mocking windows because it is vulnerable to users running insecure software in administrator mode when every other OS has the exact same vulnerability.
Well, yeah, but (1) Windows seems to have so much more insecure software than other OS's, and (2) a lot of that software is so eager to run yet more insecure software just to be "helpful" to the user (eg Word and Excel macros, email attachments, fun stuff in webpages, etc.)
Having Vista default to user mode is a good thing -- it's nice to see Microsoft finally catching up on several decades of software best practise.
What's that? Oh, widespread doesn't necessarily mean popular. Windows is installed by default with most hardware, Linux users have made a choice. Most people in the US die of heart disease, but that doesn't make it the most popular form of death.
Microsoft argued (successfully) that IE is an integral part of Windows
What part of losing the case do you consider successful? I suppose "successful" in the sense that they managed to avoid being slapped with perjury charges for faking the video that showed Windows running "worse" after IE was removed. Or successful in the sense that the penalties were reduced to the equivalent of a slap on the wrist.
The 8088 (the term "X86" was coined much, much later)
Yes, the IBM PC was 8088, but that was just Intel's 8-bit bus version of its existant 8086 processor. Either way, IBM started the x86 line of PCs.
didn't have any privilege levels so it's not possible (even today) to run a stable and secure Unix OS on it
True but irrelevant. It's not possible to run any kind of stable and secure OS on it, but it is possible to run a system that's a Unix "lookalike" system in that it has the same user tools, shell, etc. Indeed, IBM itself sold PC/IX, a Unix clone for the PC.
In addition because of the 8088's 64K memory segmentation, it's much more difficult to write a large program for it.
True but also irrelevant. "More difficult" != "impossible", and Unix grew up on 16-bit processors with an inherent 64K address limitation. (I ran a Unix system for a couple of years on a PDP-11/20 with 128K RAM and 10MB disk.)
That's not to say that you couldn't write a Unix-like OS for it, but the security and stablity of such an OS would be far less than Windows NT/2000/XP.
I'd like to see you try to run any of Windows NT/200/XP on an 8088-based IBM PC!
In this respect he is like Bill Gates, with people saying how if it hadn't been for Microsoft we'd still be using DOS.
Alas, the truth of it is that it hadn't been for Microsoft, we'd probably have been using something Unix-like a lot sooner. (Although arguably Digital Research could have ended up doing the same thing that MSFT did. Both DR-DOS and MS-DOS (nee QDOS) were natural successors to the 8-bit CP/M.)
The fact is that in the timeframe that IBM introduced the x86-based PC, there were many other platforms, from M68K-based (and other 16 and 32 bit chip) systems running real AT&T Unix derivatives, to high-end 8-bit 6809 systems running the Unix-like OS-9, and even a couple of Unix derivatives or workalikes for IBM's own PC. (Even Microsoft was in that game then, with Xenix.)
Hear hear. While I love the GNU utilities (mostly), the basic set -- especially going back a few years -- amounts to what any C programmer with some knowledge of Unix data structures could crank out in short order. Even before "The GNU Manifesto", Kernighan & Plauger's "Software Tools" (1976) showed how to build up a small suite of Unix-like utilities for almost any reasonable OS, and the Berkeley stuff started coming out not long after that.
Yes, there are some GNU tools that are rather harder to duplicate (the already mentioned GCC, stuff like lex and yacc (er, flex and bison), etc), but the coreutils have been independently reimplemented many times, and even "Software Tools" covered the rudiments of writing compilers and parser generators.
In case some disaster destroyed my town i'd be more concerned at staying warm than about my meat going off.
Your town is obviously somewhere poleward of the snowbelt, then. Places closer to the equator have the opposite problem. Take New Orleans, for example -- they certainly weren't worried about staying warm. Given the geometry of a sphere and the current average temperature, there's more land, and certainly people, in the warmer areas than the cooler.
Besides, heat is easy. Just start breaking up the furniture and burning it.
It's customary that when you put quotes around some text in a reply, that the quoted string actually appears somewhere in the post that you're replying to. Where in the world (or at least, the parent post) do you find the string "Fision [sic] does not take place"?
