I don't have statistics on this, but resubmitting after peer review is the standard way of doing things in my field (cosmology). That doesn't mean submitting the version that appears in the actual journal, with its formatting etc, but the version that passed the peer review, with all the reviewer's comments addressed.
As supporting evidence, here is the license of one of the most heavily used pieces of software in my field, camb:
You are licensed to use this software free of charge on condition that:
Any publication using results of the code must be submitted to arXiv at the same time as, or before, submitting to a journal. arXiv must be updated with a version equivalent to that accepted by the journal on journal acceptance.
If you identify any bugs you report them as soon as confirmed
Journals would not be in a position to try to fight this - nobody reads the journals, and everybody reads arXiv, so an attempt to prevent this would blow up in their face.
CO2 freezes at 78 C at a partial pressure of 1 atmosphere. That means that if the atmosphere were 100% CO2, and we were at sea level, but still at -93 C, then there would be CO2 snowing out of the atmosphere. However, the partial pressure of CO2 is much lower than 1 atmosphere simply because so little of the atmosphere is CO2. Since only 0.0397% of the air is CO2, and the local pressure (due to the high altitude) is about 0.65 atm, the partial pressure will be 2.6e-5 atmospheres. At that partial pressure the CO2 freezing temperature is less than -140 C (I couldn't find a diagram that went quite far enough down in pressure).
The physical reason for this is that there are two competing processes involved. CO2 molecules bumping into a solid speck of CO2 and getting stuck (freezing), and CO2 molecules shaking loose from a solid (sublimation). But the former process proceeds faster the more CO2 gas there is, i.e. the more often these collisions happen. Hence the dependence on the partial pressure.
The article lists Sweden among the countries where the years of health are going down, but when you look at the graph for individual countries, Sweden has a strong positive trend, and does not go down significantly in any year. Is that an error, or have I missed something?
On a side note, the article is confusing "Europe" with "The European Union". They aren't the same thing, especially when making statements like "Only the UK, Denmark and the Netherlands appear to have escaped". They didn't consider Iceland, Norway, Switzerland or any of the eastern european countries, for example. (Also, France is among those considered, and also doesn't seem to be declining).
Finally, the study is based on interview subjects' own perception of their health, and so might be affected by news reporing on health or other psychologial effects. But it is definitely an interesting result they've found.
I'm doing a postdoc right now, and while I don't mind the 60 hour weeks, the uncertainty is what gets at me. After a long education one basically becomes a vagabond, drifting from university to university, never knowing where one will be working in 3 years' time. And the last year of each postdoc is spent writing applications for other places. In my home country, there are 1-2 available permanent positions every decade or so in my field, each of which typically has more than 100 applicants from all over the world. Getting one of those is pretty unlikely, to put it mildly. So I'll have to choose between permanently moving far away from friends and family, or leave my field of research. Unless I'm better than all the 100+ other applicants.
The postdoc situation is a symptom of there beeing too little resources invested in science compared to the number of people who want to do science. Instead, society is investing resources in things like moving imagniary money around really fast (yes, high frequency trading and other finance is a big employer of drop-outs from my field - they can emply more people, and pay much higher salaries, despite their detrimental effect on society). Yes, I am a bit bitter.
This blog post by the same author as what I linked to above discusses LUX directly. It seems like theories will have to be pretty contrived to reconciliate the different experiments. So I guess the detections were just systematic errors after all.
Actually, it separated the hot gas in the galaxies from the stars and dark matter in the galaxies. Stars are so small compared to the distances between them that when galaxies collide, the stars just pass right through each other. The same applies to the dark matter (because it doesn't interact electromagnetically (or it would be visible), it does not experience any significant friction force). But the diffuse, hot gas collides and gets left behind in the collision. So you end up with dark matter and stars on each side of the collision point, and a huge amount of hot gas stuck in the middle. That gas is much heavier than the stars, so without dark matter, the gravitational field should be concentrated around the gas. But instead we see it (through gravitational lensing) to be concentrated around the stars (which is where we would expect the dark matter to be as explained above).
