Re:Didn't here the E or T words..
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Cradle to Cradle
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· Score: 2
Actually, the best PV cells in production right now are multi-junction GaAs/Ge cells that run at around 26%-28% efficiency. I've heard that there are already 30%-32% cells in the labs.
Cool!.
Do these suffer from degradation over time as with other high-efficiency designs, or are they more durable?
You surely mean purchase several dozen new games, all of the same title every Christmas, because after all, it is clearly illegal to purhcase ONE copy and share it with all the other members of the lab.
And as it's clearly illegal, of *course* you'd buy one copy per machine. Duh.
I doubt the school would jump and down with joying knowing that they would have to shell out $50-$60 every christmas PER STUDENT in the 'game club'.
a) Per machine, not per student. And given that you typically have a 3 or 4 player maximum for RTS games, you'd actually only need to buy 4 copies. Set up one quartet of machines with the new game, leave the others with the old selection.
b) Do you read?
either with school funds or by "game-lab dues" paid by the students
Even if we're buying one copy per student (i.e. we have that many machines and we install on all of them), you have a year's worth of dues to pay with. $5 a month for 10 months is... surprise surprise... about the cost of one game per year per student.
Please read and apply common sense before responding.
Why is it that running around on a space station and shooting people (a la UT or Q3) is frowned upon by parents, but building up a small army and slaughtering opponents by the hundres (a la Starcraft/TA) is ok? Don't get me wrong, I like all the games mentioned above (except TA, only because I haven't played it yet). The irony of that statement just had to make me comment.
My guess? Because FPSs are more "personal". However, nothing political is required to make sense.
More ways of harnessing solar energy.
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Cradle to Cradle
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· Score: 2
Other important methods of harvesting solar energy that I forgot: hydroelectric power and wind power.
Both are manifestations of the weather system, which is a giant solar-driven heat engine. While it's doubtful that wind power could provide a reasonable amount of energy on a continental scale, hydroelectric power certainly can. Both of these forms of solar energy harvesting are quite efficient, because you get a lot of the energy concentration for free.
Re:Litter doesn't decompose quickly.
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Cradle to Cradle
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· Score: 2
I am not sure that your green sofa would decompose in your living room...unless your living room happened to be a dark, moist, warm area, filled with microbes and available nutrients. [...] By your logic, paper towels would not exist.
Good point.
However, after you spill something on it a few times, I think the inside of your sofa would qualify as a dark, moist, warm, microbe-haven.
RTS games like Starcraft, Total Annihilation, and so forth are always popular, and shouldn't raise too much concern with parents. As for choosing the games themselves, why not just let the students vote on it? Buy a new game every Christmas for the lab, either with school funds or by "game-lab dues" paid by the students.
Simulation games will be moderately popular too, but multi-player games are usually nicer.
I actually think that adding a few select FPSs (like Tribes) that emphasize wouldn't be a bad idea, but I agree that that probably wouldn't fly too well with the parents.
As a third option, you can load SDL on all of the programming course machines and encourate the students to write their own game(s). This wouldn't replace store-bought games, but would be a neat side project that the students would be enthusiastic about and would learn a lot from. I know I had a lot of fun doing this in my high school days (wrote a Tetris clone and a version of Battleship that worked multi-player by using files in a shared directory to communicate).
Think of how often a device made of plastic will break & become useless. We have very few products left which can really be repaired.
Plastic is actually pretty easy to repair (at least if it snaps). Acetone will glue some plastics, and methylene chloride (available at hobby stores and possibly hardware stores) will glue almost all of them. Both of them are actually strong solvents, which dissolve and re-form the plastic around the break.
Now, I'm lazy enough that I'll probably buy a new $3 plastic widget instead of repairing a broken one, but it's still _do-able_:).
[Note: Use methylene chloride outdoors only. The fumes are quite dangerous.]
Litter doesn't decompose quickly.
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Cradle to Cradle
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· Score: 2
Litter wouldn't be a problem if it decomposed anytime soon, now would it? Tree leaves in autumn, for example, are nature's litter.
Ever try leaving leaves on your lawn to decompose instead of raking them?
It doesn't work so well:). I'm sure if you look around hard right *now*, you'll find mostly-intact leaves from last autumn lying around. They'll eventually degrade into random soil organics, but they'll look pretty ugly while they're doing it. And by the time they do, the next few layers of leaves will be on top.
Man-made substances are even worse for this. We want them to last for years with no degradation when we store them, so they take even longer to break down in the environment. Paper is just about the most biodegradable substance we produce, but readable newspapers from 80 years ago have been pulled out of landfills. Granted, part of this is the environment of the landfill itself, but my point holds.
A "green" sofa whose upholstry biodegraded in a reasonable time would start degrading in your living room a month or two after you bought it. A sofa that did not biodegrade over the 5+ years you usd it would take its sweet time degrading in the landfill.
In summary, I don't think nature is a fast enough recycler to be worth using (at least without help).