However, just to refresh your high school physics, radioactive decay is not fission, neither is it a "reaction". To have a reactor, you need a reaction. In an RTG, you just need something radioactive enough to be warm. The heat comes from the kinetic energy of the decay products, which got their energy from the act of decaying (exact method depends on decay type).
It turns out that 9 of the 12 people who have walked on the Moon (namely, Armstrong, Conrad, Bean, Shepard, Mitchell, Irwin, Young, Duke and Cernan) were or had been in the navy or at least graduated from a naval academy.
Now, I don't know if naval aviators consider themselves "sailors", but at least two of the above (Shepard and Young) also served aboard destroyers.
Heinlein always said that it made more sense for the navy, rather than the airforce, to be involved in a space program.
No, the Apollo program didn't use reactors. The SNAP series covered both RTGs (radioisotope thermoelectric generators) and actual fission reactors -- odd numbered models were RTG, even numbered were reactors.
The nuclear power sources on Apollo were SNAP-27s -- RTGs. (These used Pu238, the weapons stuff is Pu239.) Note that these were only used to power the scientific instrument packages (ALSEP) deployed on the surface. The LEM itself used batteries, as did the Command Module itself. The CM was supplied with power from the Service Module while attached to it (ie, until just before reentry), and that was produced by oxy-hydrogen fuel cells.
Don't know about now, but the when the ALSEP experiment packages were turned off by command from NASA (late 1977), the RTGs were still pumping out power. (The budget to collect the data ran out.) Since the half-life of Pu238 is about 90 years, it should still be putting out about 60-something % power. Of course, there's no way to turn the experiments back on again without sending somebody up there to do it manually. (When bureaucrats make a decision to end something, they want to make sure it's really hard to second guess them.)
The only reactor-based SNAP to ever fly in space was a SNAP-10A powering an ion propulsion test.
The Soviets routinely used nuclear reactors to power some of their spy satellites, ejecting the core into a high disposal orbit at end of life. Well, except for Cosmos 954, a radar satellite, which re-entered over Canada in 1978 without ejecting the core. It littered radioactive debris over a large chunk of the Northwest Territories. (Google "operation morning light" for info on the cleanup operation.)
In the 1960s it was a space race, the goal was to get high (so to speak) because it gave military superiority.
Not entirely. The military aspect could be achieved with orbital stations and unmanned satellites, and by the mid to late 1960s the USAF was shutting down its space projects (eg DynaSoar, MOL) entirely in favor of unmanned satellites and better missile technology.
The race to the Moon (vs a more generic "space race") was chosen specifically because it was the one target that the experts at the time thought the US had a real chance of beating the USSR at. The Soviets were already ahead as far as simple manned operations in Earth orbit, and the consensus was that the USSR had enough of a head start that trying for a goal like "first orbital space station" or even "first manned trip around the Moon" wouldn't guarantee a win, but "first manned Moon landing (and return)" was just do-able. At the time, Russia didn't even have plans for a heavy-lift vehicle comparable to the Saturn, which NASA had been working on for a couple of years.
Which pretty much turned out to be the case. Throughout the 60s, USSR racked up first after first -- first person in orbit, first woman in orbit, first multi-person crew in orbit, first spacewalk, first orbital rendezvous (for a loose definition of rendevous - the Gemini 6 & 7 mission was first by a more rigorous definition), and so on. If their senior rocket designer Sergei Korolev (their Wernher Von Braun equivalent) hadn't died in 1966 (from botched minor surgery), it's arguable that the problems with their N1 (Saturn V equivalent) would have been fewer or resolved more quickly, the race would have been much closer than it was. (Apollo had problems of its own too -- the Apollo 204 (Apollo 1) fire, pogo and other problems with Saturn V, schedule delays with the LEM -- of course.)
True, in a global reference frame, the rebounding object will pick up KE if it hits something moving toward it (like said bat). I was assuming a fixed target.
the very simple and specific question of whether a bullet which sticks or a bullet which bounces imparts more energy. Notwithstanding all of the fine points that you make, the fact remains that a bullet which bounces back (as in, the sign of the momentum changes) does impart more energy to the target than one which sticks, other factors being equal.
