The summary is completely incorrect. Whoever wrote the summary simply didn't understand the paper. String theory does not predict the production of microscopic black holes at LHC eneries. The paper's abstract says, "Limits on the minimum black hole mass are set, in the range 3.5 -- 4.5 TeV, for a variety of parameters in a model with large extra dimensions, along with model-independent limits on new physics in these final states." Note that phrase "large extra dimensions." Here is the WP article on large extra dimensions. String theory has *small* extra dimensions: extra dimensions that wrap around on themselves at the Planck scale. The LHC doesn't probe the Planck scale. Theories with large extra dimensions have, er, *large* extra dimensions. This experiment falsifies those theories, not string theory.
Two other markets are backpackers and boaters. However, people in those markets generally don't have a need to yak on the phone, they just have a need to be able to get help in an emergency. That's why PLB and SPOT exist. (But an awful lot of people misuse these systems as well, expecting to get helicoptered out of situations that they could have avoided or gotten themselves out of.)
Why, oh why can't people posting science stories on slashdot post links to the actual papers when they're publicly available? http://arxiv.org/abs/1008.2399
In May, Mozilla engineer Dan Witte proposed a mechanism that caused cookies to automatically expire when a user closed his or her Web browser. (By comparison, most tracking cookies last for years). It only affected tracking cookies—not cookies that websites use to remember users' passwords or shopping-cart information.
This is already pretty darn easy to accomplish in Firefox. Go it "Edit : Preferences : privacy." Uncheck "accept third-party cookies." Select "Keep until: I close Firefox." Under "exceptions," check "allow" for any sites that you frequently visit and want to stay logged in to between sessions.
I don't mind surrendering a little privacy to corporations if they're willing to pay for it. That's what I'm doing when I use the preferred customer mechanism at the supermarket. That's what I'm doing when I get a magazine subscription for much less than the newsstand price. The problem with online advertisers is that they shoot themselves in the foot with their unrealistic expectations. They expect me to give them my information without any economic reward. They expect me to tolerate animated ads that distract me from the text I'm trying to read. Given that their behavior is so unreasonable, I'm willing to take the time to install adblock plus and configure firefox to reject cookies that aren't on my whitelist.
Strictly speaking, he may be referring to a "structural isomer", but if so, it can only be defined in terms of other isomers, and further, it is a molecular distinction, not nuclear.
The term has different meanings in nuclear physics than in chemistry. In nuclear physics, it refers to an unusually long-lived excited state of the nucleus.
Right..... That sounds like a pretty political statement to me. Firstly, Amazon cannot say whether or not WikiLeaks controlled or had 'rights' to the content on there nor is it Amazon's place to judge whether it was putting anyone in jeopardy. Given that's almost the exact wording of the government 'enquiry' then the first statement seems grossly inaccurate. None of what Amazon says has been established legally.
Seems to me that you're barking up the wrong tree here. Amazon is a corporation, so it's legally considered a person in the U.S. Amazon has a legal right to make political statements under the first amendment. Freedom of speech does not mean that a third party like Amazon can be forced to provide a platform for the views of someone with whom they disagree. Amazon does not need to be able to prove that Wikileaks' activities are illegal. If Amazon decided it wanted to dump Wikileaks as a customer because they didn't like people named Julian, that would be their privilege. Whether or not Wikileaks is violating copyright is kind of a silly issue to be worrying about. IANAL, but my understanding is that under U.S. law, when you write something original and it's fixed in tangible form, you automatically own the copyright; however, works produced by the federal government are not copyrightable, although this doesn't apply, for example, to works produced by contractors. So there may or may not be copyrighted material in the Wikileaks documents, but if Amazon thinks there is, they're entitled to their opinion, and they're entitled to dump a customer for that reason -- even if they're wrong.
So let's be realistic here. The real issue is not whether we think Amazon should or should not have done this. The real issue is whether they were *pressured by the government* into doing this. If they were, then it's de facto censorship. Also, legality is not the same as morality. I approve morally of what Wikileaks has done. If it also happens to have been illegal under U.S. law, that has nothing to do with its morality.
For a long time, the famous Edgerton photos were a staple of physics textbooks. E.g., you could see the (huge) deformation of a tennis ball being hit by a racket. But the Edgerton images are all copyrighted, and it would be really helpful to have CC-BY-SA-compatible photos that could be used instead in places like Wikipedia. I'm the author of some copylefted physics textbooks, and I really haven't been able to find much that's useful. There's this category on wikimedia commons, but there's currently not much in it that's useful educationally. IMO there are a couple of things that would be useful in physics education: (1) an image like the tennis racket, showing how an object's center of mass accelerates even while it's in contact with another object; (2) an image like the bullet going through the apple, which I believe shows that the speed of sound in the apple is less than the speed of the bullet.
Of course, the downside is that reviews are going to have a negative tendency if at all possible.
Yeah, and although I hate putting money into the pockets of Amazon and E-Bay, this is the reason that they're really useful. They both try pretty hard to get buyers to rate sellers, and therefore you get a relatively unbiased set of ratings compared to what you'd get from the BBB, etc.
The solution to this seems pretty obvious to me. Don't blindly use search engines for shopping. Why in the world would anyone sane google for a product, go to that site, and enter a credit card number?
I buy my running shoes online, but I don't just google '"New Balance" 883 9-2E' and then go to the top hit and buy. I buy through Amazon, which shows me retailers that are willing to sell me those shoes and gives me users' ratings for the various retailers.
