The American Physical Society produced a report on the feasibility of various boost-phase ballistic missile interception capabilities, back in 2003.
There's a brief summary here [www.physicstoday.org], and the full report is available here [www.aps.org].
From the section of the summary talking about airborne laser (ABL) defenses:
In assessing the usefulness of the ABL, the study group adopted its publicly reported design goals: 3 MW of power focused into a 1.2-m-diameter beam (close to the diffraction limit) that could illuminate the target missile for up to 20 s. We also considered the utility of systems with greater and lesser capabilities. We found that if the ABL achieves its design goals, it would have a range of about 600 km against liquid-propellant ICBMs. That would be useful against liquid-propellant ICBMs launched from North Korea, but not from Iran. Against solid-propellant ICBMs, its range would be only about 300 km, too short to be useful in any of the scenarios we examined. The ABL's range is relatively insensitive to its power.
Note that they assumed that all the publically stated goals could be reached -- i.e., they ignored any possible engineering difficulties. Also note that the laser needs to stay focused on the target for several seconds, not just a few milliseconds as some posters have claimed: given the proposed beam power, it takes that long to heat up the . Solid-propellant rockets are harder to destroy because they're structurally much stronger (most of a liquid-propellant rocket is a thin-skinned metal fuel tank).
Oh, dear. The "Roosevelt knew it was coming and deliberately did nothing" conspiracy argument. I'm afraid it's nowhere near as paranoid as you make it out to be. I suggest you try reading a serious history, like Gordon Prange's At Dawn We Slept, rather than conspiracy-theory nonsense.
Or read this exchange from the New York Review of Books Letters column, between Gore Vidal (a novelist who dabbles in conspiracy theory) and David Kahn (a serious historian who wrote, among other things, one of the definitive histories of cryptography):
You could argue that the Japanese were "pushed" into a confrontation with the US, because the US cut off their supply of American oil in July, 1941, in response to Japanese troops moving into French Indochina. But only if you think that continued Japanese military expansion in China and Southeast Asia was somehow inevitable -- or justified.
The Japanese government could have their halted their expansion, of course; but they decided to continue. In order to do so, they needed access to oil, rubber, and other critical military supplies, so they planned to conquer Indonesia and Malaysia. In order to prevent the US from interfering in this expansion, they planned a series of attacks and invasions to knock out the US presence in the western Pacific and take out the US navy.
The Japanese were certainly not suckered into attacking Pearl Harbor; they carefully planned it, based in part on the earlier success of the British carrier aircraft in attacking the Italian naval base at Taranto in the Mediterranean (something the US ignored). Japanese military leaders started debating and planning war with the US in mid-1941; they had made the decision for war by the fall.
The US expected that a Japanese attack would most likely come in the Philippines; in part, they simply didn't think the Japanese capable of something as audacious and difficult as a long-range, carrier-based attack on Hawaii.
(Leaving aside all this, may I point out that if you are "suckering" someone into attacking you, you do this in order to ambush them when they make the attack, not let them go ahead and destroy most of your fleet?)
Actually, that's two defining events. First, Japan attacked Pearl Harbor and forced the US into war with Japan; second, Hitler declared war on the US a few days later (with Mussolini rather predictably following soon after). Why Hitler did this has never been entirely clear; the Axis agreement was a mutual defense treaty, so Germany was not obligated to join Japan if Japan attacked another country first.
So there's the possibility (perhaps not a very high one) that WWII could have remained split into unrelated Pacific/Asian and European sectors, with the US fighting Japan but not Germany.
RPG companies of the late 1970s in many ways parallel the dot-com industry in the 1990s.
Um, no, not really. What outside investors were bothering with gaming companies in the 1970s? The closest thing to booms (and attendant cash-flow problems) were probably White Wolf and Wizards of the Coast -- in the 1990s.
And Gygax was never "eaten" by TSR -- he was part of the original company, and ran it for a number of years. Original D&D was a TSR product right from the start.
1. Hubble was designed to be launched by the Shuttle; but the Shuttle is now supposed to be devoted to essentially nothing but International Space Station missions. Moreover, the cost of a Shuttle launch itself is of order $600 million. I'm not sure if the US has any unmanned rockets capable of launching the Hubble; even if we did, there would have to be at least some redesign costs to get the replacement Hubble to fit safely inside the rocket's nose and then deploy properly.