Um, no. The bouncing bullet still has KE of 1/2 m * v^2, where v is lower and sign-reversed from before it hit, but non-zero. If it hits and sticks, v is now zero (reference frame of the target) and the KE of the bullet is thus zero. Thus the bullet loses more energy if it sticks than if it bounces. Now that's not all imparted to the target (sound, heat, deformation etc), but most of it is.
OTOH, a bounce imparts more momentum to the target than if it stuck. (Momentum (m * v) is a signed quantity, but KE isn't (squaring the velocity means it's always positive whatever the sign of v).)
Of course in the real world, without body armor (or soft bullets), the bullet won't bounce or stick, but just keep on going. I vaguely recall a quote from an encyclopaedia article, talking about the Luger and its 9mm jacketed ammunition, which "had a disappointing tendency to completely penetrate the target and expend most of its energy on the surrounding landscape".
Tumble clean sand with smooth rocks higher on the Mohs scale.
Okay, sand is quarz (hardness 7). Higher on the scale would be topaz (8), corundum (sapphire - hardness 9) or diamond (10).
Could be expensive.
(Ok, joke. Industrial corundum or carborundum would work -- except that some of that would inevitably get ground down too and you'd have to separate out the nano-silica from the nano-alumina.)
John Brunner used a similar idea, earlier, in "Shockwave Rider" (if I'm remembering correctly -- it might have been the even earlier "Stand on Zanzibar" or "The Jagged Orbit"). He introduced the "karatand" (karate hand), gloves made of the stuff that are flexible in normal use but stiffen on impact. Of course Brunner's use was offensive rather than defensive.
I think it was also Brunner in one of the above novels that introduced the "geckopad", which is also just now becoming reality.
Kevlar alone just has very high tensile and shear strength. It will resist cutting (which is why kevlar gloves are often used by butchers or fishermen cleaning their catch). It's the particular weave of the kevlar in vests that makes them bullet resistant. (Earlier vests were made of nylon, but that's much bulkier for equivalent stopping power.)
As an ancestor post pointed out, the kevlar just slows down the incoming bullet. For a rifle bullet at 2000-3000 fps, it slows it down enough for the ceramic plate to stop it. For a pistol bullet -- the type most likely to be encountered by police -- at 900-1000 fps, it slows it down enough to stop it.
Don't confuse kinetic energy with momentum. Momentum is always conserved, KE isn't. KE gets converted to heat, sound, energy to deform the bullet, etc.
If a bullet (or anything else) picked up KE by bouncing, that'd be pretty amazing. You could create something that bounces higher than the height from which it was dropped, for example.
Even the momentum isn't a big deal, if it's distributed over the mass of the vest. Consider that the shooter receives exactly the same momentum (with the opposite sign) as is imparted to the bullet when it fires. (Well, no big deal compared to being hit by the bullet directly. I wouldn't want to fire a rifle with the butt held against anything tender.)
Check his biography? I've done better than that, I've read his work. I've also met him.
Even in his field of planetary astronomy he made some really bonehead, possibly politically motivated, extrapolations from the observed data. (Most notably extrapolating the global dust storms on Mars to a "nuclear winter" scenario on Earth -- ignoring the differences in diameter of the two planets (Mars is small enough to have a single convection cell run from equator to pole, Earth has three), and the effects of oceans (which Mars doesn't have) on atmospheric circulation and precipitation.)
As for what I said - "Sagan [...] was a better popularizer of science than he was a scientist", I don't think you'd find many who were really familiar with his work who would disagree with that. I'd say the same about Isaac Asimov (who was a PhD biochemist).
The problem arises when (if) the phenomenon observed depends on some aspect of the methods and materials which is not documented, possibly because the experimenter himself is unaware of its importance. The purity of germanium in the semiconductor experiments I alluded to in an earlier post, for example.
This is particularly true when an experimenter with much experience in one field reports observations in another field. The methods/materials section of a paper is going to leave out that which the author assumes that "anyone knowledgeable in the field" will know, to save space. An expert in a different field, however, may well have different experience as to what is and isn't significant, and make incorrect assumptions when trying to replicate the experiment.
