This isn't accurate. Qubits don't in general give you exponential speed up. In particular, there's no known reduction of exponential time solvability to BQP (problems solvable on a quantum computer in polynomial time http://en.wikipedia.org/wiki/BQP ). The known speed ups generally are for things that are less than exponential. So for example, integer factoring is in BQP by Shor's algorithm http://en.wikipedia.org/wiki/Shor's_algorithm but the best known factoring algorithm is already subexponential. Most people who study the field believe that BQP does not contain EXP and moreover, most believe the even stronger statement that NP is not contained in BQP.
In general, the Fermi question is a serious concern. It is a concern not just for the deep implications it has but for the practical implications for our survival. In particular, it is possible that there's a lack of intelligent life out there because life finds ways to wipe itself out. Carl Sagan for example was worried that an explanation for the Fermi paradox was that species inevitably kill themselves with nuclear war before they get off their home planets. That particular worry seems less founded right now, but other worries, like exhaustion of resources, bad nanotech and others exist. Worse, if there is such a set of very risky technologies, they have to arise quickly so that species which encounter them don't generally have time to even anticipate the risk enough. Also, if this is a common problem then that means that it needs to arise soon in our future, say the next hundred years. That's because the technology has to arise in general before one stars spreading out to space. I suspect that intelligent life is rare due to the all the difficulties, not due to civilizations destroying themselves. But the possibility that self-elimination is the problem is deeply disturbing. More resources need to be put into dealing with existential risk.
Please stop blaming Israel for bad US policy in the Middle East. There have been multiple occasions now where the Israeli government has stepped in to tell Republicans in congress that cutting assistance the Palestinians is a bad idea. See for example http://www.nytimes.com/2011/09/21/world/middleeast/house-gop-finds-a-growing-bond-with-netanyahu.html?pagewanted=all. The current American positions in the Middle East are influenced by a variety of lobbyists but a large fraction of policy is guided by some members of congress being batshit insane. Not too surprisingly, when you get the likes of Michelle Bachmann on the Permanent Intelligence committee and you have senators like Inhofe and Demint on the senate Foreign Relations committee you are going to get really bad results. Many of these people have developed such a distorted combination of ideology and religion that they essentially think that anything which hurts or antagonizes Muslims must be a good thing. Israel has something to do with this, but when Obama needs to literally call the Israeli prime minister to explain to the Republicans that fucking over the Palestinians is a bad thing, you know the situation has gotten pretty crazy.
I'm not really impressed by either. Wolfram made some very good software but then wrote that wretched book which was primarily a mix of either wrong ideas or unoriginal ideas. There was a strong failure to credit the work others had done with cellular automaton. I couldn't tell if that was due to his ignorance or his general self-promotional tendencies.
As to the Lifeboat Foundation I lost minimal trust in them after they got in bed with Pam Geller http://lifeboat.com/ex/boards (yes, that's Pamela "Obama is a Muslim with a Fake Birth Certificate" Geller http://en.wikipedia.org/wiki/Pamela_Geller#Birther_views). If that weren't enough they've been involved in fear mongering about the LHC http://lifeboat.com/ex/particle.accelerator.shield. There are however other groups that are dealing with exisential risk threats in a serious and useful fashion. The Future of Humanity Institute http://www.fhi.ox.ac.uk/ which is affiliated with the University of Oxford, and headed by the very bright Nick Bostrom thinks about existential risk issues in general. Meanwhile, there are organizations focusing on specific concerns. For example, the B612 Foundation http://www.b612foundation.org/b612/ is focused on dealing with detecting and dealing with large asteroids. They have the advantage of also having a very clever name. Internet cookie to anyone who can figure out why they are called that without searching.
The Deep Ones have more powerful weapons and under the terms of the Benthic treaty we're not allowed to recover equipment from the ocean floor without their permission. They'd be extremely unlikely to give permission after the Jennifer-Morgue fiasco.
