Derived from basic mathematical principles means derived mathematically from simple axioms, like F = ma.
So now you're saying that at least Newton's Second Law was not derived from anything; do I understand that right? If so, that's what I said the first time... F=ma (like Newton's other laws, and the c=constant thing) is purely observational, not derived from some other axiom. This is what I'm suggesting is the difference between a "law" (such as F=ma) and a "theory".
Newton's "Laws" of Motion are derived from basic mathematical premises, just like Einstein's theory of relativity.
Really? Which principles? We were always told that, for example, F=ma is simply given; that's just what happens. Everything else is built up from that. (It's sort of an axiom.) You're saying that Newton derived F=ma from somewhere?
(Nitpick: neither Newton's stuff nor Einstein's stuff are based on basic mathematical principles. If anything, they're based on basic physical principles. The math is just a tool; the Physics is the meaty stuff.:)
I recently heard an interesting description of the difference between a "Law" and a "Theory": a "law" is purely observational, whereas a "theory" implies some understanding of what's going on underneath things; a theory is derived from more basic principles. Newton's Laws of Motion, and Kepler's Laws of Orbit, are based on observations (fits, basically), although they might have had at least some idea of why it might be that way. Einstein's Theory of Relativity is derived from the ground up starting from some basic principles (I think you can get most (all?) of it from assuming the speed of light is a constant for all inertial reference frames!).
I thought that was a neat way to look at it, anyway. I don't know if it holds universally...
The reason we have different projects isn't so much about competition and ego, despite the fact that so many people seem to think otherwise (or try to make it otherwise). That may happen from time to time (or a lot), but most of the time it's because different people have different ideas on how to do something. They have different ideas of what "excellent" is.
I like all the options. Because of all the options, I get to use really useful, powerful systems, like FVWM2, Galeon, LaTeX, etc, rather than the more "mainstream" KDE/Gnome, Mozilla, OpenOffice, or whatever, all of which are much harder to use (for me) than the ones I do use. Different people feel different things are important, and they grab the bits of various projects that they like and build on them. I can then find the projects that most closely match my own priorities and use those.
I have no idea what this RedHat KDE cafuffle is about, because I chose to use Mandrake. Why couldn't the Mandrake people (or the SUSE people, or whoever) just work for RedHat instead? Because they have different ideas of how to make a distro.
We don't have a common vision, and this is a Good Thing.
GEORDI: Let's [technobabble] the main thrusters so that we can [technobabble] the Borg.
I heard a while back that Levar Burton was so used to technobabble that he would generally just ignore whatever's in the script and ad lib something, and his ad libs usually sounded better. Which makes sense -- he'd been spouting technobabble every working day for years.
Popups are annoying. They're a big part of why people use javascript for things that HTML does perfectly well, for one thing.
There is an HTML tag for "open link in a new browser window", I believe. Except that in that case, it leaves you with all your menus, browsing control buttons, scroll bars, window-resizing abilities, etc. etc. Too many times I've had an unreadable popup window appear because I'm using a bigger font than they expect and it doesn't line up with the graphics, but they turn off all access to scroll bars. Grr.
I don't understand why people force users to open things in new windows, anyway. Maybe this is just a feature of *n*x-based browsers, but with Mozilla, Netscape, and (my fave) Galeon I can middle-click to get a new window, and I often do; saves the reload that often comes with hitting the back button. But that decision should be mine, not the page author's -- if I'm not coming back to the original page, I'd rather open the new one in the same window. (Is this a middle-click thing feature of Windows browsers, too? eg. Windows Mozilla? I'm pretty sure IE doesn't do this...?)
As for tabs, they're handy for when I open a page that does have popups. The popups go in their own tabs, and I can safely ignore them (if they're ads or whatever) and just close the whole window when I'm done with the page -- the popups all vanish with everything else.
I don't know much about optimization for various languages, but I can attest that Fortran 90 has everything you'd really need in a language. It's not object oriented, but I've never needed that. It does do structures nicely, and it has nice looping features (like the ability to name loops) that help things to be clear. And it's got functions and subroutines and modules and things. Of course it's still possible to write illegible code, but it's actually possible to write good clean code, too.
