Fun with rectannas (Was: Re:You have the wrong "mi
on
Lunar Power
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· Score: 2
>But the rectenna is MUCH more efficient than a solar panel at turning it into electricity
That's intersting. Why?
Mostly because the rectanna is just an overgrown TV antenna, with the individual elements sized smaller to use a higher frequency. It is called "rectanna" because they also build into it the rectifiers that turn AC microwaves into pulsating DC power. Make several of those into a square panel and -- bingo! -- you've got an element of the receiver grid. NASA's early tests had about 85% efficiency in turning microwaves to electricity. They could probably do better today.
Compare that to a silicon solar cell, which needs to have light penetrate into its blue-gray depths just far enough to generate an electron and hole pair in the active junction between the N and P layers. And, those electrons and holes have to be swept apart by the static field in the junction before they can recombine and be wasted.
Designing a good solar cell is hard. It takes both quantum mechanics and serious material science, plus critical cost controls to be able to manufacture them cheap enough for widespread use.
Desktop Fusion would be incredible but I doubt this will work. I mean if it reaces temps hotter then the sun how can I keep it on my desk?
Others have addressed your confusion between temperature and actual energy content, but there's one thing more: The surface of the sun is not hot enough to cause nuclear fusion. They need to get near the temperature of the Sun's core to have a chance of fusion.
Actually, it's worse than that. To get fusion you have three factors involved: temperature, time, and pressure. All three multiplied together form a fusion quality number:
temperature * time * pressure * constant
In the Sun's core all three are enormous. In the experimental reactors, the time is short (milliseconds vs. millenia) and the pressure is much less (whatever they can manage with magnetic fields and/or inertia vs. the weight of an entire star). As a result, the temperature has to be even higher than that in the Sun's core.
They can offset this by using isotopes that are easier to fuse (deuterium and tritium), but that only helps so much.
Ahem. Have you ever considered that is the point of science? To factor in new evidence as part of a ever converging, successive approximation of the truth?
Absolutely. I am somewhat of a scientist myself and like to think I know a little bit about the scientific method. However, I believe that in God there already is all truth and that He has given us all the truth we need for our time on this earth. Finally, we will be taught the fullness of knowledge when we are able to bear it. I have a hard enough time with third order linear equations...
All the truth we need? Really? I don't know whether you worship Zeus, Odin, Athena, Set, Raven, Tiamat, Baal, Ashera, Quetzalcoatl, or even the new kid on the block, Yahweh, but it doesn't matter. Not one of the myriad of gods humans have revered through the ages have bothered to reveal, say, the germ theory of disease. From that follows simple sanitation, something possible even millenia ago, and which would have saved untold millions from dying agonizing deaths.
Why? Why didn't even one god see fit to proclaim this important principle? It would have given their believers a massive advantage over all the others. And, don't say, "As a test for us." Once the gods start relying on humans to work things out for themselves -- watch out! You've got that nasty science thing again.;-)
It's the nature of the thing, man.
Precicely my point. I don't trust man or his knowledge. I only trust God. Hence the motto of the USA, "In God we trust."
I see. Only trust God. Hmmm.... So, you don't trust your eyes, ears, or any of your other senses? Nor, do you trust your fellow man or what they report to you in good faith? Really? Somehow, I doubt that.
The point you seem to be missing is that science is little more than formularized common sense. If Ugh the caveman touches a rock heated by his campfire and get burnt, he won't touch that rock again. To avoid getting burnt by other rocks Ugh needs to generalize, "Rocks heated by campfire burn Ugh. No touch." Already Ugh is forming a hypothesis, which he will probably test next meal time. A smarter Ugh will realize that many things heated by fire will burn him, molten fat dripping from his antelope haunch, bones, etc. Maybe Ugh will form a theory of Heat,
"Fire make things hot. Hot things burn Ugh. No touch." Add some Material Science to this, and Bingo! cooking utensils: "Hot not run up stick fast, unless it start to burn. Put meat on stick. Hold over fire. Sparks no burn hand."
Ugh has become a primitive scientist. Stone him at once! 8-)
Seriously, you can't sit there wearing woven clothes, typing at a computer, belly full of food planted with mechanical seeders and harvested with a combine, and tell me that knowledge revealed by your god is all we need. Not unless you've got a set of Revealed blueprints for a technological society handed down from On High. Or maybe, up from Down Below.
Earth's gravity still attracts towards the center of the planet.
OK, why? Science still doesn't fully understand gravity. Are there gravity particles? Is there another force that we don't understand, what about the GUT? God knows all these things and He will teach them to us.
OK, and how will god do this? A new set of stone tablets, numbers 3 through 30,000? Educational TV on the God Channel? Are we supposed to sit around on our buns until this happens?
Or, shouldn't we be out there struggling to learn a little more about the universe, you know, doing --horrors!-- science.
Maybe there's dozen of competing hypothesises on how gravity works and maybe we have no experiment to say which ones (if any) are correct, but that's no reason to throw up our collective hands and do nothing. Tomorrow, some bright lad or lassie may cook up a test for gravity that will help winnow the wheat from the chaff of competing theories.
All of that is already well pinned down by experiment, and will stay pinned down until disproven by even more experiments
What about on another planet, or near a black hole or in another universe? Granted the latter is unlikely, but still possible. The fact is, man knows extremely little about our universe and how it works. I may agree with observations, but I don't agree in man's ideas when they so clearly contradict those of God.
