I never have problems with my mom. After all, she spends her days using OS/390 and writing reports in EasyTrieve and Cobol. The only complaint I ever hear from her is the occassional "Fuck!!!" directed at the laptop...
Not to mention column and table constraints, stored procedures, extensible datatypes, user-defined operators, query rewrite rules, and schema and domain support.
How about views? All I want is friggin' VIEWS. Why is that still missing?
Funny how the economy goes in the toilet, and all of a sudden state governments start realizing that Microsoft is really a band of highway robbers. And this isn't the only announcement in recent weeks that a state is seriously considering switching things over to Open Source software.
I wonder if Open Source could contribute to an economic comeback in any way.
Exactly. I said the same thing to my over-eager friend, who insisted we try to overclock my Athlons to insane speeds by submerging the motherboard in a tub of antifreeze. We tested this first on an old 486 motherboard. Just for future reference, submerging a computer in antifreeze doesn't work. (However, we did learn that you can rinse the motherboard very carefully with water, let it dry, and it will work again -- picture two idiots spraying down a motherboard in the kitchen sink, then blowdrying for about 20 minutes -- this mobo has sentimental value.) Apparently antifreeze has very poor characteristics at high frequencies. Just because it's nonconductive doesn't mean it'll work.
Anyway that was a little OT, but my point is, why spend $massive dollars overclocking/tricking out the case when you could just buy better equipment for half the difference?
With all the air going though there, the housing won't look pretty for long.
Put one of those negative ion generators inside. It'll zap all that dust, and just imagine how all those negatively charged particules will enhace your computer's functionality!
It doesn't mention it in the article, but the streaks almost always flow away from the poles (i.e., they flow south in the north hemisphere, north in the southern hemisphere). This seems to imply that temperature gradients have something to do with enabling the flow. It helps narrow down the range of possible substances. This is why astrogeologists like the idea that it could be water.
These dark streaks have been known for actually quite some years. It has been constant debate over what they are. This scientist isn't the first to propose it's liquid water. She doesn't seem to put forth any fantastic new ideas, though. Basically, she did a lot of observation, more than most other scientists have bothered to do, and has actually witnessed new streaks forming.
Friction is indeed nonconservative, but this describes energy becoming disordered. You can effectively lose mechanical energy in this way, but you cannot lose (total) momentum.
For some reason people are interpretting my post as claiming that the total angular momentum changes. Of course it can't. All I was trying to point out is that the transfer of momentum from the Earth to the atmosphere is not easily reversed. A change in Earth's angular momentum will show up as an equal and opposite change in the atmosphere, but the individual molecules in the atmosphere are still moving randomly. The angular momentum has been "diffused" throughout the atmosphere and can't be transferred back to the Earth.
I didn't claim the momentum was *lost*.
The same thing happens when you, e.g., stop a bicycle tire from spinning by gripping the brake pad. This produces heat. The total angular momentum is still there, but in a form that can't be converted back into rotation of the bicycle tire.
Momentum is not energy. Angular momentum is always conserved. Just think about it logically - to slow the rotation of an object down it has to push against another object in the opposite direction of rotation - which increases the rotation of that object. The sum total of angular momentum (similar to linear momentum) will always remain the same. This is very basic physics people.
Re-read my post. I never stated that angular momentum is not conserved. I said that the process is *irreversible*. Go back to the bathtub example. The swirling water eventually transfers its angular momentum to the Earth (and that momentum is conserved). Now, imagine the process happening in reverse, with the Earth spontaneously transferring angular momentum to the tub of water, decreasing Earth's momentum and increasing that of the water.
You never see this process, because *thermodynamics* prevents it from happening.
Even allowing this point, static air molecules hit the revolving ground, bounce of at a tangent, absorbing rotational momentum... *But* unless the molecules are launched at escape velocity, they will eventually fall back down, hit the earth and transfer the energy right back. The whole process is very reversible.
If you add the angular momenta of the individual molecules in the atmosphere, yes you would find that the total change in momentum is exactly opposite to that of the Earth. But any *individual* molecule is going to be moving essentially randomly. The non-zero change in momentum is only visible on the scale of the entire atmosphere. On smaller scales all you "see" is heat.
The fact that the net change in atmospheric momentum is non-zero doesn't change the laws of thermodynamics -- the individual particle momenta are still randomly oriented even though their speed distribution is (ever so slightly) asymmetrical. In order for the angular momentum to transfer back to the Earth, the particles would all have to strike the surface while travelling in the same direction. Since there are so many microstates available to the atmosphere, the chances of this are vanishingly small (i.e., entropy cannot decrease over long time periods).
