This is great news. The Hubble is one of our greatest scientific instruments. Without it or a suitable replacement, the effort to learn more about the universe would be left flapping around like a fish out of water.
Not really.
The Hubble is one out of many scientific satellites. It gets a lot of press because it cost a lot to build, and works in wavelengths that give the press pretty pictures.
There are some things the HST can do that other ground- and space-based telescopes can't (mostly due to atmospheric absorption on some wavelengths), but to say that study of the cosmos would be crippled by loss of the Hubble is silly. "Inconvenienced" is a more accurate term.
I imagine you could do the same with any magnetic card and a little fine iron sawdust that you could make yourself with a grinder.
You're working too hard. www.sci-toys.com mentions that the easiest way for a person to get iron filings is to drag a magnet through the sand at a beach.
Your particle size has to be finer than the size of the domains you're trying to look at. As another posted noted, standard magstripe cards work with domain sizes of about 5-10 mil, and the tapes mentioned by other posters have even finer domain sizes.
When I was a kid sifting magnetite out of sand for fun, typical grain size was much larger.
That's why you should never put scientists up on a pedestal like they are so unquestionable or let them tell you that their crappy theories are truth just becuase "you can't understand it".
Any scientist that tells you something is "true" has a mountain of evidence to back him or her up.
Understand the theories, _then_ criticize. Most of these kinds of objection I've heard have come from people who either took the dumbed-down high school version as gospel, or who just plain don't understand the field being discussed.
Science doesn't know everything. Any good scientist knows the limits of scientific knowledge in their field. All or nearly all models of reality that science has constructed have areas where they don't apply well, as most of these are simpler approximations to very complex systems. But to use this to say that scientists are talking vapour about the areas where they _do_ apply well is extremely foolish.
The progress of science over the past couple of centuries has not generally been to overturn old theories and models, but to extend scientific knowledge to cover cases where the old models didn't apply. When a new model is proposed, it almost always turns out that it reduces to the old model in domains that the old model was designed to address. This is why Newton's laws of motion still hold, and why you don't need special relativity to find kinetic energy of slow-moving objects, and why general relativity still gives you Kepler orbits and Newton's laws of gravitation in weak gravitational fields, and why you don't need to solve quantum electrodynamics equations to find out how strong an electromagnet is.
In this light, I find it amusing that you use Newton's works as a supporting example for ignoring scientists' statements when we still use his laws of motion and gravitation for engineering today.
At what point are people actually going to start making 64 bit applications? I'm not talking 64 bit linux or anything like that, I'm talking consumer level apps and games.
Among other things, it should let the OS map more than a few gigabytes of memory into the address space at one time. A 32-bit application will only be able to see 4 gigabytes (or 2, or whatever the limit ends up being after tag bits and OS space are reserved), but the total amount in use can be more, without an application rewrite needed. This is already done to some extent (my understanding is that the 32-bit processors have 36 bits of address space in total, with a 32-bit per process maximum), but moving to 64 bits gives a lot more headroom.
I see a lot of people upgrading to 64 bit chips, but what good does it do if there's nothing to utilize them? Is it just for bragging rights or what?
I'm a programmer and I have yet to see a need to get a 64 bit chip.
It's handy to have native handling of things like 64-bit integers, but addressable memory space is the most pressing reason right now. You'll be able to mmap() a file larger than 2 gigabytes on x86-64 machines (where up to now you had to use a non-x86 platform). You'll be able to hold more than 2 gigabytes of working data in RAM, which is significant if you're doing video editing (or heavy rendering or really heavy image processing).
Consumer apps and games will move into this niche in a few years (there are algorithms that let you trade off memory footprint and speed, and memory is cheap). But there are several places where the ability to address more memory is important _now_, even for user workstations.
Architecutre-wise, its still easier to write an emulator for [on] the PPC than for [on] the IA-32.
Part of the point of my previous post is that this fact a) means quite little when comparing the relative capabilities of the two processors, and b) is being used to make some rather silly claims in this thread. Both are good processors, and both have enthusiasts with more zeal than sense ready to bash the competition.
What do you think is easier to emulate? A low-register-count CPU on a high-register-count CPU, or vice versa?