We know of some kinds of dark matter already: There is a huge amount of neutrinos left over from the big bang, and since these interact very weakly with other stuff, they definitely qualify as dark. Other known kinds of dark matter are black holes, and compact, cold objects made out of baryons (normal matter). So dark matter exists.
The problem is that there isn't enough of the normal kinds of dark matter. To match the pattern in the cosmic microwave background and the amount of hydrogen, helium and lithium in the universe, one needs by far most of the dark matter to be non-baryonic (i.e. not normal matter, but something like neutrinos, but heavier). This kind of dark matter is something we have to postulate exists in order to match observations. But when we do assume it exists, the theory matches observations extremely well. As an example, look at the CMB power spectrum as mesured by Planck. The error bars are so small that you mostly can't see them, and the points lie smack on top of the theory curve. But only if dark matter is included.
And it just so happens that the amount of dark matter that makes theory match the points in that graph also makes the element abundances, galaxy distribution, lensing observations and galaxy cluster velocities work too. Such a coincidence is pretty telling, I think.
But yes, people have tried to avoid dark matter by modifying gravity instead (though nowadays, the most common motivation for modifying graivty is to avoid dark energy). MOND is an example of that. MOND is like normal Newtonian gravity as long as the gravitational acceleration is large (like in the solar system), but instead of falling to arbitrarily low values as distances increase, the gravitational acceleration has an effective minimal value that it approaches as you move away. And such a constant value is just what you need to get the flat rotation curves we observe in galaxies. Which is the problem MOND was invented to solve.
MOND is an elegant solution for galaxies, but it loses all its elegance and predictive power when you try to apply it to the other areas where dark matter shows up. And in some cases it is plainly ruled out as an explanation. MOND, like Newtonian gravity, is a central force, which means that the force points towards the mass that generated it. But in the Bullet cluster, the gravitational force points towards areas with little visible matter, away from areas with much visible matter. This is impossible to fit into MOND. So the Bullet cluster basically killed MOND.
Some of MOND lives on in TeVES, which is an attempt at a relativistic version of MOND. Sadly TeVES has none of the simplicity and elegance of MOND, and while it can explai
Several different experiments have tried to measure dark matter directly in the lab, and the experimental situation is pretty confusing. This plot shows the confidence intervals and exclusion limits for various experiments (but it does not include LUX yet). The shaded regions are confidence intervals, that basically say "we've seen dark matter, and its properties lie somewhere in this region. But the dotted lines say "we haven't seen it, and if it exists, it can't lie above these lines".
What is strange, then, is that all of the detections are in regions that have been excluded by other experiements. LUX just makes the situation even more strained by pulling those upper bounds even lower. Still, those bounds and intervals depend on assumptions about the properties of dark matter, and it may be possible to reconcile the results.
It will be interesting to see what happens to those tentative detections when they get more data. My bet is that in the end some systematic effect will be found to be responsible for the apparent signal. Or (much less likely) that they were just flukes. But who knows?
Find the tidal forces over that 1.5 meters. It's not a whole lot. However you start to get into time dilation, again over 1.5 meters it isn't that much.
Really now. And how did you arrive at it not being "a whole lot"? Let's insert some numbers, shall we? The mass of the sun is about 2e30 kg. Its Schwartzschild radius is, as you say, 2950 km. The acceleration according to Newtonian gravity at that point is 1.5211095e13 m/s^2. 1.5 meters further out (that's a short astronaut, by the way), the acceleration is 1.5195660e13 m/s^2. The difference is 2.057e10 m/s^2. I.e. roughly 2 billion g. Most of us would find it hard to stay together under such tension, but I guess you're made of stronger stuff!
(Of course, Newtonian gravity doesn't work very well for such strong gravitational fields. But it's enough to tell you that you're in a lot of trouble.)
At times I've missed this from ArXiv too. Cosmocoffee is an arxiv overlay that sort of allows this, but such an approach is only effective is a significant fraction of arxiv users were too use it, which is not the case.
A few years ago (2010, iirc), a paper making a controversial claim was published on arxiv, and within one month three papers had appeared disputing that claim. During the next month, a counter-rebuttal was published, followed by counter-counter-rebuttals. In effect, a discussion was going on on arxiv in the form of articles. But scientific articles come with a pretty lage overhead, so perhaps it would be good to have some quicker way of commenting on an article than writing a full paper oneself.