(This is unlike Fortran 77, where for example there are certain tasks that cannot be performed without GOTO's. Ugh. It's got many other problems, too, even leaving aside the 6 character name restriction (since most compilers allow long variable names anyway).)
I couldn't tell you whether it'd be worth your while learning Fortran as compared to using other languages. I do know that there seems to be no (reliable) free Fortran 90 compiler for Linux (g77 does a good job with Fortran77, though, with a few exceptions). We're using a compiler from Absoft here at work, and it seems to work well.
My main point, though, is that Fortran 90 is not a bad language to use. It's not any more hideous than any other language, as near as I can tell; I've seen terrifying code in any language, and I've seen (and written) good code in F90.
Re:Serious Consequences fo InfoSec People
on
WarTalking Arrest
·
· Score: 3, Interesting
If you were in a bank with a locksmith, and he showed the bank manager that the locks they were using were insecure, the manager would thank the locksmith and change the locks.
If you're Richard Feynmann and you go up to the general in charge of the Los Alamos nuclear bomb research stuff and tell him (and indeed show him) that the safes all the top secret research is in are insecure and can be picked if you can get at it with the door open (which was relatively easy to do), the general would (did) order that all safes be kept closed when Feynmann is in the room...
Not everybody in power appreciates weaknesses being shown; nor do they always get the point you're trying to make when you demonstrate the weaknesses. This applies to any field.
For some reason, you people always seem to leave FORTRAN out of discussions like these. I just don't get it. It's like you never use it or something.;)
Well, for those like myself who are forced to beat their heads against the wall that is Fortran, there's a great introduction over at the Queen's Universoty of Belfast. So far it's told me all the basic syntax stuff I need, so it makes a really handy reference.
As for Fortran 77 [shudder] (and yes, I have to work with it regularly...), a search for prof77 readily yields a relatively tiny document that contains pretty much all the F77 information you'll ever need -- it's shockingly complete considering its size. I recommend finding a.ps version.
The requirements for de-mining during peacetime and during wartime are wildly different.
During wartime, you want to get the field cleared out as fast as possible, often because people are trying to kill you while you're clearing. So there's a balance between speed and thoroughness; after a certain point, the odds of dying from a missed landmine become worse than the odds of getting shot while clearing. I'm sure that's not the only thing, but the point is during wartime you need the field cleared fast, and it's "okay" if you miss a couple.
During peacetime, you can take all the time you need (well, to a point), but it is absolutely essential that you can guarantee you've found every single mine or nobody will use that field or whatever, and you might as well not have demined at all. For example, over at the Canadian military they're apparently working on a device that shines an x-ray beam down into the earth and looks for characteristic reflections from mines. They pass this device very carefully over every square centimetre of a field, and the idea is that this way they don't miss anything. But it takes forever.
I've heard of another technique where they genetically engineer a local weed so that it glows in the dark (or something) in the presence of certain fumes given off by mines. Seed the field with these modified plants, wait a season (so it's obviously not practical for military use), then look for the glowing bits...
For a long time I used Dvorak at home, but for various reasons I left my work machine on QWERTY. Eventually I got up to about the same speed with both layouts, but there was no advantage for Dvorak. (If I didn't have to keep switching I probably would have happily stuck with Dvorak.) There was a disadvantage: I would find myself pressing the same key twice for two different letters. That was a weird feeling.
So I just gave in and stick to QWERTY. It works well enough. And with the amount of typing I do, I'd have to wear these wrist braces regardless of which layout I use, I think.
I can easily believe the reports I've heard that Dvorak is easier to learn, though; if I forgot where a key was, I could remember just by thinking of where it would likely be. It's a very logical layout. The only reason I know the QWERTY layout so well is from so many years of use.
Of course, if the reason the case is off is so that you can point a desk fan at the innards, that's a different story. A friend of mine did this for a while, because the guts (drives, mostly) ran too hot; it apparently helped a great deal.
