Yes, refraction is due to a change in group speed between media: if in one medium, the constituents interact a lot more with the light than the constituents of the other medium, the group speed in the highly interacting medium tends to be slower than in the other. Because of the requirement that various boundary conditions at the mediums' interface must be matched, the wavefronts tend to bend at the interface, and one has refraction.
You're right, in that absorption of all colors but, say, blue by some object will make that object look blue. BUT one may also separate colors into different portions of an object -- the light of different colors has simply ended up in different spots, but hasn't been permanently absorbed or attenuated (as in interference colors in bubbles, or oil slicks, etc.). One way to obtain this is to simply reflect light multiple times off of two parallel (or nearly parallel) surfaces, as in a bubble or a pane of glass. Very little of the light is really absorbed, just shuttled from place to place.
I think that we're probably just thinking of different "complementary" pictures of light -- you're focusing (agh!) on the photon, discrete picture, and I'm focusing on the continuum, wavelike picture. I'm essentially trying to scale down what I know about wave mechanics to spatial regimes where those wave mechanics get pretty strange (due to the wavelength vs. molecular size discrepancy). I think you're applying some scattering theory (or at least some good intuition) to the problem. Of course, if we're both careful, we should end up with exactly the same answer.
So isn't this subject to the same inherent photon-manipulating characteristics as other carbon atoms?
Oh, absolutely. However, one must recognize that things can scatter light in very strange ways depending on their spatial relationships to each other. Carbon atoms in graphite and diamond are identical, but their locations relative to each other make all the difference between opaque grey, and transparent brilliance. Same with water vapor in the air (humidity in the air doesn't scatter light by itself, but get those water molecules clustered together in big enough drops -- say, in a cloud -- and they scatter light quite effectively).
Basically, what I'm getting at is that you have to have some semblance of order on a scale comparable to the wavelength of light you want to interact with, to ever scatter that light. Because this "cloth" is so thin, I doubt it'll interact with the light much at all, unless you have wavefronts incident on it at grazing angles -- then you have the chance of the light interacting with it over larger spatial domains, and getting some scattering.
I dunno. Time to look at boobies. They scatter quite well. Especially when they hear geek-talk.
Except glass (usually) has a constant index of refraction (as does bubble film, which you're apparently thinking of). It's the fact that there is chromatic dispersion (simply: different frequencies of light--the colors--travel at different speeds in the medium (giving different refraction angles, and, therefore, different paths and pathlengths). So even though the index of refracton is constant for a _given_frequency_, the fact that the index changes for different frequencies gives the colors (along with multiple reflections from front and back surfaces).
The fact that this stuff is only one molecule thick is much more persuasive. In fact, very thin bubbles are completely transparent to light, because the light cannot refract if the film is less than about a wavelength thick. Since molecules (chains and polymers get a little tricky, of course) are generally much, much smaller than a visible wavelength, this stuff will probably be virtually invisible, unless, as another poster pointed out, it's extremely highly conductive (which would cause a skin-depth effect and probably do more complicated things to light).
Yes, it is nice, but it would be nice to get some feedback once one has ordered the things. I have never been contacted at all, with any sort of messages to the effect of "We see you've ordered some of our CDs -- they might ship sometime next month," or "We're having printing/production delays, please be patient," or even "Thanks for your interest." I've gotten nothing for feedback. Maybe I should actually look at their site and see what's up!
Don't know why you've not heard of it. It's been well known for a long time. An example of the sort of data (and its analysis) that one might play with can be found at:
I am. It takes no electrical power; runs manually. But the pixel sizes are inconsistent and probably too large for good quality work (unless tantric). You also don't get any color except white. Also, it generally needs a good snapshot of Natalie Portman in hot grits to prime the pump.
It's probably best to not to take family portraits and act as a Polaroid instamatic. That's just wrong.
Oops! You're totally right. I did NOT read the original parent post (the actual UW release), because, at the time, it wasn't being served. So I ASSUMED that the report was about the talk I saw (maybe a couple of months ago). I didn't realize that this new method requires the earth-orbit based plasma source. The talk he gave to us primarily was concerned with the plasma-induction coil being propelled by the solar wind.