This is wrong. Both Judaism and Islam have similar notions of obeying the law of the land. Both also prefer if possible that disputes when it is legal be handled by their own courts. The relevant term for obeying the law of the land in Judaism is dina d'malchusa dina (aramaic for "the law of the land is the law"). Both Islam and Judaism have thus in much of the West solved this by making contracts with binding arbitration using their internal court systems.
usually pardons people after they have been sentenced
Note two things. First "usually" and second that he could just publicly ask the prosecutors not to prosecute. But he won't, because he clearly likes being able to exercise his discretion. So fuck him. Fuck the royal family, and fuck every single person who thinks that anyone is immune to criticism.
Re:Why so much disbelief in aliens among scientist
on
Exoplanet Count Tops 700
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· Score: 1, Interesting
That's not really good reason to believe they don't exist. A galactic spanning civilization, for one, would only be visible, as you say, across the galaxy.
That's not obviously the case. Largescale stellar engineering is something we might notice. Dyson Spheres and Ringworlds for example are both things that we'd be able to see in nearby galaxies. Similar remarks apply to other big engineering projects.
But anyway, I agree that it's likely that microbial life of various sorts is abundant. And on the other end, I've always felt that it is only a kind of cellular chauvinism that prevents us from thinking of stellar objects as life forms. They grow, they mantain homeostasis, they sometimes reproduce in a fashion, they consume, they die.
By this logic fire would be alive also. Stars don't seem to do much of the things that life does, in particular, stars don't reproduce in a way that makes stars more similar to themselves than not so (except in so far as high metal content supernova lead to even higher metalicity).
The Peloponnesian War was not the only thing that was relevant. Keep in mind that Thales was of all the ancient Greek thinkers very arguably the one who was closest to the scientific method (in terms of combining both empirical observation and rational thinking). And Thales was one of the first. So whatever prevented a scientific revolution it was probably more subtle than that.
Quantum entanglement doesn't work that way. Among other problems you can't use quantum entanglement to transmit information faster than the speed of light. You can use entangled particles as a shared source of randomness but that's a much weaker property. Also, entanglement in any useful form is a delicate issue, random particles won't just be entangled, and if things happen to get entangled it won't last for long.
Well, all known NP-complete problems have that sort of structure, but proving it is a strictly harder problem than proving P != NP (it is easily to see that it would force P !=NP but it doesn't seem possible from any obvious fashion to go in the other direction).
Do you have a citation for that? Note by the way that 28 isn't the next relevant number: Shor's algorithm assumes that a number is odd and not a perfect power (those are both easy to reduce to the case of not being in that situation) so the next number after 21 would be 35.
Er, apparently I'm somewhat wrong here. I thought that the nature of the groups involved in ECC were sufficiently different such that the basic idea of Shor's algorithm wouldn't work, but it looks like that's wrong. ECC encryption is vulnerable.
No. We don't know that factoring is not NP-complete. If for example P=NP then factoring would be NP complete (in a trivial sense). We can't even prove that P != NP implies factoring is not NP complete. We do know that if factoring were NP-complete then the polynomial hierarchy will collapse pretty badly but that's a reason to believe that it isn't NP-complete, not a proof.
In fact, the complexity is known to be less than O(2^n), though larger than O(n^a) for any value of a.
Again, strongly suspected but not known for the second part. Proving that factoring is not O(n^a) would in fact prove that P != NP in an extremely strong fashion.This result is strongly suspected but definitely not proven. If you could prove it you would have a straight shot at a Field's Medal.
15 has been factored using NMR machines which have been abandoned for most serious research precisely because they can't be scaled very well. There are other systems which are more scalable in theory but they haven't been successful so far as getting the minimum number of qbits needed to factor 15. (Also this isn't quite accurate in that you need slightly more than log_2 n qbits to factor n in the general case, but the basic point is sound.)
