Here's an example of what happens when you try to put 2000 entries in your $PATH:
Fermilab's computing division made an interesting effort to solve the problem of a cluttered/usr/bin directory. Their primary objective, I think, was to allow for users to choose between multiple versions of various programs. The result was UPS/UPD. I think this system was based on a kind of "setup" utility from VMS, but I'm not sure of the details. You "setup" a product, optionaly giving a version number. This is sometimes important when a newer version of a product is not entirely backward-compatable. One good example is the early versions of the Tcl/Tk interpreters.
I don't think this is an ideal solution by any means. You can quickly end up with an extremely long $PATH, and exceed the built-in limitations. Besides, putting all this in your $PATH is a shell-dependant approach, which has many disadvantages. You also have to setup every program you are using, whether you know you are using it or not. There are problems with dependencies, and all sorts of other stuff.
Even so, I have not seen any other solution in Unix to the problem of maintaining multiple versions of a product.
This post is long, because I just had to rant about a few related topics. I apologize.
It's not because I'm uncomfortable with Windows or anything. It's just that I type much faster than I can click around. Also, I tend to access lots of files. My typical directories are about 3 levels deep (below my home directory), but still contain a couple hundred files each. Today there are over 64,000 files under my home directory, ~99% of which are less than 4 years old. There are all sorts of files in any given directory such as source code, executables, scripts, data files, plots, object files, specification files, etc. I do have problems remembering names of files in the long term, but throughout the week I can easily remember what I'm doing.
I agree with the basic idea that we need some kind of new interface or structure to improve things. We probably need to go beyond the simple directory tree structure, or at least augment it significantly. But I also think that these GUI file browsers are a step back from the command line. It's a step so far back that the distance cannot be regained by more sophisticated GUIs.
With this many files, a GUI system is absolutely hopeless! Whenever I have to find a file in some directory with a Windoze file browser, it drives me nuts! I can spend roughly 10 seconds scrolling through and searching for a file I want, while I could type it in about 1/2 sec. That's more than an order of magnitude faster than the stupid mickey-mouse method!!! I wish there were more samba client command-line interfaces, so I could easily copy a local file in Linux over to a samba share on another computer. smbmnt is nice, but I don't have root permissions on the system of interest.
And what can you do with files with your mouse, anyway? Not much! You can copy/move/link, rename if you're patient enough, or "open" which is some action that's the wrong thing half the time. Okay, drag and drop is good, and still has some untapped potential, but still with the mouse your options are extremely limited compared with the command-line interface of a good Unix shell.
All of this time-ordered stuff just amounts to "ls -ltr", which takes a whole lot less time than clicking on anything with a mouse. And the ls command is far more powerful since you can pick out file types with globs, or more complex filters with egrep, or whatever! Now, admitedly this only works in a particular directory, and there we can do better, but this is still vastly superior to any mouse-driven interface like the ones in the article.
The Unix find command is unfortunately very useful, and the interface is extremely akward. Actually, I feel that VMS's search command is even a little better than find. locate | grep can work well sometimes.
What we really need is some kind of cross-indexing. Perhaps there still needs to be a primary filing system, or directory tree. But this could be augmented by other systems that organize files in different ways, mostly automatically. It's hard to think of all the details, but there should be some kind of small find-file dialog/popup that narrows down possible matches as you continue to add information, like typing in the file name, or looking for a range of dates, or a certain file type or application, or topic. The shrinking list should probably remain time-ordered by default. I can imagine adding this kind of capability to Konqueror for those people who still need visual file representations as a crutch to help them get through their crawl (pre-toddler) stage. But hopefully it could also be added to a command-line interface somehow.
Also, the concept of a working directory is quite powerful, and needs to be taken into consideration. When I work, I typically am using 1-4 directories at any given time, which is easily and logically handled by having multiple terminal windows. I also use the directory stack on occasion, and "cd -" a lot. It's faster than reaching for the mouse and changing windows. If files can be cross-referenced by topic, then perhaps a "working topic" concept could be useful?
Why did they have to pick such lousy examples of American pop culture? Stuff like Independence Day and Temptation Island isn't culture, it's cultural abuse for profit! It ashames me that this is the kind of stuff they are now yumming-up in Kabul, since it is the worst example of American culture IMHO.
The price we pay for a free society in an information age is that we gradually build up resistances against media manipulation and other trash like this. For example, those happy-go-lucky commercials of the 60's and 70's seem ludicrous and silly to us these days, just bouncing off our thick armor of skepticism. But 30 years ago those commercials apparently worked!
After some years of isolation, the people freed from Taliban rule may be hungry for all the trashy sensationalism that abounds in our society. But they may be lacking the ability to recognize the more subtle manipulation and propaganda prevalent in US media and pop culture.
Or, maybe not. What do I know, I haven't lived in Afghanistan myself. Maybe these folks know how bad and stupid these movies and shows are, and are just watching them because they embody the those qualities thought "evil" by the Taliban. Even so, I am genuinely embarrased by this.
"I took the older VM plus fixes Rik felt would solve all the problems. Linus took Andrea's work. Right now, as of 2.4.14pre, Andrea's VM seems to be beating the pants off Rik's VM. All the current numbers suggest it's the better path."
Hey, I thought slashdot cited a comparison of the (fixed) Rik VM and the AA VM, and came to the conclusion that they performed about the same! They were both MUCH better than the 2.2 (old Rik) VM. What's Alan's evidence that the AA VM is "beating the pants off Rik'v VM?" If they really do perform about the same, I would have to side with Alan's original decision to just patch the old VM.
I think that you have to be careful not to give up too soon when it starts to get tough. It's natural to start feeling restless when you are genuinely being challenged. On the other hand, that's also a natural reaction when you aren't being challenged enough.
Instead of asking yourself how you feel while actually doing the programming, ask how you felt about it once you finished some project. And focus on your favorite CS classes instead of your least favorite ones. In general, if you're searching for what it is that you really enjoy doing, look at your most positive past experiences and compare these with similar experiences in other fields. This is a much more accurate and insightful comparison.
Although it's possible to do well financially after grad school, I'm not sure that it's the norm. I'm not in CS, but now after getting my Ph.D. in physics I am beginning to realize the fantastic opportunity cost of it.
Yes, you can get a stipend and tuition waiver, but no matter where you go you will be living close to the poverty level. This condition will last several years (average in physics is 6-7 I think, and it took me just over 8). During that time you won't be accumulating retirement savings, if you're married it's even tougher, and you won't be paying off your undergrad loans.
Compare that to spending 6-7 years working at some company. At the end of this time, you could be earning well over what a fully-tenured professor makes at the end of their career. You'll have paid off most of that college loan, and probably begun saving a large amount of money. Compared with the grad school track, you're doing very well! The difference may be close to a million bucks!
After grad school, you could probably get a better job than the one you would have started fresh out of college. But since then you would have made your way "up", and you would be earning the same amount as most grads do. So 6-7 years after the undergrad degree you would be earning approximately the same whichever way you go.
I'm not recommending against this. I'm still glad that I did it. But money is a big consideration -- grad school is an enormous sacrifice. You have to really want it, and be passionate about advancing the field. If you can't imagine yourself doing anything else, only then would I recommend grad school.
I agree with this completely, except that I read the original post as a question of reliability or accuracy of the commodity hardware.
Calibrating any device is important, and I love the laser printer idea for positional calibration. I think other posters responded to the intensity aspect of this.
One problem is that, for digital cameras, most are automatic and set F-stop, shutter speed, and do color corection and sharpening afterwards. You don't want any of this post-processing, and you need to know the shutter speed and F-stop (or their equivalents). I don't know enough about the market to say where these are available or not. I guess if you can't control this directly, then you'll have to include calibration data with every photo as part of the "scenery", as if each photo were taken with a completely different camera with different properties. I have a great book entitled "CCD Astronomy" which, while it isn't exactly on topic, covers the basics of image processinig and calibration very nicely. I don't have the book with me now, so I can't tell you what the author is. I used this book as an undergrad in physics while working on a CCD camera as a research project. It was very accessable to me.
