Most of the reason that EU GDP lags US GDP is that Europeans simply don't work such long hours. Eg GDP per capita in France (on a purchasing-power parity measure) $25K, compared to $35K for the US. But US workers put in 2000 hours per year each, rather than 1500 in France. So the actual productivity per worker in the US is only 5% ahead of French workers, whereas the GDP is 40% ahead.
You might consider European workers as being lazy. But having worked in both the US and the UK, I can tell you -- I prefer having a lower wage and 5 weeks holiday per year, than being paid more and only getting 2 weeks off.
This is nothing to do with charging people according to how quickly they wear out the roads. It's about charging people based on when and where they drive, in order to give them incentives to drive at less congested times, use less congested routes, or take public transport. The purpose is to reduce congestion and pollution, reduce journey times, and increase quality of life. That's why you can't do it with a gas tax.
You just don't get it. the road usage charge we are talking about IS NOT MEANT JUST TO COVER THE COST OF REPAIRING THE ROAD. It is meant to improve the quality of life.
In rural areas, traffic is not a problem. It may cause wear-and-tear on the tarmac, but it doesn't result in excessive pollution, noise, danger to pedestrians, delayed journeys. These are all factors which not only affect people living in cities, but cost the economy lots of money. (Billions of dollars in productivity are lost every year due to people & goods stuck in traffic.)
The money raised from these schemes should be ploughed back, not into roads, but into better public transport and local facilities so that people don't need to use cars so much. That way you create a virtuous circle reducing car use and improving quality of life.
I live in central London. Since the congestion charge started 6 months ago (five pounds to drive in central london during the working day), traffic outside my window has dropped dramatically. Noise is down. Pollution is down. The number of people getting run over is down. Money raised has been used to buy more buses and subsidise bus fares, so I can buy a day bus pass for less than half the price of the congestion charge, and be reasonably sure that the bus will arrive quickly and on schedule. That's the point.
In Europe, most freight is moved by train rather than by road, therefore it should have a very minor effect.
Moreover, if you'd been following the discussion you'd have seen that road usage charges are used to disincentive driving at peak times and on peak routes. Since most freight is moved at night, it would not be affected by a charge that only covers peak hours.
lower rural gas tax? That would result in city folks driving to the countryside to fill up their cars, which would make congestion WORSE.
What we're talking about here is differential road pricing to provide incentives for people to use less congested routes, or drive at less congested times. It's not a policy aimed at reducing car use per se (thought it may have that effect as well), but at redistributing car use.
It's no different from airlines charging more to travel at peak times than at slow times. Since road space is a finite resource, it makes sense to price it according to demand.
Regarding Britain and France's decision to come to the aid of Poland, not only was it after Hitler had already been prancing about Europe for a while taking what he pleased and doing as he wanted without any intervention (concentration camps, Rhineland, Sudetenland, Czechoslovakia), but also, it was due to Britain and France's poor conduct (sour winners) after the World War I towards Germany that created the condition which allowed Hitler to gain power.
Sure, Woodrow Wilson had nothing to do with negotiating the Treaty of Versailles (that ended the war). And the US senate had nothing to do with refusing to ratify the treaty because it also included the foundation of the League of Nations, which the Senate refused to join. And the lack of US involvement in the League of Nations was absolutely irrelevant to the League's ultimate failure to keep Hitler under control.
As for the U-boats in the Atlantic, the Americans at that point could have chosen to either retreat completely from the Atlantic (more plausible than it sounds) or they could have chosen to fight a solely naval war.
Now I know you are living in fantasy land. The US withdraw from the Atlantic at a time when it was still in the grip of the depression (which only ended because of the war), and when pacific trade was under threat from the Japanese? Genius! Exports would be cut to practically zero (not much demand in Mexico and Canada), unemployment would have soared even higher, there would probably have been a revolution.
Fight a purely naval war? A brilliant strategy. Why not just let the Germans overrun Britain and take over the Royal Navy -- then the world's largest fleet -- as well as exercising unchallenged control over the middle east and its oil supplies. Without British support India would have fallen to the Japanese (there was plenty of pro-Japanese sentiment among the Indian independence fighters) and German control over Africa would be virtually complete. So you're suggesting that the US would have been able to fight an effective naval war against the combined forces of three of the world's largest and most modern navies (German, British, Japanese) backed by the resources of almost all of Europe, Asia (China was already mostly under Japanese control) and Africa. Please, dream on. Once Germany declared war on the US, America's only option (apart from surrender) was to take the war to Germany.
The study of history is only of any use if it is done critically, with a view to the mistakes made by both sides. A view of history which paints the US as always being right inevitable leads to a distorted view of the past that feeds into a distorted view of the present.
And you didn't heed my sig. I never wrote that and you incorrectly assumed it.
You wrote that "most people" eat such foods with their fingers. To me that's the same as writing that you regard it as normal, since "normal" is pretty much defined as that which most people do. Are you suggesting that if you wrote "I ate a hamburger today", I would be wrong to assume or infer that you're not a vegetarian?