Apparently the preparation of the palladium rod (purity, annealing, etc) in the P&F experiments has a big influence on whether one gets excess heat. If the nanostructure of the Pd/Du matrix played a significant role in the phenomenon (as the nanostructure of semiconductors does in getting them to do anything useful), it could well explain the variable success rate. (I'm not saying it does.I'm aware of the scale differences between electronic phenomena and nuclear phenomena -- but who knows, maybe the right Pd crystal lattice makes a whole bunch of tiny Farnsworth fusors, or provides little areas for Bose-Einstein condensates of deuterons to collect, or whatever. It just has to be the right lattice, with just the right impurities.)
many experiments, including their own, failed to yield the expected results. These were irrelevant, they argued, incompetently done, or lacking some crucial (perhaps unknown) ingredient needed to make the thing work. Instead, all positive results, the appearance of excess heat, or a few neutrons, proved the phenomenon was real.
Most proponents weren't -- and aren't -- quite that extreme. They argue that excess heat, neutrons, helium, etc prove that some phenomenon not explainable by conventional nuclear physics was taking place. There's a lot of disagreement as to exactly what is taking place. The opponents, on the other hand, said "there's nothing happening, the observed head/neutrons/helium are a mistake, we can't hear you la la la..." (Okay, I exaggerate that last bit.)
That the experiments are hard to replicate (but apparently not impossible, since they seem to have been replicated by other observers) suggests that not all the conditions affecting the phenomenon -- whether it is a real physical phenomenon or some unobvious source of experimental error -- are well understood. This is to be expected if it really is something new -- because if it were easy somebody would have already noticed it. Look at the pre-1947 history of semiconductors and transistors, for example -- there was something going on but it wasn't until they could make high-purity germanium crystals that they could reliably duplicate it.
On the other hand, look at the history of polywater.
It makes more sense to me than babies hearing that noise in the womb. Can you remember what it was like in your mothers womb?
Remember? No, but then my brain is considerably different and has undergone substantial rewiring since then. As is true with all kids as they get to be a couple of years old.
Shhh to calm a baby? I do agree with. Any soothing sound.
And "any soothing sound" can include the vacuum cleaner or the clothes drier -- which both make white noisy "ssh" sounds. For my kids we had a teddy bear with an electronic sound device inside which simulated womb sounds (sshh plus heartbeat) -- worked pretty well.
I've never heard a snake hiss, even one that was alarmed and scared enough to bite me. (Harmless bite, just a (largish) garter snake that some other kids had been teasing.)
Actually stereo vision is essential to almost any predator, that's one easy way to destinguish a predator species from a prey species -- do both eyes look forward for stereo vision, or sideways for maximum peripheral vision? It's also particularly useful for arboreal species -- you really need to know if that branch you're about to jump to is within reach or not.
In fact, that's the real reason we arboreal primate descendents fear snakes -- it's not predator fear, but when you're swinging from branch to branch and that vine you grab for turns out to be a snake...whoops!
Another interesting bit from the book: In every single culture in the world, the sounds "ssssssss" or "sssshhhhhhhhhh" mean "Everybody Shut Up!", as in, "Quiet! Snake!".
The "sshh" sound is also what mothers use to calm and quiet a crying baby. Interestingly, that's also the primary sound heard in the womb -- the noise of blood flowing through veins and arteries (overlaid by the thump of the heartbeat).
And snakes generally don't hiss.
Sagan had a lot of, um, interesting ideas, but he was a better popularizer of science than he was a scientist.
As science progresses, the set of all life which is "viable outside of the womb" is going to eventually be equal to the set of all "potential for becoming life".
Not likely, since a lot of that early stuff isn't even viable inside the womb. This is a point that "pro-life" folk tend to ignore. The fact is, most fertilized ova don't even properly implant in the womb, and of those that do many don't make it much past the first month, for purely natural reasons -- including cases where there was never an embryo per se at all (eg empty placenta).
The suits themselves are complicated little machines,
The NASA suits are (over-?) complicated machines. The Russian suits are much simpler in design. (Most studies I've seen of "next generation" suits borrow a lot from Russian design.) Certainly anyone capable of learning technical diving or commercial diving can learn to handle a space suit, and you're just as dead if something goes wrong in the former cases as the latter.
As for the "physically grueling" aspect, tourists are just going to be floating around sightseeing, not doing maintenance or construction work.