Granted, it's unfortunate that this has the effect of siphoning off revenue from mom-and-pop businesses to giant corporations like Amazon and E-Bay. But it reflects the fact that online reputation is hard to evaluate, and that Amazon and E-Bay are doing something useful by building up a database of online reputations.
In theory, I could do a couple of other things that would be better for small retailers. I could go to a local bricks and mortar store. Well, that sort of works, but unfortunately the local bricks and mortar stores don't stock shoes in the wide size I want to buy. I could also google small internet retailers, then try to evaluate their reputation by googling for their name, or by going to some online site that rates online reputation. The problem is that those methods of evaluating reputation aren't very reliable.
I gave a talk on this for students at my school recently. Penrose has a popular-level book out on the topic, which came out a few months before the publication of this claimed observation. The paper describing the observation is here. Here is a talk Penrose gave at Cambridge in 2005 on the topic.
If this is right, then it's certainly a huge discovery. There are at least two pretty big problems, however.
(1) Penrose's model requires some mechanism by which 100% of the massive particles in the universe get recycled into photons or other massless radiation. Black holes can do a lot of this, but there will inevitably be a few lonely hydrogen molecules that never fall into a black hole. Therefore one of the predictions of the model is that there is some novel particle physics going on. In the video of the 2005 talk, you can see that he posits the existence of charged particles lighter than an electron. Various particle physicists pointed out to him that this really isn't possible. (E.g., low-energy photons would interact with matter by pair production, and we observe that that doesn't happen.) By the time he published the popular book, he'd change this to a prediction that all massive particles simply lose their rest mass very, very slowly. This is disappointing, because it means he's stepped back from making testable predictions. "Very, very slowly" can be as slowly as you like, i.e., too slowly to measure, and therefore this aspect of the theory isn't falsifiable.
(2) The other problem is that it's not clear whether the claimed circular patterns are real. Penrose's co-author, the experimentalist on the new paper, is Gurzadyan. Gurzadyan got the WMAP and Boomerang collaborations to give him data. He is not part of those collaborations, but he has a ton of papers on CMB on arxiv, seems to be a heavy hitter in the field. The thing that makes me cautious is that the WMAP and Boomerang collaborations have not jumped on the bandwagon. If they really believed the statistical significance of the result, presumably they'd want their names on this extremely exciting result. Penrose's book also describes a grad student who worked on searching for such patterns in the data, and the book makes it sound like that search was inconclusive. If that grad student (and his advisor) believed in the patterns presently being claimed by Gurzadyan and Penrose, then there's no way in hell that this paper would go out without the grad student's name on them as a co-author; he definitely contributed to the work, and if he believed in the result, his name would be on there.
The whole bongo thing was just part of the media-created, mass-produced "beatnik" phenomenon. It was a trivialized and mass-marketed version of the Beat movement.
>From the photon's point of view they are simultaneous.
Here's a FAQ I wrote about that. The short answer is that there is no frame of reference that coincides with the motion of a photon.
FAQ: What does the world look like in a frame of reference moving at the speed of light?
This question has a long and honorable history. As a young student, Einstein tried to imagine what an electromagnetic wave would look like from the point of view of a motorcyclist riding alongside it. But we now know, thanks to Einstein himself, that it really doesn't make sense to talk about such observers.
The most straightforward argument is based on the positivist idea that concepts only mean something if you can define how to measure them operationally. If we accept this philosophical stance (which is by no means compatible with every concept we ever discuss in physics), then we need to be able to physically realize this frame in terms of an observer and measuring devices. But we can't. It would take an infinite amount of energy to accelerate Einstein and his motorcycle to the speed of light.
Since arguments from positivism can often kill off perfectly interesting and reasonable concepts, we might ask whether there are other reasons not to allow such frames. There are. One of the most basic geometrical ideas is intersection. In relativity, we expect that even if different observers disagree about many things, they agree about intersections of world-lines. Either the particles collided or they didn't. The arrow either hit the bull's-eye or it didn't. So although general relativity is far more permissive than Newtonian mechanics about changes of coordinates, there is a restriction that they should be smooth, one-to-one functions. If there was something like a Lorentz transformation for v=c, it wouldn't be one-to-one, so it wouldn't be mathematically compatible with the structure of relativity. (An easy way to see that it can't be one-to-one is that the length contraction would reduce a finite distance to a point.)
What if a system of interacting, massless particles was conscious, and could make observations? The argument given in the preceding paragraph proves that this isn't possible, but let's be more explicit. There are two possibilities. The velocity V of the system's center of mass either moves at c, or it doesn't. If V=c, then all the particles are moving along parallel lines, and therefore they aren't interacting, can't perform computations, and can't be conscious. (This is also consistent with the fact that the proper time s of a particle moving at c is constant, ds=0.) If V is less than c, then the observer's frame of reference isn't moving at c. Either way, we don't get an observer moving at c.
To all the inevitable pedantic responses about it not "really" happening 30 years old, I'll be even more pedantic.:) Relativity of Simultaneity, look it up. It's absolutely meaningless to talk of the temporal ordering of space-like separated events. In some suitable reference frame, it "really" did happen 30 years ago.
You've got that somewhat garbled. The relevant events would be (A) a photon is emitted from the star, and (B) that photon arrives here on earth. The relationship between A and B is lightlike, not spacelike. Since they are lightlike relative to one another, they do have a well-defined temporal ordering; there is no frame of reference in which B preceded A, or in which A and B are simultaneous. Your final sentence, however, is correct.
The big problem here is that language designers want their languages to get used.
