Julian date 2459536, Friday, 22:00.
Two boxes on the screen. The A4 behind Ursula had been changed again; in its upper right corner a handwritten date—yesterday's.
Zhou Yan spoke first: what I want to ask is when it began.
Ursula said: that's a better question. Better than "where is it."
She said: we hold only the present point. 0.31.
So you go looking for history.
How.
Ursula said: three rulers. First, historical supernovae. Second, cosmic rays in tree rings. Third, photographic plates. All three are dirty. All three can measure. Measure all three first, then come back and talk.
She said: how do I compare the three.
Don't. Ursula said: these three numbers do not convert into one another. Calibrate them against each other and you're finished. You only look at where each one breaks, and where each one bends.
She said: bends.
Bends, Ursula said. And breaks. Breaks are more honest than bends.
Hu Yisu was doing the first ruler.
He worked through the public catalogs of historical guest stars, four record-keeping traditions—Chinese, Japanese, Korean, Arab. Eight entries matched to remnants: 185, 386, 393, 1006, 1054, 1181, 1572, 1604.
For 1006, the History of Song has: third year of Jingde, fourth month, day wuyin—the star of Zhou Bo appeared, south of the Di mansion, one degree west of the Cavalry Officer.
For 1054, the Song Huiyao has: first year of Zhihe, fifth month, day jichou—a guest star appeared to the southeast of Tianguan, a few cun at most. And after that, one more line: after a year and somewhat, it faded. What that star left behind is called, today, the Crab Nebula.
The one from 1181 was recorded once by China and once by Japan, the two records two months apart; which remnant it matches is disputed to this day.
After 1604 down to today, four hundred sixteen years: naked-eye supernovae inside the galaxy, zero.
Hu Yisu said: that sentence I want to say once by itself. In 1604 people used their eyes. What our telescopes see now goes a dozen-odd magnitudes deeper than the eye, whole-sky surveys once a night, tens of millions of entries a pass. Four hundred sixteen years. Not once.
She said: what about Cas A.
He said: around 1680, give or take. That year's records don't contain it.
She said: not found isn't the same as not there.
He said: I know. That's why I left it out.
She asked: what are eight points good for.
Hu Yisu said: eight numbers, four bins, two to a bin—write whatever slope you like.
She said: then we write nothing.
And after she said it she thought again: copy out the intervals.
He copied: 185 to 386, 201 years; 386 to 393, 7; 393 to 1006, 613; 1006 to 1054, 48; 1054 to 1181, 127; 1181 to 1572, 391; 1572 to 1604, 32; 1604 to today, 416, and still growing.
She circled the last line.
The bit with Tianguan she checked against today's catalogs. Near the position of the 1054 guest star, one of her 1,042: number 0887, 740 light-years out, seven edges. Seven is middling-low. She wrote on paper: 0887, 7, near 1054, no meaning.
When it was written she traced "no meaning" a second time.
Hu Yisu wanted to put it in the memo.
She said: it doesn't go in.
Why not. Eight numbers can't settle anything, but at least they settle that after 1604 it's empty.
She said: eight numbers can't settle anything. Put them in, and people will remember the empty-after-1604 and forget the other four words.
Which four words.
She said: sample size of eight.
He went quiet. After a while he said: Shijie, right now you sound exactly like the Nanshan crowd.
She said: yes.
He said: I'm insulting you.
She said: I know.
She did the second ruler herself.
Carbon-14 in tree rings records cosmic-ray storms. Synchronized worldwide; trees can't collude. Four known events: 774, 993, 1052, 1279. Amplitudes in per mil, each measured once per chronology—one Japanese cryptomeria, one central-European oak; the two stay within 0.4 of each other.
774: 12.0.
993: 9.3.
1052: 5.1.
1279: 4.9.
The step sits between 993 and 1052. A fall of forty-five percent.
She looked at those four numbers for two hours. 1052 and 1054—two years apart.
