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December 29

meteorites from EARTH to Mars, rather than vice versa

Hi, what i read is that about a ton of meteorites of mars origin land on earth every year. How often would the reverse happen given Earth's stronger gravity? Less often I'm sure but how less often? Is there an approximate formula based on gravitys and distance from sun etc? Thanks68.65.169.66 (talk) 01:20, 29 December 2012 (UTC)

When was the last time a meteorite impact on Earth was storng enough to eject material into space? This is not just a matter of stronger gravity -- it's also a matter of Earth having a dense atmosphere that all but prevents any Earth material from being ejected into space as meteors. 24.23.196.85 (talk) 01:37, 29 December 2012 (UTC)

I don't know when the last one was, but a meteorite impact on Earth, if it did bang stuff off of earth, even many millions of years ago, could be a continuing source of meteorites to Mars. Also, i wonder about (Earth)volcanoes shooting material away from Earth.68.65.169.66 (talk) 02:09, 29 December 2012 (UTC)

No volcano has ever been powerful enough to launch stuff into space -- the rocks fly thousands of feet into the air at most, while the volcanic ash usually goes up into the stratosphere and just hangs there for some weeks. 24.23.196.85 (talk) 02:51, 29 December 2012 (UTC)

No volcano on Earth. There have been (water) volcanoes that launched material into space. Some of Saturn's rings are from one (see Enceladus (moon)). StuRat (talk) 04:05, 29 December 2012 (UTC)

No volcano in historical times has come anywhere close to achieving an orbital launch. Large modern eruptions send volcanic bombs (i.e. large rocks) up to 500 m or so above the volcano. However, we have good evidence of volcanic explosions 10-100 times larger having occurred over geologic times. This makes it likely that at least occasionally volcanic eruptions might send rocks miles into the sky, and just possibly the very largest eruptions might approach escape trajectories. Back in the early twentieth century, there was a theory in geology that large, suborbital volcanic ejecta was responsible for creating impact craters (e.g. verneshot). We now know that most impact craters have a extraterrestrial origin (i.e. meteors), but I don't think one can completely rule out the possibility of an extremely large, extremely rare (e.g. 1 per 100 million years) volcanic eruption being capable of launching some rocks off the planet. If it has ever happened though, it certainly doesn't happen often. Dragons flight (talk) 05:12, 29 December 2012 (UTC)

What about meteorite impacts?64.9.234.141 (talk) 05:58, 29 December 2012 (UTC)

It would require a pretty big meteorite impact. Still not very common, since big impacts are themselves rare—maybe once every 10 million years or so at most. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:59, 29 December 2012 (UTC)

I thank you for your answer. I'm not sure how you get your estimate, or even if your estimate is at least from intuition gained from experience and study. My original question was how much Earth material gets to mars relative to the reverse process, (which hopefully the scientists who claim about 1 ton/year have their reasons). But if you are correct that such meteorite impacts are on average 1 every 10 million years, how much transfer would we expect to mars? Is it likely or unlikely that there been in the last 100million years meteor impacts that ejected millions of tons of matter from Earth?(I ask the large amount of a million tons because I bet the odds of any given particle of it ever getting to mars, let alone in a given year, are small.) Could we say perhaps then that extremely tiny amounts of Earth end up on Mars, like a teaspoon per year?Thanks again.64.9.234.141 (talk) 08:02, 29 December 2012 (UTC)

• Terrene meteorites in the moon: its relevance for the study of the origin of life in the Earth Here somebody wants to look what the earth meteorites look like to search for the beginning of life on earth.
• doi:10.1016/0012-821X(94)00232-N Here somebody wants to know how life spread from earth with meteorites.
• Testing interplanetary transfer of bacteria between Earth and Mars as a result of natural impact phenomena and human spaceflight activities Bacterial transfer in the solar system. --Stone (talk) 09:06, 29 December 2012 (UTC)

I don't see how anything ejected from Earth could make it to Mars -- Mars is tens of millions of miles farther from the sun, and the ejected material would have to overcome the sun's gravity for that great distance. Duoduoduo (talk) 13:57, 29 December 2012 (UTC)

It takes an enormous amount of energy to get off the Earth. The amount of energy to get from Earth to Mars is only about 4 times larger than the amount required to escape the Earth. If you have any scenario that can get you off the Earth, it isn't hard to imagine a scenario with a few times more energy that gets you to Mars. Dragons flight (talk) 15:23, 29 December 2012 (UTC)

While the escape velocity from the surface of Earth is more than double that of from Mars (11.2 km/s vs 5.0 km/s), I believe that Duoduoduo is mistaken if they think that once the object has escaped from the planet, then somehow the sun's gravity makes it much easier to travel from Mars to Earth than vice versa. Can someone more familiar with orbital mechanics speak to this point? -- ToE 18:18, 29 December 2012 (UTC)

Well, if you just put an object with no initial momentum just outside Mars's gravity well, it will fall toward the sun, crossing Earth's orbit on the way. But if you put an object with no initial momentum just outside Earth's gravity well, it will also fall toward the sun, hence not crossing Mars's orbit. Duoduoduo (talk) 22:10, 29 December 2012 (UTC)

Hmmm, but a rock that falls from near Earth orbit should return near to the same distance over and over again... and if so, is there a chance that it will interact again and a gravitational slingshot will get it out some distance? (but then again, it shouldn't be moving very fast relative to Earth, so it shouldn't slingshot very far... I think...) Wnt (talk) 23:16, 29 December 2012 (UTC)

But that "no initial momentum" (relative to the Sun) assumption is wrong. Anything starting from Earth will have about the same initial momentum as Earth, and anything starting from Mars will have about the same initial momentum as Mars. Therefore, it would take just as much energy, but in an opposite direction, to force an object from an Earth orbit to a Mars orbit as vice-versa. StuRat (talk) 23:21, 29 December 2012 (UTC)

"No initial momentum" was just intended as an unnecessary simplifying assumption to focus on the issue at hand -- the sun's gravity. This seems simple to me -- from Mars to Earth the sun's gravity is helping, while from Earth to Mars you're working against the sun's gravity. Duoduoduo (talk) 13:09, 30 December 2012 (UTC)

No, no, StuRat is correct. The "No-Initial-Momentum" assumption is not a good first approximation. Look at Delta-v budget#Delta-vs between Earth, Moon and Mars for an good picture on that topic. It takes about 10 km/s to go from Earth to Low Earth Orbit, and much less than that to reach a Mars Transfer orbit. And the Earth slingshot idea seems quite viable to me. Dauto (talk) 15:55, 30 December 2012 (UTC)

Forget the "No-Initial-Momentum" assumption -- as I said, it has nothing to do with my point, and I already retracted it. You say that it takes a positive boost to get out to Mars. Part of that boost is needed because you're fighting against the sun's gravity. My point is that it doesn't take that same boost to get from Mars to Earth, since the sun's gravity is helping rather than hurting. In other words, my point was simply that the sun pulls things toward the sun. Or can you get from Earth to Mars without overcoming the sun's gravity?? (And I too like the Earth slingshot idea.) Duoduoduo (talk) 16:48, 30 December 2012 (UTC)

What we're trying to explain is that it takes just as much energy to force an object in orbit about the Sun, at Mars, down to an Earth orbit, as to do the reverse. Think of the kid's experiment where you swing a ball on a string around your head. It wants to go outward, and it takes an active force to pull it inward. If this wasn't the case, then everything would have fallen into the Sun long ago. And the size of the object doesn't matter (much). Jupiter can orbit the Sun just as a speck of dust can.

Now, you are correct that an object with no initial momentum relative to the Sun would fall into it, but this just won't be the case with either Mars or Earth meteorites. StuRat (talk) 00:20, 31 December 2012 (UTC)

I'm looking for some intuition as to why the required energy would be identical in either direction. Is it this?: Denote orbital velocity to maintain a Mars-radius orbit as m and to maintain Earth-radius orbit as e. To go from Earth-radius orbit to Mars-radius orbit, the entirety of what you have to do is to decelerate from e to m, and to go from Mars-radius orbit to Earth-radius orbit the entirety of what you have to do is accelerate from m to e. Since the absolute change in velocity is the same in either case, the energy is the same in either case. Is that it? Duoduoduo (talk) 16:03, 31 December 2012 (UTC)

Yes, that's a good way to picture it. StuRat (talk) 06:43, 1 January 2013 (UTC)

But that only gives equality of energy needed if in both directions you are slowing down or speeding up to the second planet's orbital speed. But a meteorite doesn't have to do that -- it can just hit while attempting to cross the planet's orbit, without havng to enter orbit. So I return to my original notion that a key difference is which way the sun is pulling the meteorite. Duoduoduo (talk) 16:16, 1 January 2013 (UTC)

And I return to my statement that any meteorite kicked loose from a planet will have an orbital speed about the Sun very similar to the source planet. The Earth is orbiting the Sun at 29.78 km/s, and has an escape velocity of 11.186 km/s, while Mars orbits at 24.077 km/s with an escape velocity of 5.027 km/s. So, for an object to "fall" from Mars to the Earth, it would have to leave Mars at nearly 5 times the escape velocity, in just the right direction, to not have any momentum relative to the Sun. This is extremely unlikely, and the much greater amount of energy required to do this (rather than just barely escape Mars) would vaporize the object, so it would be gas, not a meteorite, and probably split Mars in half in the process. StuRat (talk) 03:02, 2 January 2013 (UTC)

Please bear with me, as I'm trying to learn something here. What I'm saying is I think analogous to the following from Delta-v budget#Near earth objects:

The delta-v to return from them [near earth objects] are usually quite small, sometimes as low as 60 m/s....However, the delta-v to reach near earth objects is usually higher, over 3.8 km/s

Duoduoduo (talk) 17:04, 30 December 2012 (UTC)

Following the reference from that section, I see that the 3.8 km/s delta-v is from Low Earth Orbit to the NEA, so most of that is needed to escape Earth's gravity well. -- ToE 18:01, 3 January 2013 (UTC)

From an earlier post: When was the last time a meteorite impact on Earth was storng [sic] enough to eject material into space?

