The realism or flight sims and FPS games would be mind boggling. A machine like this would be able to calculate whether a bullet would glance off of a rib and break it or if it would punch straight through. How much blood would be lost, and friction could be calculated to determine how much one would slip on the blood.
I'm not sure about that. The current applications that are being proposed for QC are of a fundamentally different nature. QC speeds up things like searches, but I can't see a way for it to easily speed up things like rendering or kinetics simulations. At the very least, a very different approach to those problems would have to be thought of.
Does anyone else have more information on what kinds of problems quantum computing will and will _not_ be good at?
The speed of light isn't constant, in fact a team at MIT (or somewhere like that) slowed light down to something like 30 Mph (that's Mile per hour!!)
The whole question of "If the speed of light is constant, how come it slows down in things like lenses" stems from the fact that the explanation of refraction given in high school textbooks is much simpler than what is actually going on.
If I remember correctly (it's been a while), what happens when light passes through a transparent medium (like glass or water) is that it interacts with the electrons in the material so as to be briefly absorbed and then re-emitted in the same direction (I may be mangling this - like I said, it's been a while). This kind of interaction is logical when you think about it - a photon is a packet of coupled electric and magnetic fields, while matter is made up of charged particles (electrons and atomic nuclei [small enough to look like points to most photons]).
The net effect of photons being absorbed and re-emitted is that the propagation of the light wave seems to slow down in the material. In actuality, the photons are still travelling at the speed of light in vacuum - they're just not travelling very far before interacting with the matter they're travelling through.
It turns out that a very small fraction of the photons do manage to travel through the material without interacting with anything (though this drops off very sharply with distance). Someone built a device a few years ago that used this effect to take "x-rays" of peoples' hands with visible light (detecting these "ballistic" photons only; their pattern naturally varied depending on how absorbing the materials they passed through were, and was sharp because the photons hadn't scattered off of anything). Check back issues of Scientific American (or possibly Discover) for the reference.
Recent speculation about the speed of light in vacuum not being constant stems from completely different observations, probably celestial.
Also because it's a checksum of all the data between the --Begin PGP and --End PGP lines, if you were to download a copy of Ken's message and change the message in anyway and re-upload it, it would again fail.
Is it an encrypted checksum or cyclic redundancy check code? If it's just a checksum, you can fiddle with the altered message to produce the same sum. It's far more difficult to produce the same CRC code (I think), but which is being used here?
The most secure way that I know of to encode a message to verify that it's from you is to encrypt the whole thing with your private key. The receiver runs it through your public key as if they were sending it as a reply to you, and the plaintext pops out.
OTOH, this requires you to encode the entire message with RSA, which PGP doesn't.
A friend showed me what the Jar Jargonizer did to his web page. It was neat. It occurred to me that this kind of thing could be done very easily with a Perl script, so I wrote one.
Here is a Perl script that with Jar Jar-ify any text fed into it. Because of the way it's set up, it's trivially easy to add more conversions or to modify it into a "borkifier" or any of a wide variety of other translators. If anyone takes offsense at its length, I apologize, but it's on-topic and I don't have a public web page to put it on:).
As has been pointed out by previous posters, the actions of Harvard seem inconsistent with the picture of the situation as given by Ken Williams. There are two possibilities:
Harvard is being really, really stupid.
There is additional information that makes their actions make sense (at least from their point of view).
IMO, the second is more likely. This doesn't mean that we are being misled - just that we have an incomplete view. Can anyone who has emailed Harvard management (or who is within Harvard management), or who is otherwise involved with this, provide more information on what is actually going on?
but in the end, the population grows much faster in third world countries. Which causes lots of other problems, because 3rd world countries are in general much less able to support more people (lack of infrastructure and *food*), and generally lead to a much lower quality of life. Which in turn leads to higher birth rates. So essentially it makes one giant circle! But the people are starting to live longer due to medical advances live in developed countries. So if you add all of these effects together, it means there is a significant population growth, and its likely to keep growing until we run out of space
How so? You yourself point out that the regions in which people are living longer are the regions that have low birth rates, and a _culture_ of few children. There isn't the _transport_ capacity to pull in _billions_ of immigrants - so in the worst possible case, the first world survives (not that that makes overpopulation consequences elsewhere acceptable).