Oh, and "Heat radiation carries angular momentum"?! Does the photons have extra spin or what the hell are you getting at??
Yes, photons carry angular momentum. As spin-1 particles they carry either -h/2 or h/2 J*s. If they did not, then angular momentum would not be conserved when atoms collapse into low energy states (since the lower electronic state has less angular momentum, the different in momentum must be carried away by the photon).
This is so stupid, I don't even want to try to explain. Look up angular momentum in any high school physics book.
Sigh... I suppose the introductory book also told you that light was a wave, and electrons are particles, and that gravity obeys an inverse-square law. None of which is strictly true.
If something has angular momentum, then it must be in motion with respect to some fixed point of reference. If it is in motion, then it possesses kinetic energy. The individual molecules in the atmosphere continually collide and redistribute this kinetic energy, while keeping the total angular momentum constant. The random molecular motions constitute "heat" by its very definition.
I *never* claimed that angular momentum is lost. It simply gets diffused throughout the entire atmosphere, irreversibly. In other words, it "appears as heat."
The main cause of the earth's rotation slowing _during EL Nino years_ is the change in the angular momentum of the earth. This means, that as some point, the angular momentum will change BACK!! Hence, CONSERVATION of momentum.
NO! I'm not sure why people are having a hard time with this.
As the wind brushes against the surface, it transfers momentum from the Earth and stores it as heat. This heat can't be transferred back! The total angular momentum remains constant, but the process is not REVERSIBLE.
Imagine the following: the Earth is a plastic ball, and the atmosphere is a metal sheath which encases the ball. Suppose the metal sheath doesn't touch the ball, but is separated from it by a millimeter.
Now, spin the ball, and cause the metal sheath to contract so that it grips the ball. Quite like the clutch of a car engaging. Immediately, angular momentum is transferred from the ball to the sheath, until the ball and sheath are now rotating at the same rate.
The thing is, during this whole process, the sheath *heated up*. Anyone who has burned the clutch on their car knows this. This heat cannot magically transfer back to rotational energy. Angular momentum is conserved, but it is "hidden" in the form of heat.
In fact, since hot objects radiate, and radiation carries angular momentum, the angular momentum which is stored as heat eventually radiates away from the ball-sheath system, and is lost forever.
I didn't say it was. I said *total* energy is conserved. This includes heat.
if you heat up the Earth, the athmosphere will expand, the earth's rotation will slow down, and the total rotational energy will increase -- but the angular momentum remains constant.
The effect they're talking about isn't due to increased rotational inertia from an expanding atmosphere. They are talking about fast winds exerting friction on the surface. You're correct in that the angular momentum transferred from the Earth ultimately ends up in the atmosphere, but the point I was making is that this transfer is not reversible. The angular momentum appears in the atmosphere as heat, and all the well-known efficiency theorems from thermodynamics apply to it.
Sorry, I'm going through this article trying to correct as much bad physics as I can, even though I know you meant this as a joke. So here's my pedantic comment:
Everybody run east as fast as you can, to speed the Earth up again!
Disregarding the honest mistake (you need to run West, not East)... This would actually work, as long as everyone *keeps running*. As soon as they stop running, the angular momentum which was transferred to the Earth will be transferred back to the runners. You can't change the total angular momentum of the system.
In order to speed up the Earth you would have to use a rocket or some kind of cannon which is capable of flinging material *clear off* Earth's surface, never to return. Even then, the amount of energy contained in the rotation of the Earth is *astonishingly huge*. It's doubtful we'll ever come up with anything that could make even the slightest impact on it.
When snow collects on mountains, it increases the earth's radius ever so slightly... so the actual day span increases by a fraction of a second.
True, but when the snow melts in spring the rotation will speed back up again (rotational inertia decreasing as mass moves downward).
This is fundamentally different from wind friction, which is a non-conservative force which *irreversibly* slows the Earth's rotation. The only way it might speed up again is if the wind started blowing the opposite direction with equal force.
This happens more during the winter when the earth is farther away from the sun.
The Earth is *nearer* the sun in the Northern Winter. It is the tilt of the rotational axis which produces winter, not distance from the sun. The moment of closest approach (perihelion) actually precesses very slowly (arcseconds per year). In short, there is utterly no relationship between distance to the sun and the seasons we experience on Earth.
Do we manually synchronize our clocks every once and awhile (say every few years anyways) just to make sure?
It depends what kind of clock. The cesium clock is the scientific *definition* of a second, therefore it doesn't need to be calibrated since everything else is calibrated to *it*. How often you need to synchronize your clock depends on how accurate it is (usually measured in parts per million, or parts per trillion for accurate clocks).