There is a difference between telling your users that they *can* use unicode and telling them that they *have to*. Every language I can think of that said you *had to* use non-ASCII characters is dead: APL, Algol. I don't know about the detailed reasons why nobody actually codes in Algol (maybe just because it was mainly meant as a language for describing algorithms, not for writing practical programs), but APL's absurdly inconvenient character set was surely a reason that it expanded to fill a tiny niche and then quickly died even in that niche.
*Allowing* programmers to use non-ASCII characters is a lot more reasonable, but this is not exactly the world's biggest innovation. Perl allows you to use unicode characters inside string literals, but it also allows you to use, e.g., Chinese characters as names of variables. Is this a good thing? I guess so, in the sense that choice is good. But what happens when someone who doesn't speak Chinese wants to maintain code that uses Chinese variable names? Sure, we shouldn't be cultural chauvinists, but realistically, every literate Chinese person can recognize the letters of the Latin alphabet, whereas the converse isn't true -- coders in New York or Mumbai can't read Chinese characters.
There is also a nontrivial issue of look-alike characters, which could be a source of errors. For example, do I really want to be able to have one variable named Y (upper-case Latin Y) and another named Y (upper-case Greek upsilon)?
Countries like the UK and Israel have experience with terrorism, and they've developed reasonably sane ways of handling it. Just to be clear, I'm not praising the fact that they stole land from the Irish and the Palestinians -- but at least they don't act like total idiots when someone sets off a bomb. The US, on the other hand, responded to 9/11 by running around like a chicken with its head cut off. We shot ourselves in the foot in ways that were far worse than any of the damage done by the 9/11 hijackers, including two wars and an all-out assault on our own civil liberties. Compared to that kind of national self-mutilation, I can't really take it too seriously when I'm not allowed to bring a full-size shampoo bottle on an airplane -- but it certainly is an example of the same idiocy, just on a smaller scale.
The irony of this proposal is that many professors, realizing that book prices are just obscene in the academic market, are preparing their own materials and giving them to the students for the cost of printing them.
Yep. I'm a community college physics teacher. I wrote my own book, and it's free online. Under the model being discussed in TFA, my students' minimum cost would go up from $0 to $35.
The whole reason that the current model sucks is that professors have only a very weak motivation to consider cost when selecting a textbook. Even if they are motivated enough to use price as a criterion, selecting a text is a weak lever, because all the choices from the big publishers are roughly equally overpriced. This proposal would make that *worse*, not better. Professors would go from having weak leverage on price to having none at all. Publishers would extort higher and higher fees every year. Professors would no longer get gratitude from students for putting books online for free, because students would be paying a fixed tax anyway.
This is all about eliminating students' options. No more option to buy a used book, check out a book from a library, borrow the book from a friend who took the course, or use an older edition.
In fact, in America, you don't even really own the land. You only own the house and other "improvement" ON the land. You rent your land from the government for which you pay annual rent in the form of Property Tax (this is the feudal relationship between Lord and Sovereign that we fought a revolution to get away from, and we're right back there now).
Oh, please.
In feudalism, serfdom was hereditary, and serfs were tied to the land. There is no analog of this in the present-day U.S.
In feudalism, there were mutual obligations between the lord and his serfs. Basically, the serfs had to work the land and give the lord some of what the land produced, and in return the lord had to give military protection from other lords. The U.S. Revolutionary War was essentially fought because the feudal lord (George III) was trying to make a one-sided version of the feudal relationship. He wanted the colonists to have an obligation to him (pay taxes), but they weren't getting anything from him (no military protection from the Indians, for example).
Allodial title doesn't mean immunity from taxes. It means ownership of land without being subject to feudal obligations. Taxes are not a feudal obligation.
I'm not sure what you're on, but reading narrow columns is way faster than reading wide lines. That's why newspapers have columns. One of the many deficiencies of CSS is that it's practically impossible to a newspaper-like layout which works at any screen size (adapting the number of columns as needed).
I don't think this is quite right. Newspapers are optimized for fitting the maximum number of words in a given area. They sacrifice readability for this in a variety of ways, such as leaving out the comma before an "and," and using narrow columns that force a lot of hyphenation.
I think there is an optimum line length for readability, and it's (not surprisingly) somewhere around the width of a page in a typical paperback or hardcover book. Anything much narrower or much wider reduces readability.
What kind of work are you trying to do? Your post asks about pointing devices, but if you're word-processing or coding, reconsider whether you even need a pointing device. Most of my computer work is word-processing or coding, i.e., just typing characters. I used to use mouse-based editors and word-processors, and my RSI problems were all related to my pointing device -- every time I would reach for the mouse, that's when it would hurt. Since you're asking about pointing devices, it sounds like you also have a problem with pointing devices. So if your work consists of typing characters, just stop using a pointing device. Use an editor such as emacs (good) or vi (evil) that can be controlled without a pointing device. (YMMV as far as good or evil. If God damns you to hell for using vi, I am not responsible. I am not a lawyer or a priest, and this is not legal or religious advice.)
For the LHC to create black holes at all would require a whole bunch of very speculative physics to be true, and a whole bunch of very well-established physics to be false.
No, this is incorrect. All it requires is for one very speculative piece of physics to be true: large extra dimensions.
In particular, if the LHC can create black holes then millions of black holes are being created every day by cosmic rays, which can have twenty orders of magnitude more energy than the LHC. No evidence of those black holes is seen anywhere, not in geochemical track analysis, not in the radiation signature of cosmic ray showers, no where. Ergo, either such black holes are not being created, or they are being destroyed with incredible rapidity.
