You are technically correct: the projectile can go no faster than the speed of sound in the gas; the part you forget is that sound travels faster and faster as the pressure of the medium (gas) increases.
And you are technically incorrect.;-)
The speed of sound in an ideal gas doesn't depend on the pressure, but only on the molecular mass and on the temperature.
Your comment reminds of the people harping about the ethics of attorneys.
Attorneys are not out for justice. They are out to advocate for their client's interests. That is the ethical code to which they are supposed to adhere, and they are only bad if they don't do that.
Soldiers are supposed to learn how to wage war, and, when appropriate, to actually wage war. Heinous war crimes aside, a soldier is only bad if he doesn't practice and actually wage war to the best of his ability.
The morality decisions (again, apart from clear crimes against humanity) are made at a higher level. In the US, it is congress and the president that decide when to use military force.
So, in general, eager troops are good, provided that they have good discipline up the chain of command.
It is theoretically impossible for an air-powered gun to launch a projectile faster than the speed of sound.
I believe the root of it all is that the gas cannot move down the barrel faster than the RMS speed of a molecule of the gas. So, unless you use a hot gas, or a light one (helium?) you won't exceed the speed of sound.
I used to work for Supershuttle, a van service that transports people to and from the airport. In my case, I was taking people to and from the San Francisco airport. One place we serviced was Treasure Island, then a Naval Base. I always asked the sailors what they did for the Navy. Almost every single one was a shipboard firefighter.
After a while, I came to the conclusion that there are probably a lot of shipboard fires during naval combat.
So, my point is, is it such a good idea to reduce the complement from 300 to 90?
But what do I know. I'm just a shuttle driver. Or I was just a shuttle driver, anyway.
Don't get me wrong, i think what this guy is talking about is fascinating, but i also think it's got more of a place in some theoretical branch of math than in real life development.
Actually, I think HE sees it as something that has limited utility in real life development, too. I think he's just trying to emphasize that things such as disk files are computer science constructs, and there MAY be Another Way. From the interview, I get the impression that his underlying fear, though, is that a dogmatic CS curriculum with in-curious students will fail to discover the Next Great Idea in computer science.
On the specific case of files, one thing he may be discounting, however, is that we ended up with disk files by choice. I'm not sure what the criteria were for making the decision, but other ways of arranging data on a magnetic disk (and tape) were used in the old days, and somehow, files and file systems ended up ruling the day. It may just be a waste of time to try the old ideas again. I mean, you wouldn't build a square wheel just because you think that we may have settled too quickly on round ones...
Anyway, this thread is dead, so I'm probably wasting my keystrokes.
This means that natures has got an excellent error catching and correction system, rather than letting buggy code run and produce flawed result it catches the worst cases and prevent them from running (spontaneous abortion) while code with less bugs (say, a congenital disease) has less chance to run (early death, lesser sexual attractiveness to mates...).
Just thought I'd point out that mutation is the ultimate source of genetic variation, which, when kept within certain limits, allows species to adapt to changing environments. So, in order for the whole system of evolution to work, a certain amount of genetic error is required.
So a diesel submarine should be almost as efficient as a surface ship, but a nuclear submarine will be less efficient (but will travel faster than diesel subs due to raw power)
I doubt that this is true. First of all, travelling below the surface is much different than travelling on the surface, planing or not.
There is a concept in marine architecture called hull speed. Basically, the speed of a non-planing boat is sort of fixed, irrespective of power, at some value which goes up as the square of waterline length. Near this hull speed, as you apply more power to increase in speed, you just make a bigger and bigger wake, but don't really move much faster.
In a planing hull, as you apply more power near hull speed, the boat sort of pops up off the surface of the water and begins to go much faster. It is no longer floating, but, more skimming on the surface. All fast boats that are small plane. It is just impossible to go fast without planing in a small boat.
