OK, this is too good to pass up. Jim Blinn, the computer-graphics expert responsible for the Mechanical Universe animations — and therefore, responsible for filling my childhood with arrows — summarizes The Mechanical Universe in nine minutes. Watch all of first-year physics packed in a single morsel:
In the brief interlude between my morning of debugging PHP code — Semantic MediaWiki isn’t compatible with Cite.php, the bastards! — and my afternoon of category theory, I’d like to call attention to a few items.
First, an observation: for some reason I can’t quite fathom, I was able to adapt myself to using HTML entities for punctuation marks, writing — for — and the like, but my brain didn’t process the fact that HTML entities also exist for accented letters. Instead of typing, say, à to get à, I would hit Ctrl+T to open a new Firefox tab, hit the Tab key to move to the Search bar, type a French phrase which I knew had the accented characters in question, copy the characters I needed from the search-result summaries, and paste them where I needed them.
Searching was easier than typing. Now, that’s either a sign of advanced Internet-induced brain rot, or an indication that our interconnected world has definitively left TwenCen far behind.
Last September, New Scientist magazine published a story about the “EmDrive,” a machine designed and built by the British engineer Roger Shawyer, who claimed that his contraption could produce a net forward acceleration by bouncing microwaves around inside a metal cavity. Onward to the stars, etc. Now, nobody else has been able to reproduce what Shawyer claims he’s seen, and Shawyer’s assertion that standard relativity and electromagnetism predict such an acceleration is, to put it mildly, nonsense. The conservation of momentum is built deeply into the mathematical structure of these principles, and so whatever the fine details of Shawyer’s machine, his claim is wrong.
It’s always possible that some new physics came raining out of the sky and landed in Shawyer’s garage, but if nobody can reproduce his “result,” there’s no reason to speculate about it.
Although basic tenets of E&M imply that radiation pressure can’t impart a net thrust to a closed cavity, it’s fun to see the details for how this works out, particularly in the sort of asymmetric conical shape which Shawyer built. Greg Egan has written up the details, in an essay I didn’t know about till now:
Last night, Michael Behe was Stephen Colbert’s guest on The Colbert Report. It was, shall we say, educational.
BEHE: Nobody was searching for the limits of Newton’s theory when Newton first proposed it. He thought that he had solved all of physics. But then when —
COLBERT: You mean about how — how apples fall?
BEHE: Apples fall, cannonballs go. But then —
BEHE: But then when —
COLBERT: He invented the cannonball? He invented the dive — the cannonball?
BEHE: Cannonballs fly.
Oh, yes. It’s nice to know that nobody checked to see if Newton was right, or if “universal gravitation” was really universal.
Wait. You say that it was Edmund Halley who used Newton’s laws to predict that comets travel in elliptical orbits, and that the comet seen in 1456, 1531, 1607 and 1682 would return in 1758? How could Halley say such a thing, after Newton had made his view clear that all comets travel in parabolic paths? It’s in the Principia, for Heaven’s sake! And you say that Halley was the one who realized that the stars are not fixed to a “celestial firmament” but instead move through space? How dare you imply that the views of one person are not the entirety of science! Sir, how dare you have the temerity to insist that people did not take Newton at his word but instead used his theories to make predictions about the world which they could then compare to observations to — I can hardly even articulate such a heretical notion — see if Newton was wrong.
What! Are you telling me it was the French, those wine-swilling, toad-munching surrender monkeys, who had the audacity to test Newton’s prediction that the Earth is an oblate spheroid? Sir, you could tell me all you want about the 1735 expeditions to Peru and Lapland under Charles-Marie de La Condamine and Pierre-Louis Moreau de Maupertuis respectively — the former of which incidentally brought back the first rubber and curare Europe had ever seen — but the mere suggestion that Newton’s word was not good enough is so repugnant I refuse to consider the matter further.
Just so nobody gets too excited â€” this paper is complete nonsense, not worth spending a minuteâ€™s time on. If I find the energy I might post on it, but this is no better than the other hundred crackpot preprints I get in the mail every year.
For details, you can start here and here. It looks like I might have to dig that post out of my “drafts” pile after all. . . .
Finally, of course, we should all welcome Phil Plait into the League of Moral Ambiguity, for while he’s still vacillating between superhero and supervillain attributes, he’s definitely in a comic book!
Those of you interested in the way the Wobosphere functions as a disputation arena (“We Can Fact-Check Yo’ Ass!”) may be interested in the following sordid tale of intrigue and skullduggery. I originally wrote most of this last October, in a lengthy comment on David Brin’s blog. The moral of the story, insofar as I can find one, is this: if you say that you can move your car forward by bouncing a soccer ball back and forth inside it fifty thousand times, you’ll get a quizzical look (at best). If you say the same thing but with “microwave photons” instead of soccer balls, you’re reporting on cutting-edge science!
Back in September, New Scientist magazine published an article on the “EmDrive”, a machine purportedly able to propel itself using microwaves bouncing inside a box. Those of us who remember the Dean drive and umpty-ump other wonder machines have no trouble recognizing this as the same old stuff: like all the wonder-powered spacedrives before it, it can only putter forward by violating the conservation of momentum. New Scientist‘s reportage provoked science-fiction writer Greg Egan to write an open letter saying he was “gobsmacked by the level of scientific illiteracy” the magazine showed.
So it goes, as they say on Tralfamadore. Claims of exotic spacedrives fuelled by violations of fundamental physics are, sadly but understandably, about twopence a dozen. The aspect of the affair which Egan found truly disturbing — indeed, reprehensible — was the way New Scientist glibly provided a “news” piece full of pseudoscientific gibberish purely to justify how the EmDrive might work. (Their argument really pushed the limits of the absurd, too: Einstein’s relativity has momentum conservation built into its mathematical structure, so you can’t use relativity jargon like “reference frames” to sidestep the conservation law.)