Now, the point about the feedback effect in third world countries holds true. IMO, the best way of breaking this loop is to work on helping the third world build up its infrastructure, and work on making the idea of small families acceptable within large-family cultures. Both are being attempted, and both have shown promising signs. Keep this up for a few decades, and population growth in the third world may look like less of a problem. We'll see what happens.
I'm glad you're quite satisfied with the elegance of the Mozilla architecture. Yet another ringing endorsement of "software engineering", which so far has only succeeded in making projects late.
I guess it depends on what you call "elegance". For me, "elegant" code is primarily code that is cleanly organized and cleanly written. This pays off in spades when you have to revise the code - maintaining bad code is Not Fun (I've had to do it).
Right now the population of the planet isn't dying as fast as it's expanding. This is leading to some massive problems as people live longer. Pretty soon we'll have to start finding other places to put people - or deal with seeing crime rates skyrocket, employment crises, major racially motivated wars, etc... the list goes on.
Firstly, I'd like to take issue with your conclusion. As long as there is physically room for the population, why would more people lead to fewer jobs? On the contrary, it would lead to more jobs, as more people means more _demand_ for goods and services. The number of jobs available per capita should remain the same.
Secondly, I'm not sure that your first point holds true either. Taken as a whole, the population of the earth is indeed growing. However, break this down by region, and you see huge variances. In many places - most notably North America - the population growth rate is either zero or negative, with immigration making up the difference. This is a cultural effect. Cultures in which families have many children will naturally have populations that grow quickly. Cultures where the average number of children that an individual has over the course of their lifetime is two or less have populations that are stable or declining. A longer lifespan would not inevitably lead to a population explosion - it just means that people would have to have children less frequently in order for the population to be stable (the same number of children per person, just over a longer period of time).
Because they simply don't need to bother - the job is already being done. With no compelling reason to do so, they probably won't (inertia is a powerful effect).
I think it is high time the Linux/OSS/*BSD and/. community realize that there probably is a lot of M$ dronez paid to impersonate Linux/*BSD and/. users here on/. and the other Linux OSS sites and newsgroups. The old OS2 guys say this is the same they did to derail OS2. The difference is that now we are orders of a magnitude more and aware of the M$ juggernaut.
While it certainly wouldn't cost Microsoft much to do this, IMO it's not terribly likely. We're perfectly capable of shooting ourselves in the foot without assistance - immature people will exist in any group.
Hey Rob, why not add a feature to have the IP address of the posting host included along with each message next to the score and username? That way if a luser is posting many many flame/troll messages we can easily see them for who they are and ignore them.
This would have the side effect of filtering out posts from good posters who happen to use the same ISP and are handed the same IP number for their session:/.
OTOH, a couple of past cases make me think it might be worth it.
anyone, there is such a thing as a thermal superconductor??
If I understand correctly, electrical semiconductors are also thermal superconductors, though the converse isn't true (thermal superconductors don't have to be electrical superconductors).
I could be mistaken about this, but I've seen references in a couple of places.
Re. thermal superconductors, I remember seeing a reference to "superconductor-like behaviour" being observed at room temperature. I was told that this was thermal superconduction, though I have no way to substantiate this rumour.
Can anyone familiar with the original article pass on what "superconductor-like behavior" means?
The article referenced does not appear to relate to the topic of making chips of any kind in three dimensions.
Also, as was pointed out in the comments, frequency-domain multiplexing of the type described doesn't let you build a computer.
Re. optical computers in general, there are also strong limits on how small you can shrink the feature size on optical devices, as photons will leak through the walls of the waveguides if they are made too small, and your photons will damage the device if you shorten the wavelength too much.
Cooling of the chip helps make the aluminium less resistive. Does this also lower the amount of electromigration?
Yes, it does. At the suggestion of another slashdot reader, I did more research on electromigration, and it actually has a very strong dependence on temperature.