Re:Didn't here the E or T words..
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Cradle to Cradle
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· Score: 2
I can't believe that got modded up. Anyone who thinks that solar energy can provide energy at anywhere near the current consumption rate is insane.
Sure it can. Solar energy flux (at peak generation) is 1 kW/m2. You get a gigawatt per square kilometre. Even with a 10% duty cycle, the area of (ideal, perfect) solar arrays needed to power a city is much less than, say, the farmland required to feed that city.
The best photovoltaic panels currently in the laboratory are about 15% efficient. Commercial panels are 5%. Photovoltaics will be a lot more practical in the next 20 years or so, when thin-film photovoltaics reach high enough efficiency (thin film cells also require far less energy/materials to produce, before you bring up those arguments).
For a more practical solution, you can build arrays of aluminum or steel mirror-troughs to focus light on pipes and use a conventional heat engine to extract energy.
This isn't even touching space-based solar power generation, which has the potential to be a lot cheaper (you can make big concentrators very thin and light, as structural stresses are far less).
IMO, we're likely to go with fusion instead of solar, but solar is still capable of running the world (it's just cheaper for the time being to use fossil fuels).
NERVA rockets (which use a reactor to superheat hydrogen for propulsion, at much higher efficiency levels than chemical rockets) are the key to exploration and exploitation of the Solar System. Our chemical rockets have hit peaks of efficiency limited by the physics of combustion that are not surmountable, and they fall far short of the ISP (a measure of efficiency and power) needed for manned exploration of our neighborhood.
NERVA rockets are not the only practical high-ISP drive by any stretch. As long as you have transit times of months or more, ion drives and other electric drives work fine, and give you even more Isp than NERVA (which is limited to exhaust temperatures that the engine core can withstand).
While you'd still need a nuclear plant for power production in the outer solar system, in the inner solar system solar powered ion or plasma drives work quite well.
NERVA *would* be useful for ground-to-orbit trips, as it can give enough thrust for more than 1g acceleration (unlike ion, plasma, and other exotics), but this isn't the bottleneck for exploration/colonization. Until spacecraft engineering becomes as well-understood and routine as, say, automobile engineering, any man-rated spacecraft you send up will cost enough to make launch costs insignificant.
Any construction that requires enough material for launch costs to be the dominant cost wouldn't be supplied from earth - the moon is a very convenient source of metals, glass, ceramics, etc, and I'm sure someone will point out that asteroidal material is fairly accessible as well.
In short, there isn't any application for which NERVA rockets are the only solution.
A question about this goat spider silk - does spider silk scale linearly? [...] What I wonder is if spider webs are similar - amazing properties on a spider scale, but pretty pathetic at a larger scale.
All materials obey the square/cube law (strength scales as the square of the scale, weight as the cube). The important number for cables is tensile strength per unit area. This number is independent of scale.
Spider silk and many other more common polymers have a tensile strength comparable to or greater than that of steel, while weighing much less. The down-side is usually that they stretch more when force is applied (lower elastic modulus).
Very very little non-volitile ram is used (retains data without power) which would be needed for a permenant storage device.
I'm afraid vast amounts of this, too, are produced. Flash memory cards are quite common for a wide variety of devices. The retail price you see for flash modules is mostly markup; producing flash RAM is almost as cheap as producing normal RAM (well, per unit die area). You have a couple of extra mask steps for the floating gates, but nothing exotic.
Has anyone built a home-made UPS yet that relies on a flywheel for temporary power delivery? Not as crazy it sounds! See this article from IEEE Spectrum [scientecmatrix.com]. Not as crazy as it sounds!
I thought briefly about this, but 1) energy density *really* sucks compared to batteries unless you're buying a carbon-fiber flywheel for $lots, and 2) a catastrophic flywheel failure is even worse than a catastrophic battery failure. It takes surprisingly little energy to make a very effective bomb (it's the momentum that gets you).
Batteries are cheap; batteries work. Just get marine deep-discharge ones and be prepared to handle catastrophic failures down the road (batteries outdoors, and limestone gravel is your friend).
The thing I might wonder about is artificial diamonds. I've heard they can create very small, low quality diamonds artificially, perhaps that would be sufficient for this process, but I know very little and it could very well be a mistake in facts on my part
Synthetic diamond gemstones have been around for quite a while now, though only small ones are cheap enough to be worthwhile to produce. They're commonly used. I don't know what the most common method used to produce them is nowadays, but older schemes made them by applying pressure directly to carbon samples.
Industrial diamond is almost all synthetic. It's produced, more or less, by setting off a bomb on top of carbon powder and diamond dust. The result doesn't look pretty, but is functional.
The semiconductor industry already produces diamond films for a few applications by the same methods they use for other types of film (CVD, etc). You typically don't use buckyballs as the carbon source, as other cheaper chemicals work just as well ("cheap" being relative, as whatever's being used has to be ultra-pure to avoid defects). In practice, diamond-based integrated circuits would be manufactured using techniques like this.