She wanted to look for a modern one next. Looked all evening; there was none. After 1950 this ruler breaks: carbon from fossil fuels diluted the atmosphere's carbon-14, and the bomb-test years piled on top of that after. The signal is buried underneath. You can't dredge it out.
She wrote on paper: ruler two, broken at 1950.
That afternoon she wrote Lu Weiming a letter, and it wasn't about any of this. She asked whether the solar radio flux records from 1968 to 1975 still existed.
His reply wasn't slow. It said: they do. On paper. Shanghai has a set going back to 1970, four readings a day—the same system your Old He worked under back then. Digitized only after 1979; before that it's all in the paper archive, hand-copied day by day. If you want them I can go look. Whatever I find, I'll photograph and send.
She replied: I want them.
He sent one more line: the meaning of this set isn't the Sun. It's that it's the only continuous sequence running from the late sixties down to today. Everything else broke somewhere.
She printed the letter and pressed it inside the paper notebook.
The third ruler was a hundred years long.
The Harvard plate stacks, 1890 to 1990, digitized photometry, open to any applicant. Of her 1,042, densely covered by plates: 217. Events cut from them: 31,000. She computed a clustering index in ten-year windows: fully random is zero, crowding together pushes it up.
1900: 0.09.
1910: 0.08.
1920: 0.10.
1930: 0.09.
1940: 0.13.
1950: 0.14.
1960: 0.17.
1970: 0.21.
1980: 0.24, error plus or minus 0.04.
The first forty years flat. After that, rising. She fitted a bend: 1936, error plus or minus seven years.
She sent this version to Las Campanas.
Two days later Mateo answered. It opened with one line of English: You gave me half. I ran it. 1939.
Below that, still in English, three lines: the magnitude zero point she used was off by 0.03 mag. He had rerun it on his own calibration. Bend at 1939, error plus or minus eight years. One line further down: same conclusion. Don't hand me half-finished work again.
She wrote back: three years sits inside your error, and inside mine.
He wrote back: 1936 and 1939 are both inside 1940. Pick one and write it.
She wrote: I'll write both.
He sent back a period.
She asked one more thing: why do you always rerun it yourself.
His answer was still English, longer than the last: I worked ten years in an ore-concentration plant. Slurry grade—when somebody hands me a number, if I don't run it myself, I don't know whether that number belongs to the ore or to the scale.
She wrote: this time it was the scale's.
He wrote: this time it's 0.03 mag. The scale's.
Julian date 2459537, Saturday.
In the morning she stored the summary plot of the 31,000 events into 3t. Done, she opened the mailbox. The message titled "Shoulder" was still there, last modified still 2459483.793. She clicked the cursor into the recipient field, typed nothing, closed it.
Old Tang sent one: the station-office form, twelve days overdue. This time in writing. It's landed at the institute office.
She replied: understood.
At noon, on the way to the canteen, she ran into Eli. He said two reporters had come to the gate yesterday afternoon; the gatehouse kept them outside. They stood about forty minutes, took a few photographs of the front gate, and left.
She said: what did they ask.
He said: the No. 7 feed.
She said: what did you tell them.
He said: I told them the feed at this station hasn't been clean in thirty years. He laughed once at himself, and after the laugh added: that sentence is the truth.
In the afternoon she laid the three rulers on one sheet of paper.
The first: eight points, four bins, useless. Broken at 1604, four hundred sixteen empty years since.
The second: four points, broken at 1950. Step between 993 and 1052.
The third: one hundred years, bending at 1936—or 1939.
The three curves were like three thermometers. The first has only eight graduations. The second's mercury column broke at 1950. The third only ever measured the last hundred years.
She photographed the page and sent it to Vienna.
The reply came at dusk.
Ursula wrote four lines:
One. A bend inside a single century, and you say we did it. Your kind always confesses first. Confessing is less work than working.
Two. Nine hundred years ago, under that step, there was no one. No transmitters, no radar, none of you.