If the only modification to the standard model is large extra dimensions, then it's just like any other particle physics experiment, where decay rates are closely related to formation rates. The black holes decay essentially instantaneously. That is why theories with large extra dimensions are not immediately falsified by the lack of geological evidence, or by the fact that we don't observe white dwarfs and neutron stars being destroyed by cosmic ray impacts.
For the beam dump of the LHC to behave any differently would require physics so arcane as to be basically magic, and anyone who is worried about it should also be terrified that a herd of flying elephants will trample them to death, because that's a far more probable event.
To be *worried* about black hole production at the LHC, i.e., to think that it might be dangerous, is a whole different matter. Your criticisms above are all valid criticisms if someone is saying that the black holes might be produced and not immediately evaporate. That requires some very strange nonstandard physics. Here are some papers on the topic: http://arxiv.org/abs/hep-ph/0402168http://arxiv.org/abs/0808.4087
FAQ: Do rates of nuclear decay depend on environmental factors?
There is one environmental effect that has been scientifically well established for a long time. In the process of electron capture, a proton in the nucleus combines with an inner-shell electron to produce a neutron and a neutrino. This effect does depend on the electronic environment, and in particular, the process cannot happen if the atom is completely ionized.
Other claims of environmental effects on decay rates are crank science, often quoted by creationists in their attempts to discredit evolutionary and geological time scales.
He et al. (He 2007) claim to have detected a change in rates of beta decay of as much as 11% when samples are rotated in a centrifuge, and say that the effect varies asymmetrically with clockwise and counterclockwise rotation. He believes that there is a mysterious energy field that has both biological and nuclear effects, and that it relates to circadian rhythms. The nuclear effects were not observed when the experimental conditions were reproduced by Ding et al.
Jenkins and Fischbach (2008) claim to have observed effects on alpha decay rates at the 10^-3 level, correlated with an influence from the sun. They proposed that their results could be tested more dramatically by looking for changes in the rate of alpha decay in radioisotope thermoelectric generators aboard space probes. Such an effect turned out not to exist (Cooper 2009). Undeterred by their theory's failure to pass their own proposed test, they have gone on to publish even kookier ideas, such as a neutrino-mediated effect from solar flares, even though solar flares are a surface phenomenon, whereas neutrinos come from the sun's core. An independent study found no such link between flares and decay rates (Parkhomov 2010). Jenkins and Fischbach's latest claims, in 2010, are based on experiments done decades ago by other people, so that Jenkins and Fischbach have no first-hand way of investigating possible sources of systematic error. Laboratory experiments[Lindstrom 2010] have also placed limits on the sensitivity of radioactive decay to neutron flux that rule out a neutrino-mediated effect at a level orders of magnitude less than what would be required in order to explain the variations claimed in [Jenkins 2008].
Cardone et al. claim to have observed variations in the rate of alpha decay of thorium induced by 20 kHz ultrasound, and claim that this alpha decay occurs without the emission of gamma rays. Ericsson et al. have pointed out multiple severe problems with Cardone's experiments.
I partially disagree. Memorization has its place in learning. For example, if one is taking a proper mathematical analysis class but they do not know (by heart!) the formal definition of the limit by midterm, then one is left to wonder how much actual analysis they can do. Ditto for Newton's laws of motion, for example, in the corresponding physics class.
Hi -- I'm the OP. I can't imagine that any student would get through my first-semester mechanics class without knowing the contents of Newton's laws (although they might not remember which is the 1st, 2nd, etc.). The reason I give open-notes tests is to convince them not to waste time memorizing random trivia, like the mass of the earth or the equation for the terminal velocity of a sphere. Physics is an unusual subject because there are so few basic principles needed in order to understand the whole subject -- but convincing students of that is difficult; they prefer memorization to understanding. IMO when a professor gives closed-notes exams, often the reason is that the professor is looking for a way to make the course easier. You can write an exam with lots of questions on it that only require memorization, and that makes the exam easy for students who are willing to memorize.
What the hell did these students do 10 years ago? AFAIK two semesters of English and perhaps 1 semester of literature are the norm at every reputable college in the U.S. If their English is too poor for your physics exam, they probably have no hope of graduating.
Hi -- I'm the OP. The school where I teach is a community college in California. There are lots of bad reasons for a student to end up at a community college: lazy, not too bright, etc. Now think about the good reasons. In other words, why would a bright, hard-working student be at a community college rather than a Cal State or UC? Two common answers: (1) The student is living in poverty. (2) The student's native language is Arabic or Chinese or something, and although the student is working hard as hell to get up to speed in English, getting up to a college level isn't a quick process.
Absolutely. I attended a technical college that ran the exams on an Honor System. Most exams were open-book. Professors were not allowed in the classroom once the exam began.
Hi -- I'm the OP. I would love it if my school was on the honor system. I tried to get that to happen when I was on a faculty committee working on that kind of thing, but it went nowhere. Usually at schools that have an honor system, there are very severe penalties if you do get caught cheating, such as suspension or expulsion. AFAICT our administration has been too afraid of lawsuits to go down that road. We've been told that when a student cheats, recent legal decisions say that the most we can do is to give a zero on that assignment (exam, problem set,...). Since we have a 16th-week drop deadline, that effectively means that cheating carries almost no risk. If you don't get caught, you benefit from cheating. If you do get caught, you drop with a W (as opposed to the F you were presumably expecting, which made you desperate enough to cheat).