People have been experimenting with diamond-based integrated circuits for a while now. They can operate at much higher temperatures than most other IC technologies, but doping is more difficult (requires much higher dopant concentrations, and there may be other problems).
Diamond MEMS would most logically be produced by methods similar to diamond ICs, to make maximum use of existing technology.
Bah.. If you start producing 20x more ram I bet the price would drop somewhat.
Um, no.
RAM is already produced in such vast quantities that economies of scale won't give you any further benefit. Think for a minute about how much is used yearly.
Take something like a web browser. Given a bit of wizardry (obviously, we need to consider concurrency and critical sections), you could have separate images downloaded and processed by separate processors. Your flash ad would run on another processor.
Web tasks tend not to be processor-bound. You're limited by your 'net connection for these (you can draw an image far faster than you can download it).
It turns out that most of the tasks people do either aren't strong loads on the system at all (e.g. surfing, email, word-processing, spreadsheets) or are limited by some other part of the system (memory bandwidth, disk, or graphics card).
Of the remaining tasks, most aren't easily parallelized (or at least not automatically). Of the ones that are partly parallelizable, the serial part of the task tends to cause bottlenecking, which gives you rapidly-diminishing returns (look up "Amdahl's Law" for a deeper explanation of this).
The only processor-intensive, easily-parallelizable task that's currently done is 3D gaming, and the processing load for that is mainly handled by the video card, not the CPU. Graphics cards already parallelize to some degree on-die, but can't have more than one graphics chip without driving up the price of the card considerably. While this can be (and is) done for high-end cards, consumers prefer cards that are at a sane price.
In short, in the one place where most people would benefit from a multi-chip solution, you won't see it.
Frankly, I'm wondering what's stopping us from using this approach to increasing performance? Is this like the fact that OEMs equip the low-end PCs with too little RAM so that Joe Shmoe will buy a new one as quickly as possible, since he does not know that spending 100 bucks on more RAM will make his computer last another year or two?
Actually, it's that Joe Schmoe *prefers* to buy as cheap a computer as he can get his hands on. This is why you don't see many machines sold with a vast amount of RAM, and why you don't see many dual-processor machines sold.
People apparently really _do_ just want cheap machines, not optimized machines.
And, really, as long as the focus is on the gigahertz, do the chip makers really concentrate on making their designs as efficient as possible?
Yes - if you mean performance-efficient. Being able to say that you kick your competitor's ass in benchmarking does make some difference (especially if games are some of those benchmarks).
There isn't much incentive to be power-efficient beyond the amount needed to keep your chip from melting into slag, for desktops, at least. There are many low-power offerings already used in palmtops and embedded devices.
Power efficiency _is_ an issue, as reasonable power dissipation is the primary limit to a computer's clock rate. However, as long as people are willing to use computers with fans and heatsinks, your desktop processor will dissipate 50W+.
This comes up every time a storage article is posted.
It's shot down every time, but it keeps getting re-posted.
Calculate the cost of the RAM in your computer, per gigabyte. Now, calculate the cost of storage in your hard drive, per gigabyte.
Notice that the difference is several orders of magnitude.
In order for solid state drives to be cheaper than magnetic drives, the cost of pick-your-RAM-flavour has to get a HUNDRED TIMES cheaper, while the cost of hard drives has to NOT get cheaper.
This might happen in the far future if prices drift and keep drifting, but not any time soon.
You can also make a good argument for it being intrinsically cheaper to manufacture hard drive platters than RAM arrays, but this has been beaten to death already.
I'd like to know more about the ones that are just above the brown dwarf level. Could something have terrestrial/Jovian style weather (wind, clouds, hurricanes) and also be fusing inside? That would be cool (hot).
Anything with a convective layer and a heat gradient should have weather, so yes, everything from moons-with-atmospheres on up through full-blown stars should have it.
The convective layer in red dwarfs is much deeper than in more energetic stars like the sun, as they're cooler (convective layer stops when the star material gets hot enough for radiative transmission to be the dominant heat transfer mechanism). Both still have them, though.
Winds and storms should be present aplenty, but clouds are a bit iffy. They should only happen where a phase transition is possible (e.g. from plasma to monatomic gas, and from monatomic gas to molecular gases). This would be right at or near the "surface" of a star (maybe deeper for a red dwarf).
Weather patterns would be very different from conventional weather in layers hot enough to be plasma, as plasma interacts strongly with the star's magnetic field. This region would be anything below a certain depth (i.e. most of the convective layers) and in the corona, for an active star.
Only your transmitters need to be cheap. If you can build a box and run it out to a few hundred antennas, the home-on-jam devices keep knocking out your antennas. At $500,000 each for an anti-jammer missile and $500 for an antenna and a bit of coax the numbers aren't good.
You'd need an amplifier at the antenna; aggressive jamming requires a bit more power than off the shelf coax will carry. But the idea is good (and in my own reply).
