How about if I withhold my software until you pay me? The free market will set the price. Is that OK?
Of course. Why are you setting up ridiculous straw-man arguments?
First you ask about how you can make a living in a hypothetical world in which all software is "free," presumably meaning that it's free-as-in-beer (doesn't cost money). But that world doesn't exist, and never will, for fundamental reasons. E.g., nobody is going to write an application for free for a corporation's internal use, to do something that only that corporation needs to do. Furthermore, nobody is calling for a world in which all software is free-as-in-beer -- not even people like RMS, who would like to see everyone use 100% free-as-in-speech software.
Now you seem to be asking whether someone's going to... what, send the police to your house and force you to release your software for free? Nobody has proposed that.
I need to feed my family. I write code for a living. How do I get paid for doing this in a world where all software is free?
I would think the answer was pretty obvious. Write software for which there is no free equivalent, or write software that is better than the free equivalent.
This would be extremely interesting if the strategy document had dated to before 9/11 -- but did it? It was published in 2005. It may just be al Qaeda trying to make itself out to be a bunch of masterminds several years after the fact. Just from browsing though the WP articles on OBL and 9/11, I don't see much to support the idea that such a grand strategy existed before 2001, or even before the Kenya attacks in 1998, as you seem to be claiming. Al Qaeda carried out all kinds of attacks, including attacks that killed Egyptian civilians. It's well documented that their motivation was that they were upset about US troops in Saudi Arabia, US support for Israel, and the sanctions against Iraq. What evidence is there that they had any such grand plan as early as 1998?
You're doing something nobody has done before, inventing it as you go, and people expect you to know in advance how much it's going to cost. There are always unforeseen things that crop up.
It's an order of magnitude bigger than the Hubble, and they bid $0.8 billion initially, which is less than $2.5 billion the Hubble cost to build and launch. I wouldn't call that unforseen. It was simply massively underbid.
So I highly doubt a 30km/s rotation around our sun will impact our interaction with the CMB when our relative motion to it around the center of the milky way seams to be 390 KM/s.
You're right, it isn't the velocity relative to the CMB that's relevant, it's basically the velocity relative to the galactic halo. The dark matter particles they claim to be detecting would be gravitationally bound to the galaxy. I think the rest of what I wrote is correct. Check out the link I gave in the GP post, and also this paper http://arxiv.org/abs/1011.3076 , where they predicted the yearly modulation before they started the experiment. They measure a yearly modulation of about 16%, and that is apparently consistent with theory.
There are lots of experiments of this type running right now. This team, CRESST-II, has announced that they have more events than can be explained by their background. However, that's not really the most convincing evidence you could ask for, since the background could have been underestimated. A more convincing thing to see is that some of the experiments are reporting signals that are modulated by the expected amount on a yearly basis by the earth's motion relative to the frame of the cosmic microwave background. Here is a paper that includes a survey of the the results as of June. There are some apparent contradictions between some groups' positive results and others' negative results.
It does seem to be pretty common for people to apply the term "open source" to things that aren't. For example, when Schwarzenegger was governor of California, he started a Free Digital Textbook Initiative. I went to a symposium set up by the state about this initiative. Many people at the meeting used "open source" correctly to describe their books. E.g., the book's LaTeX source code was freely available, and the book was under a CC-BY-SA license. But Pearson, a big commercial textbook publisher, sent a representative, who talked about how Pearson was doing books that were "open source." Actually their sole free offering was a consumable biology workbook that was available as a free PDF download. But they heard everyone else saying "open source," and it sounded like good pixie dust, so they started using the term.
I forgot, if you want try any of the books that go beyond the level of Exploring Black Holes, you're going to need to learn some linear algebra. There happens to be an excellent free book on this topic: http://joshua.smcvt.edu/linalg.html/
You've made an admirable attempt to define your question clearly, but you didn't quite succeed. General relativity can be understood at a variety of mathematical levels, so saying you want to understand "the mathematics of general relativity" doesn't really pin it down.
The other issue is that you haven't defined your physics background. If you really want to understand GR, you need to be fairly sophisticated in physics.
