It seems that we have a number of intelligent, articulate punks on slashdot today, which is pretty cool, IMHO. Of course, there are always the hardcore ones, like AC parent's post (not sure if serious or not). It reminds me of what a punk friend of mine said once: "You're not punk unless you've had scabies!".
Of course, really there are lots of different kind of punks. I used to know this really hot little punk chick in Savannah named Kitty who knew more about music than god and lived homeless for a year "just to see what it was like". Was she punk? Hell yeah! Did she have scabies? I hope not! (scratches crotch)
Disclosure: I work for a manufacturer of treatment plan verification devices. It never hurts to actually ~check~ to see that the software is working as spec'ed.
Well, sort of. A Carnot engine, even one which uses photons as its working fluid, must return to its original state. A solar sail "expander/compressor" like you discuss would technically only be one-half of a Carnot engine. To incorporate the rest, you either have to let the photons escape (that's easy), or turn off the sun for part of the cycle (that's hard). The Steady Flow analysis is more correct, but is not an analysis of a Carnot cycle. However, I should point out that the tiny red-shift in the photons is not a sign of a tiny energy efficiency, but rather of a small delta energy per photon collision. Given infinite space to expand in, a very large percentage of the energy of the photon gas can be collected (as the temperature difference between the sun (6000 K) and empty space (3 K) is fairly large. It's just that you have to expand your volume by a large amount to get it, and the differential with respect to the volume is very small.
Basically, we're all saying the same things here. There are always fifty gazillion ways of looking at any physics problem. But Gold's analysis is wrong.
If the mirror were 100% efficient, which is physically impossible, then the light would remain bouncing around in the sphere. However, if the mirror were 99.99999% efficient, then very quickly the light in the mirror would become black-body radiation. What you have described is essentially a blackbody cavity. Blackbody radiation is basically light whose frequency distribution is determined by temperature - in this case by the temperature of the inside of the sphere. So if you were to open up your hole again and let the light out after having been in there for a few fractions of a second, it would have a blackbody distribution corresponding to a temperature equal to the temperature of the sphere before you put in the light, plus the increase in temperature associated with the light being partially absorbed (or a decrease in temperature, if the sphere starts out at a higher temperature than the light).
You are correct that the Carnot efficiency cannot be calculated for this case, as it is not returning to it's original position. However, in the postulated case of a perfect mirror, there is no heat sink, as the photons will be reflected back towards the sun, and not radiated from the back of the sail. If the photons are absorbed by the sail, then some are radiated to the heat sink, and the expansion is no longer adiabatic (which is consistent with the lower momentum transfer). Note that if the mirror ~was~ returned to its original position, and the sun was insulated against losses in directions other than towards the sail, you would have an adiabatic expansion and then compression of the photons, leaving you with no net change in energy. Gold complains in his paper of physicists not treating photons thermodynamically. That's funny - I seem to remember working out a problem using an adiabatic expansion of a photon "gas" in my undergraduate days. I don't remember the equation of state off the top of my head, but I guarantee you can find it in Callen or any other thourough thermo book. Yes, IAAP. I also think that slashdotters should note that this was published in the Arxiv, which is NOT a peer reviewed publication (although I must say that the Arxiv rocks!). The Arxiv is sort of like an open source scientific journal, or a BBS for scientific papers. I highly recommend wandering around in it for a few hours, but remember to take everything in there with a grain of salt. Darn. I was going to try NOT posting to slashdot today. Oh, well. Feed the addiction (sticks needle labeled "/." in arm).
Most of NASA's work is already available publicly. Try the third floor of the FIT library. There's some amazing stuff in there. That's where I first found out about NERVA, and also how the Shuttle's configuration was decided upon in 1968 (before we landed on the moon).
I realize that it's about as useless as complaining about the press referring to crackers as hackers, but:
Technology != IT !!!!!
Those of us who work in technological fields ~outside~ of computing/telecom get a little annoyed when people use the term "Tech sector" or "Tech spending" to refer to only the IT sector. If you mean "Information Technology", call it that, or use the handy term "IT". Please don't co-opt the word Technology to only mean your little bits and bytes. Rockets, airplanes, oil-wells, nuclear submarines and medical breakthroughs also involve a little bit of "Technology" too, and it's annoying when analysts refer to the companies who make these things as not being "Tech companies". We can't help if the press is stupid, but this is Slashdot - we are Techie nerds and should know better.