Slashdot Mirror
mocking windows because it is vulnerable to users running insecure software in administrator mode when every other OS has the exact same vulnerability.
Well, yeah, but (1) Windows seems to have so much more insecure software than other OS's, and (2) a lot of that software is so eager to run yet more insecure software just to be "helpful" to the user (eg Word and Excel macros, email attachments, fun stuff in webpages, etc.)
Having Vista default to user mode is a good thing -- it's nice to see Microsoft finally catching up on several decades of software best practise.
the most popular operating system in the world
But Linux has had that for a long time.
What's that? Oh, widespread doesn't necessarily mean popular. Windows is installed by default with most hardware, Linux users have made a choice. Most people in the US die of heart disease, but that doesn't make it the most popular form of death.
Microsoft argued (successfully) that IE is an integral part of Windows
What part of losing the case do you consider successful? I suppose "successful" in the sense that they managed to avoid being slapped with perjury charges for faking the video that showed Windows running "worse" after IE was removed. Or successful in the sense that the penalties were reduced to the equivalent of a slap on the wrist.
The 8088 (the term "X86" was coined much, much later)
Yes, the IBM PC was 8088, but that was just Intel's 8-bit bus version of its existant 8086 processor. Either way, IBM started the x86 line of PCs.
didn't have any privilege levels so it's not possible (even today) to run a stable and secure Unix OS on it
True but irrelevant. It's not possible to run any kind of stable and secure OS on it, but it is possible to run a system that's a Unix "lookalike" system in that it has the same user tools, shell, etc. Indeed, IBM itself sold PC/IX, a Unix clone for the PC.
In addition because of the 8088's 64K memory segmentation, it's much more difficult to write a large program for it.
True but also irrelevant. "More difficult" != "impossible", and Unix grew up on 16-bit processors with an inherent 64K address limitation. (I ran a Unix system for a couple of years on a PDP-11/20 with 128K RAM and 10MB disk.)
That's not to say that you couldn't write a Unix-like OS for it, but the security and stablity of such an OS would be far less than Windows NT/2000/XP.
I'd like to see you try to run any of Windows NT/200/XP on an 8088-based IBM PC!
In this respect he is like Bill Gates, with people saying how if it hadn't been for Microsoft we'd still be using DOS.
Alas, the truth of it is that it hadn't been for Microsoft, we'd probably have been using something Unix-like a lot sooner. (Although arguably Digital Research could have ended up doing the same thing that MSFT did. Both DR-DOS and MS-DOS (nee QDOS) were natural successors to the 8-bit CP/M.)
The fact is that in the timeframe that IBM introduced the x86-based PC, there were many other platforms, from M68K-based (and other 16 and 32 bit chip) systems running real AT&T Unix derivatives, to high-end 8-bit 6809 systems running the Unix-like OS-9, and even a couple of Unix derivatives or workalikes for IBM's own PC. (Even Microsoft was in that game then, with Xenix.)
Hear hear. While I love the GNU utilities (mostly), the basic set -- especially going back a few years -- amounts to what any C programmer with some knowledge of Unix data structures could crank out in short order. Even before "The GNU Manifesto", Kernighan & Plauger's "Software Tools" (1976) showed how to build up a small suite of Unix-like utilities for almost any reasonable OS, and the Berkeley stuff started coming out not long after that.
Yes, there are some GNU tools that are rather harder to duplicate (the already mentioned GCC, stuff like lex and yacc (er, flex and bison), etc), but the coreutils have been independently reimplemented many times, and even "Software Tools" covered the rudiments of writing compilers and parser generators.
In case some disaster destroyed my town i'd be more concerned at staying warm than about my meat going off.
Your town is obviously somewhere poleward of the snowbelt, then. Places closer to the equator have the opposite problem. Take New Orleans, for example -- they certainly weren't worried about staying warm. Given the geometry of a sphere and the current average temperature, there's more land, and certainly people, in the warmer areas than the cooler.
Besides, heat is easy. Just start breaking up the furniture and burning it.
It's customary that when you put quotes around some text in a reply, that the quoted string actually appears somewhere in the post that you're replying to. Where in the world (or at least, the parent post) do you find the string "Fision [sic] does not take place"?