But the main thing you're after, I think, is the accuracy of the device, after it's been calibrated. I think this is based on two factors, the actual pixel sizes/bit depth, and the accuracy of your calibration factors. Something like pixelsize/sqrt(12), added in quadrature to the calibration errors. Estimating the accuracy of the calibration is an interesting business, and there are a variety of ways you could do it. Taking multiple calibrations and finding the statistical spread (RMS) is an easy way, but only gives you a lower bound because there will be systematic errors in your calibration procedure. I'll leave it at that. Probably any intelligent, hand-waving approach to estimating these systematic errors is enough for a senior project. A really thorough approach could take much more time than you have, generally speaking.
I've been reading through Lord of the Rings, and just last night read the part about Wormtongue, an evil agent doing mischief as a sly king's advisor, skillfully mangling the truth. Comments from MS sound just the same.
"We are going to support the latest versions of Opera and Mozilla so people will be able to get the MSN experience," said Bob Visse, MSN's director of marketing.
But, Visse warned, "the experience may be slightly degraded simply because they don't support the standards we support closely, as far as the HTML standard in those browsers."
...
Visse said earlier Thursday that the message would be shown to people using "browsers that we know don't support (W3C) standards or that we can't insure will get a great experience for the customer." W3C refers to the World Wide Web Consortium, which is developing industry standards for Web technologies.
Wow! They've left the door wide open with that last statement, especially. They can't "insure" (ensure) the performance of any software not directly under their control! Sooo, they are really saying that "we don't recommend using any software but ours." Well, of course!
What really irks me is that internet-savvy folks will realize this FUD tactic for what it is, and hate MS even more for it (which isn't even possible, so no damage done). But 95% of the public will take the message at face value, think that non-MS browsers are flaky, and that people like us who disagree are self-deluded fanatics. So MS "wins."
I think the truly evil thing that MS is doing here is blocking other browsers, or even warning the users that their "experience" will be less than perfect. These other instances you mention are probably not malicious errors, they are more likely accidental ones. MS's web pages are maliciously broken.
This is classic FUD!
The main problem here is that Joe Newbie will take it at face value. He won't realize that Mozilla, for instance, is more standards compliant than IE and that MS is breaking their web pages by using MSHTML and blocking the better browsers on purpose. He won't realize that you can change the browser string by just one letter and view the web pages with no problems. He will instead think that these other browsers are inferior -- the opposite of the truth.
You're right, this article claims at first to present a meaningful comparison, but it completely misses any and all meaningful comparitive points. The article is entirely based on three unsupported assumptions. Here's how I read it:
1) Linux is cheaper than Windows and Windows + comercial apps cost roughly 20% of the hardware.
- The first point is fact, but the 20%-ish part is made up. Probably right anyway, but I don't know.
2) *nix is easier to administer by a factor of 8
- I don't believe this. Those sys. admins I know who deal with both like Windows better. However, they do spend more time administering Windows, but that's only because they've put it on everyone's desk. My best guess is that the two OSes are equally time-consuming to administer by a competent person.
3) Windows crashes on a daily basis, while *nix systems never crash.
- This is crazy. In my experience, Windows NT is slightly more prone to crashes than Linux, but running on good hardware it's rare to see a BSOD more than once a year. The stability of these operating systems is a non-problem, compared with stability of application software and even hardware. Netscape/Mozilla in Linux is no more stable than Netscape/Mozilla in Windows. Emacs might be more stable than MS Word, but generally speaking it's the software stability that causes the most problems.
So, where's the evidence to support these statements? There are a lot of hypothetical numbers given, but they are just consequences from the underlying bogus assumptions.
Where's the interesting information? Are cost and reliability really the major concerns? How about usability, popularity, productivity, educational value, etc? For a school, you might want students exposed to a variety of systems in order to better prepare them. Learning MS Word version 200x is not nearly as useful as learning Word, StarOffice, and maybe LaTeX. Variety gives you more basis for abstraction and allows you to learn new software much more quickly. Unless you're a technical college, you should be more focused on building strong learning frameworks than teaching specific skills for now-current technology.
For a business you're more concerned about productivity, so do the applications offered on a particular platform suit your needs? I'm sure that secretaries prefer to use Word than, say, Abiword. So give them Windows. Excel is probably better than gnumeric. But I like Perl+gnuplot better than Excel for most middle-weight data anlsysis tasks.
Okay I'm obviously just rambling here, but to me these are the really interesting issues. Cost is kind of important, both licensing and administration costs. But I don't think it's the biggest issue, really. And certainly stability is not much of a concern except for servers. If you're a major banking institution and you want totally secure, stable servers, then don't use Linux, Solaris, *or* Windows. Try something like VMS!
Anyway, this was a truly vaporous article, not worth posting.
In my experience, Windows NT 4.0 is very stable, almost as stable as Linux can be. I've been using Windows NT 4.0 ~8 hours a day for the past 5 years.
I began to see frequent (about once a month) BSOD's on one computer that was really being pushed to its limits. It was a 200MHz PII w/ 96MB RAM. It was already swapping after I would log in, before running any major apps. Now I'm using a newer computer (well, about 2 years old now), with 128MB RAM. It could definately use more RAM, especially these days with it so cheap, but after 2 years of use I have NEVER seen a BSOD.
So most of this depends on hardware stability, and what software you use. I use Windows very lightly, primarily using exceed and connecting to OSF1, Linux, AIX, IRIX, etc. Even so, I do use several other windows apps frequently such as web browsers (Mozilla these days, Netscape previously), MS Office, Corel Draw, music players, and such.
Netscape and Mozilla crash a lot, and some of the most damaging crashes are when I'm writing mail in Mozilla, have to look something up on the web, and the browser crashes -- bringing down my email composer along with it. I'm getting in the habit now of launching IE just to browse while writing long email messages, so that a browser crash won't kill my unsent message. I also use IE to browse Microsoft's web pages and ibuyer.
Exceed crashes often too, but even when exceed crashes, it's very unlikely for me to loose more than a half-hour of work because everything is either on disk or edited in emacs. I would rather just run Linux on my machine, but that's not my choice to make.
I have to think that those of you who see so many BSOD's running Windows are either pushing old and flaky hardware to its limits, or are running tons of buggy software.
On the other side of the spectrum, the old Mac OS's were horrifically unstable, and seemed to crash once every 2-3 hours no matter what hardware or software you were using. And these days Windows 95 and 98 give me about a crash a week at best, sometimes more.
1) The point of grammar-based prejudice is a good one! I think online communications (email, message boards, chat rooms, IM, multiplayer games, etc) actually exacerbate the situation. Since text is often the only clue we have about other people, I end up making a lot of assumptions about others by their writing style. Assumptions about age and education, primarily. The fact that my assumptions prove correct more often than not strengthens this instinct. But is this another form of prejudice?
2) While I enjoyed the test, it always aggravates me when people equate salary with success/prestige. I've just finished my Ph.D. in physics, and am looking at jobs now. There appears to be a major fork in the road, where I need to decide to go into industry or acadamia. I could be challenged and happy either way, but it's a difficult decision. My feeling is to stay in academics, because I feel a strong affinity with the whole academic process of teaching, research, and open sharing of knowledge. But jobs in the industry typically pay two to three times more than academic jobs, just starting out. And later on the academic salaries quickly asymptote while salaries in the industry have practically no limit. From a purely financial perspective, the decision is absurdly obvious.
So my future salary is not determined by my grammar, grades, or whatever. It's determined by my priorities. I would say "greed/ethics ratio", but that's too smug. So I won't say that.;)
I also aggravates me when people talk about intelligence like it is some kind of metric. I personally don't think that intelligence can be measured in any meaningful way. Grammar, intelligence, and salaries are not like inches, centimeters, and cubits. They are related more like sweetness, color, and temperature of food are.
