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Natural Science Forum / Physics / Optics / August 2005What's Wrong With This Joke (was Tandem/Speed Limit)
In the group alt.folklore.computers: On Wed, 24 Aug 2005 22:47:01 GMT, Philip Nasadowski <nasadowsk@nospam.usermail.com> wrote, in part: >I once saw a chart >by a locomotive manufacturer proposing a gas turbine/battery hybrid >locomotive (Railpower - they're still hybrid but moved away from >turbines). One 'advantage' to the turbine was that the fuel economy on >them was improving faster than diesels, historically. Their (linear!) >chart showed an interesting prediction: by 2015, gas turbine specific >fuel consumption would cross into a negative number. Not like GE or EMD >would care - only a few years later, rail class diesels would, too. >Admittingly, the idea of an engine that makes more fuel than it burns is >cute, but it's generally not practical :) In the group sci.optics: On Sat, 20 Aug 2005 04:01:42 -0000, Skywise <into@oblivion.nothing.com> wrote, in part: >http://www.livescience.com/technology/050819_fastlight.html > >"Scientists Mess with the Speed of Light" > >Ok, so I'm reading this article and they're talking about >making light go faster than the speed of light in optical >fibers. I'm thinking they've got to be talking about phase >velocity, which they eventually do. But there's this one >paragraph that has me puzzled, > > "Light in a vacuum travels at approximately 186,000 miles > per second, but a popular misconception is that, according > to Einstein’s special theory of relativity, _nothing_ in the > universe can travel faster than this speed." > >A "popular misconception"? uhhhh....when did this change? When I was a young man at University, I remember being told the following joke: A scientific journal (I believe it may have been _Physical Review D_) had been growing thicker over the last few years. Also, the quality and importance of the papers that appeared in it were felt, in some quarters, to have declined. Thus, someone extrapolated the trend linearly, finding that in X number of years, a library shelf of this particular journal would grow at a speed faster than the speed of light. However, due to the declining quality of the articles, the laws of Special Relativity would not be violated, because the journal's articles would not contain any information. Obviously, of course, the linear extrapolation is likely to break down in any event - which relates to the topic of the thread in alt.folklore.computers. But something else spoiled the joke for me to an extent. Because in one sense, all along, it is a "popular misconception" that nothing can travel faster than light. According to the Special Theory of Relativity, no mass, no energy, and no information can travel faster than light. But there are 'things' that aren't *real physical objects* or otherwise entities that are limited by this. For example, if I point a flashlight at a distant screen, and quickly sweep it across the screen, the spot of light on the screen _could_ travel faster than light. This is because the spot of light isn't really an object, it is just where successive real objects - the photons from my flashlight - hit the screen. The spot where two searchlight beams cross. A line of fire - as opposed to the bullets actually being fired. A shadow. These things, which can be called pseudo-objects, are not causally linked to each other, but they are related, being caused by a common source. As it happens, the leading edge of the advancing line of journals on a shelf is _also_ a pseudo-object. The individual issues of Physical Review D would, however poor the quality of their articles, have mass and energy - and they would contain information, even if about the random letters pounded by monkeys on typewriters. And so each individual issue would move from the mailroom to the library shelves at a speed slower than that of light. But millions of librarians in a row stretching for miles, almost in unison, could each put an issue of the journal on the shelf one after the other so that the position of the most recently shelved journal races ahead at faster than the speed of light - without any physical law being violated. John Savard http://www.quadibloc.com/index.html > When I was a young man at University, I remember being told the > following joke: > [See up-thread for entertaining post, snipped for brevity] Also see http://www.nationmaster.com/encyclopedia/Thiotimoline  SignatureEric.Sosman@sun.com > http://www.nationmaster.com/encyclopedia/Thiotimoline Asimov's "The Endochronic Properties of Resublimated Thiotimoline", I'm guessing? Classic. Read it when I was about 11, and loved it. Martin SignatureM.A.Poyser Tel.: 07967 110890 Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie > But millions of librarians in a row stretching for