Once upon a time, publishing was expensive and risky. Printing the manuscript of sheet music, or cutting the master for a record (old-style) and stamping a few thousand cost money. If they didn't sell, the entrepreneur who paid forthem lost money. So he was justified in taking a goodly slice when it came good.
But publishing audio is now cheap and low risk. So it doesn't justify extortionate profits.
But the artist had to work just as hard - or not - as s/he ever did. And deserves the rewards just as much as ever. So the rewards of touring should go back to the artist.
Of course, some of the rewards of touring are not due solely to the artist. Mr Dibbler and friends will no doubt have paid a bit to printthe T-shirts, posters etc. and are entitled to some share of the cut. But it is by no means obvious that these are the same people who arrange the creation and shipping of CDs.
Artists need to relaim their products from the publishers. Once upon a time, the publishers earned their retirn. No more. But it takes organisation - the first artist to try it will be dropped. But the big labels are no longer, in the ager of net publishing, contributing to the glory of music -and don't deserve the profits they got in the past.
There are lots of guesses about this. They are, as yet, guesses. Since, self-evidently, homosexuality has evolved out, and yet homosexuals are undoubtedly reproductively disadvantaged (though not as much as might be believed), there must be some compensating advantage.
One thing to note is that homosexuals seem to be disproportionately represented in the creative arts. That might be because such areas of society are more tolerant of unconventional behaviour. Or it might be that there is some correlation between homosexuality and creativeit - and hence income, and hence the ability to support wives (for reproduction, not love) and children.
Another theory is that one copy of the hypthetical homosexual gene makes its posessor more sensitive, and hence a better seducer, while two copies make them homosexual. Like the famous sickle cell anaemia gene, the advantages of a single copy outweigh the disadvantages of two.
All these are Just So Stories. They might be true - or not. But, while we cannot yet tell if any of them is the truth, we can be reasonably certain that there is some advantage to genes "for" homosexuality, simply from the pesistence of the feature.
Except that this doesn't happen to liquid enclosed in a membrane - e.g. skin. The USAF have tried it: if you preload your bloodstream with oxygen, you can survive for a couple of minutes in near-vacuum. Arther C Clarke included this in some stories. The only uncomfortable thing that happens before you die of oxygen starvation is your eyeballs dry up.
Of course, if you want to have the luxury of breathing, you need to have some air pressure in your lings. And your chest isn't strong enough to hold any significant overpressure, so your chest will burst open if you hold your breath, and you will die of asphyxiation if you don't. In the fullness of time, your corpse will be vacuum-dried - but you won't be worrying about it by that time.
Simply: agreed. The voting process should be open. If the voting process includes software, that should be Open Software. Not from any OSS fanaticism, but because liberty depends upon democracy, and democracy depends upon trust. Unless voting systems are seen to be fair, we are all in deep trouble.
No. It is not for "fair use" - for review or academic purposes. It is the motive which counts, not the actual amount. There are rules of thumb that say that "a few pages" fall within fair use, but you have it the wrong way round. Resonable reviewers and critics can quote passages from a copyright work for the purpose of their review or criticism without breach of copyright. In this context, a few paragraphs wpould be "fair use", not a fixed number of pages.
Good, but not the killer app
on
Swiping Out Cancer
·
· Score: 2, Interesting
It took only few seconds of reflection before I decided this could be the killer biotech app which is needed for the dot-bio boom everyone keeps predicting someday
Sorry, I don't see it. It doesn't lead anywhere - it isn't the first of a class of devices. Obviously, if it works (lots of qualifiers in the article) it is an extremely good gadget. Many patients will benefit, and the inventors may well become justifiably rich. But apart from a sequence of improving models, all doing the same thing but steadily better, where does it lead to? It detects cancers - full stop. It detects them by detecting the nature of cncerous growth. So it won't do anything about anything else.
I don't want to knock it. $30,000 is cheap enough for every doctors surgery, and therefore for routine use any time there is a worry. If it is simple enough and safe enough, I could see them going into gyms etc, so you have a cancer check along with your fitness check. Even an optional sevice in airport departure loinges to while away those boring hours. (Hey - integrate it with the bomb scanners - get a free cancer check as the price of being scanned for explosives. Paranoia in a worthwhile cause).