The Question 2 you raise is a good one. Presumably, since it's in earth orbit, we could keep shuttling fuel of some sort to it w/out too much effort (hah!). I dunno. I'll be sure to hammer him on that if he ever shows up here again:)
I saw a talk, by this group, when they ventured across the state to my University. Despite the fact that all researchers are convinced that their new way of doing something is so much better than the other ways, this group really seems pragmatic about the whole thing.
They admit that the difficulties in getting this to work are tremendous. But from a cost standpoint (as opposed to nuclear methods, the only other energy source we can work with right now that provides enough energy density -- antimatter has a much higher energy density, of course, but we haven't any way of carrying it with us!), the UW method is the best I've seen so far, and it doesn't really screw around with the tricky issues of getting a nuclear source up in the atmosphere, where a problem can cause BIG problems for those of us on the ground. His charts showed that among all the methods out there (including some -- I don't remember seeing some of the parent poster's suggestions -- of Orion, Nuclear Salt Water, etc.), this dealie from his group sort of lies on a critical line between expense, availability, and ability to develop it to a useful stage.
Technical, very tricky engineering is required to get their "induction coil" out there, and have it be strong enough, but once it's deployed, the basic physics behind the thing is really pretty foolproof (as far as I can see).
I *did* ask him during the colloquium whether the accelerations provided would be enough for a long manned spaceflight -- they're SO much less than 1g. He said that for (far-in-the-) future flights, they have found a way to couple the fields' angular momentum to the "sail", thus spinning the spacecraft about the axis of translation, so that you could essentially have a spinning ring of which sci-fi writers are so fond. However, the efficiency of this is pretty low, so to spin the thing up, you might want to use chemical rockets, and let the plasma thingy do its job in the other direction.
[...] Needless to say, that we are totally dismayed with Dr. William's unprofessional attitude and her unscientific and mendacious press release.
This simply can not be the basis for future cooperation and we shall inform the local, regional and central authority by copy of this letter that from now on Dr. Williams is no longer welcome in the project area, as per the terms and conditions of our existing research and conservation agreement with the authorities.
Consequently, any further interference by Dr. William's may adversely affect the project and the people of Bili.
Yours sincerely, Karl Ammann, Hans A. Wasmoeth
From the aforementioned website. Looks like we might be dealing with some vapor-meatware here.
Yes, I'm very well aware of the history, DoD, ARPAnet, all that. My question was more of the evolution of data pathways since then, how a disaster in one area can/can not be gotten around today, and so forth. You touched upon a lot of that in your decentralization argument.
Seriously, how much was the "Internet" used in '89? One could argue that San Francisco probably was one of the most important nodes in the 'net back then, and so disruptions there should have had a huge impact, as opposed to today, when things are more distributed. On the other hand, the whole network is so complex that a major disruption there today may well bring a lot of traffic to a standstill.
Well, I've yet to see a book or professor who says anything remotely like "a=f/m, now go plug in some numbers." (Although, to be fair, probably a lot of students might see it that way.) My own take is that this sort of thing should be taught in a somewhat historical way, but with more emphasis on the history. For example, the fact that "an object in motion tends to stay in motion, unless acted upon, etc." is intuitive to me, but maybe that's because I've been thinking about this stuff for a large part of my so-called life. Historically, people just thought that things "naturally" wanted to stop (almost the same "naturally" that we have to invoke when saying that things "naturally want to keep going). Only later was the influence of friction and so forth really recognized. Students coming into physics classes tend to think the same way, and gently coaxing them out of that way, and toward how physicists think should be, well, *convincing*, and perhaps the best way to do that is to show some natural progressions, especially focusing (on this case, at least) on Galileo's early experiments, and so forth.
Minimizing energy is a concept which is just as vague to students as force is. Hey, at least they can *feel" forces, and imagine themselves pushing on an object. Energy is pretty tricky, because although kinetic energy is visualizable (at least in some sense -- but why is that velocity squared? and what if something is moving along with the object -- then it has no relative velocity, and so it has no kinetic energy?), potential energy is really, really difficult to wrap one's mind around, because it's not visualizable, and it's turned into kinetic energy through the action of *forces*. Ick. You also have the problem where you have to carefully define what your system is, so that energy is conserved in the whole system, and in various subsystems, as in those thermodynamics problems we all hate to love. To an undergraduate sitting there, that might seem hideously complicated. Cheers if you can get it to work, though!