Also keep in mind that some of the cheap spark gap transmitters work great for messing up some types of transmissions and Telsa had lots of cheap devices that will mess with a wide range of spectrum. The reason that the modern military jamers are so expensive is they only want to jam their enemys signals not their own. If your not using radio to such a high level you can just bust the whole spectrum.
The problem is that spread-spectrum communication can tolerate a very high noise floor (hundreds of times higher than the magnitude of the signal in any given spectral range, or more). It manages this by taking advantage of the fact that true noise will cancel a lot of itself out if added across many spectrum areas (or areas of signal space if you're using coding to get spread-spectrum), while the signal just adds constructively to itself. In order to make noise that adds constructively, you have to know the scrambling codes used by the signal you're trying to jam. Otherwise, you have to be far, far louder than the signal you're trying to swamp (do-able, but not with anything small).
Man, I hope they find a lot of good child actors. With the exception of the sixth Sence and the City of Lost Children I have yet to see an excellent job done by a child filling a more adult personality.
Hardly movie-quality, but - the kid who played Picard in the "four people get turned into children" TNG episode did a damned good job.
As pointed our above, you are going to need one hell of a large emitter to make this work. Home-on-jam makes being a large emitter a dangerous (if not fatal) proposition. Your choice then becomes one of jam and die, or don't jam and somebody else dies. The real question is can you produce enough jammers to handle the second or third wave of these things and are the jammers cheaper than the remotes?
Excellent points.
If I were designing a jamming system, I'd do a few things to ameliorate (though not eliminate) this problem. The first is to use many medium-sized jamming sources instead of one large one. As long as I can approximately track the target and as long as the source dishes are large enough to allow some direction of the noise beam and as long as I have the infrastructure and logistics support to support the many small stations/deployed jamming units, this should make life much harder for the people launching radio-seeking missiles. It also makes the jammer cost to missile cost ratio a bit more level.
Another option would be to send weather balloons with metal spheres (radio scattering reflectors) into the air around the jamming installation. When an incoming missile is detected, the jammer shuts down and a secondary jammer paints one of the reflectors as a sacrificial target. This would make the cost of the sacrificial target much less than the cost of the missile being fired at it. To make the location of your jammer station less obvious, sacrificial targets could be launched from scattered points some distance away from the jammer (but close enough to be convincing missile decoys).
There are problems with both of these stragegies, and solutions to those problems:). That's what makes thought experiments like this so much fun.
Of course, the best solution (hinted at in my previous post) is just to have agents steal the radio codes. This lets you snoop, scramble or usurp them at your discretion with much less effort required. Getting agents' hands on such sensitive information is left as an exercise...
I wonder how effective jamming would be if they took advantage of ultra wide-band/spread spectrum techniques, along with satellite linkages. Seems as though it would be hard to jam that stuff.. all the plane needs to do is look up and use a few gHz of frequencies, and you'd be hard pressed to block that.
Depends on how much effort you're willing to put in the jamming.
Jamming is just sending enough radio noise at the target to make the noise in the desired part of signal space louder than the signal.
For a kid's walkie-talkie, that means dumping noise into a narrow region of spectrum. For frequency-hopping radio, that means dumping noise into many regions of spectrum at once (unless your spies have retrieved the hopping algorithm). For impulse-based UWB, you dump a lot of randomly-timed impulses out (easier if your spies or observations give you approximate timings). For scrambled spread-spectrum radio, you either dump an ungodly amount of noise into the band used to raise the noise floor enough that even coding and correlation don't save you (do-able), or you get your spies to find the family of scrambling codes used and pattern your noise into that band of signal space.
In summary, jamming will always work, either through espionage or through brute force and ignorance.
Where will we get the "flying attack porcupines"?
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Unlimited Airwaves
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· Score: 4, Interesting
After looking over the lecture slides a few links in, the authour seems to just be saying that congestion (and hence spectrum scarcity) will be a non-issue if we just switch to point-to-point transciever schemes instead of broadcast schemes (either by using cells and a backbone or by clever coding).
This is great, and would indeed increase bandwidth to silly levels... except for the fact that implementing a pervasive point-to-point network with high local bandwidth and low leakage is a PITA of vast proportions.
Summary: Good idea, and it'll certainly see greater use in the future, but it's not "unlimited airwaves" by a long shot.
The 3d market was 3DFX's to lose. What killed 3DFX was that their good cards rewuired a 2d card to run. They were 3d only. The Banshee, which did incorporate a 2d core was late and always seemed buggy. By the time they got their act together with the 3000 series it was too late.
On the contrary, I think their death was post-3000.
The Voodoo 3 went toe to toe with all of the other offerings of its time, at least when it was rolled out. nVidia had a card that could match it, but not beat it.
3dfx dropped the ball when designing a successor to the Voodoo 3. The V4 sank with nary a ripple and the V5 was rushed into release while immature (great idea, immature execution that was made huge and power-hungry to compensate).