Such a commenting system could be used to implement open, distributed peer review. Coupled with some sort of reputation system and meta-moderation, that would make make scientific journals obsolete (in my field, nobody reads journals (that happens on arxiv), and we only submit articles to them for peer review). Another positive consequence of this is that the discussion going into peer review, which is usually hidden, would be out in the open. Such discussions are usually quite informative, and it would also let people see if the review was fair or not.
While one may fear trolling etc., I think the answers and comments on stackoverflow is a good example of how a powerful reputation system can practically eliminate trolling and vacuous comments. So I think something like this would be doable. I hope PubMed's experiment works out.
Could you elaborate a bit on this? I had the impression that D-Wave's users had to map their problem to fit what D-Wave computes, not the other way around. That would make comparisons with a specialized software solver appropriate, wouldn't it?
The blog post in question also includes a link to the source code of the specialized solver (Prog-QAP), and others have confirmed that it produces the same results as CPLEX, the general solver that D-Wave beat.
CPLEX is indeed slower than D-Wave, though newer versions have brought the factor down from 3600x to 14x. But again, CPLEX is a general solver, while D-wave is specialized hardware. The specialized software solver Prog-QAP is *much* faster than CPLEX, and gets a 12000x speedup over D-Wave when running on a single core.
But all of that is a bit old, and it may be that D-Wave has produced more impressive results after that. I hope D-Wave's approach results in something able to beat classical computers, even if it doesn't lead to a general quantum computer. But I really dislike all the secrecy they employed - that is not how science is supposed to work. The fraud speculations they have had to endure are entierly self-inflicted due to this secrecy.
Here's direct link Ted's post. The most interesting points are (if I understand them correctly):
1. The insecurity discussed in the paper is about how quickly the Linux entropy pool recovers from a compromised state. I.e. imagine that somebody somehow gains full read access to your computer's memory, and reads your randomness pool (but kindly does not read all your private keys etc.), but then loses that access at some later pool. How long does it take until the entropy pool has recovered enough entropy to be usable again? I think in most cases one would already have lost at the time an attacker gained full read access to your system, and wouldn't worry much about what happens after that. So this is a pretty irrelevant issue.
2. The paper relies on the assumption that Linux stops collecting new entropy once it thinks the pool is sufficiently random. That hasn't been the case for quite some time - it now continues to mix in new entropy no matter how random it thinks the pool is.
I would not be very worried about this. And I think all the suggestions that people use hardware RNGs *instead* of/dev/random are misguided. While hardware RNGs are good in theory, and make a good input into/dev/random, they are, unlike the Linux source code, difficult to verify.
"Using the past to predict the future" is what we usually call "learning". Even goldfish and flies to it, and it has brought us all our science and technology. Why do people exit the door at the ground floor rather than windows 5 stories up? Because past experiences has taught us that things fall down, and that falling far is harmful. Why do you type words rather than random chains of letters? Because you predict from past data that people in the future will be able to read and understand them. Even the fact that lottery numbers are impossible to predict is a prediction about the future we make based on physical understanding (which we have learnt from data from the past) coupled with data about how the lottery process works.
You probably didn't mean to make as strong a statement as what you did but you basically said the single most anti-intellectual thing is is possible to say.
Lubos Motl is in this case arguing against a straw man. He starts by assuming you have an electron in a superposition of two states, and then goes on to prove that the expectation value of observing it in both states at the same time is zero. Nothing is controversial about that, and because interpretations of quantum mechanics are mathematically equivalent, they all predict that.
Many worlds has two ingredients: 1. Superpositions, which is a basic building block of quantum mechanics, and 2. not treating observers specially, not exempting them from entering into superpositions themselves.