Today we have radar-ranging that can tell you exactly where the planets are located and how they are moving within a few hundred kilometers or better. The planets move around the sun. There's also the whole thing that a sun-centered model is based on universal laws of physics, while earth-centered models were constructed just to describe the motion of heavenly bodies and had no universality.
More generally, there are preferred reference frames. They're called inertial frames.
The AC was right, although it's hard to tell if he was right for the right reasons. And you're wrong, although your reasons for being wrong are probably more right than his reasons for being right.:-)
Radar cannot tell you what's moving and what's not. It only measures relative motion. Furthermore, modern radar measurements of the solar system are so good that they can detect all kinds of general-relativistic effects. General relativity does not have the same distinction that Newtonian mechanics does between inertial frames and noninertial frames. It has a distinction between frames that are free-falling and frames that aren't, but this fails to distinguish between the earth and the sun, since both are free-falling. You can do general relativity in a frame where the earth is at rest, neither rotating nor revolving around the sun. The gravitational fields and boundary conditions will be strange, and you'll get strange stuff like the Sagnac effect, but you will get a perfectly valid set of predictions for the motion of the planets, which will match the radar data just as well as the predictions made in the frame tied to the solar system's center of mass.
Slashdot Mirror
The summary is completely incorrect. Whoever wrote the summary simply didn't understand the paper. String theory does not predict the production of microscopic black holes at LHC eneries. The paper's abstract says, "Limits on the minimum black hole mass are set, in the range 3.5 -- 4.5 TeV, for a variety of parameters in a model with large extra dimensions, along with model-independent limits on new physics in these final states." Note that phrase "large extra dimensions." Here is the WP article on large extra dimensions. String theory has *small* extra dimensions: extra dimensions that wrap around on themselves at the Planck scale. The LHC doesn't probe the Planck scale. Theories with large extra dimensions have, er, *large* extra dimensions. This experiment falsifies those theories, not string theory.
Two other markets are backpackers and boaters. However, people in those markets generally don't have a need to yak on the phone, they just have a need to be able to get help in an emergency. That's why PLB and SPOT exist. (But an awful lot of people misuse these systems as well, expecting to get helicoptered out of situations that they could have avoided or gotten themselves out of.)
Why, oh why can't people posting science stories on slashdot post links to the actual papers when they're publicly available? http://arxiv.org/abs/1008.2399
This is already pretty darn easy to accomplish in Firefox. Go it "Edit : Preferences : privacy." Uncheck "accept third-party cookies." Select "Keep until: I close Firefox." Under "exceptions," check "allow" for any sites that you frequently visit and want to stay logged in to between sessions.
I don't mind surrendering a little privacy to corporations if they're willing to pay for it. That's what I'm doing when I use the preferred customer mechanism at the supermarket. That's what I'm doing when I get a magazine subscription for much less than the newsstand price. The problem with online advertisers is that they shoot themselves in the foot with their unrealistic expectations. They expect me to give them my information without any economic reward. They expect me to tolerate animated ads that distract me from the text I'm trying to read. Given that their behavior is so unreasonable, I'm willing to take the time to install adblock plus and configure firefox to reject cookies that aren't on my whitelist.
The term has different meanings in nuclear physics than in chemistry. In nuclear physics, it refers to an unusually long-lived excited state of the nucleus.
Seems to me that you're barking up the wrong tree here. Amazon is a corporation, so it's legally considered a person in the U.S. Amazon has a legal right to make political statements under the first amendment. Freedom of speech does not mean that a third party like Amazon can be forced to provide a platform for the views of someone with whom they disagree. Amazon does not need to be able to prove that Wikileaks' activities are illegal. If Amazon decided it wanted to dump Wikileaks as a customer because they didn't like people named Julian, that would be their privilege. Whether or not Wikileaks is violating copyright is kind of a silly issue to be worrying about. IANAL, but my understanding is that under U.S. law, when you write something original and it's fixed in tangible form, you automatically own the copyright; however, works produced by the federal government are not copyrightable, although this doesn't apply, for example, to works produced by contractors. So there may or may not be copyrighted material in the Wikileaks documents, but if Amazon thinks there is, they're entitled to their opinion, and they're entitled to dump a customer for that reason -- even if they're wrong.
So let's be realistic here. The real issue is not whether we think Amazon should or should not have done this. The real issue is whether they were *pressured by the government* into doing this. If they were, then it's de facto censorship. Also, legality is not the same as morality. I approve morally of what Wikileaks has done. If it also happens to have been illegal under U.S. law, that has nothing to do with its morality.
For a long time, the famous Edgerton photos were a staple of physics textbooks. E.g., you could see the (huge) deformation of a tennis ball being hit by a racket. But the Edgerton images are all copyrighted, and it would be really helpful to have CC-BY-SA-compatible photos that could be used instead in places like Wikipedia. I'm the author of some copylefted physics textbooks, and I really haven't been able to find much that's useful. There's this category on wikimedia commons, but there's currently not much in it that's useful educationally. IMO there are a couple of things that would be useful in physics education: (1) an image like the tennis racket, showing how an object's center of mass accelerates even while it's in contact with another object; (2) an image like the bullet going through the apple, which I believe shows that the speed of sound in the apple is less than the speed of the bullet.
Yeah, and although I hate putting money into the pockets of Amazon and E-Bay, this is the reason that they're really useful. They both try pretty hard to get buyers to rate sellers, and therefore you get a relatively unbiased set of ratings compared to what you'd get from the BBB, etc.
The solution to this seems pretty obvious to me. Don't blindly use search engines for shopping. Why in the world would anyone sane google for a product, go to that site, and enter a credit card number?