It's quite likely that the problems that caused the V5 to tank started even before the V3 days, but the V3 itself was a solid product.
Slashdot Mirror
Actually, the best PV cells in production right now are multi-junction GaAs/Ge cells that run at around 26%-28% efficiency. I've heard that there are already 30%-32% cells in the labs.
Cool!.
Do these suffer from degradation over time as with other high-efficiency designs, or are they more durable?
"Buy a new game every Christmas for the lab"
You surely mean purchase several dozen new games, all of the same title every Christmas, because after all, it is clearly illegal to purhcase ONE copy and share it with all the other members of the lab.
And as it's clearly illegal, of *course* you'd buy one copy per machine. Duh.
I doubt the school would jump and down with joying knowing that they would have to shell out $50-$60 every christmas PER STUDENT in the 'game club'.
a) Per machine, not per student. And given that you typically have a 3 or 4 player maximum for RTS games, you'd actually only need to buy 4 copies. Set up one quartet of machines with the new game, leave the others with the old selection.
b) Do you read?
either with school funds or by "game-lab dues" paid by the students
Even if we're buying one copy per student (i.e. we have that many machines and we install on all of them), you have a year's worth of dues to pay with. $5 a month for 10 months is... surprise surprise... about the cost of one game per year per student.
Please read and apply common sense before responding.
Why is it that running around on a space station and shooting people (a la UT or Q3) is frowned upon by parents, but building up a small army and slaughtering opponents by the hundres (a la Starcraft/TA) is ok? Don't get me wrong, I like all the games mentioned above (except TA, only because I haven't played it yet). The irony of that statement just had to make me comment.
My guess? Because FPSs are more "personal". However, nothing political is required to make sense.
Other important methods of harvesting solar energy that I forgot: hydroelectric power and wind power.
Both are manifestations of the weather system, which is a giant solar-driven heat engine. While it's doubtful that wind power could provide a reasonable amount of energy on a continental scale, hydroelectric power certainly can. Both of these forms of solar energy harvesting are quite efficient, because you get a lot of the energy concentration for free.
I am not sure that your green sofa would decompose in your living room...unless your living room happened to be a dark, moist, warm area, filled with microbes and available nutrients. [...] By your logic, paper towels would not exist.
Good point.
However, after you spill something on it a few times, I think the inside of your sofa would qualify as a dark, moist, warm, microbe-haven.
I actually think that adding a few select FPSs (like Tribes) that emphasize teamwork wouldn't be a bad idea
:).
Figures I'd screw up the one time I decide not to preview
RTS games like Starcraft, Total Annihilation, and so forth are always popular, and shouldn't raise too much concern with parents. As for choosing the games themselves, why not just let the students vote on it? Buy a new game every Christmas for the lab, either with school funds or by "game-lab dues" paid by the students.
Simulation games will be moderately popular too, but multi-player games are usually nicer.
I actually think that adding a few select FPSs (like Tribes) that emphasize wouldn't be a bad idea, but I agree that that probably wouldn't fly too well with the parents.
As a third option, you can load SDL on all of the programming course machines and encourate the students to write their own game(s). This wouldn't replace store-bought games, but would be a neat side project that the students would be enthusiastic about and would learn a lot from. I know I had a lot of fun doing this in my high school days (wrote a Tetris clone and a version of Battleship that worked multi-player by using files in a shared directory to communicate).
Think of how often a device made of plastic will break & become useless. We have very few products left which can really be repaired.
:).
Plastic is actually pretty easy to repair (at least if it snaps). Acetone will glue some plastics, and methylene chloride (available at hobby stores and possibly hardware stores) will glue almost all of them. Both of them are actually strong solvents, which dissolve and re-form the plastic around the break.
Now, I'm lazy enough that I'll probably buy a new $3 plastic widget instead of repairing a broken one, but it's still _do-able_
[Note: Use methylene chloride outdoors only. The fumes are quite dangerous.]
Litter wouldn't be a problem if it decomposed anytime soon, now would it? Tree leaves in autumn, for example, are nature's litter.
:). I'm sure if you look around hard right *now*, you'll find mostly-intact leaves from last autumn lying around. They'll eventually degrade into random soil organics, but they'll look pretty ugly while they're doing it. And by the time they do, the next few layers of leaves will be on top.
Ever try leaving leaves on your lawn to decompose instead of raking them?
It doesn't work so well
Man-made substances are even worse for this. We want them to last for years with no degradation when we store them, so they take even longer to break down in the environment. Paper is just about the most biodegradable substance we produce, but readable newspapers from 80 years ago have been pulled out of landfills. Granted, part of this is the environment of the landfill itself, but my point holds.
A "green" sofa whose upholstry biodegraded in a reasonable time would start degrading in your living room a month or two after you bought it. A sofa that did not biodegrade over the 5+ years you usd it would take its sweet time degrading in the landfill.
