While we have to be very cautious with regards to our environment and consumption, I do believe there is a tendency for reports from environmental agencies to be overblown. (And this is coming from a long-standing member of both the Sierra Club and CALPRIG.)
I am skeptical with regards to this recent report, because of two facts.
1) The highest per-capita consumption occurs in the first world. (see below)
2) The population of the first world is rapidly shrinking, and will amount to a small fraction of the total world population by 2050. (According to the UN. See this link for details.)
3) By 2050, even the 3rd world population is expected to reach equilibrium, so that the entire world population will actually begin to decline.
Taken together, it seems unlikely to me that the conditions stated by the WWF may actually come about, unless the 3rd world population increases its consumption dramatically, or the UN study is substantially incorrect. This is because, even though the world population is expected to increase from 6 billion to 9 billion by 2050, that additional growth will occur almost exclusively outside of Western nations. Significantly, the population of the first world will actually diminish. Now, the report itself states
"America's consumption 'footprint' is 12.2 hectares per head of population compared to the UK's 6.29ha while Western Europe as a whole stands at 6.28ha. In Ethiopia the figure is 2ha, falling to just half a hectare for Burundi, the country that consumes least resources."
So if indeed the third world consumes a large factor (an order of magnitude!) less "footprint" than the Western nations, it would seem to me that the world might actually be better off by 2050 : they are, quite simply, more efficient at using existing resources.
The question you should be asking, whenever you are evaluating a scientific idea is :
Is/are X consistent with our experimental knowledge of nature?
Where "X" is any hypothesis you wish to check. It can be the "hydrino hypothesis", or it can be the Schrodinger equation.
Now, it is a very simple and straightforwards matter to set up an experimental apparatus to observe the emission lines from hydrogen. Many of us have done it in college or even high schools labs. Each transition is seen in the spectrum.
The result? Completely consistent with the Schrodinger equation (or even the previous simpler Bohr model). If there were an energy state lower than the n = 1 quantum state, it would produce a very visible emission line, which is not seen. This is a very glaring inconstency which is not apparently addressed by this speculative work. Where is all of that supposed "UV" radiation going? Why don't we see it? I believe one can only conclude the fellow is a crank . And before someone trots his degrees out for us again, I must note that academic pedigree does not render one immune to academic senility).
While I think we do need some portion of research devoted to cutting-edge ideas, I think a minimum requirement for any serious effort is some nominal level of consistency with well-established work. Extraordinary claims require extraordinary evidence, and it seems apparent that hydrinos do not supply such evidence. In my own opinion, NASA would be far better off devoting their research efforts towards cutting-edge propulsion technologies with a much greater likelihood of success (ie, ion drives, MHD drives, solar sails...)
An object does not need to emit light in order to be seen by a telescope. Just as you can see terrestrial objects all around you which do not emit any significant amount of light in the visble because they reflect and scatter light from the sun, so too can a telescope see planets from reflected light from the sun.
The reason why distant planets, asteroids, and comets are so difficult to see is because they must first reflect light from the sun (going as 1 / r1^2, where r1 is the distance from the sun to the object) and then that reflected light must travel from the object to us (going as 1 / r2^2, where r2 is the distance from the object to us). That means the apparent luminosity scales as
1 / (r1^2 r2^2)
For objects in the outer solar system, r1 ~ r2, so the scaling goes as the inverse fourth power of the distance, as opposed to the usual inverse square law for directly emitted light. When you throw in the additional fact that many of those outer solar system objects like Pluto and Kuiper belt objects are extremely tiny in comparison to the giant planets, thereby reducing their reflecting power even more, you can see why it is difficult to see such distant objects.
I am not familiar with any Hubble observations of Pluto, though I am certain you could get an image if you gathered enough light for a long enough duration. Practically speaking, however, Hubble is primarily useful for getting excellent resolution not possible with ground-based telescopes due to atmospheric effects. Furthermore, it is in very high demand, so that it is only used where ground-based instruments cannot work as well. Ground-based telescopes are still much larger, and have a much greater light-gathering ability than Hubble, however, and are still the instruments of choice when every photon counts, as when astronomers gather specta.
Perhaps this is true with "real world" adventures -- climbing mountains, fighting battles, sailing across uncharted seas.
However, it is totally evident that this comment is meaningless when it comes to accomplishments of the intellect. Einstein didn't risk his life (though perhaps he did stake his career) on the development of General Relativity, but does that remove one iota from the genuine beauty of his theory? The same holds true for accomplishment in all spheres of human intellectual achievement : the sciences, the arts and humanities, and so on. You may argue that it is the "revolutionaries" who inevitably make the greatest discoveries by risking careers and reputations, yet history demonstrates that at least as often, the revolutionaries are purely accidental (ie, Rutherford backscattering, the discovery of the Cosmic Microwave Background, etc.) Yet the accidental nature of the discovery does not tarnish the significance of their results in any manner whatsoever.
seti@home is a scientific mission. You simply cannot judge it on the same basis as scaling a mountain. It is a comparison of apples and oranges, and entirely misses the point of an intellectual achievement. Believe me, if seti@home actually discovers a genuine signal, it will rank among the greatest discoveries of the century, if not of scientific history.
There seems to be a tremendous degree of speculation in the postings I have read. Posters have variously claimed that Amazon's practice either does or does not affect the sales of new books.
Amazon has been selling used books for some time now. Where are the statistics regarding nationwide new and used book sales, relative to Amazon's new and used book sales? Are we really talking about Amazon's used book sales making up a significant fraction of total nationwide book sales each year? If not, why is there such a fuss?
This article provided some interesting suggestions to the origins of the science fiction mythology of Star Wars.