The first thing I'd suggest is that you build a solid foundation of understanding in special relativity. The best intro to SR is Taylor and Wheeler, Spacetime Physics, and you already have the math background to understand that.
Physically, GR is a field theory. The first field theory was electromagnetism. E&M is a lot easier to understand than GR, because it takes place on a fixed background of flat spacetime, and it also connects directly to everyday experience. The more intuition and technical skill you can build up in the context of E&M, the better prepared you'll be for GR. For someone ambitious about going far in physics, the best intro to E&M is Purcell, Electricity and Magnetism. Purcell uses vector calculus, and he tries to teach you all the vector calc you need as he goes along. However, you will want some of the preparation provided by a second-semester calc course, and you will probably also have an easier time if you can also study from a separate book on vector calculus. Here is a free online calc book that I like, and here is a free vector calc book you could use. When you're learning second-semester calc, I'd suggest you skip the integration tricks that form the bulk of such a course; they're largely irrelevant to your goal, and nowadays you can use Maxima or integrals.com for that kind of thing.
With that background, you're more than prepared to start studying GR at the level of Exploring Black Holes, by Taylor and Wheeler.
If you want to go on after that and understand GR at a higher mathematical level, you could try an upper-division undergrad book such as Hartle or my own free book, and then maybe move on to a graduate-level texts. The mathematics used in graduate-level texts is typically introduced explicitly in the text itself; basically tensors and calculus on a manifold. You don't need any more math prerequisites than vector calculus before diving in. The classic graduate text is Misner, Thorne, and Wheeler. I would still recommend it wholeheartedly, except that it's now decades out of date. A more modern alternative is Carroll; there is a free online version, plus a more complete and up to date print version. Other GR books worth owning are General Relativity by Wald and The Large-Scale Structure of Space-Time by Hawking and Ellis.
Kdawson, could you please try to have the first clue about something that you submit?
There's no reason to be so rude. In fact, I would consider the summary pretty accurate, although maybe not the title.
This is a non-peer-reviewed article, fresh on the arXiv.
Totally irrelevant. New research typically appears on arxiv first. That doesn't mean it's wrong.
It's a followup to an earlier article which was widely criticized within the community as being full of holes, and the arguments in this article are very very weak.
I'm not a specialist in this field (my specialty is experimental nuclear physics), but the impression I get as an outsider is that this is inaccurate. Actually many people in the field seem to find Kobakhidze's arguments very strong. I think the most fair summary would be that right now, the whole thing is controversial. Verlinde never claimed that he had a worked-out theory. It's always just been a rough heuristic. Even if it's right, it's wrong. What I mean by that is that it's at best a provisional picture (historically analogous to the Bohr atom) which needs to be reworked into a real theory (analogous to quantum mechanics). Just as there were no clear criteria for judging whether the Bohr model was a good idea or a dead end in 1915, there are no clear criteria for judging whether this idea is good or a dead end in 2011.
A lower price is neither necessary nor sufficient to get me to buy.
I would love to be able to switch a lot of my book buying to digital. My house has as many paper books in it as it can comfortably hold, so when I get a new one, I have to throw out an old one. But two things are holding me back: (1) Formats like epub are basically html without support for mathml, which means that for math and science books, they're not an option. (2) Nobody has a large selection of DRM-free books. Historically, all DRM schemes have tended to exist for no more than about 3-5 years, after which the buyers have lost 100% of their investment. (I have ideological issues with DRM as well, but this purely economic and practical issue is enough make digital books a no-go for me.)
The price of the reader isn't a huge issue for me. If the DRM-free content was available, I'd be willing to pay $500 for a reading device. Since the DRM-free content doesn't exist, I wouldn't even be willing to take a reader if someone gave me one for free.
The slashdot summary is totally inaccurate. The law wouldn't "ban all electronic communication between teachers and students." This post explains what it would actually do. Basically they wanted to make sure parents have access to all electronic communication between teachers and students.
I will say that historically, the Hugos go to more high quality books than the Nebulas, though overall quality is still lacking; the failure of Iain Banks or Alastair Reynolds to have won a single Hugo is kind of ridiculous.
De gustibus non est disputandum, but personally, I thought Consider Phlebas was one of the worst books I'd ever read, and I stopped in the middle. I thought Revelation Space was pretty bad as well.