I buy my running shoes online, but I don't just google '"New Balance" 883 9-2E' and then go to the top hit and buy. I buy through Amazon, which shows me retailers that are willing to sell me those shoes and gives me users' ratings for the various retailers.
Granted, it's unfortunate that this has the effect of siphoning off revenue from mom-and-pop businesses to giant corporations like Amazon and E-Bay. But it reflects the fact that online reputation is hard to evaluate, and that Amazon and E-Bay are doing something useful by building up a database of online reputations.
In theory, I could do a couple of other things that would be better for small retailers. I could go to a local bricks and mortar store. Well, that sort of works, but unfortunately the local bricks and mortar stores don't stock shoes in the wide size I want to buy. I could also google small internet retailers, then try to evaluate their reputation by googling for their name, or by going to some online site that rates online reputation. The problem is that those methods of evaluating reputation aren't very reliable.
I gave a talk on this for students at my school recently. Penrose has a popular-level book out on the topic, which came out a few months before the publication of this claimed observation. The paper describing the observation is here. Here is a talk Penrose gave at Cambridge in 2005 on the topic.
If this is right, then it's certainly a huge discovery. There are at least two pretty big problems, however.
(1) Penrose's model requires some mechanism by which 100% of the massive particles in the universe get recycled into photons or other massless radiation. Black holes can do a lot of this, but there will inevitably be a few lonely hydrogen molecules that never fall into a black hole. Therefore one of the predictions of the model is that there is some novel particle physics going on. In the video of the 2005 talk, you can see that he posits the existence of charged particles lighter than an electron. Various particle physicists pointed out to him that this really isn't possible. (E.g., low-energy photons would interact with matter by pair production, and we observe that that doesn't happen.) By the time he published the popular book, he'd change this to a prediction that all massive particles simply lose their rest mass very, very slowly. This is disappointing, because it means he's stepped back from making testable predictions. "Very, very slowly" can be as slowly as you like, i.e., too slowly to measure, and therefore this aspect of the theory isn't falsifiable.
(2) The other problem is that it's not clear whether the claimed circular patterns are real. Penrose's co-author, the experimentalist on the new paper, is Gurzadyan. Gurzadyan got the WMAP and Boomerang collaborations to give him data. He is not part of those collaborations, but he has a ton of papers on CMB on arxiv, seems to be a heavy hitter in the field. The thing that makes me cautious is that the WMAP and Boomerang collaborations have not jumped on the bandwagon. If they really believed the statistical significance of the result, presumably they'd want their names on this extremely exciting result. Penrose's book also describes a grad student who worked on searching for such patterns in the data, and the book makes it sound like that search was inconclusive. If that grad student (and his advisor) believed in the patterns presently being claimed by Gurzadyan and Penrose, then there's no way in hell that this paper would go out without the grad student's name on them as a co-author; he definitely contributed to the work, and if he believed in the result, his name would be on there.
The whole bongo thing was just part of the media-created, mass-produced "beatnik" phenomenon. It was a trivialized and mass-marketed version of the Beat movement.
>From the photon's point of view they are simultaneous.
Here's a FAQ I wrote about that. The short answer is that there is no frame of reference that coincides with the motion of a photon.
FAQ: What does the world look like in a frame of reference moving at the speed of light?
This question has a long and honorable history. As a young student, Einstein tried to imagine what an electromagnetic wave would look like from the point of view of a motorcyclist riding alongside it. But we now know, thanks to Einstein himself, that it really doesn't make sense to talk about such observers.
The most straightforward argument is based on the positivist idea that concepts only mean something if you can define how to measure them operationally. If we accept this philosophical stance (which is by no means compatible with every concept we ever discuss in physics), then we need to be able to physically realize this frame in terms of an observer and measuring devices. But we can't. It would take an infinite amount of energy to accelerate Einstein and his motorcycle to the speed of light.
Since arguments from positivism can often kill off perfectly interesting and reasonable concepts, we might ask whether there are other reasons not to allow such frames. There are. One of the most basic geometrical ideas is intersection. In relativity, we expect that even if different observers disagree about many things, they agree about intersections of world-lines. Either the particles collided or they didn't. The arrow either hit the bull's-eye or it didn't. So although general relativity is far more permissive than Newtonian mechanics about changes of coordinates, there is a restriction that they should be smooth, one-to-one functions. If there was something like a Lorentz transformation for v=c, it wouldn't be one-to-one, so it wouldn't be mathematically compatible with the structure of relativity. (An easy way to see that it can't be one-to-one is that the length contraction would reduce a finite distance to a point.)
What if a system of interacting, massless particles was conscious, and could make observations? The argument given in the preceding paragraph proves that this isn't possible, but let's be more explicit. There are two possibilities. The velocity V of the system's center of mass either moves at c, or it doesn't. If V=c, then all the particles are moving along parallel lines, and therefore they aren't interacting, can't perform computations, and can't be conscious. (This is also consistent with the fact that the proper time s of a particle moving at c is constant, ds=0.) If V is less than c, then the observer's frame of reference isn't moving at c. Either way, we don't get an observer moving at c.
To all the inevitable pedantic responses about it not "really" happening 30 years old, I'll be even more pedantic. :) Relativity of Simultaneity, look it up. It's absolutely meaningless to talk of the temporal ordering of space-like separated events. In some suitable reference frame, it "really" did happen 30 years ago.