Yes, that would be a problem, if the purpose of the Bill were to put works in the future into public domain. However, this bill was created to fight the ~retroactive~ extension of copyrights from >50 years ago. If there is anything I don't like about the bill, it is that it is adding a fee retroactively, something I'd be pissed about if it was foisted on me. But I understand and approve of what the Bill proposes: that retroactively extended copyrights have a retroactive fee imposed upon them.
You see, the author of "The Scandalous Hussy" can't go back to 1937 to prepay the fee on his bodice-ripping pulp novel, so if he doesn't pay the fee now, then it becomes public domain. THAT is the purpose of the bill.
Looks very cool, and the price is actually rather good IMHO for a little guy like that. I've always wanted to use something like this for building a robot. It's a perfect size.
But first, let's give it a real-world test: a good old-fashioned Slashdotting! I mean, what would it say if a server company can't handle being slashdotted?
Last week, Sen. Hatch made an outrageous suggestion for a bill to allow copyright holders to destroy file-sharer's PCs . Some people thought this was just a spurious bill to take the heat off of the "real dangerous" laws that would then be proposed, which might seem more "rational".
Apparently this is the real bill.
So, please tell me what is rational about this? Yes, distributing materials without the permission of the copyright owner is illegal. We already have laws and civil penalties for this. This may seem like a good law (in the same way that if we had a problem with lots of windows being broken, the FBI assigning more agents to a Broken Windows Units would seem reasonable), but in fact, it is not. If I find someone violating one of my patents, I sue them, hopefully I win, and they pay me recompense or the Sherrif comes and takes their car. This is how it works. I can't expect the FBI to go around looking for people violating my patents, gathering evidence at taxpayer expense, and then handing all the information over to me.
If they are to do so, they ought to do this service for everybody. Somehow I get the feeling they aren't going to be worried about my IP, or the IP of my friends with the Indy-band website. They are going to be protecting ONLY the big money, RIAA/MPAA IP. If you don't believe this, look at recent history. This is unfair and wrong. Yes, the RIAA and MPAA are suffering from massive violations of their IP rights. But to spend tax monies on agents specifically dispatched to police their IP is unfair to other IP holders, as well as the taxpayers. It is essentially a subsidy to the legal expenses of the RIAA and MPAA. Do we really want that? Let them try to work with the laws we have.
The MPAA and RIAA have a basic problem with their business model (they are basically in the same boat as each other). What they need to realize, is that in a world of near instaneous worldwide transmission and recording, once something is released, that's it, its out there. TV and radio have worked fine with this for years (few ever complained about people recording CHiPs and Knight Rider with their VCRs). Yet TV and radio made plenty of money. If the MPAA and RIAA want to make money, they need to rework their distribution methods so that the choke-point is closer to the artist.
Until the MPAA and RIAA realize that they can do things a different way, they will keep trying to get the government to enforce their easily-violated property rights. The only way to make them change is to NOT make it easy for them to sue half of America. Make it as hard for them as it would be for you, or me.
As Thud457 so kindly pointed out, this is freshman physics. It should be in your physics texbook (if you don't have one, get one! or download this ). Basically, L=I*w , where L is the angular momentum, I is the moment of inertia, and w is the angular velocity. What does this mean? Well, if you want to see some serious precession etc., you want to have a high angular momentum. So spin something fast with lots of mass far from the center. Take a look at this: precession . I always found that bicycle wheels worked great - the only hard part is holding on to them, so I would suggest mounting the axle to something. For additional fun spin it up with a drill or small motor. Keep your duty factor low or you'll burn out the motor - drill motors are meant to spin fast, not slow.
I just checked out that textbook I linked to, and the angular momentum section suXors. Perhaps I ought to do an "Ask Slashdot" on Open Source Textbooks. Or would that be a dupe? I searched and didn't find NEthing covering physics textbooks. Hmm.
Good luck with your projects. I looked at your website and it looks like you are a true techie geek. Consider your hand shaken. Try not to catch fire.