Emulating a machine with many registers on a machine with few registers will cause spills to memory, which indeed slows things down, but there are other aspects of architecture which will slow things down far more. The x86 architecture is a crawling horror, full of operations with complex side effects and wierd idiosyncracies that are holdovers from bygone eras. I'm told that the PPC line has its own demons to worry about in this regard, before any of the Mac crowd start pointing fingers. Trying to emulate a crawling horror of an architecture requires a large amount of special-casing and time-consuming state tweaking after most operations, or else requires assuming that certain side effects won't be used most of the time and producing an emulator that only *mostly* supports the relevant code, or else requires a cross-compiler with the near-omniscience required to determine for all cases where features are needed, and produce code that does exactly what's needed and nothing more. My understanding is that it's the last approach that's used by modern emulators (with optimization thrown in for giggles), but it's far from perfect, and there is still substantial overhead both in execution time and program memory footprint (which causes extra I-cache stress, slowing things down even more).
In summary, the PPC will still have a hard time emulating an x86, and register count on the x86 is the least of its problems when trying to emulate a PPC.
Endianness is its own can of worms. You can relatively easily tweak endianness of code and immediate values during cross-compilation, but any memory buffers have to be munged at *run* time (because you don't know if the program treats them as being composed of 8-, 16-, 32-, or 64-bit elements, or all of the above). If the latest PPC chip doesn't support this in hardware, emulation becomes a tar-pit.
Anyways, this is why I'm cynically amused by all of these "My 3mul4tor can k1ck y0ur 3mul4tor's 4ss!" posts. And yes, IAACompEng.
You've obviously no clue. Go do your homework. A PPC can emulate a Pentium of roughly the same clock speed without any trouble via VPC right now, whereas a Pentium can emulate a PPC at about a tench of its own speed, in theory, and more like 1/100th of the clockspeed using the emulators that currently exist.
I realize that asking for actual evidence from either side here is futile, but:
- Download SPEC benchmarks. - Make them go on PPC machine natively with default and tweaked compiler options. - Make them go on P4 natively with default and tweaked compiler options. Use MSVC/Windows and gcc/*nix, for a good spread - gcc's optimization was Not Good last time I checked. MSVC's was. - Make the same P4 binaries go under VPC.
The results will probably be enlightening for both of you. I am deeply skeptical of *any* emuation being as fast as the real thing for code that's already optimized (i.e. won't benefit from emulator re-optimization).
You'll also be memory-bound on both machines for several types of task (same speed on both systems), clock-speed bound for several other types of task (favours the P4), register-bound on others (favours the PPC), and cache-bound on yet more (varies by machine configuration).
Apple's been reluctant to post SPEC numbers for a while now, so feel free to settle the issue with real benchmarks instead of a photoshop or emulator DSW.
Depends on the university. About 10-20 years ago, this was true. Right now, around here at least you have EE, CS, and CE as distinct disciplines:
EE deals with mostly analog systems, and mostly systems build from discrete components (e.g. power systems, high power RF systems, control for industrial systems, etc.).
CS deals with information theory and theory of computation. These are the people who design new programming languages and work on AI and so forth.
CE deals with highly-integrated electronics, and the software written to drive it. Focus is more on digital circuits than EE, and more on existing coding techniques for existing or nearly-existing devices than CS.
At least, that's what it was like when I went through. The flavour of the CE program, and much of its curriculum, will depend on whether it grew out of the EE department, the CS department, or both at the university in question. Likewise, the nature of the EE and CS departments will change depending on how much they offload to CE (EE at a school without a CE department will have a lot more CE material, for instance).
I can't point you towards physics references, but I can point you towards texts about modelling and using these devices:
Microelectronic Circuits, by Sedra and Smith. This is the semiconductor devices bible for electrical and computer engineering (in North America, at least).
Analog Integrated Circuit Design, by Johns and Martin. Excellent book recapping device behavior and describing analog circuits and the issues that come up when you're trying to integrate elements on a die.
Principles of CMOS VLSI Design, by West, Eshraghian, and Smith. This also covers layout and circuit issues, though mostly for digital logic design.
If you want to do digital logic intelligently, or design analog circuits that do their job with precision and effectiveness, you need to go back to school and get a Comp Eng degree. If you want an idea of how engineers use the devices you're trying to optimize, and what factors are important for usability and performance, these books will do.
2.Not as safe - there STILL isn't enough AI computing power to control the traffic and fly the masses safely through the 3D "skyways".
It's not a computing power problem - it's a reliability problem. The computer on your desk has enough number-crunching ability to direct a city's traffic in 2D or 3D in real-time, especially if a simpler sub-optimal-but-good-enough algorithm is used.
