John Cuthber

"The physics also tells us that red or infrared photons have less energy than blue photons, so I'm curious as to where the extra energy comes from?" I think you need to think about that again. Hint, if something were to absorb blue light, what colour would it be? "Define "exactly." Doppler and collisional broadening can be GHz — huge!" Typically "exactly" here means correct to about 4 sig fig. doppler and colisional broadeneing just alter the "exact" wavelength that gets absorbed by a particular atom. Question 1 A simplified model of the helium atom is that it consists of a nucleus with 2 units of charge and two electrons each with minus 1 unit of charge. The initial conditions are such that the system remains bound ie the system's energy is less than the ionisation energy a (for some marks) write down the Schrodinger equation for this model of the helium atom. b (for all the tea in China) solve that 3 body equation analytically and without aproximations.

"Pitbulls are the best dog for killing intruders" OK where is the evidence for this? "My choice to allow pitbulls will maintain a basic principle of liberty that dwarfs your cause like the size of the sun to a pebble." Reasserting this belief doesn't add to the debate and it doesn't make it true. "There is no freedom principle that allows your property to hurt others." That's a defense for permiting guns- it's not guns that kill, it's people. However dogs are capable of independent action. Jailing you after you dog kills someone doesn't save a life; banning the dog does. "I'm not. Some human life should be discarded. Like murderers, rapists, molesters, and etc. " If the 66 dead were all in one of those categories this would be relevant. They weren't ; it isn't. "But, to counter your point, those are 66 deaths that a human is responsible for. Just as I'm responsible for my car not running over your kids in the street, so am I responsible for my dog not eating them." Standing there yelling "bad dog" won't stop a detemined attack. You seem to have overlooked the fact that dogs are quite capable of autonomous behaviour. Srictly that statement you made would only be true if in each of the 66 cases the dogs had been ordered to attack. Otherwise you just have to accept that dogs sometimes "misbehave". When a poodle does that it's a p.i.t.a.; when a pitbul does it it could be a dead child. "When you're ready to quit putting a price on humans and get rid of automobiles, then we'll talk about how every life is worth saving. If you want to save "every life", then Pit Bull murders at 66 per 20 years is a really low-bar starting point don't you think" Did you not read the bit about the pointlessness of some risks, or did you just not understand it? (Incidentally I don't actually drive) If you don't hate dogs you should be particularly ashamed of this idea "But none of them kill people. I want a dog that is notorious for killing people so no one will break in my house. You don't have an alternative for that. " All you are doing is setting the poor dog up for a fall. Many "bad guys" carry guns and wouldn't hesitate to use them to kill or maim a dog. Now anyone who has been reading this thread will have realised that I'm not dog lover, but even I am offended when someone mistreats an animal by exploiting it's pack loyalty instinct like that. Shame on you. "Faulty logic anyway since you don't get to decide what particulars I should be attracted to. " If you were atracted to young boys, society would lock you up for it. Society does get to choose. "This is a dismissal of basic individual rights" No it's a dismissal of a single "right". Just like we dismiss the right to commit murder because the, actually rather more basic, right is to life. "- good intentions with bad consequences." The consequence is that some of the next 66 people will live. You might think that's a bad consequence.

Do you reaally not understand the difference? Asprin and frying pans have a usefull purpose; pitbulls don't. It's a good few pages back that I pointed out that we need to look at both sides of the "cost benefit" analysis here. From a practical point of view such as their conpanionship for people or their abillity as a guard dog, the pitbull can be replaced by, say, an alsation. Doing so reduces the risk to you and others. Why in the name of anything would you want a dog that's a pointless risk? Salicylic acid (without the acetyl group) will cure a headache but it's more dangerous than aspirin because it's more corrosive to the stomach. We use aspirin rather than salicylic acid because the latter is plainly an unneeded risk. Even if it were only a tiny bit more risk it would not be worth taking. Now, if you choose to take salicylic acid for your headache then, frankly that's your problem. It can't do me any harm. When you start taking risks with my life or health then I really have a right to question that choice. One way you might play dice with my life is to drive a car. You probably wouldn't harm me if you walked into me but if you drove into me you probably would harm me. On the other hand, I can see that a car might be useful to you. Since I can see that I to might want to drive a car I'm prepared to "trade". You drive and I take the risk that you might hit me because I want to drive and let you take the risk that I might hit you. What are you offering to me in trade for your choice to have a dangerous dog? The "guilt" of pitbulls is (whether you like it or not) well established- they are not a third of the dogs but they cause a third of the deaths. We are not talking about "innocent till proven guilty" here; 66 dead people is plainly guilty. This isn't some accademic point; if there were no pitbulls and their owners had chosen some other breed, then fewer people would have died. Your choice to allow pitbulls would kill other people; please give me a reason for it that their mothers will accept.

