The simplified freshman chem explanation is that as you go across, the amount of shielding electrons is the same, but nuclear charge goes up, and as such, Z-effective increases. This mostly seems to counteract increased electron-electron repulsion, with things like the lanthanide contraction aside.
I'm afraid that, while interesting, this doesn't address my question, which concerned the alkali metals only (as they are presumably the most easily analyzed). I'm just going down a column, not across a row, and finding radii smaller than a naieve model would preduct.
And yes, you are correct: the shielding cannot be perfect. If it were so, the electrons would simply be repelled by one another and not hang out anywhere near the nucleus together anymore.
They still would, as the total charge of the core shells is less than the magnitude of the charge of the nucleus. Even if perfectly spherically distributed and completely inside the valence shell, they'd only cancel as many protons as there are electrons in the non-valence shells.
The (conjectured) reason shielding isn't even this good that a friend and I thougt about was that the second assumption doesn't hold (that the wavefunctions of the inner shells extend past the valence shell, causing some of their charge to not contribute to shielding).
The first assumption should hold, if I understand correctly (the charge distribution of a filled shell has spherical symmetry in the absence of external influences). OTOH, maybe the shells could induce dipoles in each other as with London forces between atoms... Bleah.
Dragging this back to my original question - is there a known, closed-form solution to the radial distribution function for the electrons in alkali metals (or even noble gases), or even a good approximate solution, or am I stuck trying to solve the Schrodinger equation the hard way?
The one where they steal a car from an amusement park ride, and the computer create a force field around it? Damn it, my day is ruined now. I can't remember the title.
The big thing about the force fields was that they cancelled _inertia_, allowing near-instant acceleration/decelleration without pasting the occupants. This is mentioned briefly by the "nerd" character near the beginning of the film.
Actually, they are all rougly the same size, regardless of atomic weight. This is one of the interesting things about quantum mechanics and atomic physics. *All* atoms are between 0.5 and 2.5 Angstroms (1e-10 m)with Cesium being the largest (bigger than Uranium) and Nitrogen? being the smallest. Silicon isn't very large, however.
Hydrogen's the smallest, according to my books, with a radius of something like 0.53 angstroms (been a while since I looked it up).
What confuses me is why the atomic radii don't go up as the square of the number of shells. The alkali metals will have a single electron in the outermost shell, with the nucleus shielded by the inner shells, and so having an apparent charge of one. This seems to give a system with size equivalent to the nth energy level of an electron in hydrogen, which goes up as the square of the shell number.
I and the friends I asked about this speculate that because the electrons in the sheilding shells are smeared out radially, the outermost shielding shell extends past the valence shell's nominal radius, and so the core is only partly shielded, but I haven't seen any description to date of how you work out what the radii actually end up being.
pay close attention: english is a living language. If enough people think that the correct plural spelling of virus would be potatoe, then potatoe it is!
Clippy:Is this the same principle of common usage that keeps sending us all the spelling mistakes, and thinks it's ok to stick an apostrophe into any word ending in 's' no matter whether it's a contraction or a plural?
Clippy:Because if so, it can bite my skinny wire ass!
It's called electrolysis. You separate salt water into
Hydrogen a highly-reactive gas, thus antibiotic.
Oxygen, an oxidizer (duh), oxidation is about the most commonly used method of disinfection.
Sodium, a highly reactive chemical and thus disinfectant.
Chlorine, a superoxidizer (see above).
Actually, you just get the most easily reduced/oxidized species coming out. This means chlorine and hydrogen. The water stays water, and the sodium displaces the removed hydrogen to form sodium hydroxide. So, your saltwater turns into oven cleaner, which is not safe to drink, and you get chlorine gas bubbling off, which works quite well as a disinfectant (and is already used).
I wouldn't worry about the hydrogen. It's not terribly reactive, contrary to what you appear to have heard. It does burn, but you won't have enough present to worry about.
If they're using this for disinfecting, what's probably happening is that they're producing sodium chlorate. This can be formed instead of chlorine gas if your electrodes are close enough together that the ion species can mix. Sodium chlorate is a strong oxidizing agent; in weak solutions, it should be a decent disinfectant. I *really* wouldn't drink it, though (it's poisonous in significant amounts).
Contrary to what the article says, I seriously doubt you could mist a letter with chlorate-rich water and have it stay dry while being disinfected. You'd also have the nasty side effect of the letter becoming quite flammable when the mist dried, if you sprayed any substantial amount of solution on it (powerful oxidizer, remember; unstable enough that it can even explode on its own if provoked enough).