The real problem with automatically controlled cars is that the system won't be perfect, and the consequences of failure either on the ground or in the air aren't acceptable. On the ground, your automated vehicle kills a pedestrian (because of vehicle control failure or because they did something foolish). In the air, a malfunction turns your vehicle into a few thousand pounds of flying metal (plus fuel!) looking for something fragile to crash down on.
The 2D case gives you prohibitive liability problems for the manufacturer, and the 3D case gives you accidents that are far less survivable and produce far more collateral damage than the 2D kind. All of these problems are solvable, and I firmly believe we'll end up with computer-controlled ground cars in the not too distant future, but it won't be a cakewalk.
Maybe the idiots in the 50s really did think that anyone who could drivecould surely be a pilot too?
That was the general idea, if I understand correctly. After all, how much harder can it be? (/irony)
The problem is that the sensitivity of the current detectors does not allow to determine wether these has a mass and travel a little less than the speed of light or if they are massless. Neutrinos with mass can resolve the dark energy problem.
Actually, it's the dark _matter_ problem massive neutrinos address, and they only form part of the puzzle ("hot dark matter").
Dark _energy_ appears to be a repulsive force intrinsic to space. This proposed model is one take on a mechanism for it.
Neutrino mass has also been pretty conclusively demonstrated by observations of neutrino _oscillation_ (changing of flavour), which cannot occur if neutrinos are massless. This incidentally also solves the solar neutrino problem (the detectors producing shortfall measurements could only detect one type of neutrino, while solar neutrinos were oscillating between all three types in transit, resulting in many not being detected).
Most of these developments happened within the last decade or so. We're in a very interesting time for particle physics (between new observations, new mathematical approaches to applying string theory, and new approaches to modelling gravity that aren't string theory).
Also included is the coordinates of a particular black hole; when each species gets bored of kicking around with no one to talk to, it departs for a near-event horizon orbit around the black hole, where it waits, along with the other early races, for the galaxy to fill up with interesting people.
This is actually a pretty choice piece of real-estate. If you're close enough to the hole, you can draw power from either the microwave background or (later) the hole, until an incredibly distant time in the future (long after all other sources of power have been exhausted).
I'm going to have to look up that David Brin anthology:).
Our planet emits enough radio energy to look like a small sun, but it hasn't done so for very long. Some scientists believe that it won't continue at the present level, either, because future requirements will demand higher-capacity transmissions -- radio transmission will fall off in favor of something that's more tightly-focused, in other words.
I find this unlikely. After all, we didn't stop using AM and FM radio when compact microwave transcievers became available, despite having much higher bandwidth available.
Beamed systems or phased arrays being used for point to point will reduce the amount of easily interpreted radiation, but all that means is that an advanced radio-using civilization will just look like a noise-emitter.
I'd actually put this as the main stumbling block to identifying ET civilizations - we may not be able to easily distinguish artificial radio sources from natural ones.
I don't understand your first assertion. One half of a number is not the same as its square root. Even a key length of nine, the square root is 1/3 the key length. For a 100-digit key, the square root is a tenth. Please explain how this "halves" the key size.
A key with 1024 bits has 2^1024 possible values. A key with 2048 bits has 2^2048 possible values. The square root of 2^2048 is 2^1024.
A classical computer brute-force searching a 2048-bit key value requires 2^2048 tests. A quantum computer requires only sqrt(2^2048), which is (2^1024) - the number of operations a classical computer would require to brute-force a key of half the length (1024 bits).
I hope this clears up your question.
I'm not a cryptographer, but I think the advantage of using a quantum computer *is* the fact that it can do a brute-force search exponentially faster than today's hardware.
It can't, in any scheme where you have to actually get data back out of the quantum computer.
Whenever you observe the state, it collapses to a specific value. You have to do a number of tests on the same computation result to get an idea of what the probability distribution is. This takes enough operations to produce the "square root" figure quoted. You only get better than that if the algorithm you're trying to reverse lends itself specifically to a quantum implementation (like Shor's algorithm for factoring).
Someone more heavily into QC can give you a more detailed description of how this works.
In fact, all you have to do is double the key size (in bits) on something like RSA to make it just as hard to break
Bad example:).
While this is true for any case where you're stuck doing a brute-force search, in the case of RSA there's a very, very fast algorithm for reversing the trapdoor function it uses (Shor's Algorithm, which factors the public key in far better than exponential time).