Cooling computers to very low temperatures does solve or at least help a lot of problems, but is impractical for many applications. Heat flow problems will also be significant for chips that generate a lot of heat in very small areas.
There's an easy way to get around the heat issue: redesign so the heat isn't generated in the first place.
I've seen lectures demonstrating solutions for many of the heat issues. At the University of Utah there are research projects (with a bunch of funding from Intel and IBM, where the results are being targetted at production) which tackle the issue of how to use fully asynchronous circuits within a standard CPU, and how to eliminate the refresh of the entire CPU on each clock cycle.
This does indeed help - however, not that much on a well-designed chip.
A lot of the focus of chip optimization nowadays has been on improving scheduling techniques to let programs take full advantage of all of the chip's facilities at any given time. The eventual goal is that if the chip has two FPUs and three integer arithmetic units, it will be performing two FP calculations and three integer calculations per clock, with no units sitting idle. Asynchronous chips give you a large power savings when you _do_ have chip components sitting idle - you are no longer clocking a module that isn't being used. However, for a chip that is using all parts of itself, all components _have_ to be clocked, which limits the savings that you get from making a chip asynchronous.
It's still a worthwhile optimization; it just won't save you from heat problems as clock speeds rise.
On a side note, why don't designers use 3D designs? It just seems like 2D transistor grids aren't the optimum. In 3d, the clock pulse would have a much shorter path to follow, allowing higher clock speeds.
There are two obstacles that I can think of. The first is heat disspiation; heat will have to travel farther through the chip before reaching the surface. This could be ameliorated by putting sheets of thermally conducting material between layers, but this is complicated, and they'd have to be pretty thick (unless they were thermal superconductors; IIRC these exist at room temperature).
The other obstacle is depositing a layer of crystalline silicon to make transistors with. Current wafers are still sliced from single crystals of silicon. However, silicon that is deposited tends to be polycrystalline. This gives it poor electrical properties.
We'd either have to figure out how to grow or place single-crystal layers of silicon on to an outer oxide layer of a chip, or else figure out how to make fast circuitry with polycrystalline silicon.
That having been said, this is an idea that I like very much. It is one of the logical ways of extending chips once linewidth reaches its limits.
I believe Bose-Einstein condinsate and light are the theoretical switch technology that will replace silicon
That would almost certainly be impractical, as your computing device would have to be kept extremely cold (cold enough to make liquid helium look hot).
IMO, most likely better use of silicon at a fixed feature size. You can improve performance by making transistors with a lower threshold voltage (with better-doped silicon or by using another material). You can also boost performance by tweaking the materials used to reduce parasitic capacitance. You could also start developing true multi-layer chips that have more than one layer of transistors, to keep ramping up density (though cost per transistor will level off very quickly and stay constant). More work could also be put into cooling systems that let you clock chips more quickly without having to worry about electromigration. Several other optimizations are probably possible.
Basically, what will happen is that integrated circuits will become a mature technology. Right now they're still in their rapid development stage (think of it as a really long adolesence:)).
This is only one of several limits to feature size, though it is a significant one. Other limits include:
Electromigration
When current flows through a wire, atoms in the wire tend to be dragged along with the current. The current density - current per unit cross-sectional area of the wire - has to be kept below safe limits (dependent on temperature) to prevent this. Faster chips are made by passing the same amount of current through smaller transistors - but this means through smaller wires, too. Electromigration limits how small you can shrink the wires before your chip dies an early death. Copper helps - it is much more resistant to electromigration than aluminum - but it's still a big problem, and will keep getting bigger.
Capacitive coupling
You get capacitive coupling between wires that are close together - signal leaks from one to the other. This is worse for wires that are closer together, and worse for higher frequencies. As chips shrink and are clocked more quickly, capacitive coupling becomes an ever-greater problem. Capacitive coupling also causes signal leakage between the various parts of a transistor, as well as between transistor sources/drains and the substrate (though silicon-on-insulator helps eliminate this last effect).