For a submarine, there is no hull-speed issue. Subs can go faster and faster as they apply more power. I believe that nuclear submarine top-speed is classified, but I have heard lots of people say that they can do 60 knots. (1 knot ~= 1.15 mph). I doubt that even an aircraft carrier can do 60 knots. In fact, designing a boat to go 60 knots on the surface of the ocean (not a lake) is a very difficult task.
When you travel on the surface of the ocean, you have to deal with waves and wind, which become much more formidable as speed increases. A moderate sea is shaped like gentle sand-dunes, although the dunes are constantly shifting and morphing beneath you. A heavy sea (as in a storm) is more like a rock field or something in shape. The wave crests are much closer together, and the motion is much more violent. The waves can easily reach heights of 10, 20 or 30 feet, with crests perhaps 100 feet apart. If you haven't experienced it, it is hard to comprehend just how violent it is. I doubt very much any boat short of a few hundred feet can even go more than 30 or 40 miles an hour in this environment.
A submerged craft can travel serenely below all this. I imagine there is a bit of turbulence, but nothing like the chaos and danger of the surface.
Another perspective on all this is the difference between ducks and fish. Small tuna and jacks can easily hit 30 knots. I have seen them jump out of the water going this fast. Spinner dolphins can hit similar speeds. I have heard some people claim that big tuna can hit 40 or 50 knots. I don't know if this is true. Ducks can go about 2 knots.
The bottom line, I think, is that a low drag body can travel much faster submerged than a floating body of similar size, no matter what the shape. This is especially true when the surface of the sea is rough. Surface craft with very long waterlines MAY be just as efficient, I don't know.
The biggest reason for the damage an SUV causes in a collision with a normal car is the disparity in bumper height. Look carefully at normal cars: notice how the front and rear bumpers all line up? That's due to regulation - regulations which the SUVs don't have to conform to.
You are definitely right about the disparity in bumper height, but, actually, even regular car bumpers don't line up that well during heavy breaking. (And most accidents occur during heavy breaking. I mean, if you are about to crash, what else would you do besides hit the breaks?).
The front bumper dives several inches due to suspension compression, and the rear bumper goes up. That is why the most typical accident, the freeway rear-ender, often results in hood damage to the car in back. In fact, it would probably be a good idea to mandate either higher bumpers in front, or lower bumpers in back.
If everyone drove
Japanese/European passenger sedans, the roads would be significantly safer than they are now, since those cars routinely score the highest on IIHTS/NHTSA crash tests and don't endanger other drivers/passengers. [emphasis added]
I basically agree with you, but I'm not sure there's anything wrong with American passenger sedans from a safety perspective. Many people, especially on the west coast, think American cars are ugly or poorly made, but I don't think it is fair to say that they suffer from a true saftey problem.
On the other hand, big SUV's that are really just trucks do have a slight safety problem because they have a non-deformable truck chassis and high center of gravity. When they crash into lighter vehicles, the lack of a deformable bumper/crumple zone is not so bad (for the SUV) but in other accident scenarios, the lighter, lower, deformable car is definitely better. For example, if you crash into a big tree at 35 MPH, you'd be much better off doing it in a Honda Civic than in a Chevy Suburban. And if you get side-swiped or hydroplane and lose control of your vehicle, you are less likely to flip in a low center of gravity car than in a big truck-type SUV.
I wasn't aiming it at SWT, it was just a general comment about all cross-platform toolkits that use native widgets (note that
using non-native widgets, a la Swing solves this problem). [emphasis added]
Hmm. A counter-example. OK, I withdraw my allegation of off-topicness. Swing is, by all accounts, VERY consistent across platforms, and is about as cross-platform as you are likely to get. The only hassle, then, (for some people,) is the Sun controlled IP, etc.