In summary, I don't think nature is a fast enough recycler to be worth using (at least without help).
I can't believe that got modded up. Anyone who thinks that solar energy can provide energy at anywhere near the current consumption rate is insane.
Sure it can. Solar energy flux (at peak generation) is 1 kW/m2. You get a gigawatt per square kilometre. Even with a 10% duty cycle, the area of (ideal, perfect) solar arrays needed to power a city is much less than, say, the farmland required to feed that city.
The best photovoltaic panels currently in the laboratory are about 15% efficient. Commercial panels are 5%. Photovoltaics will be a lot more practical in the next 20 years or so, when thin-film photovoltaics reach high enough efficiency (thin film cells also require far less energy/materials to produce, before you bring up those arguments).
For a more practical solution, you can build arrays of aluminum or steel mirror-troughs to focus light on pipes and use a conventional heat engine to extract energy.
This isn't even touching space-based solar power generation, which has the potential to be a lot cheaper (you can make big concentrators very thin and light, as structural stresses are far less).
IMO, we're likely to go with fusion instead of solar, but solar is still capable of running the world (it's just cheaper for the time being to use fossil fuels).
NERVA rockets (which use a reactor to superheat hydrogen for propulsion, at much higher efficiency levels than chemical rockets) are the key to exploration and exploitation of the Solar System. Our chemical rockets have hit peaks of efficiency limited by the physics of combustion that are not surmountable, and they fall far short of the ISP (a measure of efficiency and power) needed for manned exploration of our neighborhood.
NERVA rockets are not the only practical high-ISP drive by any stretch. As long as you have transit times of months or more, ion drives and other electric drives work fine, and give you even more Isp than NERVA (which is limited to exhaust temperatures that the engine core can withstand).
While you'd still need a nuclear plant for power production in the outer solar system, in the inner solar system solar powered ion or plasma drives work quite well.
NERVA *would* be useful for ground-to-orbit trips, as it can give enough thrust for more than 1g acceleration (unlike ion, plasma, and other exotics), but this isn't the bottleneck for exploration/colonization. Until spacecraft engineering becomes as well-understood and routine as, say, automobile engineering, any man-rated spacecraft you send up will cost enough to make launch costs insignificant.
Any construction that requires enough material for launch costs to be the dominant cost wouldn't be supplied from earth - the moon is a very convenient source of metals, glass, ceramics, etc, and I'm sure someone will point out that asteroidal material is fairly accessible as well.
In short, there isn't any application for which NERVA rockets are the only solution.
A question about this goat spider silk - does spider silk scale linearly? [...] What I wonder is if spider webs are similar - amazing properties on a spider scale, but pretty pathetic at a larger scale.
All materials obey the square/cube law (strength scales as the square of the scale, weight as the cube). The important number for cables is tensile strength per unit area. This number is independent of scale.
Spider silk and many other more common polymers have a tensile strength comparable to or greater than that of steel, while weighing much less. The down-side is usually that they stretch more when force is applied (lower elastic modulus).
Very very little non-volitile ram is used (retains data without power) which would be needed for a permenant storage device.
I'm afraid vast amounts of this, too, are produced. Flash memory cards are quite common for a wide variety of devices. The retail price you see for flash modules is mostly markup; producing flash RAM is almost as cheap as producing normal RAM (well, per unit die area). You have a couple of extra mask steps for the floating gates, but nothing exotic.
Has anyone built a home-made UPS yet that relies on a flywheel for temporary power delivery? Not as crazy it sounds! See this article from IEEE Spectrum [scientecmatrix.com]. Not as crazy as it sounds!
I thought briefly about this, but 1) energy density *really* sucks compared to batteries unless you're buying a carbon-fiber flywheel for $lots, and 2) a catastrophic flywheel failure is even worse than a catastrophic battery failure. It takes surprisingly little energy to make a very effective bomb (it's the momentum that gets you).
Batteries are cheap; batteries work. Just get marine deep-discharge ones and be prepared to handle catastrophic failures down the road (batteries outdoors, and limestone gravel is your friend).
The thing I might wonder about is artificial diamonds. I've heard they can create very small, low quality diamonds artificially, perhaps that would be sufficient for this process, but I know very little and it could very well be a mistake in facts on my part
Synthetic diamond gemstones have been around for quite a while now, though only small ones are cheap enough to be worthwhile to produce. They're commonly used. I don't know what the most common method used to produce them is nowadays, but older schemes made them by applying pressure directly to carbon samples.
Industrial diamond is almost all synthetic. It's produced, more or less, by setting off a bomb on top of carbon powder and diamond dust. The result doesn't look pretty, but is functional.
The semiconductor industry already produces diamond films for a few applications by the same methods they use for other types of film (CVD, etc). You typically don't use buckyballs as the carbon source, as other cheaper chemicals work just as well ("cheap" being relative, as whatever's being used has to be ultra-pure to avoid defects). In practice, diamond-based integrated circuits would be manufactured using techniques like this.