However, just to refresh your high school physics, radioactive decay is not fission, neither is it a "reaction". To have a reactor, you need a reaction. In an RTG, you just need something radioactive enough to be warm. The heat comes from the kinetic energy of the decay products, which got their energy from the act of decaying (exact method depends on decay type).
It turns out that 9 of the 12 people who have walked on the Moon (namely, Armstrong, Conrad, Bean, Shepard, Mitchell, Irwin, Young, Duke and Cernan) were or had been in the navy or at least graduated from a naval academy.
Now, I don't know if naval aviators consider themselves "sailors", but at least two of the above (Shepard and Young) also served aboard destroyers.
Heinlein always said that it made more sense for the navy, rather than the airforce, to be involved in a space program.
No, the Apollo program didn't use reactors. The SNAP series covered both RTGs (radioisotope thermoelectric generators) and actual fission reactors -- odd numbered models were RTG, even numbered were reactors.
The nuclear power sources on Apollo were SNAP-27s -- RTGs. (These used Pu238, the weapons stuff is Pu239.) Note that these were only used to power the scientific instrument packages (ALSEP) deployed on the surface. The LEM itself used batteries, as did the Command Module itself. The CM was supplied with power from the Service Module while attached to it (ie, until just before reentry), and that was produced by oxy-hydrogen fuel cells.
Don't know about now, but the when the ALSEP experiment packages were turned off by command from NASA (late 1977), the RTGs were still pumping out power. (The budget to collect the data ran out.) Since the half-life of Pu238 is about 90 years, it should still be putting out about 60-something % power. Of course, there's no way to turn the experiments back on again without sending somebody up there to do it manually. (When bureaucrats make a decision to end something, they want to make sure it's really hard to second guess them.)
The only reactor-based SNAP to ever fly in space was a SNAP-10A powering an ion propulsion test.
The Soviets routinely used nuclear reactors to power some of their spy satellites, ejecting the core into a high disposal orbit at end of life. Well, except for Cosmos 954, a radar satellite, which re-entered over Canada in 1978 without ejecting the core. It littered radioactive debris over a large chunk of the Northwest Territories. (Google "operation morning light" for info on the cleanup operation.)
In the 1960s it was a space race, the goal was to get high (so to speak) because it gave military superiority.
Not entirely. The military aspect could be achieved with orbital stations and unmanned satellites, and by the mid to late 1960s the USAF was shutting down its space projects (eg DynaSoar, MOL) entirely in favor of unmanned satellites and better missile technology.
The race to the Moon (vs a more generic "space race") was chosen specifically because it was the one target that the experts at the time thought the US had a real chance of beating the USSR at. The Soviets were already ahead as far as simple manned operations in Earth orbit, and the consensus was that the USSR had enough of a head start that trying for a goal like "first orbital space station" or even "first manned trip around the Moon" wouldn't guarantee a win, but "first manned Moon landing (and return)" was just do-able. At the time, Russia didn't even have plans for a heavy-lift vehicle comparable to the Saturn, which NASA had been working on for a couple of years.
Which pretty much turned out to be the case. Throughout the 60s, USSR racked up first after first -- first person in orbit, first woman in orbit, first multi-person crew in orbit, first spacewalk, first orbital rendezvous (for a loose definition of rendevous - the Gemini 6 & 7 mission was first by a more rigorous definition), and so on. If their senior rocket designer Sergei Korolev (their Wernher Von Braun equivalent) hadn't died in 1966 (from botched minor surgery), it's arguable that the problems with their N1 (Saturn V equivalent) would have been fewer or resolved more quickly, the race would have been much closer than it was. (Apollo had problems of its own too -- the Apollo 204 (Apollo 1) fire, pogo and other problems with Saturn V, schedule delays with the LEM -- of course.)
True, in a global reference frame, the rebounding object will pick up KE if it hits something moving toward it (like said bat). I was assuming a fixed target.
the very simple and specific question of whether a bullet which sticks or a bullet which bounces imparts more energy. Notwithstanding all of the fine points that you make, the fact remains that a bullet which bounces back (as in, the sign of the momentum changes) does impart more energy to the target than one which sticks, other factors being equal.