Are you saying that God has indicated to you which of the many proposed Grand Unified Theories is correct? If so, has he included some experiments that we can run to verify this?
(Without a successful and repeatable test, your revealed knowledge has to fight it out with all the other revealed knowlege from all other cultures. Good Luck, you'll need it.)
... To give some credit to the "wailing" Creationists,
at least they don't change their story when new
"evidence" comes out.
... Say what you will about religionists and
science being irrefutable, I see science change
it's ideas on a daily basis. My religion hasn't
changed for eternity.
Ahem. Have you ever considered that is the
point of science? To factor in new evidence
as part of a ever converging, successive
approximation of the truth?
To complain about that is like griping that water
is wet. It's the nature of the thing, man.
But, not to worry. Despite your preconceptions,
not everything in science changes, or is likely to
change. Earth's gravity still attracts towards the
center of the planet. Momentum is still conserved,
even when it hurts. (I.e. Stepping into the road
ahead of a speeding bus.) Etc. All of that is
already well pinned down by experiment, and will
stay pinned down until disproven by even more
experiments -- not likely to happen at this stage.
The change that worries you happens on the
frontier. This is a good thing. Behind the slowly
advancing frontier zones are regions of knowledge
that are fairly well known, and thus pretty
reliable. That should please you, if consistency
is your goal.
Really? Then why did their first generation of HW, the Balance series, use National Semi's CPUs?
I don't doubt that there was (is?) lots of crossover between Sequent and Intel Hillsboro, but that's probably due to joint projects and hiring from the same population of engineers....
I wasn`t able to fathom from the article whether this power line equipment can be made to work in the UK. The UK voltage is 230v at 50Hz; if I use a UK to US transformer can I plug this equipment into the UK mains ?
Not by itself. Any power transformer acts like a large choke coil and filters out high frequency signals (RF). It is possible to bypass the RF around the transformer using capacitors, but they had better be very resistant to the spikes caused by switching on and off motors, fluorescent lights, etc, not to mention those induced in the wires by nearby lightning strikes.
Now, if you happened to get one of the resistive 220V to 110V converters, that might have a chance of working. Maybe.
Why in the world would this be? Are you saying that those compilers are being changed to accomodate kernel hacks? Or is the kernel code taking advantage of compiler hacks? I know that gcc has some terrible and dangerous hacks like allowing runtime variable length arrays on the stack. Is the kernel using them? This would seem like a very detrimental situation if so.
The kernel is making use of compiler hacks that aren't strictly standard. You named one. Others include the way that inline asm code is done, some new pragmas, etc.
And yes, many times ANSI just doesn't cover the kind of enhancements compiler and/or kernel developers want, so they have to roll their own.
It's not really wrong, but it does limit portability to another compiler.
To start off, My work win98 machine is faster than my other boxes running linux. Since IS will not allow me to dual boot, I'm just wondering if the GNU utils under windows would allow for a kernel compile.
The Linux kernel is strongly tied to recent gcc compilers (use only either 3.0 or 2.96? 2.97?). If you can get gcc to run under Windows then you have a chance.
Hmmm.... I think that the novel you're thinking of may be "Earth" by David Brin. In that book, Our Hero starts off trying to capture a quantum black hole that was dropped into the Earth's interior when his lab was wrecked by a neo-Luddite riot. (Sound familiar?) The black hole drops through rock and metal like lead through a hot vacuum and is presumably orbiting inside the Earth, maybe growing larger as it is able to eat a denser meal of core material.
The good guys are able to build a "gravity laser" using techniques that are not explained. They use it to scan the core for the black hole and intend to accelerate it to a higher orbit if it is growing rather than evaporating. They find the released hole and it is shrinking. They also find another and larger black hole already in the planet, slowly growing....
Antimatter cannot destroy a black hole, it has positive mass. Even if an anti-particle annihilated a normal particle inside a black hole (assmuming that "inside" has any meaning at all), it wouldn't matter. The high energy gamma rays produced would still have positive energy equal to the mass of the two particles.
To destroy a black hole requires negative mass/energy. That's the secret behind Hawking Radiation. Through some magic I never understood, the particle with negative energy from the spontaneously produced pair is the one that falls into the event horizon and is swallowed. Result: net energy loss by the black hole.
This causes the positive feedback cycle that others have mentioned and in time the black hole explodes in a final blast of radiation. Then we get to see if a naked singularity is left behind.
Suitable punishment (was: Re:rebuilding the towers
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Our New Pearl Harbor
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... Putting them in jail would be a much more satisfying punishment....
I like the ending of one of Tom Clancy's books (The Sum of All Fears??) better. In that, the leaders of a fringe group of Muslim terrorists are captured alive and turned over to an Islamic court for trial. They are found guilty of mass murder and beheaded, all according to strict Islamic law. That takes the wind out of the jihad sails. (I wonder if it also damns them to hell rather than the usual jihad/Paradise thing?)
This is not to say (or jump to the conclusion) that the actual terrorists are Muslim, but maybe the same principle could be made to work for whoever turns out to be responsible....
... Having such a cable to your home (dsl or power line) is like having a big powerful antenna into your home.
What about the impact on our health? I know, the impact of high frequency magnetic fields is not fully studied, and even scientists disagree... So aren't we pushing for radio-antennas to stay far away from our homes? Didn't someone tell us, that having a cellular phone near our brain may cause damages? And now we want this high-frequency antennas to our homes, and to our desktop???