Alternatively, they could just be doing standard electrolysis and burning the hydrogen and chlorine together to get hydrogen chloride. On contact with water (or bacteria) it'll turn into hydrochloric acid, and so would be quite poisonous.
Or they could be arcing through the air using the water as an electrode, to produce ozone or nitric acid vapour. The salt wouldn't be doing much in this scenario (except making the water conduct).
In summary, the possible reaction paths are a bit more complicated than you're painting, though I agree that the article's claims are at the very least exaggerated.
Aren't we talking about almost negligible gravitational forces from the asteroid itself? If escape velocity from the asteroid itself were an issue, I'd think we were screwed no matter what at that point, that thing would be really huge.:)
The escape velocity from asteroids is small (though non-negligeable). However, you're trying to impart it to a billion tonnes of rock. This makes the energy required significant.
Still quite do-able. My back-of-the-envelope numbers say the equivalent of a few kT is required (plus whatever is needed to actually shatter the rock, times whatever inefficiency factor you assume for force transmission).
everything comes back you know. nuking a asteroid heading towards earth is bound to have debris falling our way, and radioactive ones too.
It's far better to have 1% of the asteroid's debris cone hitting Earth than having the whole thing come raining down on us.
The environmental impact of any residual radioactivity from the nuke used to fragment it is far, far less than the environmental impact of the original strike (in the absence of interference), and probably even of the few chunks that still hit Earth.
Why not just shatter the asteroid? Seems like that would take less energy than either your or his sugesstion. Let the atmosphere do the work, just break it up is chunks that are small enough to ablate down to non-threatning pieces.
The problem is that most asteroids large enough to be a problem would cause serious problems even raining down into the atmosphere as gravel. Large volcanic eruptions mess up our climate quite nicely; vapourizing a few billion tonnes of rock on re-entry would have much the same effect.
What you really have to do is fragment the asteroid with enough force that the pieces all have local escape velocity [from the asteroid], and do it far enough back in its orbit that most of the pieces miss Earth [the hard part, as we'd need months to years of advance notice].
This is still probably the most practical way of dealing with an Earth-threatening asteroid.
What we really need to do is figure out how to take some of the mass of the asteroid and accelerate it, using this as the reactant to change the path. Sort of like installing a rail gun on the asteroid, and firing off bits of asteriod like b-b's to get the asteroid to move in the opposite direction.
Or haul a bigarsed ion drive over to it, and use charged silica vapour as the reaction mass. Bring spare ionization screens...
I can understand using certification as a business model and to help develop a stable of knowledgable consultants for projects. But having a per year fee on top of the certification seems like you're paying for them to help market you.
That depends. You could make a good argument for mandatory recertification to make sure people haven't just forgotten everything they crammed for the exam, and to keep them up to date with improvements. Making certification expire yearly accomplishes this.
Personally I think having to pay on top of the certification starts to be a bit much. If I pay the 5K and don't get any work out of it, what have they really done for me?
They've given you permission to use their label when looking for work, which presumably greatly increases your chances of finding it. If you still can't find any, that doesn't invalidate what they gave you.
I'm not arguing that JBoss certification is *worth* $5K - that's a value decision each buyer has to make for themselves. I'm just pointing out that there is a justification for what they're doing, even if you disagree with the price point.
I'm on the fence, but at the rate I've actually done anything to build my next system (hey, I did buy a cabinet!:-) the wait for the Hammer shouldn't be much longer (why does this name summon the memory of the artwork inside PF:The Wall, hmm, something there, but what...)
I'm waiting too, but that's because I don't think I'll have to upgrade for at least a year.
Remember how long it took for Athlon DDR chipsets to stabilize, and for the prices to drop. I'm not expecting a reliable, affordable Hammer/Opteron system until at least mid-2003.
Now's as good a time to buy as any (just not for the top-of-the-line models, with the speed war going on).
That said, I'm curious about what people are using these super-fast processors for.
Well, I was *going* to use it to try materials/chemistry simulations based on brute force approximate solutions of Schrodinger's Equation...
But, in practice, it's been for gaming. Tribes 2 ran like a slide show until I upgraded both my processor and my video card. It's also nice being able to play Amiga games under WinUAE without the sound skipping.