I merely gave fast-food examples that Joe Sixpack could relate to.
I'm touched by your concern that Joe Sixpack should be able to relate to your slashdot posts, though I doubt he's even heard of slashdot. But Joe Sixpack does not, never has and never will represent "most people" on this planet.
Most people eat brie or caviar (on crackers) with their fingers as well.
Well it's about time someone told Joe Sixpack to eat caviar from a mother-of-pearl spoon. Putting it on a cracker is a waste of caviar.
>>That would be essentially ridiculous, turning law from an ethical measure to a monetary one (well, more so).
In practical terms, that's exactly how it is.
Civil law operates by awarding damages to an amount that compensates your loss. (Punitive damages are an exceptional response to certain circumstances.) And if you don't have a claim for damages, then a judge isn't going to hear your case -- judges don't like being forced to spend days hearing a case simply in order to say "you were a bad boy!" at the end of it.
If you press a case and it turns out that you won on the law, but that you don't have a claim for damages, you'll most likely be awarded "nominal damages" -- a tiny figure like $1, but costs will be split so you'll still have a massive legal bill to pay. If the judge decides you were right on the law, but you never had a chance to claim damages and should have known it, he'll probably award costs against you.
You might think that there are very few cases where someone has broken the law but doesn't owe any damages, but in fact it's very common. Eg suppose I order a book from Amazon for $10, and it never arrives (and they never charge me). Clearly, Amazon are in breach of their contract, but the "damages" they owe me are the difference it price between what they charge and the book's market value. If they charge at or above the market value, they owe me no damages because I could have easily gone and bought the book somewhere else for the same price. (If however they're charging less than anyone else, then they owe me the difference.)
>>No need for that. You could accomplish the exact same thing with billions of one-time pad bits, through purely classical means.
If you had a 100% secure means of getting your pads to each other and making sure no-one copied them in transit or while they were in your posession, that would be true. The point about quantum methods is that they are tamper proof. It's impossible to copy my one-time pad without me knowing. Of course someone could steal it, but having discovered the theft of course I'd tell my correspondent to stop using that pad. In a quantum cryptographic system there's _no way_ to steal the key without being discovered. That's a pure mathematical proof based on the laws of quantum mechanics -- unless we've got the laws wrong, it truly is infallible.
>>Even in the quantum case you described, you'd need a corresponding classical message to make sense of the message.
I'm not sure what you mean here. In QC systems, most of the communication is always carried out over classical channels -- during key exchange each participant announces the measurement basis for evaluating their qubits, when the key is ready the message itself is sent classically. That's what makes it relatively practical -- most of the communication is classical. It's a strength, not a weakness.
That's not quite true; quantum cryptographic signals are not used to exchange messages, but only to guarantee a secure exchange of keys. These keys are then used to generate an unbreakable one-time pad encryption of the message, which can be broadcast publically without fear since only someone holding the key can decrypt it.
The one-time pad is one of the simplest encryption algorithms there are: you generate a random key as the same length as your message, then add the two together. You end up with something statistically indistinguishable from a random string of bits, which can only be decoded by someone who has the same key. The big drawback of the one-time pad is that somehow you have to get the recipient a copy of the key, which via non-quanum methods (eg a courier) are always open to interception.
Quantum key exchange uses entanglement to ensure that the sender and recipient can exchange keys, and be sure with arbitrary accuracy that no-one has intercepted the key -- because any attempt to intercept the key leaves a tell-tale sign. So it doesn't exactly prevent someone from stealing the key -- it just prevents them from doing so without you knowing.
It's true that at present this key exchange can only be done over a fibre-optic network, but there's no fundamental reason why it couldn't be done by other means. For example, when quantum computing becomes practical, it might be possible to use entangled qubits -- you and I could each have a "memory stick" of billions of entangled electron pairs, and when we wanted to exchange a message we'd just use up entangled pairs as needed.
Moreover because it's a key exchange, it could be possible to set up "key distribution centers", linked by fibre-optic networks. Then when we want to exchange a message, we first head down to our local centre and generate a key. Of course that's slightly less physically secure since maybe you'll be mugged on the way home, but it's stills secure against electronic eavesdropping. Even without such centres, it's obvious that many commercial establishments -- eg banks and stock exchanges -- could set up private fibre networks to guarantee secure data exchange.
However one shortcoming of current quantum crypto algorithms is that they're only useful for one-to-one communication -- you can't securely ditribute a key to many people. That's probably enough to make it useless for "common" online applications like filesharing -- but how important is truly unbreakable cryptography for that (as opposed to mere unbreakable-within-the-lifetime-of-the-universe) ?
My comment was intended as a joke (everyone eats with their fingers occasionally), but in fact you've just proved my point. You regard fast food, eaten with your fingers, as the norm. I regard it as the exception, to be done only when there's no alternative. You should get out of America more. There are some cultures where eating anything with your fingers is taboo - I remember being amazed seeing Chinese eat shell & eat a crab entirely using chopstick, when it would be far easier to use fingers.
