John Cuthber

It's not even the BBC's news site.

Water is transparent to UV light sown to at least 190nM so that calculation is wrong.

Yew, Foxglove and the Madagascar periwinkle?

The problem with thrying to make money growing these is that someone will ahve beaten you to it.

wtf is NaONH3?

Just a thought or two.

"Catching water in a bucket moving at relativistic speeds would result in water vapor and a bucket with a hole in the bottom."

All speeds are relativistic- some more so than others.

Imagine 2 taps and 2 buckets.

One bucket is just below the tap, the other is a zillion miles further down.

I turn on both taps and, in the time it takes to fill one of them, the water has yet to fall a zillion miles and reach the other.

The higher bucket fills first.

On average a bucket moving up and down is higher than one that's at the bottom of the stream. It should fill (marginally) faster.

This ones easy "If ambient temperature is at the initial freezing point of the liquid, how long will it take to completely freeze the contents of the container?"

It won't. as soon as some ice forms the salt concentrationin the rest of the water will rise. This will lower the FP. That means that the external temperature is no longer below the FP and no more ice will form.

Saying "salt" without specifying which is generally taken to mean NaCl. Also 35g/l is about the salt concentration in sea water and I doubt that's a coincidence.

A bit of googling shows that the freeziong point of sea water is about -2C

If the abmient temp is just 5C below this (ie about -7C) then the stuff will never freeze solid.

As before as the ice forms the salt will be concentrated in the remaining water. It will reduce the freezing point.

To get it to freeze solid you would need to cool it to at least -21C (the eutectic point of ice and salt).

How long it would take to freeze is a much more complicated problem and there's not enough information given to answer it.

Given what salt does to plants I'd give HCl a miss.

IIRC Ammonium sulphate will reduce the pH and supply nitrogen but ,as with all things, you don't want to overdo it.

I sugest that you take a known amount, say a litre, of water from your system. Add the acid to that and measure how much it takes to get to the right pH then you can work out how much it will need to sort out the pH of the whole lot. (if it's 5 gallons then it takes 21 times as much acid to get the pH of the bulk of the solution to a given pH as it takes to get 1 litre to the right pH). Add most of that much acid and mix it in and see how close to the right pH you are.

It's possible to get to the right pH by overshooting with the acid then adding a base but you don't want to add any more stuff than you need.

I don't know because I wasn't there at the time but I think it might have been started with a combination of heat and pressure.

A meteor falling to earth gets hot as it travels through the air. The energy to heat it comes from its kinetic energy and that, in turn, comes from gravitational potential energy.

Imagine a big lump of rock in space. Things would be atracted to it by gravity- they would crash into it and warm it up slightly. Imagine that process carrying on until you had a star's worth of material.

I think it would be pretty hot before any nuclear reaction started.

Anyone know how much fluid is in an empty stomach?

The clue is in the question. It's empty so ...

There's the punch line of the old joke...

"Three freshman-engineering students were sitting around talking between classes, when one brought up the question of who designed the human body.

One of the students insisted that the human body must have been designed by an electrical engineer because of the perfection of the nerves and synapses.

Another disagreed, and exclaimed that it had to have been a mechanical engineer who designed the human body. The system of levers and pulleys is ingenious.

"No", the third student said, "you're both wrong. The human body was designed by an architect. Who else but an architect would have put a toxic waste line through a recreation area?"

I believe that the alcohol in the stomach would make an alkyl chloride, thus helping to neutralize the stomach acid: R-OH + HCl -> R-Cl + H2O. R stands for a carbon-based attachment. And with any remaining alcohol, it could attack the H. Pylori.

Barely; that reaction usually goes the other way and there's a lot more water in the stomach than there is acid.

I suspect that drinking enough alcohol to poison the bugs would poison the patient.

The heat needed to boil the water is the latent heat of vapourisation.

There's a graph of how it varies with temperature here.

http://en.wikipedia.org/wiki/File:Heat_of_Vaporization_(Benzene%2BAcetone%2BMethanol%2BWater).png

The heat needed falls as the temperature is raised.

If you raise the temperature to the critical point the heat needed to evaporate the water is zero because there's no difference between the "gas" and "liguid" phases.

Formic acid also exists and it can be made from insects.

It's also rather more dangerous than most people expect- it burns skin rather better than conc HCl does.

If it works with tap water from a cup in a pan that's been used in any normak kitchen then there's goung to be enough dust to nucleate boiling; there's no superheating to speak of.

It's a well known effect and has been for many years

http://en.wikipedia.org/wiki/Leidenfrost_effect

Incidentally I have seen lots of references to the idea that you can put a wet finger into molten lead without injury because of this effect.

I have never seen anyone dumb enough to try it and I don't want to.

That's not fair!

It's only the slow ones that can't escape.

"But wait! It "bends space!" "

So do I.

Since it has already been proved that it cannot work the only outcome of challenging him to "prove it works" will be that he wastes more time and bandwidth.

Trurl

I can construct two totally different triangles with two sides of lengths 3 and 5.

There isn't a unique solution so you cannot sensibly claim to have found "it".

I'm beginning to wonder if Trurl can't spell "troll".

I think the traditional reply is "thank you for sharing that".

;-)

I'm not actually sure I explained anything, but I'd like to think I helped.

"If the whole world would just use the SI units, which need no conversion, we wouldn't have this discussion."

With the information given you would not be able to answer the question in SI units.

You can answer it if you use calories as the unit of energy.

Incidentally, are you aware that plenty of us learned how to do this sort of thing using Joules or calories and because of that, could redo the calculations in foot poundals if needs be?

Is this the forum for "people who can only do calculations if they are set out in exactly the right format and units"?

Still you will be pleased to know that I won't be designing any bridges any time soon, though the last time I did it (a table really, but the maths is similar) I used SI units.

Sadly, (this was in the days before Google) I only had a list of maximum permissible stresses and Young's moduli in PSI so I had to redo the calculation.

I try to leave that sort of thing to civil engineers. BTW, is a civil engineer one who asks politely before building a bridge?

Also, do you look forward to the day that McDonalds sell a "hectagrammer" or are you holding out for a Newtonner (with cheese)?

The heat radiated off into space was originally stored in the "moon" when you made it.

Imagine I have a moon with a big rock on a table. A passing meteor knocks the rock off the table. The energy released is lost as heat by radiation (over time).

No violation of anything- it just lost the energy I put in to lifting the rock onto the table in the first place.

Imagine doing this with so many rocks that they wedged one-another up and didn't need the table.

Would you know how to answer this if they asked about ethanethiol rather than than cysteine?

It's essentially the same problem.

Acetone does not mix with strong solutions of NaCl or MgSO4. I don't know about CoCl2 solution, because I have not tried it, but I would not expect them to mix.

If there are two layers- one with a lot of water and one with a lot of acetone the experimental observations (a blue layer floating on a pink one) make sense.

I will use any unit of energy I like, including the barn yard atmosphere on a bad day.

Converting to Joules just so you can divide by the same number again might be good pedantry, but I'm not sure it's helpful here.

It's a pity that the Calorie and calorie get abused on food packaging but it's rare that the distinction actually troubles anyone. (Does anyone really think that a bar of chocolate might be only 1/10000 of a day's energy needs, or about enough energy for 100 days?)

People use units that suit their personal experience and the work they are doing. There's not a lot of point trying to stop that so perhaps it's better to teach people how to convert from one unit to another and also to think about the magnitude of the answer and see if it's "just plain silly".

There really needs to be a fourth option in that poll called gobledygook or word salad or some such.