Heat Generation
A chip's total parasitic capacitance doesn't depend that much on the size of its transistors; just on its total area. Charging and discharging this capacitance dissipates a certain amount of energy (dependent on the chip voltage). As chips are clocked more quickly, power dissipation goes up in proportion to the clock speed. Reducing the core voltage helps a bit, but the core voltage must always be considerably higher than the transistor threshold voltage. Silicon-on-insulator lowers the total parasitic capacitance, but only to a certain point. The problem remains.
This list completely ignores fabrication difficulties at finer linewidths, though those look like they're tractable. However, electrical problems will still pose limits to how small you can shrink features on a chip. When exactly these limits will come into play remains to be seen, but they are lurking.
Agreed, water is a pretty good absorber of EMR at 2.45GHz, but this isn't due to "resonance" in any conventional sense. The microwaves couple pretty well to water molecules due to the molecules' polar nature (one side is electrically negative relative to the other). They vibrate quite strongly as a result, resulting in heat.
This isn't what I was talking about - in _addition_ to this effect, there are absorption bands specifically in this region due to quantization of angular momentum of the water molecule. Whether it should be called "resonance" or not depends on how you choose to explain absorption spectra to the layman. Click on "user info" above to find the post where I go over this in detail.
How many postings are going to erroneously claim that microwave ovens operate at "the resonance frequency of water?"
See my previous post. The absorption bands for rotational energy levels in water are in the microwave range. Microwave operating frequency is subject to legislation, but why do you think that band works so well in the first place?
Water will absorb at other frequencies too, but this just happens to be a fairly good one.
Most old analog cell phones operate at 800 MHz. Handheld analog cell phones are dangerous because they operate at one watt. That may not sound like much, but absorbed power is proportional to the inverse cube of distance... so your brain is absorbing a decent percentage of that one watt a centimeter or two away.
It's inverse square, and for heating at least, it still wouldn't make a difference. One watt (or 0.5 watts) is a miniscule amount of power. It takes 4 joules of energy to heat one gram of water one degree. Your microwaves will be heating up somewhere between a hundred and a thousand grams of water-based tissue over the region in which they are being absorbed (about a fifth of a pound to two pounds, for those not into metric). This gives you a temperature change of at most a few thousanths of a degree per second. Your body has a good cooling system - the circulatory system. This heat will be taken away as quickly as it is generated.
Of more significant concern is the question of strong absorption of microwaves due to rotational and other energy bands in proteins and DNA, but this is unlikely to do much, for reasons that I mentioned in another post. Your DNA molecule would have to vibrate one heck of a lot for the vibrational energy to overcome the energy of the chemical bonds in the DNA. Your DNA molecule is also sitting in a water bath, and water's a lot more viscous on that small a scale. Rotational and vibrational energy will be almost immediately transferred to the surrounding water and dissipated as heat.
I can't prove that there is _no_ danger from cell phones, but IMO it's more likely to come from solvents in the plastic - or talking while driving one-handed - than from EMF.
3) The 'resonant frequency' of a single molecule would be somewhere in the gamma-ray portion of the electromagnetic spectrum.
Completely incorrect, I'm afraid, as another poster has pointed out. Several effects cause absorption lines for molecules:
Electron shell energy levels
These cause absorption lines in the visible to UV range, as the energy of these photons corresponds to the difference in binding energy of the electrons in the outer shells of the atoms/molecules in question. Deep inner-shell transitions produce X-ray lines, usually seen in emission spectra as opposed to absorption spectra.
Vibrational resonance modes
A molecule's shape isn't fixed - it can vibrate, as if the atoms were connected by springs. The energy levels of these vibrations are quantized, and the difference in energy levels here generates absorption lines in the IR spectrum. This is what lets you use CO2 to generate infrared in a CO2 laser.
Rotational energy levels
Finally, a molecule's angular momentum is quantized - it can't rotate at any speed it feels like, but must rotate at a speed that is a multiple of a given quantity. This gives you a set of energy levels with differences that generate absorption lines in the microwave spectrum. Chemical-based masers take advantage of this to produce coherent microwave beams using media like ammonia (IIRC). It is this set of absorption bands that the previous poster was referring to.