However, the article was majorly flawed in suggesting that merely because the characters, locations, and plots in the films resembled those of previous science fiction novels, George Lucas MUST have ripped them off. While the similarities are striking in some instances, the argument is nonetheless groundless in that there are no direct connections proven between Lucas and the other works. We don't know if he has indeed ever owned or read the works in question, or discussed them with someone who has.
In short, the argument wouldn't hold up in a court of law.
Second, the author misses a major point by making the implicit assumption that the written medium is equivalent to that of film. Even if Lucas had ripped off the cited works entirely, he had still created a new, and powerful work, portrayed on film. There are numerous examples of direct adaptations of books where the film had quite an artistic integrity of its own right ("Dr. Zhivago" and "Remains of the Day" pop immediately to mind), and others (ie, "The Matrix") which blatantly stole from other works, but nonetheless were an outright success in and of their own right.
In short, I think the author of the Salon article secretly wishes he had one tenth the success of Lucas.;-)
Bob
Re:He really isn't a nut
on
Time Travel
·
· Score: 2
Hmmm...
I take it the poster hasn't actually read the book in question!
While authors since Thorne have generally agreed that time travel using wormholes might be theoretically possible, you need negative energy threading the hole to keep it stable. And where do you get a wormhole in the first place?
The challenges here are significant. I can't say whether this fellow's ideas have merit, since the article lacks sufficient technical depth to judge, but a healthy degree of skepticism is in order.
From the Kirkus Review of the same text:
Best to bring a willing suspension of disbelief to this romp by Australian physicist and prolific science popularizer Davies (The Fifth Miracle, 1999, etc.). Build a time machine? Sure, but first you have to construct a wormhole. And not just any wormhole, but an hourglass-shaped one with a neck wide enough to accommodate human girth and without gravity-crushing forces. (After all, you want to survive the trip.) And while you can travel into the future you can only go backward in time as far as the date the wormhole was built-no ecotourism in the dinosaur age, please. How-to? What you need is: (1) a collider of such magnetic megastrength that you can implode a quark-gluon bubble and create a teensy wormhole to warp spacetime; (2) an inflator to enlarge the hole (the trick here is to inject negative energy in the form of anti-gravity matter, maybe using a laser to "squeeze" light); and (3) a differentiator to create a time difference between entry and exit holes (one way is to use the twins paradox well known from relativity theory, then again apply the inflator to produce a human-accommodating wormhole)
This fellow frankly doesn't know his head from his/dev/null.
Anyone following the Wen Ho Lee scandal would know that the whole thing was enormously overblown. In the end, he was let go with a misdimeanor dealing with improper storage of data, and the judge sincerely apologized for the government.
The big difference here is that the conditions were taken to be solid ices (ammonia, etc.), whereas in the Miller-Urey experiment, the conditions were taken to be typical of primordinal planetary atmospheres. Astronomers believe such ices commonly form around dust grains in molecular clouds in interstellar space, which are known to act as catalysts for many other types of molecules. Naturally, the densities of the gases and liquids in the Miller-Urey experiment vastly exceed those in interstellar space by many orders of magnitude.
Now, even though it is novel to see amino acids under such conditions, we should hasten before we leap to any conclusions related to life on Earth or other planets. Dust grains live a very harsh life, even in relatively cold, dense molecular clouds. And then every so often, a shock passes by and will tend to strip the grains of their mantles. Finally, if they survive all of that, they may eventually make their way into a protoplanetary nebula around a star, get smacked together to form protoplanets, and eventually planets like the Earth. It is most unlikely that volatile organic molecules would survive that process. On the other hand, they could be incorporated into comets in the outer reaches of stellar systems, and survive relatively intact, though again subject to the harsh conditions of space.
Personally, I enjoyed the section on Bombadil. Even as creative as Tolkien is, his world sometimes appears to be a bit cramped. (How is that the Shire was so unheard of when everything was within a few weeks by foot?) The section on Bombadil expands his conception of Middle Earth in both space and time.
There is an wonderfully written writeup on Bombadil over here. I quote:
"Likewise, Tom Bombadil was originally a Dutch doll also belonging to Michael Tolkien. John, his brother, put the doll down a lavatory. Bombadil was rescued and Tolkien wrote The Adventures of Tom Bombadil, originally published in Oxford Magazine in 1934. Tolkien later offered to his publishers the idea that Bombadil's story could be expanded into a sequel to The Hobbit, but they didn't bite, so Tom appeared anyway in The Lord of the Rings. Tom makes his debut in the form found in this collection.
The author's method reminds me of the ways in which painful losses are explained in many other cultures. Examples include some Native American mythologies explaining the disappearance of American bison, and German legends about the disappearance of magical creatures from the world. Tolkien's explanation also seems similar to stories told about the rise of iron and technology and the passing away of old traditions, or of the disappearance of the unicorn (it missed the ark), and the rise of the dichotomy that rends myth from objective "reality." One can see the theme at work in the poem "The Last Ship," present in this collection, and in Tolkien's later writing -- elves sailing out of Middle Earth forever, making way for the age of men.
Bombadil's Adventures, however, is a heroic comedy in part about his capacity to escape disappearance -- to endure. One kind of disappearance is that of loneliness, where one fades from the view of others, becomes "mythical," alien, other -- larger than life and yet too small to see, casting no shadow. It is the solitude of being attached to other worlds, worlds where story is more than pastime, worlds where real objects have more than one kind of life and significance, and the loneliness of being unable to weave the other worlds and this one seamlessly together, to make everyone understand."