Well, I doubt it was the last, but there's at least one big one, though it obviously didn't make it to Mars. — The Hand That Feeds You:^Bite 00:08, 31 December 2012 (UTC)

Even though we haven't had any large impactors here on Earth very recently - my "gut feel" wonders whether it might be the case that the velocity of the debris will follow some kind of (gaussian?) velocity distribution? While the average velocity might not be enough to reach escape velocity - wouldn't it be possible for a freak particle out on the far end of the distribution to make it out? The energy equation ought to allow it - providing the piece of debris is small enough. SteveBaker (talk) 04:28, 31 December 2012 (UTC)

Yes, but those small particles would burn up in the atmosphere of Earth, unless you're talking about an impact so great it blows a good bit of the atmosphere away with it. And that distribution would also mean the Earth would be surrounded by a ring of all the objects which failed to reach escape velocity, although that ring might be rather unstable, due to the Moon, resulting in more of a cloud. StuRat (talk) 06:46, 1 January 2013 (UTC)

Confusion in article Atomic mass and bond order greater than 6

1. While reading the article Atomic_mass#Mass_defects_in_atomic_masses, I read in the linked section "deviation is positive or negative". What does deviation and positive/negative mean in the context ?
2. No two elements in the periodic table can form a bond with greater order than 6. Why ? Sunny Singh (DAV) (talk) 13:51, 29 December 2012 (UTC)

One atomic unit of mass is 1/12-th of the mass of Carbon-12 atom. Hydrogen-1 (proton+electron) has mass higher than this unit. So, the mass deviation is positive. Atoms heavier than carbon (up to nickel) generally have negative deviations. Ruslik_Zero 15:37, 29 December 2012 (UTC)

For your second question, see this article. Septuple bonds are not possible between two atoms of any elements with atomic numbers 100 and below. They might be possible in the early superactinides, but their half-lives may not be enough for chemical characterization (except, possibly, for a few elements around the magic number Z = 126). Double sharp (talk) 07:17, 30 December 2012 (UTC)

We have a Sextuple bond article that includes that ref. DMacks (talk) 20:45, 30 December 2012 (UTC)

Biochemistry of Seizures

What are the biochemical processes involved in a seizure. Is it different for every cause I.e.for low blood pressure, transplant rejection, high fever, allergy etc. — Preceding unsigned comment added by 176.27.208.210 (talk) 16:39, 29 December 2012 (UTC)

Don't know, but in the case of an epileptic seizure, dogs can apparently predict them, which points to a chemical odor, which means there must be chemical reactions leading up to it. StuRat (talk) 23:24, 29 December 2012 (UTC)

I think you're probably correct about chemical odors. But it seems to me there some chance that dogs detect it by other means instead. Their eyes are very sensitive to motion, perhaps especially of human motion, and they hear at some frequencies humans can't.199.33.32.40 (talk) 00:25, 30 December 2012 (UTC)

Thanks for your answers. Im pretty sure that every biochemical process in the human body involves chemical reactions and that most symptoms of illnesses are also caused by biochemical reactions. My question is specifically which biochemical processes/reactions cause seizures. 176.27.208.210 (talk) 02:48, 30 December 2012 (UTC)

I don't think that's true. A heart attack can be caused by a blockage, and a stroke can be caused by a break in a blood vessel. Neither requires any chemical reactions immediately leading up to it. StuRat (talk) 03:13, 30 December 2012 (UTC)

True but surely there's chemical processes which lead to blockages or burst vessels. 176.27.208.210 (talk) 13:23, 30 December 2012 (UTC)

Seizures have many causes (e.g, hyponatremia, hypoglycemia, hypocalcemia). The muscle activity and alterations of breathing can produce some common post-ictal chemical changes (e.g., elevated prolactin). Doctors pay more attention to the chemistry of possible causes than to the chemistry of the consequences. alteripse (talk) 06:27, 30 December 2012 (UTC)

• Rather than writing a long response I'm just going to give a pointer to our article on epilepsy. Looie496 (talk) 14:32, 30 December 2012 (UTC)
• The OP seems to be asking for an explanation at the wrong level of causation. Seizures are neurological events, and have to do with malfunctions of neurons and their signalling of each other and the body. See action potential and neurotransmitter for relevant articles. There isn't some sort of general chemical reaction going on like combustion that causes a seizure as such. All the normal sorts of chemical events that are going on in normal functioning will be found during seizures, but in the circumstance of improperly coordinated actions of the cells. Asking for a chemical explanation as such is about as relevant as it would be to ask what sort of chemical reactions are going on during a senate filibuster or a ferry capsizing. μηδείς (talk) 20:39, 30 December 2012 (UTC)

One intriguing piece of the puzzle has to do with a fall in the carbon dioxide tension before a seizure, particularly in patients with fever or hypoxic-ischemic encephalopathy. A fall in pCO2 is thought to lower the seizure threshold. The relationship between CO2 and seizures has been studied since at least the 1920s, but specific clinical interventions (like supplemental CO2 administration) have only been investigated in the last few years. I wish I understood it better on a biochemical level, but the potential clinical applications are exciting. EricEnfermero ^Howdy! 23:30, 30 December 2012 (UTC)

December 30

Morse code

Two questions in one: (1) How many chars/min can a skilled operator transmit in Morse code (assuming that he/she has already encrypted the message beforehand)? (2) On average, how long did it take for the Gestapo to locate a radio operator using direction finding? Thanks in advance! 24.23.196.85 (talk) 05:19, 30 December 2012 (UTC)

2) This will depend on whether they are smart enough to send the message from a moving vehicle, or at least restrict themselves to short messages, each broadcast from a new location. StuRat (talk) 05:38, 30 December 2012 (UTC)

(2) I meant how long can an operator "safely" transmit continuously from one location and not have the Gestapo kick in the front door. 24.23.196.85 (talk) 05:45, 30 December 2012 (UTC)

Question 1 is answered in the Morse Code article. Zoonoses (talk) 07:00, 30 December 2012 (UTC)

Depending on what you want this answered for, you may need to take into account some additional facts not covered in teh Wiki article:-

1. While good operators can send and recieve at 40 word per min or more, that is for a perfect link. In a shortwave or medium wave radio link, fading and noise may interfere with reception - the operators will then send as slow as required. With good narrow band recievers, slow enough morse can be copied accurately at signal stengths far below the noise level (hiss, static, machine noise etc) that would obliterate voice. That is the advantage of morse - you can almost always get through when nothing else will, and it nees only simple low tech equipment.

2. Military operators have always been trained in "short codes" - combinations of 3 or 4 letters coresponding to entries in a list of common messages often sent. For example in the NATO code used by navies in and after WW2, to transmit from a flagship the message "I am going to turn right onto magnetic course 290 degrees" could be transmitted as something like "XDEX90".

3. For WW2, German operators were trained to send and recieve in moving noisy environments using specially built rigs closely simulating the noise, vibration, and shock as would be experienced in aircraft and vehicles & tanks under way and under attack. Other forces probably had similar training.

In France, the Gestapo & regular German forces had a simple way of tracing a covert transmitter located in a town somewhere. Back then, a radio transmitter either needed big batteries (the size of a car batteries) or were powered from house current power mains. Usually, house current was the choice. Upon detecting a transmitter and getting a rough direction in seconds they would go to the substation and cut the power for just as long as it took to move the switch up and down - say a fraction of a second. If a matching break in transmission was detected, they knew they had the right area. If transmission continued, they would then race to a likely pole switch feeding a street and do the same. Repeat as required. In this way they could identify the correct street and sometines the correct block of flats within minutes. Then they would just block the street off and thoroughly search every dwelling.

Wickwack 58.167.246.100 (talk) 07:38, 30 December 2012 (UTC)

There was a 1960's spy movie where they did the power cutting to determine which apartment in a building the spy was transmitting from, but in WW2 they used direction finding rather than cutting the power to parts of a city to locate a spy. Any sensible spy would suspend transmitting when the power went off and back on. It would be very time consuming to drive around a city and climb poles to cut power for transmitter locating, and the message would likely be complete before you could achieve more than one such cut. Spy transmitters of WW2 were generally made to work off batteries, in any event. A WW2 US radio operator I know said she could operate at 40 WPM, She had no trouble transmitting encrypted as opposed to plaintext. That is what she was trained on. Edison (talk) 22:28, 30 December 2012 (UTC)

Hmmm, can't tell you the history but just thinking about this it might be worth reconsidering. The point is though that the spy has no way to know that the power is about to be cut, and if the spy depends on electricity, or perhaps even electric light, then once the power is off the transmission will stop. In theory you could have people shut off power to a different little part of a city every ten seconds and figure it out to some high level of precision. I suppose one appealing aspect of the scheme is that if the spy is transmitting by some kind of link or mechanism you can't detect, then you might track where the spy himself is located rather than coming up with the triangulated position of a walkie-talkie taped to a telephone or whatever. Wnt (talk) 00:28, 31 December 2012 (UTC)

Also, if the message is in code, then it's likely to be much slower to transmit than plaintext for a couple of reasons:

• Try using handwriting or typing to copy an English sentence - then try writing or typing a random string of letters or numbers of the same length. It's much harder. If I ask you to type "The cat sat on the mat" - 22 characters, you can do it in probably a couple of seconds. If I ask you to type "RKA VXL ZQG SFG OGH KS"...it'll take you much longer. You can read "The cat sat on the mat" almost instantly, hold it in your mind and just type it out as fast as your fingers can move. "RKA VXL ZQG SFG OGH KS" is probably something you can only read three or maybe six characters at a time.
• If you make a mistake typing English text ("The cat sqt on teh matt") - then the guy at the other end can still read it. But if you make a mistake with some kinds of code - then you're probably going to produce gibberish when it's decoded. So much more care is needed. The message may need to be sent more than once so that the decoders can be sure you didn't make any mistakes.

So this isn't so much about morse code proficiency as about the way the code is handled. Many codes were simple English sentences: "The aardvark sees the mountain" might mean "I need you to attack the weapons depot north of Berlin at the time we previously agreed two nights from now".

SteveBaker (talk) 17:50, 30 December 2012 (UTC)

I disagree with Edison on the effectiveness of the power cutting method. I think he has missed that it was used in conjunction with rapid direction finding. Back then covert transmitters were MF of HF. In a city of well developed suburb, sufficiently accurate direction finding on HF to be used on its' own is not possible. Now, in WW2, if you were a French peasant, and a truck full of German soldiers comes down the street at speed, you didn't hessitate, you got out the way.

Another aspect to consider is that back then electricity distribution was open wires on poles, not underground cable. In open wire distribution, the occaisonal short from wind blown debri or birds happens from time to time, so electricity companies use reclosers. Reclosers are a circuit breaker that trips on overload same as a normal circuit breaker, then waits a predetermined delay, then reconnects. If the overload is still there it trips out again. But often the overload has gone, saving the electicity company manual intervention. So folk get used to short breaks and think nothing of it. Aslo, there was a war on. Short breaks in power happens in war.

However, Edison is quite correct in saying operators have no difficulty is transmitting (or recieving) coded messages or random sequences of characters as compared to plain text. This is partly due to training, and partly due to the nature of morse code. When keying, you think letter by letter, not word by word, as 40 words per min (about one letter per second) is actually a slow process.

Lastly, when transmitting an encrypted message, you NEVER re-transmit just because the recieving end didn't recieve all the characters. You compromise the coding security if you do. It was the (actually quite rare) mistakes like that that enabled the British to read vast quantities of German military traffic. What you do is leave the recieving end to make the best of it, or if necessary, wait a bit and encrypt a different text that has the same ultimate effect.

Wickwack 60.230.218.203 (talk) 02:28, 31 December 2012 (UTC)

You and I know that you shouldn't retransmit (well, not for some classes of code) - but back in WWII, it's likely that only a few people in Bletchly Park knew that...evidently the entire German military was unaware of this particular decryption exploit! SteveBaker (talk) 04:34, 31 December 2012 (UTC)

Perhaps. But I have a copy of Alan Turing - The Enigma, by Andrew Hodges, and some textbooks on encryption. These all make it clear that:-

1. The Germans were properly trained, but never the less made mistakes.

2. On of the less common mistakes that they made was to re-tramsit messages, and that did occiasonally help Bletchly chaps.

3. Their navy had separate encription/coding schemes for habour comms, fleet operations, and weather reports. The British could sometimes pickup habour comms and decript the relatively simple code. Then, match it up with the same thing transmitted using Fleet Ops encryption. They also matched up decripted weather reports also repeated on Fleet Ops. Big, big mistake. Once the British cracked a weather report and matched it to a same length message on Fleet Ops that day, they had the day's key to all the other Fleet Ops messages.

4. A few German operators, if they were not busy with official messges, would send common nursery rhymes (of the Mary had a little lamb sort), both to practice and maintain speed, and to ensure the radio link was available at all times. Big mistake. Once Bletchly realised that was what they were doing, they looked in light traffic periods for messages matching the length of common German rhymes and concentrate on those to get the day's key.

5. German operators did have one aspect of faulty training. They would commonly send messages with polite preamble, as in: TO General Berkhead FROM Captain Nichtwhitt SUBJECT Seizure of Town. Heil Hitler Blah Blah Blah ... Blah. Bad mistake. Never use standard forms in encrypted radio messages in a war. And never never use salutations like "Heil Hitler" in lots of messages.