Ah HAH!! That's how Dr. Hfuhruhurr was able to lick his hands and stick to the wall in "The Man With Two Brains" - I always thought it was a suction effect, but it must have been Van der Waals forces.
It was probably suction. And also probably Movie Physics;).
Van der Waals forces are very weak (even hydrogen bonding). If Dr. H. could pull the same trick in vacuum, it might be van der Waals, but in air you're much better off just forming a partial vacuum by force and letting air pressure hold you in place.
If the forces in use are only Van der Waals, and these forces are present everywhere, what makes geckos, or rather their little hairs, special so that their molecules can stick to walls and mine can't?
If I understand correctly, it's because the hairs and pads are arranged so that the sticky pads can follow surface curvature down to a near-molecular level.
Most surfaces, even ones that are polished smooth, are very rough on a small scale. This roughness is actually fractal; it's not just one level of coarseness (like sandpaper), it's coarseness on many scales. Match it on one scale, and the next step finer still keeps most of the surface away from you.
So, if you put your finger on a surface, you're still not touching much of the surface, even if you press quite hard. This limits the amount of van der Waals adhesion you can get (as the effect happens over molecular distances).
A thin film of water or oil can fill the crevases and make the bonding much stronger, if you want to try sticking your fingers to things. Don't try hanging off the ceiling, though:).
Disclaimer: This explanation could be completely wrong. It's just the most plausible one I can think of.
Re:Impact on the environment (and the ground)
on
Going Up?
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· Score: 2
Cable safety is really a bugbear. The only part of the cable that will fall towards earth is the part below the point of breakage. In a worst case scenario, this is at Geosynch orbit. But what most people fail to realize is that as the cable falls it speeds up just like any other falling object. 60 or so Km up the cable is falling fast enough to burn up completely on reentry. So only 60 km or less of cable reaches the ground even in a worst case breakage scenario.
I'm playing Devil's Advocate in assuming that the energy would be concentrated in one place. If you assume a more diffuse distribution, then you just look at recent volcanic eruptions to pick a maximum energy/mass release into the atmosphere. In practice this would pretty much allow as large a cable as you want.
I feel more comfortable assuming an impossibly bad worst-case scenario, though (force of habit; I'm in engineering).
Re:Impact on the environment (and the ground)
on
Going Up?
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· Score: 2
According to the article, the power source is a laser shot from the platform, aimed at collectors on the bottom of the car. There, it's converted to electricity, and drives motors with wheels on the cable. Since intertia should keep the cable perfectly straight, it seems like a really good use of laser-powered propulsion.
The problem's not power. The problem is that your cargo has to move on the order of Mach 3 or better in order to get a decent rate of transport (remember, with a 10,000 ton cable you can only have, say 2000 tons of cargo on the cable at any given time).
You're not going to climb at that speed with wheels. A practical cable would also be about as thick as your finger, so wheels would be a bit tricky at anything faster than a slow crawl.
In the simplest case, you could just send power through the cable itself (nanotubes conduct extremely well; have two cables next to each other, and there you go).
It's the rate of cargo transport that limits the cost-effectiveness of a space elevator. You have to amortize the cost of the elevator over a relatively small maintenance window. The more cargo you can ship, the less you have to charge per kilo, and the more likely it is you'll actually find enough customers to transport the amount of cargo you need.
Impact on the environment (and the ground)
on
Going Up?
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· Score: 5, Interesting
Also what about the risk of it falling down? An orbital tower will wrap about the earth more than once if it falls. The description in Red Mars was particularly though provoking.
I used to think that this would make space elevators impractically dangerous. However, this turns out not to be the case.
The energy gained by the falling cable will be at most its gravitational potential energy, which is within a factor of two of conventional high explosives (per unit weight). Pick a maximum yield on impact, and you have a maximum cable weight. Use a thin enough cable to meet this weight restriction, and you have an adequately disaster-proof elevator (it'll make a mess, but not wreck the world's climate).
My own calculations with a 10 kT yield/cable weight came up with something that could reasonably be used for space travel and would pay for itself if you could keep the cargo moving.
The biggest problem is figuring out how to move cargo fast enough. I'd be leery of having induction motors mess with the cable itself, and if its a nanotube bundle they won't conduct in the right direction anyways. Winches are much too slow. Sheathing the cable with metal would only be practical for a very thin layer, which ends up being too thin to support the required currents without boiling off (I think). It's an interesting design problem.