The many worlds interpretation of his proof, where he valiantly destroys his straw-man, would say that after measuring the spin of the electron, the observer would be in an entangled superposition with the electron. Just like the electron is in a superposition of having spin up and down, the observer would enter a superposition of having observed spin up and having observed spin down. And because this is an entangled superposition, each version of the observer would keep getting the same result if he repeats his experiment. They would both see only a single spin no matter how many times the observe it - the probability each to observe two different spins is zero. This is the probability Motl computed in his straw-man proof. Ans it is perfectly consistent with many-worlds, and with any other interpretation of quantum mechanics. Since the only are interpretations, after all. The physics is in the math, which they all have in common.
Not necessarily. Wavefunction collapse is a part of some interpretations of quantum mechanics, such as the venerable Copenhagen interpretation, but many other popular interpretations do not include it. A prominent example of the latter is the many worldsuniversal wavefunction interpretation.
Interpretations of quantum mechanics are usually mathematically equivalent, which means that they make exactly the same physical predictions. So an experiment that would be a measurement of wavefunction collapse according to the Copenhagen interpretation would be a measurement of observer entanglement or similar in the many worlds interpretation, and something else in other interpretations. It's a bit like one theory saying that A=4/2 and another saying A=1*2. They agree on every prediction (A=2), and only differ in how they are formulated, and the intuition they give people.
Popular science reporting is usually very Copenhagen-heavy, but physicists are more mixed, and a large fraction of them would disagree that this experiment has measured wavefunction collapse (i.e. they will think it measured something else interesting).
As usual with physics articles, a non-paywalled version can be found at the arXiv. The intorduction is quite readable.
This is an interesting result, but this is very far away from realistic power generation. They do not mention the efficiency (or I missed it), and I think this isn't at the stage where one even cares much about it.
Orangutans: 275–500 cc (16.8–31 cu in)
Chimpanzees: 275–500 cc (16.8–31 cu in)
Gorillas: 340–752 cc (21–45.9 cu in)
Humans: 1,000–1,900 cc (61–120 cu in)
Neanderthals: 1,200–1,900 cc (73–120 cu in)
I think you're overestimating the orangutan brain size. It gets worse if you try to correct for body size using the encephalization quotient. You then get 7.4-7.8 for humans and 1.8 or so for orangutans.
Make that: "resulting in a total efficiency of less than 1% if I read the wikipedia article correctly". It seems one of my links went wrong, and ate some text at the same time.
When was the NIF project initiated? I found a "funding confirmation" in 1993, but not when the project itself was started. But if it was less than 5 years earlier, then ITER had a head start bureaucracy-wise.
NIF construction itself started in 1997, while ITER's started in 2008. So if you ignore the time spent on bureaucracy, NIF has had an 11 year head start. But I think the most interesting comparison is not planning time or construction time, but results/time after the facility opens. That will have to wait 7 more years, though.
What do you mean by ITER having a good head start? ITER is still a giant construction site! Here's what ITER currently looks like. Yes, it's that hole in the ground.
It would be interesting to read more details of NIL's achievement, though. For example whether this was breakeven using deuterium-tritium fuel, or whether they looked at their performance with less hazardous deuterium-deuterium fuel, and then extrapolated to performance with D-T. If the latter, then that has already been achieved by the japanese JT-60 tokamak in 1998. ITER is expected to reach 10 times breakeven with real D-T fuel, and be significantly net power positive.
The problem with inertial confinment using laser heating, as is used by NIL, is that not only is energy transfer from the lasers to the plasma inefficient, but much more importantly, generating the laser beams in the first place is extremely inefficient, resulting in a wikipedia article correctly. This makes inertial confinement fusion unlikely for energy production according to most people I've spoken to. It is useful for researching the behavior of high-energy plasmas though, which is useful for designing nuclear weapons.
Blocking on higher levels has some advantages too, though. For example blocking individual HTML elements. On facebook, I've needed this block facebook.com##div[class="ego_column"] to get rid of the last half of the advertisements. You're right that Adblock Plus sold out. That's why it was forked. I use the fork called Adblock Edge.
Slashdot Mirror
Oops, that was supposed to be "-78 C" and "2.6e-4 atmospheres".
Yes. I think you would end up with the balloon shrinking until all the CO2 has been converted into a small lump of dry ice.