I wouldn't be surprised if in 20 years we can use a quantum computer to factor a number greater than 100. But that only requires a handful of functioning qbits. It is unlikely that the technology will be that advanced. There are however non-factoring based cryptosystems that are not as of yet known to be vulnerable to quantum computing. Unfortunately, we're a long way from proving that. The claim that there exists an encryption system which is not breakable by a quantum computer is a claim which is much harder than P != NP (you are in fact making a claim that us substantially stronger than NP not being a subset of BQP which many people aren't even sure they believe). In fact, even the existence of encryption secure against classical computers requires believing claims which imply P != NP. Moreover, if one starts implementing other encryption systems that aren't as widely studied as things like RSA one opens up the danger that those encryption systems have their own flaws as well.Also, at a practical level, there's very likely not going to be someone who is going to be recording all your RSS sessions on the offchance that they can decrypt them thirty years down the line. But if you really care then use one variant of elliptic curve cryptography. http://en.wikipedia.org/wiki/Elliptic_curve_cryptography. ECC systems are well-studied and have implementations. The people who study these sorts of things seem to think that ECC is one of the systems that is more likely to not be unable breakable by quantum systems.
For three-dimensions for a large object where the balls are small compared to the volume that contains them, a close approximation of Kepler's packing will be near optimal. http://en.wikipedia.org/wiki/Kepler's_conjecture. So one can assume that around 74% of the volume of the drum will be filled, and divide that by the volume of a golfball and you should get an answer that is correct within 5% or so. It will probably be a slight overestimate of how many you can fit in.
Not really. There are connected problems involving finding information about lattices that are in general NP-complete (in particular, given an explicit lattice in k dimensions, finding the shortest non-zero vector in the lattice is NP-complete. One needs to be careful here to turn this into a decision problem from a function problem but this is a technical detail. But those problems are in arbitrarily many dimensions and don't in any obvious way get easier when one can pack spheres efficiently. (Instead if one had efficient ways of solving those problems one could possibly pack spheres more efficiently. For low dimensions we can solve the lattice problem efficiently, and the general belief is that in high dimensions the best packings will not necessarily be lattice packings. There are a few other packing problems that are NP hard or NP complete (see e.g. http://dx.doi.org/10.1023/A:1009831621621 ) but this is a much more general problem. Moreover, it isn't at all clear that this procedure even gives much better asymptotic behavior for the narrow problem in question (although it probably does). So overall, this really doesn't impact P ?=NP issues much at all.
The error coding end of this sort of thing is farther from the sort of work I've done so I'm not sure I can answer the question in detail. It is the case certainly that in limited contexts where the packing is really easy to understand (like the packing one gets from the leech lattice) that they are actively used in code design. I don't know how much they are used for higher dimensional cases in practice, especially because one isn't generally getting much better than a simple lattice packing and the technical complexity can make practical implication difficult.
The summary doesn't mention one of the main reasons we care about sphere packing. If one is interested in error correcting codes then the best way of thinking about how many messages one can reliably send is a function of how efficiently you can pack sphere. The essential idea is that you think of your signal space as some large dimensional space, and you then consider your potential error to be the radius of the spheres. Then if you can find a decent packing of the spheres and you send as your messages the signals contained as the center of the spheres then you have a more efficient ability to send messages reliably with minimal chance of error. It seems that most of the work discussed in TFA is essentially for three dimensions only so this major reason people care about sphere packing (indeed probably the biggest reason) isn't that deeply connected.
In general sphere packing shows up in a lot of contexts and is pretty tough. For high dimensions we can't generally do much more than a random packing, although there are exceptions. For example, in 24 dimensions one has the very elegant Leech lattice http://en.wikipedia.org/wiki/Leech_lattice which allows a very regular, very efficient packing of spheres, and leads to the Golay code http://en.wikipedia.org/wiki/Binary_Golay_code which is a very efficient code for sending reliable signals and is not that hard to actually implement in practice since the math behind is straightforward.