The Hugos are awarded by fans, the Nebulas by writers who are members of the Science Fiction and Fantasy Writers of America, SFWA. Ca. 2007, a lot of SF writers started questioning whether SFWA was relevant anymore. A couple of their elected officers showed extremely poor judgment (google "sfwa hendrix" and "sfwa burt"), and this seems to have been symptomatic of more widespread dysfunction within the organization.
They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.
Yes, and the existence of gravitational waves has already been proved indirectly by the Hulse-Taylor binary pulsar system, which is losing energy at exactly the rate predicted by general relativity. There is really no doubt about the existence of gravitational waves, either theoretically or empirically. LIGO is cool because it could open the door to a new way of doing astronomy, not because there is doubt about the existence of gravitational waves.
You actually don't have to be a complete kook to doubt that solar-mass bodies like Cygnus X-1 are black holes. There are all kinds of other hypothesized objects that they could be, including black stars, gravastars, fuzzballs, quark stars, boson stars, and electroweak stars. These are all long-shots, but they exist in certain reasonably well-motivated physical theories.
For skeptics, I believe the evidence is stronger that Sagittarius A* is a black hole than that Cygnus X-1 is. Sag A* is the supermassive black hole at the center of our galaxy. Sag A* has been proved by indirect but very strong evidence to have an event horizon, which is essentially the defining characteristic of a black hole. (A singularity without an event horizon would be something different; the big bang singularity is an example of that.) It may become possible in the near future to do direct imaging of Sag A*'s event horizon, which would be direct proof that it's a black hole. There are fundamental reasons why we will never be able to do anything like that with any other black hole besides Sag A*, using foreseeable technology.
Gmail and yahoo both sign all outgoing messages cryptographically using dkim. That means that if you get a spam claiming to be from one of their accounts, you can verify that it really is from such an account. Once you've done that, you can report it: gmail, yahoo. So if the author of TFA is complaining that this can't be accomplished by sending email to abuse@gmail.com or postmaster@gmail.com, then I suppose he has a valid complaint that they're not complying with RFCs...but...that's the way it is. It's not the end of the world. Gotta use a web interface instead. Boo hoo.
The author of TFA is upset that he can't get spamming accounts shut down instantly, 24/7. I actually don't really want an internet where any random person can get my ability to send email shut down instantly. What if it's a joe-job? What if the complaint is from one of these people who just clicks on "spam" when they don't want the mail, even when it's not spam? A much better way to handle this is to limit the number of messages per hour that can be sent from a newly created account. Then if it takes a day, or three days, to shut down a spam account, the consequences aren't that bad; the spammer can't use the account to send a million emails in 24 hours. I assume that gmail and yahoo already do this kind of rate-limiting.
What would be a huge improvement would be if the remaining big email providers other than gmail and yahoo would start using dkim. Once dkim becomes universal, we can establish actual reputations for people as spammers or non-spammers.
Virtually all the spam I get these days is from small domains. Recent examples include education-portal.com, spacesaver.com, and mg-style.net. The solution proposed by the author of TFA is to bug education-portal.com to respond to email sent to abuse@education-portal.com by deactivating jones@education-portal.com. Um, that isn't going to work, because jones works for education-portal.com, and they want him to spam me. The solution is to make dkim universal enough that people can stop accepting mail from domains that don't dkim-sign. Then education-portal.com can get an online reputation as a spammer, and everyone can start blocking them in their spam filters.
Sorry to tell you this, but the whole banana thing was a mistake. Your body maintains an equilibrium with respect to potassium. When you eat a banana, you quickly excrete just as much potassium as you ate. Negligible net increase in your radiation dose.
Slashdot Mirror
How about if I withhold my software until you pay me? The free market will set the price. Is that OK?
Of course. Why are you setting up ridiculous straw-man arguments?
First you ask about how you can make a living in a hypothetical world in which all software is "free," presumably meaning that it's free-as-in-beer (doesn't cost money). But that world doesn't exist, and never will, for fundamental reasons. E.g., nobody is going to write an application for free for a corporation's internal use, to do something that only that corporation needs to do. Furthermore, nobody is calling for a world in which all software is free-as-in-beer -- not even people like RMS, who would like to see everyone use 100% free-as-in-speech software.
