Wiki Contributions


And also computationally impossible for a space endeavor of any size until the late 90’s (citation needed here and would love to hear from someone with experience).

I looked into it and, yes, this looks basically correct with a caveat: it's computationally very expensive to get those first stages to land on their own at a convenient, precisely chosen location. We've been doing propulsive landings for decades with e.g. the Apollo moon landers and the Viking Mars probes, the latter of which had to be fully autonomous because of speed-of-light delays. Landing a big long rocket is a bit harder because of its somewhat unwieldy shape, but inverted pendulum control problems are definitely not a new thing.

So where does it get computationally hard? There are two parts to it. The first part is computing a trajectory and a flight plan -- when you should fire up the engines, which way you should be pointing them, what the aerodynamic control surfaces should be doing -- which should get you to the desired landing location. This is a tricky optimization problem, with a bunch of annoyingly non-convex control constraints. The second hard part, and the reason you can't just precompute the flight plan on a really big computer before launching the rocket, is that you need to adjust the plan in realtime. There will inevitably be unpredictable deviations from the original plan caused by things like wind or variation in atmospheric density. If you don't compensate for them, those deviations will add up; the Curiosity Mars rover, for example, was a big improvement over its predecessors because its predicted landing zone was an ellipse that only measured 20 km by 7 km.

The algorithm (PDF) that I hear SpaceX is using does require some pretty serious processing power if you're going to be recomputing your entire flight plan several times per second.  A version suitable for realtime use wasn't flight-tested until the early 2010s.

There's also variation in the amount of children's television watched by people in the test population. The protagonist mentions seeing "less children's television than most children in our age cohort", and it's a safe bet that this was tracked as part of the data set.

Not just genetic tendencies; it was also meant to look at shared environment, like the TV shows subtly but thoroughly pushing a certain worldview, and the words from teachers saying it explicitly. From the story: they wanted "to find out how well we were doing environment-wise and heredity-wise on people's kindness and resistance to conformity-pushed cruelty".

Ah. That web site throws out too many claims to investigate fully -- who has the time? -- but if you google around for a sampling of them you'll notice that they tend to crumble under scrutiny. The sections mentioning quantum mechanics are especially blatant: they're gibberish, total incoherent misuse of terminology.

EDIT: There's a sequence of articles called Mysterious Answers to Mysterious Questions which is relevant here. One that applies in particular is Fake Explanations, which could be summarized as "If you are equally good at explaining any outcome, you have zero knowledge." When people talk about "etheric worlds on different frequencies", or "energy vortices swirling faster than the speed of light on the earth plane", what does this predict? What, concretely, does it mean? If it can explain anything, then it predicts nothing.

If you were to try and search the space of all possible inputs for MD5, you'd quickly(ish) find an input that collided with the Obama Werewolf input, but it'd be garbage.

Really? Last I checked, the best known preimage attack against MD5 was too slow to be practical. Finding collisions is drastically easier, though I don't know any method for doing it with arbitrary plain-text English sentences.

Not just modern sexual attitudes, but specifically the sexual attitudes you see in the Harry Potter fanfiction community. And I'm sure it was meant to be jarring. Magical Britain's culture is subtly but deeply different from that of the muggle country that shares its borders; it would be profoundly weird if there were no surprises, no culture shock.

He's the Super Hufflepuff! He's taking all the electives, which is physically impossible without a Time Turner! He was mentioned right before Harry started making thorough off-screen preparations, and then conspicuously forgotten for the rest of the chapter! Dramatic logic dictates that he's got to show up at some point, probably in some way that involves time travel.

... Unless the whole thing was a throwaway joke about how useless Cedric was in Goblet of Fire, in which case yeah, I guess it was pretty funny.

An alternate interpretation is that Voldemort was strengthening a few of the spells that Sprout cast, as well as the spell that Tonks used to win the battle, and this use of his own magic was what caused Harry's doom-sense to tingle. If that's the case, then there would be none of his magic on the troll.

Other useful dummy values are $1, $42, $1,000,000, $9999999999999.95, and "'; DROP TABLE salary; --". As someone who has written input validation code for web forms on a few occasions, I personally give you my blessing to subvert them.

Load More