Harry Potter and the Methods of Rationality

Because rockets did not work by Aristotelian physics.

Rockets did not work like a human mind instinctively thought a flying thing should work.

A rocket-assisted broomstick, therefore, did not move like the magical broomsticks upon which Harry was such a very good flyer.

None of this actually went through Harry's mind at the time.

For one thing, the loudest noise he'd ever heard in his life was preventing him from hearing himself think.

For another thing, accelerating upward at four gravities meant that he had around two and a half seconds, total, to go from the bottom to the top of Azkaban.

And even if they were two and a half of the longest seconds in the history of Time, that wasn't enough room to do much thinking.

There was time only to see the lights of the Aurors' curses arrowing down at him, slightly angle the broomstick to avoid them, realize that the broomstick was simply continuing on with mostly the same momentum instead of going in the direction he pointed it, and activate the wordless concepts

*crap*

and

*Newton*

whereupon Harry angled the broomstick much harder and then they started to very quickly approach the wall so he angled it back the other way and there were more lights coming down and the Dementors were sliding smoothly up toward them along with some kind of giant winged creature of white-golden flame so Harry wrenched the broomstick back toward the sky but now he was still sliding toward another wall so he tilted the broom slightly and he stopped approaching but he was too close so he tilted it again and then the distant Aurors on their broomsticks weren't very distant at all and he was going to crash into that woman so he spun his broomstick straight away from her and then in another instant he realized his rocket was an extremely powerful flamethrower and in a fraction of a second it would be pointing directly at the Auror so he spun the broomstick sideways as he kept going up and he couldn't remember if it was pointing at any Aurors now but at least it wasn't pointing at her

Harry missed another Auror by about a meter, zipping past him on a sideways-pointed flamethrower moving upward at, Harry would later guess, around 300 kilometers per hour.

If there were any screams of roasted Aurors he didn't hear them, but this was not evidence one way or another, because all that Harry was hearing at the moment was an extremely loud noise.

A couple of calmer if not quieter seconds later, there didn't seem to be any Aurors around, or any Dementors, or any giant winged flame creatures, and the vast and terrible edifice of Azkaban looked surprisingly tiny from this height.

Harry got the broomstick pointed toward the Sun, faintly visible through the clouds, it wasn't high in the sky at this time of day and month of winter, and the broomstick accelerated for another two seconds in that direction and picked up an amazing amount of speed very quickly before the solid-fuel rocket burned itself out.

After that, once Harry could hear himself think again, when there was only the howling wind from their ridiculous speed, and Harry's enchantment-assisted fingers gripping the broomstick were merely resisting the decelerating drag of moving way faster than terminal velocity, that was when Harry actually thought all that stuff about Newtonian mechanics and Aristotelian physics and broomsticks and rocketry and the importance of curiosity and how he was never going to do anything this Gryffindor ever again or at least not until after he learned the Dark Lord's secret of immortality and why had he listened to Professor Quirinus "I asssure you, boy, I would not attempt thisss if I did not anticipate my own ssurvival" Quirrell instead of Professor Michael "Son, if you try anything to do with rockets on your own, I mean anything whatsoever without a trained professonal watching, you will die and that will make Mum sad" Verres-Evans.

"WHAT?" shrieked Amelia at the mirror.

The wind had died down to a bearable level as the air resistance slowed them, giving Harry plenty of opportunity to listen to the buzzing, ringing sound that seemed to fill his whole brain.

Professor Quirrell had been supposed to cast a Quieting Charm on the rocket exhaust... apparently there were limits to what Quieting Charms could do... in retrospect, Harry should have Transfigured a pair of earplugs, not just trusted to the Quieting Charm, though that probably wouldn't have been enough either...

Well, magical healing probably had something to treat permanent hearing damage.

No, really, magical healing probably had something to treat that. He'd seen students go to Madam Pomfrey with injuries that sounded a lot worse...

Is there some way of transplanting an imaginary personality to someone else's head? asked Hufflepuff. I don't want to live in yours anymore.

Harry shoved it all into the back of his mind, there really wasn't anything he could do about it right now. Was there anything he should be worrying about -

Then Harry glanced behind him, remembering for the first time to check whether Bellatrix or Professor Quirrell had been blown off the broomstick.

But the green snake was still in its harness, and the emaciated woman was still clinging to the broomstick, her face still charged with unhealthy color and her eyes still bright and dangerous. Her shoulders were shaking like she was laughing hysterically, and her lips were moving as though to shout, but no sound was coming out -

Oh, right.

Harry took off the hood of his cloak, tapped his ears to let her know he couldn't hear.

Whereupon Bellatrix grasped her wand, pointed it at Harry, and suddenly the ringing in his ears diminished, he could hear her.

A moment later he regretted it; the imprecations she was screaming at Azkaban, Dementors, Aurors, Dumbledore, Lucius, Bartemy Couch, something called the Order of the Phoenix, and all who stood in the way of her Dark Lord, et cetera, were not suitable for younger and more sensitive listeners; and her laughter was hurting his