Plug in the claimed numbers. At 1kW in, it generates 1.2mN of thrust. At 100km/s that is a power of 1.2kW. Clearly such over-unity numbers are bogus, and the only place for bogosity to enter in is in the 1.2mN/kW.
That's why it must be bogus.
I'm not arguing; I'm ignorant and genuinely curious. (My last formal exposure to physics was over 35 years ago.)
Can you explain why this same reasoning wouldn't apply to any constant-thrust drive, such as a laser or microwave drive? Is it a matter of the thrust/power ratio? Is the "no-perpetual-motion" argument not that the EM drive can't produce any thrust, but that it can't produce so much?
You mentioned elsewhere that you support light-sail research. Hypothetical: Shine an ideally-focused laser upon a light sail. Does the light sail maintain a constant acceleration up to relativistic speeds?
I agree. The entire image is only about four times the Moon's diameter wide, which means (if my calculations are correct, bwa ha ha!) the Moon only travels through about 1-1.5 degrees of arc during the video (which is why DSCOVR could shoot it in only 5 hours). The effective pull of the Moon on the Earth is pretty much straight toward the observer the whole time.
But there are no real depth cues, so it's hard to judge that the two bodies are nearly a quarter-million miles apart.
Is that large bright area that stays centered in the Pacific the reflection of the Sun behind DSCOVR? If so, I'm surprised how large and diffuse it is. I suppose that even from a million miles away the surface of the ocean must be pretty rough.
Bingo. The whole point of the Caps Lock key is that you don't have to press it over and over. "...Around 0.1% of all keypresses" is a completely useless measurement. A measurement of how many other keys were pressed while the Caps Lock was on might actually mean something.
That said, the size and placement of Caps Lock are simply a historical accident. If keyboard manufacturers wanted to halve the size and stick another key left of A, that would be fine with me. (The "context menu" key that's missing from so many keyboards these days would be a great choice.)
Exactly what I came to say. I'd love to be able tell which tabs are pushing FF over 2GB, or carpet-bombing my CPUs when they auto-refresh, without having to close them all one by one.
Actually, who's hurt if Google delists the movie's IMDB page? Heck, Google should just delist every page about every Universal Pictures title in current release. See how fast Universal finds the problems with their automated takedown notices when all their titles—all their theater listings—disgoogle at once.
And 8 of the 10 Windows vulnerabilities were related to the Adobe Type Manager Font Driver (ATMFD.DLL). I don't know how much of ATMFD was written by whom, but according to Wikipedia, "Adobe licensed to Microsoft the core code." That makes Adobe responsible for 13 of the 15 vulnerabilities, including all 9 of the most dangerous.
It would have been nice if The Register's somewhat hysterical FA (much less the Slashdot summary) had made clear up front that Microsoft patched most of the Windows vulnerabilities all the way back in March (MS15-021), and the last one in May (MS15-044). According to j00ru's blog post, Adobe patched their holes in May as well.
j00ru was clear enough in his blog post, but El Reg decided to stick in one line: "Microsoft and Adobe issued patches in three updates."—six paragraphs down, looking more like an image caption than part of the article. Sheesh.
Man, I miss Northernlight. That was a search engine from the late 90s that actually tried to categorize results by topic, and returned a tree structure that you could navigate through. If you entered "Paris Hilton" you got a tree with separate branches for French hotels and for sluts.
But they went subscription-only after a few years, then they went away. Too bad.
You recently blogged ("Malware Evolution Calls for Actor Attribution") criticizing security companies that don't make the effort to identify the creators of malware. Do you think there are times when a company—such as Kaspersky in their recent attack—could be acting responsibly by deliberately suppressing (temporarily, one would hope) information they might have about the source of an attack?
Yes, except that significant digits are irrelevant when you speak of exact values. These days, 1" is defined as exactly 2.54cm (or 25.4mm or maybe even.0254m; I'm not sure of the actual definition), so 1" = 2.54cm is in fact exactly correct. Blame the fact that the common English numbering system has no way of distinguishing exact values from values lacking additional significant digits. That's why my old CRC Standard Math Tables used bold text for exact values.
"'E could 'a drawed me off a pint," grumbled the old man as he settled down behind a glass. "A 'alf litre ain't enough. It don't satisfy. And a 'ole litre's too much. It starts my bladder running. Let alone the price."
1984, George Orwell. [Doggone lousy Slashdot Unicode support.]
Amen to this. I hate listening to videos on my work computer. Furthermore, I can read a transcript a lot faster than the people in the video can talk—and I absorb the meaning better as well.
Interesting question. The explanation for ice skates I was taught as a kid (weight of skater forces surface of ice to melt, making it slippery) appears to be discredited. Still, I'd expect any loosely-bonded water molecules between skates and the ice would boil away instantly in near vacuum. Has anybody ever tried skating at very high altitude?
Slashdot Mirror
I'm not arguing; I'm ignorant and genuinely curious. (My last formal exposure to physics was over 35 years ago.)
Can you explain why this same reasoning wouldn't apply to any constant-thrust drive, such as a laser or microwave drive? Is it a matter of the thrust/power ratio? Is the "no-perpetual-motion" argument not that the EM drive can't produce any thrust, but that it can't produce so much?