The elevator they're proposing is not counterbalanced - this requires it to be even longer than if it wasn't counterbalanced, but it doesn't require a conveniently placed asteroid.:)
Um, it's still counterbalanced - by the outer half of the cable. Cut the cable in the middle, and the bottom half goes "splat" just as effectively as if the counterweight was just a big rock.
I suppose it's very clear and looking like vodka (in fact, our version of vodka called pinga). Some folks, maybe having tried previously ethanol, might conclude that an "m" is not that much difference and taste methanol.
If they're blind and ignore the different containers, they *might* - just might - be confused until they open the bottle and catch a whiff.
Put a bottle of rubbing alcohol (isopropanol) and a bottle of vodka (ethanol) next to each other, and take a whiff of each. Smell the difference? Methanol is also different.
Even if the hypothetical fool tries to drink it, they'll end up vomiting their guts out before being harmed, just as if they tried to drink laboratory alcohol or the 99% ethanol you can buy at the drug store. Lab and drug store alcohol are denatured for a reason.
I honestly don't see how anyone could confuse methanol and ethanol in practice.
If you could capture a person's mental state on paper, would you consider that a real mind? A representation of information, whether electronic or otherwise, is not ipso facto something that is conscious and has a self.
Neither is a human mind that's in stasis.
If the emulated mind changes over time, and goes through state transitions the same way a biological mind does, it's functionally equivalent in all respects, including being conscious.
If you have nanotechnology, and start doing things atom-by-atom, just consider the amount of energy required and heat generated.
Less than the heat of formation of all compounds making up the object being restructured. Possibly much less, but we'll assume the worst case for the sake of argument.
This is still very low. It's about 14 MJ/kg for water, which is about 25 cents worth of electricity.
Heat dissipation isn't a problem - you just do the transformation slowly enough to keep heat production down to a reasonable level.
There are plausible arguments against nanotech, but energy cost isn't one of them.
Addendum: I'm also assuming that you don't care if your body is an atom-by-atom copy of the original, as long as the mind is intact:). My point was that nanotech would allow ruptured cells to be returned to active duty.
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The simplified freshman chem explanation is that as you go across, the amount of shielding electrons is the same, but nuclear charge goes up, and as such, Z-effective increases. This mostly seems to counteract increased electron-electron repulsion, with things like the lanthanide contraction aside.
I'm afraid that, while interesting, this doesn't address my question, which concerned the alkali metals only (as they are presumably the most easily analyzed). I'm just going down a column, not across a row, and finding radii smaller than a naieve model would preduct.
And yes, you are correct: the shielding cannot be perfect. If it were so, the electrons would simply be repelled by one another and not hang out anywhere near the nucleus together anymore.
They still would, as the total charge of the core shells is less than the magnitude of the charge of the nucleus. Even if perfectly spherically distributed and completely inside the valence shell, they'd only cancel as many protons as there are electrons in the non-valence shells.
The (conjectured) reason shielding isn't even this good that a friend and I thougt about was that the second assumption doesn't hold (that the wavefunctions of the inner shells extend past the valence shell, causing some of their charge to not contribute to shielding).
The first assumption should hold, if I understand correctly (the charge distribution of a filled shell has spherical symmetry in the absence of external influences). OTOH, maybe the shells could induce dipoles in each other as with London forces between atoms... Bleah.
Dragging this back to my original question - is there a known, closed-form solution to the radial distribution function for the electrons in alkali metals (or even noble gases), or even a good approximate solution, or am I stuck trying to solve the Schrodinger equation the hard way?
The one where they steal a car from an amusement park ride, and the computer create a force field around it? Damn it, my day is ruined now. I can't remember the title.
That would be Explorers. Fun movie.
The big thing about the force fields was that they cancelled _inertia_, allowing near-instant acceleration/decelleration without pasting the occupants. This is mentioned briefly by the "nerd" character near the beginning of the film.
Actually, they are all rougly the same size, regardless of atomic weight. This is one of the interesting things about quantum mechanics and atomic physics. *All* atoms are between 0.5 and 2.5 Angstroms (1e-10 m)with Cesium being the largest (bigger than Uranium) and Nitrogen? being the smallest. Silicon isn't very large, however.
Hydrogen's the smallest, according to my books, with a radius of something like 0.53 angstroms (been a while since I looked it up).
