That IS indeed real time. Relativity tells us nothing can have an effect here in less time. I don't know if you're trolling or just ignorant, but by your definition you can never look at the stars, galaxies or nebulae in the sky in real time either because they're all at varying distances and we're seeing light that originated anything from about 4 to several million years ago. With telescopes you can go back billions.
You're both rude and wrong. GP is correct.
"Relativity tells us nothing can have an effect here in less time." True, but that doesn't mean that it's real time. Here are a few examples that show that it's completely ridiculous to call it real time:
The cosmic microwave background is the glow of the hot early universe, from shortly after the Big Bang. No cosmologist would refer to this as seeing the Big Bang "in real time."
It's possible for a ray of light to travel in a circular orbit around a black hole. That means that it would theoretically be possible for me to face in a certain direction, stick out my tongue, and then turn around 180 degrees, look through a telescope, and, some time later, see myself sticking my tongue out at myself. I'm obviously not seeing myself "in real time."
As a third example, there are distant galaxies whose light hasn't gotten to us yet. I don't think anyone would argue that we are seeing them "in real time" -- we haven't even seen them yet.
It sounds like you're misinterpreting something you heard about the nature of simultaneity in relativity. You can define simultaneity in relativity. You simply have to keep in mind that it's relative, not absolute.
In special relativity, the standard way to do this is Einstein synchronization. The relative motions of the bodies in the solar system, as well as all space probes launched so far, is at velocities much less than c, so it doesn't even matter very much whether you talk about doing your Einstein synchronization in the frame of the earth, of mars, or whatever. This is the sense in which the information from Mars is 15 minutes behind "real time." (There are also gravitational time dilations, and they're also quite small.)
Since you brought up astronomy and cosmological look-back times, it's worth addressing that as well. To describe cosmological scales, you need general relativity, and in general relativity Einstein synchronization doesn't work. However, there is a natural notion of clock synchronization in cosmology that is defined as follows. At any spot in the universe, define a frame of reference that is at rest with respect to the cosmic microwave background (or the local flow of galaxies, which amounts to the same thing). Define a time coordinate as measured by a clock that is at rest in that frame. This is what cosmologists mean when they state the age of the universe as so many billions of years. This time coordinate is also the only reasonable definition of "in real time" for use in cosmology.
Next time, please try being more polite and/or getting your facts right.
But that brings up something I've been wondering for awhile which is this....at what point would it be better to toss the hardware? I mean you can buy one of those E350 based kits for less than $150
It sounds like you have applications such as networked storage or firewall boxes in mind, but for desktop use, you can can actually get quite nice used desktop hardware for less than $150 -- often less than half that. For about 8 years now, I've been buying cheap machines, putting linux on them, and putting them in my physics lab for my students to use. For a while I was going to garage sales, Salvation Army, and shops that sold used boxes. But recently I've found that really nice hardware is becoming available on ebay at very reasonable prices. Here are some examples of some recent machines I've bought:
HP Pavilion Desktop D4100Y Pentium D 2.80 GHz 1 GB Memory/PC2-3200, $40+$23 shipping
HP XW4400 Workstation Intel Core 2 DUO E6300 1.86GHz 250GB 1GB CD-RW/ DVD, $90+$24 shipping
HP Compaq D330 uT Intel Pentium 4 2.66GHZ 80GB HDD 1GB DDR Desktop PC, $30+$23 shipping
Even with shipping, it's a lot less money than you'd pay locally for the same hardware. It's also much less work to find it, and it's not in need of as many upgrades as the kind of stuff you find at garage sales, etc., where many machines have no CD drive, no ethernet, or not enough memory.
I typically install ubuntu and set them up with xfce as the default wm. Performance is fine.
The slashdot summary is completely garbled. It contains this sentence: "Especially when it seems to contain an obvious glaring mistake." There is nothing like this in the article. The mistake described in the article is a mistake that Bose made during a lecture, which happened to lead to a calculation that described how nature actually works. By the time Bose wrote his paper, there was not "an obvious glaring mistake." It was now presented as a scientific hypothesis, intentionally formed, about how nature actually works.
Sorry about the mangled logic in the above post. This part: "which is how they verify that your account isn't a sock puppet" is in the wrong place. It should refer to amazon, not slashdot and stackexchange.
A real names policy is important in some cases, is impossible in some cases, and is both important and impossible in some cases.
An example where it's important is online book reviews. You don't want authors reviewing their own books, or, e.g., university professors getting their grad students to give five-star reviews of their advisor's book.
An example where it's impossible is basically any web site that isn't selling a product. Presently, the main method for verifying people's real-world identities is to have them buy something with a credit card. For example, Amazon will let you review a book you didn't buy from them, but it won't let you post reviews if you've never bought anything from them. Sites like slashdot and stackexchange can't do this, which is how they verify that your account isn't a sock puppet. As an alternative to credit cards, it would be great if we could get a worldwide web of trust going, but it just ain't happening so far, due to network effects.
See my sig for a case where a real names policy is both vitally important and impossible to verify. This is a site I run that catalogs free books and accepts user-submitted reviews. I have a real names policy, but I have no good way to enforce it -- although in many cases it's transparently obvious that people are violating it (e.g., they post a review that is cut and pasted from their own web site), in which case I delete the review.
Because when it comes to open source software, when it stops becoming interesting and fun the projects stop being really maintained and start developing bugs with new hardware, security flaws that are unpatched, etc.