I don't have statistics on this, but resubmitting after peer review is the standard way of doing things in my field (cosmology). That doesn't mean submitting the version that appears in the actual journal, with its formatting etc, but the version that passed the peer review, with all the reviewer's comments addressed.
As supporting evidence, here is the license of one of the most heavily used pieces of software in my field, camb:
You are licensed to use this software free of charge on condition that:
Any publication using results of the code must be submitted to arXiv at the same time as, or before, submitting to a journal. arXiv must be updated with a version equivalent to that accepted by the journal on journal acceptance.
If you identify any bugs you report them as soon as confirmed
Journals would not be in a position to try to fight this - nobody reads the journals, and everybody reads arXiv, so an attempt to prevent this would blow up in their face.
CO2 freezes at 78 C at a partial pressure of 1 atmosphere. That means that if the atmosphere were 100% CO2, and we were at sea level, but still at -93 C, then there would be CO2 snowing out of the atmosphere. However, the partial pressure of CO2 is much lower than 1 atmosphere simply because so little of the atmosphere is CO2. Since only 0.0397% of the air is CO2, and the local pressure (due to the high altitude) is about 0.65 atm, the partial pressure will be 2.6e-5 atmospheres. At that partial pressure the CO2 freezing temperature is less than -140 C (I couldn't find a diagram that went quite far enough down in pressure).
The physical reason for this is that there are two competing processes involved. CO2 molecules bumping into a solid speck of CO2 and getting stuck (freezing), and CO2 molecules shaking loose from a solid (sublimation). But the former process proceeds faster the more CO2 gas there is, i.e. the more often these collisions happen. Hence the dependence on the partial pressure.
The article lists Sweden among the countries where the years of health are going down, but when you look at the graph for individual countries, Sweden has a strong positive trend, and does not go down significantly in any year. Is that an error, or have I missed something?
On a side note, the article is confusing "Europe" with "The European Union". They aren't the same thing, especially when making statements like "Only the UK, Denmark and the Netherlands appear to have escaped". They didn't consider Iceland, Norway, Switzerland or any of the eastern european countries, for example. (Also, France is among those considered, and also doesn't seem to be declining).
Finally, the study is based on interview subjects' own perception of their health, and so might be affected by news reporing on health or other psychologial effects. But it is definitely an interesting result they've found.
Cosmology.
I'm doing a postdoc right now, and while I don't mind the 60 hour weeks, the uncertainty is what gets at me. After a long education one basically becomes a vagabond, drifting from university to university, never knowing where one will be working in 3 years' time. And the last year of each postdoc is spent writing applications for other places. In my home country, there are 1-2 available permanent positions every decade or so in my field, each of which typically has more than 100 applicants from all over the world. Getting one of those is pretty unlikely, to put it mildly. So I'll have to choose between permanently moving far away from friends and family, or leave my field of research. Unless I'm better than all the 100+ other applicants.
The postdoc situation is a symptom of there beeing too little resources invested in science compared to the number of people who want to do science. Instead, society is investing resources in things like moving imagniary money around really fast (yes, high frequency trading and other finance is a big employer of drop-outs from my field - they can emply more people, and pay much higher salaries, despite their detrimental effect on society). Yes, I am a bit bitter.
This blog post by the same author as what I linked to above discusses LUX directly. It seems like theories will have to be pretty contrived to reconciliate the different experiments. So I guess the detections were just systematic errors after all.
Actually, it separated the hot gas in the galaxies from the stars and dark matter in the galaxies. Stars are so small compared to the distances between them that when galaxies collide, the stars just pass right through each other. The same applies to the dark matter (because it doesn't interact electromagnetically (or it would be visible), it does not experience any significant friction force). But the diffuse, hot gas collides and gets left behind in the collision. So you end up with dark matter and stars on each side of the collision point, and a huge amount of hot gas stuck in the middle. That gas is much heavier than the stars, so without dark matter, the gravitational field should be concentrated around the gas. But instead we see it (through gravitational lensing) to be concentrated around the stars (which is where we would expect the dark matter to be as explained above).