Using a quantum computer it can search every possible key simultaneously, cracking the encryption almost instantly.
My understanding was that this is not true. At best you get the square root of the number of steps that would be required for a non-quantum brute force search. This means that key sizes are effectively halved, but that isn't an insurmountable problem.
A bigger problem is that some algorithms are intrinsically vulnerable to quantum computing (or to rephrase, take far, far fewer steps to reverse on a quantum computer than a classical one). Factoring is one such case, which is why quantum computing spells the death of RSA. Most other algorithms are relatively safe, if I understand correctly (or at least, have no known quantum computing cracking method beyond brute force; this may change, unless they're _proven_ to have no other cracking method).
In summary, quantum computing is powerful, but not a magic wand that makes all classical encryption schemes invalid.
There are a lot of companies who will do small runs of PC boards for you, but you have to give them finished layouts (gerber files). This gut provides the tools to do the layout as well as doing the boards, so it saves you a huge investment in software and learning a layout system.
Check Freshmeat for "circuit board", and you will find many CAD programs that don't involve large financial outlays. I use PCB, myself.
There's still a learning curve for the interface, but the time spent learning it is much less than the time spent actually designing boards.
You have to be careful about the Uncanny Valley, though, at least according to a particular Japanese roboticist. Apparently once you get within a certain closeness of anthropomorphism, small things which aren't "quite right" can really freak people out.
This is especially apropos given the photos of this particular robot. Pale white face, black orbs for eyes, bright red lips, with vertical lines for guide tracks - they'd have a hard time making it look more vampiric if they tried:).
The Furby also bothered me for the first few days I had it. It was eerily lifelike, and the fact that I was seeing lifelike responses from something I was mentally filing it as an "object" was quite disturbing until I got used to it.
The actual clay... meaning you still have to have clay?
Yes. The whole point of this experiment is to produce better models of soft substances so that they can be used with _other_ types of interface realistically. The glove itself has no feedback characteristics - it's just a measuring device, telling the host computer what happens when you press *this* hard in *that* direction on the target substance (which among other things requires it to build an internal picture of what the current shape of the clay blob is).
Actually, has anyone every detected a black hole that wasn't gobbling up matter from a nearby source (e.g. a star). A lone black hole travelling in the void. Has anyone found such a beast?
Not yet, to the best of my knowledge.
This is part of what gravitational microlensing surveys look for, though the primary targets are objects like brown dwarfs. High-mass objects like non-paired white dwarfs, neutron stars, and black holes should stick out like a sore thumb if they're present.
So far, most of the above that we know about are from other measurements (wobble and accretion disks in paired systems, and radio from rotating neutron stars that happen to be lined up nicely with us). Microlensing events are fairly rare and pretty picky to detect.
Games like this get hyped for so long, and the pre-order BS get's pushed down your throat everytime you step into a GameStop, that it seems no game is sold on merit anymore.
Meanwhile, some of us actually have the patience to wait a week and wait for word of mouth (or see it played at a friend's place) before buying.
There will always be more than enough early adopters and/or people with more money than sense to be able to preview _any_ game like this without a demo.
You're a dumbass. The metal is reactive in air. Calculate the difference in mass and tell me how many freaking times you'd have to use your little centrifuge trick to get the purity you need? Never mind the plumbing problems?
First of all, you're separating a compound of the substance, not raw metal. In the Oak Ridge plant, they used uranium hexafluoride. Still nasty, but won't burst into flame on contact with air (it's already effectively been "burned" with fluorine).
Second of all, the Oak Ridge plant used effusion membranes as a separation method, not centrifuges.
Third of all, you're both being silly. The mass-based separation methods are fairly straightforward - not much beyond undergrad science needed to come up with them. _Implementing_ them was a huge engineering challenge, a highly non-trivial effort. Implementing them in a way that wouldn't cause accidents required considerable _scientific_ knowledge (Feynman's memoirs talk about this; they'd have had steam explosions carting around uranium in aqueous solution without someone realizing they needed a neutron absorber).
It was a monumental challenge for both the scientists and the engineers, and it is indeed impressive that they went from "what's a neutron?" to both controlled and runaway fission devices in a handful of years.
Slashdot Mirror
This is great news. The Hubble is one of our greatest scientific instruments. Without it or a suitable replacement, the effort to learn more about the universe would be left flapping around like a fish out of water.