99% true, but I think there is a special rule in the Patent Office that they will not hand out patents on perpetual motion machines unless you present a working model. Bot otherwise, though you exaggerate a little, the Patent Office works on the basis that if it is ofiginal, it will stand up when contested. An untested patent is more a statement of claim than a valid claim.
Most DNA is common, but there are some highly variable sections. Meny of them are just variable length repeats of the same code. If you jhave, at a certain place in the genome, 200 repeats of a particulare sequence, and I have 210, is that shared or not?
The way DNA testing works is to use an enxyme that snips the DNA at cerain codons, then sort the resultant fragments by length. Therefore, in your and my DNA, the fragment containing the sequencee I described above will be a differnt length and will be separated out.Since there are many such sequences in the genome, the chances of individuals other than identical twins haveing the same in all of them is negligible.
Sincec the differnt lengths are largely inherites, with only the odd one or two changing at each generation, there sill also be a considerable commonality between an individual and their bloood relatives.
If you have a large, fresh sample, DNA testing can unequivically say whether the sample did or did not come from a particlar person (or their identical twin). Problems sometimes occur because scene-of-crime samp;es may be old (DNA decays), small (just skin flakes) or ccorrupted (we all, including police officers, scatter our DNA around continually). Such samples are generally beter in steering the police than proving guilt.
Except that the guy pleaded guilty once arrested, so the DNA was not called in evidence.
But once they had arrested the guy, they had a sample of *his* DNA, which should be an exact match for the scene-of-crime DNA. The critical bit is the police working back through somebody else's DNA that they just happened to have on file.
No marketing hype allowed; we want only the facts.
You'll be lucky, with this kind of approach. The fact is that 98% of companies approached for this sort of thing will send out a salesman armed with the companies standard spiel. He may chuck in a bit of industry-wide background, but since all he knows how to do is to sell his companies kit, that is all he will do.
I would go the other way round. Find someone interesting and let him talk about whatever he wants to. One approach would be to write to the Cheif Engineer of a reasonably local company or division - by name, if you can - and ask if any of his development engineers could give a talk.
But go for the doers, not the presenters and sellers, if you can. I would rather hear from the guy who has been installing routers for 10 years on developments in networking than from the guy who has been selling them for 10 years.
I communicate with a major broadcaster, which is therefore a fairly high profile target for politically motivated hackers as well as mindless viruses. They have a flat no-attachments policy. If I want to send them a binary, I have to put it up on our website, then certain technically qualified people are permitted to download from the web. But the default applied to the majoprity of the people is no attatchments - full stop. I can't even send them zipped text or pdf.
Re:I don't have an answer, but...
on
RAID for Zero-G?
·
· Score: 2, Informative
Laptop drives have, according to a drive manufacturer, much higher shock tolerances than "normal" drives - whcih in turn are much better than preceding disks. Simply a matter of the components being lighter, but made of the same materials. Unless the storage-to-weight ratio came out really wrong, I would prefer laptop drives to desktop style.
Why should the mirror get hotter? It hasn't absorbed anything. We white/mirror coat things to protect them from radiation and keep thm cool. As I have posted elsewhere on the thread, such absorbtion as occurs is actually a sourcee of inefficiency of the system.
Ok, I'm sorry to seem old or non-progressive, but you CANNOT create a perpetual motion machine.
True - but the paper has used a broken argument. The statement If a heat engine could exceed the Carnot efficiency Then you could produce a perpetual motion machine but we know you cannot create a perperual motion machine Therefore no heat engine can exceed the Carnot efficiency. is true.
The statement The light sail is a heat engin and therefore cannot exceed the Carnot efficiency" is false, becasue a light sail is not a heat engin. A heat engine works on dis-ordered energy and must pay "Maxwells Price" - the wages of Maxwells Demon - to order it. A light sail works on ordered energy, for which maxwells Price has already been paid by the sun dumping energy into outer space.