6. The biggest mistake of all is that the German top brass, when faced with too many coincidences (as in British depth charge equiped aircraft intercepting German submarines far too often, or British merchant convoys diverting just after an order to submarines to intercept them), assumed that the British could not be reading the encrypted radio messages becasue a) the enigma encryption method was unbreakable (it essentially was, if used correctly every time) and their operators were properly trained. So instead of looking at procedures, they wasted a lot of time looking for harbour spies. And they assumed that Bristish radar was a lot better than it was, and better than was and is technically possible.

So, don't rule out that British operators were trained and did know not to re-transmit messages. Wickwack 120.145.54.24 (talk) 05:20, 31 December 2012 (UTC)

A clarification on the issue of re-transmitting: I'm not aware of any attack where two transmissions of the same cyphertext gives an attacker more information than one transmission; all the attacks I'm aware of require transmission of two different encryptions of the same plaintext. --Carnildo (talk) 03:26, 1 January 2013 (UTC)

Correct. If two copies of the same encrypted text somehow gave an attacker some advantage, he could make duplicates for himself - with carbon paper, or a mimeograph machine, or a pencil. There seems to be an above-average amount of wooly thinking in this thread. Zoonoses (talk) 06:20, 2 January 2013 (UTC)

[un-indent] Thanks for the info, everyone! So, 40 words/min on average, huh? That means that the transmissions can be kept very short indeed -- the one radio message I have so far in my novel has only 26 words (including agent ID, security tag and so on, but excluding the commas, stops and the final "over"), so it would take Blanche only about 40 seconds to transmit. I don't think even the best DF team can home in on something this short. (Francois will get to transmit the next message, but I intend to keep it similarly short.)  :-) 24.23.196.85 (talk) 05:45, 31 December 2012 (UTC)

No sweat. Note that punctuation was not normally sent. The word "over" only occurs in 2nd rate TV shows and novels. The reciever knows you've stopped transmitting anyway. Wickwack 120.145.145.21 (talk) 10:48, 31 December 2012 (UTC)

Thanks, Wickwack for a really helpful discussion! Clarification requested (or correction of my top-of-the-head arithmetic): the above says the transmission rate was about "40 words per min (about one letter per second)". The latter means 60 letters per minute, which combined with 40 words per minute means 1.5 letters per word. What am I missing? Duoduoduo (talk) 16:15, 31 December 2012 (UTC)

You've caught out my shocking mental arithmetic due to multitasking, and erroneous use of "letter" where "word" should go. 40 WPM equates to 0.67 words per second or 1.5 seconds per word as you say. Taking the standard typist's approximation that 1 word is 5 characters, that's 0.30 seconds per character. However my comments that sending morse is a slow process that encourages working on a charater by character basis and not thinking in words like we do when reading still stands. Someting else that may or may not be relevant to you is that if the channel gave good clear reception, military forces sometimes used time compressed morse. This reduced the probability of inteception and direction finding. And for submarines, it reduced the time required fully surfaced - always a good thing - surface travel means enemy planes can spot you, and and the rolling and pitching in a heavy sea can make sailors sick. The sending operator recorded the message first and then sent it at high speed. At the recieving end the message was recorded again (eg on a wire recorder) and played back at slow speed to read it. Covert agents would not have used this method however. Electronic equeipment back then was very bulky and heavy, and best kept as simple as possible for relaibility. Wickwack 124.178.61.38 (talk) 16:47, 31 December 2012 (UTC)

I'm afraid that 40 wpm claim is a load of rubbish. Very few trained operators can copy 40 wpm, even under perfect conditions. Almost no one on Earth can send 40 wpm with a straight key, especially under trying, wartime conditions. Seek out your local ham radio operator for some practical instruction. Zoonoses (talk) 06:14, 4 January 2013 (UTC)

Lorcaserin and what else? - FDA approved Obesity medication

i'v heard that except Lorcaserin, there's gonna be another Med', what is it's name? thanks. — Preceding unsigned comment added by 109.65.115.101 (talk) 06:32, 30 December 2012 (UTC)

Orlistat. OsmanRF34 (talk) 16:40, 30 December 2012 (UTC)

No. Orlistat was taken out. it gotta be something else. 109.65.115.101 (talk) 06:13, 31 December 2012 (UTC)

Is it Qsymia Article located here. Livewireo (talk) 19:21, 2 January 2013 (UTC)

What kind of chemicals would be produced when a Polyethylene plastic bag is burnt? How?

Sometimes I can smell a bit odor, so I guess it is not burnt into just carbon dioxide and water.--Inspector (talk) 09:54, 30 December 2012 (UTC)

First the long polymer chains can be broken down into alkenes and alkanes. These may give the waxy smell. There may also be partial oxidation of these to an aldehyde or primary alcohol. Graeme Bartlett (talk) 11:58, 30 December 2012 (UTC)

Combustion#Reaction mechanism suggests it starts with a hydrogen atom being stripped off by oxygen. The radical part of the polymer is highly reactive and can then further react with O₂ to form a peroxyl radical, which in turn can steal another hydrogen atom to make another radical and a peroxide. Graeme Bartlett (talk) 12:14, 30 December 2012 (UTC)

Of course, if you're just burning plastic bags - there is a good chance that it's not polyethylene anyway - there are lots of other materials used in plastic bags these days. Plastic film lists Polypropylene, Polyester, Nylon and Vinyl - along with various bioplastics. There are also things like dyes, plasticisers, release agents and who-knows-what involved in the combustion processes here. SteveBaker (talk) 17:41, 30 December 2012 (UTC)

For what it's worth, PVC and polyurethane are particularly nasty -- the former releases hydrogen chloride during burning (and often some chlorine gas as well), while the latter releases such highly toxic gases as prussic acid and formaldehyde. NOT a good idea to EVER burn those two! 24.23.196.85 (talk) 05:49, 31 December 2012 (UTC)

Does infrasonic results resonance in human body?

My physics teacher, as well as many Chinese websites [1][2][3][4][5], says that infrasonic results resonance in human body, thus 'infrasonic weapon' can be made. But Chinese Wikipedia says infrasonic doesn't damage human tissues, and English Wikipedia says it just cauese pain in the ear drums. I can't find anything about 'infrasonic weapon' which work by making resonance to human body on English websites, can anyone provide any information about it, please?--維基小霸王 (talk) 12:24, 30 December 2012 (UTC)

There's something in the Vladimir Gavreau article, but the article seems to think that it may have been imaginary. 71.79.67.209 (talk) 13:05, 30 December 2012 (UTC)

It seems diffrent because the frech imaginary one doesn't kill people by resonance.--維基小霸王 (talk) 15:00, 30 December 2012 (UTC)

There is a real lack of good research on this topic. To give a fairly bad example, the only recent paper I found in NCBI for infrasound and nausea is a review at [6] that deprecates the idea, though the authors very reluctantly cite (Leventhall G, Pelmear P, Benton S. A Review of Published Research on Low Frequency Noise and its Effects. Department for Environment, Food and Rural Affairs, London, UK; 2003. Yuan H, Long H, Liu J, Qu L, Chen J, Mou X. Effects of infrasound on hippocampus-dependent learning and memory in rats and some underlying mechanisms. Environ Toxicol Pharm. 2009;28:243–247. doi: 10.1016/j.etap.2009.04.011. Leventhall G. Infrasound from wind turbines - fact, fiction or deception? Can Acoust. 2006;34:29–36.) that loud infrasound does cause symptoms similar to those reported by subjects.

As someone who simply hears "infra"sound, some of the unquestioned assumptions of these researchers are very annoying - for example, they point out that infrasound "is emitted from road vehicles, aircraft, industrial machinery, artillery and mining explosions, air movement machinery including wind turbines, compressors, and air-conditioning units," without recognizing that indeed each and every one of these things is also annoying for the same reasons (but most of the other sources are mobile or intermittent). They furthermore fail to appreciate that infrasound "from natural sources like meteors, volcanic eruptions and ocean waves... Indeed, many mammals communicate using infrasound" is the reason why infrasound can be disturbing - because it is a warning of movements of substantial amounts of mass. They fail to appreciate that natural infrasound from wind, made up of multiple frequencies and ever-changing, can have a soothing quality. They also fail to appreciate the chief annoyance of infrasound, which is that unlike high-pitched sound that will not penetrate a window, or low-pitched sound that won't penetrate a wall or a pillow, infrasound seems to penetrate absolutely everything (except water). Now, to give them some credit, windmills I've encountered actually do produce mostly sound in high-pitched frequencies, but if you had a house next to one all you'd hear indoors would be the infra part, however large or small that may be.

Most crucially, however, their paper illustrates the absurdity of some of the sound figures given, because it actually makes use of measurements in dBA, a scale which is based on the idea that infrasound is inaudible and therefore is not even considered in taking sound measurements! All other scales either do not "normalize" sound to exclude those frequencies, or do so to a lesser degree. Wnt (talk) 19:56, 30 December 2012 (UTC)

The type of resonance that could occur in this case would be an acoustic standing wave. This requires a structure that is some multiple of a quarter of a wavelength (see e.g. Acoustic_resonance#Resonance_of_a_tube_of_air). Since the speed of sound in the human body (mostly water) is about v = 1500 m/s (speed of sound#water) and infrasound has frequencies below f = 20 Hz the body would need to have a length of at least ${\frac {v}{4f}}\approx 20{\text{ m}}$ to resonate. At high enough powers anything will be dangerous, but for ultrasound it will not be due to resonance. Ulflund (talk) 20:15, 30 December 2012 (UTC)

Not correct. A mass suspended in an elastic medium will resonate if the frequency is equal to 1 / (2Π (m.c)²) where m is the mass and c is the elastic compliance. Consider a loudspeaker: Quality loudspeakers as made with cone resonances as low as 20 Hz even with a cone diameter of only a few hundred mm. Thus it is quite possible that internal organs in the body could resonate at low frequencies. Wickwack 60.230.218.203 (talk) 02:37, 31 December 2012 (UTC)

I don't know about resonance, but I do know that at high volume, a particular frequency range may cause lethal cavitation to occur in the body. Plasmic Physics (talk) 06:28, 31 December 2012 (UTC)

Lethal cavitation is a process where the compression and decompression within the body (soundwaves travelling through it), causes soft body tissue to liquefy. There is at least one recorded death from lethal cavitation, where a person experimented with infrasound, and unknowingly found the correct range and generated a sound at elevated volume for only 3 seconds. He was paralysed and killed within that time. He was found intact, albeit with liquid brain matter exuding from his ears, burst bladder, basically if it was not for his skin, he'd have to be taken away in a bucket. Plasmic Physics (talk) 06:47, 31 December 2012 (UTC)

, if you please --Jayron32 06:54, 31 December 2012 (UTC)

About that, I saw it on a documentary on the C.I. Network or Dicovery Network. I don't remember what it was called, perhaps "A strange way to die"/"Strange ways to die"? Apparently, there is this underground social group who exploit the wellknown euphoric effect of infrasound, this person was experimenting with generating specific soundtracks to harnass this effect, with intention to sell. He found that 7 Hz was a good frequency... Plasmic Physics (talk) 07:29, 31 December 2012 (UTC)

No, it definitely was "10 Bizarre ways to die." Plasmic Physics (talk) 08:02, 31 December 2012 (UTC)

Another contributing factor: he played the sound at ~160 dB. Loud enough for items to be thrown of shelves. Plasmic Physics (talk) 20:42, 31 December 2012 (UTC)

Assuming the story is true, I'm betting it was the volume rather than the frequency that did it. 160 dB involves pressure differences around 4 kPa, which makes for a rather solid full-body impact several times a second. --Carnildo (talk) 03:33, 1 January 2013 (UTC)

Humans encounter that volume often enough at audible frequencies without turning into instant soup. Plasmic Physics (talk) 05:26, 1 January 2013 (UTC)

Resonance is most effective (or dangerous, depending on your POV) on perfectly rigid bodies, with crystals being about as close as we can come. Softer materials, like people, tend to absorb any vibration before it can build up. So, while it still might be possible, it would require far more energy than the proverbial opera singer shattering a champagne glass with her voice. StuRat (talk) 08:22, 31 December 2012 (UTC)

Are you talking through your arse again StuRat? For an object to mechanically resonate, there must be a resonant frequency. For there to be a resonant frequency, there must be mass, and there must be elasticity. The degree of resonance in real objects is determined by "Q", which is the ratio of the elasticity to the degree of damping (frictional loss), and the intensity of the forcing sound or vibration. A perfectly rigid object cannot resonate. First year physics I believe. 121.221.79.244 (talk) 00:27, 2 January 2013 (UTC)

Well, in that perfectly rigid objects don't exist in the real world, I suppose how they behave is indeterminate (if they really were completely rigid, I imagine any sound at all would shatter them, as they would have no capacity to absorb, transfer, or reflect sound energy). However, highly rigid bodies resonate nicely, like crystals. StuRat (talk) 07:03, 2 January 2013 (UTC)

Despite the apparent implausibility of resonance, the cochlea nonetheless detects vibrations according to tonotopy, based primarily on the stiffness of the basilar membrane, which is much smaller than 20m - even, as our article explains, for sounds under 20 Hz. Wnt (talk) 15:38, 31 December 2012 (UTC)

The notion of it being "euphoric" seems absurd, but the search term digs out unreliable and reliable sources interesting for further examination: [7], our own article brown note, a BBC article [8], even a New Scientist article I didn't find on PubMed before [9] ... and I didn't explore more than the first page and a half.