What confuses me is why the atomic radii don't go up as the square of the number of shells. The alkali metals will have a single electron in the outermost shell, with the nucleus shielded by the inner shells, and so having an apparent charge of one. This seems to give a system with size equivalent to the nth energy level of an electron in hydrogen, which goes up as the square of the shell number.
I and the friends I asked about this speculate that because the electrons in the sheilding shells are smeared out radially, the outermost shielding shell extends past the valence shell's nominal radius, and so the core is only partly shielded, but I haven't seen any description to date of how you work out what the radii actually end up being.
Any pointers/quick explanations?
pay close attention: english is a living language. If enough people think that the correct plural spelling of virus would be potatoe, then potatoe it is!
I'm afraid I'm with Clippy on this one:
Clippy: Is this the same principle of common usage that keeps sending us all the spelling mistakes, and thinks it's ok to stick an apostrophe into any word ending in 's' no matter whether it's a contraction or a plural?
Clippy: Because if so, it can bite my skinny wire ass!
It's called electrolysis. You separate salt water into
Hydrogen a highly-reactive gas, thus antibiotic.
Oxygen, an oxidizer (duh), oxidation is about the most commonly used method of disinfection.
Sodium, a highly reactive chemical and thus disinfectant.
Chlorine, a superoxidizer (see above).
Actually, you just get the most easily reduced/oxidized species coming out. This means chlorine and hydrogen. The water stays water, and the sodium displaces the removed hydrogen to form sodium hydroxide. So, your saltwater turns into oven cleaner, which is not safe to drink, and you get chlorine gas bubbling off, which works quite well as a disinfectant (and is already used).
I wouldn't worry about the hydrogen. It's not terribly reactive, contrary to what you appear to have heard. It does burn, but you won't have enough present to worry about.
If they're using this for disinfecting, what's probably happening is that they're producing sodium chlorate. This can be formed instead of chlorine gas if your electrodes are close enough together that the ion species can mix. Sodium chlorate is a strong oxidizing agent; in weak solutions, it should be a decent disinfectant. I *really* wouldn't drink it, though (it's poisonous in significant amounts).
Contrary to what the article says, I seriously doubt you could mist a letter with chlorate-rich water and have it stay dry while being disinfected. You'd also have the nasty side effect of the letter becoming quite flammable when the mist dried, if you sprayed any substantial amount of solution on it (powerful oxidizer, remember; unstable enough that it can even explode on its own if provoked enough).
Alternatively, they could just be doing standard electrolysis and burning the hydrogen and chlorine together to get hydrogen chloride. On contact with water (or bacteria) it'll turn into hydrochloric acid, and so would be quite poisonous.
Or they could be arcing through the air using the water as an electrode, to produce ozone or nitric acid vapour. The salt wouldn't be doing much in this scenario (except making the water conduct).
In summary, the possible reaction paths are a bit more complicated than you're painting, though I agree that the article's claims are at the very least exaggerated.
I knew I'd seen something very much like this before.
Anyone remember Omnibot?
...Assuming a rock with density 5000 kg/m^3 and a volume of (1km)^3...
Aren't we talking about almost negligible gravitational forces from the asteroid itself? If escape velocity from the asteroid itself were an issue, I'd think we were screwed no matter what at that point, that thing would be really huge. :)
The escape velocity from asteroids is small (though non-negligeable). However, you're trying to impart it to a billion tonnes of rock. This makes the energy required significant.
Still quite do-able. My back-of-the-envelope numbers say the equivalent of a few kT is required (plus whatever is needed to actually shatter the rock, times whatever inefficiency factor you assume for force transmission).
everything comes back you know. nuking a asteroid heading towards earth is bound to have debris falling our way, and radioactive ones too.
It's far better to have 1% of the asteroid's debris cone hitting Earth than having the whole thing come raining down on us.
The environmental impact of any residual radioactivity from the nuke used to fragment it is far, far less than the environmental impact of the original strike (in the absence of interference), and probably even of the few chunks that still hit Earth.
Why not just shatter the asteroid? Seems like that would take less energy than either your or his sugesstion. Let the atmosphere do the work, just break it up is chunks that are small enough to ablate down to non-threatning pieces.
The problem is that most asteroids large enough to be a problem would cause serious problems even raining down into the atmosphere as gravel. Large volcanic eruptions mess up our climate quite nicely; vapourizing a few billion tonnes of rock on re-entry would have much the same effect.
What you really have to do is fragment the asteroid with enough force that the pieces all have local escape velocity [from the asteroid], and do it far enough back in its orbit that most of the pieces miss Earth [the hard part, as we'd need months to years of advance notice].