I totally agree with you that how physicists think is a Good Thing, mainly because it seems to provide facility with mathematics, and because it's so applicable to other fields, and gives a lot of flexibility when encountered with unknown problems. It may be very, very cheap of me to say this, because throwing more time at things often doesn't work, but (introductory) physics classes in universities are too short, and too rushed. There's just too much interesting stuff that physics can explain, and too little time to cram all that in to a year, let alone a semester. Students in any of the sciences should see physics as less of a "oh, crap, you're taking THAT class? Do you HAVE to?!?" thing, and more of a fact of life, for maybe two years. I haven't any idea of how to implement that, and, of course, it's been a perennial problem for a long time (see the Physics Today of, well, several years ago, which has a picture of a bunch of textbooks stacked on the cover, and which documents many of exactly the same complaints in universities 100 years ago).
Best of luck with finding better ways to teach this stuff! We all can benefit from people thinking honestly about that question, really.
Actually, to be pedantic (but, again, this is getting at a question to which physicists do NOT know the answer, and so it's very interesting at many levels), GRAVITATIONAL mass http://en.wikipedia.org/wiki/Gravitational_mass#Gr avitational_Mass is defined (roughly) as the number you get when you weigh something. INERTIAL mass http://en.wikipedia.org/wiki/Gravitational_mass#In ertial_Mass is a lot different (at least in everyday life) because you can talk about it--even in an "intuitive" way--without ever referring to a scale or weighing the thing. The heart of General Relativity pretty much insists that these two masses are EXACTLY the same, and they seem to be, experimentally, but it's not very convincing that they HAVE to be. My understanding of their equivalence -- which is spotty at best -- is that inertial mass is evinced in a sort of "radiation reaction" effect, similar to the reaction force that one gets when one tries to accelerate, say, an electron. Feynman and Wheeler tried to explain this reaction by invoking half-advanced and half-retarded waves, where the advanced waves arrive at the object just as you try to accelerate the thing, having been emitted from possible absorbers just in time to arrive... If gravitational waves exist, they might be just the half-retarded waves in this situation, and the half-advanced ones would account for the inertial mass of any object.
Most fascinating to me is this: Relativity says that fields containing energy (e.g., gravitational fields) act as though they have mass (E=mc^2, after all). This mass must provide some gravitational force. Thus, gravitational fields may create "their OWN" gravitational fields, etc. In fact, this self-feeding would account for the infinite gravity (beyond the event horizon) of a black hole.
Oh? And how do you expect an undergraduate biology major to understand (say) a particle's motion? Personally, saying that we should NOT teach a=F/m (which makes sense in real life, as long as you can get around the tricky 'what IS mass, really?' issue) in favor of defining a trajectory as the path over which the action of a particle's motion is extremized is crap.
Maybe you're saying that mathematics classes need to teach integral calculus a lot earlier, so that people can do path integrals, instead of algebra-based physics? I dare you to teach Lagrangians and Hamiltonians to scores of undergraduates, whether they're engineers or art majors, and have them make as much "sense" as Newton's second and third Laws.
One of my gripes (hey, I'm a graduate student in physics, too!) is that books meant for other majors SO misrepresent what physics IS, and even some very basic concepts. Recently, reading my girlfriend's microbiology book (which starts out explaining atomic structure and so for -- very well, actually), I came across the phrase "Carbon has such-and-such properties because of its location in the periodic table." Now, I can understand that if this were said in context of "Hey, notice THIS pattern, and THAT pattern," it might make sense. But this statement was the beginning of a MAJOR section! Carbon doesn't have those properties because of its location in the table! It was PUT in the table where it is BECAUSE of those properties.
Yes, this is quibbling. But a lot of people believe the author's exact words, and they're words which don't even make sense if you understand the simple fact that the periodic table, neat as it is, is contrived by man to explain nature, not the other way around.
In short, we insist on complicated terminology because to speak about things using lax terminology is NOT THE TRUTH. If you're talking about a certain thing, you want to make damned sure that other people know exactly what you're talking about. It's kind of like complaining that we shouldn't have to learn all of those names of those hue things -- they're all just colors, right?
Books can be poor; professors can be dry and vapid. But the subject matter isn't, really, and some professors really make a good (and successful!) effort to get students involved, interested, and really learn stuff.
Kudos to anyone who can find a better way to teach introductory physics classes. But I have a feeling that the basic paradigms serve as well now as they did 100 years ago, and will serve as well millennia into the future.