Not really.
The Hubble is one out of many scientific satellites. It gets a lot of press because it cost a lot to build, and works in wavelengths that give the press pretty pictures.
There are some things the HST can do that other ground- and space-based telescopes can't (mostly due to atmospheric absorption on some wavelengths), but to say that study of the cosmos would be crippled by loss of the Hubble is silly. "Inconvenienced" is a more accurate term.
That having been said, I'm glad it's staying up.
This is why Newton's laws of motion still hold, and why you don't need special relativity to find kinetic energy of slow-moving objects
Yes, but I find it interesting that you can derive kinetic energy of slow-moving objects from special relativity.
From the sentence before the one you are replying to:
When a new model is proposed, it almost always turns out that it reduces to the old model in domains that the old model was designed to address.
I imagine you could do the same with any magnetic card and a little fine iron sawdust that you could make yourself with a grinder.
You're working too hard. www.sci-toys.com mentions that the easiest way for a person to get iron filings is to drag a magnet through the sand at a beach.
Your particle size has to be finer than the size of the domains you're trying to look at. As another posted noted, standard magstripe cards work with domain sizes of about 5-10 mil, and the tapes mentioned by other posters have even finer domain sizes.
When I was a kid sifting magnetite out of sand for fun, typical grain size was much larger.
That's why you should never put scientists up on a pedestal like they are so unquestionable or let them tell you that their crappy theories are truth just becuase "you can't understand it".
Any scientist that tells you something is "true" has a mountain of evidence to back him or her up.
Understand the theories, _then_ criticize. Most of these kinds of objection I've heard have come from people who either took the dumbed-down high school version as gospel, or who just plain don't understand the field being discussed.
Science doesn't know everything. Any good scientist knows the limits of scientific knowledge in their field. All or nearly all models of reality that science has constructed have areas where they don't apply well, as most of these are simpler approximations to very complex systems. But to use this to say that scientists are talking vapour about the areas where they _do_ apply well is extremely foolish.
The progress of science over the past couple of centuries has not generally been to overturn old theories and models, but to extend scientific knowledge to cover cases where the old models didn't apply. When a new model is proposed, it almost always turns out that it reduces to the old model in domains that the old model was designed to address. This is why Newton's laws of motion still hold, and why you don't need special relativity to find kinetic energy of slow-moving objects, and why general relativity still gives you Kepler orbits and Newton's laws of gravitation in weak gravitational fields, and why you don't need to solve quantum electrodynamics equations to find out how strong an electromagnet is.
In this light, I find it amusing that you use Newton's works as a supporting example for ignoring scientists' statements when we still use his laws of motion and gravitation for engineering today.
Can they make wallpaper that enhances my wifi instead of killing it?
Put in conducting patterns along the lines of a zone plate, and maybe. That'll be directional, and only work in some places in the room, though.
What this amounts to is an RF lens, being used as you would use an RF dish.
At what point are people actually going to start making 64 bit applications? I'm not talking 64 bit linux or anything like that, I'm talking consumer level apps and games.
Among other things, it should let the OS map more than a few gigabytes of memory into the address space at one time. A 32-bit application will only be able to see 4 gigabytes (or 2, or whatever the limit ends up being after tag bits and OS space are reserved), but the total amount in use can be more, without an application rewrite needed. This is already done to some extent (my understanding is that the 32-bit processors have 36 bits of address space in total, with a 32-bit per process maximum), but moving to 64 bits gives a lot more headroom.
I see a lot of people upgrading to 64 bit chips, but what good does it do if there's nothing to utilize them? Is it just for bragging rights or what?
I'm a programmer and I have yet to see a need to get a 64 bit chip.
It's handy to have native handling of things like 64-bit integers, but addressable memory space is the most pressing reason right now. You'll be able to mmap() a file larger than 2 gigabytes on x86-64 machines (where up to now you had to use a non-x86 platform). You'll be able to hold more than 2 gigabytes of working data in RAM, which is significant if you're doing video editing (or heavy rendering or really heavy image processing).
Consumer apps and games will move into this niche in a few years (there are algorithms that let you trade off memory footprint and speed, and memory is cheap). But there are several places where the ability to address more memory is important _now_, even for user workstations.
Here's another Dalek tribute, featuring a con artist named Sam Starfall (normally wearing an animatronic environment suit).