The main lines of evidence for dark matter:
* Galactic rotation curves
* Velocity distribution in clusters of galaxies
* Gravitational lensing in general
* The Bullet Cluster in particular
* The pattern of positions of galaxies in the universe
* The pattern of Baryon-acoustic oscillations in the cosmic microwave background and in the galaxy distribution
* The primordial distribution of light elements in the universe
We know of some kinds of dark matter already: There is a huge amount of neutrinos left over from the big bang, and since these interact very weakly with other stuff, they definitely qualify as dark. Other known kinds of dark matter are black holes, and compact, cold objects made out of baryons (normal matter). So dark matter exists.
The problem is that there isn't enough of the normal kinds of dark matter. To match the pattern in the cosmic microwave background and the amount of hydrogen, helium and lithium in the universe, one needs by far most of the dark matter to be non-baryonic (i.e. not normal matter, but something like neutrinos, but heavier). This kind of dark matter is something we have to postulate exists in order to match observations. But when we do assume it exists, the theory matches observations extremely well. As an example, look at the CMB power spectrum as mesured by Planck. The error bars are so small that you mostly can't see them, and the points lie smack on top of the theory curve. But only if dark matter is included.
And it just so happens that the amount of dark matter that makes theory match the points in that graph also makes the element abundances, galaxy distribution, lensing observations and galaxy cluster velocities work too. Such a coincidence is pretty telling, I think.
But yes, people have tried to avoid dark matter by modifying gravity instead (though nowadays, the most common motivation for modifying graivty is to avoid dark energy). MOND is an example of that. MOND is like normal Newtonian gravity as long as the gravitational acceleration is large (like in the solar system), but instead of falling to arbitrarily low values as distances increase, the gravitational acceleration has an effective minimal value that it approaches as you move away. And such a constant value is just what you need to get the flat rotation curves we observe in galaxies. Which is the problem MOND was invented to solve.
MOND is an elegant solution for galaxies, but it loses all its elegance and predictive power when you try to apply it to the other areas where dark matter shows up. And in some cases it is plainly ruled out as an explanation. MOND, like Newtonian gravity, is a central force, which means that the force points towards the mass that generated it. But in the Bullet cluster, the gravitational force points towards areas with little visible matter, away from areas with much visible matter. This is impossible to fit into MOND. So the Bullet cluster basically killed MOND.
Some of MOND lives on in TeVES, which is an attempt at a relativistic version of MOND. Sadly TeVES has none of the simplicity and elegance of MOND, and while it can explai
Several different experiments have tried to measure dark matter directly in the lab, and the experimental situation is pretty confusing. This plot shows the confidence intervals and exclusion limits for various experiments (but it does not include LUX yet). The shaded regions are confidence intervals, that basically say "we've seen dark matter, and its properties lie somewhere in this region. But the dotted lines say "we haven't seen it, and if it exists, it can't lie above these lines".
What is strange, then, is that all of the detections are in regions that have been excluded by other experiements. LUX just makes the situation even more strained by pulling those upper bounds even lower. Still, those bounds and intervals depend on assumptions about the properties of dark matter, and it may be possible to reconcile the results.
It will be interesting to see what happens to those tentative detections when they get more data. My bet is that in the end some systematic effect will be found to be responsible for the apparent signal. Or (much less likely) that they were just flukes. But who knows?
Find the tidal forces over that 1.5 meters. It's not a whole lot. However you start to get into time dilation, again over 1.5 meters it isn't that much.
Really now. And how did you arrive at it not being "a whole lot"? Let's insert some numbers, shall we? The mass of the sun is about 2e30 kg. Its Schwartzschild radius is, as you say, 2950 km. The acceleration according to Newtonian gravity at that point is 1.5211095e13 m/s^2. 1.5 meters further out (that's a short astronaut, by the way), the acceleration is 1.5195660e13 m/s^2. The difference is 2.057e10 m/s^2. I.e. roughly 2 billion g. Most of us would find it hard to stay together under such tension, but I guess you're made of stronger stuff!
(Of course, Newtonian gravity doesn't work very well for such strong gravitational fields. But it's enough to tell you that you're in a lot of trouble.)
At times I've missed this from ArXiv too. Cosmocoffee is an arxiv overlay that sort of allows this, but such an approach is only effective is a significant fraction of arxiv users were too use it, which is not the case.