People have been experimenting with diamond-based integrated circuits for a while now. They can operate at much higher temperatures than most other IC technologies, but doping is more difficult (requires much higher dopant concentrations, and there may be other problems).
Diamond MEMS would most logically be produced by methods similar to diamond ICs, to make maximum use of existing technology.
Bah.. If you start producing 20x more ram I bet the price would drop somewhat.
Um, no.
RAM is already produced in such vast quantities that economies of scale won't give you any further benefit. Think for a minute about how much is used yearly.
Take something like a web browser. Given a bit of wizardry (obviously, we need to consider concurrency and critical sections), you could have separate images downloaded and processed by separate processors. Your flash ad would run on another processor.
Web tasks tend not to be processor-bound. You're limited by your 'net connection for these (you can draw an image far faster than you can download it).
It turns out that most of the tasks people do either aren't strong loads on the system at all (e.g. surfing, email, word-processing, spreadsheets) or are limited by some other part of the system (memory bandwidth, disk, or graphics card).
Of the remaining tasks, most aren't easily parallelized (or at least not automatically). Of the ones that are partly parallelizable, the serial part of the task tends to cause bottlenecking, which gives you rapidly-diminishing returns (look up "Amdahl's Law" for a deeper explanation of this).
The only processor-intensive, easily-parallelizable task that's currently done is 3D gaming, and the processing load for that is mainly handled by the video card, not the CPU. Graphics cards already parallelize to some degree on-die, but can't have more than one graphics chip without driving up the price of the card considerably. While this can be (and is) done for high-end cards, consumers prefer cards that are at a sane price.
In short, in the one place where most people would benefit from a multi-chip solution, you won't see it.
Frankly, I'm wondering what's stopping us from using this approach to increasing performance? Is this like the fact that OEMs equip the low-end PCs with too little RAM so that Joe Shmoe will buy a new one as quickly as possible, since he does not know that spending 100 bucks on more RAM will make his computer last another year or two?
Actually, it's that Joe Schmoe *prefers* to buy as cheap a computer as he can get his hands on. This is why you don't see many machines sold with a vast amount of RAM, and why you don't see many dual-processor machines sold.
People apparently really _do_ just want cheap machines, not optimized machines.
And, really, as long as the focus is on the gigahertz, do the chip makers really concentrate on making their designs as efficient as possible?
Yes - if you mean performance-efficient. Being able to say that you kick your competitor's ass in benchmarking does make some difference (especially if games are some of those benchmarks).
There isn't much incentive to be power-efficient beyond the amount needed to keep your chip from melting into slag, for desktops, at least. There are many low-power offerings already used in palmtops and embedded devices.
Power efficiency _is_ an issue, as reasonable power dissipation is the primary limit to a computer's clock rate. However, as long as people are willing to use computers with fans and heatsinks, your desktop processor will dissipate 50W+.
This comes up every time a storage article is posted.
It's shot down every time, but it keeps getting re-posted.
Calculate the cost of the RAM in your computer, per gigabyte. Now, calculate the cost of storage in your hard drive, per gigabyte.
Notice that the difference is several orders of magnitude.
In order for solid state drives to be cheaper than magnetic drives, the cost of pick-your-RAM-flavour has to get a HUNDRED TIMES cheaper, while the cost of hard drives has to NOT get cheaper.
This might happen in the far future if prices drift and keep drifting, but not any time soon.
You can also make a good argument for it being intrinsically cheaper to manufacture hard drive platters than RAM arrays, but this has been beaten to death already.
I'd like to know more about the ones that are just above the brown dwarf level. Could something have terrestrial/Jovian style weather (wind, clouds, hurricanes) and also be fusing inside? That would be cool (hot).
:).
Anything with a convective layer and a heat gradient should have weather, so yes, everything from moons-with-atmospheres on up through full-blown stars should have it.
The convective layer in red dwarfs is much deeper than in more energetic stars like the sun, as they're cooler (convective layer stops when the star material gets hot enough for radiative transmission to be the dominant heat transfer mechanism). Both still have them, though.
Winds and storms should be present aplenty, but clouds are a bit iffy. They should only happen where a phase transition is possible (e.g. from plasma to monatomic gas, and from monatomic gas to molecular gases). This would be right at or near the "surface" of a star (maybe deeper for a red dwarf).
Weather patterns would be very different from conventional weather in layers hot enough to be plasma, as plasma interacts strongly with the star's magnetic field. This region would be anything below a certain depth (i.e. most of the convective layers) and in the corona, for an active star.
Stars are neat
Only your transmitters need to be cheap. If you can build a box and run it out to a few hundred antennas, the home-on-jam devices keep knocking out your antennas. At $500,000 each for an anti-jammer missile and $500 for an antenna and a bit of coax the numbers aren't good.
You'd need an amplifier at the antenna; aggressive jamming requires a bit more power than off the shelf coax will carry. But the idea is good (and in my own reply).