Um, no. The bouncing bullet still has KE of 1/2 m * v^2, where v is lower and sign-reversed from before it hit, but non-zero. If it hits and sticks, v is now zero (reference frame of the target) and the KE of the bullet is thus zero. Thus the bullet loses more energy if it sticks than if it bounces. Now that's not all imparted to the target (sound, heat, deformation etc), but most of it is.
OTOH, a bounce imparts more momentum to the target than if it stuck. (Momentum (m * v) is a signed quantity, but KE isn't (squaring the velocity means it's always positive whatever the sign of v).)
Of course in the real world, without body armor (or soft bullets), the bullet won't bounce or stick, but just keep on going. I vaguely recall a quote from an encyclopaedia article, talking about the Luger and its 9mm jacketed ammunition, which "had a disappointing tendency to completely penetrate the target and expend most of its energy on the surrounding landscape".
Tumble clean sand with smooth rocks higher on the Mohs scale.
Okay, sand is quarz (hardness 7). Higher on the scale would be topaz (8), corundum (sapphire - hardness 9) or diamond (10).
Could be expensive.
(Ok, joke. Industrial corundum or carborundum would work -- except that some of that would inevitably get ground down too and you'd have to separate out the nano-silica from the nano-alumina.)
John Brunner used a similar idea, earlier, in "Shockwave Rider" (if I'm remembering correctly -- it might have been the even earlier "Stand on Zanzibar" or "The Jagged Orbit"). He introduced the "karatand" (karate hand), gloves made of the stuff that are flexible in normal use but stiffen on impact. Of course Brunner's use was offensive rather than defensive.
I think it was also Brunner in one of the above novels that introduced the "geckopad", which is also just now becoming reality.
Kevlar alone just has very high tensile and shear strength. It will resist cutting (which is why kevlar gloves are often used by butchers or fishermen cleaning their catch). It's the particular weave of the kevlar in vests that makes them bullet resistant. (Earlier vests were made of nylon, but that's much bulkier for equivalent stopping power.)
As an ancestor post pointed out, the kevlar just slows down the incoming bullet. For a rifle bullet at 2000-3000 fps, it slows it down enough for the ceramic plate to stop it. For a pistol bullet -- the type most likely to be encountered by police -- at 900-1000 fps, it slows it down enough to stop it.
Don't confuse kinetic energy with momentum. Momentum is always conserved, KE isn't. KE gets converted to heat, sound, energy to deform the bullet, etc.
If a bullet (or anything else) picked up KE by bouncing, that'd be pretty amazing. You could create something that bounces higher than the height from which it was dropped, for example.
Even the momentum isn't a big deal, if it's distributed over the mass of the vest. Consider that the shooter receives exactly the same momentum (with the opposite sign) as is imparted to the bullet when it fires. (Well, no big deal compared to being hit by the bullet directly. I wouldn't want to fire a rifle with the butt held against anything tender.)
Either that or they've got a serious "foothold" situation.
Check his biography? I've done better than that, I've read his work. I've also met him.
Even in his field of planetary astronomy he made some really bonehead, possibly politically motivated, extrapolations from the observed data. (Most notably extrapolating the global dust storms on Mars to a "nuclear winter" scenario on Earth -- ignoring the differences in diameter of the two planets (Mars is small enough to have a single convection cell run from equator to pole, Earth has three), and the effects of oceans (which Mars doesn't have) on atmospheric circulation and precipitation.)
As for what I said - "Sagan [...] was a better popularizer of science than he was a scientist", I don't think you'd find many who were really familiar with his work who would disagree with that. I'd say the same about Isaac Asimov (who was a PhD biochemist).
The problem arises when (if) the phenomenon observed depends on some aspect of the methods and materials which is not documented, possibly because the experimenter himself is unaware of its importance. The purity of germanium in the semiconductor experiments I alluded to in an earlier post, for example.
This is particularly true when an experimenter with much experience in one field reports observations in another field. The methods/materials section of a paper is going to leave out that which the author assumes that "anyone knowledgeable in the field" will know, to save space. An expert in a different field, however, may well have different experience as to what is and isn't significant, and make incorrect assumptions when trying to replicate the experiment.