I hope you realize that Pearl Harbour was solely a Japanese affair with no German involvement whatsoever. If anything, the fact that the Americans chose to fight a war on two fronts, one of which was not a direct threat to them, instead of focusing solely on the Pacific Theatre does nothing but strengthen my point.
There's no excuse for ignorance on this scale in the pot-Google era. Germany declared war on the US 4 days after Pearl Harbour. This meant that its U-Boats started torpedoing US ships in the Atlantic. Are you suggesting the US would have been willing to sit back and accept that?
But on your main point, that there was no German involvement in Pearl Harbour: Throughout 1941 Ribbentrop (Hitler's foreign minister) encouraged the Japanese government to attack the US. 10 days before Pearl Harbour he undertook that Germany would also declare war on the US if Japan attacked.
As for your emphasis on the nobility of the US's actions in deigning to take part in WWII at all, how about Britain and France's decision to come to the aid of Poland in 1939? Documents unearthed at Nuremburg clearly show that Hitler at first did not expect France and Britain to take seriously their pledge to defend Poland. Neither country had to declare war at all, and neither's interests were directly threatened.
Your story is refuted by the fact that the Russian program (which would have suffered none of the enivronmental concerns of the Boeing and Concorde efforts) failed as wel
Your logic is refuted by the fact that Concorde was in service for almost 30 years -- it carried its first passengers in 1976. The technical failures of the Russian project have no bearing on Concorde.
in fact the original poster has a good point. Concorde failed to flourish economically largely because the US authorities refused it permission to fly supersonically over the continental USA. That meant it was automatically excluded from the longer routes, such as London-LA, where the timne difference from supersonic speeds would have made a revolution in business travel possible.
Even on regular jets it's possible to make it to NY and back on business in 24hr (leave London 9am, arrive NY around 11am, afternoon meeting, leave NY 10pm, arrive London 9am...) Concorde's extra speed on that route is basically just adding convenience and glamour. But London-LA in 3 hours instead of 10 would revolutionise business travel between Europe and the west coast. That's what BA and Air France were counting on to make the numbers work. Another result of the FAA ban on supersonic travel was that US airlines, naturally, would never buy the airline.
So basically, the FAA ban on supersonic travel in the US meant that Concorde was barred from its most profitable routes, and so was unattractive to most airlines. That's why it never made any money, either for its makers or for BA and Air France. And there's little doubt that the FAA ban -- while partly based on genuine concerns about noise -- was also in part a response to protect the US aircraft industry.
It's just ironic that the long-term effects of this strategy were to kill of Boeing's Sonic Cruiser, which it had pinned its hopes on as the airplane to beat Airbus (the descendant of the consortium that built Concorde). As a result, Boeing is reduced to relying on the 747 -- first flown in 1969 -- to compete with Airbus's new superjumbo.
Of course the Russian and ESA rockets have the same effect, but if the story mentioned that it would have to be put on the "international" pages, and then no-one would read it...
That may be true if you're restricted to measuring voltage of electrical signals. But it has no bearing on optical processing.
In an optical processing, information can be encoded in the colour of the light. So rather than having laser on=1, laser off=0, a system could use red on=A, red off=B, blue on =C, blue off=D etc. Because it's optical, and optical signals don't interfere with each other, you don't need to worry about noise. Additionally there are now materials that can be used to modulate the frequency of light passing through them, which would allow the signal to be all-optical. With such a system being technologically feasible, it seems silly to restrict yourself to binary logic.
Don't by the recommended books, because they won't help. Seriously, unless the prof actually teaches straight out of the book (in which case, why take the class -- you can learn it by yourself), you shouldn't need them. Instead, listen in class and take good notes.
My experience (and I've had plenty in higher education) is that it's almost always more helpful to buy books NOT on the lecturer's list. Why? Because most lecturers recommend books that present things in the same way they teach them (ie they recommend the books they base their courses on). So if there's something you don't understand in class, a book won't help if it explains things in the same way.
As a maths/physics student I found the Dover series to be great. Cheap (under $10 a few years back), student-level texts by authors whose understanding of the subject far exceeds that of most lecturers. Schrodinger on quantum mechanics, Einstein on relativity, Fermi on thermodynamics, Lanczos on classical mechanics...They might not be of much direct help with problem sets, but they're great for giving insights into the subject. They do have a couple of drawbacks, though -- in some subjects they can be out of date (so you're safe with most maths and undergrad physics, not so good on genetics...). The other one is that they often assume quite a lot of knowledge about related subjects, which means you then have to buy another Dover book on that etc. But that's part of the fun.
Re:This idea is genius.
on
MIT Everyware
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actually, I did. Well OK, technically I was attending a little-known school at the other end of Mass Ave but I took MIT classes, had an MIT supervisor and an MIT office. You're right, MIT is not a normal school, but not because it's all about classes -- more because outside classes the students spend their time coding or in the machine shop building things.