It seems to me that whatever changes strong winds make in the earth's rotation must be temporary because of the conservation of angular momentum. When the wind pick up, the earth slows down. Wehn the winds die down, the earth speeds up again.
No. Friction is a non-conservative force. The energy is irreversibly transformed into heat. *Total energy* is conserved, but there is no physical law saying that kinetic energy must remain kinetic, or rotational must remain rotational.
Imagine a bathtub full of water, with the water sloshing around in the bathtub. As the sloshing water rubs against the sides of the tub, it transfers energy to the tub in the form of heat. Eventually the sloshing ceases, and all the kinetic energy the water had is now converted to heat. The process is irreversible -- you don't suddenly see the bathtub *cooling down* as the water spontaneously starts sloshing again.
Do you then go ask for a credit from the utility because of the excessive/unexpected use?
For unexpected use, of course you can't demand a freebie, since it is understood that the fountain is for public use. However, suppose someone presses the button on the fountain and holds it for several hours without drinking anything. This seems like theft, to me.
Any service offered to the public has certain bounds within which it is expected to be used. People should have the authority to prevent others from abusing their services.
If someone is DOSing me, and I have no authority or technical capacity to stop their attack, then why should I pay for someone else's criminal behavior? If I immediately pull the plug on my network, call up the ISP to inform them, yet the packets still come cascading in... I have acted in good faith to do everything possible.
The current situation is like being able to watch the guy pressing the button on the fountain, and paying for the water, yet not being able to do anything to stop it. How can that be *my* fault?
Well, here's the scenario people seem to be putting forth:
ISP A has customer X. ISP B has malicious user Y. Malicious user Y sends huge quantities of packets to user X.
The question seems to be, should ISP A eat the cost, or should customer X eat it? Why the hell are those the only two options?! It seems to me like ISP *B* should eat the cost, since the malicious packets were sent through their network in the first place. ISP B can attempt to recover their loss directly from malicious user Y.
The ISP *and* the customer are both victims in a DOS attack. Whoever runs the network which *initiated* the attack should be responsible.
And, of course, all these calculations go out the window if someone (other than sci-fi writers) comes up with propellantless propulsion. But I'm not holding my breath for that one.
It already exists. It's called light pressure. Just divide watts by the speed of light to get force. E.g., if you shoot a 150MW laser out the back, the craft will experience 150e6/3e8 = 0.5 newtons of thrust.
It should be obvious at this point that although propellant-less "propulsion" is a physical possibility, it is nowhere near practical...
But, I personally view each such step with a little trepidation. Once the first quantom computer is made... all our present encryption will be... useless against it.
To modify an old phrase: What quantum physics giveth, and it taketh away.
Quantum encryption makes it impossible for wiretappers to snoop on transmissions. As long as the communication endpoints are secure (this includes physical security), transmissions over quantum channels are completely secure, quantum computers NOTwithstanding.
The problem with completely secure crypto isn't technical, it's economic and political. You need special equipment (and a direct fiber link) to do quantum crypto. Unless you can afford (and are legally allowed) to buy this equipment, your communications will be vulnerable to governments and powerful corporations who have quantum code cracking computers.
The Riemann hypothesis isn't exactly the most practical of problems, but many people have spent decades working on it (and some have gone insane). It's good that it is finally put to rest.
info? Never managed to get the knack. I can just about to drill down - but get back up?
By hitting the 'u' key. You know, as in Up.
BTW, when using Info remember that you're actually using a hacked version of Emacs. By learning to use Info you are learning some parts of Emacs. If you have some kind of religious conflict with this, you should probably stop using Info.
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96 KHz is often more than enough to deal with simple analog circuits. And 24 bits of precision is insane. Screw the Audigy, I just want the ADC chip!
I'm proud of my Big Iron Momma.
How about views? All I want is friggin' VIEWS. Why is that still missing?
I wonder if Open Source could contribute to an economic comeback in any way.
Anyway that was a little OT, but my point is, why spend $massive dollars overclocking/tricking out the case when you could just buy better equipment for half the difference?
Put one of those negative ion generators inside. It'll zap all that dust, and just imagine how all those negatively charged particules will enhace your computer's functionality!
Just remember, 10 years from now your cool modded case with its dual Athlon 2600s is going to look like a funny piece of crap.
These dark streaks have been known for actually quite some years. It has been constant debate over what they are. This scientist isn't the first to propose it's liquid water. She doesn't seem to put forth any fantastic new ideas, though. Basically, she did a lot of observation, more than most other scientists have bothered to do, and has actually witnessed new streaks forming.