You've got that somewhat garbled. The relevant events would be (A) a photon is emitted from the star, and (B) that photon arrives here on earth. The relationship between A and B is lightlike, not spacelike. Since they are lightlike relative to one another, they do have a well-defined temporal ordering; there is no frame of reference in which B preceded A, or in which A and B are simultaneous. Your final sentence, however, is correct.
The big problem here is that language designers want their languages to get used.
There is a difference between telling your users that they *can* use unicode and telling them that they *have to*. Every language I can think of that said you *had to* use non-ASCII characters is dead: APL, Algol. I don't know about the detailed reasons why nobody actually codes in Algol (maybe just because it was mainly meant as a language for describing algorithms, not for writing practical programs), but APL's absurdly inconvenient character set was surely a reason that it expanded to fill a tiny niche and then quickly died even in that niche.
*Allowing* programmers to use non-ASCII characters is a lot more reasonable, but this is not exactly the world's biggest innovation. Perl allows you to use unicode characters inside string literals, but it also allows you to use, e.g., Chinese characters as names of variables. Is this a good thing? I guess so, in the sense that choice is good. But what happens when someone who doesn't speak Chinese wants to maintain code that uses Chinese variable names? Sure, we shouldn't be cultural chauvinists, but realistically, every literate Chinese person can recognize the letters of the Latin alphabet, whereas the converse isn't true -- coders in New York or Mumbai can't read Chinese characters.
There is also a nontrivial issue of look-alike characters, which could be a source of errors. For example, do I really want to be able to have one variable named Y (upper-case Latin Y) and another named Y (upper-case Greek upsilon)?
Countries like the UK and Israel have experience with terrorism, and they've developed reasonably sane ways of handling it. Just to be clear, I'm not praising the fact that they stole land from the Irish and the Palestinians -- but at least they don't act like total idiots when someone sets off a bomb. The US, on the other hand, responded to 9/11 by running around like a chicken with its head cut off. We shot ourselves in the foot in ways that were far worse than any of the damage done by the 9/11 hijackers, including two wars and an all-out assault on our own civil liberties. Compared to that kind of national self-mutilation, I can't really take it too seriously when I'm not allowed to bring a full-size shampoo bottle on an airplane -- but it certainly is an example of the same idiocy, just on a smaller scale.
Yep. I'm a community college physics teacher. I wrote my own book, and it's free online. Under the model being discussed in TFA, my students' minimum cost would go up from $0 to $35.
The whole reason that the current model sucks is that professors have only a very weak motivation to consider cost when selecting a textbook. Even if they are motivated enough to use price as a criterion, selecting a text is a weak lever, because all the choices from the big publishers are roughly equally overpriced. This proposal would make that *worse*, not better. Professors would go from having weak leverage on price to having none at all. Publishers would extort higher and higher fees every year. Professors would no longer get gratitude from students for putting books online for free, because students would be paying a fixed tax anyway.
This is all about eliminating students' options. No more option to buy a used book, check out a book from a library, borrow the book from a friend who took the course, or use an older edition.
Oh, please.
In feudalism, serfdom was hereditary, and serfs were tied to the land. There is no analog of this in the present-day U.S.
In feudalism, there were mutual obligations between the lord and his serfs. Basically, the serfs had to work the land and give the lord some of what the land produced, and in return the lord had to give military protection from other lords. The U.S. Revolutionary War was essentially fought because the feudal lord (George III) was trying to make a one-sided version of the feudal relationship. He wanted the colonists to have an obligation to him (pay taxes), but they weren't getting anything from him (no military protection from the Indians, for example).
Allodial title doesn't mean immunity from taxes. It means ownership of land without being subject to feudal obligations. Taxes are not a feudal obligation.
I don't think this is quite right. Newspapers are optimized for fitting the maximum number of words in a given area. They sacrifice readability for this in a variety of ways, such as leaving out the comma before an "and," and using narrow columns that force a lot of hyphenation.
I think there is an optimum line length for readability, and it's (not surprisingly) somewhere around the width of a page in a typical paperback or hardcover book. Anything much narrower or much wider reduces readability.
What kind of work are you trying to do? Your post asks about pointing devices, but if you're word-processing or coding, reconsider whether you even need a pointing device. Most of my computer work is word-processing or coding, i.e., just typing characters. I used to use mouse-based editors and word-processors, and my RSI problems were all related to my pointing device -- every time I would reach for the mouse, that's when it would hurt. Since you're asking about pointing devices, it sounds like you also have a problem with pointing devices. So if your work consists of typing characters, just stop using a pointing device. Use an editor such as emacs (good) or vi (evil) that can be controlled without a pointing device. (YMMV as far as good or evil. If God damns you to hell for using vi, I am not responsible. I am not a lawyer or a priest, and this is not legal or religious advice.)
No, this is incorrect. All it requires is for one very speculative piece of physics to be true: large extra dimensions.
If the only modification to the standard model is large extra dimensions, then it's just like any other particle physics experiment, where decay rates are closely related to formation rates. The black holes decay essentially instantaneously. That is why theories with large extra dimensions are not immediately falsified by the lack of geological evidence, or by the fact that we don't observe white dwarfs and neutron stars being destroyed by cosmic ray impacts.
To be *worried* about black hole production at the LHC, i.e., to think that it might be dangerous, is a whole different matter. Your criticisms above are all valid criticisms if someone is saying that the black holes might be produced and not immediately evaporate. That requires some very strange nonstandard physics. Here are some papers on the topic: http://arxiv.org/abs/hep-ph/0402168 http://arxiv.org/abs/0808.4087
FAQ: Do rates of nuclear decay depend on environmental factors?