Shortly after is right. I am amazed at how fast this meme spread. I was hearing that sick joke in the lunchroom at my school 20 MINUTES after the explosion. It might have had something to do with the fact that my school was within sight of the launch (30 miles south of the cape), so we saw the explosion with our own eyes, instead of on TV. Did the joke appear as fast elsewhere?
It was my twelfth birthday. I loved the shuttle when I was a kid; to me it represented science. But I know that we need to replace it with something better, cheaper, simpler. People have been saying "to kill the shuttle is to kill the space program" since I was a kid. Sorry, but the shuttle has already killed the space program. Or at least frozen it during my lifetime. As long as the shuttle flies, the politicians will not pony up money for a replacement system. If America has no space presence, the embarrasment will force them to fund a new system.
I mean jeez, I live in the economic blast radius of the Cape and I'm asking for this. My friends' Dads all lost their jobs in '86. This year, the shuttle loss didn't really effect the local economy, at least outside of Titusville. Why? Well, Space is not the growth industry on the Space Coast that it used to be. How sad is that?
Why do editors link to articles which don't tell you anything when they could just as easily link to the original site which doesn't tell you much more? I don't think that the BBC mentioned "Hybrid State Maser" or other remotely technical details...
Trimprob
Actually I was doing something kind of weird. I wanted to use the centrifuge for separating a continuously-flowing liquid, so I was trying to make the centrifuge essentially out of tubing. I was going to use welded threaded connections, as I didn't think that swageloks would really cut it. I was really worried about the balancing, and that was the primary reason I decided not to attempt it. In addition the gravity drip design (drip in the top, separated liquids fly out at different height levels) would have made balance a possibly dynamic issue (ie not fun). If you are just making a gyroscope, I would first take a look at what you are using it for. If you are just having fun/looking at gyroscopic effects, you don't really need high speed. A decently large inertial moment and a few rpm would do fine. Now if you are doing weird mad science stuff, I would need to know more to give any advice. But in general, if you are making a gyroscope, you want to have your mass more toward the edge. Anything big and heavy like you are describing should show decent gyroscopic motion, but be careful! 113 cu in of metal can pack a wallop!
Well, you can find out, to a good approximation: The amperage is just the voltage divided by the resistance, as everybot is posting to this thread. So you need to find the resistance. There are two components to this resistance. One is you and one is the batteries. You can estimate your own resistance using an ohmeter, connecting it between the points on your body which touched the contacts. Note that this will slightly over-estimate your resistance, as the resistance of the human body decreases with increasing voltage (as do many objects). You can find the internal resistance of the batteries using an ammeter. Connect one contact from the batteries to the ammeter, then connect a wire with a known resistor in series to the other end. Make sure the resistor is large enough that the current level won't blow out your ammeter. Then connect the wire to the other end of the batteries. There may be a small plasma ball, but don't worry about that. If you are quick, you can see the maximum current, or you can use a ballistic ammeter (which sticks at the highest measurement). From this info you can find the internal resistance of the batteries. Add this to your own resistance, and divide 2000 V by the total resistance. This should be fairly close, although you should know that there is a big difference between 0.1 amps running across your skin (ouch) and running through your chest (ugh!ack!). There is also additional resistance from the air, if it jumped across, but with sufficient ionization it is surprisingly low.
So why do I know so much about this? I used to work in a lab with lots of high voltage. I've had a few "incidents". I've had to run this calculation before. '180,000 V' divided by 'Dave' = "OMG! Did I just shoot a lighting bolt out my ass? Fsck that hurt!".
Reminds me of the time I was trying to make a centrifuge, and I thought it would be good to test it first by mounting a Frisbee to the motor. I was using a 1 hp Alcatel vacuum pump motor (~30,000 rpm) in a vacuum (about 1E-3 torr). The Frisbee disintegrated nearly instaneously. I was picking little pieces of purple plastic out of the vacuum chamber for the next hour. I decided not to build that centrifuge. Hmm, chunks of steel at 1800 km/hr... It was just a little too scary for me.