Oh, good. Apple Computer has nothing to worry about. Despite the vagaries of language, there's no way a court will uphold "principle content" over "principal content".
What people have to remember is this:
Denver, CO is set up to be the next Washington, D.C., in case the latter ever gets wiped out. Norad is based in Colorado Springs. Both of these potential targets are quite far to the northeast of Durango. The closest strategic targets I can think of are really Denver, Colorado Springs, Kirkland AFB in Albuquerque, and Los Alamos, White Sands, etc. in NM, and maybe some proving grounds and bases in Utah and Nevada. Durango is NOT a target, but it's kind of in the middle of these other, good targets. You'd expect to get a bit of fallout there from a large-scale attack. Having a fallout shelter is GOOD, I suppose, if you're worried about that.
In addition, Durango is one of these "new Aspens", where college students hang out, there are a lot of older locals (ranchers, Navajo, people who showed up before the '70's, mainly), and so forth, but there are a LOT of VERY rich people around (WalMart heir rich; 4th richest in the US rich), who can afford these kind of eccentric houses (and seem to get off on living in this gorgeous place, and ruin the whole atmosphere at the same time because then no one else can afford to live there ).
Finally, a lot of people hunt in Durango (and all over the mountain West). It's the kind of thing where you get a few days off in the fall to bag an elk or bear. So the guy's comment about elk hindquarters, although strange to a lot of people, are very common to people from the Rockies.
Yes, but there are advantages:
1) You don't ever do a FP!;
2) You REALLY proofread that sucker;
3) !wastedwords;
4) The editing is spectacular -- way above the usual standards around here:)
Slashdot Mirror
all gamblers think that they are "better than average," and are "winning players."
Er... yeah. Or they think they may train to get better. Otherwise, they wouldn't play. No one wants to lose consistently.
Yes, refraction is due to a change in group speed between media: if in one medium, the constituents interact a lot more with the light than the constituents of the other medium, the group speed in the highly interacting medium tends to be slower than in the other. Because of the requirement that various boundary conditions at the mediums' interface must be matched, the wavefronts tend to bend at the interface, and one has refraction.
You're right, in that absorption of all colors but, say, blue by some object will make that object look blue. BUT one may also separate colors into different portions of an object -- the light of different colors has simply ended up in different spots, but hasn't been permanently absorbed or attenuated (as in interference colors in bubbles, or oil slicks, etc.). One way to obtain this is to simply reflect light multiple times off of two parallel (or nearly parallel) surfaces, as in a bubble or a pane of glass. Very little of the light is really absorbed, just shuttled from place to place.
I think that we're probably just thinking of different "complementary" pictures of light -- you're focusing (agh!) on the photon, discrete picture, and I'm focusing on the continuum, wavelike picture. I'm essentially trying to scale down what I know about wave mechanics to spatial regimes where those wave mechanics get pretty strange (due to the wavelength vs. molecular size discrepancy). I think you're applying some scattering theory (or at least some good intuition) to the problem. Of course, if we're both careful, we should end up with exactly the same answer.
So isn't this subject to the same inherent photon-manipulating characteristics as other carbon atoms?
Oh, absolutely. However, one must recognize that things can scatter light in very strange ways depending on their spatial relationships to each other. Carbon atoms in graphite and diamond are identical, but their locations relative to each other make all the difference between opaque grey, and transparent brilliance. Same with water vapor in the air (humidity in the air doesn't scatter light by itself, but get those water molecules clustered together in big enough drops -- say, in a cloud -- and they scatter light quite effectively).
Basically, what I'm getting at is that you have to have some semblance of order on a scale comparable to the wavelength of light you want to interact with, to ever scatter that light. Because this "cloth" is so thin, I doubt it'll interact with the light much at all, unless you have wavefronts incident on it at grazing angles -- then you have the chance of the light interacting with it over larger spatial domains, and getting some scattering.
I dunno. Time to look at boobies. They scatter quite well. Especially when they hear geek-talk.
Except glass (usually) has a constant index of refraction (as does bubble film, which you're apparently thinking of). It's the fact that there is chromatic dispersion (simply: different frequencies of light--the colors--travel at different speeds in the medium (giving different refraction angles, and, therefore, different paths and pathlengths). So even though the index of refracton is constant for a _given_frequency_, the fact that the index changes for different frequencies gives the colors (along with multiple reflections from front and back surfaces).