Re:This idea is genius.
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MIT Everyware
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Don't be silly. People don't go to MIT to get an education. They go to drink beer and get laid...no, wait. That must have been some other college I was thinking of.
Oh yes, I remember now. They go to MIT in order to assemble police cars on the roof. Seriously, if you think college is all about classes, you missed out on your education.
>>If you've ever attended college and skipped a class, you should know there is absolutely no comparison between being in class and reading the notes on the web later.
If you live in the EU, don't just sign the petition - email your MEPs explaining why they should oppose the motion (and reminding them - gently - that they want your vote!). Yesterday I emailed all 10 MEPs representing London explaining my concerns, and I've already received 2 thoughtful responses -- one of which was seemed convinced by my arguments.
Probably the best arguments to use are those against patenting algorithmic business methods (also covered by the directive) rather than software per se, as they're more likely to be appreciated by politicians. My example was patenting an 'algorithm' that uses a number keyed in by a bank customer to verify their identity against the account details held on their bank card. Hey presto, your "software patent" gives you a monopoly on ATMs.
You can find a list of UK MEPs at the European Parliament's UK Office. For other countries, check out the main EU parliament website. Note that each constituency is represented by several MEPs, allocated between different parites by proportional representation. The vote on the directive is next week, so email your MEP today!
virtual photons are the quantum-field-theoretic explanation for the zero-point field. You get the zero-point energy from summing all the Feynman diagrams which have no incoming/outgoing particles - ie those consisting wholly of virtual particles. For the simple Casimir effect between two parallel plates, it's not necessary to invoke them in the calculation -- but that doesn't mean they're not there.
It's true that virtual particles used to be primarily considered to be a mathematical construct to aid calculation (and still are by some), but they're now generally accepted to be an accurate picture of reality. Eg Hawking radiation given off by a black hole is explained via the invocation of virtual particle pairs.
Many cornerstones of modern physics started off as mathematical construct introduced to aid calculations. Quantum mechanics itself is a good example -- Planck didn't believe that energy was quantised, he just found it was a good way of explaining the black-body radiation curve. It was only when Einstein explained the photoelectric effect by assuming that radiation could only exist as quantized photons that it was generally accepted this was the case. In the same year - 1905 - Einstein did the same thing for the constant speed of light and the existence of atoms. Until then neither concept was accepted as more than a convenient explanation for some odd experimental results -- he took them to assume reality, worked through the results, and gave us relativity and the theory of brownian motion.
the Casimir effect (a phenomenon that explains Max Planck's and Werner Heisenberg's quantum vacuum fluctuation theory)
Whoa there, you've got it all backwards. The Casimir effect is EXPLAINED BY quantum vacuum fluctuations, though the description of the effect in the original article is so bad that I can forgive your misunderstanding.
First, let's get the names right. It was Heisenberg and Schrodinger (not Planck) who came up with the first quantum theory to predict vacuum energy. However the idea of this energy coming from virtual particles (or "spontaneously appearing and disappearing particles and photons" as the article puts it) comes from Dirac's theory of quantum electrodynamics, as perfected by Feynman, Tomonaga and Schwinger. There's no independent "quantum vacuum fluctuation theory".
Second, let's have a closer look at the physics. The article gets the basic idea right: two parallel plates close together are pushed together because there are less virtual particles between the plates than outside them. The detail, though, is wrong - photons do not "pile up" outside the plates. It's much simpler than that. In an (infinite) vacuum, photons can exist with any wavelength. But between two plates, photons can only exist with wavelengths that are simple multiples of the distance between the plates -- just like vibrations on a finite string. (So it's not simply a case of only longer wavelenths being excluded--shorter ones are too, unless they're the right length) Both inside and outside, each permitted wavelength will on average be occupied by the same number of "virtual" photons caused by vacuum fluctuations. Because there are less wavelengths permissible between the plates than outside them, there's overall a greater energy density outside, which translates into a higher pressure.
The more perspicacious reader will have noted that there's an infinite number of possible wavelengths outside, and a (smaller) infinity of permitted wavelengths inside, with the difference between the two being infinite. Since each wavelength carries the same (finite) amount of vacuum energy, doesn't this mean that the energy density of the vacuum is infinite and that the force between the two plates is infinite... Well, yes and no. It depends what you mean by infinity:) Quantum theory is full of such unhelpful infinities -- it was working out how to get rid of them ("renormalisation") that won Feynman his Nobel prize.
One interested but little-known point about the Casimir effect is that it's not always attractive -- depending on the geometry of the components involved it can also be repulsive. However working out the result except in the most simple geometries is a VERY difficult problem...