2. The de-orbiting module has to be attached to Hubble at some point anyway, otherwise there is the danger that when Hubble's orbit decays, it will strew bits of itself across populated areas. So you still have to send a robotic mission that can rendezvous and dock with Hubble, even if you're not attempting to repair and enhance it.
Yes, there are several other instruments; and, as a previous poster noted, these other instruments account for about 70% of Hubble's typical observing. There's more on the various instruments, past and present, here:
http://www.stsci.edu/hst/HST_overview/; and links to more technical descriptions here: http://www.stsci.edu/hst/HST_overview/instruments/.
Briefly, there's ACS (Advanced Camera for Surveys), which does both optical and UV imaging; WFPC2 (Wide Field Planetary Camera 2), the older UV/optical imager; and NICMOS, which does near-infrared imaging. Both ACS and NICMOS also have spectroscopy modes, though they don't make up for what STIS does, or did.
Depending on what you're trying to look at, individual exposure times range from about a second to 30 minutes or so (longer than that, and you start getting too many cosmic ray hits that add noise to your data).
Planes usually aren't a problem; satellites (and meteors!) occasionally are. It depends on how big your field of view is (a degree across or just a few minutes of arc?) and how long you expose for.
An example from an observing program of mine: in a total of about 80 five-minute exposures of nearby galaxies, with a field of view about 0.1 degrees across, there were two exposures with satellite tracks on them. Annoying, but tolerable.
Actually... those are some seriously strange claims! Portuguese colonies in Greenland? Good "secret conspiracy-theory alternate history," not so good "real world" history.
Greenland was settled by Norse explorers in the Middle Ages (and of course earlier by various peoples from North America); the colony was cut off from Europe sometime in the late 1300s or early 1400s, and perished sometime in the 15th or 16th Century. The Portuguese were busy sailing down the coast of Africa and around into the Indian Ocean. They weren't going to Greenland!
(Now, had Columbus somehow ended up in Iceland, and somehow gotten someone to translate a few of the old pagan sagas, he might have deduced the existence of lands to the west. Lands with not much to offer except grapes and hostile natives, according to the sagas, so Columbus probably wouldn't have been too interested anyway.)
The reason Columbus insisted that China was close enough to be reached by contemporary sailing ships from Spain was because he simply got the distance wrong. As you mention, the radius of the earth had been accurately measured over a thousand years earlier, by the Alexandrian Greek Eratosthenes. He gave the earth's circumference in stadia, a common unit in Hellenistic times.
So how long is a "stadium"? Ah, there's the problem -- in late 15th Century Europe, they had recovered Eratosthenes' work, but not enough of the context, so they didn't really know. Columbus argued for a small value, which made the earth small and China not too far away. His academic opponents argued for a larger value, which would mean China was too far away. And, as we all know, Columbus was... well, wrong. His ships would have run out of food and water well before reaching China, but they luckily ran into the Americas on the way.
I think the idea was more to compare cathedrals and bazaars as functioning institutions, rather than in the sense of "how do you build them?" Cathedrals are organized, hierarchical entities, with scheduled ceremonies, committees, and managers (in a generic sense). You can't just walk in and suggest changes to a service or set up your own altar... Bazaars, on the other hand, *are* whover shows up and pitches a tent and tries to buy or sell, with no one trying to run the show and tightly regulate things. At least, that's the first-order comparison.
In fact, I think bazaars *do* require a certain amount of behind-the-scenes coordination: most historical Middle Eastern bazaars had officials who regulated weights and measures and prosecuted fraud, in addition to at least some kind of police presence to discourage thieves and robbers from taking whatever they wanted. And the actual construction of cathedrals involved a certain amount of community participation and contribution, from traveling artisans who helped spread Gothic style and techniques throughout Europe, to local citizens contributing their own labor and money to the building.
ESR's point, I think, was mainly to come up with some vivid metaphors to highlight the differences he perceived in software construction practices -- stately, organized, closed institution versus seemingly anarchic free-for-all -- rather than to make some historically [pedantically] accurate comparison. And maybe he had structures like the Cathedral of Cologne in mind, as well: begun in the Middle Ages and not actually finished until the 19th Century. Translated to computer timescales, that's at least a little like the slow progress of the GNU Hurd, or Windows NT 5, or...