The fact that this stuff is only one molecule thick is much more persuasive. In fact, very thin bubbles are completely transparent to light, because the light cannot refract if the film is less than about a wavelength thick. Since molecules (chains and polymers get a little tricky, of course) are generally much, much smaller than a visible wavelength, this stuff will probably be virtually invisible, unless, as another poster pointed out, it's extremely highly conductive (which would cause a skin-depth effect and probably do more complicated things to light).
Yes, it is nice, but it would be nice to get some feedback once one has ordered the things. I have never been contacted at all, with any sort of messages to the effect of "We see you've ordered some of our CDs -- they might ship sometime next month," or "We're having printing/production delays, please be patient," or even "Thanks for your interest." I've gotten nothing for feedback. Maybe I should actually look at their site and see what's up!
Get out, go hiking, meet people of the appropriate sex, see concerts, learn to cook.
Huh. There's more than one?
Don't know why you've not heard of it. It's been well known for a long time. An example of the sort of data (and its analysis) that one might play with can be found at:
s potanalysis.html
http://www.scientificarts.com/sunspotanalysis/sun
... it's about time to go home. Wait -- every 11 YEARS?!? It seems to get dark about every 24 hours around here, give or take a few.
I'm not aware of any printer that prints white.
I am. It takes no electrical power; runs manually. But the pixel sizes are inconsistent and probably too large for good quality work (unless tantric). You also don't get any color except white. Also, it generally needs a good snapshot of Natalie Portman in hot grits to prime the pump.
It's probably best to not to take family portraits and act as a Polaroid instamatic. That's just wrong.
Thank you! From one coming from behind a University firewall, where .torrent usually doesn't reach, I am in your debt.
Oops! You're totally right. I did NOT read the original parent post (the actual UW release), because, at the time, it wasn't being served. So I ASSUMED that the report was about the talk I saw (maybe a couple of months ago). I didn't realize that this new method requires the earth-orbit based plasma source. The talk he gave to us primarily was concerned with the plasma-induction coil being propelled by the solar wind. :)
The Question 2 you raise is a good one. Presumably, since it's in earth orbit, we could keep shuttling fuel of some sort to it w/out too much effort (hah!). I dunno. I'll be sure to hammer him on that if he ever shows up here again
I saw a talk, by this group, when they ventured across the state to my University. Despite the fact that all researchers are convinced that their new way of doing something is so much better than the other ways, this group really seems pragmatic about the whole thing.
They admit that the difficulties in getting this to work are tremendous. But from a cost standpoint (as opposed to nuclear methods, the only other energy source we can work with right now that provides enough energy density -- antimatter has a much higher energy density, of course, but we haven't any way of carrying it with us!), the UW method is the best I've seen so far, and it doesn't really screw around with the tricky issues of getting a nuclear source up in the atmosphere, where a problem can cause BIG problems for those of us on the ground. His charts showed that among all the methods out there (including some -- I don't remember seeing some of the parent poster's suggestions -- of Orion, Nuclear Salt Water, etc.), this dealie from his group sort of lies on a critical line between expense, availability, and ability to develop it to a useful stage.
Technical, very tricky engineering is required to get their "induction coil" out there, and have it be strong enough, but once it's deployed, the basic physics behind the thing is really pretty foolproof (as far as I can see).
I *did* ask him during the colloquium whether the accelerations provided would be enough for a long manned spaceflight -- they're SO much less than 1g. He said that for (far-in-the-) future flights, they have found a way to couple the fields' angular momentum to the "sail", thus spinning the spacecraft about the axis of translation, so that you could essentially have a spinning ring of which sci-fi writers are so fond. However, the efficiency of this is pretty low, so to spin the thing up, you might want to use chemical rockets, and let the plasma thingy do its job in the other direction.
[...] Needless to say, that we are totally dismayed with Dr. William's unprofessional attitude and her unscientific and mendacious press release.
This simply can not be the basis for future cooperation and we shall inform the local, regional and central authority by copy of this letter that from now on Dr. Williams is no longer welcome in the project area, as per the terms and conditions of our existing research and conservation agreement with the authorities.
Consequently, any further interference by Dr. William's may adversely affect the project and the people of Bili.
Yours sincerely,
Karl Ammann, Hans A. Wasmoeth
From the aforementioned website. Looks like we might be dealing with some vapor-meatware here.