Three. I don't concern myself with who woke whom. I concern myself with whether the number is monotone. At present it is monotone.
Four. Burn this in: these three are not S. Not one of these numbers is called S. Compare them with 0.31 and I will not speak to you again.
She set the phone down when she'd read them. What she was thinking of wasn't the four lines. It was 1968, a twenty-two-year-old doing calibration at a radar station already struck from the rolls, four times a day, for two years and three months.
She had meant to join the step and the bend into one line and compute a rise per century. Halfway through she stopped. The three rulers don't share units. Ursula had said it: calibrate them against each other and you're finished.
She left that step empty, drew a bracket on the paper, and wrote nothing inside the bracket.
From 1052 to 1936, eight hundred eighty-four years between, and all she held of them was the emptiness after 1604.
In the tank the water was twenty degrees. Lao Wu flat against the glass, claws upward, shell still the old one. She counted the notches on the driftwood: still three, the third no deeper. She dropped in two pellets. The crayfish didn't move.
On her phone, one from Dr. Shen, sent Thursday afternoon: the booth is free Monday morning. Coming or not.
She replied: another day.
The thirteenth time.
At eight she video-called Zhou Yao.
This time it went through. Three minutes forty-one.
The camera was pointed at a sheet of paper; Zhou Yao was drawing, only half her face in frame.
She said: that note—what did you write.
Zhou Yao said: not telling.
She said: then whose name did you sign.
Zhou Yao said: my own.
She said: when Dad asked about my ears, what did you say.
Zhou Yao said: I didn't say anything.
She said: oh.
Zhou Yao said: Mom, what time is it there.
She said: eight.
Zhou Yao said: oh.
Then neither of them spoke. She could hear, on the far end, a pen moving on paper.
After they hung up she checked the call record: three minutes forty-one.
Julian date 2459538, Sunday, 2:41 in the morning.
When the phone rang she wasn't asleep. She was reading the distribution of the 31,000 events.
An unknown number on the screen. Beijing area code.
She answered.
Silence first, at the other end. Then an old man's voice: Xiao Zhou.
She said: yes.
Only after the word was out did she place it: He Zhaoting.
He said: I've found a machine.
She said: what machine.
He said: a reel-to-reel, built in 1981. Belts replaced twice. The speed is off. But it turns.
She said: and the wrinkled stretch, near the rim.
He said: bypassed. The wrinkled part won't pass. I cut the tape on both sides of it and spliced the ends together.
She said: how much is missing in between.
He said: how much, I don't know. I know that it is.
She said nothing.
He said: listen.
Then she heard something else. Hiss first, wide, pressed down underneath—the tape's own thirty years of noise floor. Over the hiss, the second marks: one short tone a second, and after sixty short tones, a long one. She counted three long ones.
After that came something very slow, so slow it didn't seem like sound—pushed up from low to high a little at a time, up to the top, then back down, twice through.
She moved the phone from her right ear to her left.
That stretch ran about two minutes. When it was done, hiss again.
He said: that passage is the six a.m. reading, April 7, 1968.
She said: four times a day.
He said: six, twelve, eighteen, twenty-four.
She said: mm.
He said: tomorrow I'll listen through the other three.
She said: there's no machine on my end.
He said: I know.
She said: and the other two reels—
He said: they're with me.
She waited for the next sentence. It didn't come. He asked nothing about delay, nothing about the data. Not one word.
She said: Old He.
He said: did you hear it.
She said: I heard it.
He said: good.
And he hung up.
She set the phone on the desk, screen still lit. She turned the paper notebook to the Beijing page. The number in the corner was still there: 2439954.
Under it she wrote one line: 6:00.
Under that, one more: 252.
She flipped back a page, to a sentence she had written: 1968—quartz clock plus shortwave time signals, millisecond level. Milliseconds can erase a synchronization. They cannot build one.
She put a dot under the sentence.
Call record: 252 seconds.