I think you are confusing my argument with those of other individuals. I am saying the total size of the economy is, in the long run, proportional to the total resources (natural, human, etc.) available to it. The implicit assumption is that in the long run, nations will eventually find ways to solve their internal social and economic problems. The US has no exlusive monopoly on high productivity -- eventually other nations will adapt to our solution, or find even better solutions. It may not happen in a year, or a decade, or possibly even a century. But it will happen. This is certainly true historically -- if you look over very long period of time (say a century or more), productivity has dramatically increased in every modern nation. The US does not have exclusive rights to high productivity, and eventually the unseen hand of economics tends to level the playing field.
Note that Japan's economy will always be limited by the fact that it can only support so many people on its land. It has indeed done very well, but it cannot sustain orders of magnitude higher productivity than the US.
In the 18th century, Alexis DeToqueville made an interesting prediction that Russia and the United States would eventually come to be world powers, based on a similar line of logic. Skeptics at that time looked at the US, which was quite a backwater place, and scoffed at the notion. Their criticisms are very similar to those you pose for China today. It took a very long time for the US to develop the economic, legal, and social institutions to succeed as a predominant world power -- almost two centuries. I would argue the same will prove true for China in the next century. It is a very safe bet.
Oh yes. Per capita GNP. The same measure that Luxembourg beats the US out on. By almost a factor of 2, as well. Over $45,000 per capita for Luxembourg versus a bit over $28,000 for the US. I suppose that makes Luxmberourg the world's most powerful economy in the world.
Seriously though, the buying power of an economy is jointly determined by both the total PPP and PPP per capita. But when it comes to research expenditures, the total size of the economy is what is important. If you can afford to spend a few percent of your economy on research, the total PPP is what is most important. The PPP per capita is also important, but its importance issecondary -- it is related to how much your citizens can afford to be taxed, and so is related to the percent of your total PPP which you can afford to allocate towards research.
This is just an additional development showing China's growing strength. It's economy, based on PPP (purchasing power product, like GNP, but based on equivalent purchasing power instead of relying upon monetary conversions, as GNP does, is the second largest in the world (right behind the US -- 1996 estimate $4,047 billion international dollars, whereas the US had about $6,000 billion international dollars), and is growing much more rapidly than the US PPP -- about 8% a year. In not too long, China will surpass the US as the largest economy on the planet. And it still has a long ways to grow and improve. Eventually it will dwarf the US economy.
What then? China is destined to become the world's largest economy. We simply won't be able to compete in a full-out space race, on a dollar-per-dollar basis. As I see it, there are several possibilities. One is that we will focus our research efforts, much like some European nations have done, in order to excel. (Gran Sasso in Italy, for instance, is a leading high energy detector chamber for high-energy cosmic rays.) Or perhaps we will still manage to shine, simply because we attract better talent from around the world, and do better work with the limited resources available to us. Another possibility is that the US will forge closer ties with other nations -- in North America, Europe, and elsewhere, so that our economy will be able to compete with those of China, India, and Russia, once those nations get their acts together. Lastly, we may indeed be relegated to second (or lower) place on the world's stage, in space and other fields.
While I think this is an interesting experiment in pooling parallel resources, there are also enormous challenges involved.
Anyone who has ever used a parallel machine quickly realizes that in most "interesting" problems, a great deal of inter-processor communication is involved. Even apparently "trivially" parallelizable tasks, such as a CG ray-tracing of a shot from a movie scene, often carry bottlenecks which limit their degree of parallelization. For instance, in the ray-tracing case, even though each ray can indeed be traced independently of the rest, each processor must store the 3D volumetric model it is rendering in memory. Eventually the size of the volumetric model exceeds the memory capacity of the processor, and rays must then be swapped among processors. The same limitations apply to any number of other tasks -- data mining (where one needs to search for correlations in a huge volume of data, too large to be stored on a single processor), simulation (where hyperbolic, or even more bandwidth consumptive, parabolic or elliptic PDEs are often solved), etc...
Achieving good load balance in parallel applications is a key challenge in computational science today. It's quite fair to say that on the current generation of IBM SP2s, which are the most common architecture in high-end computing, the parallel performance for most applications is poor at best. Slapping on an additional machine, with an even tigher bottleneck over the network between them, is not going to magically solve any problems. It is going to push the state-of-the-art of a very LIMITED set of applications a bit further, but a lot more work at the hardware and algorithmic levels needs to be done before MOST applications can really benefit from the scale of these machines.
Ahh... yes, nanotechnology. Constructing molecules. Like diethylthiacyanine,diethylthiacarbocyanine, diethylthiadicarbocyanine, diethylthiatricarbocyanine. Which are molecules. Dyes, actually. Guess what they do? They absorb some wavelengths of light, and emit at others. I suppose that is why they are used as dyes. Every molecule behaves the same way, whether it is artificial or naturally occuring.
Hence, my original argument applies unaltered.
Diffraction and polarization are not significant for large objects subjected to incoherent light. For diffraction to occur, you need a target comparable to the wavelength of light -- not much less or greater. I think most soldiers are bigger than micro-sized bb's.
Oh yes, refraction is part of geometrical optics. But I suppose you didn't realize that.
Unlike some other posters, at least you are in the realm of reality, so I think I'll respond.
Yes, fiber optics can bend light. The problem is that they are highly directional -- only incoming light from a very narrow angle will be piped. If you've ever had to splice two fiber optic cables together, you know just how difficult this is. So while a very narrow cone of light could be routed in principle, most light is just going to be reflected or absorbed as usual.
Infrared camo is more interesting. Yes, you could probably arrange for something like this. You'd effectively be wearing a thermos outfit, and it could potentially get very hot inside. It's unclear to me that you could built up heat for any significant duration without forcing the soldier into heat exhaustion. Yes, you could install an air conditioner, but thermodynamics tells us that even more heat is generated in the process.