A few years ago (2010, iirc), a paper making a controversial claim was published on arxiv, and within one month three papers had appeared disputing that claim. During the next month, a counter-rebuttal was published, followed by counter-counter-rebuttals. In effect, a discussion was going on on arxiv in the form of articles. But scientific articles come with a pretty lage overhead, so perhaps it would be good to have some quicker way of commenting on an article than writing a full paper oneself.
Such a commenting system could be used to implement open, distributed peer review. Coupled with some sort of reputation system and meta-moderation, that would make make scientific journals obsolete (in my field, nobody reads journals (that happens on arxiv), and we only submit articles to them for peer review). Another positive consequence of this is that the discussion going into peer review, which is usually hidden, would be out in the open. Such discussions are usually quite informative, and it would also let people see if the review was fair or not.
While one may fear trolling etc., I think the answers and comments on stackoverflow is a good example of how a powerful reputation system can practically eliminate trolling and vacuous comments. So I think something like this would be doable. I hope PubMed's experiment works out.
Could you elaborate a bit on this? I had the impression that D-Wave's users had to map their problem to fit what D-Wave computes, not the other way around. That would make comparisons with a specialized software solver appropriate, wouldn't it?
The blog post in question also includes a link to the source code of the specialized solver (Prog-QAP), and others have confirmed that it produces the same results as CPLEX, the general solver that D-Wave beat.
CPLEX is indeed slower than D-Wave, though newer versions have brought the factor down from 3600x to 14x. But again, CPLEX is a general solver, while D-wave is specialized hardware. The specialized software solver Prog-QAP is *much* faster than CPLEX, and gets a 12000x speedup over D-Wave when running on a single core.
But all of that is a bit old, and it may be that D-Wave has produced more impressive results after that. I hope D-Wave's approach results in something able to beat classical computers, even if it doesn't lead to a general quantum computer. But I really dislike all the secrecy they employed - that is not how science is supposed to work. The fraud speculations they have had to endure are entierly self-inflicted due to this secrecy.
Here's direct link Ted's post. The most interesting points are (if I understand them correctly):
1. The insecurity discussed in the paper is about how quickly the Linux entropy pool recovers from a compromised state. I.e. imagine that somebody somehow gains full read access to your computer's memory, and reads your randomness pool (but kindly does not read all your private keys etc.), but then loses that access at some later pool. How long does it take until the entropy pool has recovered enough entropy to be usable again? I think in most cases one would already have lost at the time an attacker gained full read access to your system, and wouldn't worry much about what happens after that. So this is a pretty irrelevant issue.
2. The paper relies on the assumption that Linux stops collecting new entropy once it thinks the pool is sufficiently random. That hasn't been the case for quite some time - it now continues to mix in new entropy no matter how random it thinks the pool is.
I would not be very worried about this. And I think all the suggestions that people use hardware RNGs *instead* of /dev/random are misguided. While hardware RNGs are good in theory, and make a good input into /dev/random, they are, unlike the Linux source code, difficult to verify.
"Using the past to predict the future" is what we usually call "learning". Even goldfish and flies to it, and it has brought us all our science and technology. Why do people exit the door at the ground floor rather than windows 5 stories up? Because past experiences has taught us that things fall down, and that falling far is harmful. Why do you type words rather than random chains of letters? Because you predict from past data that people in the future will be able to read and understand them. Even the fact that lottery numbers are impossible to predict is a prediction about the future we make based on physical understanding (which we have learnt from data from the past) coupled with data about how the lottery process works.
You probably didn't mean to make as strong a statement as what you did but you basically said the single most anti-intellectual thing is is possible to say.
Lubos Motl is in this case arguing against a straw man. He starts by assuming you have an electron in a superposition of two states, and then goes on to prove that the expectation value of observing it in both states at the same time is zero. Nothing is controversial about that, and because interpretations of quantum mechanics are mathematically equivalent, they all predict that.
Many worlds has two ingredients: 1. Superpositions, which is a basic building block of quantum mechanics, and 2. not treating observers specially, not exempting them from entering into superpositions themselves.