Now you seem to be asking whether someone's going to ... what, send the police to your house and force you to release your software for free? Nobody has proposed that.
Please stop trolling.
I need to feed my family. I write code for a living. How do I get paid for doing this in a world where all software is free?
I would think the answer was pretty obvious. Write software for which there is no free equivalent, or write software that is better than the free equivalent.
Here's mine:
Maybe the high percentage it got had a lot to do with the fact that this was in India, so there were language and cross-cultural issues.
This would be extremely interesting if the strategy document had dated to before 9/11 -- but did it? It was published in 2005. It may just be al Qaeda trying to make itself out to be a bunch of masterminds several years after the fact. Just from browsing though the WP articles on OBL and 9/11, I don't see much to support the idea that such a grand strategy existed before 2001, or even before the Kenya attacks in 1998, as you seem to be claiming. Al Qaeda carried out all kinds of attacks, including attacks that killed Egyptian civilians. It's well documented that their motivation was that they were upset about US troops in Saudi Arabia, US support for Israel, and the sanctions against Iraq. What evidence is there that they had any such grand plan as early as 1998?
You're doing something nobody has done before, inventing it as you go, and people expect you to know in advance how much it's going to cost. There are always unforeseen things that crop up.
It's an order of magnitude bigger than the Hubble, and they bid $0.8 billion initially, which is less than $2.5 billion the Hubble cost to build and launch. I wouldn't call that unforseen. It was simply massively underbid.
So I highly doubt a 30km/s rotation around our sun will impact our interaction with the CMB when our relative motion to it around the center of the milky way seams to be 390 KM/s.
You're right, it isn't the velocity relative to the CMB that's relevant, it's basically the velocity relative to the galactic halo. The dark matter particles they claim to be detecting would be gravitationally bound to the galaxy. I think the rest of what I wrote is correct. Check out the link I gave in the GP post, and also this paper http://arxiv.org/abs/1011.3076 , where they predicted the yearly modulation before they started the experiment. They measure a yearly modulation of about 16%, and that is apparently consistent with theory.
There are lots of experiments of this type running right now. This team, CRESST-II, has announced that they have more events than can be explained by their background. However, that's not really the most convincing evidence you could ask for, since the background could have been underestimated. A more convincing thing to see is that some of the experiments are reporting signals that are modulated by the expected amount on a yearly basis by the earth's motion relative to the frame of the cosmic microwave background. Here is a paper that includes a survey of the the results as of June. There are some apparent contradictions between some groups' positive results and others' negative results.
It does seem to be pretty common for people to apply the term "open source" to things that aren't. For example, when Schwarzenegger was governor of California, he started a Free Digital Textbook Initiative. I went to a symposium set up by the state about this initiative. Many people at the meeting used "open source" correctly to describe their books. E.g., the book's LaTeX source code was freely available, and the book was under a CC-BY-SA license. But Pearson, a big commercial textbook publisher, sent a representative, who talked about how Pearson was doing books that were "open source." Actually their sole free offering was a consumable biology workbook that was available as a free PDF download. But they heard everyone else saying "open source," and it sounded like good pixie dust, so they started using the term.
What the AC said was this:
Dirac went looking to remove the square from E=mc^2 since it allowed for the possibility of negative matter and energy.
He thinks Dirac rewrote E=mc^2 as E=mc, which is total nonsense.
Dirac went looking to remove the square from E=mc^2 since it allowed for the possibility of negative matter and energy.
You're confused. This is totally incorrect.
I forgot, if you want try any of the books that go beyond the level of Exploring Black Holes, you're going to need to learn some linear algebra. There happens to be an excellent free book on this topic: http://joshua.smcvt.edu/linalg.html/
You've made an admirable attempt to define your question clearly, but you didn't quite succeed. General relativity can be understood at a variety of mathematical levels, so saying you want to understand "the mathematics of general relativity" doesn't really pin it down.
The other issue is that you haven't defined your physics background. If you really want to understand GR, you need to be fairly sophisticated in physics.