It's mature software. Mature software is pretty much by definition not interesting or fun. But TFA describes how Red Hat is paying 10 people to work on GNOME. Presumably these people are still there because they get a paycheck, and they can endure the fact that the project is mature and not bleeding edge.
TFA seems to be describing a mature software project that has entered maintenance mode. Why would this be a bad thing?
TFA says, "Distros are dropping GNOME for other environments instead of working with GNOME," with "other" and "environments" hyperlinked to Unity and Cinnamon. Actually, aren't these projects that share a ton of code with GNOME? So what's the problem? Users have a bunch of different choices. The developers offering these choices are sharing code. Users who prefer something outside this family of choices, such as KDE or Fluxbox or XFCE, can also do their own thing. This is also good. All the same apps run just fine in all these different environments. This is also good.
TFA says, "The claimed target users for GNOME are leaving desktop computers behind for types of devices GNOME doesn't work on," with hyperlinks referring to smartphones and tablet computers. Again, I don't see the problem. Users have other choices besides keyboard-and-mouse computers. I kind of doubt that anyone is choosing to use a smartphone to write their novel, so maybe users are actually using the correct tool for the correct job: desktops for the jobs that desktops are good for, smartphones for the jobs that smartphones are good for. Once again, what's the problem?
I try to get my college buddies to send me encrypted email, and it's the same story, "Dude, just use Facebook like everybody else".
Your friends are perfectly sane not to bother with encrypted email. There are two serious problems with encrypted email: (1) poor ease of use, and (2) network effects (i.e., it's not useful unless lots of people use it, but people won't use it because it's not useful).
#1 is actually not easy to fix, because it's inherently difficult to manage a public/private key infrastructure. This inherent difficulty shows up in the fact that the software is much too hard for the typical user.
#2 is also basically impossible to fix.
For these reasons, email is always going to be an insecure medium, just like postcards are always going to be insecure. If you need more security, use snail mail, which is highly legally protected in the US and is not run by telecoms that are only too happy to shit on the constitution.
If the complaint about how "rise of run isn't a formal definition of slope" is indicative of the kinds of errors in his lectures, then I'd say Khan is right that the naysayers are just being picky. Yah, it's not perfectly accurate or a formal definition, but it's an excellent start to understanding a deeper understanding.
First off, you've misquoted the article. Please don't put things in quotes if they aren't what the person actually said.
Anyway, I think you're missing the point here. The point isn't that rise/run isn't formal. (They didn't use the word "formal.") The point is exactly the opposite of that. If you read the context, the point he's making is that the definition is purely formal, not conceptual.
I teach physics, and this is exactly the complaint I have about the Khan Academy physics videos that I've looked at. They show students examples of worked problems, but they don't deal with concepts. It's the "plug and chug" mentality.
If your ultimate (and final) response when asked why you believe something is "because my teacher told me", then you really don't understand the subject matter very well at all.
And this is exactly what's poisonous about the Khan Academy's approach. Their videos teach the "how" without the "why."
It really all comes down to this. Kahn Academy is non-profit, and is more interested in the public good. Everybody else that wants to get on this bandwagon simply can't compete with this, because they want money, and lots of it.
Huh? Either you don't know what you're talking about or you're describing the situation in some country I've never heard of. This is certainly not the situation in the US.
Just to pick a few random examples in the US, the University of California is nonprofit; the ivy leagues are all nonprofit; the University of Chicago is nonprofit.
At least in the US, for-profit colleges are a relatively recent innovation, and typically they are scams. They bring in underprepared students, suck up their government benefits (e.g., GI Bill money), and then spew them out on the job market, where they don't get jobs.
What I really see is from the security scandal and many many other problems including spammers taking over, and feature rott, are all a sign of a lack of vision and people just giving a damn about their products. Their products reak, porn spammers even go into the children's chat rooms for crying out loud and spam every 1 minute!
Here's another pathetic example. Yahoo was the inventor of the DKIM system for cryptographically signing email in 2004. It's a valuable tool for fighting spam. When you get spam from a yahoo or gmail address, you can tell whether or not the return address is forged. If it's not forged, you can complain using a web interface. But within the last year or so, yahoo eliminated that interface, so they're no longer getting the full benefit of the DKIM system that they themselves invented. Here is the URL where the form used to be; it now redirects to a useless help page.
I'm not sure what the point is of a newspaper in 2012.
The point is the same as it was 50 years ago. The point is to get in-depth news and opinion.
My young son asked me about newspapers, and I explained it as "A tiny little part of the internet, printed out yesterday, and delivered to your house".
You can read newspapers online, so your whining about the fact that it's up to (gasp!) 24 hours out of date is irrelevant. The complaint that it's "a tiny little part of the internet" is even sillier. What do you actually want to do, read the whole internet every day?
He's completely uninterested. Everyone in my generation knows we're supposed to feel newspapers are important, maybe a sense of guilt at not subscribing.
No, not "everyone." I don't know what generation you're from, but every generation old enough to read contains at least some people who do think newspapers are important, and who don't feel any guilt because they do subscribe. So let's get rid of the over-generalization and think a bit about what you're really saying. What you're really saying is that you belong to the majority that gets their news from sources that are not as good as newspapers. Sources like crappy local TV news, Fox News, and that story about the cute bunnies that your sister emailed you the link to.
Rather like the donation campaigns for the Ballet at work, no one wants to go but we've all been socialized to believe its important.