One related issue is showing that a given type of sphere packing is the best possible. This turns out to be really, really tough. Kepler (yes, that Kepler, he did a lot.) famously conjectured that for spheres in three-dimensions the most efficient pacing was in general the obvious packing (the packing one sees with oranges in a grocery store). http://en.wikipedia.org/wiki/Kepler_conjecture. This problem wasn't solved until 1998, which made it for a long time one of the oldest unsolved problems in mathematics. Even just getting weak lower bounds is tough, especially in the higher dimensional case. The range between the upper and lower bounds is generally massive, because it is tricky to actually figure out good ways of fitting spheres together and it is really tricky to show that there isn't some clever way of getting more spheres in. (The earlier mentioned Leech lattice essentially works because it turns out that if one makes the essentially obvious lattice in 24 dimensions you can just manage to then slip a few more spheres in.) Last semester I was doing work related to what is called the Jordan-Schur theorem http://en.wikipedia.org/wiki/Jordan-Schur_Theorem, and it turned out that one might be able to improve some of the bounds if one had decent sphere packing lower bounds. Unfortunately, for my purposes none of the sphere packing results known were almost any better than just the naive volume estimates (that is, that you can't fit more little spheres into a region than you have volume). In high dimensions, things are just that bad.
TFA is actually talking about a special where you want to fit your spheres in a region of a specific shape, in this case, a cylinder. Things like this show up fairly frequently. In the case I was working with, one needed to fit the spheres around a larger sphere. Chan's result is quite interesting, although it looks to some extent like how well his type of packing works is empirical. The paper doesn't seem to be giving much in the way of direct upper bounds on how well the packing will work in general, although for many applied purposes his method should work well enough. I suspect that over the next few months people will be looking at his method, generalizing it, and trying to use it to establish explicit, non-computational, upper bounds.
66 billion in science dollars.
on
The F-35 Story
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· Score: 2
That's about 10 copies of the James Webb Telescope assuming absolutely worst case cost estimates. This is about fifteen times the cost that the Terrestrial Planet Finder would have been assuming it had been approved and then run over budget by a lot. It is about four times the cost of ITER, the next generation fusion reactor being built by an international consortium. It is about 1.5 human trips to Mars. It is about four times the maximal cost of the Superconducting Super Collider if it has been approved.Estimating the cost of the International Space Station is tough but this is clearly more than twice that cost. Most of these projects has been on the chopping block at one time. Two of these projects got axed and the Mars one never really got off the ground. This says something about our priorities and it isn't good.
Humans aren't little psychological weaklings. We've known this pretty well for a long time. In the 1500s sailors set out in small groups in difficult conditions (in many ways more difficult and cramped then a mission to Mars would be) for years at a time with zero communication with home. In contrast people on a Mars mission will have a higher chance of return and will be in constant communication with their friends and loved ones (aside from a few minutes of delay due to the speed of light) which makes things even easier. We don't need to wonder if human psychology lets us survive such circumstances. We already know they can. These experiments are not a good use of limited resources.
ne list still somewhat active is the discussion list for AOLserver, AOL's open-source Web server software. The administrator for this list moved it to SourceForge, where the AOLserver code is housed. However, the administrator, Dossy Shiobara, noted that there was no immediate way to move the decadelong archives of this mailing list, along with related announcement lists, to SourceForge. Fortunately, much of the content is mirrored on other sites, however.
Not all of the lists are going to have their archives mirrored. This is going to mean that a fair bit of internet history is going to get lost, and contribute a decent amount of linkrot in the process. While I suspect that most of that will just be inane flamewars, it always saddens me when data that could be preserved isn't preserved. I do hope that someone finds a way to move the archives of the various lists somewhere.
The simulation is pretty robust. When one part gets an error it just deletes that section of the simulation and resets it. It uses a lazy evaluation similar to Haskell so it can get away with this without turning off the whole simulation.
Slashdot Mirror
This isn't accurate. Qubits don't in general give you exponential speed up. In particular, there's no known reduction of exponential time solvability to BQP (problems solvable on a quantum computer in polynomial time http://en.wikipedia.org/wiki/BQP ). The known speed ups generally are for things that are less than exponential. So for example, integer factoring is in BQP by Shor's algorithm http://en.wikipedia.org/wiki/Shor's_algorithm but the best known factoring algorithm is already subexponential. Most people who study the field believe that BQP does not contain EXP and moreover, most believe the even stronger statement that NP is not contained in BQP.