miles, almost in > unison, could each put an issue of the journal on the shelf one after > the other so that the position of the most recently shelved journal > races ahead at faster than the speed of light - without any physical law > being violated. So if one librarian inserts and removes a volume according to some pattern, modulating the endpoint, that doesn't convey information? Or are librarians destined to become FTL telegraphers? The classic FTL example I can recall mentioned in electronics class is the pattern established in a waveguide before the RF passes through it. Not a microwave/radar engineer so don't ask me for details. Hmm, doesn't the excited electron jumping between shells in a laser happen faster than light as well? Jack Peacock >> But millions of librarians in a row stretching for miles, almost in >> unison, could each put an issue of the journal on the shelf one after [quoted text clipped - 5 lines] >modulating the endpoint, that doesn't convey information? Or are librarians >destined to become FTL telegraphers? Most of that information would be outside the event horizon for a real observer located at some arbitrary, but real, point along the line of journals. This would of course assume that the shelves don't collapse and the journals descend into a black hole. >The classic FTL example I can recall mentioned in electronics class is the >pattern established in a waveguide before the RF passes through it. Not a >microwave/radar engineer so don't ask me for details. Hmm, doesn't the >excited electron jumping between shells in a laser happen faster than light >as well? That last one is beyond me. I never read anything that tried seriously to reconsile QM and relativity. -- mrr >> But millions of librarians in a row stretching for miles, almost in >> unison, could each put an issue of the journal on the shelf one after [quoted text clipped - 9 lines] >pattern established in a waveguide before the RF passes through it. Not a >microwave/radar engineer so don't ask me for details. Isn't this called a phase velocity? There is a name for it. > .. Hmm, doesn't the >excited electron jumping between shells in a laser happen faster than light >as well? I don't think there is a thingie that jumps. It's a field, not a ball. /BAH snip-- >The classic FTL example I can recall mentioned in electronics class is the >pattern established in a waveguide before the RF passes through it. Not a >microwave/radar engineer so don't ask me for details. i believe this expresses the difference between phase and group velocity in a waveguide, the group velocity is less than the speed of light and the phase velocity is greater >> But millions of librarians in a row stretching for miles, almost in >> unison, could each put an issue of the journal on the shelf one after [quoted text clipped - 5 lines] >modulating the endpoint, that doesn't convey information? Or are librarians >destined to become FTL telegraphers? This is a random event that is at most able to convey information FTL than is the "writing speed" of a giant-size wide-screen oscilloscope with a small ray gun that responds well to high frequencies. Suppose you have an oscilloscope that has the "time base" or the "X Value" angularly move a laser east-west, and the "Y-Input" (whatever signal varying with time, possibly an oscillating signal with frequency a multiple of the X-retracing frequency) angularly moves the laser north-south. Suppose the laser is moved angularly back-and-forth east-west .3 degree 2,000 times a second, and does so north-south .3 degree 8,000 times a second, with movements being peak-to-peak values and the movements being sinusoidal. I surely believe this can actually be done! For the sake of this argument, this hypothetical experiment can angularly move a mirror that reflects a laser beam in lieu of moving the laser in such a fashion. Movement of the mirror has the additional advantage of only having to have angular movement of half the angular movement of the reflected laser beam! Now, aim the laser at the moon, 235,000 or whatever miles away!!! Looks like this writes a "Lissajous" pattern on the moon, with overall dimensions roughly square and able to fit on the moon. As in about 1230 miles on each side of the "square". This surely sounds not only physically possible, but outright achievable!!! So the beam moves north-south along the lunar surface up-and-down 1230 miles 8,000 times a second, 9.84 million miles a second. If fastest speed coincides with fastest east-west speed of 1/4 that, then the "dot" moves at 10.14 million miles per second - and "C" is .186 272 million miles per second! So what does this prove some movement known to move faster than C? Surely this is not even an argument of transmitting info faster than C! And if a big bunch of librarians with good stopwatches reshelve books in a