DURING THE FIRST FEW DAYS AFTER THE MOON HAD BLOWN UP, Doob had spent hours gazing up at Potatohead, Mr. Spinny, Acorn, Peach Pit, Scoop, Big Boy, and Kidney Bean. They were visible in the daytime, just as the moon had formerly been, and even on the rare day when it was cloudy in Pasadena, or he was stuck indoors, he could pull up a window on the screen of his computer and watch them on a live video feed.
After he had figured out that they were going to kill everyone on Earth, he had become a lot less interested in staring at them. He had, in fact, sometimes gone for weeks without looking up at the gradually spreading cloud of debris. Sometimes while walking across a dark parking lot or driving down the highway he would catch sight of the moon-chunks in the sky and deliberately turn his gaze away from them. They filled him with horror and even a kind of shame over the fact that he had once found the whole thing such a fascinating science treat. He did not want to be reminded of it. Instead he tracked the slow disintegration of the moon-pieces through spreadsheets and plots shared with him by his graduate students and his colleagues. He did everything he could to reduce the whole state of affairs to two numbers. One of these was the Bolide Fragmentation Rate, or BFR, which was a measure of how frequently big rocks were being made into small rocks. The other was, quite simply, how many days remained before the White Sky.
On Day 7, minutes after they had met, he and Amelia had watched Kidney Bean fracture into two big chunks, later dubbed KB1 and KB2 (though attempts had been made at the time to give them cutesy names of their own). Three weeks later Scoop had collided with Big Boy and broken into three pieces, SC1, SC2, and SC3. Big Boy itself was now BB1, still fairly recognizable, plus a whole family tree of bits that had shrapneled off its smaller piece, BB2. These were given code numbers such as BB2-1-3, meaning the third-biggest fragment of the largest fragment of the second-biggest piece of Big Boy. Beyond about that level it became difficult, and somewhat pointless, to keep track of them all. Mr. Spinny had caused all sorts of havoc before finally breaking in half; its wayward children MS1 and MS2 had gone winging off in opposite directions and ended up in big eccentric orbits around the rubble cloud’s shared center of mass, occasionally looping in from a great distance and slamming into one of the slower-moving pieces. MS2 had broken Acorn into three pieces just three days before Doob’s memorable Oval Office chat with the president. While he’d been flying back to L.A., a hunk of it the size of an oil tanker had slammed into the Indian Ocean and kicked up a tsunami that had killed forty thousand people on the west coast of India.
After he got home from his trip to D.C., he and Amelia checked into a suite at the Langham, a palatial hotel in Pasadena, so that they could spend a few days together before he went out on a round-the-world journey. All through their romantic dinner on the terrace he made a concerted effort not to look at the remains of the moon. Later they went back to their suite and made love. After twenty minutes’ postcoital cuddling, Amelia rolled over on her side and went to sleep, inviting Doob to spoon with her, but Doob, unable to relax, pulled his tablet onto his lap, put on his reading glasses, and started killing time on the Internet. The French doors to the balcony were open, and at some point the breeze coming in through them obliged Amelia to snuggle deeper under the blankets. Doob got up and walked over to close the doors, and was confronted by the sight of the moon-cloud, directly in front of him, hanging over the lights of L.A., and now something like four times the diameter of the original moon. It was arresting, partly because it had been so long since he had looked squarely at it, and so he stood there for a while observing. Peach Pit was still largely in one piece, but other than that the original Seven Sisters were no longer discernible.
Out of curiosity he consulted an app that told him when Izzy would be passing over, and saw that it was going to happen in about ten minutes. So he stood there and waited for it. As he waited, his attention turned again and again to the pieces of the moon. What was their future? He knew that they would shatter into an uncountable number of fragments and become the White Sky and then the Hard Rain. But what was the final distribution of sizes going to be, how many big ones and how many small? They had some models based on the simplifying assumption that all moon rock was basically the same, but clearly that wasn’t true.