"Don't Panic!" -- The Hitchhiker's Guide to the Galaxy.
Short answer: If there's any real threat from non-ionizing EM radiation, then well over a decade of research by lots of different groups hasn't found it. (And, they've been looking hard too. Finding a threat would bring a big budget increase.;^)
But, don't take my word for it. Rather than relying on what "somebody" said, check out this FAQ
Cellular
Phone Antennas (Mobile Phone Base Stations) and Human Health from the Radiation Oncology department of the Medical College of Wisconsin. It has a fairly comprehensive treatment of the subject.
Anyway, the actual signal power levels on this scheme will be fairly low. In fact, most home power lines are "noisy" with EMI right now. That's a problem for signal processing, but my point is -- adding a modulated signal to all the crap that is already there would be no real change from a "health" aspect, if any such thing exists at all....
And a two-hundred billion dollar corporation goes *poof*, along with 195 billion dollars worth of stock. Stock owned by voters, or retirement funds (in turn owned by voters.)
As others have posted, the proceeds would go to the existing stockholders in amounts that are proportional to the number of shares held. This has the ironic side effect of making Gates and Ballmer even richer than they are now. Oh well.... --
5) Discorporate MSFT - corporations are a legal construct after all, so when one oversteps the bounds of law as repeatedly, aggressively, and unashamedly as Microsoft, revoke its charter. Force an auction of all MSFT assets, including source code, to the highest bidder. Split the assets into small portions and sell them separately. Current MSFT executives and major stockholders will be prohibited from buying these assets.
6) Charge Microsoft's executives in criminal court - The evidence presented was fairly damning. It showed that the anti-competetive behavior was initiated and encouraged at the very top of the corporate hierarchy. Put Gates, Ballmer, Alchin, etc, on trial for racketeering. If found guilty, throw their @$$es into jail -- no probation allowed.
And, what about those who submitted the doctored video tapes of rigged demos in the first phase of the trial? I'm still waiting for perjury charges to be filed against them....
I disagree, I think the billions and billions of money spent on research has more than paid off for Microsoft and users. Like it or not, through their research on what users wants, Microsoft makes huge advances in useability, although sometimes at the expense of stability, etc.
"What users want"? Maybe, if you want to write to the Least Common Denominator....
Anyway, trading off stability for "usability" is a mistake. A good SW Engr. group should be able to achieve both.
Also, why do you have to stop them? If you don't like them, don't buy their stuff and recommend that your friends do the same. I really don't see the need for a focus on stopping Microsoft. If they are as horrible as most people here think, they will stop themselves.
Maybe you missed the reason the AOL / MSFT talks broke down: the Dark Lords of Redmond wanted to tie all A-V formats to WMF with an exclusive contract, freezing out Real, MP3, Ogg Vorbis, etc. They still want to extend their monopoly any way they can.
The fact is that people have choices now in terms of computing. Microsoft doesn't need to be stopped. Make a better product and make it as easy to use as Windows and Microsoft's hold of computing with lessen.
I agree with this with some exceptions. If MSFT would compete solely on the quality of their products, I'd have no problem with them. So long as they are trying to extend their turf by leveraging their existing monopolies, and trying to get new monopoly positions, I've got no use for them.
So, a FS conversion tool would be really nice, like that DOS to NTFS thingy.
Yes, it would be. Don't hold your breath. In long standing *nix tradition, in-place fs conversion tools are very low priority. Instead, you're supposed to convert to the new fs by copying it to a new partition using the usual methods:
Plug in an extra disk temporarily.
Back up the original to tape (twice), then mkfs the partition.
Back it up using the network, then mkfs.
Back up to a compressed tar ball on some other file system.
Excellent! I wonder which distro will be the first to include JFS as an option? Ordinarily, I'd say SuSE, but they've released 7.2 recently.
Sure, I can (and will) install JFS myself, but I want to see it exposed to lots of people in a distro and stand up under the load before I put it on a production server. Example: SuSE and reiserfs. --
Converting keychain lights to White LEDs
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LED Flashlights
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· Score: 1
At most hardware stores you can purchase a small keychain light that uses two watch cell batteries and an LED in a flexible rubber shell. They come with a red LED in most cases; go to Radio Shack and get a white LED to replace the red. I use it all the time, and the batteries last for months. You get a wide bright circle of crisp white illumination. The white is much easier than pure red - I suppose the human vision system relies on color differentiation.
This is good advice except for one thing: All the red LED rubber squeeze lights I ever bought contained alkaline coin cells, which put out 1.5 V each. A red LED can reach its rated current (and brightness) at around 1.85 V, so the 3 V from the batteries is more than enough. (These squeeze lights don't have current limiting resistors. They rely on the batteries' internal resistance to limit current. With watch batteries, that seems to work pretty well.)
So, everthing is fine for red LEDs. White LEDs need about 3.5 V to max out. Their voltage/current curve isn't as sharp as a red LED's, so they will emit some light at 3.0 V, but you aren't seeing them at their best. As the batteries run down, you'll get exponentially less light. Bad juju.