Not an inert gast - it doesn't depend on the chemistry of the gas, only its physics. You have to use no gas - a hard vacuum, not the soft one these things usually have.
The light can only reflect losslessly when the sails are still (in a particular frame of reference). In the frame of reference of the bomb, as the sails accelerate they begin to redshift the photons a little bit at each bounce because the sail is moving, so the sail becomes less and less efficient. In the frame of the reference of the sail, it is the flash from the bomb which is becoming redder and redder and less and less efficient as it recedes faster and faster. Since the bomb produces a finite supply of photons, this setup gives a finit acceleration. The sun, however, produces an "infinite" supply of photons which are discarded (slightly reddened) after one use.
That is where we disagree. Photons carry momentum. Photon is turned through 180 degrees. Surely momentum is reflected through 180 degrees. If momentum of photon is changed, momentum of something els must also be changed - and the only obvious thing is the mirror.
You use another component of your movement - the orbital velocity. Navigiating in a gravity gradient is tricky for thoose not used to it. See Larry Niven't "The Integral Trees" for details. You don't use light pressure to go straight out. If you did, you would very soon reach a point where the return force of gravity pulled you back. Instead, you use it to increase your orbital velocity, thus causing you to fly outwards, or decreas it, thus causing you to fall inwards.
If you created a perfect vacuum - and people have done so - it does rotate in the correct direction. However, it has to be a good vacuum, and cheap gimmick shop gadgets don't achieve that, so the opposite effect works as you describe. It rotates in the light - that is good enough for a gadget.
Disagree. IWAP, when I left University. Thermally, the sail will heat up and will imet equal numbers of photons either side. There will therefore be, as the paper concedes, a short period while acceleration is higher as it absorbs photons until it reaches equilibrium. However, the disagreement is whther the final situation has residual thrust.
It doeds, because the important photons are those which are reflected. Hypothesize that the mirrore is perfect: 100% of all photons are reflected, none absorbed, and the mirror does not heat up at all. The paper would assert that the mirror therefore feels no force at all. And yet, on one side it is being battered by photons, whcih come in with a momentum vector one way and leave with the vector reversed. ISTM that this purely theoretical mirror must feel some force. The question is whether a real mirror can come close enough to the theoretical to get perceptible thrust. The thermal mechanism described is in fact a leakage mode of the system - a defect to be minimoised.
The fallacy is that a sail is a heat engine. It is not. Heat is disorganised energy - atoms flying around in random directions. Heat engines convert disorganised energy - the random motion of atoms - into organised energy. One example of such an engine is the Stirling engine, which converts hot gas into rotary motion - and obeys Carnot's law. Solar radiation is organised energy - and the sail converts one form of organised energy into another; it is a form of gearbox, if you will, and can approach 100% efficiency. The analog is to the sail, not the Stirling engine. A sailing boat can convert wind into movement as long as the wind lasts. (The fact that the wind is created by a heat engine is irrelevant - the wind is organised and they thermodynamic price has been paid before it reaches the sail.)
NO! Energy is NOT momentum. I takes energy to transfer momentum from one object to another, but they are fundamentally different concepts. Momentum is mv. Energy has many different forms, but even in its closest form to momentum, kinetic energy, it goes as v^2 not v. Confusing the two is responsible for a lot of misapprehensions 9such as that rockets won't work in a vacuum).
For most of us, that surely is the point. This is Slashdot, of course we are all Linux fans, of course we want to see SCO kicked into the long grass. But even if it were to turn out the "wrong" way, it were better done sooner than later. Just suppose SCOs allecagtions are true (I doubt this as much as most). IBM gets hit with massive damages - bad for IBM shareholdres but IBM, and they, will live. But SCO has revealed all the bits of GNU/Linux it believes to be ripoffs (it has to, in order to estimate the damages and to claim future royalties). So the Linux community cuts them out, does without some of them, and puts in a panic effort to do a cleanroom rewrite of those that are really necessary. I bet that if Torvalds, Stallman & Co. put out a "Save Our System" call, any really crucial bits of the system could be duplicated in three months.