But it definitely isn't conclusive at all.
For some reason people are interpretting my post as claiming that the total angular momentum changes. Of course it can't. All I was trying to point out is that the transfer of momentum from the Earth to the atmosphere is not easily reversed. A change in Earth's angular momentum will show up as an equal and opposite change in the atmosphere, but the individual molecules in the atmosphere are still moving randomly. The angular momentum has been "diffused" throughout the atmosphere and can't be transferred back to the Earth.
I didn't claim the momentum was *lost*.
The same thing happens when you, e.g., stop a bicycle tire from spinning by gripping the brake pad. This produces heat. The total angular momentum is still there, but in a form that can't be converted back into rotation of the bicycle tire.
Re-read my post. I never stated that angular momentum is not conserved. I said that the process is *irreversible*. Go back to the bathtub example. The swirling water eventually transfers its angular momentum to the Earth (and that momentum is conserved). Now, imagine the process happening in reverse, with the Earth spontaneously transferring angular momentum to the tub of water, decreasing Earth's momentum and increasing that of the water.
You never see this process, because *thermodynamics* prevents it from happening.
If you add the angular momenta of the individual molecules in the atmosphere, yes you would find that the total change in momentum is exactly opposite to that of the Earth. But any *individual* molecule is going to be moving essentially randomly. The non-zero change in momentum is only visible on the scale of the entire atmosphere. On smaller scales all you "see" is heat.
The fact that the net change in atmospheric momentum is non-zero doesn't change the laws of thermodynamics -- the individual particle momenta are still randomly oriented even though their speed distribution is (ever so slightly) asymmetrical. In order for the angular momentum to transfer back to the Earth, the particles would all have to strike the surface while travelling in the same direction. Since there are so many microstates available to the atmosphere, the chances of this are vanishingly small (i.e., entropy cannot decrease over long time periods).
Oh, and "Heat radiation carries angular momentum"?! Does the photons have extra spin or what the hell are you getting at??
Yes, photons carry angular momentum. As spin-1 particles they carry either -h/2 or h/2 J*s. If they did not, then angular momentum would not be conserved when atoms collapse into low energy states (since the lower electronic state has less angular momentum, the different in momentum must be carried away by the photon).
Sigh... I suppose the introductory book also told you that light was a wave, and electrons are particles, and that gravity obeys an inverse-square law. None of which is strictly true.
If something has angular momentum, then it must be in motion with respect to some fixed point of reference. If it is in motion, then it possesses kinetic energy. The individual molecules in the atmosphere continually collide and redistribute this kinetic energy, while keeping the total angular momentum constant. The random molecular motions constitute "heat" by its very definition.
I *never* claimed that angular momentum is lost. It simply gets diffused throughout the entire atmosphere, irreversibly. In other words, it "appears as heat."
NO! I'm not sure why people are having a hard time with this.
As the wind brushes against the surface, it transfers momentum from the Earth and stores it as heat. This heat can't be transferred back! The total angular momentum remains constant, but the process is not REVERSIBLE.
Imagine the following: the Earth is a plastic ball, and the atmosphere is a metal sheath which encases the ball. Suppose the metal sheath doesn't touch the ball, but is separated from it by a millimeter.
Now, spin the ball, and cause the metal sheath to contract so that it grips the ball. Quite like the clutch of a car engaging. Immediately, angular momentum is transferred from the ball to the sheath, until the ball and sheath are now rotating at the same rate.
The thing is, during this whole process, the sheath *heated up*. Anyone who has burned the clutch on their car knows this. This heat cannot magically transfer back to rotational energy. Angular momentum is conserved, but it is "hidden" in the form of heat.
In fact, since hot objects radiate, and radiation carries angular momentum, the angular momentum which is stored as heat eventually radiates away from the ball-sheath system, and is lost forever.
I didn't say it was. I said *total* energy is conserved. This includes heat.
if you heat up the Earth, the athmosphere will expand, the earth's rotation will slow down, and the total rotational energy will increase -- but the angular momentum remains constant.
The effect they're talking about isn't due to increased rotational inertia from an expanding atmosphere. They are talking about fast winds exerting friction on the surface. You're correct in that the angular momentum transferred from the Earth ultimately ends up in the atmosphere, but the point I was making is that this transfer is not reversible. The angular momentum appears in the atmosphere as heat, and all the well-known efficiency theorems from thermodynamics apply to it.
Everybody run east as fast as you can, to speed the Earth up again!
Disregarding the honest mistake (you need to run West, not East)... This would actually work, as long as everyone *keeps running*. As soon as they stop running, the angular momentum which was transferred to the Earth will be transferred back to the runners. You can't change the total angular momentum of the system.