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Most of the reason that EU GDP lags US GDP is that Europeans simply don't work such long hours. Eg GDP per capita in France (on a purchasing-power parity measure) $25K, compared to $35K for the US. But US workers put in 2000 hours per year each, rather than 1500 in France. So the actual productivity per worker in the US is only 5% ahead of French workers, whereas the GDP is 40% ahead.
You might consider European workers as being lazy. But having worked in both the US and the UK, I can tell you -- I prefer having a lower wage and 5 weeks holiday per year, than being paid more and only getting 2 weeks off.
This is nothing to do with charging people according to how quickly they wear out the roads. It's about charging people based on when and where they drive, in order to give them incentives to drive at less congested times, use less congested routes, or take public transport. The purpose is to reduce congestion and pollution, reduce journey times, and increase quality of life. That's why you can't do it with a gas tax.
You just don't get it. the road usage charge we are talking about IS NOT MEANT JUST TO COVER THE COST OF REPAIRING THE ROAD. It is meant to improve the quality of life.
In rural areas, traffic is not a problem. It may cause wear-and-tear on the tarmac, but it doesn't result in excessive pollution, noise, danger to pedestrians, delayed journeys. These are all factors which not only affect people living in cities, but cost the economy lots of money. (Billions of dollars in productivity are lost every year due to people & goods stuck in traffic.)
The money raised from these schemes should be ploughed back, not into roads, but into better public transport and local facilities so that people don't need to use cars so much. That way you create a virtuous circle reducing car use and improving quality of life.
I live in central London. Since the congestion charge started 6 months ago (five pounds to drive in central london during the working day), traffic outside my window has dropped dramatically. Noise is down. Pollution is down. The number of people getting run over is down. Money raised has been used to buy more buses and subsidise bus fares, so I can buy a day bus pass for less than half the price of the congestion charge, and be reasonably sure that the bus will arrive quickly and on schedule. That's the point.
In Europe, most freight is moved by train rather than by road, therefore it should have a very minor effect.
Moreover, if you'd been following the discussion you'd have seen that road usage charges are used to disincentive driving at peak times and on peak routes. Since most freight is moved at night, it would not be affected by a charge that only covers peak hours.
lower rural gas tax? That would result in city folks driving to the countryside to fill up their cars, which would make congestion WORSE.
What we're talking about here is differential road pricing to provide incentives for people to use less congested routes, or drive at less congested times. It's not a policy aimed at reducing car use per se (thought it may have that effect as well), but at redistributing car use.
It's no different from airlines charging more to travel at peak times than at slow times. Since road space is a finite resource, it makes sense to price it according to demand.
Regarding Britain and France's decision to come to the aid of Poland, not only was it after Hitler had already been prancing about Europe for a while taking what he pleased and doing as he wanted without any intervention (concentration camps, Rhineland, Sudetenland, Czechoslovakia), but also, it was due to Britain and France's poor conduct (sour winners) after the World War I towards Germany that created the condition which allowed Hitler to gain power.
Sure, Woodrow Wilson had nothing to do with negotiating the Treaty of Versailles (that ended the war). And the US senate had nothing to do with refusing to ratify the treaty because it also included the foundation of the League of Nations, which the Senate refused to join. And the lack of US involvement in the League of Nations was absolutely irrelevant to the League's ultimate failure to keep Hitler under control.
As for the U-boats in the Atlantic, the Americans at that point could have chosen to either retreat completely from the Atlantic (more plausible than it sounds) or they could have chosen to fight a solely naval war.
Now I know you are living in fantasy land. The US withdraw from the Atlantic at a time when it was still in the grip of the depression (which only ended because of the war), and when pacific trade was under threat from the Japanese? Genius! Exports would be cut to practically zero (not much demand in Mexico and Canada), unemployment would have soared even higher, there would probably have been a revolution.
Fight a purely naval war? A brilliant strategy. Why not just let the Germans overrun Britain and take over the Royal Navy -- then the world's largest fleet -- as well as exercising unchallenged control over the middle east and its oil supplies. Without British support India would have fallen to the Japanese (there was plenty of pro-Japanese sentiment among the Indian independence fighters) and German control over Africa would be virtually complete. So you're suggesting that the US would have been able to fight an effective naval war against the combined forces of three of the world's largest and most modern navies (German, British, Japanese) backed by the resources of almost all of Europe, Asia (China was already mostly under Japanese control) and Africa. Please, dream on. Once Germany declared war on the US, America's only option (apart from surrender) was to take the war to Germany.
The study of history is only of any use if it is done critically, with a view to the mistakes made by both sides. A view of history which paints the US as always being right inevitable leads to a distorted view of the past that feeds into a distorted view of the present.
And you didn't heed my sig. I never wrote that and you incorrectly assumed it.
You wrote that "most people" eat such foods with their fingers. To me that's the same as writing that you regard it as normal, since "normal" is pretty much defined as that which most people do. Are you suggesting that if you wrote "I ate a hamburger today", I would be wrong to assume or infer that you're not a vegetarian?
I merely gave fast-food examples that Joe Sixpack could relate to.