For best results in your squeeze light conversion, remove the two alkaline cells and put in two lithium cells of the same size. The combined 6.0 V output along with lithium cells' ability to sustain nearly 3.0 V over most of the cell's life will keep your light shining brilliantly for a long time. In fact, a Photon Microlight II is just a squeeze light with a better case (hard plastic) and one or two lithium coin cells (depending on which LED you choose).
So, by converting a squeeze light youself you can save lots of cash vs. the Photon's cost of USD $15-$20. --
This picture nicely shows the receptivity of the four kinds of receivers in the human eye.
Nice picture. OK, so if the goal is to fire up the cone cells (which, occupying the fovea, give the sharpest vision) without futzing up the night adaptation of the rods, then we should pick a color that the rods are least sensitive to, while maximizing the cone sensitivityj. This is so we don't have to pump out too much light.
I'd say that means something in the orange through red-orange to red range. Right? --
Adjustible LED flashlights for astronomy
on
LED Flashlights
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· Score: 1
Just use an LED flasher chip: they will act as a charge pump, allowing higher voltage to the LED from a lower-voltage battery. If you set the flash rate to a couple of kilohertz you won't notice the flashing in normal use (although it makes a cool effect if you move the light around: lots of little spots of light), and the flasher chip plus LED will burn WAY less power than a PIC.
You can even adjust the duty cycle to vary the brightness. Furthur, even DratShack carries LED flasher chips.
I've built a number of adjustible LED flashlights over the years for my amateur astronomer friends. A couple of points: First, PICs are CMOS RISC microcontrollers that can operate from DC up to their rated clock speed (32 kHz, or 1, 4, 20, or 40 MHz). Even the standard PICs don't draw much power when under-clocked, and the low power models consume very dern little. Sure, a LM3909 LED flasher doesn't take much power either, but it's a bipolar chip designed in the early '70s. The state of the art has progressed just a bit since then.
Now, a LM3909 can be operated in voltage boost mode (it's usual operating mode) using just one capacitor. I was never able to get a 3909 to both be adjustible over a 100:1 brightness range and still use capacitive voltage boost. Maybe you've managed it, but I never could. I got my best results by operating it as a DC-to-DC boost converter using an inductor, a much smaller capacitor, and two extra resistors to increase the cycle rate up to around 100 kHz. See the National Semiconductor application guide for the LM3909 for lots of circuits that use the 3909 for everything from blinking LEDs, to an audio amplifier, to a coil tester for motorcycles.
Secondly, you're right that a switching power supply is much superior to just burning the excess power in a potentiometer. I've had the best results using DC-to-DC converter chips from Maxim or Linear Technologies. The chips designed for single cell operation are already optimized for low power. Just pick the adjustible output voltage ones, use them in current controlled mode, and you're in business. Choose the right chips and you've got minimal external components and a nice clean surface mount design that can drive the LEDs until the battery is dead, dead, dead. (Some single cell chips can self-start from 0.8 V and operate down to 0.7 V. An alkaline cell is considered dead at around 0.9 V or so.) --
No, not cow lard. Gelatin is made from processed collagen: namely hooves, bones, connective tissues, etc, that are boiled and/or treated with mild acids. --
Umm, probably not. Remember that when they were using the retroreflectors left on the Moon by the Apollo astronauts, it took both a powerful laser and a very sensitive photocell to get the job done. And, that's just to get a measurable signal there and back, not to transfer real power. The much greater distance to Mercury would make optical power transmission much harder than to the Moon, to say nothing of the problems of focusing incoherent light over that far.
You could do better using laser light, which can be more precisely focused. See Robert Forrest's Flight of the Dragonfly for a fictional account in which he proposes to shoot industrial amounts of laser light across not just interplanetary, but interstellar distances. The scale of Doc Forrest's astro-engineering is not for the faint hearted. 8^)
But, if you're going to go to Mercury and set up a power station, why not make something so valuable that it is worth the effort to send it back to Earth? Why not make antimatter, bottle it, and ship it back? That would avoid transmission losses entirely.
(Of course, there is the little problem that current antimatter production techniques are fabulously inefficient. The best ratio of power in to potential-energy-of-antimatter out is millions to one!) --
Speaking of large man made objects in space, what about all of our junk from previous NASA endeavors left orbiting (or left with the hope that they would burn up eventually)? What about all of the micro-meteorites that are moving fast enough to slice a car in half?
By putting a huge array of solar-panels in space, you've just created an object with a considerably large surface-area to mass ratio. Therefore, the probability of it getting hit, damaged, or even destroyed by speeding space junk is all the larger.
Yup. Intelligent design would allow for all that: The micro-meteorites aren't too much of a problem; they're moving so fast that they'll mostly punch clean holes through the paper-thin solar cells. Even if the hole shorts out the cell -- no problem. The panel is made up of a bunch of fairly small, independent solar cells. Losing a few isn't a big issue. Build it with more than required. (You'll need the extra capacity eventually. The radiation in space degrades the power output of solar cells over time. Commercial satellites are always sent up with enough extra solar cells to last the sat's design life.)
When too many cells are bad, either due to damage or radiation, it's time to send out the repair crew.
Space junk is a problem too, but more so in low orbit. Solar power sattelites would be put in geosynchronous orbit, about 23,000 miles up. Everyone who puts a satellite up there is supposed to minimize the amount of junk they drop. Plus, they should keep enough reserve fuel to send the sat out from geo synch to a "retirement" orbit when its useful life is over.