In order to speed up the Earth you would have to use a rocket or some kind of cannon which is capable of flinging material *clear off* Earth's surface, never to return. Even then, the amount of energy contained in the rotation of the Earth is *astonishingly huge*. It's doubtful we'll ever come up with anything that could make even the slightest impact on it.
True, but when the snow melts in spring the rotation will speed back up again (rotational inertia decreasing as mass moves downward).
This is fundamentally different from wind friction, which is a non-conservative force which *irreversibly* slows the Earth's rotation. The only way it might speed up again is if the wind started blowing the opposite direction with equal force.
This happens more during the winter when the earth is farther away from the sun.
The Earth is *nearer* the sun in the Northern Winter. It is the tilt of the rotational axis which produces winter, not distance from the sun. The moment of closest approach (perihelion) actually precesses very slowly (arcseconds per year). In short, there is utterly no relationship between distance to the sun and the seasons we experience on Earth.
Do we manually synchronize our clocks every once and awhile (say every few years anyways) just to make sure?
It depends what kind of clock. The cesium clock is the scientific *definition* of a second, therefore it doesn't need to be calibrated since everything else is calibrated to *it*. How often you need to synchronize your clock depends on how accurate it is (usually measured in parts per million, or parts per trillion for accurate clocks).
No. Friction is a non-conservative force. The energy is irreversibly transformed into heat. *Total energy* is conserved, but there is no physical law saying that kinetic energy must remain kinetic, or rotational must remain rotational.
Imagine a bathtub full of water, with the water sloshing around in the bathtub. As the sloshing water rubs against the sides of the tub, it transfers energy to the tub in the form of heat. Eventually the sloshing ceases, and all the kinetic energy the water had is now converted to heat. The process is irreversible -- you don't suddenly see the bathtub *cooling down* as the water spontaneously starts sloshing again.
I mean, this is basic thermodynamics.
For unexpected use, of course you can't demand a freebie, since it is understood that the fountain is for public use. However, suppose someone presses the button on the fountain and holds it for several hours without drinking anything. This seems like theft, to me.
Any service offered to the public has certain bounds within which it is expected to be used. People should have the authority to prevent others from abusing their services.
If someone is DOSing me, and I have no authority or technical capacity to stop their attack, then why should I pay for someone else's criminal behavior? If I immediately pull the plug on my network, call up the ISP to inform them, yet the packets still come cascading in... I have acted in good faith to do everything possible.
The current situation is like being able to watch the guy pressing the button on the fountain, and paying for the water, yet not being able to do anything to stop it. How can that be *my* fault?
ISP A has customer X. ISP B has malicious user Y. Malicious user Y sends huge quantities of packets to user X.
The question seems to be, should ISP A eat the cost, or should customer X eat it? Why the hell are those the only two options?! It seems to me like ISP *B* should eat the cost, since the malicious packets were sent through their network in the first place. ISP B can attempt to recover their loss directly from malicious user Y.
The ISP *and* the customer are both victims in a DOS attack. Whoever runs the network which *initiated* the attack should be responsible.
It already exists. It's called light pressure. Just divide watts by the speed of light to get force. E.g., if you shoot a 150MW laser out the back, the craft will experience 150e6/3e8 = 0.5 newtons of thrust.
It should be obvious at this point that although propellant-less "propulsion" is a physical possibility, it is nowhere near practical...
Maybe you can't enforce Arkansas law in Texas, but the Texans can sure enforce their law in Arkansas. All it takes is a shotgun and a pickup truck.
I didn't mean rest in peace, I said "rest easy." Not the same thing...
To modify an old phrase: What quantum physics giveth, and it taketh away.
Quantum encryption makes it impossible for wiretappers to snoop on transmissions. As long as the communication endpoints are secure (this includes physical security), transmissions over quantum channels are completely secure, quantum computers NOTwithstanding.
The problem with completely secure crypto isn't technical, it's economic and political. You need special equipment (and a direct fiber link) to do quantum crypto. Unless you can afford (and are legally allowed) to buy this equipment, your communications will be vulnerable to governments and powerful corporations who have quantum code cracking computers.
The Riemann hypothesis isn't exactly the most practical of problems, but many people have spent decades working on it (and some have gone insane). It's good that it is finally put to rest.
By hitting the 'u' key. You know, as in Up.
BTW, when using Info remember that you're actually using a hacked version of Emacs. By learning to use Info you are learning some parts of Emacs. If you have some kind of religious conflict with this, you should probably stop using Info.