I[t] would be faster, but the main problem with SWT on the Unix side is, face it, GTK2. According to the Eclipse newsgroup archive, the developers ran into myriads of small problems beginning from the container layout handling to implement a z-ordering of components on top of GTK2 in eclipse because GTK2 either does it differently or does it none at all. No wonder that performance is dragged down. If you look at the windows side, things are quite different and eclipse is blazingly fast.
Well, just for the sake of completeness, I should mention that in the *nix world, you can choose from the gtk version and the motif version of SWT.
This is a fundamental problem with cross-platform development using layout managers.
It isn't a criticism particular to SWT. Since the original post specifically asked about cross-platform GUI's, I think your criticism is out of place (off-topic) quite frankly.
We still haven't seen any unbiased studies on the effects of cellular phones on the brain (where people hold their phones while talking) and the reproductive organs (where they keep them when they're not).
I am going to call you on this. Where is a biased study? How was it flawed and how would you have done it differently?
Personally, I believe that if there are any hazards to humans from cell phone RF emissions, they are very slight, otherwise it would be easy to find them conclusively in a well-designed study.
And, if, perchance, you can't back up what you are saying, then please stop saying it.
It turns out that what matters is the dielectric constant of the medium in which the electric wave travels.
In the case of wireless, that medium is air, which has a dielectric constant very nearly the same as free space (vacuum).
But electrical signals travelling in twisted pair wire (like category 5 cabling) travel a bit slower because the dielectric material they are travelling in is really the insulation in the wire. That's right, the signal is really travelling in the dielectric, not in the wires, per se.
So the speed of propagation doesn't depend on the properties of the wire conductor, but on the dielectric in between the two conductors.
You can calculate the speed if you know the relative permitivity of the dielectric. This is very closely related to the index of refraction, by the way.
Anyway, in most practical situations (i.e., in non-magnetic materials) the velocity equals the free-space speed of light divided by the square root of the relative permitivity of the dielectric. So in typical fiberglass circuit board, called FR4, where the '4' represents the relative permitivity, the speed of light is C/sqrt(4), or about half the free-space speed. Since the free-space speed is 300 Million meters per second, half of it is 150 million meters per second. You could also say that it is 150 meters per microsecond, or 0.150 meters per nanosecond, or 150 mm/ns.
But this is really only true for signals which are not on one of the surface layers. Surface layer signals experience a medium partially of FR4, and partially of air, so they travel a little faster.
I don't think it is fair or makes much sense to lump all unices together with respect to kernel architecture. They are not all the same. I'm not really a kernel expert, but I know the different unices employed different techniques and came from substantially different code-bases.
Also, I would be interested in at least one and preferably a few example(s) of how the "aging paradigm" of UNIX is a major disadvantage to "OSS kernel hackers," as compared to Microsoft NT/2k hackers.
Also, it would be nice to see how this disadvantage or these disadvantages affected the Mac OS 10.2 hackers as well.
MM --
Re:I am sooooooo tired of plastic!!!
on
Waterproof Books
·
· Score: 1
Actually, the last time I checked, both aluminum and glass containers were VERY recycleable, in the sense that recycling them results in huge energy savings.
All other materials are highly questionable. When they "recycle" plastics, they mean, for example, that they shred them up and use them for filling outdoor furniture cushions or making synthetic building materials (for plastic fences and faux wood 2x4's and so on). They don't recycle plastic milk jugs into new milk jugs.
Steel (sometimes called tin) cans are not recycled in any meaningful way at all. I would suggest crushing them and keeping them in your own back yard, as some day they may be valuable to your progeny or your progeny's progeny.
MM --
Why plastic is good(was:I am so tired of plastic!)
on
Waterproof Books
·
· Score: 1
Environmentalists should be in favor of plastics replacing paper and pulp (and anything made of wood)
Here's why:
1) CO2, which comes mainly from fossil-fuel consumption is the leading anthropogenic greenhouse gas.