No, not "no one." I enjoy the ballet myself, and I go several times a year with my wife. So, to clean up your sloppy reasoning again, what's really going on is that some people like ballet and some don't, some read newspapers and some don't.
However, newspapers are so far off the modern cultural radar, that my kids don't even get the point.
Where do you think people got their news in 1975? Most of them got it from local TV news, not newspapers. In general, the majority of the population in every civilization, in every era, have been either unable to think deeply about events and issues or uninterested in doing so. That hasn't changed, and probably never will.
But they still want to ban gay marriage and abortion, right? Just want to make sure we're talking about the same freedom-loving Libertarians, here.
You should really replace "Libertarians" with "Ron Paul" here. In particular, the libertarian candidate for president, Gary Johnson, supports both gay marriage and abortion rights: http://www.ontheissues.org/gary_johnson.htm Although I disagree with Ron Paul on abortion, and didn't vote for him in 2008 for that reason, his position is emotionally understandable considering his background as an obstetrician.
Libertarians are not monolithic on all the issues, which to me is a sign of health. Another noteworthy issue on which there's great diversity among LP politicians is immigration -- you see all kinds of positions ranging from Jan Brewer-style xenophobia to people advocating completely opening the borders and eliminating any government quotas or controls.
Science is not a zero-sum game. Scientific discoveries enrich everybody, regardless of which country they're made in.
The SSC was way over budget. Better to pull the plug than to give various contractors a blank check.
American physicists are well represented at the LHC. Grad students are still being trained, etc. It's not like American experimental particle physics was dealt a fatal blow from which it can never recover by the cancellation of the SSC.
The actual fatal blow to accelerator-based experimental particle physics may be a world-wide one, due to (1) accelerator technology reaching the point of diminishing returns, and (2) a physics scenario in which the Higgs is detected but absolutely nothing else (such as supersymmetry) turns up. If this is how things turn out, then we'll just have to say that accelerator physics was a field that was active and then died. It happens. There's no god-given rule that says that every academic field will remain viable forever. Take a look at the Nobel prizes in physics from years like 1912 and 1920. The future of experimental particle physics may be in cosmic ray experiments, for example. If so, then the US Congress will look prescient for canceling the SSC.
The article makes an analogy with physical exploration of outer space, but that doesn't quite work. The "space race" happened because both sides in the Cold War wanted a propaganda victory. After the Cold War ended, projects like the ISS and the shuttle continued because of pork-barrel politics.
SETI is qualitatively different. If the Allen Telescope Array manages to keep going and then succeeds, it won't be a propaganda victory for any national government, and it won't put any aerospace company on the federal gravy train. From the point of view of politicians and industrialists, there's no motivation for SETI.
There's also no obvious reason why a success for SETI in 2020 AD is any better or worse for humanity than a success in 2120 or 3020. The ATA is designed to survey a sphere a thousand light-years in radius. If we detect a signal from a civilization 1000 l.y. away, there's no possibility of a two-way conversation. It's like discovering the first dinosaur fossil. Sure, it would be cool to be the one to dig it up, but there's no hurry to dig it up. It was there for millions of years and wasn't going anywhere if we didn't dig it up. If there are radio beacons in our galaxy transmitting "I am here" signals, then statistically such signals have probably existed for millions of years and will continue to exist for millions of years into the future. You can make up scenarios where a successful SETI gives some kind of moral or spiritual lift to H. sapiens right when we needed it. You can also make up science fiction stories where it has no big effect on us, or even a negative effect (e.g., we receive a signal modulated with super-duper scientific knowledge, which helps us to blow up the world or something).
The mass opinion is indeed so negative it's hard to believe that anybody would program anything in C.
Huh? What mass opinion? Where's the evidence for this?
Pick the right tool for the job. C is the right tool for some jobs, specifically jobs like writing drivers or operating systems.
Historically, C won by having an innovative syntax for pointers, which a lot of people liked, and it also won by being a small language that was easy to implement. Because it was small and easy to implement, it ended up being widely available. Ca. 1980, the joke was that C was like masturbation: it might not be what you really want, but it's always available. A lot of people in 2012 may not realize that in the era when C was winning popularity, people didn't usually have access to free compilers, and for many types of hardware (e.g., 8-bit desktops like the TRS-80), there simply weren't any good development tools. Another big win for C was that because it was so widely available, it became easy to find programmers who could code in it; it fed on its own success in a positive feedback loop. This is why languages like java had C-like syntax -- they wanted to ride the coattails of C.
IMO the biggest problems have been when people started to use C for tasks for which it wasn't the right tool. It started creeping up into higher-level applications, where it wasn't really appropriate. This became particularly problematic with the rise of the internet. Networks used to be small and run by people with whom you had personal contact, so nobody really cared about the kind of buffer-overflow vulnerabilities that C is prone to. The attitude was that if you gave a program crazy input that caused it to crash, well, what was the big deal? You crashed the program, and you were only hurting yourself.
But linux especially needs to offer the GUI as the primary interface for EVERYTHING. I know the old linux hands disagree. This is why you have adoption problems. [...] And of course hardware venders frequently don't release drivers for your OS. Fix the GUI issue and all that will change.
This would make a lot of sense... if it were even loosely based on reality.
My wife, my 12-year-old daughter, and my mother in law all use linux as their only desktop OS. None of them know a CLI from a hole in the ground. None of them needs a CLI to do anything they want to do. They use GUIs exclusively -- mainly Firefox, libreoffice, and GIMP. There is no "GUI issue."
And because you have adoption problems many companies don't write software for your OS requiring the open source community to write everything themselves.