How much of a problem is this? I don't know, but someone must. Who collects statistics on comm sat and weather sat failures?
An earlier post was complaining about how we hadn't built anything huge in space. This is true, but the lack of wind means that large foil structures supported by springy wires can survive for years in space. Didn't the Russians try a huge folding space mirror a while back? They destroyed it afterwards, to avoid the ire of amateur astronomers.;^)
Even in geosync orbit there are limits to how flimsy a structure can be before undamped vibrations or the feeble breath of low powered maneuvering thrusters rip it apart. But, very lightweight construction by Earth standards should be possible in space.
Think of the Echo 1 balloon, from the days before active comm sats. It was just a huge, spherical, aluminum coated balloon with a few pounds of volatile chemicals inside. Once launched and ejected from the rocket, the sun's heat vaporized the chemicals and inflated the balloon. Once inflated, it didn't matter much whether a meteorite punctured the balloon or not. There was no air to make it flatten out, no gravity to deflate it.
In low orbit with a huge cross section and almost no mass, even the faint traces of atmosphere present eventually brought Echo 1 back to Earth. And yes, the microwave reflections from the balloon did change a bit over time, showing that the bag was wrinkling some. Still, Echo 1 is an example of how a large, flimsy construction is possible in space -- and under harsher conditions to low mass objects than would be found out at geosynch orbit. --
Actually, making the solar panels on the Moon isn't that bad an idea. Or at least grabbing more of the resources from there, a lot less costly (in energy) to move mass from the Lunar surface to geosysnc earth orbit than from the Earth's gravity well.
Same for electricians, really, given a lunar base/factory.
Since solar cells can be made from sand,
O' Neill's original plan called for lunar mass drivers to shoot bags of raw materials (selected regolith [i.e. sand, etc.]) into the Earth-Moon L1 (or maybe L2) point where a catcher net would collect them. The bags would be shipped to L4 or L5 by a solar powered mass driver propelled transfer ship. This was pretty neat -- the transfer ship would need no fuel, just sunlight and hurling some of the cargo out the back at Mach 29. [8^)
John S. Lewis and company at the U. of Arizona have since shown in Breaking the Bonds of Earth: Space Resources and other works, that it would be cheaper to get the needed regolith from certain Near Earth Asteroids. There are at least two asteroids from which you can return cargo capsules by applying a delta-V of less than 60 meters/sec (134 miles/hour). The launch windows only open once every few years for each asteroid, so we need to spot a couple more likely ones and get those automated dirt bagger robots on their way.
Either that or send larger missions that can shoot back more capsules when the launch windows are open. --
(1)By the time it's "mostly harmless," won't it be sufficiently low-energy to be completely useless?
The atomspheric energy absorption is not high enough to make this inefficient and does not really contribute to making this *mostly harmless*. The reason it becomes *mostly harmless* is due to dispersion of the beam over a large area. So, a larger antenna is used to pick it up.
People need to check out the solar power satellites link cited in the post. The safety details have been addressed long ago.
Too many folks won't read the reference links, so to elaborate on the safety issues:
The highest beam energy on Earth's surface at any point on or off the antenna array will be less than that produced by talking on a cellular phone. (About 26 milliwatts per square cm.)
The real problem is holding a microwave beam tight enough to carry useful energy over the ~23,000 miles from geosynchronous orbit to Earth.
This will be done using a large phased array transmitter. It uses a transmitter array of many small emitter modules synchronized and phased together by a pilot signal from the center of the receiver antenna array. If the pilot signal is lost, the emitters rapidly unsynchronize and the power sat's energy is dispersed over an area several times that of the entire planet, dissipating it down to essentially zero energy at any one spot.
In other words, only when the emitter array is phased together can it be said to be transmitting a beam at all, rather than frittering away its microwaves in all directions, mostly into deep space. No pilot signal, no synchronization, no beam, no cities fried like anthills.
Slashdot Mirror
Mostly because the rectanna is just an overgrown TV antenna, with the individual elements sized smaller to use a higher frequency. It is called "rectanna" because they also build into it the rectifiers that turn AC microwaves into pulsating DC power. Make several of those into a square panel and -- bingo! -- you've got an element of the receiver grid. NASA's early tests had about 85% efficiency in turning microwaves to electricity. They could probably do better today.
Compare that to a silicon solar cell, which needs to have light penetrate into its blue-gray depths just far enough to generate an electron and hole pair in the active junction between the N and P layers. And, those electrons and holes have to be swept apart by the static field in the junction before they can recombine and be wasted. Designing a good solar cell is hard. It takes both quantum mechanics and serious material science, plus critical cost controls to be able to manufacture them cheap enough for widespread use.
Others have addressed your confusion between temperature and actual energy content, but there's one thing more: The surface of the sun is not hot enough to cause nuclear fusion. They need to get near the temperature of the Sun's core to have a chance of fusion.
Actually, it's worse than that. To get fusion you have three factors involved: temperature, time, and pressure. All three multiplied together form a fusion quality number:
In the Sun's core all three are enormous. In the experimental reactors, the time is short (milliseconds vs. millenia) and the pressure is much less (whatever they can manage with magnetic fields and/or inertia vs. the weight of an entire star). As a result, the temperature has to be even higher than that in the Sun's core.They can offset this by using isotopes that are easier to fuse (deuterium and tritium), but that only helps so much.