• Anthor source, which come from Chinese National TV China Central Television. This is my rough translation from 0:17 to 1:30:

Infrasonic weapon is a weapon which transmits infrasound that frequency below 20 Hz. The acoustic wave resonant with human body, which make related organ or part of body changing shape, displacing, even fracture to make the man injured or even dead. The weapon is disguised, fast, long distance, making no pollution to the environment, and no damaging to facilities. Nonlethal weapons that every contry is making will become very important in future wars.

Expert: Nowadays, infrasonic weapon has already been used. Typical infrasonic weapon includes: infrasonic generator (most common one at present). In 1995, the US Army tested this kind of weapon in Serb soldiers in Bosnia And Herzegovina. Having been exploded for seconds, Serb soldiers were faint, vomit, and unconscious.

--維基小霸王 (talk) 15:23, 2 January 2013 (UTC)

I'm having some trouble wading through the sea of disinformation out there, but [10] seems to suggest that infrasound weapons are theoretically possible, were examined as of 1992, but (it says) were found unsatisfactory due to trouble reaching the volume needed. Skull resonance per se seems excluded by plausible-sounding claims that the skull resonates at much higher frequencies (Google says it's in here...), yet my personal experience is that particularly low-pitched, dizzying infrasound from about 1/2 hour exposure to a nearby Bobcat excavator on a few occasions causes my coronal suture to get sore, which never occurred from any other cause, so I am perversely reluctant to concede the point. Wnt (talk) 16:04, 2 January 2013 (UTC)

Properties of blood

From my understanding, blood is a shear thinning fluid. So it acts like a liquid when you apply shear to it, I.e. when flowing but when the flow rate is reduced it behaves like a solid and that this is the property of blood which helps with clotting and recovering from injuries. My question is how does this property interact with platelets etc to help with this process? Is it the fact that platelets work better in more viscous fluids? 176.27.208.210 (talk) 13:31, 30 December 2012 (UTC)

why do doctors tell women not to douche

Women have been douching for thousands of years, in fact before modern medicine, Women used to cure infections in that area with douching. Now they tell people not to douche because it may disrupt Flora, as an experiment I tried not washing my skin for a month and got numerous staph infections. There is Flora on our skin, so I don't think there theory Is correct. Although they claim the vagina is self-cleaning, They also claim the ear is self-cleaning, however it is only self-cleaning to an extent, and it should be cleaned at least periodically inside. For example, if a man were to ejaculate into the vagina without a condom in my opinion it should be douched out with plain water. This also used used to be recommended in the olden days, because the sperm (which is a living thing) that does not leak out will basically rot in there.--Mk651117 (talk) 13:35, 30 December 2012 (UTC)

The Reference desks are a forum for asking questions, not a forum for expressing your own personal opinions about things. Looie496 (talk) 14:26, 30 December 2012 (UTC)

(e/c)You've phrased your question in such a way that it appears you're asking for medical advice, which we cannot give. If you have questions about your own habits, you should consult your family doctor. I can point out that our article on douche leads to this Science News article which goes over many of the downsides associated with the practice. Your separate claim of getting multiple staph infections simply by not washing an area of your skin sounds frankly incredible. If true, you should definitely seek medical attention. Matt Deres (talk) 14:28, 30 December 2012 (UTC)

I'm not a female so I don't douche I'm not asking for medical advise. --Mk651117 (talk) 16:56, 30 December 2012 (UTC)

Well this is a reference desk, so here is a reference. Alansplodge (talk) 20:24, 30 December 2012 (UTC)

An interesting quote from that study "In a 1997 meeting of the Nonprescription Drug Advisory Committee of the Food and Drug Administration (149), Dr. Andrew Onderdonk presented data looking at women with abnormal vaginal ecology, such as women with culture-positive vaginal yeast infections (32). His group treated women with either sterile water, a vinegar and water douching solution, or a povidone-iodine solution. Twenty-four hours after treatment with the various douche solutions, the only women whose vaginal microflora returned to normal were the women who used the povidone-iodine douche. This suggested that, in women who have an abnormal vaginal ecology, perhaps due to a vaginal yeast infection, douching with povidone-iodine may be beneficial and may help to return the vaginal ecology back to normal values. "

It would appear that that study says that a vaginal yeast infection can be cured with a single application of an iodine-based douche. It seems to me like the drug companies are trying to discourage douching so they can sell expensive drugs to treat vaginal infections when douching is a cheap alternative option.--Mk651117 (talk) 20:59, 30 December 2012 (UTC)

Sorry, I have no reference aside from my experience as a married male, but "rotting sperm" is definitely not generally a problem for women who do not douche. The problem with your skin experiment is that for your whole life you HAVE disrupted the flora on your skin by washing with soap every single day. By not washing you are not immediately returning your skin to it's "natural" state all of a sudden. There are millions of people around the world who do not wash with soap every day and apart from probably being a bit smelly to our sensibilities, do not suffer from constant staph infections. Vespine (talk) 00:22, 31 December 2012 (UTC)

Just one more note, your opening premise is a logical falicy known as appeal to tradition. Vespine (talk) 00:25, 31 December 2012 (UTC)

Vespine If someone disrupts their flora on their skin by washing It with soap every day that would make them more likely to get staph infections and if they stopped washing with soap for a month It should make them less likely according to the logic doctors have regarding vaginal flora. If this person stopped washing for a month their flora should return to normal by then and and make them more resistant to staph infections if anything. The irony of this is that if you read about staph infections as well as things like folliculitis and cellulitis one of the causes is poor hygiene, which rules out the fact that flora plays much part in infections. --Jason677 (talk) 01:02, 31 December 2012 (UTC)

I don't follow your logic. Flora is a balance, besides, we're talking about internal and external which are probably quite different from each other. But in any case, if you wash your skin with soap, you are removing the bulk of the flora on your skin, so staph infections are not more likely, because the WHOLE balance is too low, when you stop washing, the "bad" bacteria have less "good" bacteria to fight and can end up winning, that's how you get an infection. The bacteria is always there, but the balance has been thrown out. You can't say a month is enough time for the balance to return, it may never return. A similar thing happens when you undergo heavy duty antibiotic treatment, such as chemo therapy, the balance in your gut is thrown out, initially ALL the bacteria are affected, but when they start to recolonise, some bacteria can grow back faster then others and that's what can cause issues. Fecal transplant can be used as a treatment by giving the patient back the colonies of bacteria they previously had to re-establish their previous balance. I'm also not sure about the logic in your last sentance, a lot of infections are caused by bacteria present in the flora, so im not sure how you can deduce that flora doesn't play much part in infections. Vespine (talk) 03:08, 31 December 2012 (UTC)

So according to that logic if woman douched every day then they would not get a infection, only if they stopped douching would it be a problem. That study you posted also said that vinegar douches do not kill the "good" flora in the vagina, only the "bad" flora, for whatever reason. --Jason677 (talk) 12:17, 31 December 2012 (UTC)

No, according to that logic, washing the unbroken skin on your arms can not be compared to washing the mucous membrane inside a vagina. Mucous membranes are specifically susceptable to infections if the mucous which normally protects it is disrupted, for example by washing it off. To be honest, I'm actually not sure what you're trying to argue. What point are you trying to make? It doesn't sound like you actually know what you're talking about, I'm certainly no expert either, so what's your point? Do you dispute why doctors recommend not douching? It seems like there is more then enough references and links in our article to present a pretty good argument. Vespine (talk) 02:37, 2 January 2013 (UTC)

Add indicator lamp to heater

I have a question about electrical circuits. I have an electrical heater at home, powered by mains electricity (220V AC), which I use when changing my baby's diapers so she doesn't get too cold. Many models have a feature where they automatically turn off after a certain period of time (eg 10 minutes), but my heater does not have this feature. I only turn it on to change diapers, but occasionally I forget to turn it off, which is annoying as it uses a fair amount of power.

I would therefore like to add some kind of indicator light/lamp to remind me that the heater is switched on. Is there anything you can suggest which would accomplish this? I thought about wiring a light in series with the heater, but I only have 220V lamps, which wouldn't work in series with another 220V device. Any tips would be appreciated! — QuantumEleven 15:03, 30 December 2012 (UTC)

If you need to ask a question this basic, you are obviously not qualified to work on mains voltage cicuits. Therfore I suggest you take a different tack, which is simpler anyway. Purchase an multi-output extension lead. Typicall units have 4 outlets on a small box about 40 x 150 x 30 mm dependiong on style and country. These incorporate a neon light that indicates the power is on. Plug the extension lead/board into the wall outlet and teh heater into the lead/board. Get into the habit of switching on/off at the wall, and then the light will warn you that you have the heater powwered up. Wickwack 124.182.143.91 (talk) 16:41, 30 December 2012 (UTC)

Neon light ? I've never seen one of those on a power strip. They typically have an LED light (often in the power switch): [11], although older ones might have an incandescent light. If you don't have a wall switch on your outlet, be sure to get a power strip with a power switch on it, then turn the heater on and off there (I use my foot, since it's on the floor). In addition to a switch and indicator light, some also act as a surge protector, but that's more for protecting delicate electronic equipment, so you could skip that feature here, to save some money. StuRat (talk) 21:31, 30 December 2012 (UTC)

LEDs in a power strip??? StuRat, do you have any idea of the nonsense you talk? The Belkin unit you linked to has a neon light in the switch. In most countries, a wall outlet without a switch would be illegal, as the ability to switch off an appliance broken or on fire is an important safety requirement. Keit 120.145.54.24 (talk) 02:44, 31 December 2012 (UTC)

The Belkin unit doesn't say whether it's an LED or neon light. StuRat (talk) 04:06, 1 January 2013 (UTC)

LED is correct. Not neon. I can only imagine the waste of energy. And wall sockets almost never have switches in the U.S. Where are they required? Rmhermen (talk) 03:34, 31 December 2012 (UTC)

? you guys must be young; i'm old enough that my stock of power strips, switches and GFCs with pilot lights, etc. antedate the wide availability of LEDs and rely on the once ubiquitous NE2 bulb, a handy item with a current draw of a few milliamps whose availability at every Radio Shack I miss, due to a lifelong habit of wiring them (with a current-limiting resistor) across the after-the-switch power leads of all appliances such as the OP's heater which did not come with an indicator. Of course, that parallels the general switch from things relying on 110 volts (in America) to ones that run on batteries.  :::Gzuckier (talk) 04:39, 31 December 2012 (UTC)