And the Linux cimmunity could get back to growth as normal. This is because the FUD would have been dissipated. The harm being done by the SCO lawsuit hanging over GNU/Linux, and SCOs threatening letters, is far greater than the harm done by ripping out the offending code - if there is any. We, the Linux community, need a quick resolution.
In English law - I don't know about US law (and IANAL anywhere) - there is a duty on a plainiff in a civil case to take all reasonable steps to minimise any losses resulting from the harm being done to them. If you think I am infinging your copyright, you have a duty to tell me as soon as possible, not wait cackling while my potential fine piles up. If such an obligation exists in US law, SCO are not observing it. The cannot claim that every line of GNU/Linux is theirs. In fact, they cannmot claim that the fragnents allegedly stolen by IBM are crucial to the system, because it existed as a working system before IBM ever became involved. But they do claim that they have lost sales of their Unix product because Linux, incorporating their stolen code, is so good. It seems to me, therefore, that they have a duty to expose the code they allege to be stolen, and allow the Linux community to remove it. If their theory about the value of their code (if any) is true, Linux will drop in functionality and their sales will correspondingly recover; they may then claim for past, but not future, sales lost. In fact, I think that Linux would barely huccup. As I say, three months top level work by the community should repair all significant holes in the system.
So if anybody knows how to speed thes up, pleas tell. And for heavans sake, nobody do anything which could slow it down.
As stated many times abover, the processing power you have put in us way over the top. Think about the bandwidth. What are you ging to have to the net? 1 Mbit/sec? 5? A Scsi disk can deliver 500 Mbit/sec. Most of the web pages are static, so it is just scrape it off the oxide and send it down the link. Yes, there are some dynamic ones: how much processing is needed for them (run a test - I bet it isn't much)?.
Ram - well, you need at least 1/2 Gb, and the extra is not much.
Disks: you have put in 3 in a Raid 5. Do you really need that much space? 70 Gb disk for 250 users gives about 250Mb each - surely enough for email plus personal pages - most web accounts give 10Mb for personal pages, and few user fill them (does any body have experience with an ISP to comment on that?) And if your mail spool is in the 100Mb class, you are in trouble - or you exchange a lot of porn. I would have thoughtn2 disks in Raid 1 would do. And the only reason to go scsi is the greater reliability: Scsi gets 5 years warranty, IDE 1 - and that reflects in the build. And you can do soft raid, too, rather than spend money on a raid controller. On a sustem we built recenmtlyu, soft raid-1 was faster than hard raid, because of using a 32bit Scsi controller on a 64-bit busa.
Go for reliability. You want to leave a system that, once set up, runs forever. Overspec your PSU - PSUs like running about 50% load (but not too much - they don't like 10% load). Definitely overspec your fans - a $10 fan can quadruple the life of several $200 disks. Don't buy the cheapest kit in sight - try and get something with a bit more reliability built into the connectors etc. And, as already posted, have a backup solution as well as Raid. Put effort into making the backup process easy, and test and document the restore process (rember, it is probably your successor who will have to do it).
And spend any left-over money on bandwidth. That is what the net is about - bandwidth, not mips. Mips are a means to an end in web servers, and an excess is just wasted.
The Hindenberg fire was spectacular, but most of it came from the skin, which was varnished celluloid = one of the most flammable solids known. And approximately half the people on board it survived - which would be regarded as pretty good for an aviation accident resulting in fire and total hull loss for modern aircraft. It would be officially rated "survivable" today.
Hydrogen fuel has its dangers, but they are not necessarily greater than gasoline, just different. For example, gasoline spills and runs along the ground - hydrogen goes straight up. So with hydrogen you are much less likely to be surrounded by a pool of flames. Bacause it is lighter than air, it will dissipate quickly if there is any ventilation at all, making an explosive build up less likely (but not impossible, expecially under a roof. On the other end of the scales, a hydrogen flame is totally invisible, so that there is no indicator where a burning leak is except for when other things are destroyed. Gasoline advertises itself with a cheery glow of incandescent carbon particls on their way from gasoline to CO2.