2) It is clear that every oil field will eventually be exploited, and every bit of that oil will either go into fuel or plastic. There aren't really that many other options. If it goes into fuel, it will eventually be converted into CO2 and contribute to global warming. But if it is used intstead to create some solid plastic object, it will eventually find its way into a landfill, where it will be safely stored for many many years, and where it can never be used as a fuel. And, since plastics are largely inert and non-toxic, this isn't any kind of real environmental problem. It may be an asthetic problem, but that's another issue.
So, in summary, more plastics means less CO2, and less greenhouse effect. Not to mention fewer chopped-down trees.
But have you ever seen an old giant sequoia? Some of the biggest ones have been measured at 15 feet in diameter 100 feet above ground level, and 25 feet in diameter near the ground.
I don't know much about logging, but I know you can't cut a tree like that down in 5 minutes. At least not without heavy equipment.
you can easily perform a hot-swap of the bios chip to flash it. I have done it at least 20 times for I-opener hackers around here. Boot with good bios , load the flash program. yank good bios chip. insert target chip CORRECTLY. flash it.
This only works with a socketed ROM BIOS chip. Not all ROM BIOS chips are in sockets. Some are soldered down, and some are or will soon be soldered BGA's which are practically impossible to replace without expensive and special tools.
People with such hardware should be very careful about flashing their BIOS.
Slashdot Mirror
And you are technically incorrect. ;-)
The speed of sound in an ideal gas doesn't depend on the pressure, but only on the molecular mass and on the temperature.
MM
--
Your comment reminds of the people harping about the ethics of attorneys.
Attorneys are not out for justice. They are out to advocate for their client's interests. That is the ethical code to which they are supposed to adhere, and they are only bad if they don't do that.
Soldiers are supposed to learn how to wage war, and, when appropriate, to actually wage war. Heinous war crimes aside, a soldier is only bad if he doesn't practice and actually wage war to the best of his ability.
The morality decisions (again, apart from clear crimes against humanity) are made at a higher level. In the US, it is congress and the president that decide when to use military force.
So, in general, eager troops are good, provided that they have good discipline up the chain of command.
Just my $0.02
MM
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Thanks for the info. A capsizing damage control trainer sounds pretty interesting, by the way!
MM
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Ah. Makes sense.
Thanks.
MM
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It is theoretically impossible for an air-powered gun to launch a projectile faster than the speed of sound.
I believe the root of it all is that the gas cannot move down the barrel faster than the RMS speed of a molecule of the gas. So, unless you use a hot gas, or a light one (helium?) you won't exceed the speed of sound.
I could be wrong about this.
MM
--
I used to work for Supershuttle, a van service that transports people to and from the airport. In my case, I was taking people to and from the San Francisco airport. One place we serviced was Treasure Island, then a Naval Base. I always asked the sailors what they did for the Navy. Almost every single one was a shipboard firefighter.
After a while, I came to the conclusion that there are probably a lot of shipboard fires during naval combat.
So, my point is, is it such a good idea to reduce the complement from 300 to 90?
But what do I know. I'm just a shuttle driver. Or I was just a shuttle driver, anyway.
MM
--
On the specific case of files, one thing he may be discounting, however, is that we ended up with disk files by choice. I'm not sure what the criteria were for making the decision, but other ways of arranging data on a magnetic disk (and tape) were used in the old days, and somehow, files and file systems ended up ruling the day. It may just be a waste of time to try the old ideas again. I mean, you wouldn't build a square wheel just because you think that we may have settled too quickly on round ones...
Anyway, this thread is dead, so I'm probably wasting my keystrokes.
MM
--
MM
--
There is a concept in marine architecture called hull speed. Basically, the speed of a non-planing boat is sort of fixed, irrespective of power, at some value which goes up as the square of waterline length. Near this hull speed, as you apply more power to increase in speed, you just make a bigger and bigger wake, but don't really move much faster.
In a planing hull, as you apply more power near hull speed, the boat sort of pops up off the surface of the water and begins to go much faster. It is no longer floating, but, more skimming on the surface. All fast boats that are small plane. It is just impossible to go fast without planing in a small boat.