I'm afraid it doesn't work quite like that. You see, gamma ray detectors (and most other detectors of ionizing radiation) detect the ionization produced by a ray passing through a material. The gamma ray passes through a material (in this case, a germanium crystal I believe) and knocks a few electrons around. That current is then collected, and by knowing the size and location of a pulse of current, they can determine the size and location of the photon which passed through. If you were to reverse the process, you could get some electrons to move around, but you couldn't make them dance in the exacting pattern which would be required to emit a bunch of photons which would combine to make a high energy gamma ray. It is less like turning a microphone into a speaker than it is like trying to get a thousand microphones to reproduce a sound a mile away, as if it had been produced at that point. In other words, it is theoretically possible to create a gamma ray by combining multiple ionizations, but only if you can control where those ionizations occur down to a nano-, maybe even pico- meter resolution. Generally, the best way to create a gamma ray is to ram two nuclei together at very high speed. Basically the same method the hulk uses...
I looked, but I couldn't find a full article online. I did find an abstract for an oral presentation back in November, and of course, the issued patent is available at uspto.gov. New Scientist published an article on a similar technology a few months back. Sorry no links, but it's all easily Googleable.
It would have to raise an awful lot of money to do NEthing effectively. An average patent costs $5-6k, so if you are going to be filing patents to protect "free technology", then you are going to be burning through money very quickly. It's generally much more cost effective to place discoveries in the public domain, the old fashioned way. However, there might be a different use of such a FPF - call it the "American Technological Liberties Union". I'm picking that moniker for a reason: we have had a zillion postings to/. about bad patents which should not have been issued by USPTO in the first place. Well, those patents are just pieces of paper until someone violates them (say, by making a One-Click Purchasing website ala the infamous Amazon patent). So, what usually happens is the person who violates the improper patent gets sued, and often they do not have the money to defend themselves, and thus the improper patent stands. This is where the ATLU comes in. They provide legal defense for those people who are doing actual innovation, and even the playing field. The hard part, of course, is deciding which cases are proper to help defend. I sure wouldn't want the ATLU helping someone violating one of my patents.
Actually, I believe the story was referring to this . If you look in the methodology appendix in the aforementioned white paper, it refers back to this (or rather the previous year's version). The white paper discusses the benefits to a country's economy from dissuading piracy.
One of the major problems I see with the methodology is that it assumes that the rate of usage for a particular piece of software is the same in every country as it is in the US. I.e. if 4% of computers sold in the US use MATLAB, then 4% of the computer's sold in Vietnam must be using MATLAB, whether bought or pirated. Multiply the number of computers sold in Vietnam by 4%, subtract the number of copies of MATLAB sold in Vietnam, and the remainder must be pirated copies! They then conclude that countries which have a lower calculated rate of piracy have a better software industry. Now, if it happens to be that countries with a better software industry use MATLAB more, then it makes it look like countries that don't are pirates. This would also generate the conclusion that piracy means a bad software industry, but would be an artifact of the measurement methodology.
Note that I am only using MATLAB as an example app, and just because the methodology is poor doesn't mean that there isn't lots of copying in Vietnam.
My point was exactly that this is not a separate issue, as the parent post had said. You might note that your objections to the petition are the same kind of objections anyone would have to what is essentially a compromise/I-can't-win-the-fight-that-matters-but- maybe-I-can-get-this-passed kind of bill. I.e. "if we pass this, then they'll say we got what we wanted, and we won't get what we really want". I don't know what the best way to win a legislative battle is, but I thought it would be good to at least show some support for those people who are fighting to keep copyrights to a reasonable time limit. I think there are some problems with the plan (please read the post regarding photography - an excellent point), but Eldred and Lessig are at least trying to help solve a problem, which is more than I do politically.
Speaking as someone who has put literally thousands of hours into building a deuteron collider, why should you get life+50 years, and I get 20 years? Inventors lose their rights after a limited time, and rightly so. Inventors have to pay fees to keep their patents from being considered 'abandoned'. What makes your 1000's of hours of work worthy of more time than mine? Aren't a few decades enough time for you to, in slashdot-ese, "4. Profit!!!" ?
Slashdot Mirror
It seems that we have a number of intelligent, articulate punks on slashdot today, which is pretty cool, IMHO. Of course, there are always the hardcore ones, like AC parent's post (not sure if serious or not). It reminds me of what a punk friend of mine said once:
"You're not punk unless you've had scabies!".