The first thing I'd suggest is that you build a solid foundation of understanding in special relativity. The best intro to SR is Taylor and Wheeler, Spacetime Physics, and you already have the math background to understand that.
Physically, GR is a field theory. The first field theory was electromagnetism. E&M is a lot easier to understand than GR, because it takes place on a fixed background of flat spacetime, and it also connects directly to everyday experience. The more intuition and technical skill you can build up in the context of E&M, the better prepared you'll be for GR. For someone ambitious about going far in physics, the best intro to E&M is Purcell, Electricity and Magnetism. Purcell uses vector calculus, and he tries to teach you all the vector calc you need as he goes along. However, you will want some of the preparation provided by a second-semester calc course, and you will probably also have an easier time if you can also study from a separate book on vector calculus. Here is a free online calc book that I like, and here is a free vector calc book you could use. When you're learning second-semester calc, I'd suggest you skip the integration tricks that form the bulk of such a course; they're largely irrelevant to your goal, and nowadays you can use Maxima or integrals.com for that kind of thing.
With that background, you're more than prepared to start studying GR at the level of Exploring Black Holes, by Taylor and Wheeler.
If you want to go on after that and understand GR at a higher mathematical level, you could try an upper-division undergrad book such as Hartle or my own free book, and then maybe move on to a graduate-level texts. The mathematics used in graduate-level texts is typically introduced explicitly in the text itself; basically tensors and calculus on a manifold. You don't need any more math prerequisites than vector calculus before diving in. The classic graduate text is Misner, Thorne, and Wheeler. I would still recommend it wholeheartedly, except that it's now decades out of date. A more modern alternative is Carroll; there is a free online version, plus a more complete and up to date print version. Other GR books worth owning are General Relativity by Wald and The Large-Scale Structure of Space-Time by Hawking and Ellis.
some months ago there was a study proposing that black people do not have Neanderthal ancestry. do they have a different immune system?
Yes. Click through to the BBC News article.
Kdawson, could you please try to have the first clue about something that you submit?
There's no reason to be so rude. In fact, I would consider the summary pretty accurate, although maybe not the title.
This is a non-peer-reviewed article, fresh on the arXiv.
Totally irrelevant. New research typically appears on arxiv first. That doesn't mean it's wrong.
It's a followup to an earlier article which was widely criticized within the community as being full of holes, and the arguments in this article are very very weak.
I'm not a specialist in this field (my specialty is experimental nuclear physics), but the impression I get as an outsider is that this is inaccurate. Actually many people in the field seem to find Kobakhidze's arguments very strong. I think the most fair summary would be that right now, the whole thing is controversial. Verlinde never claimed that he had a worked-out theory. It's always just been a rough heuristic. Even if it's right, it's wrong. What I mean by that is that it's at best a provisional picture (historically analogous to the Bohr atom) which needs to be reworked into a real theory (analogous to quantum mechanics). Just as there were no clear criteria for judging whether the Bohr model was a good idea or a dead end in 1915, there are no clear criteria for judging whether this idea is good or a dead end in 2011.
A lower price is neither necessary nor sufficient to get me to buy.
I would love to be able to switch a lot of my book buying to digital. My house has as many paper books in it as it can comfortably hold, so when I get a new one, I have to throw out an old one. But two things are holding me back: (1) Formats like epub are basically html without support for mathml, which means that for math and science books, they're not an option. (2) Nobody has a large selection of DRM-free books. Historically, all DRM schemes have tended to exist for no more than about 3-5 years, after which the buyers have lost 100% of their investment. (I have ideological issues with DRM as well, but this purely economic and practical issue is enough make digital books a no-go for me.)
The price of the reader isn't a huge issue for me. If the DRM-free content was available, I'd be willing to pay $500 for a reading device. Since the DRM-free content doesn't exist, I wouldn't even be willing to take a reader if someone gave me one for free.
The slashdot summary is totally inaccurate. The law wouldn't "ban all electronic communication between teachers and students." This post explains what it would actually do. Basically they wanted to make sure parents have access to all electronic communication between teachers and students.
I will say that historically, the Hugos go to more high quality books than the Nebulas, though overall quality is still lacking; the failure of Iain Banks or Alastair Reynolds to have won a single Hugo is kind of ridiculous.