Architecutre-wise, its still easier to write an emulator for [on] the PPC than for [on] the IA-32.
Part of the point of my previous post is that this fact a) means quite little when comparing the relative capabilities of the two processors, and b) is being used to make some rather silly claims in this thread. Both are good processors, and both have enthusiasts with more zeal than sense ready to bash the competition.
What do you think is easier to emulate? A low-register-count CPU on a high-register-count CPU, or vice versa?
Emulating a machine with many registers on a machine with few registers will cause spills to memory, which indeed slows things down, but there are other aspects of architecture which will slow things down far more. The x86 architecture is a crawling horror, full of operations with complex side effects and wierd idiosyncracies that are holdovers from bygone eras. I'm told that the PPC line has its own demons to worry about in this regard, before any of the Mac crowd start pointing fingers. Trying to emulate a crawling horror of an architecture requires a large amount of special-casing and time-consuming state tweaking after most operations, or else requires assuming that certain side effects won't be used most of the time and producing an emulator that only *mostly* supports the relevant code, or else requires a cross-compiler with the near-omniscience required to determine for all cases where features are needed, and produce code that does exactly what's needed and nothing more. My understanding is that it's the last approach that's used by modern emulators (with optimization thrown in for giggles), but it's far from perfect, and there is still substantial overhead both in execution time and program memory footprint (which causes extra I-cache stress, slowing things down even more).
In summary, the PPC will still have a hard time emulating an x86, and register count on the x86 is the least of its problems when trying to emulate a PPC.
Endianness is its own can of worms. You can relatively easily tweak endianness of code and immediate values during cross-compilation, but any memory buffers have to be munged at *run* time (because you don't know if the program treats them as being composed of 8-, 16-, 32-, or 64-bit elements, or all of the above). If the latest PPC chip doesn't support this in hardware, emulation becomes a tar-pit.
Anyways, this is why I'm cynically amused by all of these "My 3mul4tor can k1ck y0ur 3mul4tor's 4ss!" posts. And yes, IAACompEng.
You've obviously no clue. Go do your homework. A PPC can emulate a Pentium of roughly the same clock speed without any trouble via VPC right now, whereas a Pentium can emulate a PPC at about a tench of its own speed, in theory, and more like 1/100th of the clockspeed using the emulators that currently exist.
I realize that asking for actual evidence from either side here is futile, but:
- Download SPEC benchmarks.
- Make them go on PPC machine natively with default and tweaked compiler options.
- Make them go on P4 natively with default and tweaked compiler options. Use MSVC/Windows and gcc/*nix, for a good spread - gcc's optimization was Not Good last time I checked. MSVC's was.
- Make the same P4 binaries go under VPC.
The results will probably be enlightening for both of you. I am deeply skeptical of *any* emuation being as fast as the real thing for code that's already optimized (i.e. won't benefit from emulator re-optimization).
You'll also be memory-bound on both machines for several types of task (same speed on both systems), clock-speed bound for several other types of task (favours the P4), register-bound on others (favours the PPC), and cache-bound on yet more (varies by machine configuration).
Apple's been reluctant to post SPEC numbers for a while now, so feel free to settle the issue with real benchmarks instead of a photoshop or emulator DSW.
Isn't that what EE is?
Depends on the university. About 10-20 years ago, this was true. Right now, around here at least you have EE, CS, and CE as distinct disciplines:
At least, that's what it was like when I went through. The flavour of the CE program, and much of its curriculum, will depend on whether it grew out of the EE department, the CS department, or both at the university in question. Likewise, the nature of the EE and CS departments will change depending on how much they offload to CE (EE at a school without a CE department will have a lot more CE material, for instance).
Your mileage may (still) vary
This is the semiconductor devices bible for electrical and computer engineering (in North America, at least).
Excellent book recapping device behavior and describing analog circuits and the issues that come up when you're trying to integrate elements on a die.
This also covers layout and circuit issues, though mostly for digital logic design.
If you want to do digital logic intelligently, or design analog circuits that do their job with precision and effectiveness, you need to go back to school and get a Comp Eng degree. If you want an idea of how engineers use the devices you're trying to optimize, and what factors are important for usability and performance, these books will do.
2.Not as safe - there STILL isn't enough AI computing power to control the traffic and fly the masses safely through the 3D "skyways".