Even with "trace amounts of iron" a magnetic effect would vary with the square of the distance. But what do I know?
Different radiation patterns will vary with distance in different ways. Uniform radiation falls off as the square of the distance, but beamed radiation does not. All that this guy has shown is that the radiation is beamed. There's no new physics in that.
I briefly touched on this while writing a post earlier, but it's been bugging me more and more so I feel the urge to elaborate. The guy does something involving extremely high currents over short periods of time (read: powerful electromagnetic radiation source), and somehow attributes this to a quantum anti-gravity! It's easy to criticise Podkletnov's experimental technique, but this logical leap is so flawed it's hillarious.
He writes: If the effect is truly gravitational, then the acceleration of any test body on which the impulse acts should be in principle independent on the mass of the body.... Here, however, we encounter a conceptual difficulty. (The difficulty lies in the author's inability to use reason.) Suppose [we put in the beam] a very massive pendulum. If the effect is gravitational (an unsupported and ludicrous assumption to begin with, but allriiiight) then the acceleration of a test mass should not depend on its mass. However it is clear that in order to give this mass the same oscillation amplitude of the small masses employed in the experiment, a huge energy amount is necessary, which cannot be provided by the device. Therefore the effect would seem to violate the equivalence principle.
There are at least two gaping problems with this logic, which is actually the springboard off which the author launches into 20 pages of pointless theory. First, it's a ridiculous extrapolation. He observes some (inconclusive, I'm certain, though he presents no data) evidence that the impulse given to the test masses is proportional to their mass. This means the energy absorbed by the free objects is proportional to their mass. Then he conjectures that a really large mass must do the same thing (by extrapolation), at which point it absorbs more energy than he has put into the pulse in the first place. I hope this logic sounds as bad to you as it does to me!
Then he cites it as a violation of the equivalence principle. It's really a violation of conservation of energy, which is by all accounts impossible. Even the quantum gravity theory he appeals to requires conservation of energy, as do virtually all possible physical theories. The equivalence principle simply doesn't apply to this situation, and even if it did, it would be satisfied. This principle only applies to the limiting case of a uniform gravitational field. On small scales, the gravity field near the earth is uniform enough. But his claimed effect would be highly non-uniform. Second, the equivalence principle is basically that the gravitational field is equivalent in every respect to an accellerating reference frame -- which explains why gravity fields produce a force on a body proportional to its mass.
Even though this paper uses a lot of big words (often misspelled), it is by no means scientific. The author conveniently ignores all the reasonable explanations for his radiation, presents no data whatsoever to support his claim that it's a gravitational force, and merrily plunges into a thoretical discourse having no bearing on reality.
Of course, this result looks a little fishy to me, too. First, like others I want to point out that this result is not "published", so the original post should be ammended. Anyone can put a paper up on xxx.lanl.gov. Second, the only reason I would guess this is not a complete hoax is that hoaxers don't usually go to this much effort. But I can't really tell.
It's disturbing that the title of the paper mentions a gravitational force, and throughout the author refers to his radiation as a "gravity impulse". This is a premature, biasing assumption, and it makes the entire paper distasteful to read. A gravitational force would be the last thing I would imagine attributing to this effect, which is obviously electromagnetic in origin.
I have no concerns that he somehow set up the experiment "incorrectly". If this is not a hoax, then whatever he did to create the radiation is fine, as long as it's described well enough for others to reproduce. However, his tests of the radiation are biased toward the idea that it's gravitational and not electromagnetic. He does not use antenae and plot the frequency spectrum, for example.
There is no table showing the various materials used, at various distances, and the relative effects of the pulse on them. Because the pulses are not very uniform, many materials should be simultaneously tested. What is the confidence level of the hypothesis that various materials experience the same force, proportional to their mass? He only says that it's true, but doesn't show any data!! This is not even close to science. It's more like wishing real hard. If I were a reviewer of the article, I would ask for much more data to be presented.
Section 4b of the paper is highly flawed. Really, what evidence does he present for the case that this is not garden-variety E-M radiation? He says the force is proportiaonal to mass and mostly independant of material (without showing the data which may be perfectly consistent with other hypotheses). Fine, but the atomic charges are going to be proportional to mass, also, so it could be a high-frequency kind of thing. He should test it on, say, different isotopes of the same element. Or lead vs beryllium, to get a decent range. He says that electromagnetic shielding doesn't attenuate the radiation. Okay, if you say so, but please, what kind of shielding did you try? Did you use a conductor, or mu-metal? How large? How much? To what accuracy did you test this? Magntic fields are extremely penetrating, and a Farraday cage doesn't help. I know, my office is one floor up and one room to the right of an 8 Tesla magnet, and I can't put any computer monitors in the Southern half of my room!
Then in 4b he has some completely lunatic argument that his "new force" is not consistent with GR, because if he extrapolates the effect way beyond the range he has tested, he comes up with a violation of conservation of energy. "My tiny test balls received kinetic energy proportional to their masses, so logically, if I put a wrecking ball in the way it would absorb more energy than I put into the pulse! Ha!" He calls this a violation of the equivalence principle, which is absolutely wrong. It's a violation of conservation of energy, which is technically equivalent to saying that the laws of physics change from day to day (that time is not a valid symmetry).
Then the rest of the paper goes into theories of quantum gravity and stranger stuff, which is most certainly not proven physics (not that I don't believe it, but come on!). I didn't read any of it, because I would rather read good science fiction than bad science fiction.
Assuming this is not a hoax, I would be mildly interested in seeing a proper analysis of this high-energy E-M pulse. But there's enough genuine and important scientific research that is getting its funding slashed in the US (thanks, Bush!), so I hope experiments like this don't get more attention than they deserve.
I just bought a CD which I had completely downloaded in MP3 format (through gnutella), and was very impressed with. So I would answer to the survey that, yes, I would buy a CD that I downloaded music from. But on the other hand, I probably would have bought a CD at that time anyway, so gnutella downloads simply helped me make that decision. I'm certainly glad I bought the CD since there is so much more to hear that doesn't come through on MP3's 128 kbps quality. I'm not a raving audiophile, but I'm not deaf either. Somewhere inbetween.:-)
But will gnutella/Napster cause me to buy more music than I would ordinarilly? Maybe -- it allows me to sample a larger diversity of music, which might get me to buy CDs I wouldn't buy ordinarilly and thus inspire more of an appetite for music. Or, maybe I'll just find out that the CDs I've been considering really don't sound as good as I hoped. I think the former scenario is more likely, but I honestly don't know the answer, even for myself!
So this should make it obvious that any kind of survey like this one is not going to disclose any truth about whether or not Napster is helping the music industry. Also the major source of bias in a survey like this is: Who's choosing to take this survey? It's obviously people who are familliar with Napster, as the first statistic showed. It's probably also people who think Napster is good, and want to "prove" it. So even if the survey questions were insightful it still wouldn't mean anything.
I also hated the comments about the music industry needing to be more selective, supporting only a couple dozen artists! I agree with the general conclusion that the music industry should be worried about things other than Napster, but I think the music industry is much too limiting rather than permissive, way too comercial and concerned only with the bottom line.
I think the best music is the stuff that would never be released as a single. The bad songs are the ones that you instantly like the first time you hear them, and get tired of quickly. These get airplay because the execs are listening only for that instantly-appealing hook. The good songs are the ones that take some time to grow on you. These are stamped out by the industry as much as possible.
I agree, and think the Voyager estimate is valid.
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I agree, this is at least the right spirit of how warp speeds work. I vaguely remember reading some kind of functional description about warp speeds in some kind of writer's technical guide to ST:TNG. I don't recall the exact function, but the function has a pole at warp 10, so as the warp number approaches 10, the speed approaches infinity.