huge library in some "Wave" that travels faster than C, this does not indicate info travelling fater than C... For that matter, librarians downstream of a disruption of such a FTL "reshelving wave" restore the "FTL reshelving wave" before they learn of the disruption! >The classic FTL example I can recall mentioned in electronics class is the >pattern established in a waveguide before the RF passes through it. I don't see how anything travels faster than light when all superluminal speed is of absence of anything. However, "waveguide" reminds me of this "phase velocity-vs-group velocity" business, since a common form of waveguides is a place where this often occurs. <SNIP> >Hmm, doesn't the excited electron jumping between shells in a laser >happen faster than light as well? Given the amount of time not only for the jump to occur but also the amount of time required to wait for the jump to occur or to respond to this jump occurring, I surely believe this to nopt believe this to be a mechanism to transmit info FTL from the cause of the jump to the output of whatever detected that the jump has occurred. > Jack Peacock - Don Klipstein (don@misty.com) > Because in one sense, all along, it is a "popular misconception" that > nothing can travel faster than light. According to the Special Theory of > Relativity, no mass, no energy, and no information can travel faster > than light. Anything with imaginary rest mass can (and must) travel faster than the speed of light if the LF contractions hold good. Such particles used to be called tachyons, I'm not sure if they have been ruled out yet. SignatureC:>WIN | Directable Mirror Arrays The computer obeys and wins. | A better way to focus the sun You lose and Bill collects. | licences available see | http://www.sohara.org/ > Anything with imaginary rest mass can (and must) travel faster than >the speed of light if the LF contractions hold good. Such particles used >to be called tachyons, I'm not sure if they have been ruled out yet. Even when tachyons were considered, it was known that they could not be detected or manipulated, since doing so would allow faster-than-light communications, which would permit backwards in time communications as well, since tachyons were fully subject to Special Relativity. John Savard http://www.quadibloc.com/index.html >> Anything with imaginary rest mass can (and must) travel faster than >>the speed of light if the LF contractions hold good. Such particles used [quoted text clipped - 4 lines] >communications, which would permit backwards in time communications as >well, since tachyons were fully subject to Special Relativity. You are 3c distance away from me. You hold a 9 of spades. You hold the high card. I flip a king of spades. I instantaneouly hold the high card. This "information" transferred at faster than the speed of light in a vacuum. /BAH > You are 3c distance away from me. You hold a 9 of spades. > You hold the high card. > > I flip a king of spades. I instantaneouly hold the high card. > This "information" transferred at faster than the speed of light > in a vacuum. How do you know your opponent isn't now holding a 45 which would make yours the low hand? >> You are 3c distance away from me. You hold a 9 of spades. >> You hold the high card. [quoted text clipped - 5 lines] >How do you know your opponent isn't now holding a 45 which would make >yours the low hand? More to the point. Since the information transferred is of a visual type it is transmitted by light at is thusly non-instantaneous. enri >>> You are 3c distance away from me. You hold a 9 of spades. >>> You hold the high card. [quoted text clipped - 8 lines] >More to the point. Since the information transferred is of a visual >type it is transmitted by light at is thusly non-instantaneous. No. The information is "high card". Before the second draw the high card was the 9 of spades. This was a bad analogy but I read it some place to explain conservation of spin. /BAH > > Anything with imaginary rest mass can (and must) travel faster than > >the speed of light if the LF contractions hold good. Such particles used [quoted text clipped - 4 lines] > communications, which would permit backwards in time communications as > well, since tachyons were fully subject to Special Relativity. This assumes that backwards in time communications are forbidden, but General Relativity seems replete with methods for producing closed paths in time, making and using them is just a small matter of engineering :) SignatureC:>WIN | Directable Mirror Arrays The computer obeys and wins. | A better way to focus the sun You lose and Bill collects. | licences available see | http://www.sohara.org/ >> > Anything with imaginary rest mass can (and must) travel faster than >> >the speed of light if the LF contractions hold good. Such particles used [quoted text clipped - 8 lines] >but General Relativity seems replete with methods for producing closed >paths in time, making and using them is just a small matter of engineering :) Makes me think that if two people talking to each other are falling into a black hole with one behind the other, FTL communications become allowed in one direction after at least one or maybe both of the two are past the point of no return? And any FTL communications between the two if one of the two are not past the point of no return only involve the one past the point of no return, and never FTL enough far enough to allow any possibility of the doomed astronaught to get an ancestor to change his fate ahead of time? - Don Klipstein (don@misty.com) > >> > Anything with imaginary rest mass can (and must) travel faster than > >> >the speed of light if the LF contractions hold good. Such particles used [quoted text clipped - 17 lines] > possibility of the doomed astronaught to get an ancestor to change his > fate ahead of time? There's a misconception here that a self consistent paradox free universe requires an absence of time travel or FTL communications. This has been shown not to be so - see "Cauchy Problem in Spacetimes with closed Timelike Curves" by Friedman, Morris, Novikov, Echeverria, Klinkhammer, Thorne and Yurtsever in Ohysical Review D42 (1990) 1915-1930. In short they show that the apparent paradox can always be avoided. SignatureC:>WIN | Directable Mirror Arrays The computer obeys and wins. | A better way to focus the sun You lose and Bill collects. | licences available see | http://www.sohara.org/ >In the group alt.folklore.computers: > [quoted text clipped - 8 lines] >>chart showed an interesting prediction: by 2015, gas turbine specific >>fuel consumption would cross into a negative number. Is this not proof that "the relevant sloped line" on the chart would make a major change in course well before the year at which such a straight line would predict gas turbine engines to be 100% efficient at converting heat-of-combustion to mechanical energy? I surely think that efficiency of gas turbine engines has done some "leveling off" in recent years to an extent good for an adjustment of a chart that extrapolates to a prediction of gas turbine engines to have efficiency crossing from infinity to negative-infinity in 2015! When did this chart predict 100% efficiency? (as opposed to infinity efficiency?) If this is projected to occur later than 2005, who claims that we have to wait until then to invalidate "straight-lining" (my words) that I believe was used in this chart? When did this chart predict the rather tall order of 50% efficiency? If that was for before 2005, has this been achieved yet in an any economically practical engine? - Don Klipstein (don@misty.com) > I surely think that efficiency of gas turbine engines has done some > "leveling off" in recent years to an extent good for an adjustment of a > chart that extrapolates to a prediction of gas turbine engines to have > efficiency crossing from infinity to negative-infinity in 2015! The cores probbably. What makes today's jetliner engines so efficient is the ever increasing bypass ratios. This doesn't apply to a turboshaft, of course. > When did this chart predict 100% efficiency? (as opposed to infinity > efficiency?) If this is projected to occur later than 2005, who claims > that we have to wait until then to invalidate "straight-lining" (my words) > that I believe was used in this chart? I'll see if I can dig it up. I'm guessing there's a theoretical limit that can be predicted, but it certainly isn't 100%. > When did this chart predict the rather tall order of 50% efficiency? > If that was for before 2005, has this been achieved yet in an any > economically practical engine? 50% has been achived in HUGE marine diesels, but it's a fuction of turning so slow - 200 rpm, which gives the thing darn near forever to get a lot of energy out of each boom. I think some smaller diesels can hit near 40%, but it's harder as size goes down. Ahhh, here we go: http://web.archive.org/web/20040210111547/www.railpower.com/efficiency.ph p I was somewhat off on my dates predicted, but, hey, they STILL show it as being a linear drop, though the data points don't match up well :) But, still. They're showing it as a straight line. Keep running it along and hey, isn't that a neat trick? The best I can figure, rail diesels slowly got better at a somewhat linear pace, gas turbines jumped a few times but have leveled off in recent years. It's interesting to note that a rebuild of 70's vintage gas turbine powered trains in NY recently was a disaster - the units were still unreliable, and still sucked fuel. Actually, they just plain sucked, but that's another story... As of late, Railpower's been backing off on their turbine plans (no more dreamy charts!). I suspect their