The many worlds interpretation of his proof, where he valiantly destroys his straw-man, would say that after measuring the spin of the electron, the observer would be in an entangled superposition with the electron. Just like the electron is in a superposition of having spin up and down, the observer would enter a superposition of having observed spin up and having observed spin down. And because this is an entangled superposition, each version of the observer would keep getting the same result if he repeats his experiment. They would both see only a single spin no matter how many times the observe it - the probability each to observe two different spins is zero. This is the probability Motl computed in his straw-man proof. Ans it is perfectly consistent with many-worlds, and with any other interpretation of quantum mechanics. Since the only are interpretations, after all. The physics is in the math, which they all have in common.
That was supposed to be "... but physicists are more mixed."
Not necessarily. Wavefunction collapse is a part of some interpretations of quantum mechanics, such as the venerable Copenhagen interpretation, but many other popular interpretations do not include it. A prominent example of the latter is the many worlds universal wavefunction interpretation.
Interpretations of quantum mechanics are usually mathematically equivalent, which means that they make exactly the same physical predictions. So an experiment that would be a measurement of wavefunction collapse according to the Copenhagen interpretation would be a measurement of observer entanglement or similar in the many worlds interpretation, and something else in other interpretations. It's a bit like one theory saying that A=4/2 and another saying A=1*2. They agree on every prediction (A=2), and only differ in how they are formulated, and the intuition they give people.
Popular science reporting is usually very Copenhagen-heavy, but physicists are more mixed, and a large fraction of them would disagree that this experiment has measured wavefunction collapse (i.e. they will think it measured something else interesting).
As usual with physics articles, a non-paywalled version can be found at the arXiv. The intorduction is quite readable.
This is an interesting result, but this is very far away from realistic power generation. They do not mention the efficiency (or I missed it), and I think this isn't at the stage where one even cares much about it.
From this article:
Orangutans: 275–500 cc (16.8–31 cu in)
Chimpanzees: 275–500 cc (16.8–31 cu in)
Gorillas: 340–752 cc (21–45.9 cu in)
Humans: 1,000–1,900 cc (61–120 cu in)
Neanderthals: 1,200–1,900 cc (73–120 cu in)
I think you're overestimating the orangutan brain size. It gets worse if you try to correct for body size using the encephalization quotient. You then get 7.4-7.8 for humans and 1.8 or so for orangutans.
Make that: "resulting in a total efficiency of less than 1% if I read the wikipedia article correctly". It seems one of my links went wrong, and ate some text at the same time.
When was the NIF project initiated? I found a "funding confirmation" in 1993, but not when the project itself was started. But if it was less than 5 years earlier, then ITER had a head start bureaucracy-wise.
NIF construction itself started in 1997, while ITER's started in 2008. So if you ignore the time spent on bureaucracy, NIF has had an 11 year head start. But I think the most interesting comparison is not planning time or construction time, but results/time after the facility opens. That will have to wait 7 more years, though.
What do you mean by ITER having a good head start? ITER is still a giant construction site! Here's what ITER currently looks like. Yes, it's that hole in the ground.
It would be interesting to read more details of NIL's achievement, though. For example whether this was breakeven using deuterium-tritium fuel, or whether they looked at their performance with less hazardous deuterium-deuterium fuel, and then extrapolated to performance with D-T. If the latter, then that has already been achieved by the japanese JT-60 tokamak in 1998. ITER is expected to reach 10 times breakeven with real D-T fuel, and be significantly net power positive.
The problem with inertial confinment using laser heating, as is used by NIL, is that not only is energy transfer from the lasers to the plasma inefficient, but much more importantly, generating the laser beams in the first place is extremely inefficient, resulting in a wikipedia article correctly. This makes inertial confinement fusion unlikely for energy production according to most people I've spoken to. It is useful for researching the behavior of high-energy plasmas though, which is useful for designing nuclear weapons.
Blocking on higher levels has some advantages too, though. For example blocking individual HTML elements. On facebook, I've needed this block facebook.com##div[class="ego_column"] to get rid of the last half of the advertisements. You're right that Adblock Plus sold out. That's why it was forked. I use the fork called Adblock Edge.