John Cuthber

"We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard".

The brain can say if some statements are true but there are some about which we are not sure (not least, the quesstion that forms the title of this thread). I could write a program that, if asked "Is the sum of 2 even numbers an even number?" would reply "Yes". It may well be the the fact that we con often answer general questions like this means that we are not turing machines- but it could be that we are somehow programed to recognise some questions and give the right answer.

"btw this plastic is also known as PET" Yes.

Get 2 plates of glass, put thin spacers between them. Seal round most of the edges to give a big flat very thin glass box. Dissolve the sunscreen up in something- alcohol will probably work, and pour it into the gap between the plates. Seal the last bit of the edge and you have a filter with a known amount of sunscreen distributed evenly over a known area. Just getting hold of the active ingredient in the sunblock might make it easier to get a clear solution. Incidentally, as has been pointed out before, glass blocks a lot of UV. Big sheets of fused quartz are going to cost a fortune. You might want to look up the UV spectra of, for example, perspex, and PVC. Perspex won't survive alcohol indefinitley, but it might give you time to grow some plants. I'd not like to be there when someone trys to spin coat a big glass plate.

Once he has done it outside a hundred times then you might think about saying it's safe enough to do inside.

I was just testing to see if anyone read the list. The RMX should be HMX.

Isn't the answer to this question "Yes, I have one between my ears"? I think we need a definition of computer as well as consious. If my brain (and as much of the nervous/ sensory system as is required) can be mapped onto a turing machine then a computer can be consious (at least as much as I can). If not then it can't (at least for the definition of consious that says it means "acting like a brain"). Is the brain a turing machine? If not, what does it do that a turing machine can't? (and I know that one possible answer to that is that a brain can be consious- but that's begging the question).

You can recrystalise it from salt substitue and that will get you a pure enough product for most things. What do you want it for?

Ironiser, Trust me, it does make sense, and you can just think about it. The problem is that you need a lot of background knowledge before you can do that- not least you need to understand a lot of quantum mechanics. In the meantime, have fun trying to live your life without having to remember stuff.

Aparently about 320% of people have voted in this poll, so I guess there must be a God after all (or the software has screwed up somehow)

He can pay as much attention as he likes in class. That equation is just plain wrong. The product of the reaction is acetic acid, so googling it might not help. There's another way of balancing equations that might help here. Pretend that the Cr(VI) is present as CrO3 (not a million miles out for acid dichromate) and that it's converted to Cr2O3. 4 CrO3 --> 2 Cr2O3 + 3O2 Then write out the oxidation as if its being burned in oxygen C2H5OH + (however many) O2 --> CO2 + H2O Each O2 requires 4/3 CrO3 From that you can get the stoiciometry of the reaction.

Well, you might be a student, but I think you are right. NOC is not a stable compound and it's not a radical I have ever heard of.

"None of the above" would be a good option.

It's difficult to put them in any real order but I wasn't exactly happy working with flurosulphonic acid perchloric acid, HF, bromine, nitroglycerine, PETN, TNT, RDX, picric acid, EGDN, tetryl, RMX, RDX, tetrachlorodibenzodioxin or ricin. On the other hand I think more people are killed by alcohol than by all those "nasty" chemicals put together.

He's going down hill. Even with the engine switched off he would still roll down the hill and accelerate until the wind resistance (etc) was dissipating energy as fast as gravity was providing it. The engine isn't the only power source here.

Sucralose is a calorie free sweetner so its not going to provide energy. Taurine and speed have practically nothing in common. The most likely effect of all these added chemicals is to give you really expensive urine, that's where the end up.

Usually, but not always. At the maximum the change in absorbtivity with wavelength is small so errors in the wavelength don't matter so much. On the other hand, if there's a "valley" in the spectrum you can use that instead. Of course, the sensitivity will be lower, but that might be an advantage sometimes. If the solution is very concentrated you might want to use some wavelength where the stuff absorbs less strongly- that way you don't need to dilute the sample to get it within the linear range of the spectrometer. Also if the solution has some impurity in it that also absorbs at the maximum, but not somewhere else in the spectrum you can sometimes measure the concentration without interference from the impurity.

This has been discussed at some length on another site. http://www.thenakedscientists.com/forum/index.php?topic=17926.0 The problem is not with the physics, but with the poster's interpretation.

Heating copper to red heat in air will coat it with the oxide (mainly CuO, some Cu2O). Quenching it in water will make a lot of the oxide fall off as flakes. With a bit of copper pipe, a gas stove and a bucket of cold water you should be able to make some quite easily. If you want a lot this will get tedious. Adding copper compounds to H2O2 generally makes it decompose to water and O2 - not a lot of use. What do you want the stuff for? If it's for colouring flames then the quality of the product from heating copper in air is probably good enough.

DMSO doesn't smell much but one of its uses is as an oxidant. The by product (the sulphide) really stinks. I think a scrubber with an amine might be a better idea- such scrubbers are used for cleaning up gas streams anyway so the technology isn't new. How fast MeI reacts with, for example, ethanolamine, is another matter.

The heat of neutralisation in water is the the same for all acids so you could do this reaction in solution. Sb(V) is fairly oxidising so I suspect the product would be Fe(III) hexafluoroantimonate, even if you started with Fe(OH)2. If someone said "What happens if I add dilute perchloric acid to Fe(OH)3 ?" would anyone be predicting anything exciting?

In what way?

I know that people have extracted DNA from old things but that Dinosaur DNA from amber remains in the realms of science fiction. What's the oldedts DNA found and is it reasonable to assume that viruses might last roughly that long?

Not to me. For every positive number there is a negative number and they form a pair whose sum is zero. Then you sum all the zeros and get zero.

I also think that's what the question is about. You might also want to add something about the pros and cons of the various definitions. Incidentally, I never found "electronegativity" to be a very useful concept. As far as I can see, the definition is pretty much circular. It seems to be something like "Fluorine and oxygen behave in such and such a way because they are electronegative; electronegative elements are the ones that behave in such and such a way." Actually, they behave that way because of the way their electrons are organised and the extent to which they shield the nucleus. If their electrons didn't behave that way, they would be a different element.