The existence of open-source applications on linux is a good thing, not a bad thing.
Roughly speaking, there are three levels of "greenness", for lack of a better word. "Off the grid" means you're totally self-sufficient; probably solar during the day stored to batteries for night, combined with ultra-efficient stuff. "Net zero" means you self-generate a surplus of power sometimes and a deficit others, selling your excess to the power company and buying your need.
Not really. First, being off the grid typically isn't a choice people make when they have the option of being on the grid. It's usually what people do when they live in remote areas where the grid simply doesn't reach. And anyway, being off the grid is normally less green than being net zero and on the grid. Most people who are off the grid are under capacity for their needs, and typically they make up for that by running a generator sometimes -- which is very bad environmentally. (Battery systems that let you store energy in the day for use at night are extremely big and expensive, and I don't know how common they are in real life. They require maintenance and are dangerous if not properly maintained. I suspect that a gigantic battery is not likely to be very green, either. You have all those chemicals, which have to be disposed of when the battery reaches its end of life.) On the other hand, if they have excess capacity, that's energy that's being wasted rather than going to people who are on the grid, so again it's less green than being on the grid. And it's essentially impossible to have an off-grid system that has exactly the right capacity for your needs. That's because energy production varies dramatically from day to day and month to month due to clouds and the height of the sun in the sky.
On-grid photovoltaics are actually really nice environmentally, because they produce the most power on hot, sunny days, which are exactly the days when a lot of people are using air conditioners. The solar energy helps keep the electric company from having to fire up more generators and feed more fossil fuels into them.
Here is an article that touches on how some of this plays out in real life.
The problem with bedrest (among the obvious ones of removing the subject from useful tasks for a month) is that it causes a large amount of muscle loss and the very bone loss it is trying to detect. What's more, the bone loss from immobilization is rapid and it may take years to recover from.
And ironically, this may imply exactly the opposite of the Slashdot summary's pro-space spin. Some background first.
Once the cold war and the space race were over, NASA and its contractors went through all kinds of contortions to try to justify continuing the pork-barrel funding of human spaceflight. There have been all kinds of benefits proposed, from inspiring schoolchildren to guaranteeing jobs in aerospace, but none of them have been very convincing as a justification for the amount of money being spent, which, while small in proportion to the federal budget, is nevertheless a boatload of money every year.
One of the arguments was that the shuttle, and later the ISS, were going to be platforms for scientific research in microgravity. This sort of does make sense, because you can't do that type of science anywhere else than in earth orbit, and there may be certain kinds of work that require human scientists to be present. We were supposed to get manufacturing techniques that could only exist in microgravity, e.g., growing perfect crystals -- oops, never worked out. We were also supposed to learn all about the biological effects of microgravity.
Basically the microgravity research idea didn't work out. Astronauts aboard the ISS are extremely busy all the time, basically because it's a hell of a lot of work just staying alive up there. Simple tasks like cleaning take up a huge amount of their time. They just don't have enough time to do a significant amount of science. Not only is the amount of good science very small, but the bang for the buck is lousy, and has been made even lousier by the crazy cost overruns on the ISS as well as the failure of the space shuttle to be as cheap as it was supposed to be.
And the main result of research into the biological effects of microgravity is that these effects are extremely negative. Osteoporosis is just one of the many extremely debilitating effects experienced by astronauts aboard the ISS. When they get back to earth, they're completely wrecked physically and have to go through a long period of physical conditioning to get back to anything like reasonable shape. Many of the effects are exactly analogous to the effects of bed rest.
So what we're really learning here is that humans are fundamentally not well adapted to microgravity. If humans are ever going to live permanently in space, it's probably going to have to be aboard rotating space stations that provide the equivalent of a gravitational field. (We don't know for sure, but most likely a gravitational field like the moon's is not enough for human health.) Oops, but if the point of the space shuttle and ISS was supposed to be that we could do stuff in microgravity... what would be the point of a rotating space station, which wouldn't provide a microgravity environment? Well, none, really.
This is another point against anyone who claims NASA, and going to space in general, is a complete waste of money.
This has always been a totally bogus argument, because you can't do a controlled experiment. Suppose that the US had never engaged in the Cold War propaganda exercise known as the space race. Later, suppose that the US had never gotten into pork-barrel projects such as the space shuttle and the ISS. What would the world have been like? We have no way of figuring out what scientific advances would have been made in this alternate history.
Maybe more tax money would have been directed toward unmanned space exploration, which, unlike human spaceflight, provides scientific results in reasonable proportion to what it costs.
Maybe the nonexistence of a government monopoly on human spaceflight would have encouraged the private sector to start up a space tourism industry decades ago, and my wife and I would have celebrated out 20th anniversary last year in orbit.
Maybe, simply by reducing the size of government, we would have boosted the over-all economy a little bit, and through exponential growth (the "butterfly effect") that small change would have made the economy significantly bigger today, say by 10%. In a 10% bigger economy, a fixed percentage of taxes spent on cancer research means 10% more cancer research, so maybe we'd have a cure for cancer now.
Maybe one smart person, rather than becoming an engineer on the Apollo program, would instead have gone into fundamental research in physics, and we'd have a theory of quantum gravity today.
We just have no way of knowing. You could just as easily say that World War II was a good thing, because without it we would never have invented radar.