Of course, really there are lots of different kind of punks. I used to know this really hot little punk chick in Savannah named Kitty who knew more about music than god and lived homeless for a year "just to see what it was like". Was she punk? Hell yeah! Did she have scabies? I hope not! (scratches crotch)
Or "Multidata"!
Deaths in Panama
Disclosure: I work for a manufacturer of treatment plan verification devices. It never hurts to actually ~check~ to see that the software is working as spec'ed.
Uh, two words: Smoot Hawley.
Read some history
Well, sort of. A Carnot engine, even one which uses photons as its working fluid, must return to its original state. A solar sail "expander/compressor" like you discuss would technically only be one-half of a Carnot engine. To incorporate the rest, you either have to let the photons escape (that's easy), or turn off the sun for part of the cycle (that's hard).
The Steady Flow analysis is more correct, but is not an analysis of a Carnot cycle. However, I should point out that the tiny red-shift in the photons is not a sign of a tiny energy efficiency, but rather of a small delta energy per photon collision. Given infinite space to expand in, a very large percentage of the energy of the photon gas can be collected (as the temperature difference between the sun (6000 K) and empty space (3 K) is fairly large. It's just that you have to expand your volume by a large amount to get it, and the differential with respect to the volume is very small.
Basically, we're all saying the same things here. There are always fifty gazillion ways of looking at any physics problem. But Gold's analysis is wrong.
You are correct, but just a nitpick:
Elastic scattering ~is~ thermodynamics, when applied to any large ensemble of particles.
You can apply thermo just about anywhere in physics.
If the mirror were 100% efficient, which is physically impossible, then the light would remain bouncing around in the sphere. However, if the mirror were 99.99999% efficient, then very quickly the light in the mirror would become black-body radiation. What you have described is essentially a blackbody cavity. Blackbody radiation is basically light whose frequency distribution is determined by temperature - in this case by the temperature of the inside of the sphere. So if you were to open up your hole again and let the light out after having been in there for a few fractions of a second, it would have a blackbody distribution corresponding to a temperature equal to the temperature of the sphere before you put in the light, plus the increase in temperature associated with the light being partially absorbed (or a decrease in temperature, if the sphere starts out at a higher temperature than the light).
You are correct that the Carnot efficiency cannot be calculated for this case, as it is not returning to it's original position. However, in the postulated case of a perfect mirror, there is no heat sink, as the photons will be reflected back towards the sun, and not radiated from the back of the sail. If the photons are absorbed by the sail, then some are radiated to the heat sink, and the expansion is no longer adiabatic (which is consistent with the lower momentum transfer). Note that if the mirror ~was~ returned to its original position, and the sun was insulated against losses in directions other than towards the sail, you would have an adiabatic expansion and then compression of the photons, leaving you with no net change in energy.
Gold complains in his paper of physicists not treating photons thermodynamically. That's funny - I seem to remember working out a problem using an adiabatic expansion of a photon "gas" in my undergraduate days. I don't remember the equation of state off the top of my head, but I guarantee you can find it in Callen or any other thourough thermo book.
Yes, IAAP. I also think that slashdotters should note that this was published in the Arxiv, which is NOT a peer reviewed publication (although I must say that the Arxiv rocks!). The Arxiv is sort of like an open source scientific journal, or a BBS for scientific papers. I highly recommend wandering around in it for a few hours, but remember to take everything in there with a grain of salt.
Darn. I was going to try NOT posting to slashdot today. Oh, well. Feed the addiction (sticks needle labeled "/." in arm).
Most of NASA's work is already available publicly. Try the third floor of the FIT library. There's some amazing stuff in there. That's where I first found out about NERVA, and also how the Shuttle's configuration was decided upon in 1968 (before we landed on the moon).
I realize that it's about as useless as complaining about the press referring to crackers as hackers, but:
Technology != IT !!!!!
Those of us who work in technological fields ~outside~ of computing/telecom get a little annoyed when people use the term "Tech sector" or "Tech spending" to refer to only the IT sector. If you mean "Information Technology", call it that, or use the handy term "IT". Please don't co-opt the word Technology to only mean your little bits and bytes. Rockets, airplanes, oil-wells, nuclear submarines and medical breakthroughs also involve a little bit of "Technology" too, and it's annoying when analysts refer to the companies who make these things as not being "Tech companies". We can't help if the press is stupid, but this is Slashdot - we are Techie nerds and should know better.