As far as gamma rays are concerned, they correspond to energy level differences in the _nuclei_ of atoms. The energies involved are almost always far greater than the energy differences even in inner electron shells, which is why the gamma ray portion of the spectrum is higher than the x-ray portion.
As far as microwave absorption doing damage is concerned, I am skeptical because the bond strength in molecules is much greater than the energy of the microwaves. Even if a microwave beam was exactly tuned to one of the absorption bands of - say - DNA, the DNA would dissipate kinetic energy by interaction with the water and other chemicals around it. I doubt that it would come even within orders of magnitude of levels that could cause mechanical breakage.
IMO, further study would be wise before trying to ban all cell phones based on inconclusive studies.
What's to stop these guys from sapping small amounts of power directly from the wires themselves? Use the small amount of juice to run around or to charge batteries?
Mainly, the insulation on the wires:).
They could try getting power from the EM radiation given off by the wires, but wires carrying significant amouns of power are usually configured to minimize EMF, as it represents wasted power.
They could run bare wires as power rails for the robots, but that partially defeats the purpose of having the robots in the first place, by limiting their range. It could be done, but IMO if they were going to put in that much effort they'd be better off using other approaches.
Slashdot Mirror
I'm not sure about that. The current applications that are being proposed for QC are of a fundamentally different nature. QC speeds up things like searches, but I can't see a way for it to easily speed up things like rendering or kinetics simulations. At the very least, a very different approach to those problems would have to be thought of.
Does anyone else have more information on what kinds of problems quantum computing will and will _not_ be good at?
The whole question of "If the speed of light is constant, how come it slows down in things like lenses" stems from the fact that the explanation of refraction given in high school textbooks is much simpler than what is actually going on.
If I remember correctly (it's been a while), what happens when light passes through a transparent medium (like glass or water) is that it interacts with the electrons in the material so as to be briefly absorbed and then re-emitted in the same direction (I may be mangling this - like I said, it's been a while). This kind of interaction is logical when you think about it - a photon is a packet of coupled electric and magnetic fields, while matter is made up of charged particles (electrons and atomic nuclei [small enough to look like points to most photons]).
The net effect of photons being absorbed and re-emitted is that the propagation of the light wave seems to slow down in the material. In actuality, the photons are still travelling at the speed of light in vacuum - they're just not travelling very far before interacting with the matter they're travelling through.
It turns out that a very small fraction of the photons do manage to travel through the material without interacting with anything (though this drops off very sharply with distance). Someone built a device a few years ago that used this effect to take "x-rays" of peoples' hands with visible light (detecting these "ballistic" photons only; their pattern naturally varied depending on how absorbing the materials they passed through were, and was sharp because the photons hadn't scattered off of anything). Check back issues of Scientific American (or possibly Discover) for the reference.
Recent speculation about the speed of light in vacuum not being constant stems from completely different observations, probably celestial.
Is it an encrypted checksum or cyclic redundancy check code? If it's just a checksum, you can fiddle with the altered message to produce the same sum. It's far more difficult to produce the same CRC code (I think), but which is being used here?
The most secure way that I know of to encode a message to verify that it's from you is to encrypt the whole thing with your private key. The receiver runs it through your public key as if they were sending it as a reply to you, and the plaintext pops out.
OTOH, this requires you to encode the entire message with RSA, which PGP doesn't.
Here is a Perl script that with Jar Jar-ify any text fed into it. Because of the way it's set up, it's trivially easy to add more conversions or to modify it into a "borkifier" or any of a wide variety of other translators. If anyone takes offsense at its length, I apologize, but it's on-topic and I don't have a public web page to put it on