So you need some kind of function like speed = 9/(10-WarpNumber) c
I don't think that's exactly the right function, but it's something kinda like that. Actually I think the real function is more "decimally inspired" and artificially exponential, but I don't remember just how. In any case, warp 1 is the speed of light, and at warp 10 you "occupy all points in space at the same time."
Another important aspect is that, even if flagships like the Enterprise can exceed warp 9, they can't cruise at that speed. Cruising speed is perhaps more like warp 4--7 for voyager, I'm not sure exactly. It's whatever speed they can sustain for long periods of time.
So if the Milky way is about 100,000 light years across, and Voyager is on the opposide side, and they can't go straight through the center because of various astrophysical hazards, maybe a 75,000 ly journey is about right. So to make that in 75 years, they have to be going 1000 times the speed of light. I don't know what the cruising speed of Voyager is, but 1000 x warp 1 seems "reasonable" (whatever that means in SciFi).
I agree with this, though the life-or-death status of an OS can sometimes be a tangible and important thing, the main problem with this article is that it doesn't provide any actual information at all! All he's saying is that Linux has not magically overcome all it's user-friendlness issues in the last couple months. He's certainly not the first person to observe this! And then he tries to decorate the truth by proclaiming some kind of judicial status for himself and declares that Linux on the desktop is "officially" dead. What does this mean? Absolutely nothing. It's pure transmission noise on the internet.
"Dead", for an OS, means that nobody is writing new applications for the OS or supporting new hardware. A dead OS is one that's falling so far behind the forefront of application development that it becomes practically useless.
MSDOS is dead. VMS is probably not dead but may be close in spite of a few yet-unmatched technologies. Mac OS is not, and neither is Linux by a long shot!
What Linux has going for it is easy to underestimate. It's a true community project -- a great development platform because of its freeness. IMHO it has more potential than any other OS because the software and libraries being written today are the building blocks for tomorrow's software, and so on. This cannot happen for proprietary environments like Windows since this level of sharing is not encouraged.
Yeah, I'm one of those many users who has a dual Windows/Linux desktop. My wife and I use Windows for things such as Quicken, Cakewalk, Finale, and games. But I use Linux for everything else - web browsing, ssh, development, analysis, basically everything related to my research work. I don't have a problem with this division! Use the right tool (or OS) for the right job. I use Windows NT with Exceed connecting to Linux+OSF1 at school, but I would much prefer the Linux desktop because it is much more configurable and I feel much more productive. So many of the apps I use are supported naitively in Linux and not Windows. I would say that my own needs are different than the "average user", but there is no such thing really. For myself and a great many others, Linux is not just a viable alternative for a desktop OS, it is the superior one by far! Linux is not dead, but growing and thriving.
This becomes a serious question if you consider things like gigabit ethernet. We're also starting to see some hardware out there that makes IDE raid systems a little more reasonable.
I looked into this a little bit for my research group at UIUC. We were wanting to buy some more disk space, somewhere between 400GB and 1TB. There were two options I considered.
Buy a bunch of SCSI disks and put them in our existing SCSI controller which has some free space. We would get a set of 6 drives, either 70GB or 160GB each. One would be redundant.
Buy an IDE raid server and run Linux on it. We could connect 6 80GB IDE drives to a 3ware IDE SCSI card or some such thing. Since IDE drives are about 1/4 the cost of SCSI drives, and 6 80GB drives cost about the same as the computer to support them, this ends up being half as expensive per GB. Some collaborators at Vanderbilt
did this a year ago.
In our situation we wanted to be able to process data as fast as possible. We have a growing collection of dual-PIII "compute servers" and divide our data amongst the computers. Typical jobs will run on a dozen of these computers (24 CPUs) and rip through data in either minutes, hours, or even months depending on the job. We are often I/O-bound.
We went with the SCSI disks for a few reasons:
SCSI disks have their own internal cache and can read or write chunks out of sequence to minimize head travel. We were only guessing that this could be a big deal since we were often reading and writing a few dozen data streams at once, saturating the server. But we haven't done any tests so I don't know how big a factor this is in reality.
SCSI disks were hot-swappable - no downtime.
This solution is more scalable and convenient. One doesn't want to manage several disk servers if it's not necessary.
Our Sys. Admin. insisted, for these reasons and more.
Of course without the infrastructure of our existing RAID box, the economy would slant much more toward the IDE RAID solution. And for a home environment I think smaller-scale things like the ABIT KT7A-RAID card might also become very handy. Last I heard, the RAID controller it used wasn't fully supported in Linux, but that information is probably out of date by now.
We are currently using OSF1 for our server instead of Linux primarily because of the advanced filesystem: a 64-bit filesystem, ACLs, partitions that span multiple disks, and so on. It's good to hear that most of these advantages are now available to Linux, and XFS looks extremely promising. Keep up the good work, everyone!
I won't flame you because the vast majority of people, even with your level of math education, would agree with you. You're wrong about math, of course, but I think most of the blame lies in the way mathematics is taught. (I don't mean to suggest that I have a solution to this problem, either.)
I like to think of math as a language. For one, it's a way of communicating ideas both abstract and concrete. Also like other languages, it provides us a conceptual framework which allows us to understand things better. And finally it's a powerful tool when you learn how to manipulate it.
Much of our math education is just the manipulation part of math, which is useful but never by itself (except on tests, as you said). Learning to describe and understand things mathematically is at least as important. With these three aspects mastered, mathematics becomes indispensable to whatever you do. Well, except for sex -- but other than that, it's pretty useful.
I really like the ability to download music from peer-to-peer networks, and I think it could even be good for the recording industry. Here's a typical scenario for me:
First, I actually hear a new song on the radio and think it's not too bad. Yes, this does actually happen once every month or two. If the artist is good, then it's always the worst songs on an album that get any airplay, so I would probably want the album for the other songs. Or if the artist is bad, the other songs will be a similar tripe and I won't be interested.
Next, I can download parts or all of the album from napster or gnutella. I'll soon find out whether or not I like it. If I really like it, I'll buy the CD because I can play it in my car or home stereo which are both much better than my cheap computer speakers.
I also think the idea of buying a CD just for one song that you've already heard is crazy. The really good songs are the ones that take time to appreciate, and you never hear those unless you get the whole CD. But if you're a "professional student" like me, you won't be able to afford buying CDs very often, so you have to be choosy. Napster and gnutella help me do this. In fact I'm surprised by how much more music I like because of this.
I've seen an overwhelming shift in experimental particle physics from other flavors of Unix into Linux over the last few years. I think the main reasons for this were the no-cost Linux license and way the PC hardware has become almost as powerful as the Sun, Digital, SGI, IBM, and HP workstations yet much cheaper.
This may be a foreshadow of industrial trends to come with the present economic recession because, for the past 8 years or so, particle physics has been in a major recession of its own. After suffering 20% cutbacks in Department of Energy funding over the last few years, we got a 5% cut last year, and rumors of a 15% cut this year are very
threatening.
Other reasons for basic research programs to switch to Linux include security of having the source code, and the way that the free software movement is consistent with the philosophy of our research. Scientists can get very fearful of any software that's not under their control, so having the source code gives a kind of reassurance that their computing platforms won't break in some way that can't be fixed. And also the basic goal is to increase public knowledge, not to create intellectual property. (I sure am glad I don't need to pay royalties to Einstein's great grandsons every time I boost particle trajectories from one reference frame to another, or compute invariant particle masses.) So it makes sense to use, and develop as the need arises, free software whenever it's feasable.
Okay, I'm getting further off topic, so I'll stop.
As I understand it, the degeneracy pressure works like this:
The "seats in the classroom" you refer to are particular values for the momenta of the particles (electrons in the case of white dwarfs) in some volume. So as you try to compress the material, in you're adding more particles to any given volume of the stuff. These particles must pick discrete values of momenta that aren't already "taken", so they must be fast. All of the lower momentum seats are already taken, if you consider a white dwarf to be "cold". Even though a white dwarf is very hot in ordinary terms, it's "stone cold" for these purposes because the pressure due to temperature is much less than what's needed to compete with gravity.