Slashdot Mirror
Once upon a time, publishing was expensive and risky. Printing the manuscript of sheet music, or cutting the master for a record (old-style) and stamping a few thousand cost money. If they didn't sell, the entrepreneur who paid forthem lost money. So he was justified in taking a goodly slice when it came good.
But publishing audio is now cheap and low risk. So it doesn't justify extortionate profits.
But the artist had to work just as hard - or not - as s/he ever did. And deserves the rewards just as much as ever. So the rewards of touring should go back to the artist.
Of course, some of the rewards of touring are not due solely to the artist. Mr Dibbler and friends will no doubt have paid a bit to printthe T-shirts, posters etc. and are entitled to some share of the cut. But it is by no means obvious that these are the same people who arrange the creation and shipping of CDs.
Artists need to relaim their products from the publishers. Once upon a time, the publishers earned their retirn. No more. But it takes organisation - the first artist to try it will be dropped. But the big labels are no longer, in the ager of net publishing, contributing to the glory of music -and don't deserve the profits they got in the past.
There are lots of guesses about this. They are, as yet, guesses. Since, self-evidently, homosexuality has evolved out, and yet homosexuals are undoubtedly reproductively disadvantaged (though not as much as might be believed), there must be some compensating advantage.
One thing to note is that homosexuals seem to be disproportionately represented in the creative arts. That might be because such areas of society are more tolerant of unconventional behaviour. Or it might be that there is some correlation between homosexuality and creativeit - and hence income, and hence the ability to support wives (for reproduction, not love) and children.
Another theory is that one copy of the hypthetical homosexual gene makes its posessor more sensitive, and hence a better seducer, while two copies make them homosexual. Like the famous sickle cell anaemia gene, the advantages of a single copy outweigh the disadvantages of two.
All these are Just So Stories. They might be true - or not. But, while we cannot yet tell if any of them is the truth, we can be reasonably certain that there is some advantage to genes "for" homosexuality, simply from the pesistence of the feature.
Except that this doesn't happen to liquid enclosed in a membrane - e.g. skin. The USAF have tried it: if you preload your bloodstream with oxygen, you can survive for a couple of minutes in near-vacuum. Arther C Clarke included this in some stories. The only uncomfortable thing that happens before you die of oxygen starvation is your eyeballs dry up.
Of course, if you want to have the luxury of breathing, you need to have some air pressure in your lings. And your chest isn't strong enough to hold any significant overpressure, so your chest will burst open if you hold your breath, and you will die of asphyxiation if you don't. In the fullness of time, your corpse will be vacuum-dried - but you won't be worrying about it by that time.
Simply: agreed. The voting process should be open. If the voting process includes software, that should be Open Software. Not from any OSS fanaticism, but because liberty depends upon democracy, and democracy depends upon trust. Unless voting systems are seen to be fair, we are all in deep trouble.
No. It is not for "fair use" - for review or academic purposes. It is the motive which counts, not the actual amount. There are rules of thumb that say that "a few pages" fall within fair use, but you have it the wrong way round. Resonable reviewers and critics can quote passages from a copyright work for the purpose of their review or criticism without breach of copyright. In this context, a few paragraphs wpould be "fair use", not a fixed number of pages.
It took only few seconds of reflection before I decided this could be the killer biotech app which is needed for the dot-bio boom everyone keeps predicting someday
Sorry, I don't see it. It doesn't lead anywhere - it isn't the first of a class of devices. Obviously, if it works (lots of qualifiers in the article) it is an extremely good gadget. Many patients will benefit, and the inventors may well become justifiably rich. But apart from a sequence of improving models, all doing the same thing but steadily better, where does it lead to? It detects cancers - full stop. It detects them by detecting the nature of cncerous growth. So it won't do anything about anything else.
I don't want to knock it. $30,000 is cheap enough for every doctors surgery, and therefore for routine use any time there is a worry. If it is simple enough and safe enough, I could see them going into gyms etc, so you have a cancer check along with your fitness check. Even an optional sevice in airport departure loinges to while away those boring hours. (Hey - integrate it with the bomb scanners - get a free cancer check as the price of being scanned for explosives. Paranoia in a worthwhile cause).
