Harry Potter and the Methods of Rationality

persuaded Rabi, and Fermi had abided by the majority vote of their tiny three-person conspiracy. And so, years later, the only neutron moderator the Nazis had known about was deuterium.

The only deuterium source under Nazi control had been a captured facility in occupied Norway, which had been knocked out by bombs and sabotage, causing a total of twenty-four civilian deaths.

The Nazis had tried to ship the deuterium already refined, on board a civilian Norwegian ferry, the SS Hydro.

Knut Haukelid and his assistants had been discovered by the night watchman of the civilian ferry while they were sneaking on board to sabotage it. Haukelid had told the watchman that they were escaping the Gestapo, and the watchman had let them go. Haukelid had considered warning the night watchman, but that would have endangered the mission, so Haukelid had only shaken his hand. And the civilian ship had sunk in the deepest part of the lake, with eight dead Germans, seven dead crew, and three dead civilian bystanders. Some of the Norwegian rescuers of the ship had thought the German soldiers present should be left to drown, but this view had not prevailed, and the German survivors had been rescued. And that had been the end of the Nazi nuclear weapons program.

Which was to say that Knut Haukelid had killed innocent people. One of whom, the night watchman of the ship, had been a good person. Someone who'd gone out of his way to help Haukelid, at risk to himself; from the kindness of his heart, for the highest moral reasons; and been sent to drown in turn. Afterward, in the cold light of history, it had looked like the Nazis had never been close to getting nuclear weapons after all.

And Harry had never read anything suggesting that Haukelid had acted wrongly.

That was war in real life. In terms of total damage and who'd gotten hit, what Haukelid had done was considerably worse than what Dumbledore might have done to Narcissa Malfoy, or what Dumbledore had possibly done to leak the prophecy to Lord Voldemort to get him to attack Harry's parents.

If Haukelid had been a comic-book superhero, he'd have somehow gotten all the civilians off the ferry, he would've attacked the German soldiers directly...

...rather than let a single innocent person die...

...but Knut Haukelid hadn't been a superhero.

And neither had been Albus Dumbledore.

Harry closed his eyes, swallowing hard a few times against the sudden choking sensation. It was abruptly very clear that while Harry was going around trying to live the ideals of the Enlightenment, Dumbledore was the one who'd actually fought in a war. Nonviolent ideals were cheap to hold if you were a scientist, living inside the Protego bubble cast by the police officers and soldiers whose actions you had the luxury to question. Albus Dumbledore seemed to have started out with ideals at least as strong as Harry's own, if not stronger; and Dumbledore hadn't gotten through his war without losing friends and killing enemies and sacrificing allies.

Are you so much better than Haukelid and Dumbledore, Harry Potter, that you'll be able to fight without a single casualty? Even in the world of comic books, the only reason a superhero like Batman even looks successful is that the comic-book readers only notice when Important Named Characters die, not when the Joker shoots some random nameless bystander to show off his villainy. Batman is a murderer no less than the Joker, for all the lives the Joker took that Batman could've saved by killing him. That's what the man named Alastor was trying to tell Dumbledore, and afterward Dumbledore regretted having taken so long to change his mind. Are you really going to try to follow the path of the superhero, and never sacrifice a single piece or kill a single enemy?

Fatigued, Harry turned his attention away from the dilemma for a moment, opened his eyes again to regard the hemisphere of night, which required no decisions from him.

Near the edge of his vision, the pale white crescent of the Moon, the light from which had left one-and-a- quarter seconds ago, around 375,000 kilometers of distance in Earth's space of simultaneity.

Above and to the side, Polaris, the North Star, the first star Harry had learned to identify in the sky by following the edge of the Big Dipper; that was actually a five-system with a brilliant central supergiant, 434 light-years from Earth. It was the first star whose name Harry had ever learned, so long ago that he couldn't have guessed how old he'd been.

The dim fog that was the Milky Way; so many billions of distant stars that they became an indistinct river, the plane of a galaxy that stretched 100,000 light-years across.

In the center of the constellation Andromeda, the star Andromeda, which was really the Andromeda Galaxy. The nearest galaxy to the Milky Way, 2.4 million light-years away, containing an estimated trillion stars.

Numbers like those made 'infinity' pale by comparison, because 'infinity' was just featureless and blank. Thinking that the stars were 'infinitely' distant was a lot less scary than trying to work out what 2.4 million light- years amounted to in meters. 2.4 million light-years, times 31 million seconds in a year, times a photon moving at 300,000,000 meters per second...

It was strange to think that such distances might not be unreachably far away. Magic was loose in the universe, things like Time-Turners and broomsticks. Had anyone even measured the speed of a portkey, or a phoenix? And the human understanding of magic couldn't possibly be anywhere near the underlying laws. What would you be able to do with magic if you really understood it?

A year ago, Dad had gone to the Australian National University in Canberra for a conference where he'd been an invited speaker, and he'd taken Mum and Harry along. And they'd all visited the National Museum of Australia, because, it had turned out, there was basically nothing else to do in Canberra. The glass display cases had shown rock-throwers crafted by the Australian aborigines - like giant wooden shoehorns, they'd looked, but smoothed and carved and ornamented with the most painstaking care. In the 40,000 years since anatomically modern humans had migrated to Australia from Asia, nobody had invented the bow-and-arrow. It really made you appreciate how non-obvious was the idea of Progress. Why would you even think of Invention as something important, if all your history's heroic tales were of great warriors and defenders instead of Thomas Edison? How could anyone possibly have suspected, while carving a rock-thrower with painstaking care, that someday human beings would invent rocket ships and nuclear energy?

Could you have looked up into the sky, at the brilliant light of the Sun, and deduced that the universe contained greater sources of energy than mere fire? Would you have realized that if the fundamental physical laws permitted it, someday humans would tap the same energies as the Sun? Even if nothing you could imagine doing with rock- throwers or woven pouches - no pattern of running across the savannah and nothing you could obtain by hunting animals - would accomplish that even in imagination?