It's not a computing power problem - it's a reliability problem. The computer on your desk has enough number-crunching ability to direct a city's traffic in 2D or 3D in real-time, especially if a simpler sub-optimal-but-good-enough algorithm is used.
The real problem with automatically controlled cars is that the system won't be perfect, and the consequences of failure either on the ground or in the air aren't acceptable. On the ground, your automated vehicle kills a pedestrian (because of vehicle control failure or because they did something foolish). In the air, a malfunction turns your vehicle into a few thousand pounds of flying metal (plus fuel!) looking for something fragile to crash down on.
The 2D case gives you prohibitive liability problems for the manufacturer, and the 3D case gives you accidents that are far less survivable and produce far more collateral damage than the 2D kind. All of these problems are solvable, and I firmly believe we'll end up with computer-controlled ground cars in the not too distant future, but it won't be a cakewalk.
Maybe the idiots in the 50s really did think that anyone who could drivecould surely be a pilot too?
That was the general idea, if I understand correctly. After all, how much harder can it be? (/irony)
The problem is that the sensitivity of the current detectors does not allow to determine wether these has a mass and travel a little less than the speed of light or if they are massless. Neutrinos with mass can resolve the dark energy problem.
Actually, it's the dark _matter_ problem massive neutrinos address, and they only form part of the puzzle ("hot dark matter").
Dark _energy_ appears to be a repulsive force intrinsic to space. This proposed model is one take on a mechanism for it.
Neutrino mass has also been pretty conclusively demonstrated by observations of neutrino _oscillation_ (changing of flavour), which cannot occur if neutrinos are massless. This incidentally also solves the solar neutrino problem (the detectors producing shortfall measurements could only detect one type of neutrino, while solar neutrinos were oscillating between all three types in transit, resulting in many not being detected).
Most of these developments happened within the last decade or so. We're in a very interesting time for particle physics (between new observations, new mathematical approaches to applying string theory, and new approaches to modelling gravity that aren't string theory).
Also included is the coordinates of a particular black hole; when each species gets bored of kicking around with no one to talk to, it departs for a near-event horizon orbit around the black hole, where it waits, along with the other early races, for the galaxy to fill up with interesting people.
:).
This is actually a pretty choice piece of real-estate. If you're close enough to the hole, you can draw power from either the microwave background or (later) the hole, until an incredibly distant time in the future (long after all other sources of power have been exhausted).
I'm going to have to look up that David Brin anthology
Our planet emits enough radio energy to look like a small sun, but it hasn't done so for very long. Some scientists believe that it won't continue at the present level, either, because future requirements will demand higher-capacity transmissions -- radio transmission will fall off in favor of something that's more tightly-focused, in other words.
I find this unlikely. After all, we didn't stop using AM and FM radio when compact microwave transcievers became available, despite having much higher bandwidth available.
Beamed systems or phased arrays being used for point to point will reduce the amount of easily interpreted radiation, but all that means is that an advanced radio-using civilization will just look like a noise-emitter.
I'd actually put this as the main stumbling block to identifying ET civilizations - we may not be able to easily distinguish artificial radio sources from natural ones.
I don't understand your first assertion. One half of a number is not the same as its square root. Even a key length of nine, the square root is 1/3 the key length. For a 100-digit key, the square root is a tenth. Please explain how this "halves" the key size.
A key with 1024 bits has 2^1024 possible values. A key with 2048 bits has 2^2048 possible values. The square root of 2^2048 is 2^1024.
A classical computer brute-force searching a 2048-bit key value requires 2^2048 tests. A quantum computer requires only sqrt(2^2048), which is (2^1024) - the number of operations a classical computer would require to brute-force a key of half the length (1024 bits).
I hope this clears up your question.
I'm not a cryptographer, but I think the advantage of using a quantum computer *is* the fact that it can do a brute-force search exponentially faster than today's hardware.
It can't, in any scheme where you have to actually get data back out of the quantum computer.
Whenever you observe the state, it collapses to a specific value. You have to do a number of tests on the same computation result to get an idea of what the probability distribution is. This takes enough operations to produce the "square root" figure quoted. You only get better than that if the algorithm you're trying to reverse lends itself specifically to a quantum implementation (like Shor's algorithm for factoring).
Someone more heavily into QC can give you a more detailed description of how this works.
In fact, all you have to do is double the key size (in bits) on something like RSA to make it just as hard to break
:).