Yes, that would be a problem, if the purpose of the Bill were to put works in the future into public domain. However, this bill was created to fight the ~retroactive~ extension of copyrights from >50 years ago. If there is anything I don't like about the bill, it is that it is adding a fee retroactively, something I'd be pissed about if it was foisted on me. But I understand and approve of what the Bill proposes: that retroactively extended copyrights have a retroactive fee imposed upon them.
You see, the author of "The Scandalous Hussy" can't go back to 1937 to prepay the fee on his bodice-ripping pulp novel, so if he doesn't pay the fee now, then it becomes public domain. THAT is the purpose of the bill.
Looks very cool, and the price is actually rather good IMHO for a little guy like that. I've always wanted to use something like this for building a robot. It's a perfect size.
But first, let's give it a real-world test: a good old-fashioned Slashdotting! I mean, what would it say if a server company can't handle being slashdotted?
Good so far.
Last week, Sen. Hatch made an outrageous suggestion for a bill to allow copyright holders to destroy file-sharer's PCs . Some people thought this was just a spurious bill to take the heat off of the "real dangerous" laws that would then be proposed, which might seem more "rational".
Apparently this is the real bill.
So, please tell me what is rational about this? Yes, distributing materials without the permission of the copyright owner is illegal. We already have laws and civil penalties for this. This may seem like a good law (in the same way that if we had a problem with lots of windows being broken, the FBI assigning more agents to a Broken Windows Units would seem reasonable), but in fact, it is not. If I find someone violating one of my patents, I sue them, hopefully I win, and they pay me recompense or the Sherrif comes and takes their car. This is how it works. I can't expect the FBI to go around looking for people violating my patents, gathering evidence at taxpayer expense, and then handing all the information over to me.
If they are to do so, they ought to do this service for everybody. Somehow I get the feeling they aren't going to be worried about my IP, or the IP of my friends with the Indy-band website. They are going to be protecting ONLY the big money, RIAA/MPAA IP. If you don't believe this, look at recent history. This is unfair and wrong. Yes, the RIAA and MPAA are suffering from massive violations of their IP rights. But to spend tax monies on agents specifically dispatched to police their IP is unfair to other IP holders, as well as the taxpayers. It is essentially a subsidy to the legal expenses of the RIAA and MPAA. Do we really want that? Let them try to work with the laws we have.
The MPAA and RIAA have a basic problem with their business model (they are basically in the same boat as each other). What they need to realize, is that in a world of near instaneous worldwide transmission and recording, once something is released, that's it, its out there. TV and radio have worked fine with this for years (few ever complained about people recording CHiPs and Knight Rider with their VCRs). Yet TV and radio made plenty of money. If the MPAA and RIAA want to make money, they need to rework their distribution methods so that the choke-point is closer to the artist.
Until the MPAA and RIAA realize that they can do things a different way, they will keep trying to get the government to enforce their easily-violated property rights. The only way to make them change is to NOT make it easy for them to sue half of America. Make it as hard for them as it would be for you, or me.
As Thud457 so kindly pointed out, this is freshman physics. It should be in your physics texbook (if you don't have one, get one! or download this ). Basically, L=I*w , where L is the angular momentum, I is the moment of inertia, and w is the angular velocity. What does this mean? Well, if you want to see some serious precession etc., you want to have a high angular momentum. So spin something fast with lots of mass far from the center. Take a look at this: precession . I always found that bicycle wheels worked great - the only hard part is holding on to them, so I would suggest mounting the axle to something. For additional fun spin it up with a drill or small motor. Keep your duty factor low or you'll burn out the motor - drill motors are meant to spin fast, not slow.
I just checked out that textbook I linked to, and the angular momentum section suXors. Perhaps I ought to do an "Ask Slashdot" on Open Source Textbooks. Or would that be a dupe? I searched and didn't find NEthing covering physics textbooks. Hmm.
Good luck with your projects. I looked at your website and it looks like you are a true techie geek. Consider your hand shaken. Try not to catch fire.