Actually, we do see members of other species. One of the entertaining things about the Senate scene is seeing how many of the various species you can recognize from, e.g., the cantina scene in Episode IV. I'm pretty sure there's a small group of the walrus-faced guys (one of whom went after Luke and got cut down by Kenobi in the cantina scene), as well as the whatever-they-are's with three eyes. Probably some others I missed.
Re English as the universal language: well, I think you're supposed to take that as a convenient translation of whatever the "common" language of the Republic/Empire is. If you watch a movie about the Roman Empire, you don't really expect all the dialog to be in Latin, do you? (;-)
"Elected" kings are a moderately common phenomenon in history. The Holy Roman Emperors of the Middle Ages were elected, for example, which I think may draw on an older Germanic tradition.
However, before people get all excited about this, such "elections" were restricted to the upper nobility: candidates only came from the top families (or in some cases, I think, from one extended family), and only the top nobles in the realm actually got to vote. Often, they would try to elect someone weak enough that he wouldn't interfere with the nobles' affairs and would allow them to manipulate him. (Some medieval Popes were elected for similar reasons.)
I have no idea what the situation is supposed to be on Naboo. The fact that Queen Amidala seems moderately competent at wearing her bizarre dresses, playing the formal "queen" role, and has a coterie of loyal handmaidens suggests to me that she's from a small pool of candidates trained from an early age with loyal servants -- in other words, a royal family. But I may be giving Lucas too much credit for sociological invention.
Although... why is Leia a "princess", anyway? If it's because Queen Amidala was her mother, it suggests some kind of hereditary monarchy on Naboo. (We don't have special titles for the children of Presidents, after all.)
D'oh --- forgot that Yoda's body did disappear as or just after he died, as several people have pointed out.
So I'm inclined to say the "disappearing Jedi" trick can only be pulled off (or only happens to) the most enlightened/advanced Jedi. Presumably, Qui-Gon wasn't quite at that stage yet; he didn't seem to be on the Jedi Council, for example. Vader had gone over to the Dark Side, so it doesn't surprise me that he (and Darth Maul and the Emperor) didn't vanish at death --- despite his redemption right at the end, he wasn't anywhere near as "holy" as Obi-Wan and Yoda were at the times of their deaths.
At this point, my two favorite theories for why Obi-Wan disappears at death and other Jedi don't are:
1.) Kenobi was sufficiently "holy" or "enlightened" or somesuch by the time of Episode IV, moreso than the other Jedi we've seen die (which doesn't necessarily explain Yoda's death...)
2.) Kenobi had a moment to prepare an unusual departure. There's the scene in Episode IV when Luke et al. are racing across the hanger for the Millenium Falcon, Luke sees the battle between Obi-Wan and Vader, and starts towards it. Obi-Wan sees this, presumably realizes that there's the danger of Luke confronting Vader before he's ready, and decides to sacrifice himself. So's there's that brief moment of Obi-Wan closing his eyes and lifting his saber out of guard position, allowing Vader to cut him through.
So is Obi-Wan just resigning himself to death (or whatever), or does he use that moment to "translate" himself into another state? (I've always wondered whether or not Obi-Wan vanished before Vader's saber cuts through...) In that case, Qui-Gon clearly didn't have time to set up his transition, if indeed he was sufficiently adept or "holy" to have done so; Darth Maul strikes too abruptly. And Yoda, for whatever reason, didn't see the need when he was dying.
What's the point of doing that? Maybe it lets Obi-Wan communicate with Luke more easily after "death", or maybe he just wanted to confuse and disturb Vader.
Not quite. Cherenkov radiation is the shock wave (of light) produced by something travelling faster than the *local* speed of light -- e.g., something moving 50 MPH through our Bose-Einstein condensate with a 38 MPH local lightspeed. It's analogous to the shock wave produced by a supersonic object (bullet, jet, etc.) moving through the atmosphere faster than the local sound speed. But the "superluminal" object is still limited to travelling slower than the *vacuum* speed of light (c). (I suppose a tachyon *could* produce Cherenkov radiation, but you don't need one.)