Cool. Makes sense. Is that how the "tesseract" xscreensaver hack works, or does that do something else?
It'd be cool to see it in something besides wireframe, though. If you did it for xscreensaver, I bet they'd start distributing it.
Both at the last apartment I lived and at the current one, I spoke to either the manager or the mail carrier and they put a little dot on my mailbox; this was a signal to the mail carrier and others that I do not want junk mail, flyers, etc. Now I get the occasional ad from something I'm already signed up for, but it's almost nothing.
The mail carriers are an understanding lot, at least here in Canada, it seems.:)
That's easy. Take a 4-cube. Pass it through 3-space, and what you'll see is an infinitely small cube at the point in the center of the 4-cube which will then grow to the cross-sectional size of the 4-cube, and shrink back down. Not too hard to wrap your head around. Tesseracts are a totally different matter...
I disagree. That nicely describes what happens with a sphere, but not so much with a cube.
I guess it depends on how it's passing through 3-space. The best way to imagine this stuff is to imagine a 3-D object passing through 2-space. If you pass the cube through corner first, you'll get something like what you describe, except the cross sections will be triangular most of the time. Edge on, you'll get rectangles.
Face-on, your 2-space will see nothing until the 3-cube hits it, then the 2-space will see a square just sitting there until the 3-cube is all the way through.
What's the difference between a tesseract and a 4-cube? According to Eric Weisstein, it seems they're the same thing.
I read the free introductory stuff on this site, and it was excellent. Resulted in my buying other Tad Williams novels, because I like the style and his writing ability in general. And the Shadowmarch site has all kinds of background information, really nice artwork, forums, etc, that do add a lot to the story.
THe only reason I didn't subscribe was because I didn't like the payment method. I can't even remember what it was, but I think it was PayPal only when I tried. (It was also hard to get at the "payment methods" screen -- I had to set up a login first.) It may be different now, but I never bothered going back.
It's just so much easier to go out and buy a book, I guess.:( Too bad, because it's a really good story and a very interesting project. And now people will say "look, online publishing doesn't work!" when it might (might) be a logistical issue.
Re:Is any of this real?
on
Quark Stars
·
· Score: 2
Physics is all lies. I'm not kidding. And no serious physicist believes otherwise. We just look at existing data and try and make up some theory that "explains" what we're looking at -- and by "explain" I mean "predicts results the same as the experiment gives". Good theories also suggest other experiments to try, and predict what those results should be. If the experiment gives the predicted results, we're a little happier to keep using the theory.
There's usually more than one theory (many, in general) to explain any given experimental result. And often several work equally well. Sometimes two theories give such similar results that you can pick whichever one's easier. (And that's usually what happens; this is what Occam's Razor is all about. Physicists are a lazy bunch.)
And of course a lot of our theories are only valid at low energy (for example), just like Newton's Laws. A lot of work goes into figuring out just how fast we can go and still call it "low energy" for a given theory, so we know how fast we can go before we need to go through the work of coming up with a more complicated, higher-energy theory. (Theories almost always get more complicated at higher energy, because more can go on. Just look at Einsteinian Relativity vs. Newtonian Mechanics!)
Physics is mostly approximations and emperical formulas. (Actually, the difference between a "law" and a "theory" is that a "law" is purely empirical -- it's the formula that best fits the theory, and was developed without worrying about the underlying mechanics. Deriving F=ma is a first year Physics lab, for example.:)
(And no, we don't really know that a given star/galaxy is 8 billion lightyears away. Measuring distances, especially at intergalactic scales, is one of the biggest problems in astronomy.)
Re:"Up" quarks and "down" quarks.
on
Quark Stars
·
· Score: 2
Does anyone know if all up quarks are the same as all other up quarks and if all down quarks are the same as all other down quarks?