Shortly after is right. I am amazed at how fast this meme spread. I was hearing that sick joke in the lunchroom at my school 20 MINUTES after the explosion. It might have had something to do with the fact that my school was within sight of the launch (30 miles south of the cape), so we saw the explosion with our own eyes, instead of on TV. Did the joke appear as fast elsewhere?
It was my twelfth birthday. I loved the shuttle when I was a kid; to me it represented science. But I know that we need to replace it with something better, cheaper, simpler. People have been saying "to kill the shuttle is to kill the space program" since I was a kid. Sorry, but the shuttle has already killed the space program. Or at least frozen it during my lifetime. As long as the shuttle flies, the politicians will not pony up money for a replacement system. If America has no space presence, the embarrasment will force them to fund a new system.
I mean jeez, I live in the economic blast radius of the Cape and I'm asking for this. My friends' Dads all lost their jobs in '86. This year, the shuttle loss didn't really effect the local economy, at least outside of Titusville. Why? Well, Space is not the growth industry on the Space Coast that it used to be. How sad is that?
Tell me, Mr. andersen , what good is source code if you are unable to comply with the GPL? ;)
Why do editors link to articles which don't tell you anything when they could just as easily link to the original site which doesn't tell you much more? I don't think that the BBC mentioned "Hybrid State Maser" or other remotely technical details... Trimprob
Actually I was doing something kind of weird. I wanted to use the centrifuge for separating a continuously-flowing liquid, so I was trying to make the centrifuge essentially out of tubing. I was going to use welded threaded connections, as I didn't think that swageloks would really cut it. I was really worried about the balancing, and that was the primary reason I decided not to attempt it. In addition the gravity drip design (drip in the top, separated liquids fly out at different height levels) would have made balance a possibly dynamic issue (ie not fun).
If you are just making a gyroscope, I would first take a look at what you are using it for. If you are just having fun/looking at gyroscopic effects, you don't really need high speed. A decently large inertial moment and a few rpm would do fine. Now if you are doing weird mad science stuff, I would need to know more to give any advice. But in general, if you are making a gyroscope, you want to have your mass more toward the edge. Anything big and heavy like you are describing should show decent gyroscopic motion, but be careful! 113 cu in of metal can pack a wallop!
Well, you can find out, to a good approximation:
The amperage is just the voltage divided by the resistance, as everybot is posting to this thread. So you need to find the resistance. There are two components to this resistance. One is you and one is the batteries. You can estimate your own resistance using an ohmeter, connecting it between the points on your body which touched the contacts. Note that this will slightly over-estimate your resistance, as the resistance of the human body decreases with increasing voltage (as do many objects). You can find the internal resistance of the batteries using an ammeter. Connect one contact from the batteries to the ammeter, then connect a wire with a known resistor in series to the other end. Make sure the resistor is large enough that the current level won't blow out your ammeter. Then connect the wire to the other end of the batteries. There may be a small plasma ball, but don't worry about that. If you are quick, you can see the maximum current, or you can use a ballistic ammeter (which sticks at the highest measurement). From this info you can find the internal resistance of the batteries. Add this to your own resistance, and divide 2000 V by the total resistance. This should be fairly close, although you should know that there is a big difference between 0.1 amps running across your skin (ouch) and running through your chest (ugh!ack!). There is also additional resistance from the air, if it jumped across, but with sufficient ionization it is surprisingly low.
So why do I know so much about this? I used to work in a lab with lots of high voltage. I've had a few "incidents". I've had to run this calculation before. '180,000 V' divided by 'Dave' = "OMG! Did I just shoot a lighting bolt out my ass? Fsck that hurt!".
Reminds me of the time I was trying to make a centrifuge, and I thought it would be good to test it first by mounting a Frisbee to the motor. I was using a 1 hp Alcatel vacuum pump motor (~30,000 rpm) in a vacuum (about 1E-3 torr). The Frisbee disintegrated nearly instaneously. I was picking little pieces of purple plastic out of the vacuum chamber for the next hour.
I decided not to build that centrifuge. Hmm, chunks of steel at 1800 km/hr... It was just a little too scary for me.