Your best bet is probably not to try to capture all of the heat, but retain it briefly in an outer suit layer, and let it equilibrate to the mean temperature of the environment before releasing it. You would still be radiating in the infrared, but you would be nearly indistinguishable from your background.
The original poster was seriously confused. Don't people pay attention in physics classes anymore?
Simple considerations tell us that geometrical optics is an excellent approximation for any large object. The size of the object is much, much greater than a wavelength of light, so optics reduces to tracing rays from your eyeball to the source, and thence reflected or absorbed as the case may be. There is no such thing as "bending" visible light around a macroscopic object. You can make a suit which is nearly fully reflective (not a good stealth tactic -- you would appear like a nice shiny mirror), or nearly absorptive (in which case you would appear black), but there are plenty of ordinary materials that already work quite well for either purpose.
Since I presume that the nanotech folks at MIT are well aware of this fact, I doubt they proposed to "bend light" in their suits. Rather, they are probably going to implement something which Nature has long realized in chameleons and various other creatures : "invisibility" through blending in. Various miniaturized digital cameras could sense the background that a suit was in, and change the colorations on the suit (perhaps using a variation on the "digital ink" concept) accordingly. Hence, a suit could appear sandy-yellow when in the desert, white when in the desert, and camoflouge when in the jungle.
Since we all already doing essentially that when outfitting soldiers (no one wears the bright red of old British regulars anymore), it is unclear whether there is any real advantage to this concept, especially given the cost. Particularly since, to anyone equipped with infrared night vision goggles, every body temperature objects glow like a beacon.
I don't agree with this author's assessment. The type of "parallelism" involved in the AltiVec is SIMD -- single instruction, multiple data. It's the same kind of parallelism which Cray pioneered over 25 years ago. While in the early days, a great deal of hand-tuning was required, leading to such memorable Cray-specific replacement constructs as the vectorized Cray vector merges (CVMGT, CVMGZ, CVMGP, etc...) in place of non-vectorized If-Then's, great strides were made in Cray's compilers over the last few years. You could get very reasonable vectorized performance for most numerically intensive codes straight out of the compiler, without any modifications at all. With a bit of profiling and additional compiler directives, you could get excellent performance indeed.
The plain fact of the matter is that SIMD is MUCH, MUCH easier than doing distributed parallelization. It took Cray about 20 years to really get it right, so given how new the Altivec is, let's give Apple and company a few years to see how much they can accomplish.
I think this author is giving Pons and Fleischman a bit too much credit. While it is certainly true that both were well-respected chemists, their work on cold fusion was at best sloppy, and at worst, both inaccurate and deceptive.
Some facts in the case:
1) They used heavy water (D_2O) in their experiments. Steven Koonin, a theoretical nuclear physicist, confronted them at a conference with a simple question : Had they done the simple test of using ordinary water? (Which wouldn't have produced fusion.) The answer was damning : No, they hadn't even thought of it.
2) Their work detecting neutrons (a certain biproduct of fusion, cold or not) from their experiment was presented in a most misleading fashion at conferences. They displayed figures without labels, and did not perform proper calibrations of their detection -- it was impossible to determine whether their "signals" were simply background. (Of course, their detections were orders of magnitude too small -- had the signal been commensurate with the heat produced, they would have been dead from the radioactivity.)
3) Moreover, when confronted with the the fact that their "signals" lacked a crucial feature known as the "Compton edge" (as any physics major has observed this in their labs classes) which must accompany any real signal, they further lopped off their plots so as to show only the spurious peak, making it impossible to realize that they were lacking the Compton edge.
4) They presented their research to the press prior to publication. This turned the scientific process into a media circus, impeding progress, and doing immense damage to the public conception of the scientfic process.
5) Rather than openly describing their methodology (a standard practice in any scientific discipline) to allow other researchers to reproduce their work, they kept their methods secret. I recall several groups were forced to set up their experiments using bits of video footage from the evening news.
6) Later claims by a number of researchers that some extraneous heat was being produced is quite a distinct issue from the original work of Pons and Fleischman. Pons and Fleischman's original claims were much bolder -- they claimed a very large extraneous heat output. It was later determined that they had simply done their calorimetry accounting wrong (a common error in calorimetry, but nonetheless surprising, because they were experts in calorimetry).
In sum, the way Pons and Fleischman conducted their work on cold fusion was a prime example of how science is not to be done. The image of Pons and Fleischman as two revolutionary figures taking on the physics establishment is simply not commensurate with the facts of the case -- they practiced very poor science, by the standards of any scientific discipline.
I think both of the tests you mention are not really confirmation of the fact that they have actually formed anti-hydrogen.
Why? Let's assume that, for some reason, the atoms in question were not anti-hydrogen, but simply plain run-of-the-mill hydrogen.
How do the spectra compare? The spectrum of hydrogen should be exactly identical to that of anti-hydrogen. Nope. Can't use it as a confirmation of the antimatter state.
How about net charge? Well, hydrogen also has zero charge. Nope, can't use net charge as a confirmation either.
In fact, your argument is not quite correct. Hydrogen atoms do possess a net magnetic moment (primarily due to the spin and orbital angular momentum of the electron, though the latter is zero in the ground state) and therefore do move in a magnetic field. In fact, that was the entire basis of the classic Stern-Gerlach experiment.
I've heard that experimentalists might be able to confirm the existence of anti-hydrogen by smashing the atoms in question against a wall, and looking for characteristic gamma rays. If one knew the initial state were either hydrogen or anti-hydrogen, then one could be assured upon seeing the gamma rays, that the initial state was indeed anti-hydrogen. The problem with this approach is that it destroys the antimatter atoms in the process, so that you are not able to subsequently use them in other experiments.