There's recent evidence that a large moon to stabilize may not be necessary. See http://www.universetoday.com/91331/life-on-alien-planets-may-not-require-a-large-moon-after-all/ for a summary and http://www.sciencedirect.com/science/article/pii/S0019103511004064 for the actual paper. The issue is that while the lack of a moon will result in less stability in general the level of wobbling will be small and slow. There's also been in general growing evidence that habitable planets are more common than one might think otherwise. One recent study indicates that around a third of all sun-like stars have a planet in the habitable zone. http://blogs.discovermagazine.com/badastronomy/2011/09/29/new-study-13-of-sun-like-stars-might-have-terrestrial-planets-in-their-habitable-zones/ http://arxiv.org/PS_cache/arxiv/pdf/1109/1109.4682v1.pdf (keep in mind that being in the habitable zone is not sufficient for life. Our system has three planets in that zone, Earth, Mars and Venus, and only one of them supports complex life.) There's also been recent work which shows that for red dwarf stars there habitable zones are much larger than was previously expected (essentially water ice preferentially absorbs light from just the right wavelengths that red stars emit so that the outer zone is longer).
In general, the Fermi question is a serious concern. It is a concern not just for the deep implications it has but for the practical implications for our survival. In particular, it is possible that there's a lack of intelligent life out there because life finds ways to wipe itself out. Carl Sagan for example was worried that an explanation for the Fermi paradox was that species inevitably kill themselves with nuclear war before they get off their home planets. That particular worry seems less founded right now, but other worries, like exhaustion of resources, bad nanotech and others exist. Worse, if there is such a set of very risky technologies, they have to arise quickly so that species which encounter them don't generally have time to even anticipate the risk enough. Also, if this is a common problem then that means that it needs to arise soon in our future, say the next hundred years. That's because the technology has to arise in general before one stars spreading out to space. I suspect that intelligent life is rare due to the all the difficulties, not due to civilizations destroying themselves. But the possibility that self-elimination is the problem is deeply disturbing. More resources need to be put into dealing with existential risk.
Please stop blaming Israel for bad US policy in the Middle East. There have been multiple occasions now where the Israeli government has stepped in to tell Republicans in congress that cutting assistance the Palestinians is a bad idea. See for example http://www.nytimes.com/2011/09/21/world/middleeast/house-gop-finds-a-growing-bond-with-netanyahu.html?pagewanted=all. The current American positions in the Middle East are influenced by a variety of lobbyists but a large fraction of policy is guided by some members of congress being batshit insane. Not too surprisingly, when you get the likes of Michelle Bachmann on the Permanent Intelligence committee and you have senators like Inhofe and Demint on the senate Foreign Relations committee you are going to get really bad results. Many of these people have developed such a distorted combination of ideology and religion that they essentially think that anything which hurts or antagonizes Muslims must be a good thing. Israel has something to do with this, but when Obama needs to literally call the Israeli prime minister to explain to the Republicans that fucking over the Palestinians is a bad thing, you know the situation has gotten pretty crazy.
Nope! More clever than that... ROT 13 for spoiler: Vg vf gur qrfvtangvba bs gur nfgrebvq gung gur gvgyr punenpgre yvirf ba va Gur Yvggyr Cevapr.
I'm not really impressed by either. Wolfram made some very good software but then wrote that wretched book which was primarily a mix of either wrong ideas or unoriginal ideas. There was a strong failure to credit the work others had done with cellular automaton. I couldn't tell if that was due to his ignorance or his general self-promotional tendencies.