Experimental physicists use this effect in things like neutrino detectors, such the AMANDA detector at the South Pole: fast-moving subatomic particles created by interactions between neutrinos and atoms inside the earth go zipping through South Polar ice faster than the speed of light *inside ice*, creating a flash of Cherenkov radiation. If you have light detectors embedded in the ice, you can pick up the flash; if you have enough detectors and good clocks, you can track the flash moving through the ice and figure out which direction the particle came from, which tells you where in the universe the parent neutrino came from...
I suspect the original poster's idea *won't* work because it relies on getting light to travel faster than the local light speed, which by definition may not be possible...but I'm not up on my relativistic shock wave theory.
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Oh, dear. The "Roosevelt knew it was coming and deliberately did nothing" conspiracy argument. I'm afraid it's nowhere near as paranoid as you make it out to be. I suggest you try reading a serious history, like Gordon Prange's At Dawn We Slept, rather than conspiracy-theory nonsense.
Or read this exchange from the New York Review of Books Letters column, between Gore Vidal (a novelist who dabbles in conspiracy theory) and David Kahn (a serious historian who wrote, among other things, one of the definitive histories of cryptography):
http://www.nybooks.com/articles/14238
You could argue that the Japanese were "pushed" into a confrontation with the US, because the US cut off their supply of American oil in July, 1941, in response to Japanese troops moving into French Indochina. But only if you think that continued Japanese military expansion in China and Southeast Asia was somehow inevitable -- or justified.
The Japanese government could have their halted their expansion, of course; but they decided to continue. In order to do so, they needed access to oil, rubber, and other critical military supplies, so they planned to conquer Indonesia and Malaysia. In order to prevent the US from interfering in this expansion, they planned a series of attacks and invasions to knock out the US presence in the western Pacific and take out the US navy.
The Japanese were certainly not suckered into attacking Pearl Harbor; they carefully planned it, based in part on the earlier success of the British carrier aircraft in attacking the Italian naval base at Taranto in the Mediterranean (something the US ignored). Japanese military leaders started debating and planning war with the US in mid-1941; they had made the decision for war by the fall.
The US expected that a Japanese attack would most likely come in the Philippines; in part, they simply didn't think the Japanese capable of something as audacious and difficult as a long-range, carrier-based attack on Hawaii.
(Leaving aside all this, may I point out that if you are "suckering" someone into attacking you, you do this in order to ambush them when they make the attack, not let them go ahead and destroy most of your fleet?)
Actually, that's two defining events. First, Japan attacked Pearl Harbor and forced the US into war with Japan; second, Hitler declared war on the US a few days later (with Mussolini rather predictably following soon after). Why Hitler did this has never been entirely clear; the Axis agreement was a mutual defense treaty, so Germany was not obligated to join Japan if Japan attacked another country first.
So there's the possibility (perhaps not a very high one) that WWII could have remained split into unrelated Pacific/Asian and European sectors, with the US fighting Japan but not Germany.
RPG companies of the late 1970s in many ways parallel the dot-com industry in the 1990s.
Um, no, not really. What outside investors were bothering with gaming companies in the 1970s? The closest thing to booms (and attendant cash-flow problems) were probably White Wolf and Wizards of the Coast -- in the 1990s.
And Gygax was never "eaten" by TSR -- he was part of the original company, and ran it for a number of years. Original D&D was a TSR product right from the start.
Two reasons spring to mind:
1. Hubble was designed to be launched by the Shuttle; but the Shuttle is now supposed to be devoted to essentially nothing but International Space Station missions. Moreover, the cost of a Shuttle launch itself is of order $600 million. I'm not sure if the US has any unmanned rockets capable of launching the Hubble; even if we did, there would have to be at least some redesign costs to get the replacement Hubble to fit safely inside the rocket's nose and then deploy properly.
2. The de-orbiting module has to be attached to Hubble at some point anyway, otherwise there is the danger that when Hubble's orbit decays, it will strew bits of itself across populated areas. So you still have to send a robotic mission that can rendezvous and dock with Hubble, even if you're not attempting to repair and enhance it.