Slashdot Mirror
1) The highest per-capita consumption occurs in the first world. (see below)
2) The population of the first world is rapidly shrinking, and will amount to a small fraction of the total world population by 2050. (According to the UN. See this link for details.)
3) By 2050, even the 3rd world population is expected to reach equilibrium, so that the entire world population will actually begin to decline.
Taken together, it seems unlikely to me that the conditions stated by the WWF may actually come about, unless the 3rd world population increases its consumption dramatically, or the UN study is substantially incorrect. This is because, even though the world population is expected to increase from 6 billion to 9 billion by 2050, that additional growth will occur almost exclusively outside of Western nations. Significantly, the population of the first world will actually diminish. Now, the report itself states
"America's consumption 'footprint' is 12.2 hectares per head of population compared to the UK's 6.29ha while Western Europe as a whole stands at 6.28ha. In Ethiopia the figure is 2ha, falling to just half a hectare for Burundi, the country that consumes least resources."
So if indeed the third world consumes a large factor (an order of magnitude!) less "footprint" than the Western nations, it would seem to me that the world might actually be better off by 2050 : they are, quite simply, more efficient at using existing resources.
Bob
Is/are X consistent with our experimental knowledge of nature?
Where "X" is any hypothesis you wish to check. It can be the "hydrino hypothesis", or it can be the Schrodinger equation.
Now, it is a very simple and straightforwards matter to set up an experimental apparatus to observe the emission lines from hydrogen. Many of us have done it in college or even high schools labs. Each transition is seen in the spectrum.
The result? Completely consistent with the Schrodinger equation (or even the previous simpler Bohr model). If there were an energy state lower than the n = 1 quantum state, it would produce a very visible emission line, which is not seen. This is a very glaring inconstency which is not apparently addressed by this speculative work. Where is all of that supposed "UV" radiation going? Why don't we see it? I believe one can only conclude the fellow is a crank . And before someone trots his degrees out for us again, I must note that academic pedigree does not render one immune to academic senility).
While I think we do need some portion of research devoted to cutting-edge ideas, I think a minimum requirement for any serious effort is some nominal level of consistency with well-established work. Extraordinary claims require extraordinary evidence, and it seems apparent that hydrinos do not supply such evidence. In my own opinion, NASA would be far better off devoting their research efforts towards cutting-edge propulsion technologies with a much greater likelihood of success (ie, ion drives, MHD drives, solar sails...)
Bob
The reason why distant planets, asteroids, and comets are so difficult to see is because they must first reflect light from the sun (going as 1 / r1^2, where r1 is the distance from the sun to the object) and then that reflected light must travel from the object to us (going as 1 / r2^2, where r2 is the distance from the object to us). That means the apparent luminosity scales as
1 / (r1^2 r2^2)
For objects in the outer solar system, r1 ~ r2, so the scaling goes as the inverse fourth power of the distance, as opposed to the usual inverse square law for directly emitted light. When you throw in the additional fact that many of those outer solar system objects like Pluto and Kuiper belt objects are extremely tiny in comparison to the giant planets, thereby reducing their reflecting power even more, you can see why it is difficult to see such distant objects.
I am not familiar with any Hubble observations of Pluto, though I am certain you could get an image if you gathered enough light for a long enough duration. Practically speaking, however, Hubble is primarily useful for getting excellent resolution not possible with ground-based telescopes due to atmospheric effects. Furthermore, it is in very high demand, so that it is only used where ground-based instruments cannot work as well. Ground-based telescopes are still much larger, and have a much greater light-gathering ability than Hubble, however, and are still the instruments of choice when every photon counts, as when astronomers gather specta.
Bob
Perhaps this is true with "real world" adventures -- climbing mountains, fighting battles, sailing across uncharted seas.
However, it is totally evident that this comment is meaningless when it comes to accomplishments of the intellect. Einstein didn't risk his life (though perhaps he did stake his career) on the development of General Relativity, but does that remove one iota from the genuine beauty of his theory? The same holds true for accomplishment in all spheres of human intellectual achievement : the sciences, the arts and humanities, and so on. You may argue that it is the "revolutionaries" who inevitably make the greatest discoveries by risking careers and reputations, yet history demonstrates that at least as often, the revolutionaries are purely accidental (ie, Rutherford backscattering, the discovery of the Cosmic Microwave Background, etc.) Yet the accidental nature of the discovery does not tarnish the significance of their results in any manner whatsoever.
seti@home is a scientific mission. You simply cannot judge it on the same basis as scaling a mountain. It is a comparison of apples and oranges, and entirely misses the point of an intellectual achievement. Believe me, if seti@home actually discovers a genuine signal, it will rank among the greatest discoveries of the century, if not of scientific history.
Bob
Amazon has been selling used books for some time now. Where are the statistics regarding nationwide new and used book sales, relative to Amazon's new and used book sales? Are we really talking about Amazon's used book sales making up a significant fraction of total nationwide book sales each year? If not, why is there such a fuss?
Bob
This article provided some interesting suggestions to the origins of the science fiction mythology of Star Wars.
;-)
However, the article was majorly flawed in suggesting that merely because the characters, locations, and plots in the films resembled those of previous science fiction novels, George Lucas MUST have ripped them off. While the similarities are striking in some instances, the argument is nonetheless groundless in that there are no direct connections proven between Lucas and the other works. We don't know if he has indeed ever owned or read the works in question, or discussed them with someone who has.
In short, the argument wouldn't hold up in a court of law.