I've never tried to use this kind of software for automatically picking routes for trail running, etc. The reason I consider yournavigation.org's driving directions unusable is that although they do give the right route, they break it up into tiny pieces. Driving 20 miles on a single freeway is broken up into literally 10 or 15 tiny segments, e.g., they tell you to continue driving 150' as the freeway goes over an overpass. Secondary problems are that the web interface never seems to do the lookups properly for the beginning and end points, and you can't modify the route with the mouse.
One point where Open Street Map shines is that it has actual roads and trails in such places as National Parks and forests...where the commercial maps have nothing but blank green areas.
Yep. For example, here is a place in the Alps in openstreetmap, and here is the same place in google maps, and here is the same thing in routes.tomtom.com. Only openstreetmap shows the hiking trail (as well as peaks with their elevations, and mountain huts). This is a really good thing for hikers, runners and mountain bikers.
You can also get topo maps based on OSM data from toposm.com, although this still seems pretty primitive and they only cover the US. Google's maps with contour shading are OK, but they don't let you print them through their web interface (although you can always print a screenshot), and they don't show contour lines.
What isn't so great about OSM is that driving directions from yournavigation.org are not usable at all. Also, the search functionality is (not surprisingly) inferior to the one in google maps -- if you don't put in exactly the right form of the name, it doesn't work.
You missed the other factor of u. The expression u sqrt(u^2 + v^2) gives the x component of a vector with squared magnitude u^2 + v^2 that points in the direction of (u,v).
Slashdot Mirror
You're both rude and wrong. GP is correct.
"Relativity tells us nothing can have an effect here in less time." True, but that doesn't mean that it's real time. Here are a few examples that show that it's completely ridiculous to call it real time:
The cosmic microwave background is the glow of the hot early universe, from shortly after the Big Bang. No cosmologist would refer to this as seeing the Big Bang "in real time."
It's possible for a ray of light to travel in a circular orbit around a black hole. That means that it would theoretically be possible for me to face in a certain direction, stick out my tongue, and then turn around 180 degrees, look through a telescope, and, some time later, see myself sticking my tongue out at myself. I'm obviously not seeing myself "in real time."
As a third example, there are distant galaxies whose light hasn't gotten to us yet. I don't think anyone would argue that we are seeing them "in real time" -- we haven't even seen them yet.
It sounds like you're misinterpreting something you heard about the nature of simultaneity in relativity. You can define simultaneity in relativity. You simply have to keep in mind that it's relative, not absolute.
In special relativity, the standard way to do this is Einstein synchronization. The relative motions of the bodies in the solar system, as well as all space probes launched so far, is at velocities much less than c, so it doesn't even matter very much whether you talk about doing your Einstein synchronization in the frame of the earth, of mars, or whatever. This is the sense in which the information from Mars is 15 minutes behind "real time." (There are also gravitational time dilations, and they're also quite small.)
Since you brought up astronomy and cosmological look-back times, it's worth addressing that as well. To describe cosmological scales, you need general relativity, and in general relativity Einstein synchronization doesn't work. However, there is a natural notion of clock synchronization in cosmology that is defined as follows. At any spot in the universe, define a frame of reference that is at rest with respect to the cosmic microwave background (or the local flow of galaxies, which amounts to the same thing). Define a time coordinate as measured by a clock that is at rest in that frame. This is what cosmologists mean when they state the age of the universe as so many billions of years. This time coordinate is also the only reasonable definition of "in real time" for use in cosmology.
Next time, please try being more polite and/or getting your facts right.
It sounds like you have applications such as networked storage or firewall boxes in mind, but for desktop use, you can can actually get quite nice used desktop hardware for less than $150 -- often less than half that. For about 8 years now, I've been buying cheap machines, putting linux on them, and putting them in my physics lab for my students to use. For a while I was going to garage sales, Salvation Army, and shops that sold used boxes. But recently I've found that really nice hardware is becoming available on ebay at very reasonable prices. Here are some examples of some recent machines I've bought:
HP Pavilion Desktop D4100Y Pentium D 2.80 GHz 1 GB Memory /PC2-3200, $40+$23 shipping
HP XW4400 Workstation Intel Core 2 DUO E6300 1.86GHz 250GB 1GB CD-RW/ DVD, $90+$24 shipping
HP Compaq D330 uT Intel Pentium 4 2.66GHZ 80GB HDD 1GB DDR Desktop PC, $30+$23 shipping
Gateway GT5637E AMD Athlon 64 X2 3800+ 160GB HDD 2GB DDR2 CD-RW/ DVD-RW, $110+$20 shipping
Even with shipping, it's a lot less money than you'd pay locally for the same hardware. It's also much less work to find it, and it's not in need of as many upgrades as the kind of stuff you find at garage sales, etc., where many machines have no CD drive, no ethernet, or not enough memory.
I typically install ubuntu and set them up with xfce as the default wm. Performance is fine.
The slashdot summary is completely garbled. It contains this sentence: "Especially when it seems to contain an obvious glaring mistake." There is nothing like this in the article. The mistake described in the article is a mistake that Bose made during a lecture, which happened to lead to a calculation that described how nature actually works. By the time Bose wrote his paper, there was not "an obvious glaring mistake." It was now presented as a scientific hypothesis, intentionally formed, about how nature actually works.
Sorry about the mangled logic in the above post. This part: "which is how they verify that your account isn't a sock puppet" is in the wrong place. It should refer to amazon, not slashdot and stackexchange.
A real names policy is important in some cases, is impossible in some cases, and is both important and impossible in some cases.