MonkeyBoyo,
I'm afraid it doesn't work quite like that. You see, gamma ray detectors (and most other detectors of ionizing radiation) detect the ionization produced by a ray passing through a material. The gamma ray passes through a material (in this case, a germanium crystal I believe) and knocks a few electrons around. That current is then collected, and by knowing the size and location of a pulse of current, they can determine the size and location of the photon which passed through. If you were to reverse the process, you could get some electrons to move around, but you couldn't make them dance in the exacting pattern which would be required to emit a bunch of photons which would combine to make a high energy gamma ray. It is less like turning a microphone into a speaker than it is like trying to get a thousand microphones to reproduce a sound a mile away, as if it had been produced at that point. In other words, it is theoretically possible to create a gamma ray by combining multiple ionizations, but only if you can control where those ionizations occur down to a nano-, maybe even pico- meter resolution. Generally, the best way to create a gamma ray is to ram two nuclei together at very high speed. Basically the same method the hulk uses...
"HULK SMASH!"
I looked, but I couldn't find a full article online. I did find an abstract for an oral presentation back in November, and of course, the issued patent is available at uspto.gov. New Scientist published an article on a similar technology a few months back. Sorry no links, but it's all easily Googleable.
It would have to raise an awful lot of money to do NEthing effectively. An average patent costs $5-6k, so if you are going to be filing patents to protect "free technology", then you are going to be burning through money very quickly. It's generally much more cost effective to place discoveries in the public domain, the old fashioned way. /. about bad patents which should not have been issued by USPTO in the first place. Well, those patents are just pieces of paper until someone violates them (say, by making a One-Click Purchasing website ala the infamous Amazon patent). So, what usually happens is the person who violates the improper patent gets sued, and often they do not have the money to defend themselves, and thus the improper patent stands. This is where the ATLU comes in. They provide legal defense for those people who are doing actual innovation, and even the playing field. The hard part, of course, is deciding which cases are proper to help defend. I sure wouldn't want the ATLU helping someone violating one of my patents.
However, there might be a different use of such a FPF - call it the "American Technological Liberties Union". I'm picking that moniker for a reason: we have had a zillion postings to
(Disclaimer: I am a patent holder)
Actually, I believe the story was referring to this . If you look in the methodology appendix in the aforementioned white paper, it refers back to this (or rather the previous year's version). The white paper discusses the benefits to a country's economy from dissuading piracy.
One of the major problems I see with the methodology is that it assumes that the rate of usage for a particular piece of software is the same in every country as it is in the US. I.e. if 4% of computers sold in the US use MATLAB, then 4% of the computer's sold in Vietnam must be using MATLAB, whether bought or pirated. Multiply the number of computers sold in Vietnam by 4%, subtract the number of copies of MATLAB sold in Vietnam, and the remainder must be pirated copies! They then conclude that countries which have a lower calculated rate of piracy have a better software industry. Now, if it happens to be that countries with a better software industry use MATLAB more, then it makes it look like countries that don't are pirates. This would also generate the conclusion that piracy means a bad software industry, but would be an artifact of the measurement methodology.
Note that I am only using MATLAB as an example app, and just because the methodology is poor doesn't mean that there isn't lots of copying in Vietnam.
My point was exactly that this is not a separate issue, as the parent post had said. You might note that your objections to the petition are the same kind of objections anyone would have to what is essentially a compromise/I-can't-win-the-fight-that-matters-but- maybe-I-can-get-this-passed kind of bill. I.e. "if we pass this, then they'll say we got what we wanted, and we won't get what we really want". I don't know what the best way to win a legislative battle is, but I thought it would be good to at least show some support for those people who are fighting to keep copyrights to a reasonable time limit. I think there are some problems with the plan (please read the post regarding photography - an excellent point), but Eldred and Lessig are at least trying to help solve a problem, which is more than I do politically.
Speaking as someone who has put literally thousands of hours into building a deuteron collider, why should you get life+50 years, and I get 20 years? Inventors lose their rights after a limited time, and rightly so. Inventors have to pay fees to keep their patents from being considered 'abandoned'. What makes your 1000's of hours of work worthy of more time than mine? Aren't a few decades enough time for you to, in slashdot-ese, "4. Profit!!!" ?