As to the Lifeboat Foundation I lost minimal trust in them after they got in bed with Pam Geller http://lifeboat.com/ex/boards (yes, that's Pamela "Obama is a Muslim with a Fake Birth Certificate" Geller http://en.wikipedia.org/wiki/Pamela_Geller#Birther_views). If that weren't enough they've been involved in fear mongering about the LHC http://lifeboat.com/ex/particle.accelerator.shield. There are however other groups that are dealing with exisential risk threats in a serious and useful fashion. The Future of Humanity Institute http://www.fhi.ox.ac.uk/ which is affiliated with the University of Oxford, and headed by the very bright Nick Bostrom thinks about existential risk issues in general. Meanwhile, there are organizations focusing on specific concerns. For example, the B612 Foundation http://www.b612foundation.org/b612/ is focused on dealing with detecting and dealing with large asteroids. They have the advantage of also having a very clever name. Internet cookie to anyone who can figure out why they are called that without searching.
The Deep Ones have more powerful weapons and under the terms of the Benthic treaty we're not allowed to recover equipment from the ocean floor without their permission. They'd be extremely unlikely to give permission after the Jennifer-Morgue fiasco.
This is wrong. Both Judaism and Islam have similar notions of obeying the law of the land. Both also prefer if possible that disputes when it is legal be handled by their own courts. The relevant term for obeying the law of the land in Judaism is dina d'malchusa dina (aramaic for "the law of the land is the law"). Both Islam and Judaism have thus in much of the West solved this by making contracts with binding arbitration using their internal court systems.
usually pardons people after they have been sentenced
Note two things. First "usually" and second that he could just publicly ask the prosecutors not to prosecute. But he won't, because he clearly likes being able to exercise his discretion. So fuck him. Fuck the royal family, and fuck every single person who thinks that anyone is immune to criticism.
That's not really good reason to believe they don't exist. A galactic spanning civilization, for one, would only be visible, as you say, across the galaxy.
That's not obviously the case. Largescale stellar engineering is something we might notice. Dyson Spheres and Ringworlds for example are both things that we'd be able to see in nearby galaxies. Similar remarks apply to other big engineering projects.
But anyway, I agree that it's likely that microbial life of various sorts is abundant. And on the other end, I've always felt that it is only a kind of cellular chauvinism that prevents us from thinking of stellar objects as life forms. They grow, they mantain homeostasis, they sometimes reproduce in a fashion, they consume, they die.
By this logic fire would be alive also. Stars don't seem to do much of the things that life does, in particular, stars don't reproduce in a way that makes stars more similar to themselves than not so (except in so far as high metal content supernova lead to even higher metalicity).
The Peloponnesian War was not the only thing that was relevant. Keep in mind that Thales was of all the ancient Greek thinkers very arguably the one who was closest to the scientific method (in terms of combining both empirical observation and rational thinking). And Thales was one of the first. So whatever prevented a scientific revolution it was probably more subtle than that.
Quantum entanglement doesn't work that way. Among other problems you can't use quantum entanglement to transmit information faster than the speed of light. You can use entangled particles as a shared source of randomness but that's a much weaker property. Also, entanglement in any useful form is a delicate issue, random particles won't just be entangled, and if things happen to get entangled it won't last for long.
Well, all known NP-complete problems have that sort of structure, but proving it is a strictly harder problem than proving P != NP (it is easily to see that it would force P !=NP but it doesn't seem possible from any obvious fashion to go in the other direction).
Do you have a citation for that? Note by the way that 28 isn't the next relevant number: Shor's algorithm assumes that a number is odd and not a perfect power (those are both easy to reduce to the case of not being in that situation) so the next number after 21 would be 35.
Er, apparently I'm somewhat wrong here. I thought that the nature of the groups involved in ECC were sufficiently different such that the basic idea of Shor's algorithm wouldn't work, but it looks like that's wrong. ECC encryption is vulnerable.
In fact, the complexity is known to be less than O(2^n), though larger than O(n^a) for any value of a.
Again, strongly suspected but not known for the second part. Proving that factoring is not O(n^a) would in fact prove that P != NP in an extremely strong fashion.This result is strongly suspected but definitely not proven. If you could prove it you would have a straight shot at a Field's Medal.