99% true, but I think there is a special rule in the Patent Office that they will not hand out patents on perpetual motion machines unless you present a working model. Bot otherwise, though you exaggerate a little, the Patent Office works on the basis that if it is ofiginal, it will stand up when contested. An untested patent is more a statement of claim than a valid claim.
Most DNA is common, but there are some highly variable sections. Meny of them are just variable length repeats of the same code. If you jhave, at a certain place in the genome, 200 repeats of a particulare sequence, and I have 210, is that shared or not?
The way DNA testing works is to use an enxyme that snips the DNA at cerain codons, then sort the resultant fragments by length. Therefore, in your and my DNA, the fragment containing the sequencee I described above will be a differnt length and will be separated out.Since there are many such sequences in the genome, the chances of individuals other than identical twins haveing the same in all of them is negligible.
Sincec the differnt lengths are largely inherites, with only the odd one or two changing at each generation, there sill also be a considerable commonality between an individual and their bloood relatives.
If you have a large, fresh sample, DNA testing can unequivically say whether the sample did or did not come from a particlar person (or their identical twin). Problems sometimes occur because scene-of-crime samp;es may be old (DNA decays), small (just skin flakes) or ccorrupted (we all, including police officers, scatter our DNA around continually). Such samples are generally beter in steering the police than proving guilt.
Except that the guy pleaded guilty once arrested, so the DNA was not called in evidence.
But once they had arrested the guy, they had a sample of *his* DNA, which should be an exact match for the scene-of-crime DNA. The critical bit is the police working back through somebody else's DNA that they just happened to have on file.
No marketing hype allowed; we want only the facts.
You'll be lucky, with this kind of approach. The fact is that 98% of companies approached for this sort of thing will send out a salesman armed with the companies standard spiel. He may chuck in a bit of industry-wide background, but since all he knows how to do is to sell his companies kit, that is all he will do.
I would go the other way round. Find someone interesting and let him talk about whatever he wants to. One approach would be to write to the Cheif Engineer of a reasonably local company or division - by name, if you can - and ask if any of his development engineers could give a talk.
But go for the doers, not the presenters and sellers, if you can. I would rather hear from the guy who has been installing routers for 10 years on developments in networking than from the guy who has been selling them for 10 years.
I communicate with a major broadcaster, which is therefore a fairly high profile target for politically motivated hackers as well as mindless viruses. They have a flat no-attachments policy. If I want to send them a binary, I have to put it up on our website, then certain technically qualified people are permitted to download from the web. But the default applied to the majoprity of the people is no attatchments - full stop. I can't even send them zipped text or pdf.
Laptop drives have, according to a drive manufacturer, much higher shock tolerances than "normal" drives - whcih in turn are much better than preceding disks. Simply a matter of the components being lighter, but made of the same materials. Unless the storage-to-weight ratio came out really wrong, I would prefer laptop drives to desktop style.
Why should the mirror get hotter? It hasn't absorbed anything. We white/mirror coat things to protect them from radiation and keep thm cool. As I have posted elsewhere on the thread, such absorbtion as occurs is actually a sourcee of inefficiency of the system.
Ok, I'm sorry to seem old or non-progressive, but you CANNOT create a perpetual motion machine.
True - but the paper has used a broken argument. The statement
If a heat engine could exceed the Carnot efficiency
Then you could produce a perpetual motion machine
but we know you cannot create a perperual motion machine
Therefore no heat engine can exceed the Carnot efficiency.
is true.
The statement
The light sail is a heat engin and therefore cannot exceed the Carnot efficiency"
is false, becasue a light sail is not a heat engin. A heat engine works on dis-ordered energy and must pay "Maxwells Price" - the wages of Maxwells Demon - to order it. A light sail works on ordered energy, for which maxwells Price has already been paid by the sun dumping energy into outer space.
Not an inert gast - it doesn't depend on the chemistry of the gas, only its physics. You have to use no gas - a hard vacuum, not the soft one these things usually have.