An example where it's important is online book reviews. You don't want authors reviewing their own books, or, e.g., university professors getting their grad students to give five-star reviews of their advisor's book.
An example where it's impossible is basically any web site that isn't selling a product. Presently, the main method for verifying people's real-world identities is to have them buy something with a credit card. For example, Amazon will let you review a book you didn't buy from them, but it won't let you post reviews if you've never bought anything from them. Sites like slashdot and stackexchange can't do this, which is how they verify that your account isn't a sock puppet. As an alternative to credit cards, it would be great if we could get a worldwide web of trust going, but it just ain't happening so far, due to network effects.
See my sig for a case where a real names policy is both vitally important and impossible to verify. This is a site I run that catalogs free books and accepts user-submitted reviews. I have a real names policy, but I have no good way to enforce it -- although in many cases it's transparently obvious that people are violating it (e.g., they post a review that is cut and pasted from their own web site), in which case I delete the review.
It's mature software. Mature software is pretty much by definition not interesting or fun. But TFA describes how Red Hat is paying 10 people to work on GNOME. Presumably these people are still there because they get a paycheck, and they can endure the fact that the project is mature and not bleeding edge.
...and I like it.
TFA seems to be describing a mature software project that has entered maintenance mode. Why would this be a bad thing?
TFA says, "Distros are dropping GNOME for other environments instead of working with GNOME," with "other" and "environments" hyperlinked to Unity and Cinnamon. Actually, aren't these projects that share a ton of code with GNOME? So what's the problem? Users have a bunch of different choices. The developers offering these choices are sharing code. Users who prefer something outside this family of choices, such as KDE or Fluxbox or XFCE, can also do their own thing. This is also good. All the same apps run just fine in all these different environments. This is also good.
TFA says, "The claimed target users for GNOME are leaving desktop computers behind for types of devices GNOME doesn't work on," with hyperlinks referring to smartphones and tablet computers. Again, I don't see the problem. Users have other choices besides keyboard-and-mouse computers. I kind of doubt that anyone is choosing to use a smartphone to write their novel, so maybe users are actually using the correct tool for the correct job: desktops for the jobs that desktops are good for, smartphones for the jobs that smartphones are good for. Once again, what's the problem?
Your friends are perfectly sane not to bother with encrypted email. There are two serious problems with encrypted email: (1) poor ease of use, and (2) network effects (i.e., it's not useful unless lots of people use it, but people won't use it because it's not useful).
#1 is actually not easy to fix, because it's inherently difficult to manage a public/private key infrastructure. This inherent difficulty shows up in the fact that the software is much too hard for the typical user.
#2 is also basically impossible to fix.
For these reasons, email is always going to be an insecure medium, just like postcards are always going to be insecure. If you need more security, use snail mail, which is highly legally protected in the US and is not run by telecoms that are only too happy to shit on the constitution.
First off, you've misquoted the article. Please don't put things in quotes if they aren't what the person actually said.
Anyway, I think you're missing the point here. The point isn't that rise/run isn't formal. (They didn't use the word "formal.") The point is exactly the opposite of that. If you read the context, the point he's making is that the definition is purely formal, not conceptual.
I teach physics, and this is exactly the complaint I have about the Khan Academy physics videos that I've looked at. They show students examples of worked problems, but they don't deal with concepts. It's the "plug and chug" mentality.
And this is exactly what's poisonous about the Khan Academy's approach. Their videos teach the "how" without the "why."
It really all comes down to this. Kahn Academy is non-profit, and is more interested in the public good. Everybody else that wants to get on this bandwagon simply can't compete with this, because they want money, and lots of it.
Huh? Either you don't know what you're talking about or you're describing the situation in some country I've never heard of. This is certainly not the situation in the US.
Just to pick a few random examples in the US, the University of California is nonprofit; the ivy leagues are all nonprofit; the University of Chicago is nonprofit.
At least in the US, for-profit colleges are a relatively recent innovation, and typically they are scams. They bring in underprepared students, suck up their government benefits (e.g., GI Bill money), and then spew them out on the job market, where they don't get jobs.
Here's another pathetic example. Yahoo was the inventor of the DKIM system for cryptographically signing email in 2004. It's a valuable tool for fighting spam. When you get spam from a yahoo or gmail address, you can tell whether or not the return address is forged. If it's not forged, you can complain using a web interface. But within the last year or so, yahoo eliminated that interface, so they're no longer getting the full benefit of the DKIM system that they themselves invented. Here is the URL where the form used to be; it now redirects to a useless help page.
The point is the same as it was 50 years ago. The point is to get in-depth news and opinion.
You can read newspapers online, so your whining about the fact that it's up to (gasp!) 24 hours out of date is irrelevant. The complaint that it's "a tiny little part of the internet" is even sillier. What do you actually want to do, read the whole internet every day?
No, not "everyone." I don't know what generation you're from, but every generation old enough to read contains at least some people who do think newspapers are important, and who don't feel any guilt because they do subscribe. So let's get rid of the over-generalization and think a bit about what you're really saying. What you're really saying is that you belong to the majority that gets their news from sources that are not as good as newspapers. Sources like crappy local TV news, Fox News, and that story about the cute bunnies that your sister emailed you the link to.
No, not "no one." I enjoy the ballet myself, and I go several times a year with my wife. So, to clean up your sloppy reasoning again, what's really going on is that some people like ballet and some don't, some read newspapers and some don't.