There is one environmental effect that has been scientifically well established for a long time. In the process of electron capture, a proton in the nucleus combines with an inner-shell electron to produce a neutron and a neutrino. This effect does depend on the electronic environment, and in particular, the process cannot happen if the atom is completely ionized.
Other claims of environmental effects on decay rates are crank science, often quoted by creationists in their attempts to discredit evolutionary and geological time scales.
He et al. (He 2007) claim to have detected a change in rates of beta decay of as much as 11% when samples are rotated in a centrifuge, and say that the effect varies asymmetrically with clockwise and counterclockwise rotation. He believes that there is a mysterious energy field that has both biological and nuclear effects, and that it relates to circadian rhythms. The nuclear effects were not observed when the experimental conditions were reproduced by Ding et al.
Jenkins and Fischbach (2008) claim to have observed effects on alpha decay rates at the 10^-3 level, correlated with an influence from the sun. They proposed that their results could be tested more dramatically by looking for changes in the rate of alpha decay in radioisotope thermoelectric generators aboard space probes. Such an effect turned out not to exist (Cooper 2009). Undeterred by their theory's failure to pass their own proposed test, they have gone on to publish even kookier ideas, such as a neutrino-mediated effect from solar flares, even though solar flares are a surface phenomenon, whereas neutrinos come from the sun's core. An independent study found no such link between flares and decay rates (Parkhomov 2010). Jenkins and Fischbach's latest claims, in 2010, are based on experiments done decades ago by other people, so that Jenkins and Fischbach have no first-hand way of investigating possible sources of systematic error. Laboratory experiments[Lindstrom 2010] have also placed limits on the sensitivity of radioactive decay to neutron flux that rule out a neutrino-mediated effect at a level orders of magnitude less than what would be required in order to explain the variations claimed in [Jenkins 2008].
Cardone et al. claim to have observed variations in the rate of alpha decay of thorium induced by 20 kHz ultrasound, and claim that this alpha decay occurs without the emission of gamma rays. Ericsson et al. have pointed out multiple severe problems with Cardone's experiments.
He YuJian et al., Science China 50 (2007) 170.
YouQian Ding et al., Science China 52 (2009) 690.
Jenkins and Fischbach (2008), http://arxiv.org/abs/0808.3283v1
Jenkins and Fischbach (2009), http://arxiv.org/abs/0808.3156
Jenkins and Fischbach (2010), http://arxiv.org/abs/1007.3318
Parkhomov, http://arxiv.org/abs/1006.2295
Cooper (2009), http://arxiv.org/abs/0809.4248
F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956
Ericsson et al., Comment on "Piezonuclear decay of thorium," Phys. Lett. A 373 (2009) 1956, http://arxiv4.library.cornell.edu/abs/0907.0623
Ericsson et al., http://arxiv.org/abs/0909.2141
Lindstrom et al. (2010), http://arxiv.org/abs/1006.5071
Hi -- I'm the OP. I can't imagine that any student would get through my first-semester mechanics class without knowing the contents of Newton's laws (although they might not remember which is the 1st, 2nd, etc.). The reason I give open-notes tests is to convince them not to waste time memorizing random trivia, like the mass of the earth or the equation for the terminal velocity of a sphere. Physics is an unusual subject because there are so few basic principles needed in order to understand the whole subject -- but convincing students of that is difficult; they prefer memorization to understanding. IMO when a professor gives closed-notes exams, often the reason is that the professor is looking for a way to make the course easier. You can write an exam with lots of questions on it that only require memorization, and that makes the exam easy for students who are willing to memorize.
Hi -- I'm the OP. The school where I teach is a community college in California. There are lots of bad reasons for a student to end up at a community college: lazy, not too bright, etc. Now think about the good reasons. In other words, why would a bright, hard-working student be at a community college rather than a Cal State or UC? Two common answers: (1) The student is living in poverty. (2) The student's native language is Arabic or Chinese or something, and although the student is working hard as hell to get up to speed in English, getting up to a college level isn't a quick process.
Hi -- I'm the OP. I would love it if my school was on the honor system. I tried to get that to happen when I was on a faculty committee working on that kind of thing, but it went nowhere. Usually at schools that have an honor system, there are very severe penalties if you do get caught cheating, such as suspension or expulsion. AFAICT our administration has been too afraid of lawsuits to go down that road. We've been told that when a student cheats, recent legal decisions say that the most we can do is to give a zero on that assignment (exam, problem set, ...). Since we have a 16th-week drop deadline, that effectively means that cheating carries almost no risk. If you don't get caught, you benefit from cheating. If you do get caught, you drop with a W (as opposed to the F you were presumably expecting, which made you desperate enough to cheat).
The AC was right, although it's hard to tell if he was right for the right reasons. And you're wrong, although your reasons for being wrong are probably more right than his reasons for being right. :-)
Radar cannot tell you what's moving and what's not. It only measures relative motion. Furthermore, modern radar measurements of the solar system are so good that they can detect all kinds of general-relativistic effects. General relativity does not have the same distinction that Newtonian mechanics does between inertial frames and noninertial frames. It has a distinction between frames that are free-falling and frames that aren't, but this fails to distinguish between the earth and the sun, since both are free-falling. You can do general relativity in a frame where the earth is at rest, neither rotating nor revolving around the sun. The gravitational fields and boundary conditions will be strange, and you'll get strange stuff like the Sagnac effect, but you will get a perfectly valid set of predictions for the motion of the planets, which will match the radar data just as well as the predictions made in the frame tied to the solar system's center of mass.