The light can only reflect losslessly when the sails are still (in a particular frame of reference). In the frame of reference of the bomb, as the sails accelerate they begin to redshift the photons a little bit at each bounce because the sail is moving, so the sail becomes less and less efficient. In the frame of the reference of the sail, it is the flash from the bomb which is becoming redder and redder and less and less efficient as it recedes faster and faster. Since the bomb produces a finite supply of photons, this setup gives a finit acceleration. The sun, however, produces an "infinite" supply of photons which are discarded (slightly reddened) after one use.
Reflection can't provide momentum
That is where we disagree. Photons carry momentum. Photon is turned through 180 degrees. Surely momentum is reflected through 180 degrees. If momentum of photon is changed, momentum of something els must also be changed - and the only obvious thing is the mirror.
You use another component of your movement - the orbital velocity. Navigiating in a gravity gradient is tricky for thoose not used to it. See Larry Niven't "The Integral Trees" for details. You don't use light pressure to go straight out. If you did, you would very soon reach a point where the return force of gravity pulled you back. Instead, you use it to increase your orbital velocity, thus causing you to fly outwards, or decreas it, thus causing you to fall inwards.
If you created a perfect vacuum - and people have done so - it does rotate in the correct direction. However, it has to be a good vacuum, and cheap gimmick shop gadgets don't achieve that, so the opposite effect works as you describe. It rotates in the light - that is good enough for a gadget.
Disagree. IWAP, when I left University. Thermally, the sail will heat up and will imet equal numbers of photons either side. There will therefore be, as the paper concedes, a short period while acceleration is higher as it absorbs photons until it reaches equilibrium. However, the disagreement is whther the final situation has residual thrust.
It doeds, because the important photons are those which are reflected. Hypothesize that the mirrore is perfect: 100% of all photons are reflected, none absorbed, and the mirror does not heat up at all. The paper would assert that the mirror therefore feels no force at all. And yet, on one side it is being battered by photons, whcih come in with a momentum vector one way and leave with the vector reversed. ISTM that this purely theoretical mirror must feel some force. The question is whether a real mirror can come close enough to the theoretical to get perceptible thrust. The thermal mechanism described is in fact a leakage mode of the system - a defect to be minimoised.
The fallacy is that a sail is a heat engine. It is not. Heat is disorganised energy - atoms flying around in random directions. Heat engines convert disorganised energy - the random motion of atoms - into organised energy. One example of such an engine is the Stirling engine, which converts hot gas into rotary motion - and obeys Carnot's law. Solar radiation is organised energy - and the sail converts one form of organised energy into another; it is a form of gearbox, if you will, and can approach 100% efficiency. The analog is to the sail, not the Stirling engine. A sailing boat can convert wind into movement as long as the wind lasts. (The fact that the wind is created by a heat engine is irrelevant - the wind is organised and they thermodynamic price has been paid before it reaches the sail.)
NO! Energy is NOT momentum. I takes energy to transfer momentum from one object to another, but they are fundamentally different concepts. Momentum is mv. Energy has many different forms, but even in its closest form to momentum, kinetic energy, it goes as v^2 not v. Confusing the two is responsible for a lot of misapprehensions 9such as that rockets won't work in a vacuum).
Hey - you've been reading Starship Troopers
When do the legal festivities kick off?
For most of us, that surely is the point. This is Slashdot, of course we are all Linux fans, of course we want to see SCO kicked into the long grass. But even if it were to turn out the "wrong" way, it were better done sooner than later. Just suppose SCOs allecagtions are true (I doubt this as much as most). IBM gets hit with massive damages - bad for IBM shareholdres but IBM, and they, will live. But SCO has revealed all the bits of GNU/Linux it believes to be ripoffs (it has to, in order to estimate the damages and to claim future royalties). So the Linux community cuts them out, does without some of them, and puts in a panic effort to do a cleanroom rewrite of those that are really necessary. I bet that if Torvalds, Stallman & Co. put out a "Save Our System" call, any really crucial bits of the system could be duplicated in three months.