Where do you think people got their news in 1975? Most of them got it from local TV news, not newspapers. In general, the majority of the population in every civilization, in every era, have been either unable to think deeply about events and issues or uninterested in doing so. That hasn't changed, and probably never will.
You should really replace "Libertarians" with "Ron Paul" here. In particular, the libertarian candidate for president, Gary Johnson, supports both gay marriage and abortion rights: http://www.ontheissues.org/gary_johnson.htm Although I disagree with Ron Paul on abortion, and didn't vote for him in 2008 for that reason, his position is emotionally understandable considering his background as an obstetrician.
Libertarians are not monolithic on all the issues, which to me is a sign of health. Another noteworthy issue on which there's great diversity among LP politicians is immigration -- you see all kinds of positions ranging from Jan Brewer-style xenophobia to people advocating completely opening the borders and eliminating any government quotas or controls.
Oh, god, this is stupid.
Science is not a zero-sum game. Scientific discoveries enrich everybody, regardless of which country they're made in.
The SSC was way over budget. Better to pull the plug than to give various contractors a blank check.
American physicists are well represented at the LHC. Grad students are still being trained, etc. It's not like American experimental particle physics was dealt a fatal blow from which it can never recover by the cancellation of the SSC.
The actual fatal blow to accelerator-based experimental particle physics may be a world-wide one, due to (1) accelerator technology reaching the point of diminishing returns, and (2) a physics scenario in which the Higgs is detected but absolutely nothing else (such as supersymmetry) turns up. If this is how things turn out, then we'll just have to say that accelerator physics was a field that was active and then died. It happens. There's no god-given rule that says that every academic field will remain viable forever. Take a look at the Nobel prizes in physics from years like 1912 and 1920. The future of experimental particle physics may be in cosmic ray experiments, for example. If so, then the US Congress will look prescient for canceling the SSC.
The article makes an analogy with physical exploration of outer space, but that doesn't quite work. The "space race" happened because both sides in the Cold War wanted a propaganda victory. After the Cold War ended, projects like the ISS and the shuttle continued because of pork-barrel politics.
SETI is qualitatively different. If the Allen Telescope Array manages to keep going and then succeeds, it won't be a propaganda victory for any national government, and it won't put any aerospace company on the federal gravy train. From the point of view of politicians and industrialists, there's no motivation for SETI.
There's also no obvious reason why a success for SETI in 2020 AD is any better or worse for humanity than a success in 2120 or 3020. The ATA is designed to survey a sphere a thousand light-years in radius. If we detect a signal from a civilization 1000 l.y. away, there's no possibility of a two-way conversation. It's like discovering the first dinosaur fossil. Sure, it would be cool to be the one to dig it up, but there's no hurry to dig it up. It was there for millions of years and wasn't going anywhere if we didn't dig it up. If there are radio beacons in our galaxy transmitting "I am here" signals, then statistically such signals have probably existed for millions of years and will continue to exist for millions of years into the future. You can make up scenarios where a successful SETI gives some kind of moral or spiritual lift to H. sapiens right when we needed it. You can also make up science fiction stories where it has no big effect on us, or even a negative effect (e.g., we receive a signal modulated with super-duper scientific knowledge, which helps us to blow up the world or something).
Huh? What mass opinion? Where's the evidence for this?
Pick the right tool for the job. C is the right tool for some jobs, specifically jobs like writing drivers or operating systems.
Historically, C won by having an innovative syntax for pointers, which a lot of people liked, and it also won by being a small language that was easy to implement. Because it was small and easy to implement, it ended up being widely available. Ca. 1980, the joke was that C was like masturbation: it might not be what you really want, but it's always available. A lot of people in 2012 may not realize that in the era when C was winning popularity, people didn't usually have access to free compilers, and for many types of hardware (e.g., 8-bit desktops like the TRS-80), there simply weren't any good development tools. Another big win for C was that because it was so widely available, it became easy to find programmers who could code in it; it fed on its own success in a positive feedback loop. This is why languages like java had C-like syntax -- they wanted to ride the coattails of C.
IMO the biggest problems have been when people started to use C for tasks for which it wasn't the right tool. It started creeping up into higher-level applications, where it wasn't really appropriate. This became particularly problematic with the rise of the internet. Networks used to be small and run by people with whom you had personal contact, so nobody really cared about the kind of buffer-overflow vulnerabilities that C is prone to. The attitude was that if you gave a program crazy input that caused it to crash, well, what was the big deal? You crashed the program, and you were only hurting yourself.
This would make a lot of sense ... if it were even loosely based on reality.
My wife, my 12-year-old daughter, and my mother in law all use linux as their only desktop OS. None of them know a CLI from a hole in the ground. None of them needs a CLI to do anything they want to do. They use GUIs exclusively -- mainly Firefox, libreoffice, and GIMP. There is no "GUI issue."
The existence of open-source applications on linux is a good thing, not a bad thing.
Not really. First, being off the grid typically isn't a choice people make when they have the option of being on the grid. It's usually what people do when they live in remote areas where the grid simply doesn't reach. And anyway, being off the grid is normally less green than being net zero and on the grid. Most people who are off the grid are under capacity for their needs, and typically they make up for that by running a generator sometimes -- which is very bad environmentally. (Battery systems that let you store energy in the day for use at night are extremely big and expensive, and I don't know how common they are in real life. They require maintenance and are dangerous if not properly maintained. I suspect that a gigantic battery is not likely to be very green, either. You have all those chemicals, which have to be disposed of when the battery reaches its end of life.) On the other hand, if they have excess capacity, that's energy that's being wasted rather than going to people who are on the grid, so again it's less green than being on the grid. And it's essentially impossible to have an off-grid system that has exactly the right capacity for your needs. That's because energy production varies dramatically from day to day and month to month due to clouds and the height of the sun in the sky.