jarjar.pl
# Define the substitutions to be performed.
@WordList =
(
"I'm", "meesa be",
"I", "meesa",
"me", "meesa",
"you", "you-sa",
"my", "meesa's",
"your", "you-sa's",
"myself", "meesa's self",
"yourself", "you-sa's self",
"am", "be"
);
@SuffixList =
(
"ing", "\'in",
"er", "-a"
);
@PrefixList =
(
);
# Perform the substitutions on each line of input.
while ($Input = )
{
# Replace whole words.
for ($Index = 0; $WordList[$Index]; $Index += 2)
{
$Input =~
s/(^|\W)$WordList[$Index](\W|$)/$1$WordList[$Inde
}
# Replace suffixes.
for ($Index = 0; $SuffixList[$Index]; $Index += 2)
{
$Input =~
s/(\w)$SuffixList[$Index](\W|$)/$1$SuffixList[$In
}
# Replace prefixes.
for ($Index = 0; $PrefixList[$Index]; $Index += 2)
{
$Input =~
s/(^|\W)$PrefixList[$Index](\w)/$1$PrefixList[$In
}
# Print the modified line.
print $Input;
}
IMO, the second is more likely. This doesn't mean that we are being misled - just that we have an incomplete view. Can anyone who has emailed Harvard management (or who is within Harvard management), or who is otherwise involved with this, provide more information on what is actually going on?
How so? You yourself point out that the regions in which people are living longer are the regions that have low birth rates, and a _culture_ of few children. There isn't the _transport_ capacity to pull in _billions_ of immigrants - so in the worst possible case, the first world survives (not that that makes overpopulation consequences elsewhere acceptable).
Now, the point about the feedback effect in third world countries holds true. IMO, the best way of breaking this loop is to work on helping the third world build up its infrastructure, and work on making the idea of small families acceptable within large-family cultures. Both are being attempted, and both have shown promising signs. Keep this up for a few decades, and population growth in the third world may look like less of a problem. We'll see what happens.
I guess it depends on what you call "elegance". For me, "elegant" code is primarily code that is cleanly organized and cleanly written. This pays off in spades when you have to revise the code - maintaining bad code is Not Fun (I've had to do it).
Firstly, I'd like to take issue with your conclusion. As long as there is physically room for the population, why would more people lead to fewer jobs? On the contrary, it would lead to more jobs, as more people means more _demand_ for goods and services. The number of jobs available per capita should remain the same.
Secondly, I'm not sure that your first point holds true either. Taken as a whole, the population of the earth is indeed growing. However, break this down by region, and you see huge variances. In many places - most notably North America - the population growth rate is either zero or negative, with immigration making up the difference. This is a cultural effect. Cultures in which families have many children will naturally have populations that grow quickly. Cultures where the average number of children that an individual has over the course of their lifetime is two or less have populations that are stable or declining. A longer lifespan would not inevitably lead to a population explosion - it just means that people would have to have children less frequently in order for the population to be stable (the same number of children per person, just over a longer period of time).
Because they simply don't need to bother - the job is already being done. With no compelling reason to do so, they probably won't (inertia is a powerful effect).
While it certainly wouldn't cost Microsoft much to do this, IMO it's not terribly likely. We're perfectly capable of shooting ourselves in the foot without assistance - immature people will exist in any group.
This would have the side effect of filtering out posts from good posters who happen to use the same ISP and are handed the same IP number for their session
OTOH, a couple of past cases make me think it might be worth it.
If I understand correctly, electrical semiconductors are also thermal superconductors, though the converse isn't true (thermal superconductors don't have to be electrical superconductors).
I could be mistaken about this, but I've seen references in a couple of places.
Re. thermal superconductors, I remember seeing a reference to "superconductor-like behaviour" being observed at room temperature. I was told that this was thermal superconduction, though I have no way to substantiate this rumour.
Can anyone familiar with the original article pass on what "superconductor-like behavior" means?
does that answer the question?
The article referenced does not appear to relate to the topic of making chips of any kind in three dimensions.
Also, as was pointed out in the comments, frequency-domain multiplexing of the type described doesn't let you build a computer.
Re. optical computers in general, there are also strong limits on how small you can shrink the feature size on optical devices, as photons will leak through the walls of the waveguides if they are made too small, and your photons will damage the device if you shorten the wavelength too much.
Yes, it does. At the suggestion of another slashdot reader, I did more research on electromigration, and it actually has a very strong dependence on temperature.