All the truth we need? Really? I don't know whether you worship Zeus, Odin, Athena, Set, Raven, Tiamat, Baal, Ashera, Quetzalcoatl, or even the new kid on the block, Yahweh, but it doesn't matter. Not one of the myriad of gods humans have revered through the ages have bothered to reveal, say, the germ theory of disease. From that follows simple sanitation, something possible even millenia ago, and which would have saved untold millions from dying agonizing deaths.
Why? Why didn't even one god see fit to proclaim this important principle? It would have given their believers a massive advantage over all the others. And, don't say, "As a test for us." Once the gods start relying on humans to work things out for themselves -- watch out! You've got that nasty science thing again. ;-)
I see. Only trust God. Hmmm.... So, you don't trust your eyes, ears, or any of your other senses? Nor, do you trust your fellow man or what they report to you in good faith? Really? Somehow, I doubt that.
The point you seem to be missing is that science is little more than formularized common sense. If Ugh the caveman touches a rock heated by his campfire and get burnt, he won't touch that rock again. To avoid getting burnt by other rocks Ugh needs to generalize, "Rocks heated by campfire burn Ugh. No touch." Already Ugh is forming a hypothesis, which he will probably test next meal time. A smarter Ugh will realize that many things heated by fire will burn him, molten fat dripping from his antelope haunch, bones, etc. Maybe Ugh will form a theory of Heat, "Fire make things hot. Hot things burn Ugh. No touch." Add some Material Science to this, and Bingo! cooking utensils: "Hot not run up stick fast, unless it start to burn. Put meat on stick. Hold over fire. Sparks no burn hand."
Ugh has become a primitive scientist. Stone him at once! 8-)
Seriously, you can't sit there wearing woven clothes, typing at a computer, belly full of food planted with mechanical seeders and harvested with a combine, and tell me that knowledge revealed by your god is all we need. Not unless you've got a set of Revealed blueprints for a technological society handed down from On High. Or maybe, up from Down Below.
OK, and how will god do this? A new set of stone tablets, numbers 3 through 30,000? Educational TV on the God Channel? Are we supposed to sit around on our buns until this happens?
Or, shouldn't we be out there struggling to learn a little more about the universe, you know, doing --horrors!-- science.
Maybe there's dozen of competing hypothesises on how gravity works and maybe we have no experiment to say which ones (if any) are correct, but that's no reason to throw up our collective hands and do nothing. Tomorrow, some bright lad or lassie may cook up a test for gravity that will help winnow the wheat from the chaff of competing theories.
Are you saying that God has indicated to you which of the many proposed Grand Unified Theories is correct? If so, has he included some experiments that we can run to verify this?
(Without a successful and repeatable test, your revealed knowledge has to fight it out with all the other revealed knowlege from all other cultures. Good Luck, you'll need it.)
Ahem. Have you ever considered that is the point of science? To factor in new evidence as part of a ever converging, successive approximation of the truth?
To complain about that is like griping that water is wet. It's the nature of the thing, man.
But, not to worry. Despite your preconceptions, not everything in science changes, or is likely to change. Earth's gravity still attracts towards the center of the planet. Momentum is still conserved, even when it hurts. (I.e. Stepping into the road ahead of a speeding bus.) Etc. All of that is already well pinned down by experiment, and will stay pinned down until disproven by even more experiments -- not likely to happen at this stage.
The change that worries you happens on the frontier. This is a good thing. Behind the slowly advancing frontier zones are regions of knowledge that are fairly well known, and thus pretty reliable. That should please you, if consistency is your goal.
Really? Then why did their first generation of HW, the Balance series, use National Semi's CPUs?
I don't doubt that there was (is?) lots of crossover between Sequent and Intel Hillsboro, but that's probably due to joint projects and hiring from the same population of engineers....
Not by itself. Any power transformer acts like a large choke coil and filters out high frequency signals (RF). It is possible to bypass the RF around the transformer using capacitors, but they had better be very resistant to the spikes caused by switching on and off motors, fluorescent lights, etc, not to mention those induced in the wires by nearby lightning strikes.
Now, if you happened to get one of the resistive 220V to 110V converters, that might have a chance of working. Maybe.
The kernel is making use of compiler hacks that aren't strictly standard. You named one. Others include the way that inline asm code is done, some new pragmas, etc.
And yes, many times ANSI just doesn't cover the kind of enhancements compiler and/or kernel developers want, so they have to roll their own. It's not really wrong, but it does limit portability to another compiler.
The Linux kernel is strongly tied to recent gcc compilers (use only either 3.0 or 2.96? 2.97?). If you can get gcc to run under Windows then you have a chance.
The good guys are able to build a "gravity laser" using techniques that are not explained. They use it to scan the core for the black hole and intend to accelerate it to a higher orbit if it is growing rather than evaporating. They find the released hole and it is shrinking. They also find another and larger black hole already in the planet, slowly growing....
To destroy a black hole requires negative mass/energy. That's the secret behind Hawking Radiation. Through some magic I never understood, the particle with negative energy from the spontaneously produced pair is the one that falls into the event horizon and is swallowed. Result: net energy loss by the black hole.
This causes the positive feedback cycle that others have mentioned and in time the black hole explodes in a final blast of radiation. Then we get to see if a naked singularity is left behind.
