swansont

As was noted, it's a problem when you let idealism drive science. Also, when you have politicians and bureaucrats run science, you can get an obscene version of Pascal's wager - fund something that, if it works, will pay tremendous dividends. But they are unable to distinguish between "difficult" and "impossible" - they just see what the payoff would be. NASA has funded a version of Podkletnov's antigravity experiment, for example.

This site gives some efficiencies. 2% for incandescents is pretty close. But LEDs aren't much more efficient, according to the list. Halogens are. Halogens run hotter, which means they give a whiter spectrum - normal incandescents look yellow - and hotter means a larger fraction of the total energy is in the visible. Which also explains why lower power incandescents are less efficient; they should be a little cooler. Another advantage of halogens is that they redeposit the tungsten on the filament, and the bulb lasts longer. Note that the link I give is the ratio of visible to total radiated power - it ignores any inefficiency in generating the EM spectrum in the first place.

Except you can't figure it that way. The potential difference is measured from ground to cloud, and won't be equal to what is measured across the cage. The current will be limited by the resistance of the atmosphere, similar to how the current through a resistor doesn't get larger when you get to the leads, which have small R. It's a series circuit. Typical discharges are of order 5,000-20,000 amps, though larger values can certainly occur.

I thought she was a riot!

It was also done in degrees C, which gives an answer of 37. Then a sloppy conversion to F was done, incorporating an extra significant digit, which gives the illusion that anything other than 98.6 F is abnormal.

<Sigh> Once again, I will point out that this is just anomalous dispersion. No violation of causality or special relativity occurred. The waves of the various frequencies that made up the wave packet were resorted, so that the peak shifted. The beam was reshaped. It's sleight-of-hand. A physics parlor trick. The peak came out earlier than it was supposed to, and the flowers are still standing. It's more bad journalism than anything else - the notion that "nothing can exceed c" is relativity oversimplified to the point that it's wrong.

No, that's not it. The superconductors aren't cooled to zero, since that's forbidden by the third law of thermodynamics. Superconductivity happens because the electrons pair up (Cooper pairs) and become Bosonic, which changes their interactions with the surrounding lattice. BCS theory is the basis of superconductivity.

They haven't cooled wires anywhere close, as compared to other things that have been cooled (BEC). R for a superconductor isn't just small, it's zero.

No, they've gotten stuff to work above liquid nitrogen temperatures - 77K - for some time now. YBa2Cu3O7-x superconducts at temperatures as high as 94K.

You aren't Emily Litella, by any chance? Never mind...

Van de Graff generators

A man was wandering around a fairground and he happened to see a fortune-teller's tent. Thinking it would be good for a laugh, he went inside and sat down. "Ah....." said the woman as she gazed into her crystal ball. "I see you are the father of two children." "That's what you think," said the man scornfully. "I'm the father of THREE children.". The woman grinned and said, "That's what YOU think.

Annoyed by the professor of anatomy who told racy stories during class, a group of coeds decided that the next time he started to tell one they would all rise and leave the room in protest. The professor, however, got wind of their scheme just before class the following day, so he bided his time: then, halfway through the lecture, he began. "They say there is quite a shortage of prostitutes in France . . ." The girls looked at one another, arose, and started for the door. "Young ladies," said the professor, "the next plane doesn't leave until tomorrow afternoon."

I only scanned the article, but they don't appear to have considered the possibility that the plane wasn't level at impact. All of the drawings show, and calculations seem to assume, a level plane. In their "(Don't) Try this at home" section, I didn't see an answer to their challenge. But I've had campfires into which aluminum cans were crumpled and dropped, with no evidence of them to be found the next day.

momentum and mass aren't the same thing.

Rubber's a good insulator, but I don't think it will keep out EM radiation, just current. Wood's a good insulator, too, but doesn't do much as far as shielding goes. You no longer have a grounded surface, so no Faraday cage. The reason that the surface will be an equipotential is that charges feel a force when there is a potential difference, and this causes them to move in such a way that they will minimize their energy. If you have a poor conductor, it will take longer to equilibrate. I'm guessing that the equilibration time would be related to the frequency of radiation that would be passed by the material. e.g. if the material took a millisecond to respond, radiation higher than about a kHz would easily be passed.

AFAIK it still holds that there is no "center" to the universe, and the measurement of time depends on your kinetic and gravitational potentials. And the kinetic term depends on your frame of reference. I don't think you will get very far with defining things this way, especially since the definitions are vague to begin with.

Revolves.

They were equivalent, weren't they? Anyway, surface tension isn't the whole story. Adhesion to the bottle matters as well.

I'm sure that's what they said about the Maginot line.