The mechanics of Natalie Portman locomotion in thermally elevated, coarsely-ground, boiled maize.
It was certainly distinguishing itself in my logs...
Must... refrain... from making... corn... joke... Aughhh!
Yes, I'm very well aware of the history, DoD, ARPAnet, all that. My question was more of the evolution of data pathways since then, how a disaster in one area can/can not be gotten around today, and so forth. You touched upon a lot of that in your decentralization argument.
The DARPA Grand Challenge.
Didja notice in the "slowmo_great_bound_small.avi" movie how Rhex was running away from that dude? It's 'cause it just kicked him in the nads. Hard.
Seriously, how much was the "Internet" used in '89? One could argue that San Francisco probably was one of the most important nodes in the 'net back then, and so disruptions there should have had a huge impact, as opposed to today, when things are more distributed. On the other hand, the whole network is so complex that a major disruption there today may well bring a lot of traffic to a standstill.
Sorry, guys. The original poster is actually upset that it's not spelled "evar".
Well, I've yet to see a book or professor who says anything remotely like "a=f/m, now go plug in some numbers." (Although, to be fair, probably a lot of students might see it that way.) My own take is that this sort of thing should be taught in a somewhat historical way, but with more emphasis on the history. For example, the fact that "an object in motion tends to stay in motion, unless acted upon, etc." is intuitive to me, but maybe that's because I've been thinking about this stuff for a large part of my so-called life. Historically, people just thought that things "naturally" wanted to stop (almost the same "naturally" that we have to invoke when saying that things "naturally want to keep going). Only later was the influence of friction and so forth really recognized. Students coming into physics classes tend to think the same way, and gently coaxing them out of that way, and toward how physicists think should be, well, *convincing*, and perhaps the best way to do that is to show some natural progressions, especially focusing (on this case, at least) on Galileo's early experiments, and so forth.
Minimizing energy is a concept which is just as vague to students as force is. Hey, at least they can *feel" forces, and imagine themselves pushing on an object. Energy is pretty tricky, because although kinetic energy is visualizable (at least in some sense -- but why is that velocity squared? and what if something is moving along with the object -- then it has no relative velocity, and so it has no kinetic energy?), potential energy is really, really difficult to wrap one's mind around, because it's not visualizable, and it's turned into kinetic energy through the action of *forces*. Ick. You also have the problem where you have to carefully define what your system is, so that energy is conserved in the whole system, and in various subsystems, as in those thermodynamics problems we all hate to love. To an undergraduate sitting there, that might seem hideously complicated. Cheers if you can get it to work, though!
I totally agree with you that how physicists think is a Good Thing, mainly because it seems to provide facility with mathematics, and because it's so applicable to other fields, and gives a lot of flexibility when encountered with unknown problems. It may be very, very cheap of me to say this, because throwing more time at things often doesn't work, but (introductory) physics classes in universities are too short, and too rushed. There's just too much interesting stuff that physics can explain, and too little time to cram all that in to a year, let alone a semester. Students in any of the sciences should see physics as less of a "oh, crap, you're taking THAT class? Do you HAVE to?!?" thing, and more of a fact of life, for maybe two years. I haven't any idea of how to implement that, and, of course, it's been a perennial problem for a long time (see the Physics Today of, well, several years ago, which has a picture of a bunch of textbooks stacked on the cover, and which documents many of exactly the same complaints in universities 100 years ago).
Best of luck with finding better ways to teach this stuff! We all can benefit from people thinking honestly about that question, really.
Actually, to be pedantic (but, again, this is getting at a question to which physicists do NOT know the answer, and so it's very interesting at many levels), GRAVITATIONAL mass http://en.wikipedia.org/wiki/Gravitational_mass#Gr avitational_Mass is defined (roughly) as the number you get when you weigh something. INERTIAL mass http://en.wikipedia.org/wiki/Gravitational_mass#In ertial_Mass is a lot different (at least in everyday life) because you can talk about it--even in an "intuitive" way--without ever referring to a scale or weighing the thing. The heart of General Relativity pretty much insists that these two masses are EXACTLY the same, and they seem to be, experimentally, but it's not very convincing that they HAVE to be. My understanding of their equivalence -- which is spotty at best -- is that inertial mass is evinced in a sort of "radiation reaction" effect, similar to the reaction force that one gets when one tries to accelerate, say, an electron. Feynman and Wheeler tried to explain this reaction by invoking half-advanced and half-retarded waves, where the advanced waves arrive at the object just as you try to accelerate the thing, having been emitted from possible absorbers just in time to arrive... If gravitational waves exist, they might be just the half-retarded waves in this situation, and the half-advanced ones would account for the inertial mass of any object.