Yup. I mean, there are a handful of "quantum numbers" like colour (three possible values) and spin (two possible values) that have been mentioned here (there might be other quantum numbers -- I forget offhand, and it depends on how you look at them anyway -- but there aren't many). But if two quarks have the same quantum numbers, they are indistinguishable. There are a lot of properties of matter that can be tested that depend on this indistinguishability, so we're pretty sure it's true; we don't have to see the quark itself very closely to know this (which is kind of cool, really).
(Sort of like how we know there are exactly three possible quark colours: certain reactions, for example, are more or less likely depending on how many possible colours there are. Yay, indirect measurement!)
Re:Building block of the universe binary?
on
Quark Stars
·
· Score: 2
As well, there are 6 "colors" that each could have - red, blue, green, cyan, magenta, and yellow.
Actually, there are only three colours, normally called red, blue, and green. There's also "antired", "antiblue", and "antigreen", but these are not cyan etc.
(But you can call them anything you like. Feynmann used to pick three colours from the flag of whatever country he was presenting in.)
Star Wars, love it to death, really isn't even pulp sci-fi, it's a trite story with sci-fi trappings that could just as easily been a fantasy, or a western or whatever.
There are very very few sci-fi stories that couldn't easily be fantasy stories.
I'm not sure I see how the second half of Star Wars (after Leia is rescued) could be a western, though.
What I'm really wondering, though, is what you feel makes the story trite. I mean, every story has been told before, especially if you simplify it into elements ("rescue the princess, defeat the evil army, save the world"). What makes this particular one trite?
So, if I play my CD's at a party I throw at my house, does the RIAA expect me to compensate for that?
Well, yes. At the moment I don't think they can force you to do so, but they'd sure like to. In their world, you'd pay per play and per ear. And they're working on it.
Around TRIUMF, where I work, we have a lot of monitors get "gaussed" by the cyclotron's magnetic field. Most monitors around there have some pretty rainbow effects. Turns out that the degauss button available on the newer ones works pretty well to fix them.
I'd still suggest not doing this deliberately, but if it happens there's at least hope of recovery.
Slashdot Mirror
So now you're saying that at least Newton's Second Law was not derived from anything; do I understand that right? If so, that's what I said the first time... F=ma (like Newton's other laws, and the c=constant thing) is purely observational, not derived from some other axiom. This is what I'm suggesting is the difference between a "law" (such as F=ma) and a "theory".
Really? Which principles? We were always told that, for example, F=ma is simply given; that's just what happens. Everything else is built up from that. (It's sort of an axiom.) You're saying that Newton derived F=ma from somewhere?
(Nitpick: neither Newton's stuff nor Einstein's stuff are based on basic mathematical principles. If anything, they're based on basic physical principles. The math is just a tool; the Physics is the meaty stuff. :)
I thought that was a neat way to look at it, anyway. I don't know if it holds universally...
I like all the options. Because of all the options, I get to use really useful, powerful systems, like FVWM2, Galeon, LaTeX, etc, rather than the more "mainstream" KDE/Gnome, Mozilla, OpenOffice, or whatever, all of which are much harder to use (for me) than the ones I do use. Different people feel different things are important, and they grab the bits of various projects that they like and build on them. I can then find the projects that most closely match my own priorities and use those.
I have no idea what this RedHat KDE cafuffle is about, because I chose to use Mandrake. Why couldn't the Mandrake people (or the SUSE people, or whoever) just work for RedHat instead? Because they have different ideas of how to make a distro.
We don't have a common vision, and this is a Good Thing.
I heard a while back that Levar Burton was so used to technobabble that he would generally just ignore whatever's in the script and ad lib something, and his ad libs usually sounded better. Which makes sense -- he'd been spouting technobabble every working day for years.
There is an HTML tag for "open link in a new browser window", I believe. Except that in that case, it leaves you with all your menus, browsing control buttons, scroll bars, window-resizing abilities, etc. etc. Too many times I've had an unreadable popup window appear because I'm using a bigger font than they expect and it doesn't line up with the graphics, but they turn off all access to scroll bars. Grr.