I like the ending of one of Tom Clancy's books (The Sum of All Fears??) better. In that, the leaders of a fringe group of Muslim terrorists are captured alive and turned over to an Islamic court for trial. They are found guilty of mass murder and beheaded, all according to strict Islamic law. That takes the wind out of the jihad sails. (I wonder if it also damns them to hell rather than the usual jihad/Paradise thing?)
This is not to say (or jump to the conclusion) that the actual terrorists are Muslim, but maybe the same principle could be made to work for whoever turns out to be responsible....
"Don't Panic!" -- The Hitchhiker's Guide to the Galaxy.
Short answer: If there's any real threat from non-ionizing EM radiation, then well over a decade of research by lots of different groups hasn't found it. (And, they've been looking hard too. Finding a threat would bring a big budget increase. ;^)
But, don't take my word for it. Rather than relying on what "somebody" said, check out this FAQ Cellular Phone Antennas (Mobile Phone Base Stations) and Human Health from the Radiation Oncology department of the Medical College of Wisconsin. It has a fairly comprehensive treatment of the subject.
They've got other EMF related FAQs, too:
Anyway, the actual signal power levels on this scheme will be fairly low. In fact, most home power lines are "noisy" with EMI right now. That's a problem for signal processing, but my point is -- adding a modulated signal to all the crap that is already there would be no real change from a "health" aspect, if any such thing exists at all....
As others have posted, the proceeds would go to the existing stockholders in amounts that are proportional to the number of shares held. This has the ironic side effect of making Gates and Ballmer even richer than they are now. Oh well....
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5) Discorporate MSFT - corporations are a legal construct after all, so when one oversteps the bounds of law as repeatedly, aggressively, and unashamedly as Microsoft, revoke its charter. Force an auction of all MSFT assets, including source code, to the highest bidder. Split the assets into small portions and sell them separately. Current MSFT executives and major stockholders will be prohibited from buying these assets.
6) Charge Microsoft's executives in criminal court - The evidence presented was fairly damning. It showed that the anti-competetive behavior was initiated and encouraged at the very top of the corporate hierarchy. Put Gates, Ballmer, Alchin, etc, on trial for racketeering. If found guilty, throw their @$$es into jail -- no probation allowed.
And, what about those who submitted the doctored video tapes of rigged demos in the first phase of the trial? I'm still waiting for perjury charges to be filed against them....
Hey, I can dream can't I? ;^)
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"What users want"? Maybe, if you want to write to the Least Common Denominator.... Anyway, trading off stability for "usability" is a mistake. A good SW Engr. group should be able to achieve both.
Maybe you missed the reason the AOL / MSFT talks broke down: the Dark Lords of Redmond wanted to tie all A-V formats to WMF with an exclusive contract, freezing out Real, MP3, Ogg Vorbis, etc. They still want to extend their monopoly any way they can.
I agree with this with some exceptions. If MSFT would compete solely on the quality of their products, I'd have no problem with them. So long as they are trying to extend their turf by leveraging their existing monopolies, and trying to get new monopoly positions, I've got no use for them.
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Yes, it would be. Don't hold your breath. In long standing *nix tradition, in-place fs conversion tools are very low priority. Instead, you're supposed to convert to the new fs by copying it to a new partition using the usual methods:
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Sure, I can (and will) install JFS myself, but I want to see it exposed to lots of people in a distro and stand up under the load before I put it on a production server. Example: SuSE and reiserfs.
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This is good advice except for one thing: All the red LED rubber squeeze lights I ever bought contained alkaline coin cells, which put out 1.5 V each. A red LED can reach its rated current (and brightness) at around 1.85 V, so the 3 V from the batteries is more than enough. (These squeeze lights don't have current limiting resistors. They rely on the batteries' internal resistance to limit current. With watch batteries, that seems to work pretty well.)
So, everthing is fine for red LEDs. White LEDs need about 3.5 V to max out. Their voltage/current curve isn't as sharp as a red LED's, so they will emit some light at 3.0 V, but you aren't seeing them at their best. As the batteries run down, you'll get exponentially less light. Bad juju.
For best results in your squeeze light conversion, remove the two alkaline cells and put in two lithium cells of the same size. The combined 6.0 V output along with lithium cells' ability to sustain nearly 3.0 V over most of the cell's life will keep your light shining brilliantly for a long time. In fact, a Photon Microlight II is just a squeeze light with a better case (hard plastic) and one or two lithium coin cells (depending on which LED you choose).
So, by converting a squeeze light youself you can save lots of cash vs. the Photon's cost of USD $15-$20.
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Nice picture. OK, so if the goal is to fire up the cone cells (which, occupying the fovea, give the sharpest vision) without futzing up the night adaptation of the rods, then we should pick a color that the rods are least sensitive to, while maximizing the cone sensitivityj. This is so we don't have to pump out too much light.
I'd say that means something in the orange through red-orange to red range. Right?
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I've built a number of adjustible LED flashlights over the years for my amateur astronomer friends. A couple of points: First, PICs are CMOS RISC microcontrollers that can operate from DC up to their rated clock speed (32 kHz, or 1, 4, 20, or 40 MHz). Even the standard PICs don't draw much power when under-clocked, and the low power models consume very dern little. Sure, a LM3909 LED flasher doesn't take much power either, but it's a bipolar chip designed in the early '70s. The state of the art has progressed just a bit since then.