15 has been factored using NMR machines which have been abandoned for most serious research precisely because they can't be scaled very well. There are other systems which are more scalable in theory but they haven't been successful so far as getting the minimum number of qbits needed to factor 15. (Also this isn't quite accurate in that you need slightly more than log_2 n qbits to factor n in the general case, but the basic point is sound.)
I wouldn't be surprised if in 20 years we can use a quantum computer to factor a number greater than 100. But that only requires a handful of functioning qbits. It is unlikely that the technology will be that advanced. There are however non-factoring based cryptosystems that are not as of yet known to be vulnerable to quantum computing. Unfortunately, we're a long way from proving that. The claim that there exists an encryption system which is not breakable by a quantum computer is a claim which is much harder than P != NP (you are in fact making a claim that us substantially stronger than NP not being a subset of BQP which many people aren't even sure they believe). In fact, even the existence of encryption secure against classical computers requires believing claims which imply P != NP. Moreover, if one starts implementing other encryption systems that aren't as widely studied as things like RSA one opens up the danger that those encryption systems have their own flaws as well.Also, at a practical level, there's very likely not going to be someone who is going to be recording all your RSS sessions on the offchance that they can decrypt them thirty years down the line. But if you really care then use one variant of elliptic curve cryptography. http://en.wikipedia.org/wiki/Elliptic_curve_cryptography. ECC systems are well-studied and have implementations. The people who study these sorts of things seem to think that ECC is one of the systems that is more likely to not be unable breakable by quantum systems.
For three-dimensions for a large object where the balls are small compared to the volume that contains them, a close approximation of Kepler's packing will be near optimal. http://en.wikipedia.org/wiki/Kepler's_conjecture. So one can assume that around 74% of the volume of the drum will be filled, and divide that by the volume of a golfball and you should get an answer that is correct within 5% or so. It will probably be a slight overestimate of how many you can fit in.
Not really. There are connected problems involving finding information about lattices that are in general NP-complete (in particular, given an explicit lattice in k dimensions, finding the shortest non-zero vector in the lattice is NP-complete. One needs to be careful here to turn this into a decision problem from a function problem but this is a technical detail. But those problems are in arbitrarily many dimensions and don't in any obvious way get easier when one can pack spheres efficiently. (Instead if one had efficient ways of solving those problems one could possibly pack spheres more efficiently. For low dimensions we can solve the lattice problem efficiently, and the general belief is that in high dimensions the best packings will not necessarily be lattice packings. There are a few other packing problems that are NP hard or NP complete (see e.g. http://dx.doi.org/10.1023/A:1009831621621 ) but this is a much more general problem. Moreover, it isn't at all clear that this procedure even gives much better asymptotic behavior for the narrow problem in question (although it probably does). So overall, this really doesn't impact P ?=NP issues much at all.
The error coding end of this sort of thing is farther from the sort of work I've done so I'm not sure I can answer the question in detail. It is the case certainly that in limited contexts where the packing is really easy to understand (like the packing one gets from the leech lattice) that they are actively used in code design. I don't know how much they are used for higher dimensional cases in practice, especially because one isn't generally getting much better than a simple lattice packing and the technical complexity can make practical implication difficult.
The summary doesn't mention one of the main reasons we care about sphere packing. If one is interested in error correcting codes then the best way of thinking about how many messages one can reliably send is a function of how efficiently you can pack sphere. The essential idea is that you think of your signal space as some large dimensional space, and you then consider your potential error to be the radius of the spheres. Then if you can find a decent packing of the spheres and you send as your messages the signals contained as the center of the spheres then you have a more efficient ability to send messages reliably with minimal chance of error. It seems that most of the work discussed in TFA is essentially for three dimensions only so this major reason people care about sphere packing (indeed probably the biggest reason) isn't that deeply connected.
In general sphere packing shows up in a lot of contexts and is pretty tough. For high dimensions we can't generally do much more than a random packing, although there are exceptions. For example, in 24 dimensions one has the very elegant Leech lattice http://en.wikipedia.org/wiki/Leech_lattice which allows a very regular, very efficient packing of spheres, and leads to the Golay code http://en.wikipedia.org/wiki/Binary_Golay_code which is a very efficient code for sending reliable signals and is not that hard to actually implement in practice since the math behind is straightforward.