For a submarine, there is no hull-speed issue. Subs can go faster and faster as they apply more power. I believe that nuclear submarine top-speed is classified, but I have heard lots of people say that they can do 60 knots. (1 knot ~= 1.15 mph). I doubt that even an aircraft carrier can do 60 knots. In fact, designing a boat to go 60 knots on the surface of the ocean (not a lake) is a very difficult task.
When you travel on the surface of the ocean, you have to deal with waves and wind, which become much more formidable as speed increases. A moderate sea is shaped like gentle sand-dunes, although the dunes are constantly shifting and morphing beneath you. A heavy sea (as in a storm) is more like a rock field or something in shape. The wave crests are much closer together, and the motion is much more violent. The waves can easily reach heights of 10, 20 or 30 feet, with crests perhaps 100 feet apart. If you haven't experienced it, it is hard to comprehend just how violent it is. I doubt very much any boat short of a few hundred feet can even go more than 30 or 40 miles an hour in this environment.
A submerged craft can travel serenely below all this. I imagine there is a bit of turbulence, but nothing like the chaos and danger of the surface.
Another perspective on all this is the difference between ducks and fish. Small tuna and jacks can easily hit 30 knots. I have seen them jump out of the water going this fast. Spinner dolphins can hit similar speeds. I have heard some people claim that big tuna can hit 40 or 50 knots. I don't know if this is true. Ducks can go about 2 knots.
The bottom line, I think, is that a low drag body can travel much faster submerged than a floating body of similar size, no matter what the shape. This is especially true when the surface of the sea is rough. Surface craft with very long waterlines MAY be just as efficient, I don't know.
MM
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The front bumper dives several inches due to suspension compression, and the rear bumper goes up. That is why the most typical accident, the freeway rear-ender, often results in hood damage to the car in back. In fact, it would probably be a good idea to mandate either higher bumpers in front, or lower bumpers in back.
MM
--
On the other hand, big SUV's that are really just trucks do have a slight safety problem because they have a non-deformable truck chassis and high center of gravity. When they crash into lighter vehicles, the lack of a deformable bumper/crumple zone is not so bad (for the SUV) but in other accident scenarios, the lighter, lower, deformable car is definitely better. For example, if you crash into a big tree at 35 MPH, you'd be much better off doing it in a Honda Civic than in a Chevy Suburban. And if you get side-swiped or hydroplane and lose control of your vehicle, you are less likely to flip in a low center of gravity car than in a big truck-type SUV.
MM
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MM
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MM
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Actually, you would think that a native widget app would be faster, but lots of people claim that SWT + gcj (or javac) is NOT faster.
I've never done a benchmark myself.
I do suggest that people who want to try SWT plus GCG go to my sourceforge project, libswt.
--
MM
This is a fundamental problem with cross-platform development using layout managers.
It isn't a criticism particular to SWT. Since the original post specifically asked about cross-platform GUI's, I think your criticism is out of place (off-topic) quite frankly.
MM
--
Well, the mass of the ship increases (I'm not making this up) as it gets closer to light speed, so it is harder and harder to maintain 1G.
;-)
If you don't believe me, go ask Einstein.
In any event, I'm not really sure how prounounced the time dilation effect actually is. Relativity is not my field.
MM
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I am going to call you on this. Where is a biased study? How was it flawed and how would you have done it differently?
Personally, I believe that if there are any hazards to humans from cell phone RF emissions, they are very slight, otherwise it would be easy to find them conclusively in a well-designed study.
And, if, perchance, you can't back up what you are saying, then please stop saying it.
MM
--
It turns out that what matters is the dielectric constant of the medium in which the electric wave travels.
In the case of wireless, that medium is air, which has a dielectric constant very nearly the same as free space (vacuum).