On-grid photovoltaics are actually really nice environmentally, because they produce the most power on hot, sunny days, which are exactly the days when a lot of people are using air conditioners. The solar energy helps keep the electric company from having to fire up more generators and feed more fossil fuels into them.
Here is an article that touches on how some of this plays out in real life.
And ironically, this may imply exactly the opposite of the Slashdot summary's pro-space spin. Some background first.
Once the cold war and the space race were over, NASA and its contractors went through all kinds of contortions to try to justify continuing the pork-barrel funding of human spaceflight. There have been all kinds of benefits proposed, from inspiring schoolchildren to guaranteeing jobs in aerospace, but none of them have been very convincing as a justification for the amount of money being spent, which, while small in proportion to the federal budget, is nevertheless a boatload of money every year.
One of the arguments was that the shuttle, and later the ISS, were going to be platforms for scientific research in microgravity. This sort of does make sense, because you can't do that type of science anywhere else than in earth orbit, and there may be certain kinds of work that require human scientists to be present. We were supposed to get manufacturing techniques that could only exist in microgravity, e.g., growing perfect crystals -- oops, never worked out. We were also supposed to learn all about the biological effects of microgravity.
Basically the microgravity research idea didn't work out. Astronauts aboard the ISS are extremely busy all the time, basically because it's a hell of a lot of work just staying alive up there. Simple tasks like cleaning take up a huge amount of their time. They just don't have enough time to do a significant amount of science. Not only is the amount of good science very small, but the bang for the buck is lousy, and has been made even lousier by the crazy cost overruns on the ISS as well as the failure of the space shuttle to be as cheap as it was supposed to be.
And the main result of research into the biological effects of microgravity is that these effects are extremely negative. Osteoporosis is just one of the many extremely debilitating effects experienced by astronauts aboard the ISS. When they get back to earth, they're completely wrecked physically and have to go through a long period of physical conditioning to get back to anything like reasonable shape. Many of the effects are exactly analogous to the effects of bed rest.
So what we're really learning here is that humans are fundamentally not well adapted to microgravity. If humans are ever going to live permanently in space, it's probably going to have to be aboard rotating space stations that provide the equivalent of a gravitational field. (We don't know for sure, but most likely a gravitational field like the moon's is not enough for human health.) Oops, but if the point of the space shuttle and ISS was supposed to be that we could do stuff in microgravity ... what would be the point of a rotating space station, which wouldn't provide a microgravity environment? Well, none, really.
This has always been a totally bogus argument, because you can't do a controlled experiment. Suppose that the US had never engaged in the Cold War propaganda exercise known as the space race. Later, suppose that the US had never gotten into pork-barrel projects such as the space shuttle and the ISS. What would the world have been like? We have no way of figuring out what scientific advances would have been made in this alternate history.
Maybe more tax money would have been directed toward unmanned space exploration, which, unlike human spaceflight, provides scientific results in reasonable proportion to what it costs.
Maybe the nonexistence of a government monopoly on human spaceflight would have encouraged the private sector to start up a space tourism industry decades ago, and my wife and I would have celebrated out 20th anniversary last year in orbit.
Maybe, simply by reducing the size of government, we would have boosted the over-all economy a little bit, and through exponential growth (the "butterfly effect") that small change would have made the economy significantly bigger today, say by 10%. In a 10% bigger economy, a fixed percentage of taxes spent on cancer research means 10% more cancer research, so maybe we'd have a cure for cancer now.
Maybe one smart person, rather than becoming an engineer on the Apollo program, would instead have gone into fundamental research in physics, and we'd have a theory of quantum gravity today.
We just have no way of knowing. You could just as easily say that World War II was a good thing, because without it we would never have invented radar.
I've never tried to use this kind of software for automatically picking routes for trail running, etc. The reason I consider yournavigation.org's driving directions unusable is that although they do give the right route, they break it up into tiny pieces. Driving 20 miles on a single freeway is broken up into literally 10 or 15 tiny segments, e.g., they tell you to continue driving 150' as the freeway goes over an overpass. Secondary problems are that the web interface never seems to do the lookups properly for the beginning and end points, and you can't modify the route with the mouse.
This is what's great about free information -- you can add it yourself. Click on Edit above the map.
Yep. For example, here is a place in the Alps in openstreetmap, and here is the same place in google maps, and here is the same thing in routes.tomtom.com. Only openstreetmap shows the hiking trail (as well as peaks with their elevations, and mountain huts). This is a really good thing for hikers, runners and mountain bikers.
You can also get topo maps based on OSM data from toposm.com, although this still seems pretty primitive and they only cover the US. Google's maps with contour shading are OK, but they don't let you print them through their web interface (although you can always print a screenshot), and they don't show contour lines.
What isn't so great about OSM is that driving directions from yournavigation.org are not usable at all. Also, the search functionality is (not surprisingly) inferior to the one in google maps -- if you don't put in exactly the right form of the name, it doesn't work.
Cool, thanks for checking that! As explained here, what's going on is that the expression is only a constant of the motion for v>0.
You missed the other factor of u. The expression u sqrt(u^2 + v^2) gives the x component of a vector with squared magnitude u^2 + v^2 that points in the direction of (u,v).