So the more dense the white dwarf becomes, the higher the average momentum of the electrons must be. This average momentum translates into pressure. So even though the white dwarf is not hot enough to support itself against gravity by ordinary classical gas pressure, there is a minimum pressure of the gas that comes, basically, from the Pauli exclusion principle.
As you increase the pressure more and more (we're considering more and more massive stellar cores), the electrons you're forcing into a given volume will need to adopt larger and larger values of momentum. Eventually the momentum of the electrons will become larger than the rest mass of the electrons, and they become "relativistic" (moving very close to the speed of light). In this case, as you add more electrons and increase the average momentum, you aren't actually increasing the speed of the electrons by much -- they're already going (very nearly) the speed of light. At this point, the pressure doesn't build up as quickly with density, and "gravity wins".
So if the core of the star is massive enough, the force of gravity will overcome this electron degeneracy pressure, and you could be left with a neutron star or a black hole. In the case of the neutron star, the protons and neutrons (also spin 1/2) will get close together and create their own degeneracy pressure. If the density is so great that the protons and neutrons become relativistic, it will collapse into a black hole (well, that's the best theory anyway). The protons and neutrons need a much higher momentum to move near the speed of light, because their mass is about 2000 times greater than the electrons.
For even more complicated reasons, many of the protons and electrons in a newly-forming neutron star will interact to form neutrons and neutrinos. The neutrinos leave, cooling the core and helping out with the supernova. The neutrons stay behind of course, forming a large percentage (70%?? I forget) of the composition of the neutron star, hence the name.
I hope this helps! I guess the short answer is that special relativity spells doom for massive would-be white dwarfs (or would-be neutron stars).
Slashdot Mirror
Fermilab's computing division made an interesting effort to solve the problem of a cluttered /usr/bin directory. Their primary objective, I think, was to allow for users to choose between multiple versions of various programs. The result was UPS/UPD. I think this system was based on a kind of "setup" utility from VMS, but I'm not sure of the details. You "setup" a product, optionaly giving a version number. This is sometimes important when a newer version of a product is not entirely backward-compatable. One good example is the early versions of the Tcl/Tk interpreters.
I don't think this is an ideal solution by any means. You can quickly end up with an extremely long $PATH, and exceed the built-in limitations. Besides, putting all this in your $PATH is a shell-dependant approach, which has many disadvantages. You also have to setup every program you are using, whether you know you are using it or not. There are problems with dependencies, and all sorts of other stuff.
Even so, I have not seen any other solution in Unix to the problem of maintaining multiple versions of a product.
I prefer the command line, too.
This post is long, because I just had to rant about a few related topics. I apologize.
It's not because I'm uncomfortable with Windows or anything. It's just that I type much faster than I can click around. Also, I tend to access lots of files. My typical directories are about 3 levels deep (below my home directory), but still contain a couple hundred files each. Today there are over 64,000 files under my home directory, ~99% of which are less than 4 years old. There are all sorts of files in any given directory such as source code, executables, scripts, data files, plots, object files, specification files, etc. I do have problems remembering names of files in the long term, but throughout the week I can easily remember what I'm doing.
I agree with the basic idea that we need some kind of new interface or structure to improve things. We probably need to go beyond the simple directory tree structure, or at least augment it significantly. But I also think that these GUI file browsers are a step back from the command line. It's a step so far back that the distance cannot be regained by more sophisticated GUIs.
With this many files, a GUI system is absolutely hopeless! Whenever I have to find a file in some directory with a Windoze file browser, it drives me nuts! I can spend roughly 10 seconds scrolling through and searching for a file I want, while I could type it in about 1/2 sec. That's more than an order of magnitude faster than the stupid mickey-mouse method!!! I wish there were more samba client command-line interfaces, so I could easily copy a local file in Linux over to a samba share on another computer. smbmnt is nice, but I don't have root permissions on the system of interest.
And what can you do with files with your mouse, anyway? Not much! You can copy/move/link, rename if you're patient enough, or "open" which is some action that's the wrong thing half the time. Okay, drag and drop is good, and still has some untapped potential, but still with the mouse your options are extremely limited compared with the command-line interface of a good Unix shell.
All of this time-ordered stuff just amounts to "ls -ltr", which takes a whole lot less time than clicking on anything with a mouse. And the ls command is far more powerful since you can pick out file types with globs, or more complex filters with egrep, or whatever! Now, admitedly this only works in a particular directory, and there we can do better, but this is still vastly superior to any mouse-driven interface like the ones in the article.
The Unix find command is unfortunately very useful, and the interface is extremely akward. Actually, I feel that VMS's search command is even a little better than find. locate | grep can work well sometimes.
What we really need is some kind of cross-indexing. Perhaps there still needs to be a primary filing system, or directory tree. But this could be augmented by other systems that organize files in different ways, mostly automatically. It's hard to think of all the details, but there should be some kind of small find-file dialog/popup that narrows down possible matches as you continue to add information, like typing in the file name, or looking for a range of dates, or a certain file type or application, or topic. The shrinking list should probably remain time-ordered by default. I can imagine adding this kind of capability to Konqueror for those people who still need visual file representations as a crutch to help them get through their crawl (pre-toddler) stage. But hopefully it could also be added to a command-line interface somehow.
Also, the concept of a working directory is quite powerful, and needs to be taken into consideration. When I work, I typically am using 1-4 directories at any given time, which is easily and logically handled by having multiple terminal windows. I also use the directory stack on occasion, and "cd -" a lot. It's faster than reaching for the mouse and changing windows. If files can be cross-referenced by topic, then perhaps a "working topic" concept could be useful?
Well, that's enough ideas for now.
Why did they have to pick such lousy examples of American pop culture? Stuff like Independence Day and Temptation Island isn't culture, it's cultural abuse for profit! It ashames me that this is the kind of stuff they are now yumming-up in Kabul, since it is the worst example of American culture IMHO.
The price we pay for a free society in an information age is that we gradually build up resistances against media manipulation and other trash like this. For example, those happy-go-lucky commercials of the 60's and 70's seem ludicrous and silly to us these days, just bouncing off our thick armor of skepticism. But 30 years ago those commercials apparently worked!
After some years of isolation, the people freed from Taliban rule may be hungry for all the trashy sensationalism that abounds in our society. But they may be lacking the ability to recognize the more subtle manipulation and propaganda prevalent in US media and pop culture.
Or, maybe not. What do I know, I haven't lived in Afghanistan myself. Maybe these folks know how bad and stupid these movies and shows are, and are just watching them because they embody the those qualities thought "evil" by the Taliban. Even so, I am genuinely embarrased by this.
Hey, I thought slashdot cited a comparison of the (fixed) Rik VM and the AA VM, and came to the conclusion that they performed about the same! They were both MUCH better than the 2.2 (old Rik) VM. What's Alan's evidence that the AA VM is "beating the pants off Rik'v VM?" If they really do perform about the same, I would have to side with Alan's original decision to just patch the old VM.
I think that you have to be careful not to give up too soon when it starts to get tough. It's natural to start feeling restless when you are genuinely being challenged. On the other hand, that's also a natural reaction when you aren't being challenged enough.
Instead of asking yourself how you feel while actually doing the programming, ask how you felt about it once you finished some project. And focus on your favorite CS classes instead of your least favorite ones. In general, if you're searching for what it is that you really enjoy doing, look at your most positive past experiences and compare these with similar experiences in other fields. This is a much more accurate and insightful comparison.
Although it's possible to do well financially after grad school, I'm not sure that it's the norm. I'm not in CS, but now after getting my Ph.D. in physics I am beginning to realize the fantastic opportunity cost of it.
Yes, you can get a stipend and tuition waiver, but no matter where you go you will be living close to the poverty level. This condition will last several years (average in physics is 6-7 I think, and it took me just over 8). During that time you won't be accumulating retirement savings, if you're married it's even tougher, and you won't be paying off your undergrad loans.