"An Article In The Washinton Post That Stated A Child's Skin Color Could Not Be Darker Than It's Parents." They should know better. Any chance of posting a link to the article so we can all have a good laugh at it please?

I gather that in the states you have the freedom to own guns but not nuclear weapons. The people, through their representatives in government have made that choice. In principle there is no difference between banning nukes and legislating to ban a breed of dog. (of course, there are practical differences) People have, in a democracy, the freedoms they choose to let their neighbours have The fact that many people chose to break the law is their fault, not mine. Now would you please answer the question, what's so much better about a pitbull compared to, for example, a retriever that explains why I should have to worry about my children getting attacked? If you want a dog, get a dog, but, unless you are deliberately antisocial, why would you want to get one that presents an unncessary risk to other people? "freedom" doesn't cut it; we already restrict individual freedom for the sake of the majority's freedom in many things. Why is this one different?

"No, no no, it's ALL physics!" A solution of copper sulphate in water looks blue. This is because there is an energy level that the electrons in the copper ion can be excited to by light in the red or infra red region. However that transition is between two states of d orbitals. The physics tells us that such a transition is forbidden and therfore the copper ion is colourless. The chemistry tells us its blue.* More seriously if that stuff is physics how come I'm a spectroscopist and I'm a chemist? And even more seriously, yes it's perfectly possible to see fluorescense from a gas but you need to get the laser at exactly the right wavelength. There are a number of ways, for example you can use the green light from a mercury lamp to excite iodine molecules in the vapour state (coincidentally these happen at the same wavelength). Or you can use a tuneable laser source (which would be expensive) or a broadband source. It might be interesting to try this with a blue LED and Br2 or NO2 but only if you know how to play with toxic gases safely. * I know it's down to vibrational effects really, but I learned it in chemistry, not physics.

The snopes article gives reasons why that sort of story is often faked, but it doesn't rule out the idea that it might have been true once. Any faith in doctor/ patient confidentiallity ignores the fact that doctors are human too.

What's a shperical wire?

I'm not sure about this "Because the watter as exotermic coumpound is more close to decomposition when heated. This results in lower voltage required. Of course, the higher conductivity and lower viscosity should be considered too, but the true reason is thermodynamical one." The cell is being driven at something like 9V from the adaptor but the thermodynamic equilibrium potential is something like 1V. So 8V are being wasted. The effect of temperature on the emf of the cell will be of the order of milivolts so you might get 7.8 volts wasted instead of 8 but the reall loss is the ohmic loses in the bulk of the solution.

Someone posted that you shouldn't pick your nose or rub your eyes after chopping peppers. They also said that blokes who need to pee at 3 am should sit down to keep the floor clean. There's a combination of those two concepts that constitutes good advice Also, if the chemical says " causes burns" try not to get it on your skin; if it says "causes severe burns" don't get it on your skin.

"No, the figure "alone" does not do that. What if every dog owner owned a pit bull, and only one guy owned a poodle? Those numbers would be misleading in that case wouldn't they?" What if all the numbers were made up? What if this thread is being written by pit bulls? Seriously, as has been pointed out, unless about a third of dogs in the US are pitbulls then pitbulls are statistcally more dangerous than other dogs. Stop pretending that, because we don't have data on evry dog in the US we can't make that observation. This brings us back to my earlier point; what's so great about these dogs that justifies keeping them even though they aer notably more dangerous than other breeds?

I once asked a mathematician and he said he thought they used these. http://en.wikipedia.org/wiki/Chebyshev_polynomials However I have practically no idea what they are or how they work.