I'm touched by your concern that Joe Sixpack should be able to relate to your slashdot posts, though I doubt he's even heard of slashdot. But Joe Sixpack does not, never has and never will represent "most people" on this planet.
Most people eat brie or caviar (on crackers) with their fingers as well.
Well it's about time someone told Joe Sixpack to eat caviar from a mother-of-pearl spoon. Putting it on a cracker is a waste of caviar.
>>That would be essentially ridiculous, turning law from an ethical measure to a monetary one (well, more so).
In practical terms, that's exactly how it is.
Civil law operates by awarding damages to an amount that compensates your loss. (Punitive damages are an exceptional response to certain circumstances.) And if you don't have a claim for damages, then a judge isn't going to hear your case -- judges don't like being forced to spend days hearing a case simply in order to say "you were a bad boy!" at the end of it.
If you press a case and it turns out that you won on the law, but that you don't have a claim for damages, you'll most likely be awarded "nominal damages" -- a tiny figure like $1, but costs will be split so you'll still have a massive legal bill to pay. If the judge decides you were right on the law, but you never had a chance to claim damages and should have known it, he'll probably award costs against you.
You might think that there are very few cases where someone has broken the law but doesn't owe any damages, but in fact it's very common. Eg suppose I order a book from Amazon for $10, and it never arrives (and they never charge me). Clearly, Amazon are in breach of their contract, but the "damages" they owe me are the difference it price between what they charge and the book's market value. If they charge at or above the market value, they owe me no damages because I could have easily gone and bought the book somewhere else for the same price. (If however they're charging less than anyone else, then they owe me the difference.)
>>No need for that. You could accomplish the exact same thing with billions of one-time pad bits, through purely classical means.
If you had a 100% secure means of getting your pads to each other and making sure no-one copied them in transit or while they were in your posession, that would be true. The point about quantum methods is that they are tamper proof. It's impossible to copy my one-time pad without me knowing. Of course someone could steal it, but having discovered the theft of course I'd tell my correspondent to stop using that pad. In a quantum cryptographic system there's _no way_ to steal the key without being discovered. That's a pure mathematical proof based on the laws of quantum mechanics -- unless we've got the laws wrong, it truly is infallible.
>>Even in the quantum case you described, you'd need a corresponding classical message to make sense of the message.
I'm not sure what you mean here. In QC systems, most of the communication is always carried out over classical channels -- during key exchange each participant announces the measurement basis for evaluating their qubits, when the key is ready the message itself is sent classically. That's what makes it relatively practical -- most of the communication is classical. It's a strength, not a weakness.
That's not quite true; quantum cryptographic signals are not used to exchange messages, but only to guarantee a secure exchange of keys. These keys are then used to generate an unbreakable one-time pad encryption of the message, which can be broadcast publically without fear since only someone holding the key can decrypt it.
The one-time pad is one of the simplest encryption algorithms there are: you generate a random key as the same length as your message, then add the two together. You end up with something statistically indistinguishable from a random string of bits, which can only be decoded by someone who has the same key. The big drawback of the one-time pad is that somehow you have to get the recipient a copy of the key, which via non-quanum methods (eg a courier) are always open to interception.
Quantum key exchange uses entanglement to ensure that the sender and recipient can exchange keys, and be sure with arbitrary accuracy that no-one has intercepted the key -- because any attempt to intercept the key leaves a tell-tale sign. So it doesn't exactly prevent someone from stealing the key -- it just prevents them from doing so without you knowing.
It's true that at present this key exchange can only be done over a fibre-optic network, but there's no fundamental reason why it couldn't be done by other means. For example, when quantum computing becomes practical, it might be possible to use entangled qubits -- you and I could each have a "memory stick" of billions of entangled electron pairs, and when we wanted to exchange a message we'd just use up entangled pairs as needed.
Moreover because it's a key exchange, it could be possible to set up "key distribution centers", linked by fibre-optic networks. Then when we want to exchange a message, we first head down to our local centre and generate a key. Of course that's slightly less physically secure since maybe you'll be mugged on the way home, but it's stills secure against electronic eavesdropping. Even without such centres, it's obvious that many commercial establishments -- eg banks and stock exchanges -- could set up private fibre networks to guarantee secure data exchange.
However one shortcoming of current quantum crypto algorithms is that they're only useful for one-to-one communication -- you can't securely ditribute a key to many people. That's probably enough to make it useless for "common" online applications like filesharing -- but how important is truly unbreakable cryptography for that (as opposed to mere unbreakable-within-the-lifetime-of-the-universe) ?
My MP3 collection is too big to fit on my 30GB iPod
I wouldn't boast about that unless you want the RIAA knocking at your door...
My comment was intended as a joke (everyone eats with their fingers occasionally), but in fact you've just proved my point. You regard fast food, eaten with your fingers, as the norm. I regard it as the exception, to be done only when there's no alternative. You should get out of America more. There are some cultures where eating anything with your fingers is taboo - I remember being amazed seeing Chinese eat shell & eat a crab entirely using chopstick, when it would be far easier to use fingers.