Green Goat might get a niche as a yard switcher, but mainline uses for hybrid locomotives in general are probbably limited at best. They sure have been good at buzzword compliance, at least. In the US market, they might have a niches they can carve out and live in. Worldwide, I suspect Bombardier, etc would crush them in an instant. [snip engine efficiency] >> When did this chart predict the rather tall order of 50% efficiency? >> If that was for before 2005, has this been achieved yet in an any [quoted text clipped - 4 lines] >get a lot of energy out of each boom. I think some smaller diesels can >hit near 40%, but it's harder as size goes down. 200 rpm isn't slow regarding large ships. "Give her all she got, you may even take her to 200 rpm" -- line from the movie about the breakout from Dakar. >Ahhh, here we go: > >http://web.archive.org/web/20040210111547/www.railpower.com/efficiency.php >I was somewhat off on my dates predicted, but, hey, they STILL show it >as being a linear drop, though the data points don't match up well :) [quoted text clipped - 18 lines] >can carve out and live in. Worldwide, I suspect Bombardier, etc would >crush them in an instant. That is turbine-electric, right ? Diesel-electric has been pretty standard issue in locomotives for at least 4 decades now. -- mrr > 200 rpm isn't slow regarding large ships. I should have said 'max' in there. Sorry.. > That is turbine-electric, right ? Diesel-electric has been pretty > standard issue in locomotives for at least 4 decades now. Yeah. Bombardier tried their hand at selling turbine electric in the US, at the nagging of the US DOT. Once AGAIN, it was a commercial failure. The idea was to get 'electric train performance' without the supposedly 'expensive' electrification. Once again, it was a total failure - the prototype is rotting up in a yard in Canada somewhere. Closest to a sale was Florida, where they proposed it Vs an electric system for high speed rail. So much for big savings - the turbine trains were more expensive, slower, and the system cost was barely cheaper, despite heavy single tracking in BBD's design proposal. FL went BBD, demanded all electric, then came to its senses and realized the state has no real use for high speed rail becaue it has no useable local transit to support it, nor any real city centers. The system would have been a very expensive shuttle between Orlando airport and disneyworld. Whoopie. Diesel electric's well established, though diesel hydrualic is and was common in Europe for decades and had some noteably uses in the US (RDC, etc) IMHO, DH hasn't gotten big use in the US only because of Electro-Motive's big success early on. There's little question it works, and in some applications beats DE anyway. I suspect the US DOT will STILL keep trying at the gas turbine train idea, but it's so far been proven to be unworkable - the TGV was origionally going to be gas turbine - only after the prototypes got rolling did they decide to go electric. Pretty much everyone's tried it and it's been a failure - turboshafts aren't very reliable sucking in dust and being shaken like crazy all day, fuel consumption is STILL higher than a diesel, and maintenance is a scary thing to think about - lots of rail maintenance is hammer based. Gas turbines have a nasty habit of exploding and shedding parts when you abuse them... More realistically, the US DOT should step back, look at how they're pretty much the sole party persuing gas turbine powered trains (Railpower's vaporware GT loco not withstanding), and then look at what's worked overseas and adopt that. But you're talking about an agency/industry that has rasied NIH from an acronym to an art form... > I suspect the US DOT will STILL keep trying at the gas turbine train > idea, but it's so far been proven to be unworkable - the TGV was [quoted text clipped - 5 lines] > lots of rail maintenance is hammer based. Gas turbines have a nasty > habit of exploding and shedding parts when you abuse them... But turbines are so _sexy_... Signature/~\ cgibbs@kltpzyxm.invalid (Charlie Gibbs) \ / I'm really at ac.dekanfrus if you read it the right way. X Top-posted messages will probably be ignored. See RFC1855. / \ HTML will DEFINITELY be ignored. Join the ASCII ribbon campaign! For those who haven't seen any information on these engines, here's a link to one of those behemoths: http://www.bath.ac.uk/~ccsshb/12cyl/ I don't know if this is a duplicate of the below link, since it comes up here as a "naughty boy; this is a restricted web-site". Joe > 50% has been achived in HUGE marine diesels, but it's a fuction of > turning so slow - 200 rpm, which gives the thing darn near forever to [quoted text clipped - 5 lines] > http://web.archive.org/web/20040210111547/www.railpower.com/efficiency.ph > p |
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