Briefly, there's ACS (Advanced Camera for Surveys), which does both optical and UV imaging; WFPC2 (Wide Field Planetary Camera 2), the older UV/optical imager; and NICMOS, which does near-infrared imaging. Both ACS and NICMOS also have spectroscopy modes, though they don't make up for what STIS does, or did.
Depending on what you're trying to look at, individual exposure times range from about a second to 30 minutes or so (longer than that, and you start getting too many cosmic ray hits that add noise to your data).
Planes usually aren't a problem; satellites (and meteors!) occasionally are. It depends on how big your field of view is (a degree across or just a few minutes of arc?) and how long you expose for.
An example from an observing program of mine: in a total of about 80 five-minute exposures of nearby galaxies, with a field of view about 0.1 degrees across, there were two exposures with satellite tracks on them. Annoying, but tolerable.
Actually... those are some seriously strange claims! Portuguese colonies in Greenland? Good "secret conspiracy-theory alternate history," not so good "real world" history.
Greenland was settled by Norse explorers in the Middle Ages (and of course earlier by various peoples from North America); the colony was cut off from Europe sometime in the late 1300s or early 1400s, and perished sometime in the 15th or 16th Century. The Portuguese were busy sailing down the coast of Africa and around into the Indian Ocean. They weren't going to Greenland!
(Now, had Columbus somehow ended up in Iceland, and somehow gotten someone to translate a few of the old pagan sagas, he might have deduced the existence of lands to the west. Lands with not much to offer except grapes and hostile natives, according to the sagas, so Columbus probably wouldn't have been too interested anyway.)
The reason Columbus insisted that China was close enough to be reached by contemporary sailing ships from Spain was because he simply got the distance wrong. As you mention, the radius of the earth had been accurately measured over a thousand years earlier, by the Alexandrian Greek Eratosthenes. He gave the earth's circumference in stadia, a common unit in Hellenistic times.
So how long is a "stadium"? Ah, there's the problem -- in late 15th Century Europe, they had recovered Eratosthenes' work, but not enough of the context, so they didn't really know. Columbus argued for a small value, which made the earth small and China not too far away. His academic opponents argued for a larger value, which would mean China was too far away. And, as we all know, Columbus was... well, wrong. His ships would have run out of food and water well before reaching China, but they luckily ran into the Americas on the way.
I think the idea was more to compare cathedrals and bazaars as functioning institutions, rather than in the sense of "how do you build them?" Cathedrals are organized, hierarchical entities, with scheduled ceremonies, committees, and managers (in a generic sense). You can't just walk in and suggest changes to a service or set up your own altar... Bazaars, on the other hand, *are* whover shows up and pitches a tent and tries to buy or sell, with no one trying to run the show and tightly regulate things. At least, that's the first-order comparison.
In fact, I think bazaars *do* require a certain amount of behind-the-scenes coordination: most historical Middle Eastern bazaars had officials who regulated weights and measures and prosecuted fraud, in addition to at least some kind of police presence to discourage thieves and robbers from taking whatever they wanted. And the actual construction of cathedrals involved a certain amount of community participation and contribution, from traveling artisans who helped spread Gothic style and techniques throughout Europe, to local citizens contributing their own labor and money to the building.
ESR's point, I think, was mainly to come up with some vivid metaphors to highlight the differences he perceived in software construction practices -- stately, organized, closed institution versus seemingly anarchic free-for-all -- rather than to make some historically [pedantically] accurate comparison. And maybe he had structures like the Cathedral of Cologne in mind, as well: begun in the Middle Ages and not actually finished until the 19th Century. Translated to computer timescales, that's at least a little like the slow progress of the GNU Hurd, or Windows NT 5, or...
-- Peter
Actually, we do see members of other species. One of the entertaining things about the Senate scene is seeing how many of the various species you can recognize from, e.g., the cantina scene in Episode IV. I'm pretty sure there's a small group of the walrus-faced guys (one of whom went after Luke and got cut down by Kenobi in the cantina scene), as well as the whatever-they-are's with three eyes. Probably some others I missed.
Re English as the universal language: well, I think you're supposed to take that as a convenient translation of whatever the "common" language of the Republic/Empire is. If you watch a movie about the Roman Empire, you don't really expect all the dialog to be in Latin, do you? (;-)
"Elected" kings are a moderately common phenomenon in history. The Holy Roman Emperors of the Middle Ages were elected, for example, which I think may draw on an older Germanic tradition.