Second, the author misses a major point by making the implicit assumption that the written medium is equivalent to that of film. Even if Lucas had ripped off the cited works entirely, he had still created a new, and powerful work, portrayed on film. There are numerous examples of direct adaptations of books where the film had quite an artistic integrity of its own right ("Dr. Zhivago" and "Remains of the Day" pop immediately to mind), and others (ie, "The Matrix") which blatantly stole from other works, but nonetheless were an outright success in and of their own right.
In short, I think the author of the Salon article secretly wishes he had one tenth the success of Lucas.
Bob
Hmmm...
:
I take it the poster hasn't actually read the book in question!
While authors since Thorne have generally agreed that time travel using wormholes might be theoretically possible, you need negative energy threading the hole to keep it stable. And where do you get a wormhole in the first place?
The challenges here are significant. I can't say whether this fellow's ideas have merit, since the article lacks sufficient technical depth to judge, but a healthy degree of skepticism is in order.
From the Kirkus Review of the same text
Best to bring a willing suspension of disbelief to this romp by Australian physicist and prolific science popularizer Davies (The Fifth Miracle, 1999, etc.). Build a time machine? Sure, but first you have to construct a wormhole. And not just any wormhole, but an hourglass-shaped one with a neck wide enough to accommodate human girth and without gravity-crushing forces. (After all, you want to survive the trip.) And while you can travel into the future you can only go backward in time as far as the date the wormhole was built-no ecotourism in the dinosaur age, please. How-to? What you need is: (1) a collider of such magnetic megastrength that you can implode a quark-gluon bubble and create a teensy wormhole to warp spacetime; (2) an inflator to enlarge the hole (the trick here is to inject negative energy in the form of anti-gravity matter, maybe using a laser to "squeeze" light); and (3) a differentiator to create a time difference between entry and exit holes (one way is to use the twins paradox well known from relativity theory, then again apply the inflator to produce a human-accommodating wormhole)
This fellow frankly doesn't know his head from his /dev/null.
Anyone following the Wen Ho Lee scandal would know that the whole thing was enormously overblown. In the end, he was let go with a misdimeanor dealing with improper storage of data, and the judge sincerely apologized for the government.
Bob
The big difference here is that the conditions were taken to be solid ices (ammonia, etc.), whereas in the Miller-Urey experiment, the conditions were taken to be typical of primordinal planetary atmospheres. Astronomers believe such ices commonly form around dust grains in molecular clouds in interstellar space, which are known to act as catalysts for many other types of molecules. Naturally, the densities of the gases and liquids in the Miller-Urey experiment vastly exceed those in interstellar space by many orders of magnitude.
Now, even though it is novel to see amino acids under such conditions, we should hasten before we leap to any conclusions related to life on Earth or other planets. Dust grains live a very harsh life, even in relatively cold, dense molecular clouds. And then every so often, a shock passes by and will tend to strip the grains of their mantles. Finally, if they survive all of that, they may eventually make their way into a protoplanetary nebula around a star, get smacked together to form protoplanets, and eventually planets like the Earth. It is most unlikely that volatile organic molecules would survive that process. On the other hand, they could be incorporated into comets in the outer reaches of stellar systems, and survive relatively intact, though again subject to the harsh conditions of space.
Bob
Personally, I enjoyed the section on Bombadil. Even as creative as Tolkien is, his world sometimes appears to be a bit cramped. (How is that the Shire was so unheard of when everything was within a few weeks by foot?) The section on Bombadil expands his conception of Middle Earth in both space and time.
:
There is an wonderfully written writeup on Bombadil over here. I quote
"Likewise, Tom Bombadil was originally a Dutch doll also belonging to Michael Tolkien. John, his brother, put the doll down a lavatory. Bombadil was rescued and Tolkien wrote The Adventures of Tom Bombadil, originally published in Oxford Magazine in 1934. Tolkien later offered to his publishers the idea that Bombadil's story could be expanded into a sequel to The Hobbit, but they didn't bite, so Tom appeared anyway in The Lord of the Rings. Tom makes his debut in the form found in this collection.
The author's method reminds me of the ways in which painful losses are explained in many other cultures. Examples include some Native American mythologies explaining the disappearance of American bison, and German legends about the disappearance of magical creatures from the world. Tolkien's explanation also seems similar to stories told about the rise of iron and technology and the passing away of old traditions, or of the disappearance of the unicorn (it missed the ark), and the rise of the dichotomy that rends myth from objective "reality." One can see the theme at work in the poem "The Last Ship," present in this collection, and in Tolkien's later writing -- elves sailing out of Middle Earth forever, making way for the age of men.
Bombadil's Adventures, however, is a heroic comedy in part about his capacity to escape disappearance -- to endure. One kind of disappearance is that of loneliness, where one fades from the view of others, becomes "mythical," alien, other -- larger than life and yet too small to see, casting no shadow. It is the solitude of being attached to other worlds, worlds where story is more than pastime, worlds where real objects have more than one kind of life and significance, and the loneliness of being unable to weave the other worlds and this one seamlessly together, to make everyone understand."
Bob
Brian :
I think you are confusing my argument with those of other individuals. I am saying the total size of the economy is, in the long run, proportional to the total resources (natural, human, etc.) available to it. The implicit assumption is that in the long run, nations will eventually find ways to solve their internal social and economic problems. The US has no exlusive monopoly on high productivity -- eventually other nations will adapt to our solution, or find even better solutions. It may not happen in a year, or a decade, or possibly even a century. But it will happen. This is certainly true historically -- if you look over very long period of time (say a century or more), productivity has dramatically increased in every modern nation. The US does not have exclusive rights to high productivity, and eventually the unseen hand of economics tends to level the playing field.
Note that Japan's economy will always be limited by the fact that it can only support so many people on its land. It has indeed done very well, but it cannot sustain orders of magnitude higher productivity than the US.