One related issue is showing that a given type of sphere packing is the best possible. This turns out to be really, really tough. Kepler (yes, that Kepler, he did a lot.) famously conjectured that for spheres in three-dimensions the most efficient pacing was in general the obvious packing (the packing one sees with oranges in a grocery store). http://en.wikipedia.org/wiki/Kepler_conjecture. This problem wasn't solved until 1998, which made it for a long time one of the oldest unsolved problems in mathematics. Even just getting weak lower bounds is tough, especially in the higher dimensional case. The range between the upper and lower bounds is generally massive, because it is tricky to actually figure out good ways of fitting spheres together and it is really tricky to show that there isn't some clever way of getting more spheres in. (The earlier mentioned Leech lattice essentially works because it turns out that if one makes the essentially obvious lattice in 24 dimensions you can just manage to then slip a few more spheres in.) Last semester I was doing work related to what is called the Jordan-Schur theorem http://en.wikipedia.org/wiki/Jordan-Schur_Theorem, and it turned out that one might be able to improve some of the bounds if one had decent sphere packing lower bounds. Unfortunately, for my purposes none of the sphere packing results known were almost any better than just the naive volume estimates (that is, that you can't fit more little spheres into a region than you have volume). In high dimensions, things are just that bad.
TFA is actually talking about a special where you want to fit your spheres in a region of a specific shape, in this case, a cylinder. Things like this show up fairly frequently. In the case I was working with, one needed to fit the spheres around a larger sphere. Chan's result is quite interesting, although it looks to some extent like how well his type of packing works is empirical. The paper doesn't seem to be giving much in the way of direct upper bounds on how well the packing will work in general, although for many applied purposes his method should work well enough. I suspect that over the next few months people will be looking at his method, generalizing it, and trying to use it to establish explicit, non-computational, upper bounds.
That's about 10 copies of the James Webb Telescope assuming absolutely worst case cost estimates. This is about fifteen times the cost that the Terrestrial Planet Finder would have been assuming it had been approved and then run over budget by a lot. It is about four times the cost of ITER, the next generation fusion reactor being built by an international consortium. It is about 1.5 human trips to Mars. It is about four times the maximal cost of the Superconducting Super Collider if it has been approved.Estimating the cost of the International Space Station is tough but this is clearly more than twice that cost. Most of these projects has been on the chopping block at one time. Two of these projects got axed and the Mars one never really got off the ground. This says something about our priorities and it isn't good.
Humans aren't little psychological weaklings. We've known this pretty well for a long time. In the 1500s sailors set out in small groups in difficult conditions (in many ways more difficult and cramped then a mission to Mars would be) for years at a time with zero communication with home. In contrast people on a Mars mission will have a higher chance of return and will be in constant communication with their friends and loved ones (aside from a few minutes of delay due to the speed of light) which makes things even easier. We don't need to wonder if human psychology lets us survive such circumstances. We already know they can. These experiments are not a good use of limited resources.
ne list still somewhat active is the discussion list for AOLserver, AOL's open-source Web server software. The administrator for this list moved it to SourceForge, where the AOLserver code is housed. However, the administrator, Dossy Shiobara, noted that there was no immediate way to move the decadelong archives of this mailing list, along with related announcement lists, to SourceForge. Fortunately, much of the content is mirrored on other sites, however.
Not all of the lists are going to have their archives mirrored. This is going to mean that a fair bit of internet history is going to get lost, and contribute a decent amount of linkrot in the process. While I suspect that most of that will just be inane flamewars, it always saddens me when data that could be preserved isn't preserved. I do hope that someone finds a way to move the archives of the various lists somewhere.
The simulation is pretty robust. When one part gets an error it just deletes that section of the simulation and resets it. It uses a lazy evaluation similar to Haskell so it can get away with this without turning off the whole simulation.