Don't worry, those NE-2's are still readily available, and will be for years to come. For things that run on AC without any internal conversion to DC, and a myriad of applications that use the special characteristics of a gas discharge, there's nothing better than a small neon tube - cheap, simple, and yes, more energy efficient than a LED. Not as long life as a LED though. Just about every electronics hobbyist shop and trade supplier has them. We had RadioShack/Tandy in Australia for a while. I don't miss them. They stocked a small weird combination of odd bits and pieces at inflated prices. Firms like Dick Smith, Altronics, etc left them for dead. Keit 120.145.54.24 (talk) 05:01, 31 December 2012 (UTC)

Keit, are you going to admit you were once again wrong by saying power strips never come with LED indicator lights ? And how about not accusing me of talking nonsense (when it's you who doesn't seem to know squat about electronics, at least outside of your home country). StuRat (talk) 06:10, 31 December 2012 (UTC)

StuRat, put a sock in it. Not only am I a fully qualified professional electrical/electronic engineer, I have over 50 years experience, mostly in design, senior, and consultancy roles, and while I am not familiar with the US National Electrical Code (as it applies only in the USA) I am fully familiar with practices in countries whose standards are based on European standards, which is most countries in the World, Japan and the USA excepted. And I do know darn well what's in power boards and the like, and its never LEDs for the reasons given by Gzuckier and myself. Stop trying to defend the indefensible. Think before you post, check your facts, and you won't be picked on by me or anyone else (they do squawk now and then don't they?), because you won't be posting such bulldust. Keit 121.215.132.62 (talk) 10:41, 31 December 2012 (UTC)

Keit, WTF is wrong with you ? A simple Google search for "power strip with LED indicator" gives millions of results: [12] (that's more than "power strip with neon indicator"). Then there's our own article on them: Power_strip#Indication. You are the one who pulls this crap out of you ass and passes it off as true. You apparently know nothing about electronics outside of your country, so are utterly incompetent to "correct" anybody else. StuRat (talk) 03:54, 1 January 2013 (UTC)

There's nothing in the Wiki article that establishes that LEDs are used, though there is a single sentence mentioning LEDs. It wouldn't be the first time that a Wiki article has it wrong.

Only a complete idiot would believe that just because googling "power+strip+with+led+indicator+light" returns "about 1,610,000 results" then that means 1,610,000 pages describing power strips with LED indicator lights. What it returns is pages with those words in them somewhere, not necessarily in that sequence. When I clicked on your google link, the 1st page listed was the Wikipedia article. The second page, an Answers.com contribution, has a discussion on ground fault indicators, and a refernce to power strips and a separate unrelated link to LEDs as indicators in general, not related to power strips. The 3rd page, a question and answer page, has LEDs clearly associated with power strips, and also clearly indicates the author of the questions and answers has confused neons for LEDs as he describes a common fault that occurs with NE-2 -style neons when they age and never occurs with LEDs. The 4th page is an illustration of a range of electric products, including power strips with no mention of LEDs in them, and another quite different product with a dimmable LED viewing light in it. The 5th page, MadeInChina.com, is a catalog of a range of products, including power strips (no LEDs) and LED strips for room lighting - quite a different thing.

Get the picture now StuRat? I hope you don't need a comment on all 1,620,000 pages. Perhaps you are like some non-technical folk who think that anything that glows, is small, and is electric must be a LED. Quite often they are not. You even get coloured plastic lenses on Asian electronic equipment that looks just like a typical red, orange, or green led, but behind it is an NE-2 -style neon or even an incandescent pea lamp (as in some Japanese hifi/stereo equipment). But you will make a much better contribution to Ref Desk if you think before you post, and check your facts, rather than abuse anyone who says you are wrong. I know from your old posts you are an intelligent chap - you can do better. Your posts in recent times are getting worse - is there a reason? Keit 121.215.48.51 (talk) 09:54, 1 January 2013 (UTC)

I can't tell which links you refer to by the order of the Google return, since Google seems to return a different list for different people (I get 1,730,000 Ghits, not 1,610,000). I will provide the actual links. Here's the 2nd link returned to me: [13] (the first being Wikipedia). That seems to be talking about actual LED indicator lights on power strips with surge protectors, and they seem to be qualified individuals, being an electrical supply company. A bit further down the page, I find this link, which is similarly a company selling power strips, which claims they have LED indicator lights: [14]. This next link talks about why some power strips have flickering indicator lights and others are solid. According to this site, it's the neon ones which tend to flicker, and the LED ones don't: [15]. I could go on, but you get the point, many web sites talk about LED lights in power strips/surge protectors. Yes, Google gives lots of false returns, but the relative number of returns for LED being more than neon tells us something, that more web sites talk about LED indicator lights on power strips than neon indicators. Given this level of evidence, it's not reasonable for you to continue to insist that power strips with LED indicator lights do not exist. Even though I had not personally seen a power strip with a neon indicator light, I'm perfectly willing to accept that they exist, based on the Google returns, and you should be reasonable enough to do the same. You need to get over this mode of insisting that anything you haven't personally seen or heard of can't possibly exist.StuRat (talk) 03:48, 2 January 2013 (UTC)

I have seen perhaps one outlet per room controlled by a switch by the door, and that outlet is typically used for a lamp. Controlling all outlets with switches would inevitably lead to having clocks switched off, etc. StuRat (talk) 03:40, 31 December 2012 (UTC)

In the UK, every modern outlet has an individual switch (it's about 50 years since unswitched outlets were common). The exception is clock outlets which are fused but unswitched. These are now rare because of cheaper battery clocks. Dbfirs 11:12, 31 December 2012 (UTC)

I see. Do you have a switch by every outlet, or just a giant switch bank by the door ? If so, I sure hope they are labelled. Something else to note is that most rooms in the US have an overhead light fixture, also controlled by a switch near the door(s), so there is no outlet associated with that switch. StuRat (talk) 18:17, 2 January 2013 (UTC)

Yes, every outlet has a switch incorporated in the outlet, not separate. A double outlet has two separate switches. Unswitched outlets have not been normally available for about forty years, though they can occasionally be found in older houses that have not been rewired. The reasoning is presumably that the switches on some appliances can become faulty, so the outlet switch is an extra safety feature. Also, the higher voltage (typically 240v here in the UK) means that there is more risk in plugging and unplugging when the plug is "live" (though two other plastic safety features have been added in the last 60 years). Lighting fixtures are switched exactly as in the USA. Dbfirs 19:15, 2 January 2013 (UTC)

Are your outlets higher than in the US ? Here they are like a foot off the floor, typically (except in the kitchen and bathrooms), which would mean a lot of bending to turn switches on and off down there. StuRat (talk) 23:42, 2 January 2013 (UTC)

Some are still at skirting-board level, but the modern standard in new houses is to place them about 4 feet high to give easy access for wheelchair users. Dbfirs 08:51, 3 January 2013 (UTC)

Since I have a bad back, and have difficulty bending down to plug and unplug things, that sounds great to me. Can you pick me up at the airport ? I'll be on the next flight. :-) StuRat (talk) 19:18, 3 January 2013 (UTC)

You'd better not rush to book your flight, Stu, because the electrics in my house are at least fifty years old and mainly follow the American (and older British) practice of outlets at low level. The only ones at a convenient height are those that I've added. A cheap and easy solution is to mount a short cheap extension onto the wall at a convenient height and plug it in to the low-level outlet. Dbfirs 09:56, 5 January 2013 (UTC)

My current house has multiple outlets per room controlled by wall switches, in lieu of ceiling light fixtures. And yes, it is incredibly annoying; I have mostly put those little covers over them that prevent me from absentmindedly switching them off. Gzuckier (talk) 04:39, 31 December 2012 (UTC)

Better still, get a timer. You see those ones that will turn lights on and off at specific times of day. If you set that machine to turn on and off for just one hour in every 24 hours (say, on at midnight, off at 1am) - then, when you need to use the heater, rotate the dial to "midnight" - until it just turns on - then if you forget, the heater will turn it off again, automatically one hour later. Of course if you don't use the heater then it'll turn on again 24 hours later...but if it's a changing table, it's unlikely that you won't use it at least that often! By all means use a extension cord with a neon indicator too...but this would be a good back-stop. Since heaters use a lot of current, make sure that both extension cord and timer can handle that amount. SteveBaker (talk) 17:29, 30 December 2012 (UTC)

There's a couple of countdown or boost timers which you set and timeout and they're fairly cheap, but in fact the 24 hour timers tend to be even cheaper and all you need do is set only the switch off time and not the switch on time and you've got a good adjustable countdown with them. Dmcq (talk) 19:19, 30 December 2012 (UTC)

You might have trouble finding an appliance timer rated for the wattage used by a space heater. In the US, they typically draw 1500 watts, and those small outlet timers can't handle that. StuRat (talk) 21:27, 30 December 2012 (UTC)

The OP said their voltage is 220 V. Appliance timers rated for either 8 A or 10 A are quite common in 220 V and 240 V countries - that corresponds to 1760 to 2200 W. Keit 120.145.54.24 (talk) 02:44, 31 December 2012 (UTC)

I used to have space heaters hooked up to timers. One timer that I have left over says it is rated to 1700W (125V, US configuration). I don't remember where I bought it, but it wasn't hard to find.--Wikimedes (talk) 12:36, 31 December 2012 (UTC)

The weird thing is, in the U.S. I never even heard of the idea of having switches on outlet plates as a safety measure (outside of ground fault outlets, that is). I never questioned the idea that the "switch" is to pull out the plug. What am I missing? Wnt (talk) 19:30, 31 December 2012 (UTC)

The plug and socket are not designed to be a switch, so you should not routinely switch off by pulling out the plug (or switch on by pushing the plug in. Appliances should always be switched off using the on/off switch provided on the appliance if provided, then switch off at the wall outlet (termed a General Purpose Outlet [GPO] in official standards.), then pull out the plug if putting the appliance away. Switches are designed to give a clean sudden break so that arcing is minimised. However, in an emergency (eg appliance on fire) I would be quite happy to pull out the plug if there's no other option.

Regarding the safety requirement to have a switch at every wall outlet, one must remember that American electrical safety standards are lower than European and other standards (the concept of third pin earthing is comparitively new to USA - the rest of us have had it >100 years). That is not a criticism of the USA because a) it's a lot harder to kill yourself with 110 V than it is with 220 V (albiet still quite possible), and b) the USA was the first country to implement widespread commercial electricity distribution. Doubling the voltage makes switch arcing and wear a lot worse too. Other countries came later and were able to benefit from experience while the USA was stuck with early standards. Once standards are set it is very expensive to change. We saw the same thing in reverse with analog television - Britain was first with 405 lines and AM sound in 1938 - a significant achivement back then, but not really adequate in sound quality nor picture detail. The USA was next, starting TV just after WW2 with 525 lines and FM sound - a significant improvement compared to the British system. Europe and Australia was next in the late 1950's with 625 lines and FM sound and a few minor technical improvements. Nobody would think that made Australian TV engineers smarter than American or British TV engineers - they just came later and drew on American experience. A strong case can be made for 220/230/240 V rather than 110/115 V, especially with countries with lower density towns, but that is another subject. Keit 124.178.141.171 (talk) 00:59, 1 January 2013 (UTC)

The problem with that explanation is that I can't imagine why we would possibly want to switch to a 220 volt standard, even if it were totally free and easy (and if not doing so, why we would want these extra switches). Why the heck would I want a 220V television cable, a 220V floor lamp, a 220V anything, except the appliances that are already 220V with 220V outlets in the U.S. right now (and I am skeptical those are worth the trouble). I've been to some places with 220V and a B&B with a frayed connection to the lamp or a 220V wire running, for some reason inexplicable to man, to the shower head, is a questionable enterprise to my way of thinking...