Also keep in mind that some of the cheap spark gap transmitters work great for messing up some types of transmissions and Telsa had lots of cheap devices that will mess with a wide range of spectrum. The reason that the modern military jamers are so expensive is they only want to jam their enemys signals not their own. If your not using radio to such a high level you can just bust the whole spectrum.
The problem is that spread-spectrum communication can tolerate a very high noise floor (hundreds of times higher than the magnitude of the signal in any given spectral range, or more). It manages this by taking advantage of the fact that true noise will cancel a lot of itself out if added across many spectrum areas (or areas of signal space if you're using coding to get spread-spectrum), while the signal just adds constructively to itself. In order to make noise that adds constructively, you have to know the scrambling codes used by the signal you're trying to jam. Otherwise, you have to be far, far louder than the signal you're trying to swamp (do-able, but not with anything small).
Man, I hope they find a lot of good child actors. With the exception of the sixth Sence and the City of Lost Children I have yet to see an excellent job done by a child filling a more adult personality.
Hardly movie-quality, but - the kid who played Picard in the "four people get turned into children" TNG episode did a damned good job.
As pointed our above, you are going to need one hell of a large emitter to make this work. Home-on-jam makes being a large emitter a dangerous (if not fatal) proposition. Your choice then becomes one of jam and die, or don't jam and somebody else dies. The real question is can you produce enough jammers to handle the second or third wave of these things and are the jammers cheaper than the remotes?
:). That's what makes thought experiments like this so much fun.
Excellent points.
If I were designing a jamming system, I'd do a few things to ameliorate (though not eliminate) this problem. The first is to use many medium-sized jamming sources instead of one large one. As long as I can approximately track the target and as long as the source dishes are large enough to allow some direction of the noise beam and as long as I have the infrastructure and logistics support to support the many small stations/deployed jamming units, this should make life much harder for the people launching radio-seeking missiles. It also makes the jammer cost to missile cost ratio a bit more level.
Another option would be to send weather balloons with metal spheres (radio scattering reflectors) into the air around the jamming installation. When an incoming missile is detected, the jammer shuts down and a secondary jammer paints one of the reflectors as a sacrificial target. This would make the cost of the sacrificial target much less than the cost of the missile being fired at it. To make the location of your jammer station less obvious, sacrificial targets could be launched from scattered points some distance away from the jammer (but close enough to be convincing missile decoys).
There are problems with both of these stragegies, and solutions to those problems
Of course, the best solution (hinted at in my previous post) is just to have agents steal the radio codes. This lets you snoop, scramble or usurp them at your discretion with much less effort required. Getting agents' hands on such sensitive information is left as an exercise...
I wonder how effective jamming would be if they took advantage of ultra wide-band/spread spectrum techniques, along with satellite linkages. Seems as though it would be hard to jam that stuff.. all the plane needs to do is look up and use a few gHz of frequencies, and you'd be hard pressed to block that.
Depends on how much effort you're willing to put in the jamming.
Jamming is just sending enough radio noise at the target to make the noise in the desired part of signal space louder than the signal.
For a kid's walkie-talkie, that means dumping noise into a narrow region of spectrum. For frequency-hopping radio, that means dumping noise into many regions of spectrum at once (unless your spies have retrieved the hopping algorithm). For impulse-based UWB, you dump a lot of randomly-timed impulses out (easier if your spies or observations give you approximate timings). For scrambled spread-spectrum radio, you either dump an ungodly amount of noise into the band used to raise the noise floor enough that even coding and correlation don't save you (do-able), or you get your spies to find the family of scrambling codes used and pattern your noise into that band of signal space.
In summary, jamming will always work, either through espionage or through brute force and ignorance.
After looking over the lecture slides a few links in, the authour seems to just be saying that congestion (and hence spectrum scarcity) will be a non-issue if we just switch to point-to-point transciever schemes instead of broadcast schemes (either by using cells and a backbone or by clever coding).
This is great, and would indeed increase bandwidth to silly levels... except for the fact that implementing a pervasive point-to-point network with high local bandwidth and low leakage is a PITA of vast proportions.
Summary: Good idea, and it'll certainly see greater use in the future, but it's not "unlimited airwaves" by a long shot.
The 3d market was 3DFX's to lose.
What killed 3DFX was that their good cards rewuired a 2d card to run. They were 3d only. The Banshee, which did incorporate a 2d core was late and always seemed buggy.
By the time they got their act together with the 3000 series it was too late.
On the contrary, I think their death was post-3000.
The Voodoo 3 went toe to toe with all of the other offerings of its time, at least when it was rolled out. nVidia had a card that could match it, but not beat it.
3dfx dropped the ball when designing a successor to the Voodoo 3. The V4 sank with nary a ripple and the V5 was rushed into release while immature (great idea, immature execution that was made huge and power-hungry to compensate).
It's quite likely that the problems that caused the V5 to tank started even before the V3 days, but the V3 itself was a solid product.