This is still probably the most practical way of dealing with an Earth-threatening asteroid.
What we really need to do is figure out how to take some of the mass of the asteroid and accelerate it, using this as the reactant to change the path. Sort of like installing a rail gun on the asteroid, and firing off bits of asteriod like b-b's to get the asteroid to move in the opposite direction.
Or haul a bigarsed ion drive over to it, and use charged silica vapour as the reaction mass. Bring spare ionization screens...
I'm still in the "nuke it" camp, myself.
I can understand using certification as a business model and to help develop a stable of knowledgable consultants for projects. But having a per year fee on top of the certification seems like you're paying for them to help market you.
That depends. You could make a good argument for mandatory recertification to make sure people haven't just forgotten everything they crammed for the exam, and to keep them up to date with improvements. Making certification expire yearly accomplishes this.
Personally I think having to pay on top of the certification starts to be a bit much. If I pay the 5K and don't get any work out of it, what have they really done for me?
They've given you permission to use their label when looking for work, which presumably greatly increases your chances of finding it. If you still can't find any, that doesn't invalidate what they gave you.
I'm not arguing that JBoss certification is *worth* $5K - that's a value decision each buyer has to make for themselves. I'm just pointing out that there is a justification for what they're doing, even if you disagree with the price point.
I'm on the fence, but at the rate I've actually done anything to build my next system (hey, I did buy a cabinet! :-) the wait for the Hammer shouldn't be much longer (why does this name summon the memory of the artwork inside PF:The Wall, hmm, something there, but what...)
I'm waiting too, but that's because I don't think I'll have to upgrade for at least a year.
Remember how long it took for Athlon DDR chipsets to stabilize, and for the prices to drop. I'm not expecting a reliable, affordable Hammer/Opteron system until at least mid-2003.
Now's as good a time to buy as any (just not for the top-of-the-line models, with the speed war going on).
That said, I'm curious about what people are using these super-fast processors for.
Well, I was *going* to use it to try materials/chemistry simulations based on brute force approximate solutions of Schrodinger's Equation...
But, in practice, it's been for gaming. Tribes 2 ran like a slide show until I upgraded both my processor and my video card. It's also nice being able to play Amiga games under WinUAE without the sound skipping.
Ah HAH!! That's how Dr. Hfuhruhurr was able to lick his hands and stick to the wall in "The Man With Two Brains" - I always thought it was a suction effect, but it must have been Van der Waals forces.
;).
It was probably suction. And also probably Movie Physics
Van der Waals forces are very weak (even hydrogen bonding). If Dr. H. could pull the same trick in vacuum, it might be van der Waals, but in air you're much better off just forming a partial vacuum by force and letting air pressure hold you in place.
Water just helps you get a better seal for this.
If the forces in use are only Van der Waals, and these forces are present everywhere, what makes geckos, or rather their little hairs, special so that their molecules can stick to walls and mine can't?
:).
If I understand correctly, it's because the hairs and pads are arranged so that the sticky pads can follow surface curvature down to a near-molecular level.
Most surfaces, even ones that are polished smooth, are very rough on a small scale. This roughness is actually fractal; it's not just one level of coarseness (like sandpaper), it's coarseness on many scales. Match it on one scale, and the next step finer still keeps most of the surface away from you.
So, if you put your finger on a surface, you're still not touching much of the surface, even if you press quite hard. This limits the amount of van der Waals adhesion you can get (as the effect happens over molecular distances).
A thin film of water or oil can fill the crevases and make the bonding much stronger, if you want to try sticking your fingers to things. Don't try hanging off the ceiling, though
Disclaimer: This explanation could be completely wrong. It's just the most plausible one I can think of.
Cable safety is really a bugbear. The only part of the cable that will fall towards earth is the part below the point of breakage. In a worst case scenario, this is at Geosynch orbit. But what most people fail to realize is that as the cable falls it speeds up just like any other falling object. 60 or so Km up the cable is falling fast enough to burn up completely on reentry. So only 60 km or less of cable reaches the ground even in a worst case breakage scenario.
I'm playing Devil's Advocate in assuming that the energy would be concentrated in one place. If you assume a more diffuse distribution, then you just look at recent volcanic eruptions to pick a maximum energy/mass release into the atmosphere. In practice this would pretty much allow as large a cable as you want.