Cooling computers to very low temperatures does solve or at least help a lot of problems, but is impractical for many applications. Heat flow problems will also be significant for chips that generate a lot of heat in very small areas.
I've seen lectures demonstrating solutions for many of the heat issues. At the University of Utah there are research projects (with a bunch of funding from Intel and IBM, where the results are being targetted at production) which tackle the issue of how to use fully asynchronous circuits within a standard CPU, and how to eliminate the refresh of the entire CPU on each clock cycle.
This does indeed help - however, not that much on a well-designed chip.
A lot of the focus of chip optimization nowadays has been on improving scheduling techniques to let programs take full advantage of all of the chip's facilities at any given time. The eventual goal is that if the chip has two FPUs and three integer arithmetic units, it will be performing two FP calculations and three integer calculations per clock, with no units sitting idle. Asynchronous chips give you a large power savings when you _do_ have chip components sitting idle - you are no longer clocking a module that isn't being used. However, for a chip that is using all parts of itself, all components _have_ to be clocked, which limits the savings that you get from making a chip asynchronous.
It's still a worthwhile optimization; it just won't save you from heat problems as clock speeds rise.
There are two obstacles that I can think of. The first is heat disspiation; heat will have to travel farther through the chip before reaching the surface. This could be ameliorated by putting sheets of thermally conducting material between layers, but this is complicated, and they'd have to be pretty thick (unless they were thermal superconductors; IIRC these exist at room temperature).
The other obstacle is depositing a layer of crystalline silicon to make transistors with. Current wafers are still sliced from single crystals of silicon. However, silicon that is deposited tends to be polycrystalline. This gives it poor electrical properties.
We'd either have to figure out how to grow or place single-crystal layers of silicon on to an outer oxide layer of a chip, or else figure out how to make fast circuitry with polycrystalline silicon.
That having been said, this is an idea that I like very much. It is one of the logical ways of extending chips once linewidth reaches its limits.
That would almost certainly be impractical, as your computing device would have to be kept extremely cold (cold enough to make liquid helium look hot).
IMO, most likely better use of silicon at a fixed feature size. You can improve performance by making transistors with a lower threshold voltage (with better-doped silicon or by using another material). You can also boost performance by tweaking the materials used to reduce parasitic capacitance. You could also start developing true multi-layer chips that have more than one layer of transistors, to keep ramping up density (though cost per transistor will level off very quickly and stay constant). More work could also be put into cooling systems that let you clock chips more quickly without having to worry about electromigration. Several other optimizations are probably possible.
Basically, what will happen is that integrated circuits will become a mature technology. Right now they're still in their rapid development stage (think of it as a really long adolesence
When current flows through a wire, atoms in the wire tend to be dragged along with the current. The current density - current per unit cross-sectional area of the wire - has to be kept below safe limits (dependent on temperature) to prevent this. Faster chips are made by passing the same amount of current through smaller transistors - but this means through smaller wires, too. Electromigration limits how small you can shrink the wires before your chip dies an early death. Copper helps - it is much more resistant to electromigration than aluminum - but it's still a big problem, and will keep getting bigger.
You get capacitive coupling between wires that are close together - signal leaks from one to the other. This is worse for wires that are closer together, and worse for higher frequencies. As chips shrink and are clocked more quickly, capacitive coupling becomes an ever-greater problem. Capacitive coupling also causes signal leakage between the various parts of a transistor, as well as between transistor sources/drains and the substrate (though silicon-on-insulator helps eliminate this last effect).
A chip's total parasitic capacitance doesn't depend that much on the size of its transistors; just on its total area. Charging and discharging this capacitance dissipates a certain amount of energy (dependent on the chip voltage). As chips are clocked more quickly, power dissipation goes up in proportion to the clock speed. Reducing the core voltage helps a bit, but the core voltage must always be considerably higher than the transistor threshold voltage. Silicon-on-insulator lowers the total parasitic capacitance, but only to a certain point. The problem remains.