Actually, come to think of it, if I were starting a new standard I think it would be to run everything on about 5 volts DC, so computers and cell phones and such wouldn't need power supplies. I imagine LED light bulbs could work well with it. I don't know about rigging an electric oven ... but hey, gas is better anyway. :) Wnt (talk) 05:38, 1 January 2013 (UTC)

The pros and cons for various voltages have been discussed repreatedly on Ref Desk, including quite recently. The fact is, each type of appliance or load has its own best or ideal voltage. 5V could never be succesfull, as when voltage is lowered, current must increase to conpensate. A 1 kW heater on 5 V would draw 200 Amps - the cables, plugs, and switches for 200 A would be immense. 110/115 V was not a bad choice for USA as USA has a high population density, with most folk living on small plots of land or no land of their own at all, as in blocks of flats or high rise flats. That in turn makes for short intervals between transformers, so the cost of distribution at final voltage is not too high. In Australia, 240 V was a good choice becasue we have an overall population density only a tenth of that of the USA (and the contrast was even greater when standards were set). We mostly have lived on large land plots, so there is a large distance between transformers. So the cost of final voltage distribution is relatively high in Australia, and the cost falls increased voltage, because the current is less. Keit — Preceding unsigned comment added by 121.215.48.51 (talk) 09:06, 1 January 2013 (UTC)

Why do some carbon compounds burn and others not?

Why don't granite, diamonds, limestone CO2 burn? But, methane and other do? OsmanRF34 (talk) 16:30, 30 December 2012 (UTC)

A chemical will only burn if it is in an environment that allows an exothermic reaction to take place. Looie496 (talk) 16:37, 30 December 2012 (UTC)

And why is an ignited match an environment that allows an exothermic reaction to take place in the case of paper, but not in the case of granite? OsmanRF34 (talk) 16:50, 30 December 2012 (UTC)

It's down to how tightly the carbon is bonded to the other elements in the compound (and to itself). If you burn some methane (CH4 - carbon and hydrogen) in oxygen, you get CO2 and H2O - carbon dioxide and water. The oxygen in the CO2 and H2O is bound more tightly to the Carbon and Hydrogen than those the carbon and hydrogen were bonded to each other in the methane. Put in terms of energy - the amount of energy it took to pull the methane molecules apart was far less than the amount that was released when the carbon and hydrogen bonded with the oxygen - so that reaction happens very easily. The reverse reaction would require massive energy input - lots of energy to pull the carbon and hydrogen away from the oxygen and very little (if any) regained if the carbon and hydrogen could somehow be turned back into methane. SteveBaker (talk) 17:23, 30 December 2012 (UTC)

Your premise is wrong. Diamond#history talks explicitly about combustion of diamond. --ColinFine (talk) 17:30, 30 December 2012 (UTC)

In fact a demonstration of burning a diamond in oxygen was shown in the Royal Institution Christmas Lectures only the other day. You can see it at http://www.bbc.co.uk/programmes/b01pp6bq but you may only be able to watch it from a UK ip adress. Richerman (talk) 18:02, 30 December 2012 (UTC)

It requires a LOT of heat though - the energy input to break apart those strong lattice bonds in order that combustion can occur. You can't just wave a match over it and expect it to catch fire. SteveBaker (talk) 18:26, 30 December 2012 (UTC)

Yes, he used a blowtorch in the RI demonstration. Richerman (talk) 19:07, 30 December 2012 (UTC)

Sorry, I just watched it again to check. He used a hydrogen flame light it and then after a few seconds he removed the flame and the diamond kept glowing as the carbon carried on combining with the oxygen to form CO2. Richerman (talk) 19:25, 30 December 2012 (UTC)

To be clear, carbon dioxide (CO2) is the product of burning, so it doesn't itself burn (it's the most stable combination of carbon and oxygen). Limestone is made up of CO2 which has dissolved in water and reacted reversibly to form carbonic acid (H2O+CO2=H2CO3) and then given up a hydronium (proton) because of alkaline conditions to yield bicarbonate HCO3-, which interacts with calcium ion to produce limestone (CaCO3). Since limestone is made from CO2 interacting by further (non-burning) means that don't require energy in, it doesn't produce energy out by burning. Lastly granite doesn't contain any carbon that I'm aware of. Wnt (talk) 19:21, 30 December 2012 (UTC)

Carbon dioxide can burn (or at least can provide an environment for something to burn). Set light to magnesium ribbon in a CO₂ atmosphere and the magnesium will burn quite happily, stripping the O from the CO₂ and generating a lot of soot. By the way that's probably graphite rather than granite. Tonywalton ^Talk 00:26, 31 December 2012 (UTC)

The OP may be confusing granite with graphite. --NorwegianBlue ^talk 19:54, 30 December 2012 (UTC)

Ah, of course. And that's interesting because graphite is actually used as a refractory. Looking into this, there seems to be some sophistication involved - the graphite might be treated with phosphates, or it might be intended to oxidize before silicon carbide components ... I don't presently really understand the industrial uses. "Graphite does not burn or support combustion. If ground to sub-micron sizes, graphite may ignite spontaneously in air." [16] Hmmm.... Wnt (talk) 00:16, 31 December 2012 (UTC)

Strictly speaking graphite does not burn; no solid does. What happens is that the heat (either initial applied heat, or heat of combustion) causes the graphite (or other substance) to sublimate to gasseous carbon, which burns very readily. It takes a lot of heat to sublimate graphite, you it is difficult to get started. In complex substances, ege wood, coal, pyrolisation occurs - the local heat causes the wood, coal, etc to break down into gasseous components that burn, and solid components (the ash) that will not.

The fact that graphite will burn if the temperature is high enough to sublimate it is why graphite moderated nuclear reactors are inherently dangerous, and there have been some serious accidents in England and elsewhere. If the control rods get stuck, up she goes. Keit 120.145.54.24 (talk) 02:55, 31 December 2012 (UTC)

Actually, the reason why graphite-moderated reactors are dangerous is because of their positive void coefficient -- which essentially means that when the reactor temperature increases, the nuclear reaction self-accelerates, possibly leading to a dangerous runaway reaction, (although we Americans have operated just such a reactor at Hanford Site for decades without any serious trouble). 24.23.196.85 (talk) 06:01, 31 December 2012 (UTC)

That may be so, but it's more complicated than that. And I do mean the graphite can catch fire and has done so. Windscale UK 1957 is an example. A graphite moderated reactor at Windscale had an unexpected temperature increase with control rods fully inserted. The reason was not understood at the time, due to a defective design, and the technicans took the wrong action, ultimately trying to correct it with emergency forced air cooling thru the graphite channels. Locallised very high temperatures had set uranium on fire - that and the oxygen forced in set the graphite alight. The positive reaction coefficient was understood at the time and had little or nothing to nothing to do with it. It is thought that failure to fully aneal the graphite, as required regularly in graphite moderated reactors, was the initial cause. When graphite self-aneals, heat is liberated. Graphite moderated reactors are cheap and simple to construct, but are full of tricks in operation. Keit 121.215.132.62 (talk) 10:27, 31 December 2012 (UTC)

I do not deny the foregoing -- my point is that the biggest operating hazard in a graphite reactor is due to the positive void coefficient. 24.23.196.85 (talk) 04:19, 1 January 2013 (UTC)

Article on energy effects of direct sunlight?

Do we have an article that discusses the effect caused by direct sunlight on a surface? I'm looking for something to describe what's going on in this picture, where sunlight has melted all the snow off the roof except for the area that's shaded by one of the chimneys. Shade doesn't help enough, its parent Category:Shading is actually a graphics thing, and Insolation may be useful, but it appears to be on a global or continental scale instead of something small enough to be measured in feet or metres. Nyttend (talk) 18:01, 30 December 2012 (UTC)

How about Solar gain? Richerman (talk) 18:05, 30 December 2012 (UTC)

Thank you. I've added the photo to the article; is the caption accurate and relevant? "Solar gain is illustrated by the snow on the roof of this house: sunlight has melted all of the snow, except for the area that is shaded by the chimney to the right". Nyttend (talk) 18:18, 30 December 2012 (UTC)

Sounds about right to me but I'm no expert. Richerman (talk) 19:00, 30 December 2012 (UTC)

December 31

Light illumination?

Why does red light produce less illumination than blue or green light? NealCruco (talk) 01:01, 31 December 2012 (UTC)

Wikipedia doesn't have a good non-technical article on it (the closest I could find was Luminosity function), but the human eye is most sensitive to green light, and more sensitive to red light than to blue light, but more sensitive to variations in blue than in red, giving the appearance of greater sensitivity to blue. --Carnildo (talk) 01:34, 31 December 2012 (UTC)

The technical term (and the main article) is photometry, the field of study that deals with human perception of photons and illumination. Strictly speaking, a red light source and a blue light source and a white light source can all shine with the same luminous intensity, and yet still be perceived at different apparent brightnesses when viewed by the human eyeball (and the brain, which is usually attached, that processes the vision stimuli). This is because your eyeball is not the standard eyeball that was used to define luminous intensity. And of course, if you read and understand luminous intensity, it will be obvious why a blue, red, and white light-source might produce the same number of watts of visible light, yet vary significantly in perceived brightness: because brightness is perceived in a wavelength-dependent way by the human visual system. Everything from the photochemical response of retina cells, to the brain's psychological interpretation of color signal, is wavelength-dependent, and this ensemble must be approximated by one of the many common luminosity functions, or by one you create for yourself for your own purposes. Our photometry article elaborates on the subtleties of measuring "brightness" and related quantities; depending on your application, you may want to measure incident energy, or incident photon-count, or perceived luminous intensity, or some other specific quality/quantity. Many standard units and methodologies exist that cover most common use-cases. Compare radiometry, which avoids the messy bits of perception and instead deals exclusively with physical quantities like number od total incident photons, or watts. Nimur (talk) 04:11, 31 December 2012 (UTC)

Also, Purkinje effect may be relevant. Gzuckier (talk) 04:55, 31 December 2012 (UTC)

And any number of other contextual effects applied by various other modules in the visual system, as in edge and shape detection. Here are some optical illusions illustrating just a few of these forms of post-optic nerve processing of the raw luminosity/wavelength information provided by the eye: 1, 2, 3, 4, 5. Snow (talk) 06:30, 31 December 2012 (UTC)

Eating meat from a venom-killed animal

Would it be safe to eat the meat of a creature that has been killed by the venom of another animal, say a chicken bitten by a rattlesnake or a fish stung to death by jellyfish? Or would that depend on the individual animals involved? 69.111.189.155 (talk) 02:06, 31 December 2012 (UTC)

We can't answer medical questions here. Hot Stop (Talk) 02:10, 31 December 2012 (UTC)

We can't give medical advice, but hopefully no one is being advised here. Our article venomous snake says something I didn't know: "It is, for example, harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. The two exceptions are: the Rhabdophis keelback snakes secrete poison from glands they get from the poisonous toads they consume, and similarly, certain garter snakes from Oregon retain toxins in their livers from the newts they eat." In general, every toxin is different, so it is impossible to make any general statement with accuracy - I don't know if those are the only two exceptions. Wnt (talk) 02:19, 31 December 2012 (UTC)

Just to clarify, I didn't intend for this to be medical advice. I was just curious. Thanks for the responses anyway! 69.111.189.155 (talk) 03:50, 31 December 2012 (UTC)