The essence of the "scientific" argument seems to be this "Based on information about C14 dating that wasn't available 20 years ago, Jackson's theory suggests that only a two percent contamination could skew results by 1,500 years. " Which is odd, they knew about contamination 20 years back too. For this "new information" to make any sense all the separate parts of the shroud would have had to be "contaminated" to exactly the same degree. A much more sensible reason for all the 3 labs' results agreeing is that all of them were competent and so removed any contamination from the sub samples of cloth before they analysed it. Since the labs concerned were the best in the world that seems quite reasonable. There's also this bit "Basically, it is a re-analysis of the available data which takes into consideration the spatial positions of the sub-samples on the shroud. It shows that the 1988 statistical results are not correct," which makes sense if the different peieces of the shroud are of significantly different ages or compositions. This overlooks the fact that it's basicly 1 bit of cloth.

Dragging ions through the solution using an electric field is more difficult if the liquid is viscous. Heating water will reduce the viscosity and so less work will be done on those ions. If you need to waste less effort working against viscosity then you will get better efficiency . (Actually there are other complications, particularly in the case of protons in solution. It's called the proton switch mechanism.)

Lower viscosity will help too.

The uncertainty principle just about rules out measuring you acccurately enough to copy you anyway. Transfering that data and producing the copy somewhere else would be less of a problem than measuring it.

"We do not want the medals to be diluted and watered down. " Synchronised swimming? Rythmic gymnastics? Olympic standard hypocrisy I think.

If the prof had thought to point out that the difference between a poodle and a rottweiler (sp?) is evolutionn and that (at least according to one deffinition) the eye is part of the brain, would the student now be president? Darkness really exists- we have all seen it. You can measure it; ironicly you use a light meter. "You argue there is life and then there is death, a good God and a bad God" Actually he was arguing that there is no God. Destroying a strawman isn't a valid debating technique. Evil isn't the absesnse of good, it's the opposite. The absense of good is indifference.

I would rather take my chances with, for example, the licensed fungicides left in food than the fungal mycotoxins that mouldy food would contain. Also, the "organic" movement permits the use of really rather toxic compounds like nicotine and rotenone. Nicotine proportionately more toxic to people than to the insects they are meant to kill. I think you could argue that's "silly". Since the tomato taste testing wasn't done "double blind" it's hard to see that it has any great value.

Then the question's not got a lot to do with the night sky.

Actually, I think a single electron in an infinitely large empty box can be at rest. More importantly, even for a finite box ( and, therefore finite quantisation of translational energy) I think the ground state is the one with zero kinetic energy. The uncertainty principle isn't bothered because you don't know where in the box to find the particle.

There are two different things in that equation symbolised by "v" and "V" which probably isn't helping anyone.

From Norman "In my New York, the words of the prophets are written on the subway walls, and tenement halls... (Paul Simon)" I think using Paul Simon lyrics as an excuse for petty vandalism is a new debating trick. *(BTW, do you know if the guy concerned is any happier about his country's government than you are?) However it doesn't answer the question. Why do you think the Chinese government (as opposed to some of the people) will give a damn if, for example, the USA or UK boycot the olympic games? * Actually, I think it's just a straight non sequitur, but where's the fun in that?

No, it's zero point energy. If they were stationary you would know their momentum and position exactly. That's a breach of the uncertainty principle. They are moving but, since you can't stop them, they don't have energy that you can take from them. If you cn't take that energy away then you can't "cool" them so they must be at absolute zero. (Strictly that only applies vibrational movement of atoms in a crystal lattice or a molecule, atoms of a gas could be stationary because you wouldn't know where they were so the uncertainty remains. OTOH, at absolute zero pretty much everythuing freezes) WTF this has to do with time I don't know.

The temperature of the sun's surface is about 6000 C. We don't need to go there to measure it; we just need to study the spectrum of light it emits. We could do the same experiment from pluto (though it would be a bit tricky) and we would still get the same answer. The temperature of the sun is the same wherever you measure it from (I don't want to know abouth the super hot corona etc. here). The same is true for "space"; it has a temperature- we can measure it (it will change with the deffinition you use for temperature) In much the same way we could measure the temperature of the sky by averaging the spectrum- it would give a pretty odd set of answers depending on what wavelengths you chose to look at but you could average over all those to get some sort of an answer. An easier way would be to find something that never sees the sun (tricky) or seldom does- the dark bits of the moon might be close enough, and measure its temperature.