This list completely ignores fabrication difficulties at finer linewidths, though those look like they're tractable. However, electrical problems will still pose limits to how small you can shrink features on a chip. When exactly these limits will come into play remains to be seen, but they are lurking.
This isn't what I was talking about - in _addition_ to this effect, there are absorption bands specifically in this region due to quantization of angular momentum of the water molecule. Whether it should be called "resonance" or not depends on how you choose to explain absorption spectra to the layman. Click on "user info" above to find the post where I go over this in detail.
Alpha has been making extremely fast chips for years. Look up their old roadmaps and check the clock speeds.
Not that clock speed means a whole lot. However, Alpha's spec numbers have been impressive too.
See my previous post. The absorption bands for rotational energy levels in water are in the microwave range. Microwave operating frequency is subject to legislation, but why do you think that band works so well in the first place?
Water will absorb at other frequencies too, but this just happens to be a fairly good one.
It's inverse square, and for heating at least, it still wouldn't make a difference. One watt (or 0.5 watts) is a miniscule amount of power. It takes 4 joules of energy to heat one gram of water one degree. Your microwaves will be heating up somewhere between a hundred and a thousand grams of water-based tissue over the region in which they are being absorbed (about a fifth of a pound to two pounds, for those not into metric). This gives you a temperature change of at most a few thousanths of a degree per second. Your body has a good cooling system - the circulatory system. This heat will be taken away as quickly as it is generated.
Of more significant concern is the question of strong absorption of microwaves due to rotational and other energy bands in proteins and DNA, but this is unlikely to do much, for reasons that I mentioned in another post. Your DNA molecule would have to vibrate one heck of a lot for the vibrational energy to overcome the energy of the chemical bonds in the DNA. Your DNA molecule is also sitting in a water bath, and water's a lot more viscous on that small a scale. Rotational and vibrational energy will be almost immediately transferred to the surrounding water and dissipated as heat.
I can't prove that there is _no_ danger from cell phones, but IMO it's more likely to come from solvents in the plastic - or talking while driving one-handed - than from EMF.
Completely incorrect, I'm afraid, as another poster has pointed out. Several effects cause absorption lines for molecules:
These cause absorption lines in the visible to UV range, as the energy of these photons corresponds to the difference in binding energy of the electrons in the outer shells of the atoms/molecules in question. Deep inner-shell transitions produce X-ray lines, usually seen in emission spectra as opposed to absorption spectra.
A molecule's shape isn't fixed - it can vibrate, as if the atoms were connected by springs. The energy levels of these vibrations are quantized, and the difference in energy levels here generates absorption lines in the IR spectrum. This is what lets you use CO2 to generate infrared in a CO2 laser.
Rotational energy levels
Finally, a molecule's angular momentum is quantized - it can't rotate at any speed it feels like, but must rotate at a speed that is a multiple of a given quantity. This gives you a set of energy levels with differences that generate absorption lines in the microwave spectrum. Chemical-based masers take advantage of this to produce coherent microwave beams using media like ammonia (IIRC). It is this set of absorption bands that the previous poster was referring to.
As far as gamma rays are concerned, they correspond to energy level differences in the _nuclei_ of atoms. The energies involved are almost always far greater than the energy differences even in inner electron shells, which is why the gamma ray portion of the spectrum is higher than the x-ray portion.
As far as microwave absorption doing damage is concerned, I am skeptical because the bond strength in molecules is much greater than the energy of the microwaves. Even if a microwave beam was exactly tuned to one of the absorption bands of - say - DNA, the DNA would dissipate kinetic energy by interaction with the water and other chemicals around it. I doubt that it would come even within orders of magnitude of levels that could cause mechanical breakage.
IMO, further study would be wise before trying to ban all cell phones based on inconclusive studies.
Mainly, the insulation on the wires
They could try getting power from the EM radiation given off by the wires, but wires carrying significant amouns of power are usually configured to minimize EMF, as it represents wasted power.
They could run bare wires as power rails for the robots, but that partially defeats the purpose of having the robots in the first place, by limiting their range. It could be done, but IMO if they were going to put in that much effort they'd be better off using other approaches.
An interesting thought, though.