And the Linux cimmunity could get back to growth as normal. This is because the FUD would have been dissipated. The harm being done by the SCO lawsuit hanging over GNU/Linux, and SCOs threatening letters, is far greater than the harm done by ripping out the offending code - if there is any. We, the Linux community, need a quick resolution.
In English law - I don't know about US law (and IANAL anywhere) - there is a duty on a plainiff in a civil case to take all reasonable steps to minimise any losses resulting from the harm being done to them. If you think I am infinging your copyright, you have a duty to tell me as soon as possible, not wait cackling while my potential fine piles up. If such an obligation exists in US law, SCO are not observing it. The cannot claim that every line of GNU/Linux is theirs. In fact, they cannmot claim that the fragnents allegedly stolen by IBM are crucial to the system, because it existed as a working system before IBM ever became involved. But they do claim that they have lost sales of their Unix product because Linux, incorporating their stolen code, is so good. It seems to me, therefore, that they have a duty to expose the code they allege to be stolen, and allow the Linux community to remove it. If their theory about the value of their code (if any) is true, Linux will drop in functionality and their sales will correspondingly recover; they may then claim for past, but not future, sales lost. In fact, I think that Linux would barely huccup. As I say, three months top level work by the community should repair all significant holes in the system.
So if anybody knows how to speed thes up, pleas tell. And for heavans sake, nobody do anything which could slow it down.
As stated many times abover, the processing power you have put in us way over the top. Think about the bandwidth. What are you ging to have to the net? 1 Mbit/sec? 5? A Scsi disk can deliver 500 Mbit/sec. Most of the web pages are static, so it is just scrape it off the oxide and send it down the link. Yes, there are some dynamic ones: how much processing is needed for them (run a test - I bet it isn't much)?.
Ram - well, you need at least 1/2 Gb, and the extra is not much.
Disks: you have put in 3 in a Raid 5. Do you really need that much space? 70 Gb disk for 250 users gives about 250Mb each - surely enough for email plus personal pages - most web accounts give 10Mb for personal pages, and few user fill them (does any body have experience with an ISP to comment on that?) And if your mail spool is in the 100Mb class, you are in trouble - or you exchange a lot of porn. I would have thoughtn2 disks in Raid 1 would do. And the only reason to go scsi is the greater reliability: Scsi gets 5 years warranty, IDE 1 - and that reflects in the build. And you can do soft raid, too, rather than spend money on a raid controller. On a sustem we built recenmtlyu, soft raid-1 was faster than hard raid, because of using a 32bit Scsi controller on a 64-bit busa.
Go for reliability. You want to leave a system that, once set up, runs forever. Overspec your PSU - PSUs like running about 50% load (but not too much - they don't like 10% load). Definitely overspec your fans - a $10 fan can quadruple the life of several $200 disks. Don't buy the cheapest kit in sight - try and get something with a bit more reliability built into the connectors etc. And, as already posted, have a backup solution as well as Raid. Put effort into making the backup process easy, and test and document the restore process (rember, it is probably your successor who will have to do it).
And spend any left-over money on bandwidth. That is what the net is about - bandwidth, not mips. Mips are a means to an end in web servers, and an excess is just wasted.
The Hindenberg fire was spectacular, but most of it came from the skin, which was varnished celluloid = one of the most flammable solids known. And approximately half the people on board it survived - which would be regarded as pretty good for an aviation accident resulting in fire and total hull loss for modern aircraft. It would be officially rated "survivable" today.
Hydrogen fuel has its dangers, but they are not necessarily greater than gasoline, just different. For example, gasoline spills and runs along the ground - hydrogen goes straight up. So with hydrogen you are much less likely to be surrounded by a pool of flames. Bacause it is lighter than air, it will dissipate quickly if there is any ventilation at all, making an explosive build up less likely (but not impossible, expecially under a roof. On the other end of the scales, a hydrogen flame is totally invisible, so that there is no indicator where a burning leak is except for when other things are destroyed. Gasoline advertises itself with a cheery glow of incandescent carbon particls on their way from gasoline to CO2.