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is there some clear advantage to 240v 50hz AC?

No. Frequency is largely irrelevant. The only common (although probably not so much anymore) residential application I can think of are wall clocks with synchronous motors using the line frequency to keep time. Increasing the voltage would give you more usable power out of your common 15/20A household branch circuit, but that's it. Perhaps you could lower the total number of branch circuits by going to higher voltage, but I don't know how many people would really care that they have 1/3 fewer breakers. Or you have crazy ass things like the UK ring circuit.

Take a look at a lot of your electronics and you'll see that they probably accept a "universal input" of 50/60Hz between 100-240VAC. One distinct advantage higher frequency has is allowing smaller size of components like transformers. This is why you'll see things like 115VAC @ 400Hz in aircraft.

The Rickets versus Skin cancer theory for the distribution of skin shades is just one theory.

from http://www.wonderquest.com/evolution-skin-color.htm:

'
Jared Diamond (1999 winner of the Medal of Science award and UCLA evolutionary biologist) points out flaws in these theories.

"Among tropical peoples," he writes "anthropologists love to stress the dark skins of African blacks, people of the southern Indian peninsula, and New Guineans and love to forget the pale skins of Amazonian Indians and Southeast Asians living at the same latitudes." [Emphasis mine.]

He notes that dark peoples of equatorial West Africa and the New Guinea mountains get no more UV radiation than the light-skinned folk in Switzerland, if you take cloud cover into account. ...
Charles E. Taylor, UCLA evolutionary biologist, thinks so, too. "Diamond argues for sexual selection because nothing else seems to fit," Taylor says. "This is a cop-out, of course, but it makes sense to me." ...
"It is not impossible that white skin color originated in Northern Africa," says Taylor.
'

http://www.newscientist.com/article/mg20327222.500-where-does-white-skin-come-from.html

http://en.allexperts.com/q/Evolution-3839/white-skin.htm

Or maybe it didn't evolve that way for any particular reason.

The fact that fingerprints are so conserved among primates, and some even have them on their tails which they use to grip trees as well, to me that suggests it's a functional feature. Were humans the only ones with fingerprints I would agree that it might not be an evolved feature.

We use fingerprints for identifying criminals, but clearly that's not what they were evolved for. In the absence of the conservation, had the friction studies shown a positive result, that still would not have meant it was evolved for that purpose. But the fact that primates have kept fingerprints around through multiple speciation events really makes it seem like it had some function. There's also the possibility that it is somehow necessary to develop fingerprints in order to develop primate fingers.

Annual rainfall where I live is around 1-3 metres (more slightly inland than on the coast). Let's say 2m as an average. Cumulous cloud (the kind that typically causes rain) forms at 2-16km. Picking a number somewhere in the middle, let's say 8km for the average distance rain drops fall. That means, every year, two cubic metres of rain fall 8km per square metre of ground. That's 2,000 litres, which means roughly 2,000 kg. The total energy in this is calculated as mgh, so: 2,000 x 9.8 x 8,000 = 156,800,000 J.

Unfortunately, this is wrong. A raindrop doesn't keep on accelerating all of these 8 kilometers; it will reach it's terminal velocity, at which point the deceleration due to air resistance exactly cancels the acceleration due to gravity. Since raindrops are small, their surface area is large compared to their mass, so I'd imagine the terminal velocity to be rather small - which is a good thing, otherwise we'd get our skulls crushed to powder by rain, but sadly means that we can't extract all that much power from a single raindrop.

Actually, I checked, and according to WonderQuest, the average speed of a raindrop is between 2 (for small ones) to 9 (for large ones) meters per second. Since kinetic energy is mv^2, this works out to between 2000kg * 2m/s * 2m/s = 8000J (= 0.002 kWh) and 2000kg * 9m/s * 9m/s = 162 000J (= 0.045 kWh) per square meter per year.

Since the price of electricity is about 0.07 euros per kWh where I live, and a square meter of this thing would need about 22 years to produce a single kWh under optimal conditions and assuming a 100% efficient conversion, I don't think that it is a good investment.

disclaimer - I'm not a physicist.

Having said that... I came across this - http://www.wonderquest.com/extinctions-safetyglass-magnetslasers.htm (Scroll down for pertinent info). Apparently "electromagnetic waves can bend light through an indirect, quantum effect--but to such a tiny degree that we cannot measure it." So, maybe bigger magnet = more bending = measurable?

And there's coal there too, thus proving that dinosaurs drove SUV's.

This reminds me of Freezing Frogs. Basically they fill their cells with glucose, and are actually able to freeze themselves for the entire winter and then wake up in the spring. I remember a radio show where they were saying you could freeze them over and over again, without any adverse effects.

We can thank those crazy Babylonians and their base-60 numbering system. A lot of early mathematics was done by Arabic scholars who inherited this nightmare, which is where we get the 360 degree nonsense. here is an interesting article about the origins of base 60.

http://www.wonderquest.com/black-holes-proof.htm
Summarizes very neatly the default hypothesis that they exist

This leaves aside the problem of coming up with a better theory than GR (which has been extensively tested)

After all, the theory of black holes has been contested vigorously from its inception http://en.wikipedia.org/wiki/Chandrasekhar_limit
http://www.newscientist.com/article.ns?id=dn6193

Two examples of a reasonable approximation to proof:
Massive black holes ... Here they seem to have shown that MACHOs and WIMPs do not fit the bill.
http://www.space.com/scienceastronomy/blackhole_mi lkyway_021016.html

And for a stellar mass black hole
http://www.space.com/scienceastronomy/astronomy/de ath_spiral_010111.html

Those lefties want to leave it there, can you believe that? It is the will of God that we dig it up and burn it -- NOW!

Yeah, thanks to the damn metric system, or english system or whatever it's called that they use in England, this really does get confusing. A billion(Brittish) == a trillion(US)

.. with a decent physics-looking explanation: an interview with April Holladay on Wonderquest.com.
p.s. I hope this venture succeeds.