I don't understand why people force users to open things in new windows, anyway. Maybe this is just a feature of *n*x-based browsers, but with Mozilla, Netscape, and (my fave) Galeon I can middle-click to get a new window, and I often do; saves the reload that often comes with hitting the back button. But that decision should be mine, not the page author's -- if I'm not coming back to the original page, I'd rather open the new one in the same window. (Is this a middle-click thing feature of Windows browsers, too? eg. Windows Mozilla? I'm pretty sure IE doesn't do this...?)
As for tabs, they're handy for when I open a page that does have popups. The popups go in their own tabs, and I can safely ignore them (if they're ads or whatever) and just close the whole window when I'm done with the page -- the popups all vanish with everything else.
(This is unlike Fortran 77, where for example there are certain tasks that cannot be performed without GOTO's. Ugh. It's got many other problems, too, even leaving aside the 6 character name restriction (since most compilers allow long variable names anyway).)
I couldn't tell you whether it'd be worth your while learning Fortran as compared to using other languages. I do know that there seems to be no (reliable) free Fortran 90 compiler for Linux (g77 does a good job with Fortran77, though, with a few exceptions). We're using a compiler from Absoft here at work, and it seems to work well.
My main point, though, is that Fortran 90 is not a bad language to use. It's not any more hideous than any other language, as near as I can tell; I've seen terrifying code in any language, and I've seen (and written) good code in F90.
If you're Richard Feynmann and you go up to the general in charge of the Los Alamos nuclear bomb research stuff and tell him (and indeed show him) that the safes all the top secret research is in are insecure and can be picked if you can get at it with the door open (which was relatively easy to do), the general would (did) order that all safes be kept closed when Feynmann is in the room...
Not everybody in power appreciates weaknesses being shown; nor do they always get the point you're trying to make when you demonstrate the weaknesses. This applies to any field.
Well, for those like myself who are forced to beat their heads against the wall that is Fortran, there's a great introduction over at the Queen's Universoty of Belfast. So far it's told me all the basic syntax stuff I need, so it makes a really handy reference.
As for Fortran 77 [shudder] (and yes, I have to work with it regularly...), a search for prof77 readily yields a relatively tiny document that contains pretty much all the F77 information you'll ever need -- it's shockingly complete considering its size. I recommend finding a .ps version.
Probably... but then you'd be seeing bright spots everywhere...
During wartime, you want to get the field cleared out as fast as possible, often because people are trying to kill you while you're clearing. So there's a balance between speed and thoroughness; after a certain point, the odds of dying from a missed landmine become worse than the odds of getting shot while clearing. I'm sure that's not the only thing, but the point is during wartime you need the field cleared fast, and it's "okay" if you miss a couple.
During peacetime, you can take all the time you need (well, to a point), but it is absolutely essential that you can guarantee you've found every single mine or nobody will use that field or whatever, and you might as well not have demined at all. For example, over at the Canadian military they're apparently working on a device that shines an x-ray beam down into the earth and looks for characteristic reflections from mines. They pass this device very carefully over every square centimetre of a field, and the idea is that this way they don't miss anything. But it takes forever.
I've heard of another technique where they genetically engineer a local weed so that it glows in the dark (or something) in the presence of certain fumes given off by mines. Seed the field with these modified plants, wait a season (so it's obviously not practical for military use), then look for the glowing bits...
So I just gave in and stick to QWERTY. It works well enough. And with the amount of typing I do, I'd have to wear these wrist braces regardless of which layout I use, I think.
I can easily believe the reports I've heard that Dvorak is easier to learn, though; if I forgot where a key was, I could remember just by thinking of where it would likely be. It's a very logical layout. The only reason I know the QWERTY layout so well is from so many years of use.
Of course, if the reason the case is off is so that you can point a desk fan at the innards, that's a different story. A friend of mine did this for a while, because the guts (drives, mostly) ran too hot; it apparently helped a great deal.
Cool. Makes sense. Is that how the "tesseract" xscreensaver hack works, or does that do something else? It'd be cool to see it in something besides wireframe, though. If you did it for xscreensaver, I bet they'd start distributing it.