>>You're really just eating everything that hands have touched.
I guess they haven't discovered cutlery in your part of the world yet
I hope you realize that Pearl Harbour was solely a Japanese affair with no German involvement whatsoever. If anything, the fact that the Americans chose to fight a war on two fronts, one of which was not a direct threat to them, instead of focusing solely on the Pacific Theatre does nothing but strengthen my point.
There's no excuse for ignorance on this scale in the pot-Google era. Germany declared war on the US 4 days after Pearl Harbour. This meant that its U-Boats started torpedoing US ships in the Atlantic. Are you suggesting the US would have been willing to sit back and accept that?
But on your main point, that there was no German involvement in Pearl Harbour: Throughout 1941 Ribbentrop (Hitler's foreign minister) encouraged the Japanese government to attack the US. 10 days before Pearl Harbour he undertook that Germany would also declare war on the US if Japan attacked.
As for your emphasis on the nobility of the US's actions in deigning to take part in WWII at all, how about Britain and France's decision to come to the aid of Poland in 1939? Documents unearthed at Nuremburg clearly show that Hitler at first did not expect France and Britain to take seriously their pledge to defend Poland. Neither country had to declare war at all, and neither's interests were directly threatened.
Your story is refuted by the fact that the Russian program (which would have suffered none of the enivronmental concerns of the Boeing and Concorde efforts) failed as wel
Your logic is refuted by the fact that Concorde was in service for almost 30 years -- it carried its first passengers in 1976. The technical failures of the Russian project have no bearing on Concorde.
in fact the original poster has a good point. Concorde failed to flourish economically largely because the US authorities refused it permission to fly supersonically over the continental USA. That meant it was automatically excluded from the longer routes, such as London-LA, where the timne difference from supersonic speeds would have made a revolution in business travel possible.
Even on regular jets it's possible to make it to NY and back on business in 24hr (leave London 9am, arrive NY around 11am, afternoon meeting, leave NY 10pm, arrive London 9am...) Concorde's extra speed on that route is basically just adding convenience and glamour. But London-LA in 3 hours instead of 10 would revolutionise business travel between Europe and the west coast. That's what BA and Air France were counting on to make the numbers work. Another result of the FAA ban on supersonic travel was that US airlines, naturally, would never buy the airline.
So basically, the FAA ban on supersonic travel in the US meant that Concorde was barred from its most profitable routes, and so was unattractive to most airlines. That's why it never made any money, either for its makers or for BA and Air France. And there's little doubt that the FAA ban -- while partly based on genuine concerns about noise -- was also in part a response to protect the US aircraft industry.
It's just ironic that the long-term effects of this strategy were to kill of Boeing's Sonic Cruiser, which it had pinned its hopes on as the airplane to beat Airbus (the descendant of the consortium that built Concorde). As a result, Boeing is reduced to relying on the 747 -- first flown in 1969 -- to compete with Airbus's new superjumbo.
Of course the Russian and ESA rockets have the same effect, but if the story mentioned that it would have to be put on the "international" pages, and then no-one would read it...
That may be true if you're restricted to measuring voltage of electrical signals. But it has no bearing on optical processing.
In an optical processing, information can be encoded in the colour of the light. So rather than having laser on=1, laser off=0, a system could use red on=A, red off=B, blue on =C, blue off=D etc. Because it's optical, and optical signals don't interfere with each other, you don't need to worry about noise. Additionally there are now materials that can be used to modulate the frequency of light passing through them, which would allow the signal to be all-optical. With such a system being technologically feasible, it seems silly to restrict yourself to binary logic.
Don't by the recommended books, because they won't help. Seriously, unless the prof actually teaches straight out of the book (in which case, why take the class -- you can learn it by yourself), you shouldn't need them. Instead, listen in class and take good notes.
My experience (and I've had plenty in higher education) is that it's almost always more helpful to buy books NOT on the lecturer's list. Why? Because most lecturers recommend books that present things in the same way they teach them (ie they recommend the books they base their courses on). So if there's something you don't understand in class, a book won't help if it explains things in the same way.
As a maths/physics student I found the Dover series to be great. Cheap (under $10 a few years back), student-level texts by authors whose understanding of the subject far exceeds that of most lecturers. Schrodinger on quantum mechanics, Einstein on relativity, Fermi on thermodynamics, Lanczos on classical mechanics...They might not be of much direct help with problem sets, but they're great for giving insights into the subject. They do have a couple of drawbacks, though -- in some subjects they can be out of date (so you're safe with most maths and undergrad physics, not so good on genetics...). The other one is that they often assume quite a lot of knowledge about related subjects, which means you then have to buy another Dover book on that etc. But that's part of the fun.
actually, I did. Well OK, technically I was attending a little-known school at the other end of Mass Ave but I took MIT classes, had an MIT supervisor and an MIT office. You're right, MIT is not a normal school, but not because it's all about classes -- more because outside classes the students spend their time coding or in the machine shop building things.