However, before people get all excited about this, such "elections" were restricted to the upper nobility: candidates only came from the top families (or in some cases, I think, from one extended family), and only the top nobles in the realm actually got to vote. Often, they would try to elect someone weak enough that he wouldn't interfere with the nobles' affairs and would allow them to manipulate him. (Some medieval Popes were elected for similar reasons.)
I have no idea what the situation is supposed to be on Naboo. The fact that Queen Amidala seems moderately competent at wearing her bizarre dresses, playing the formal "queen" role, and has a coterie of loyal handmaidens suggests to me that she's from a small pool of candidates trained from an early age with loyal servants -- in other words, a royal family. But I may be giving Lucas too much credit for sociological invention.
Although... why is Leia a "princess", anyway? If it's because Queen Amidala was her mother, it suggests some kind of hereditary monarchy on Naboo. (We don't have special titles for the children of Presidents, after all.)
In reference to my previous "theories":
D'oh --- forgot that Yoda's body did disappear as or just after he died, as several people have pointed out.
So I'm inclined to say the "disappearing Jedi" trick can only be pulled off (or only happens to) the most enlightened/advanced Jedi. Presumably, Qui-Gon wasn't quite at that stage yet; he didn't seem to be on the Jedi Council, for example. Vader had gone over to the Dark Side, so it doesn't surprise me that he (and Darth Maul and the Emperor) didn't vanish at death --- despite his redemption right at the end, he wasn't anywhere near as "holy" as Obi-Wan and Yoda were at the times of their deaths.
-- Peter
At this point, my two favorite theories for why Obi-Wan disappears at death and other Jedi don't are:
1.) Kenobi was sufficiently "holy" or "enlightened" or somesuch by the time of Episode IV, moreso than the other Jedi we've seen die (which doesn't necessarily explain Yoda's death...)
2.) Kenobi had a moment to prepare an unusual departure. There's the scene in Episode IV when Luke et al. are racing across the hanger for the Millenium Falcon, Luke sees the battle between Obi-Wan and Vader, and starts towards it. Obi-Wan sees this, presumably realizes that there's the danger of Luke confronting Vader before he's ready, and decides to sacrifice himself. So's there's that brief moment of Obi-Wan closing his eyes and lifting his saber out of guard position, allowing Vader to cut him through.
So is Obi-Wan just resigning himself to death (or whatever), or does he use that moment to "translate" himself into another state? (I've always wondered whether or not Obi-Wan vanished before Vader's saber cuts through...) In that case, Qui-Gon clearly didn't have time to set up his transition, if indeed he was sufficiently adept or "holy" to have done so; Darth Maul strikes too abruptly. And Yoda, for whatever reason, didn't see the need when he was dying.
What's the point of doing that? Maybe it lets Obi-Wan communicate with Luke more easily after "death", or maybe he just wanted to confuse and disturb Vader.
-- Peter
Not quite. Cherenkov radiation is the shock wave (of light) produced by something travelling faster than the *local* speed of light -- e.g., something moving 50 MPH through our Bose-Einstein condensate with a 38 MPH local lightspeed. It's analogous to the shock wave produced by a supersonic object (bullet, jet, etc.) moving through the atmosphere faster than the local sound speed. But the "superluminal" object is still limited to travelling slower than the *vacuum* speed of light (c). (I suppose a tachyon *could* produce Cherenkov radiation, but you don't need one.)
Experimental physicists use this effect in things like neutrino detectors, such the AMANDA detector at the South Pole: fast-moving subatomic particles created by interactions between neutrinos and atoms inside the earth go zipping through South Polar ice faster than the speed of light *inside ice*, creating a flash of Cherenkov radiation. If you have light detectors embedded in the ice, you can pick up the flash; if you have enough detectors and good clocks, you can track the flash moving through the ice and figure out which direction the particle came from, which tells you where in the universe the parent neutrino came from...
I suspect the original poster's idea *won't* work because it relies on getting light to travel faster than the local light speed, which by definition may not be possible...but I'm not up on my relativistic shock wave theory.