Most fascinating to me is this: Relativity says that fields containing energy (e.g., gravitational fields) act as though they have mass (E=mc^2, after all). This mass must provide some gravitational force. Thus, gravitational fields may create "their OWN" gravitational fields, etc. In fact, this self-feeding would account for the infinite gravity (beyond the event horizon) of a black hole.
It's now time to find boobies on the 'net.
Oh? And how do you expect an undergraduate biology major to understand (say) a particle's motion? Personally, saying that we should NOT teach a=F/m (which makes sense in real life, as long as you can get around the tricky 'what IS mass, really?' issue) in favor of defining a trajectory as the path over which the action of a particle's motion is extremized is crap.
Maybe you're saying that mathematics classes need to teach integral calculus a lot earlier, so that people can do path integrals, instead of algebra-based physics? I dare you to teach Lagrangians and Hamiltonians to scores of undergraduates, whether they're engineers or art majors, and have them make as much "sense" as Newton's second and third Laws.
One of my gripes (hey, I'm a graduate student in physics, too!) is that books meant for other majors SO misrepresent what physics IS, and even some very basic concepts. Recently, reading my girlfriend's microbiology book (which starts out explaining atomic structure and so for -- very well, actually), I came across the phrase "Carbon has such-and-such properties because of its location in the periodic table." Now, I can understand that if this were said in context of "Hey, notice THIS pattern, and THAT pattern," it might make sense. But this statement was the beginning of a MAJOR section! Carbon doesn't have those properties because of its location in the table! It was PUT in the table where it is BECAUSE of those properties.
Yes, this is quibbling. But a lot of people believe the author's exact words, and they're words which don't even make sense if you understand the simple fact that the periodic table, neat as it is, is contrived by man to explain nature, not the other way around.
In short, we insist on complicated terminology because to speak about things using lax terminology is NOT THE TRUTH. If you're talking about a certain thing, you want to make damned sure that other people know exactly what you're talking about. It's kind of like complaining that we shouldn't have to learn all of those names of those hue things -- they're all just colors, right?
Books can be poor; professors can be dry and vapid. But the subject matter isn't, really, and some professors really make a good (and successful!) effort to get students involved, interested, and really learn stuff.
Kudos to anyone who can find a better way to teach introductory physics classes. But I have a feeling that the basic paradigms serve as well now as they did 100 years ago, and will serve as well millennia into the future.
Oh, good. Apple Computer has nothing to worry about. Despite the vagaries of language, there's no way a court will uphold "principle content" over "principal content".
Next?
Which (to me) begs the question: where do the OTHERS fall? Which is worse than XP?
What people have to remember is this:
Denver, CO is set up to be the next Washington, D.C., in case the latter ever gets wiped out. Norad is based in Colorado Springs. Both of these potential targets are quite far to the northeast of Durango. The closest strategic targets I can think of are really Denver, Colorado Springs, Kirkland AFB in Albuquerque, and Los Alamos, White Sands, etc. in NM, and maybe some proving grounds and bases in Utah and Nevada. Durango is NOT a target, but it's kind of in the middle of these other, good targets. You'd expect to get a bit of fallout there from a large-scale attack. Having a fallout shelter is GOOD, I suppose, if you're worried about that.
In addition, Durango is one of these "new Aspens", where college students hang out, there are a lot of older locals (ranchers, Navajo, people who showed up before the '70's, mainly), and so forth, but there are a LOT of VERY rich people around (WalMart heir rich; 4th richest in the US rich), who can afford these kind of eccentric houses (and seem to get off on living in this gorgeous place, and ruin the whole atmosphere at the same time because then no one else can afford to live there ).
Finally, a lot of people hunt in Durango (and all over the mountain West). It's the kind of thing where you get a few days off in the fall to bag an elk or bear. So the guy's comment about elk hindquarters, although strange to a lot of people, are very common to people from the Rockies.
Yes, but there are advantages: :)
1) You don't ever do a FP!;
2) You REALLY proofread that sucker;
3) !wastedwords;
4) The editing is spectacular -- way above the usual standards around here