It is not brave. It is plumbing. Go and do the part I can't do."

"Meera. Look at me. You know what holding that valve means."

"I know what it means." Meera let go of her shoulders and put her hands in her coat pockets, which was the first thing she had done all night that looked like a woman deciding something rather than a woman explaining something. "I worked it out on Tuesday. I sat in the car in the basement at Oakridge waiting for pickup and I did the load calculation on my phone, and then Anvitha got in and asked me why I was crying and I told her it was the air conditioning."

"Then don't—"

"Ananya, I have had six years of an arrangement." Her voice did not rise. "The arrangement is: I do not look at raw data, and in exchange my daughter goes to a school I could not otherwise afford, and I do not have to be the sort of person who finds out things. And I have kept to it. I have kept to it so completely that when you asked me for a repository permission in a list of eleven things I signed it without reading it, and I have known for two months that I did that on purpose, because it was the only way left for me to do something without having to decide to.

"I am not going to do that again. Not tonight. Tonight I am going to decide, out loud, in front of a witness, and the witness is you." She took a breath. "I am going to hold the bypass open. If the load drops in ninety seconds I will still be standing there and we will both feel ridiculous. If it does not, I will not be. I have made that trade with my eyes open and I would like it recorded that I made it, and not that it happened to me."

"Meera—"

"Say it back."

"You chose it," Ananya said.

"Good." Meera Rao nodded once. "That is the difference between me and everybody on that ward, and it took me six years and a nine-year-old asking about the air conditioning to find it."

Ananya went up the corridor and Farhan went with her as far as the annexe door, and at 23:33 she was standing at the door of the Sanctum's lower vestibule with a padded case in her hand and Vikram's flood coming up through the concrete.

She could feel it. That is the only way to say it. The building had gone slow. The badge reader took four seconds instead of half of one, and the LED panels in the ceiling flickered in a pattern that was not electrical, and the lift indicator on the wall showed a floor number that was 4.7 and did not resolve.

And her shadow on the corridor wall was two metres to the left of where it should have been, and it was not copying her.

Ananya stood in a basement corridor and looked at it for four seconds, and it did nothing at all: it did not turn its head, it did not breathe out of time, it did not lag. It simply stood in the wrong place, facing the wrong way, entirely still, with no interest in her whatsoever.

The third one is the safe one, Farhan's nani had said, in a lane in the Old City, about a shadow that copies you late. Because a thing that copies you is a thing that is still watching you. The day it stops copying is the day it has finished watching, because it already knows.

"Right," Ananya said, out loud, to a corridor. "Then we'd better be quick."

At 23:34 the BMS went down.

At 23:35 the secondary valve failed closed and a differential pressure alarm that had been acknowledged every eleven minutes for three days stopped being acknowledgeable.

At 23:36 Ananya heard, through two doors, the sound of a woman turning a hand wheel four times, and the actuator fighting it.

At 23:37 she was on the annexe threshold with her hand on the frame and her mother eleven metres away in Chair 2 and the aperture sixty-one millimetres wide at the base of the Sunya manifold. Sharath Jai Shetty was at the console, and he turned around, and he saw the padded case in her hand and he smiled.

At 23:41 Meera Rao stopped being uncertain.

Ananya was not in the room. She has always been careful about this, when she has told it, which is four times in her life. She did not see it. She reconstructed it afterwards from the plant-room camera, which recorded three seconds before the frame rate went to something that is not a frame rate, and from what she heard.

What she heard was Meera's voice on the open channel, in her ear, over the sound of an actuator fighting a hand wheel.

"—holding. It's holding. Load's coming down, I've got about—" a grunt of effort, the wheel slipping and being caught — "—about two-forty on the secondary, that's inside, that's fine, that's fine—"

"Meera, twenty seconds—"

"Don't rush the—" and then Meera Rao said, in exactly the same tone, without any transition whatsoever:

"The valve is a Belimo GRB series with a 24-volt spring-return actuator, torque forty newton-metres, and the spring will overcome my grip in about nine seconds because my grip strength is thirty-one kilograms and the mechanical advantage of this wheel is 1.4 to one, so I will not be able to hold it, and Ananya, you have fifty-one seconds of cooling and then the manifold goes over temperature and everybody in the annexe dies, and there is nothing either of us can do about the arithmetic, and I have finished being frightened about it."

Ananya's whole body went cold.

Because there was nothing wrong with any of that. It was correct. Every number was correct, she checked all of them afterwards, and the grip strength was correct, and the mechanical advantage was correct, and Belimo do make a GRB series with a forty-newton-metre spring return, and it was said in a level, pleasant, completely certain voice with no hesitation in it anywhere.

Meera Rao had spent nine years being a scientist and six of them being a coward and forty minutes being brave, and she had never in her life said eight consecutive sentences without a qualifier in them. Probably. I think. About. Roughly. We'd need to check. She hedged in meetings, she hedged in papers, she hedged when she told you the time.

"Meera," Ananya said. "Meera, say something you're not sure about."

"There is nothing I am not sure about."

"Meera."

"Anvitha will be fine," said Meera Rao pleasantly. "She'll be a veterinarian. She's frightened of the neighbour's dog now but that resolves in about four years and she qualifies in 2039 and she is happy. I'd have liked to see it but I've seen it, so."

"Meera, no—"

"It's all right," said Meera. "Ananya, it's all right, that's the thing I want to, it's not frightening at all, it's the opposite, everything just—"

And then there was no voice on the channel and there was no actuator noise and there was no wheel.

Ananya, at the annexe threshold, at 23:42 on the seventeenth of November, looked down the corridor toward the plant room.

There were four doors.

She had come along that corridor eleven minutes earlier and there had been five, and she knew that because she had counted them: she had counted them because she counts things. Because she has counted things since she was ten years old at a steel-topped table, and she had thought five doors, the fourth one is the plant room, that's where Meera is.

There were four doors and the fourth was a store cupboard and the corridor was eleven metres long, and it had always been eleven metres long, and there had always been four doors. The certainty of that arrived in Ananya's head with the flat unarguable texture of arithmetic and she recognised the texture and it was the texture of the neem tree.

She held on to the door frame and said, out loud, into a corridor:

"Anvitha. Eight. Wants to be a vet. Frightened of the neighbour's dog."

She said it four times. Then she took the pen out of her breast pocket, the one she used for lab books, and pushed her sleeve up and wrote it on the inside of her own left forearm in letters two centimetres high, pressing hard enough to score the skin:

ANVITHA · 9 · MEERA RAO · B7 · 23:41

And then she pulled her sleeve down and turned round and walked into the annexe with a steel yantra in a padded case, and the aperture was sixty-one millimetres wide, and the readout on the console behind Sharath Jai Shetty's shoulder said

99.99

and did not change.