De gustibus non est disputandum, but personally, I thought Consider Phlebas was one of the worst books I'd ever read, and I stopped in the middle. I thought Revelation Space was pretty bad as well.
So ... what's your pick for best SF novel of 2010!?!? I want to read it!
Typical Hollywood action movie, nothing special. Interminable sections of it were like watching a video game.
The Hugos are awarded by fans, the Nebulas by writers who are members of the Science Fiction and Fantasy Writers of America, SFWA. Ca. 2007, a lot of SF writers started questioning whether SFWA was relevant anymore. A couple of their elected officers showed extremely poor judgment (google "sfwa hendrix" and "sfwa burt"), and this seems to have been symptomatic of more widespread dysfunction within the organization.
They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.
Yes, and the existence of gravitational waves has already been proved indirectly by the Hulse-Taylor binary pulsar system, which is losing energy at exactly the rate predicted by general relativity. There is really no doubt about the existence of gravitational waves, either theoretically or empirically. LIGO is cool because it could open the door to a new way of doing astronomy, not because there is doubt about the existence of gravitational waves.
hough some think the graviton is likely to be a tachyon (a particle that is faster than light.)
Complete nonsense. Please don't post garbage about topics you don't know anything about.
You actually don't have to be a complete kook to doubt that solar-mass bodies like Cygnus X-1 are black holes. There are all kinds of other hypothesized objects that they could be, including black stars, gravastars, fuzzballs, quark stars, boson stars, and electroweak stars. These are all long-shots, but they exist in certain reasonably well-motivated physical theories.
For skeptics, I believe the evidence is stronger that Sagittarius A* is a black hole than that Cygnus X-1 is. Sag A* is the supermassive black hole at the center of our galaxy. Sag A* has been proved by indirect but very strong evidence to have an event horizon, which is essentially the defining characteristic of a black hole. (A singularity without an event horizon would be something different; the big bang singularity is an example of that.) It may become possible in the near future to do direct imaging of Sag A*'s event horizon, which would be direct proof that it's a black hole. There are fundamental reasons why we will never be able to do anything like that with any other black hole besides Sag A*, using foreseeable technology.
Gmail and yahoo both sign all outgoing messages cryptographically using dkim. That means that if you get a spam claiming to be from one of their accounts, you can verify that it really is from such an account. Once you've done that, you can report it: gmail, yahoo. So if the author of TFA is complaining that this can't be accomplished by sending email to abuse@gmail.com or postmaster@gmail.com, then I suppose he has a valid complaint that they're not complying with RFCs...but...that's the way it is. It's not the end of the world. Gotta use a web interface instead. Boo hoo.
The author of TFA is upset that he can't get spamming accounts shut down instantly, 24/7. I actually don't really want an internet where any random person can get my ability to send email shut down instantly. What if it's a joe-job? What if the complaint is from one of these people who just clicks on "spam" when they don't want the mail, even when it's not spam? A much better way to handle this is to limit the number of messages per hour that can be sent from a newly created account. Then if it takes a day, or three days, to shut down a spam account, the consequences aren't that bad; the spammer can't use the account to send a million emails in 24 hours. I assume that gmail and yahoo already do this kind of rate-limiting.
What would be a huge improvement would be if the remaining big email providers other than gmail and yahoo would start using dkim. Once dkim becomes universal, we can establish actual reputations for people as spammers or non-spammers.
Virtually all the spam I get these days is from small domains. Recent examples include education-portal.com, spacesaver.com, and mg-style.net. The solution proposed by the author of TFA is to bug education-portal.com to respond to email sent to abuse@education-portal.com by deactivating jones@education-portal.com. Um, that isn't going to work, because jones works for education-portal.com, and they want him to spam me. The solution is to make dkim universal enough that people can stop accepting mail from domains that don't dkim-sign. Then education-portal.com can get an online reputation as a spammer, and everyone can start blocking them in their spam filters.
Sorry to tell you this, but the whole banana thing was a mistake. Your body maintains an equilibrium with respect to potassium. When you eat a banana, you quickly excrete just as much potassium as you ate. Negligible net increase in your radiation dose.