The mail carriers are an understanding lot, at least here in Canada, it seems. :)
I disagree. That nicely describes what happens with a sphere, but not so much with a cube.
I guess it depends on how it's passing through 3-space. The best way to imagine this stuff is to imagine a 3-D object passing through 2-space. If you pass the cube through corner first, you'll get something like what you describe, except the cross sections will be triangular most of the time. Edge on, you'll get rectangles.
Face-on, your 2-space will see nothing until the 3-cube hits it, then the 2-space will see a square just sitting there until the 3-cube is all the way through.
What's the difference between a tesseract and a 4-cube? According to Eric Weisstein, it seems they're the same thing.
THe only reason I didn't subscribe was because I didn't like the payment method. I can't even remember what it was, but I think it was PayPal only when I tried. (It was also hard to get at the "payment methods" screen -- I had to set up a login first.) It may be different now, but I never bothered going back.
It's just so much easier to go out and buy a book, I guess. :( Too bad, because it's a really good story and a very interesting project. And now people will say "look, online publishing doesn't work!" when it might (might) be a logistical issue.
I wonder if this Universal Translator will handle the canine language...
Oh, yeah. Good point.
There's usually more than one theory (many, in general) to explain any given experimental result. And often several work equally well. Sometimes two theories give such similar results that you can pick whichever one's easier. (And that's usually what happens; this is what Occam's Razor is all about. Physicists are a lazy bunch.)
And of course a lot of our theories are only valid at low energy (for example), just like Newton's Laws. A lot of work goes into figuring out just how fast we can go and still call it "low energy" for a given theory, so we know how fast we can go before we need to go through the work of coming up with a more complicated, higher-energy theory. (Theories almost always get more complicated at higher energy, because more can go on. Just look at Einsteinian Relativity vs. Newtonian Mechanics!)
Physics is mostly approximations and emperical formulas. (Actually, the difference between a "law" and a "theory" is that a "law" is purely empirical -- it's the formula that best fits the theory, and was developed without worrying about the underlying mechanics. Deriving F=ma is a first year Physics lab, for example. :)
(And no, we don't really know that a given star/galaxy is 8 billion lightyears away. Measuring distances, especially at intergalactic scales, is one of the biggest problems in astronomy.)
Yup. I mean, there are a handful of "quantum numbers" like colour (three possible values) and spin (two possible values) that have been mentioned here (there might be other quantum numbers -- I forget offhand, and it depends on how you look at them anyway -- but there aren't many). But if two quarks have the same quantum numbers, they are indistinguishable. There are a lot of properties of matter that can be tested that depend on this indistinguishability, so we're pretty sure it's true; we don't have to see the quark itself very closely to know this (which is kind of cool, really).
(Sort of like how we know there are exactly three possible quark colours: certain reactions, for example, are more or less likely depending on how many possible colours there are. Yay, indirect measurement!)
Actually, there are only three colours, normally called red, blue, and green. There's also "antired", "antiblue", and "antigreen", but these are not cyan etc.
(But you can call them anything you like. Feynmann used to pick three colours from the flag of whatever country he was presenting in.)
There are very very few sci-fi stories that couldn't easily be fantasy stories.
I'm not sure I see how the second half of Star Wars (after Leia is rescued) could be a western, though.
What I'm really wondering, though, is what you feel makes the story trite. I mean, every story has been told before, especially if you simplify it into elements ("rescue the princess, defeat the evil army, save the world"). What makes this particular one trite?
Well, yes. At the moment I don't think they can force you to do so, but they'd sure like to. In their world, you'd pay per play and per ear. And they're working on it.
Around TRIUMF, where I work, we have a lot of monitors get "gaussed" by the cyclotron's magnetic field. Most monitors around there have some pretty rainbow effects. Turns out that the degauss button available on the newer ones works pretty well to fix them.
I'd still suggest not doing this deliberately, but if it happens there's at least hope of recovery.