But electrical signals travelling in twisted pair wire (like category 5 cabling) travel a bit slower because the dielectric material they are travelling in is really the insulation in the wire. That's right, the signal is really travelling in the dielectric, not in the wires, per se.
So the speed of propagation doesn't depend on the properties of the wire conductor, but on the dielectric in between the two conductors.
You can calculate the speed if you know the relative permitivity of the dielectric. This is very closely related to the index of refraction, by the way.
Anyway, in most practical situations (i.e., in non-magnetic materials) the velocity equals the free-space speed of light divided by the square root of the relative permitivity of the dielectric. So in typical fiberglass circuit board, called FR4, where the '4' represents the relative permitivity, the speed of light is C/sqrt(4), or about half the free-space speed. Since the free-space speed is 300 Million meters per second, half of it is 150 million meters per second. You could also say that it is 150 meters per microsecond, or 0.150 meters per nanosecond, or 150 mm/ns.
But this is really only true for signals which are not on one of the surface layers. Surface layer signals experience a medium partially of FR4, and partially of air, so they travel a little faster.
--
MM
I don't think it is fair or makes much sense to lump all unices together with respect to kernel architecture. They are not all the same. I'm not really a kernel expert, but I know the different unices employed different techniques and came from substantially different code-bases.
Also, I would be interested in at least one and preferably a few example(s) of how the "aging paradigm" of UNIX is a major disadvantage to "OSS kernel hackers," as compared to Microsoft NT/2k hackers.
Also, it would be nice to see how this disadvantage or these disadvantages affected the Mac OS 10.2 hackers as well.
MM
--
Actually, the last time I checked, both aluminum and glass containers were VERY recycleable, in the sense that recycling them results in huge energy savings.
All other materials are highly questionable. When they "recycle" plastics, they mean, for example, that they shred them up and use them for filling outdoor furniture cushions or making synthetic building materials (for plastic fences and faux wood 2x4's and so on). They don't recycle plastic milk jugs into new milk jugs.
Steel (sometimes called tin) cans are not recycled in any meaningful way at all. I would suggest crushing them and keeping them in your own back yard, as some day they may be valuable to your progeny or your progeny's progeny.
MM
--
Environmentalists should be in favor of plastics replacing paper and pulp (and anything made of wood)
Here's why:
1) CO2, which comes mainly from fossil-fuel consumption is the leading anthropogenic greenhouse gas.
2) It is clear that every oil field will eventually be exploited, and every bit of that oil will either go into fuel or plastic. There aren't really that many other options. If it goes into fuel, it will eventually be converted into CO2 and contribute to global warming. But if it is used intstead to create some solid plastic object, it will eventually find its way into a landfill, where it will be safely stored for many many years, and where it can never be used as a fuel. And, since plastics are largely inert and non-toxic, this isn't any kind of real environmental problem. It may be an asthetic problem, but that's another issue.
So, in summary, more plastics means less CO2, and less greenhouse effect. Not to mention fewer chopped-down trees.
MM
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3-ft blade and five minutes, huh?
Maybe for new-growth.
But have you ever seen an old giant sequoia? Some of the biggest ones have been measured at 15 feet in diameter 100 feet above ground level, and 25 feet in diameter near the ground.
I don't know much about logging, but I know you can't cut a tree like that down in 5 minutes. At least not without heavy equipment.
MM
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I think that is EXACTLY what EVERYONE realizes.
MM
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I don't like Firefly very much. I tried to watch it because of the glowing praise it received here, but it was only mediocre, in my opinion.
Also, I don't think it has much geek appeal, personally. It is essentially a western, with characters of modern sensibilities injected into it.
Just my $0.02
MM
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This only works with a socketed ROM BIOS chip. Not all ROM BIOS chips are in sockets. Some are soldered down, and some are or will soon be soldered BGA's which are practically impossible to replace without expensive and special tools.
People with such hardware should be very careful about flashing their BIOS.
MM
--