You mentioned elsewhere that you support light-sail research. Hypothetical: Shine an ideally-focused laser upon a light sail. Does the light sail maintain a constant acceleration up to relativistic speeds?
Not saying he spent his campaign money on Russian hackers, but...
I agree. The entire image is only about four times the Moon's diameter wide, which means (if my calculations are correct, bwa ha ha!) the Moon only travels through about 1-1.5 degrees of arc during the video (which is why DSCOVR could shoot it in only 5 hours). The effective pull of the Moon on the Earth is pretty much straight toward the observer the whole time.
But there are no real depth cues, so it's hard to judge that the two bodies are nearly a quarter-million miles apart.
Is that large bright area that stays centered in the Pacific the reflection of the Sun behind DSCOVR? If so, I'm surprised how large and diffuse it is. I suppose that even from a million miles away the surface of the ocean must be pretty rough.
I still refer regularly to my CRC Standard Math Tables—two different editions, both sadly decades out of date.
I was tickled years ago to discover the OEIS; some other math website referred to it, and I was lost for hours. TV Tropes for math nerds.
Bingo. The whole point of the Caps Lock key is that you don't have to press it over and over. "...Around 0.1% of all keypresses" is a completely useless measurement. A measurement of how many other keys were pressed while the Caps Lock was on might actually mean something.
That said, the size and placement of Caps Lock are simply a historical accident. If keyboard manufacturers wanted to halve the size and stick another key left of A, that would be fine with me. (The "context menu" key that's missing from so many keyboards these days would be a great choice.)
Exactly what I came to say. I'd love to be able tell which tabs are pushing FF over 2GB, or carpet-bombing my CPUs when they auto-refresh, without having to close them all one by one.
I'll take either as long as the audio stays muted.
Takes me back to the 1970s. "What's a four-letter word for intercourse?" "Talk." Bet your sweet ass.
Actually, who's hurt if Google delists the movie's IMDB page? Heck, Google should just delist every page about every Universal Pictures title in current release. See how fast Universal finds the problems with their automated takedown notices when all their titles—all their theater listings—disgoogle at once.
17. I feel that restricting the use of Portable Electronic Device policy at work improves worker productivity
18. I feel that restricting the use of Portable Electronic Device policy at work enhances my employer's security
What do those questions even mean? "Restricting the use of PED policy"?
Anonymous Cowherd? Is that you?
And 8 of the 10 Windows vulnerabilities were related to the Adobe Type Manager Font Driver (ATMFD.DLL). I don't know how much of ATMFD was written by whom, but according to Wikipedia, "Adobe licensed to Microsoft the core code." That makes Adobe responsible for 13 of the 15 vulnerabilities, including all 9 of the most dangerous.
Not Dice's fault (this time); the summary just quotes The Register's opening hook.
It would have been nice if The Register's somewhat hysterical FA (much less the Slashdot summary) had made clear up front that Microsoft patched most of the Windows vulnerabilities all the way back in March (MS15-021), and the last one in May (MS15-044). According to j00ru's blog post, Adobe patched their holes in May as well.
j00ru was clear enough in his blog post, but El Reg decided to stick in one line: "Microsoft and Adobe issued patches in three updates."—six paragraphs down, looking more like an image caption than part of the article. Sheesh.
Man, I miss Northernlight. That was a search engine from the late 90s that actually tried to categorize results by topic, and returned a tree structure that you could navigate through. If you entered "Paris Hilton" you got a tree with separate branches for French hotels and for sluts.
But they went subscription-only after a few years, then they went away. Too bad.
You recently blogged ("Malware Evolution Calls for Actor Attribution") criticizing security companies that don't make the effort to identify the creators of malware. Do you think there are times when a company—such as Kaspersky in their recent attack—could be acting responsibly by deliberately suppressing (temporarily, one would hope) information they might have about the source of an attack?
It's wonderfully ironic that, with your signature, you're the first poster to actually comment on the story instead of the 95-meter needle.
Steve? Is that you?
Yes, except that significant digits are irrelevant when you speak of exact values. These days, 1" is defined as exactly 2.54cm (or 25.4mm or maybe even .0254m; I'm not sure of the actual definition), so 1" = 2.54cm is in fact exactly correct. Blame the fact that the common English numbering system has no way of distinguishing exact values from values lacking additional significant digits. That's why my old CRC Standard Math Tables used bold text for exact values.
1984, George Orwell. [Doggone lousy Slashdot Unicode support.]
Amen to this. I hate listening to videos on my work computer. Furthermore, I can read a transcript a lot faster than the people in the video can talk—and I absorb the meaning better as well.
Make it 440Hz; then I can tune my piano from it.
Interesting question. The explanation for ice skates I was taught as a kid (weight of skater forces surface of ice to melt, making it slippery) appears to be discredited. Still, I'd expect any loosely-bonded water molecules between skates and the ice would boil away instantly in near vacuum. Has anybody ever tried skating at very high altitude?
It doesn't seem to shine in the dark, so probably not. Kinda rules out lights from an active alien base, as well. Bummer.