Compare that to spending 6-7 years working at some company. At the end of this time, you could be earning well over what a fully-tenured professor makes at the end of their career. You'll have paid off most of that college loan, and probably begun saving a large amount of money. Compared with the grad school track, you're doing very well! The difference may be close to a million bucks!
After grad school, you could probably get a better job than the one you would have started fresh out of college. But since then you would have made your way "up", and you would be earning the same amount as most grads do. So 6-7 years after the undergrad degree you would be earning approximately the same whichever way you go.
I'm not recommending against this. I'm still glad that I did it. But money is a big consideration -- grad school is an enormous sacrifice. You have to really want it, and be passionate about advancing the field. If you can't imagine yourself doing anything else, only then would I recommend grad school.
- Topher
I agree with this completely, except that I read the original post as a question of reliability or accuracy of the commodity hardware.
Calibrating any device is important, and I love the laser printer idea for positional calibration. I think other posters responded to the intensity aspect of this.
One problem is that, for digital cameras, most are automatic and set F-stop, shutter speed, and do color corection and sharpening afterwards. You don't want any of this post-processing, and you need to know the shutter speed and F-stop (or their equivalents). I don't know enough about the market to say where these are available or not. I guess if you can't control this directly, then you'll have to include calibration data with every photo as part of the "scenery", as if each photo were taken with a completely different camera with different properties. I have a great book entitled "CCD Astronomy" which, while it isn't exactly on topic, covers the basics of image processinig and calibration very nicely. I don't have the book with me now, so I can't tell you what the author is. I used this book as an undergrad in physics while working on a CCD camera as a research project. It was very accessable to me.
But the main thing you're after, I think, is the accuracy of the device, after it's been calibrated. I think this is based on two factors, the actual pixel sizes/bit depth, and the accuracy of your calibration factors. Something like pixelsize/sqrt(12), added in quadrature to the calibration errors. Estimating the accuracy of the calibration is an interesting business, and there are a variety of ways you could do it. Taking multiple calibrations and finding the statistical spread (RMS) is an easy way, but only gives you a lower bound because there will be systematic errors in your calibration procedure. I'll leave it at that. Probably any intelligent, hand-waving approach to estimating these systematic errors is enough for a senior project. A really thorough approach could take much more time than you have, generally speaking.
Hope this helps!
"We are going to support the latest versions of Opera and Mozilla so people will be able to get the MSN experience," said Bob Visse, MSN's director of marketing.
But, Visse warned, "the experience may be slightly degraded simply because they don't support the standards we support closely, as far as the HTML standard in those browsers."
...
Visse said earlier Thursday that the message would be shown to people using "browsers that we know don't support (W3C) standards or that we can't insure will get a great experience for the customer." W3C refers to the World Wide Web Consortium, which is developing industry standards for Web technologies.
Wow! They've left the door wide open with that last statement, especially. They can't "insure" (ensure) the performance of any software not directly under their control! Sooo, they are really saying that "we don't recommend using any software but ours." Well, of course!
What really irks me is that internet-savvy folks will realize this FUD tactic for what it is, and hate MS even more for it (which isn't even possible, so no damage done). But 95% of the public will take the message at face value, think that non-MS browsers are flaky, and that people like us who disagree are self-deluded fanatics. So MS "wins."
This is classic FUD!
The main problem here is that Joe Newbie will take it at face value. He won't realize that Mozilla, for instance, is more standards compliant than IE and that MS is breaking their web pages by using MSHTML and blocking the better browsers on purpose. He won't realize that you can change the browser string by just one letter and view the web pages with no problems. He will instead think that these other browsers are inferior -- the opposite of the truth.
You're right, this article claims at first to present a meaningful comparison, but it completely misses any and all meaningful comparitive points. The article is entirely based on three unsupported assumptions. Here's how I read it:
1) Linux is cheaper than Windows and Windows + comercial apps cost roughly 20% of the hardware.
- The first point is fact, but the 20%-ish part is made up. Probably right anyway, but I don't know.
2) *nix is easier to administer by a factor of 8
- I don't believe this. Those sys. admins I know who deal with both like Windows better. However, they do spend more time administering Windows, but that's only because they've put it on everyone's desk. My best guess is that the two OSes are equally time-consuming to administer by a competent person.
3) Windows crashes on a daily basis, while *nix systems never crash.
- This is crazy. In my experience, Windows NT is slightly more prone to crashes than Linux, but running on good hardware it's rare to see a BSOD more than once a year. The stability of these operating systems is a non-problem, compared with stability of application software and even hardware. Netscape/Mozilla in Linux is no more stable than Netscape/Mozilla in Windows. Emacs might be more stable than MS Word, but generally speaking it's the software stability that causes the most problems.
So, where's the evidence to support these statements? There are a lot of hypothetical numbers given, but they are just consequences from the underlying bogus assumptions.
Where's the interesting information? Are cost and reliability really the major concerns? How about usability, popularity, productivity, educational value, etc? For a school, you might want students exposed to a variety of systems in order to better prepare them. Learning MS Word version 200x is not nearly as useful as learning Word, StarOffice, and maybe LaTeX. Variety gives you more basis for abstraction and allows you to learn new software much more quickly. Unless you're a technical college, you should be more focused on building strong learning frameworks than teaching specific skills for now-current technology.
For a business you're more concerned about productivity, so do the applications offered on a particular platform suit your needs? I'm sure that secretaries prefer to use Word than, say, Abiword. So give them Windows. Excel is probably better than gnumeric. But I like Perl+gnuplot better than Excel for most middle-weight data anlsysis tasks.
Okay I'm obviously just rambling here, but to me these are the really interesting issues. Cost is kind of important, both licensing and administration costs. But I don't think it's the biggest issue, really. And certainly stability is not much of a concern except for servers. If you're a major banking institution and you want totally secure, stable servers, then don't use Linux, Solaris, *or* Windows. Try something like VMS!
Anyway, this was a truly vaporous article, not worth posting.
In my experience, Windows NT 4.0 is very stable, almost as stable as Linux can be. I've been using Windows NT 4.0 ~8 hours a day for the past 5 years.
I began to see frequent (about once a month) BSOD's on one computer that was really being pushed to its limits. It was a 200MHz PII w/ 96MB RAM. It was already swapping after I would log in, before running any major apps. Now I'm using a newer computer (well, about 2 years old now), with 128MB RAM. It could definately use more RAM, especially these days with it so cheap, but after 2 years of use I have NEVER seen a BSOD.
So most of this depends on hardware stability, and what software you use. I use Windows very lightly, primarily using exceed and connecting to OSF1, Linux, AIX, IRIX, etc. Even so, I do use several other windows apps frequently such as web browsers (Mozilla these days, Netscape previously), MS Office, Corel Draw, music players, and such.
Netscape and Mozilla crash a lot, and some of the most damaging crashes are when I'm writing mail in Mozilla, have to look something up on the web, and the browser crashes -- bringing down my email composer along with it. I'm getting in the habit now of launching IE just to browse while writing long email messages, so that a browser crash won't kill my unsent message. I also use IE to browse Microsoft's web pages and ibuyer.
Exceed crashes often too, but even when exceed crashes, it's very unlikely for me to loose more than a half-hour of work because everything is either on disk or edited in emacs. I would rather just run Linux on my machine, but that's not my choice to make.
I have to think that those of you who see so many BSOD's running Windows are either pushing old and flaky hardware to its limits, or are running tons of buggy software.
On the other side of the spectrum, the old Mac OS's were horrifically unstable, and seemed to crash once every 2-3 hours no matter what hardware or software you were using. And these days Windows 95 and 98 give me about a crash a week at best, sometimes more.
This is really two topics in one post -- sorry.