Our article snakebite points to a paper "Riggs BS, Smilkstein MJ, Kulig KW, et al. Rattlesnake envenomation with massive oropharyngeal edema following incision and suction (Abstract). Presented at the AACT/AAPCC/ABMT/CAPCC Annual Scientific Meeting, Vancouver, Canada, September 27 October 2, 1987." which (the article claims) indicates that people have gotten poisoned by sucking snake venom from other people's wounds...so I suppose it's not impossible for you to get into trouble by eating venom-killed meat. But the size of the dose from eating a pound or so of the meat from an animal seems like it would be rather small in a 100lb+ human provided you didn't eat the part of the animal close to the actual bite site. Tough question though...I wouldn't want to bet my life on anyone's answer here! SteveBaker (talk) 05:01, 31 December 2012 (UTC)

I tracked that abstract down a bit further out of curiosity: "Riggs et al (1987) reported the case of a 29 year old man with no prior history of snakebite, who was bitten on the left index finger by a rattlesnake. The patient had performed incision and oral suction before seeking medical attention. He also had recent dental surgery and gingival irritation and mucosal breaks. Mild edema from the bite site to the wrist and a mild coagulopathy developed. The most striking feature was massive oropharyngeal edema with dyspnea, wheezing, and inability to speak, which occurred before any antivenin was administered. The massive oropharyngeal swelling may have been due to absorption of venom through the injured gingival mucosa and brings the safety of incision and oral suction into question." (found at [17]) I note that this was the same patient who had otherwise been bitten, which means there could be some pattern of interaction between the suctioned venom and the injected venom components, so I don't know for sure this extends to any random sucker. Wnt (talk) 18:46, 31 December 2012 (UTC)

Notice that people have been using arrow poison for thousands of years. Icek (talk) 23:15, 31 December 2012 (UTC)

Very many natural venoms are complex molecules with high molecular weight. These usually break down into harmless compounds both under the influence of heat and by contact with stomach acid. As always, there are exceptions (as e.g. if the venom enters the bloodstream via a would in the oral cavity), so caveat emptor. --Stephan Schulz (talk) 12:01, 2 January 2013 (UTC)

How can i Make a Ligand substance be SELECTIVE on specific receptor areas ?

Let's say i create a new general material which inhibits all types of Gaba receptors, but i want it to be selective to a very particular area of the brain. in other words, while the substance can influence all brain areas with Gaba R, I want it to focus on a particular one.

what are the princilpals of making a particular molecule Selective? what things should i take for granted? when constructing this molecule.

THIS IS NOT HOMEWORK !, i ask because i want to know about the principles. i understand that lately, some new info was discovered about this. thanks. 109.65.115.101 (talk) 06:20, 31 December 2012 (UTC)

Well, I suppose you could make something which reacts more with grey matter or white matter, or perhaps with areas that are more active (use more glucose), but I don't know how you could make it only react with, say, areas storing memories of cats. There has been some study on applying electromagnetic fields to the brain, and perhaps you could make something that would only be activated in the presence of a strong electromagnetic field, and thus you could control which regions of the brain are affected, by altering the field strength and shape around the head. StuRat (talk) 07:10, 31 December 2012 (UTC)

if i understand you correctly what you say is: after a ligand is given, we could "Navigate it" to a specific brain regions by external methods? — Preceding unsigned comment added by 109.67.131.95 (talk) 09:57, 31 December 2012 (UTC)

Either that, or activate it in a particular region, so it would float inertly through the rest of the brain. StuRat (talk) 03:44, 1 January 2013 (UTC)

With regards to GABA receptors, which are located on the cell membrane, there is no (current) way of making a non-selective ligand selective for a brain region. If it can pass the blood-brain barrier, then it will diffuse amongst the entire brain. There are ways of making a drug selective to a brain region if that region expresses selectively expresses something. For example 6-hydroxydopamine given systemically will selectively kill midbrain dopaminergic neurons and noradrenergic neurons, because it is taken up by the dopamine transporter and noradrenaline transporter, so only neurons expressing these transporters will uptake it. With regards to GABA ligands, there are different expressions of GABA receptor subunits in different brain regions, so one can design a ligand which will only bind to GABA receptors which contain a specific subunit (but this ligand will still diffuse amongst the entire brain). There's currently a large amount of research going into this in the hope of developing anxiolytics without amnesic effects, etc. --Markr4 (talk) 11:03, 31 December 2012 (UTC)

Hey Mark, and many many thanks for kindness. about the anciolytics you mentioned. are all amnesic?, and, does this amnesia caused by Necrosis?

thanks ! — Preceding unsigned comment added by 109.67.131.95 (talk) 12:58, 31 December 2012 (UTC)

Well the anxiolytics I was referring to were benzodiazepines, each which have their own unique attributes (i.e. some are more amnesic than others, probably due to GABA receptor subunit specificity). But benzodiazepine-induced amnesia is almost certainly not caused by necrosis.. Rather it is caused by their enhancement of GABA-mediated inhibition of long-term potentiation, probably in the hippocampus. Here is a link to a free-to-read paper which talks about the role of the GABA-A alpha-4 subunit in amnesia (although they used isoflurane for proof of concept). Here is a link to a review paper discussing the role of all the GABA-A receptor subunits. --Markr4 (talk) 19:34, 31 December 2012 (UTC)

Look up "the GABA receptor" and you will see that in fact, there are many different kinds of GABA receptors. Because there are different kinds, it is possible to have many different kinds of GABA agonists which affect different channels and have different effects. Ethanol, GHB, barbiturates and Quaaludes are not precisely the same, for example. The same is true for most other receptors - for example, you can design cannabinoid drugs to do anything from suppressing appetite to treating inflammatory bowel disease. Wnt (talk) 15:01, 31 December 2012 (UTC)

To start to answer your question (to control where the drug is activated independently of structure) see [18] for an idea and [19] for some results (though I think that example is far too crude to possibly work for your application, and it may not even count as a proof of concept). Wnt (talk) 15:11, 31 December 2012 (UTC)

• Making drugs that are more selective is the dream of pharmacology. Currently the only way of doing it is to try making small changes in the structure of a molecule and hope you get lucky. Lots of people have been trying to develop a principled approach to the problem, but so far it hasn't panned out very well. Looie496 (talk) 15:27, 31 December 2012 (UTC)

• OK, so this is not really an answer to the question, but this could be done in an experimental setting with transgenic animals. As long as you have a protein-based inhibitor that could be expressed in mammalian cells (not sure if one exists off the top of my head), use of a region or cell-type specific promoter will allow you to do this. Slight off-topic, I admit. Fgf10 (talk) 17:13, 31 December 2012 (UTC)

Not at all off-topic. Gene therapy may have hit some snags in initial trials, but there is no reason to think it will not one day be as simple to use as a chemical pill is today, and as you say, it could be exquisitely fine-tuned. Wnt (talk) 18:39, 31 December 2012 (UTC)

I didn't even think of the gene-therapy angle, but that's a good call. (I spend a big chunk of my professional life working with transgenic animals, so it's always my first thought). There have been efforts to use specific promoters to enhance gene therapy already. Fgf10 (talk) 19:05, 31 December 2012 (UTC)

• Probably it is possible to archive using optical control of protein activities (Google: controlling protein activities with light). And then use technics from optogenetics to activate protein only in selected regions of the brain. Currently most research are done around intracellular activities of proteins, but technically it should be possible to create one that would bind membrane receptor only in a presence of light. TMMForever (talk) 19:34, 31 December 2012 (UTC)

Specific capacity... What the heck is it?

Here is the quote:

The anode shows also superior stability over 600 cycles and exhibits high specific energy (200 Wh/kg) delivered at a specific power of 30 kW/kg. The TiO2 anode in a full Li-ion cell with a LiNi0.5Mn1.5O4 cathode operates at 2.8 V and demonstrates the highest (310 mA h/g) reversible specific capacity reported to date.

http://pubs.acs.org/doi/abs/10.1021/nn900150y?journalCode=ancac3&quickLinkVolume=3&quickLinkPage=907&volume=3

I could understand "specific energy" and "specific power". Both numbers(200 Wh/kg & 30 kW/kg) do make sense. But "specific capacity"? Look, 310 mA h/g at 2.8v, if we convert to wh/kg, that would be 868 Wh/kg. And we are talking about QUOTE:"full Li-ion cell". But they just claimed anode got specific energy of 200 Wh/kg. So only way to wrap my head around is to assume that cathode have way higher specific energy then 868 Wh/kg achieved for full cell. Which is not realistic.

Or may be "specific capacity" means something very different then "specific energy"? TMMForever (talk) 11:45, 31 December 2012 (UTC)

The given units mA h/g would seem to have the dimensions of charge/mass, which I suppose might be called specific charge. My guess therefore (and it is a guess) was that the sentence was intended to read specific charge capacity. --ColinFine (talk)

Yeah by itself 310 mA h/g have detentions of current*time/mass, but if we take into account mentioned 2.8 V we actually should get specific energy. IMHO. Please also take a look at the link to abstract, they have a nice graph that try to explain characteristics of the cells in question, with one axis representing "specific capacity". But I admit, I actually clueless as to what specific charge capacity represents... TMMForever (talk) 12:26, 31 December 2012 (UTC)

Here is an explanation of what that represents [20]. Mikenorton (talk) 12:38, 31 December 2012 (UTC)

Perfect, thank you! TMMForever (talk) 18:23, 31 December 2012 (UTC)

And still talking about specific (charge) capacity, to understand the beast, could someone estimate specific energy of the cell in question? Provided the above mentioned sentence("The TiO2 anode in a full Li-ion cell with a LiNi0.5Mn1.5O4 cathode operates at 2.8 V and demonstrates the highest (310 mA h/g) reversible specific capacity reported to date.") and this graph: http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-4/jp210793u/production/images/medium/jp-2011-10793u_0006.gif

Should I just use 2.8V mentioned in sentence to calculate specific energy? Or should I take discharge voltage from the graph, looks like 1.4V at 310 mA h/g and use that to estimate Wh/kg? Or some other strategy? TMMForever (talk) 18:23, 31 December 2012 (UTC)

Scientific explanation for ESP (Extrasensory perception)

I have since I was a child been having experiences which would be called ESP (Extrasensory perception), even recently I have had some experiences that I cannot explain such as I had had a horrible feeling that if I went out that day something bad was going to happen to me, well I had to go out, and when I was reversing in my driveway My mirror hit a garbage can that someone had put in my path and the mirror exploded showering glass all over me and the inside of my car through my open window. I also predicted Michael Jackson's death three months before it happened, I just had this strong feeling that he was going to die soon and he did. The same thing happened to my dog. Although she was 12, she was in reasonably good health. I had this strong feeling that she was going to die soon and she died a week later. I am atheist and I don't believe in a afterlife or spirit world so I have no real way to reconcile these experiences with science, which is what I believe in. Has science ever been able to explain things like ESP.--Jason677 (talk) 14:53, 31 December 2012 (UTC)

This could be confirmation bias - how many times have you had these feelings but it did not turn out to be a correct prediction so you have forgotten about it?--Gilderien Chat|List of good deeds 15:22, 31 December 2012 (UTC)

(ec)What you describe is not actually ESP but precognition. Most people here will tell you it is bunk, confirmation bias in your recall of events. If you don't believe that, you may believe that it is very dangerous, and has been warned against by several religions. I hesitate to explain further, because the more one understands it the more dangerous it is... Note that our article on the Diocletian persecution reports that it started when some believers making the sign of the cross were able to block the perceptions of the Emperor's haruspices, which suggests a remedy. Wnt (talk) 15:31, 31 December 2012 (UTC)

Perhaps the postulated parent universe's virtual machine(s) are getting hacked. ;) --Modocc (talk) 17:05, 31 December 2012 (UTC)

It could have been a self fullfilling prophesy too. If he/she was spending too much time worrying about unknown dangers his/her attention to hazards in his/her immediate path could well have been compromised. Wickwack 124.178.61.38 (talk) 16:07, 31 December 2012 (UTC)

WHAAOE! We have an article on Self-fulfilling prophecy too... How about that for foresight! -Modocc (talk) 16:28, 31 December 2012 (UTC)

Here is a excerpt from Richard Feynman's book, Surely you're joking, Mr. Feynman:

"I remembered the time I was in my fraternity house at MIT when the idea came into my head completely out of the blue that my grandmother was dead. Right after that there was a telephone call, just like that. It was for Pete Bernays--my grandmother wasn't dead. So I remembered that, in case somebody told me a story that ended the other way."