I feel more comfortable assuming an impossibly bad worst-case scenario, though (force of habit; I'm in engineering).
According to the article, the power source is a laser shot from the platform, aimed at collectors on the bottom of the car. There, it's converted to electricity, and drives motors with wheels on the cable. Since intertia should keep the cable perfectly straight, it seems like a really good use of laser-powered propulsion.
The problem's not power. The problem is that your cargo has to move on the order of Mach 3 or better in order to get a decent rate of transport (remember, with a 10,000 ton cable you can only have, say 2000 tons of cargo on the cable at any given time).
You're not going to climb at that speed with wheels. A practical cable would also be about as thick as your finger, so wheels would be a bit tricky at anything faster than a slow crawl.
In the simplest case, you could just send power through the cable itself (nanotubes conduct extremely well; have two cables next to each other, and there you go).
It's the rate of cargo transport that limits the cost-effectiveness of a space elevator. You have to amortize the cost of the elevator over a relatively small maintenance window. The more cargo you can ship, the less you have to charge per kilo, and the more likely it is you'll actually find enough customers to transport the amount of cargo you need.
Also what about the risk of it falling down? An orbital tower will wrap about the earth more than once if it falls. The description in Red Mars was particularly though provoking.
I used to think that this would make space elevators impractically dangerous. However, this turns out not to be the case.
The energy gained by the falling cable will be at most its gravitational potential energy, which is within a factor of two of conventional high explosives (per unit weight). Pick a maximum yield on impact, and you have a maximum cable weight. Use a thin enough cable to meet this weight restriction, and you have an adequately disaster-proof elevator (it'll make a mess, but not wreck the world's climate).
My own calculations with a 10 kT yield/cable weight came up with something that could reasonably be used for space travel and would pay for itself if you could keep the cargo moving.
The biggest problem is figuring out how to move cargo fast enough. I'd be leery of having induction motors mess with the cable itself, and if its a nanotube bundle they won't conduct in the right direction anyways. Winches are much too slow. Sheathing the cable with metal would only be practical for a very thin layer, which ends up being too thin to support the required currents without boiling off (I think). It's an interesting design problem.
The elevator they're proposing is not counterbalanced - this requires it to be even longer than if it wasn't counterbalanced, but it doesn't require a conveniently placed asteroid. :)
Um, it's still counterbalanced - by the outer half of the cable. Cut the cable in the middle, and the bottom half goes "splat" just as effectively as if the counterweight was just a big rock.
I suppose it's very clear and looking like vodka (in fact, our version of vodka called pinga). Some folks, maybe having tried previously ethanol, might conclude that an "m" is not that much difference and taste methanol.
If they're blind and ignore the different containers, they *might* - just might - be confused until they open the bottle and catch a whiff.
Put a bottle of rubbing alcohol (isopropanol) and a bottle of vodka (ethanol) next to each other, and take a whiff of each. Smell the difference? Methanol is also different.
Even if the hypothetical fool tries to drink it, they'll end up vomiting their guts out before being harmed, just as if they tried to drink laboratory alcohol or the 99% ethanol you can buy at the drug store. Lab and drug store alcohol are denatured for a reason.
I honestly don't see how anyone could confuse methanol and ethanol in practice.
If you could capture a person's mental state on paper, would you consider that a real mind? A representation of information, whether electronic or otherwise, is not ipso facto something that is conscious and has a self.
Neither is a human mind that's in stasis.
If the emulated mind changes over time, and goes through state transitions the same way a biological mind does, it's functionally equivalent in all respects, including being conscious.
If you have nanotechnology, and start doing things atom-by-atom, just consider the amount of energy required and heat generated.
Less than the heat of formation of all compounds making up the object being restructured. Possibly much less, but we'll assume the worst case for the sake of argument.
This is still very low. It's about 14 MJ/kg for water, which is about 25 cents worth of electricity.
Heat dissipation isn't a problem - you just do the transformation slowly enough to keep heat production down to a reasonable level.
There are plausible arguments against nanotech, but energy cost isn't one of them.
Consciousness is composed of the states of the cells in your nervous and endocrine systems (and various associated phenomena).
I disagree.
Seeing as neither of us will have an easy time proving their assertation, I suggest we follow my original suggestion and wait until someone tries it.
Addendum: I'm also assuming that you don't care if your body is an atom-by-atom copy of the original, as long as the mind is intact :). My point was that nanotech would allow ruptured cells to be returned to active duty.