;)
1) The point of grammar-based prejudice is a good one! I think online communications (email, message boards, chat rooms, IM, multiplayer games, etc) actually exacerbate the situation. Since text is often the only clue we have about other people, I end up making a lot of assumptions about others by their writing style. Assumptions about age and education, primarily. The fact that my assumptions prove correct more often than not strengthens this instinct. But is this another form of prejudice?
2) While I enjoyed the test, it always aggravates me when people equate salary with success/prestige. I've just finished my Ph.D. in physics, and am looking at jobs now. There appears to be a major fork in the road, where I need to decide to go into industry or acadamia. I could be challenged and happy either way, but it's a difficult decision. My feeling is to stay in academics, because I feel a strong affinity with the whole academic process of teaching, research, and open sharing of knowledge. But jobs in the industry typically pay two to three times more than academic jobs, just starting out. And later on the academic salaries quickly asymptote while salaries in the industry have practically no limit. From a purely financial perspective, the decision is absurdly obvious.
So my future salary is not determined by my grammar, grades, or whatever. It's determined by my priorities. I would say "greed/ethics ratio", but that's too smug. So I won't say that.
I also aggravates me when people talk about intelligence like it is some kind of metric. I personally don't think that intelligence can be measured in any meaningful way. Grammar, intelligence, and salaries are not like inches, centimeters, and cubits. They are related more like sweetness, color, and temperature of food are.
Whew! done ranting. That felt good.
Different radiation patterns will vary with distance in different ways. Uniform radiation falls off as the square of the distance, but beamed radiation does not. All that this guy has shown is that the radiation is beamed. There's no new physics in that.
I briefly touched on this while writing a post earlier, but it's been bugging me more and more so I feel the urge to elaborate. The guy does something involving extremely high currents over short periods of time (read: powerful electromagnetic radiation source), and somehow attributes this to a quantum anti-gravity! It's easy to criticise Podkletnov's experimental technique, but this logical leap is so flawed it's hillarious.
He writes: If the effect is truly gravitational, then the acceleration of any test body on which the impulse acts should be in principle independent on the mass of the body. ... Here, however, we encounter a conceptual difficulty. (The difficulty lies in the author's inability to use reason.) Suppose [we put in the beam] a very massive pendulum. If the effect is gravitational (an unsupported and ludicrous assumption to begin with, but allriiiight) then the acceleration of a test mass should not depend on its mass. However it is clear that in order to give this mass the same oscillation amplitude of the small masses employed in the experiment, a huge energy amount is necessary, which cannot be provided by the device. Therefore the effect would seem to violate the equivalence principle.
There are at least two gaping problems with this logic, which is actually the springboard off which the author launches into 20 pages of pointless theory. First, it's a ridiculous extrapolation. He observes some (inconclusive, I'm certain, though he presents no data) evidence that the impulse given to the test masses is proportional to their mass. This means the energy absorbed by the free objects is proportional to their mass. Then he conjectures that a really large mass must do the same thing (by extrapolation), at which point it absorbs more energy than he has put into the pulse in the first place. I hope this logic sounds as bad to you as it does to me!
Then he cites it as a violation of the equivalence principle. It's really a violation of conservation of energy, which is by all accounts impossible. Even the quantum gravity theory he appeals to requires conservation of energy, as do virtually all possible physical theories. The equivalence principle simply doesn't apply to this situation, and even if it did, it would be satisfied. This principle only applies to the limiting case of a uniform gravitational field. On small scales, the gravity field near the earth is uniform enough. But his claimed effect would be highly non-uniform. Second, the equivalence principle is basically that the gravitational field is equivalent in every respect to an accellerating reference frame -- which explains why gravity fields produce a force on a body proportional to its mass.
Even though this paper uses a lot of big words (often misspelled), it is by no means scientific. The author conveniently ignores all the reasonable explanations for his radiation, presents no data whatsoever to support his claim that it's a gravitational force, and merrily plunges into a thoretical discourse having no bearing on reality.
It's disturbing that the title of the paper mentions a gravitational force, and throughout the author refers to his radiation as a "gravity impulse". This is a premature, biasing assumption, and it makes the entire paper distasteful to read. A gravitational force would be the last thing I would imagine attributing to this effect, which is obviously electromagnetic in origin.
I have no concerns that he somehow set up the experiment "incorrectly". If this is not a hoax, then whatever he did to create the radiation is fine, as long as it's described well enough for others to reproduce. However, his tests of the radiation are biased toward the idea that it's gravitational and not electromagnetic. He does not use antenae and plot the frequency spectrum, for example.
There is no table showing the various materials used, at various distances, and the relative effects of the pulse on them. Because the pulses are not very uniform, many materials should be simultaneously tested. What is the confidence level of the hypothesis that various materials experience the same force, proportional to their mass? He only says that it's true, but doesn't show any data!! This is not even close to science. It's more like wishing real hard. If I were a reviewer of the article, I would ask for much more data to be presented.
Section 4b of the paper is highly flawed. Really, what evidence does he present for the case that this is not garden-variety E-M radiation? He says the force is proportiaonal to mass and mostly independant of material (without showing the data which may be perfectly consistent with other hypotheses). Fine, but the atomic charges are going to be proportional to mass, also, so it could be a high-frequency kind of thing. He should test it on, say, different isotopes of the same element. Or lead vs beryllium, to get a decent range. He says that electromagnetic shielding doesn't attenuate the radiation. Okay, if you say so, but please, what kind of shielding did you try? Did you use a conductor, or mu-metal? How large? How much? To what accuracy did you test this? Magntic fields are extremely penetrating, and a Farraday cage doesn't help. I know, my office is one floor up and one room to the right of an 8 Tesla magnet, and I can't put any computer monitors in the Southern half of my room!
Then in 4b he has some completely lunatic argument that his "new force" is not consistent with GR, because if he extrapolates the effect way beyond the range he has tested, he comes up with a violation of conservation of energy. "My tiny test balls received kinetic energy proportional to their masses, so logically, if I put a wrecking ball in the way it would absorb more energy than I put into the pulse! Ha!" He calls this a violation of the equivalence principle, which is absolutely wrong. It's a violation of conservation of energy, which is technically equivalent to saying that the laws of physics change from day to day (that time is not a valid symmetry).
Then the rest of the paper goes into theories of quantum gravity and stranger stuff, which is most certainly not proven physics (not that I don't believe it, but come on!). I didn't read any of it, because I would rather read good science fiction than bad science fiction.
Assuming this is not a hoax, I would be mildly interested in seeing a proper analysis of this high-energy E-M pulse. But there's enough genuine and important scientific research that is getting its funding slashed in the US (thanks, Bush!), so I hope experiments like this don't get more attention than they deserve.
Topher Cawlfield
I just bought a CD which I had completely downloaded in MP3 format (through gnutella), and was very impressed with. So I would answer to the survey that, yes, I would buy a CD that I downloaded music from. But on the other hand, I probably would have bought a CD at that time anyway, so gnutella downloads simply helped me make that decision. I'm certainly glad I bought the CD since there is so much more to hear that doesn't come through on MP3's 128 kbps quality. I'm not a raving audiophile, but I'm not deaf either. Somewhere inbetween. :-)
But will gnutella/Napster cause me to buy more music than I would ordinarilly? Maybe -- it allows me to sample a larger diversity of music, which might get me to buy CDs I wouldn't buy ordinarilly and thus inspire more of an appetite for music. Or, maybe I'll just find out that the CDs I've been considering really don't sound as good as I hoped. I think the former scenario is more likely, but I honestly don't know the answer, even for myself!
So this should make it obvious that any kind of survey like this one is not going to disclose any truth about whether or not Napster is helping the music industry. Also the major source of bias in a survey like this is: Who's choosing to take this survey? It's obviously people who are familliar with Napster, as the first statistic showed. It's probably also people who think Napster is good, and want to "prove" it. So even if the survey questions were insightful it still wouldn't mean anything.
I also hated the comments about the music industry needing to be more selective, supporting only a couple dozen artists! I agree with the general conclusion that the music industry should be worried about things other than Napster, but I think the music industry is much too limiting rather than permissive, way too comercial and concerned only with the bottom line.