In the 18th century, Alexis DeToqueville made an interesting prediction that Russia and the United States would eventually come to be world powers, based on a similar line of logic. Skeptics at that time looked at the US, which was quite a backwater place, and scoffed at the notion. Their criticisms are very similar to those you pose for China today. It took a very long time for the US to develop the economic, legal, and social institutions to succeed as a predominant world power -- almost two centuries. I would argue the same will prove true for China in the next century. It is a very safe bet.
Bob
Oh yes. Per capita GNP. The same measure that Luxembourg beats the US out on. By almost a factor of 2, as well. Over $45,000 per capita for Luxembourg versus a bit over $28,000 for the US. I suppose that makes Luxmberourg the world's most powerful economy in the world.
Seriously though, the buying power of an economy is jointly determined by both the total PPP and PPP per capita. But when it comes to research expenditures, the total size of the economy is what is important. If you can afford to spend a few percent of your economy on research, the total PPP is what is most important. The PPP per capita is also important, but its importance issecondary -- it is related to how much your citizens can afford to be taxed, and so is related to the percent of your total PPP which you can afford to allocate towards research.
Bob
This is just an additional development showing China's growing strength. It's economy, based on PPP (purchasing power product, like GNP, but based on equivalent purchasing power instead of relying upon monetary conversions, as GNP does, is the second largest in the world (right behind the US -- 1996 estimate $4,047 billion international dollars, whereas the US had about $6,000 billion international dollars), and is growing much more rapidly than the US PPP -- about 8% a year. In not too long, China will surpass the US as the largest economy on the planet. And it still has a long ways to grow and improve. Eventually it will dwarf the US economy.
What then? China is destined to become the world's largest economy. We simply won't be able to compete in a full-out space race, on a dollar-per-dollar basis. As I see it, there are several possibilities. One is that we will focus our research efforts, much like some European nations have done, in order to excel. (Gran Sasso in Italy, for instance, is a leading high energy detector chamber for high-energy cosmic rays.) Or perhaps we will still manage to shine, simply because we attract better talent from around the world, and do better work with the limited resources available to us. Another possibility is that the US will forge closer ties with other nations -- in North America, Europe, and elsewhere, so that our economy will be able to compete with those of China, India, and Russia, once those nations get their acts together. Lastly, we may indeed be relegated to second (or lower) place on the world's stage, in space and other fields.
You take your pick.
Bob
While I think this is an interesting experiment in pooling parallel resources, there are also enormous challenges involved.
Anyone who has ever used a parallel machine quickly realizes that in most "interesting" problems, a great deal of inter-processor communication is involved. Even apparently "trivially" parallelizable tasks, such as a CG ray-tracing of a shot from a movie scene, often carry bottlenecks which limit their degree of parallelization. For instance, in the ray-tracing case, even though each ray can indeed be traced independently of the rest, each processor must store the 3D volumetric model it is rendering in memory. Eventually the size of the volumetric model exceeds the memory capacity of the processor, and rays must then be swapped among processors. The same limitations apply to any number of other tasks -- data mining (where one needs to search for correlations in a huge volume of data, too large to be stored on a single processor), simulation (where hyperbolic, or even more bandwidth consumptive, parabolic or elliptic PDEs are often solved), etc...
Achieving good load balance in parallel applications is a key challenge in computational science today. It's quite fair to say that on the current generation of IBM SP2s, which are the most common architecture in high-end computing, the parallel performance for most applications is poor at best. Slapping on an additional machine, with an even tigher bottleneck over the network between them, is not going to magically solve any problems. It is going to push the state-of-the-art of a very LIMITED set of applications a bit further, but a lot more work at the hardware and algorithmic levels needs to be done before MOST applications can really benefit from the scale of these machines.
Bob
Ahh... yes, nanotechnology. Constructing molecules. Like diethylthiacyanine,diethylthiacarbocyanine, diethylthiadicarbocyanine, diethylthiatricarbocyanine. Which are molecules. Dyes, actually. Guess what they do? They absorb some wavelengths of light, and emit at others. I suppose that is why they are used as dyes. Every molecule behaves the same way, whether it is artificial or naturally occuring.
Hence, my original argument applies unaltered.
Diffraction and polarization are not significant for large objects subjected to incoherent light. For diffraction to occur, you need a target comparable to the wavelength of light -- not much less or greater. I think most soldiers are bigger than micro-sized bb's.
Oh yes, refraction is part of geometrical optics. But I suppose you didn't realize that.
Bob
This topic has already been addressed in another thread.
;-)
Spouting is having an uninformed opinion.
Bob
Unlike some other posters, at least you are in the realm of reality, so I think I'll respond.
Yes, fiber optics can bend light. The problem is that they are highly directional -- only incoming light from a very narrow angle will be piped. If you've ever had to splice two fiber optic cables together, you know just how difficult this is. So while a very narrow cone of light could be routed in principle, most light is just going to be reflected or absorbed as usual.
Infrared camo is more interesting. Yes, you could probably arrange for something like this. You'd effectively be wearing a thermos outfit, and it could potentially get very hot inside. It's unclear to me that you could built up heat for any significant duration without forcing the soldier into heat exhaustion. Yes, you could install an air conditioner, but thermodynamics tells us that even more heat is generated in the process.
Your best bet is probably not to try to capture all of the heat, but retain it briefly in an outer suit layer, and let it equilibrate to the mean temperature of the environment before releasing it. You would still be radiating in the infrared, but you would be nearly indistinguishable from your background.
Bob
Uhhh.. yeah, if you were a black hole. I think we can safely rule out that possibility here.
/.'ers become so clueless??
LOL
When did
The original poster was seriously confused. Don't people pay attention in physics classes anymore?