Bad example
While this is true for any case where you're stuck doing a brute-force search, in the case of RSA there's a very, very fast algorithm for reversing the trapdoor function it uses (Shor's Algorithm, which factors the public key in far better than exponential time).
Using a quantum computer it can search every possible key simultaneously, cracking the encryption almost instantly.
My understanding was that this is not true. At best you get the square root of the number of steps that would be required for a non-quantum brute force search. This means that key sizes are effectively halved, but that isn't an insurmountable problem.
A bigger problem is that some algorithms are intrinsically vulnerable to quantum computing (or to rephrase, take far, far fewer steps to reverse on a quantum computer than a classical one). Factoring is one such case, which is why quantum computing spells the death of RSA. Most other algorithms are relatively safe, if I understand correctly (or at least, have no known quantum computing cracking method beyond brute force; this may change, unless they're _proven_ to have no other cracking method).
In summary, quantum computing is powerful, but not a magic wand that makes all classical encryption schemes invalid.
Obligatory link to the previous slashdot post about the same article, five days ago.
There are a lot of companies who will do small runs of PC boards for you, but you have to give them finished layouts (gerber files). This gut provides the tools to do the layout as well as doing the boards, so it saves you a huge investment in software and learning a layout system.
Check Freshmeat for "circuit board", and you will find many CAD programs that don't involve large financial outlays. I use PCB, myself.
There's still a learning curve for the interface, but the time spent learning it is much less than the time spent actually designing boards.
You have to be careful about the Uncanny Valley, though, at least according to a particular Japanese roboticist. Apparently once you get within a certain closeness of anthropomorphism, small things which aren't "quite right" can really freak people out.
:).
This is especially apropos given the photos of this particular robot. Pale white face, black orbs for eyes, bright red lips, with vertical lines for guide tracks - they'd have a hard time making it look more vampiric if they tried
The Furby also bothered me for the first few days I had it. It was eerily lifelike, and the fact that I was seeing lifelike responses from something I was mentally filing it as an "object" was quite disturbing until I got used to it.
The actual clay... meaning you still have to have clay?
Yes. The whole point of this experiment is to produce better models of soft substances so that they can be used with _other_ types of interface realistically. The glove itself has no feedback characteristics - it's just a measuring device, telling the host computer what happens when you press *this* hard in *that* direction on the target substance (which among other things requires it to build an internal picture of what the current shape of the clay blob is).
Actually, has anyone every detected a black hole that wasn't gobbling up matter from a nearby source (e.g. a star). A lone black hole travelling in the void. Has anyone found such a beast?
Not yet, to the best of my knowledge.
This is part of what gravitational microlensing surveys look for, though the primary targets are objects like brown dwarfs. High-mass objects like non-paired white dwarfs, neutron stars, and black holes should stick out like a sore thumb if they're present.
So far, most of the above that we know about are from other measurements (wobble and accretion disks in paired systems, and radio from rotating neutron stars that happen to be lined up nicely with us). Microlensing events are fairly rare and pretty picky to detect.
Games like this get hyped for so long, and the pre-order BS get's pushed down your throat everytime you step into a GameStop, that it seems no game is sold on merit anymore.
Meanwhile, some of us actually have the patience to wait a week and wait for word of mouth (or see it played at a friend's place) before buying.
There will always be more than enough early adopters and/or people with more money than sense to be able to preview _any_ game like this without a demo.
You're a dumbass. The metal is reactive in air. Calculate the difference in mass and tell me how many freaking times you'd have to use your little centrifuge trick to get the purity you need? Never mind the plumbing problems?
First of all, you're separating a compound of the substance, not raw metal. In the Oak Ridge plant, they used uranium hexafluoride. Still nasty, but won't burst into flame on contact with air (it's already effectively been "burned" with fluorine).
Second of all, the Oak Ridge plant used effusion membranes as a separation method, not centrifuges.
Third of all, you're both being silly. The mass-based separation methods are fairly straightforward - not much beyond undergrad science needed to come up with them. _Implementing_ them was a huge engineering challenge, a highly non-trivial effort. Implementing them in a way that wouldn't cause accidents required considerable _scientific_ knowledge (Feynman's memoirs talk about this; they'd have had steam explosions carting around uranium in aqueous solution without someone realizing they needed a neutron absorber).
It was a monumental challenge for both the scientists and the engineers, and it is indeed impressive that they went from "what's a neutron?" to both controlled and runaway fission devices in a handful of years.