Apparently the preparation of the palladium rod (purity, annealing, etc) in the P&F experiments has a big influence on whether one gets excess heat. If the nanostructure of the Pd/Du matrix played a significant role in the phenomenon (as the nanostructure of semiconductors does in getting them to do anything useful), it could well explain the variable success rate. (I'm not saying it does.I'm aware of the scale differences between electronic phenomena and nuclear phenomena -- but who knows, maybe the right Pd crystal lattice makes a whole bunch of tiny Farnsworth fusors, or provides little areas for Bose-Einstein condensates of deuterons to collect, or whatever. It just has to be the right lattice, with just the right impurities.)
many experiments, including their own, failed to yield the expected results. These were irrelevant, they argued, incompetently done, or lacking some crucial (perhaps unknown) ingredient needed to make the thing work. Instead, all positive results, the appearance of excess heat, or a few neutrons, proved the phenomenon was real.
Most proponents weren't -- and aren't -- quite that extreme. They argue that excess heat, neutrons, helium, etc prove that some phenomenon not explainable by conventional nuclear physics was taking place. There's a lot of disagreement as to exactly what is taking place. The opponents, on the other hand, said "there's nothing happening, the observed head/neutrons/helium are a mistake, we can't hear you la la la..." (Okay, I exaggerate that last bit.)
That the experiments are hard to replicate (but apparently not impossible, since they seem to have been replicated by other observers) suggests that not all the conditions affecting the phenomenon -- whether it is a real physical phenomenon or some unobvious source of experimental error -- are well understood. This is to be expected if it really is something new -- because if it were easy somebody would have already noticed it. Look at the pre-1947 history of semiconductors and transistors, for example -- there was something going on but it wasn't until they could make high-purity germanium crystals that they could reliably duplicate it.
On the other hand, look at the history of polywater.
It makes more sense to me than babies hearing that noise in the womb. Can you remember what it was like in your mothers womb?
Remember? No, but then my brain is considerably different and has undergone substantial rewiring since then. As is true with all kids as they get to be a couple of years old.
Shhh to calm a baby? I do agree with. Any soothing sound.
And "any soothing sound" can include the vacuum cleaner or the clothes drier -- which both make white noisy "ssh" sounds. For my kids we had a teddy bear with an electronic sound device inside which simulated womb sounds (sshh plus heartbeat) -- worked pretty well.
I've never heard a snake hiss, even one that was alarmed and scared enough to bite me. (Harmless bite, just a (largish) garter snake that some other kids had been teasing.)
Actually stereo vision is essential to almost any predator, that's one easy way to destinguish a predator species from a prey species -- do both eyes look forward for stereo vision, or sideways for maximum peripheral vision? It's also particularly useful for arboreal species -- you really need to know if that branch you're about to jump to is within reach or not.
In fact, that's the real reason we arboreal primate descendents fear snakes -- it's not predator fear, but when you're swinging from branch to branch and that vine you grab for turns out to be a snake...whoops!
Another interesting bit from the book: In every single culture in the world, the sounds "ssssssss" or "sssshhhhhhhhhh" mean "Everybody Shut Up!", as in, "Quiet! Snake!".
The "sshh" sound is also what mothers use to calm and quiet a crying baby. Interestingly, that's also the primary sound heard in the womb -- the noise of blood flowing through veins and arteries (overlaid by the thump of the heartbeat).
And snakes generally don't hiss.
Sagan had a lot of, um, interesting ideas, but he was a better popularizer of science than he was a scientist.
As science progresses, the set of all life which is "viable outside of the womb" is going to eventually be equal to the set of all "potential for becoming life".
Not likely, since a lot of that early stuff isn't even viable inside the womb. This is a point that "pro-life" folk tend to ignore. The fact is, most fertilized ova don't even properly implant in the womb, and of those that do many don't make it much past the first month, for purely natural reasons -- including cases where there was never an embryo per se at all (eg empty placenta).
The suits themselves are complicated little machines,
The NASA suits are (over-?) complicated machines. The Russian suits are much simpler in design. (Most studies I've seen of "next generation" suits borrow a lot from Russian design.) Certainly anyone capable of learning technical diving or commercial diving can learn to handle a space suit, and you're just as dead if something goes wrong in the former cases as the latter.
As for the "physically grueling" aspect, tourists are just going to be floating around sightseeing, not doing maintenance or construction work.