I think the best music is the stuff that would never be released as a single. The bad songs are the ones that you instantly like the first time you hear them, and get tired of quickly. These get airplay because the execs are listening only for that instantly-appealing hook. The good songs are the ones that take some time to grow on you. These are stamped out by the industry as much as possible.
So you need some kind of function like
speed = 9/(10-WarpNumber) c
I don't think that's exactly the right function, but it's something kinda like that. Actually I think the real function is more "decimally inspired" and artificially exponential, but I don't remember just how. In any case, warp 1 is the speed of light, and at warp 10 you "occupy all points in space at the same time."
Another important aspect is that, even if flagships like the Enterprise can exceed warp 9, they can't cruise at that speed. Cruising speed is perhaps more like warp 4--7 for voyager, I'm not sure exactly. It's whatever speed they can sustain for long periods of time.
So if the Milky way is about 100,000 light years across, and Voyager is on the opposide side, and they can't go straight through the center because of various astrophysical hazards, maybe a 75,000 ly journey is about right. So to make that in 75 years, they have to be going 1000 times the speed of light. I don't know what the cruising speed of Voyager is, but 1000 x warp 1 seems "reasonable" (whatever that means in SciFi).
"Dead", for an OS, means that nobody is writing new applications for the OS or supporting new hardware. A dead OS is one that's falling so far behind the forefront of application development that it becomes practically useless.
MSDOS is dead. VMS is probably not dead but may be close in spite of a few yet-unmatched technologies. Mac OS is not, and neither is Linux by a long shot!
What Linux has going for it is easy to underestimate. It's a true community project -- a great development platform because of its freeness. IMHO it has more potential than any other OS because the software and libraries being written today are the building blocks for tomorrow's software, and so on. This cannot happen for proprietary environments like Windows since this level of sharing is not encouraged.
Yeah, I'm one of those many users who has a dual Windows/Linux desktop. My wife and I use Windows for things such as Quicken, Cakewalk, Finale, and games. But I use Linux for everything else - web browsing, ssh, development, analysis, basically everything related to my research work. I don't have a problem with this division! Use the right tool (or OS) for the right job. I use Windows NT with Exceed connecting to Linux+OSF1 at school, but I would much prefer the Linux desktop because it is much more configurable and I feel much more productive. So many of the apps I use are supported naitively in Linux and not Windows. I would say that my own needs are different than the "average user", but there is no such thing really. For myself and a great many others, Linux is not just a viable alternative for a desktop OS, it is the superior one by far! Linux is not dead, but growing and thriving.
I looked into this a little bit for my research group at UIUC. We were wanting to buy some more disk space, somewhere between 400GB and 1TB. There were two options I considered.
In our situation we wanted to be able to process data as fast as possible. We have a growing collection of dual-PIII "compute servers" and divide our data amongst the computers. Typical jobs will run on a dozen of these computers (24 CPUs) and rip through data in either minutes, hours, or even months depending on the job. We are often I/O-bound.
We went with the SCSI disks for a few reasons:
Of course without the infrastructure of our existing RAID box, the economy would slant much more toward the IDE RAID solution. And for a home environment I think smaller-scale things like the ABIT KT7A-RAID card might also become very handy. Last I heard, the RAID controller it used wasn't fully supported in Linux, but that information is probably out of date by now.
We are currently using OSF1 for our server instead of Linux primarily because of the advanced filesystem: a 64-bit filesystem, ACLs, partitions that span multiple disks, and so on. It's good to hear that most of these advantages are now available to Linux, and XFS looks extremely promising. Keep up the good work, everyone!
I like to think of math as a language. For one, it's a way of communicating ideas both abstract and concrete. Also like other languages, it provides us a conceptual framework which allows us to understand things better. And finally it's a powerful tool when you learn how to manipulate it.
Much of our math education is just the manipulation part of math, which is useful but never by itself (except on tests, as you said). Learning to describe and understand things mathematically is at least as important. With these three aspects mastered, mathematics becomes indispensable to whatever you do. Well, except for sex -- but other than that, it's pretty useful.
First, I actually hear a new song on the radio and think it's not too bad. Yes, this does actually happen once every month or two. If the artist is good, then it's always the worst songs on an album that get any airplay, so I would probably want the album for the other songs. Or if the artist is bad, the other songs will be a similar tripe and I won't be interested.
Next, I can download parts or all of the album from napster or gnutella. I'll soon find out whether or not I like it. If I really like it, I'll buy the CD because I can play it in my car or home stereo which are both much better than my cheap computer speakers.
I also think the idea of buying a CD just for one song that you've already heard is crazy. The really good songs are the ones that take time to appreciate, and you never hear those unless you get the whole CD. But if you're a "professional student" like me, you won't be able to afford buying CDs very often, so you have to be choosy. Napster and gnutella help me do this. In fact I'm surprised by how much more music I like because of this.
This may be a foreshadow of industrial trends to come with the present economic recession because, for the past 8 years or so, particle physics has been in a major recession of its own. After suffering 20% cutbacks in Department of Energy funding over the last few years, we got a 5% cut last year, and rumors of a 15% cut this year are very threatening.
Other reasons for basic research programs to switch to Linux include security of having the source code, and the way that the free software movement is consistent with the philosophy of our research. Scientists can get very fearful of any software that's not under their control, so having the source code gives a kind of reassurance that their computing platforms won't break in some way that can't be fixed. And also the basic goal is to increase public knowledge, not to create intellectual property. (I sure am glad I don't need to pay royalties to Einstein's great grandsons every time I boost particle trajectories from one reference frame to another, or compute invariant particle masses.) So it makes sense to use, and develop as the need arises, free software whenever it's feasable.
Okay, I'm getting further off topic, so I'll stop.
The "seats in the classroom" you refer to are particular values for the momenta of the particles (electrons in the case of white dwarfs) in some volume. So as you try to compress the material, in you're adding more particles to any given volume of the stuff. These particles must pick discrete values of momenta that aren't already "taken", so they must be fast. All of the lower momentum seats are already taken, if you consider a white dwarf to be "cold". Even though a white dwarf is very hot in ordinary terms, it's "stone cold" for these purposes because the pressure due to temperature is much less than what's needed to compete with gravity.
So the more dense the white dwarf becomes, the higher the average momentum of the electrons must be. This average momentum translates into pressure. So even though the white dwarf is not hot enough to support itself against gravity by ordinary classical gas pressure, there is a minimum pressure of the gas that comes, basically, from the Pauli exclusion principle.
As you increase the pressure more and more (we're considering more and more massive stellar cores), the electrons you're forcing into a given volume will need to adopt larger and larger values of momentum. Eventually the momentum of the electrons will become larger than the rest mass of the electrons, and they become "relativistic" (moving very close to the speed of light). In this case, as you add more electrons and increase the average momentum, you aren't actually increasing the speed of the electrons by much -- they're already going (very nearly) the speed of light. At this point, the pressure doesn't build up as quickly with density, and "gravity wins".
So if the core of the star is massive enough, the force of gravity will overcome this electron degeneracy pressure, and you could be left with a neutron star or a black hole. In the case of the neutron star, the protons and neutrons (also spin 1/2) will get close together and create their own degeneracy pressure. If the density is so great that the protons and neutrons become relativistic, it will collapse into a black hole (well, that's the best theory anyway). The protons and neutrons need a much higher momentum to move near the speed of light, because their mass is about 2000 times greater than the electrons.
For even more complicated reasons, many of the protons and electrons in a newly-forming neutron star will interact to form neutrons and neutrinos. The neutrinos leave, cooling the core and helping out with the supernova. The neutrons stay behind of course, forming a large percentage (70%?? I forget) of the composition of the neutron star, hence the name.
I hope this helps! I guess the short answer is that special relativity spells doom for massive would-be white dwarfs (or would-be neutron stars).