Simple considerations tell us that geometrical optics is an excellent approximation for any large object. The size of the object is much, much greater than a wavelength of light, so optics reduces to tracing rays from your eyeball to the source, and thence reflected or absorbed as the case may be. There is no such thing as "bending" visible light around a macroscopic object. You can make a suit which is nearly fully reflective (not a good stealth tactic -- you would appear like a nice shiny mirror), or nearly absorptive (in which case you would appear black), but there are plenty of ordinary materials that already work quite well for either purpose.
Since I presume that the nanotech folks at MIT are well aware of this fact, I doubt they proposed to "bend light" in their suits. Rather, they are probably going to implement something which Nature has long realized in chameleons and various other creatures : "invisibility" through blending in. Various miniaturized digital cameras could sense the background that a suit was in, and change the colorations on the suit (perhaps using a variation on the "digital ink" concept) accordingly. Hence, a suit could appear sandy-yellow when in the desert, white when in the desert, and camoflouge when in the jungle.
Since we all already doing essentially that when outfitting soldiers (no one wears the bright red of old British regulars anymore), it is unclear whether there is any real advantage to this concept, especially given the cost. Particularly since, to anyone equipped with infrared night vision goggles, every body temperature objects glow like a beacon.
Bob
I don't agree with this author's assessment. The type of "parallelism" involved in the AltiVec is SIMD -- single instruction, multiple data. It's the same kind of parallelism which Cray pioneered over 25 years ago. While in the early days, a great deal of hand-tuning was required, leading to such memorable Cray-specific replacement constructs as the vectorized Cray vector merges (CVMGT, CVMGZ, CVMGP, etc...) in place of non-vectorized If-Then's, great strides were made in Cray's compilers over the last few years. You could get very reasonable vectorized performance for most numerically intensive codes straight out of the compiler, without any modifications at all. With a bit of profiling and additional compiler directives, you could get excellent performance indeed.
The plain fact of the matter is that SIMD is MUCH, MUCH easier than doing distributed parallelization. It took Cray about 20 years to really get it right, so given how new the Altivec is, let's give Apple and company a few years to see how much they can accomplish.
Bob
This anonymous poster is entirely correct, and the parent is incorrect. I'd mod him up myself, if I had any moderator points left.
Bob
I think this author is giving Pons and Fleischman a bit too much credit. While it is certainly true that both were well-respected chemists, their work on cold fusion was at best sloppy, and at worst, both inaccurate and deceptive.
:
Some facts in the case
1) They used heavy water (D_2O) in their experiments. Steven Koonin, a theoretical nuclear physicist, confronted them at a conference with a simple question : Had they done the simple test of using ordinary water? (Which wouldn't have produced fusion.) The answer was damning : No, they hadn't even thought of it.
2) Their work detecting neutrons (a certain biproduct of fusion, cold or not) from their experiment was presented in a most misleading fashion at conferences. They displayed figures without labels, and did not perform proper calibrations of their detection -- it was impossible to determine whether their "signals" were simply background. (Of course, their detections were orders of magnitude too small -- had the signal been commensurate with the heat produced, they would have been dead from the radioactivity.)
3) Moreover, when confronted with the the fact that their "signals" lacked a crucial feature known as the "Compton edge" (as any physics major has observed this in their labs classes) which must accompany any real signal, they further lopped off their plots so as to show only the spurious peak, making it impossible to realize that they were lacking the Compton edge.
4) They presented their research to the press prior to publication. This turned the scientific process into a media circus, impeding progress, and doing immense damage to the public conception of the scientfic process.
5) Rather than openly describing their methodology (a standard practice in any scientific discipline) to allow other researchers to reproduce their work, they kept their methods secret. I recall several groups were forced to set up their experiments using bits of video footage from the evening news.
6) Later claims by a number of researchers that some extraneous heat was being produced is quite a distinct issue from the original work of Pons and Fleischman. Pons and Fleischman's original claims were much bolder -- they claimed a very large extraneous heat output. It was later determined that they had simply done their calorimetry accounting wrong (a common error in calorimetry, but nonetheless surprising, because they were experts in calorimetry).
In sum, the way Pons and Fleischman conducted their work on cold fusion was a prime example of how science is not to be done. The image of Pons and Fleischman as two revolutionary figures taking on the physics establishment is simply not commensurate with the facts of the case -- they practiced very poor science, by the standards of any scientific discipline.
Bob
My favorite one of these is the "Naturist Journal : You May Encounter Nude News Beyond This Point" : http://www.naturistjournal.com/.
I kid you not.
Chris :
I think both of the tests you mention are not really confirmation of the fact that they have actually formed anti-hydrogen.
Why? Let's assume that, for some reason, the atoms in question were not anti-hydrogen, but simply plain run-of-the-mill hydrogen.
How do the spectra compare? The spectrum of hydrogen should be exactly identical to that of anti-hydrogen. Nope. Can't use it as a confirmation of the antimatter state.
How about net charge? Well, hydrogen also has zero charge. Nope, can't use net charge as a confirmation either.
In fact, your argument is not quite correct. Hydrogen atoms do possess a net magnetic moment (primarily due to the spin and orbital angular momentum of the electron, though the latter is zero in the ground state) and therefore do move in a magnetic field. In fact, that was the entire basis of the classic Stern-Gerlach experiment.
I've heard that experimentalists might be able to confirm the existence of anti-hydrogen by smashing the atoms in question against a wall, and looking for characteristic gamma rays. If one knew the initial state were either hydrogen or anti-hydrogen, then one could be assured upon seeing the gamma rays, that the initial state was indeed anti-hydrogen. The problem with this approach is that it destroys the antimatter atoms in the process, so that you are not able to subsequently use them in other experiments.
Bob