Don't be silly. People don't go to MIT to get an education. They go to drink beer and get laid...no, wait. That must have been some other college I was thinking of.
Oh yes, I remember now. They go to MIT in order to assemble police cars on the roof. Seriously, if you think college is all about classes, you missed out on your education.
>>If you've ever attended college and skipped a class, you should know there is absolutely no comparison between being in class and reading the notes on the web later.
You're right. That's why I never went to class.
If you live in the EU, don't just sign the petition - email your MEPs explaining why they should oppose the motion (and reminding them - gently - that they want your vote!). Yesterday I emailed all 10 MEPs representing London explaining my concerns, and I've already received 2 thoughtful responses -- one of which was seemed convinced by my arguments.
Probably the best arguments to use are those against patenting algorithmic business methods (also covered by the directive) rather than software per se, as they're more likely to be appreciated by politicians. My example was patenting an 'algorithm' that uses a number keyed in by a bank customer to verify their identity against the account details held on their bank card. Hey presto, your "software patent" gives you a monopoly on ATMs.
You can find a list of UK MEPs at the European Parliament's UK Office. For other countries, check out the main EU parliament website. Note that each constituency is represented by several MEPs, allocated between different parites by proportional representation. The vote on the directive is next week, so email your MEP today!
ll of the Roomba users seem to say that you have to do a manual clean every month
Since I only vacuum once a month anyway, doesn't look like a Roomba will save me any work...
virtual photons are the quantum-field-theoretic explanation for the zero-point field. You get the zero-point energy from summing all the Feynman diagrams which have no incoming/outgoing particles - ie those consisting wholly of virtual particles. For the simple Casimir effect between two parallel plates, it's not necessary to invoke them in the calculation -- but that doesn't mean they're not there.
It's true that virtual particles used to be primarily considered to be a mathematical construct to aid calculation (and still are by some), but they're now generally accepted to be an accurate picture of reality. Eg Hawking radiation given off by a black hole is explained via the invocation of virtual particle pairs.
Many cornerstones of modern physics started off as mathematical construct introduced to aid calculations. Quantum mechanics itself is a good example -- Planck didn't believe that energy was quantised, he just found it was a good way of explaining the black-body radiation curve. It was only when Einstein explained the photoelectric effect by assuming that radiation could only exist as quantized photons that it was generally accepted this was the case. In the same year - 1905 - Einstein did the same thing for the constant speed of light and the existence of atoms. Until then neither concept was accepted as more than a convenient explanation for some odd experimental results -- he took them to assume reality, worked through the results, and gave us relativity and the theory of brownian motion.
the Casimir effect (a phenomenon that explains Max Planck's and Werner Heisenberg's quantum vacuum fluctuation theory)
:) Quantum theory is full of such unhelpful infinities -- it was working out how to get rid of them ("renormalisation") that won Feynman his Nobel prize.
Whoa there, you've got it all backwards. The Casimir effect is EXPLAINED BY quantum vacuum fluctuations, though the description of the effect in the original article is so bad that I can forgive your misunderstanding.
First, let's get the names right. It was Heisenberg and Schrodinger (not Planck) who came up with the first quantum theory to predict vacuum energy. However the idea of this energy coming from virtual particles (or "spontaneously appearing and disappearing particles and photons" as the article puts it) comes from Dirac's theory of quantum electrodynamics, as perfected by Feynman, Tomonaga and Schwinger. There's no independent "quantum vacuum fluctuation theory".
Second, let's have a closer look at the physics. The article gets the basic idea right: two parallel plates close together are pushed together because there are less virtual particles between the plates than outside them. The detail, though, is wrong - photons do not "pile up" outside the plates. It's much simpler than that. In an (infinite) vacuum, photons can exist with any wavelength. But between two plates, photons can only exist with wavelengths that are simple multiples of the distance between the plates -- just like vibrations on a finite string. (So it's not simply a case of only longer wavelenths being excluded--shorter ones are too, unless they're the right length) Both inside and outside, each permitted wavelength will on average be occupied by the same number of "virtual" photons caused by vacuum fluctuations. Because there are less wavelengths permissible between the plates than outside them, there's overall a greater energy density outside, which translates into a higher pressure.
The more perspicacious reader will have noted that there's an infinite number of possible wavelengths outside, and a (smaller) infinity of permitted wavelengths inside, with the difference between the two being infinite. Since each wavelength carries the same (finite) amount of vacuum energy, doesn't this mean that the energy density of the vacuum is infinite and that the force between the two plates is infinite... Well, yes and no. It depends what you mean by infinity
One interested but little-known point about the Casimir effect is that it's not always attractive -- depending on the geometry of the components involved it can also be repulsive. However working out the result except in the most simple geometries is a VERY difficult problem...