Now, a LM3909 can be operated in voltage boost mode (it's usual operating mode) using just one capacitor. I was never able to get a 3909 to both be adjustible over a 100:1 brightness range and still use capacitive voltage boost. Maybe you've managed it, but I never could. I got my best results by operating it as a DC-to-DC boost converter using an inductor, a much smaller capacitor, and two extra resistors to increase the cycle rate up to around 100 kHz. See the National Semiconductor application guide for the LM3909 for lots of circuits that use the 3909 for everything from blinking LEDs, to an audio amplifier, to a coil tester for motorcycles.
Secondly, you're right that a switching power supply is much superior to just burning the excess power in a potentiometer. I've had the best results using DC-to-DC converter chips from Maxim or Linear Technologies. The chips designed for single cell operation are already optimized for low power. Just pick the adjustible output voltage ones, use them in current controlled mode, and you're in business. Choose the right chips and you've got minimal external components and a nice clean surface mount design that can drive the LEDs until the battery is dead, dead, dead. (Some single cell chips can self-start from 0.8 V and operate down to 0.7 V. An alkaline cell is considered dead at around 0.9 V or so.)
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No, not cow lard. Gelatin is made from processed collagen: namely hooves, bones, connective tissues, etc, that are boiled and/or treated with mild acids.
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You could do better using laser light, which can be more precisely focused. See Robert Forrest's Flight of the Dragonfly for a fictional account in which he proposes to shoot industrial amounts of laser light across not just interplanetary, but interstellar distances. The scale of Doc Forrest's astro-engineering is not for the faint hearted. 8^)
But, if you're going to go to Mercury and set up a power station, why not make something so valuable that it is worth the effort to send it back to Earth? Why not make antimatter, bottle it, and ship it back? That would avoid transmission losses entirely.
(Of course, there is the little problem that current antimatter production techniques are fabulously inefficient. The best ratio of power in to potential-energy-of-antimatter out is millions to one!)
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Yup. Intelligent design would allow for all that: The micro-meteorites aren't too much of a problem; they're moving so fast that they'll mostly punch clean holes through the paper-thin solar cells. Even if the hole shorts out the cell -- no problem. The panel is made up of a bunch of fairly small, independent solar cells. Losing a few isn't a big issue. Build it with more than required. (You'll need the extra capacity eventually. The radiation in space degrades the power output of solar cells over time. Commercial satellites are always sent up with enough extra solar cells to last the sat's design life.)
When too many cells are bad, either due to damage or radiation, it's time to send out the repair crew.
Space junk is a problem too, but more so in low orbit. Solar power sattelites would be put in geosynchronous orbit, about 23,000 miles up. Everyone who puts a satellite up there is supposed to minimize the amount of junk they drop. Plus, they should keep enough reserve fuel to send the sat out from geo synch to a "retirement" orbit when its useful life is over.
How much of a problem is this? I don't know, but someone must. Who collects statistics on comm sat and weather sat failures?
An earlier post was complaining about how we hadn't built anything huge in space. This is true, but the lack of wind means that large foil structures supported by springy wires can survive for years in space. Didn't the Russians try a huge folding space mirror a while back? They destroyed it afterwards, to avoid the ire of amateur astronomers.
Even in geosync orbit there are limits to how flimsy a structure can be before undamped vibrations or the feeble breath of low powered maneuvering thrusters rip it apart. But, very lightweight construction by Earth standards should be possible in space.
Think of the Echo 1 balloon, from the days before active comm sats. It was just a huge, spherical, aluminum coated balloon with a few pounds of volatile chemicals inside. Once launched and ejected from the rocket, the sun's heat vaporized the chemicals and inflated the balloon. Once inflated, it didn't matter much whether a meteorite punctured the balloon or not. There was no air to make it flatten out, no gravity to deflate it.
In low orbit with a huge cross section and almost no mass, even the faint traces of atmosphere present eventually brought Echo 1 back to Earth. And yes, the microwave reflections from the balloon did change a bit over time, showing that the bag was wrinkling some. Still, Echo 1 is an example of how a large, flimsy construction is possible in space -- and under harsher conditions to low mass objects than would be found out at geosynch orbit.
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Since solar cells can be made from sand, O' Neill's original plan called for lunar mass drivers to shoot bags of raw materials (selected regolith [i.e. sand, etc.]) into the Earth-Moon L1 (or maybe L2) point where a catcher net would collect them. The bags would be shipped to L4 or L5 by a solar powered mass driver propelled transfer ship. This was pretty neat -- the transfer ship would need no fuel, just sunlight and hurling some of the cargo out the back at Mach 29. [8^)
John S. Lewis and company at the U. of Arizona have since shown in Breaking the Bonds of Earth: Space Resources and other works, that it would be cheaper to get the needed regolith from certain Near Earth Asteroids. There are at least two asteroids from which you can return cargo capsules by applying a delta-V of less than 60 meters/sec (134 miles/hour). The launch windows only open once every few years for each asteroid, so we need to spot a couple more likely ones and get those automated dirt bagger robots on their way.
Either that or send larger missions that can shoot back more capsules when the launch windows are open.
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Too many folks won't read the reference links, so to elaborate on the safety issues:
In other words, only when the emitter array is phased together can it be said to be transmitting a beam at all, rather than frittering away its microwaves in all directions, mostly into deep space. No pilot signal, no synchronization, no beam, no cities fried like anthills.
Sorry, Dr. Evil, but that's the way it is.
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