I have my own story. When I was young (aka a few years ago), I went on a class field trip to Paris. At the base of the Eiffel Tower, I had a strong feeling that something terrible was going to happen if I went up the tower. I had to go up, and it remains one of the most enjoyable and memorable experiences of my life.

I propose an experiment. Every time you predict something, or have a feeling something's about to happen, you write it down in a notebook within 24 hours. Every prediction must have a timeframe--you can't just say "Barack Obama will die" or "something bad will happen to me", because both of those are certain to come true at some time. If you forget to write it down in 24 hours, or if the event happens before you get a chance to write it down, don't write it down (it doesn't count). After a predetermined amount of time, say half a year, you look at the notebook and count up the events that did happen and the events that did not. For this to work, you have to be very disciplined in using the notebook. Under no circumstances can you revise previous entries, excuse yourself for missing the prediction timeframe, excuse inconsistencies between your prediction and what actually happened, add in entries after 24 hours have passed, or start counting up entries before the pre-determined amount of time has passed. I suspect that if you conduct this experiment, you'll find very few correct predictions amongst a vast number of completely incorrect ones. --99.227.0.168 (talk) 17:14, 31 December 2012 (UTC)

That would be a way for the OP to reconcile fact from fiction, especially if the OP is prone to making predictions. Some people obviously are and have faulty memories of them, but not everyone. Since I'm uncertain about most future events my notebook would be fairly void. -Modocc (talk) 18:27, 31 December 2012 (UTC)

I think the notebook experiment is an excellent idea. It requires extreme honesty and self-monitoring though...perhaps it would be better to have a close friend fill out the book on your behalf and verify which predictions come true. Here are some ways in which you can be deluded into thinking that you can predict the future:

1. You may make many predictions - and statistically, those are a small enough percentage to be accounted for by chance. You mentally bury the failed predictions and vastly inflate the successful ones.
2. You may make a prediction - and because of that prediction, subconsciously cause something to happen to match your prediction.
3. You may see an event and have a confabulation (a false memory) that you had predicted it.
4. You may make predictions that are sufficiently vague (eg "something bad will happen to me today") that you are almost certain to be able to find a match.
5. You may have some knowledge that enables you to make a prediction of something that's very likely to happen.

The notebook approach will reveal #1 and #3 - but #2, #4 and #5 are harder to pin down. SteveBaker (talk) 18:59, 31 December 2012 (UTC)

A very close friend of mine has had several seemingly inexplicable vivid and difficult to explain detailed precognitions, but the only vision I've ever had, that I'm aware of, happened when I unexpectedly felt a sudden awful emotion, a mix of hopelessness, dread and sadness; a deep sinking and sickening feeling that I had never experienced before or since which caused me to lay down, at which point I lapsed into a semiconscious dream in which I sensed everything spinning in addition to an image of what appeared to be luggage in a small space and a very dark landscape of water rushing around. This was a very brief vision, a few seconds at most and it happened just before sunset on the day John F. Kennedy, Jr. plane crashed. Just a coincidence I'm sure (see our article [21] on interpreting coincidences), mainly because with some eight billion plus people on this planet various unusual coincidences will occur and we tend to publicize them when these happen and thus these seem salient... but if what happened to me was of something that runs much deeper, like some sort of block time phenomena, science nor any garden tramping mutt has yet to pull back the curtain. -Modocc (talk) 19:50, 31 December 2012 (UTC)

If you get a chance, read in Johnny Cash's autobiography, about a day when everyone in the family had a sense of forboding about the day, including his brother, who nonetheless went to his job at the sawmill, and suffered a fatal injury. This kind of thing may indeed be all confirmation bias or some kind of natural intuition or just coincidence, but it's still possible there's something there. I call it "bad vibes". ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:37, 2 January 2013 (UTC)

So is there a scientific explanation for "bad vibes" ?--Jonharley667 (talk) 18:14, 2 January 2013 (UTC)

What accounts for the heavy taste of Beer?

I always assumed there was starch in beer, hence light beer without the starch. Turns out that's way off. So what exactly does make beer taste heavy compared to wine and liquor? μηδείς (talk) 22:49, 31 December 2012 (UTC)

Surely that depends entirely on the kind of beer? Weak American lagers are way lighter than wine, but a good decent English ale can be quite heavy. Don't think there's a single answer to it. However, there is a lot of sugars and complex carbohydrates in most beers compared to wines and spirits, so that probably accounts for a lot of the 'heavy' taste. Fgf10 (talk) 23:01, 31 December 2012 (UTC)

1. What is a "heavy taste"?

2. Is it universal, in every beer in every country?

3. In my country, Australia, "light" beer means lower alcohol. I get the impression the OP is talking about lower kilojoules (or calories). Can this be clarified please? HiLo48 (talk) 23:19, 31 December 2012 (UTC)

I'm enjoying Bavaria 8.6 right now. It is definitely got a heavy taste! Although North American flavor have only 7.9% alc./vol. So I would agree, heavy would mean higher alcohol content. But there might be some other things that affect taste. Think of Guinness, dark varieties do taste heavier... Happy New Year! TMMForever (talk) 00:00, 1 January 2013 (UTC)

And btw, this Bavaria taste way heavier then 13% alc./vol. Merlot or other vines with high alc content... But sorry, not sure as to why. TMMForever (talk) 00:14, 1 January 2013 (UTC)

Beer has a 'body' to it that wine and liquors don't have, similar to the way milk and orange juice have a body but water and soda do not. Some beers have a stronger body than others--and while dark beers tend to have more 'body' I don't think it's due to the darkness itself. For example, DAB Alt, which is dark, has a very crisp, soda-like texture. I had always assumed this was due to dissolved sugar or fiber. But our beer article implies there is no fiber, and this website implies beer has no glycemic load. As for lite beer, I had always assumed that meant low in sugar, but our article says it is only lower in alcohol content--which is what got me wondering when I read it. I generally drink red wine or liquor, but over the holidays my family always has a lot of beer, and I like Guinness. Two bottles of that will fill me to the point of not wanting to eat, while two glasses of wine would never do that. Given I'm watching my blood sugar, I am wondering if beer is worse than liquor, but the website I linked to implies it is not. So I am left wondering what exactly it is that leads to the beer's 'body'. μηδείς (talk) 01:21, 1 January 2013 (UTC) PS, Yes, I have drunk beer in Germany, Switzerland and Austria, there is no difference--that is, beer of all sorts in all countries has this body and liquor doesn't. μηδείς (talk) 01:26, 1 January 2013 (UTC)

Protein apparently. From Mash ingredients: "Corn was originally introduced into the brewing of American lagers because of the high protein content of the six-row barley; adding corn, which is high in sugar but low in protein, helped thin out the body of the resulting beer. Increased amounts of corn use over time led to the development of the American pale lager style." -Modocc (talk) 03:28, 1 January 2013 (UTC)

Sounds like you're asking about the "mouthfeel" of a beer amongst other things. Beer is far more complicated to make than wine, which is basically grape juice and yeast: beer/lager is basically malted barley, yeast, hops and water (with some other stuff as adjuncts). The way the barley is roasted contributes a lot to the colour, taste and body of the beer: a very pale malt will produce a pale beer. Crystal malt is slightly caramelised and is used in most bitters and milds in the UK. Black malt is the darkest and is used in stouts and porters such as Guinness, looks and tastes burnt. And then there's the type of yeast and length of fermentation of the beer/lager. Not forgetting the nature of the water (liquor to brewers) - has it been Burtonised? Oh and what variety/varieties of hops are used? We have an article on Cask ale for your delectation. As for what you refer to as "liquor" (which sounds like what the UK calls "spirits), whiskey is basically distilled beer. --TammyMoet (talk) 10:33, 1 January 2013 (UTC)

Yes, by liquor I mean what them highfalutin' folks both here in the states and them in yonder strange jurisdictions calls spirits. μηδείς (talk) 21:37, 1 January 2013 (UTC)

Mouthfeel is a much more general term, but it would obviously include what I am talking about. Protein seems likely, given it is a significant if slight nutrient listed for beer. But what sort of protein then is clear and water/alcohol soluble? I am still not clarified. μηδείς (talk) 21:33, 1 January 2013 (UTC)

January 1

Industrial Revolution and Coal

The Industrial Revolution used and began our use of coal. But won't coal be used up? What is the answer of the people who began, invented, and developed the Industrial Revolution?

Republicanism (talk) 00:37, 1 January 2013 (UTC)

Of course sooner or later it will be used up -- but it will not happen for at least 400 years, so this is not an urgent issue at this time. 24.23.196.85 (talk) 00:49, 1 January 2013 (UTC)

It's unlikely that we could actually consume the remaining coal before we make the planet virtually unlivable...hence we won't run out of coal. If we have sense, we'll stop using it long before it actually runs out. The people who started the industrial revolution were (at the outset) using so little coal, that the issue of if/when we'd ever run out was simply not a problem. It's only as that use accelerated through the next century that the possibility of running out might be considered. SteveBaker (talk) 00:56, 1 January 2013 (UTC)

not a place to debate global warming, the question isn't even about it
The following discussion has been closed. Please do not modify it.
"Virtually unlivable" in what way? If you mean smog or acid rain, this can easily be mitigated by scrubbing the sulfur out of the smoke, as is universally done today. 24.23.196.85 (talk) 01:42, 1 January 2013 (UTC) I imagine he meant global climate change due to increased atmospheric carbon dioxide. I certainly hope we will have better energy options than coal, before that happens. StuRat (talk) 03:41, 1 January 2013 (UTC) The notion that CO2 is responsible for climate change is disputed -- there are many other factors at work here, including an increase in solar radiation, and/or the action of trace gases (especially glyoxal and its derivatives). Also, climate change will not make the planet "virtually unlivable" -- in fact, it can actually benefit the civilized countries (especially Europe and Canada) by increasing agricultural productivity. 24.23.196.85 (talk) 04:05, 1 January 2013 (UTC) Sweet racism bro. Those uncivilized brutes in Africa totally deserve what climate change will bring. 24.255.30.187 (talk) 06:33, 1 January 2013 (UTC) So you want all of us Americans to cripple our own energy sector and set our economy and culture back by maybe two centuries just because of the off chance that some Stone-age troglodytes might get their land flooded if we don't? What kind of crazy, self-hating thinking is this? 24.23.196.85 (talk) 00:50, 2 January 2013 (UTC) At this point, the only ones who deny that CO2 causes climate change are right-wing politicians and any "scientists" on their payroll. StuRat (talk) 06:38, 1 January 2013 (UTC) Even among those people, very few deny that CO2 causes warming, since the physical fact that CO2 is a greenhouse gas is indisputable. They just deny that warming has in fact happened on Earth, or if it has, that it's anthropogenic. --99.227.0.168 (talk) 16:58, 1 January 2013 (UTC) It is worth noting that with carbon sequestration we might be able to use up all the coal, oil shale, and assorted such goodies without getting overheated - if we are clever enough to do it but not clever enough to outsmart ourselves, that is. (I am primarily thinking of the carbonate formation under "chemical processes" in that article) Wnt (talk) 13:23, 1 January 2013 (UTC) Being one of "those people" I think it is clear that the extra CO2 humans do contribute to the atmosphere does contribute to increased warming, but that other factors obviously hugely drown out that signal (look at the warmth of the late middle ages and the Roman era), and that a massive socialist redistribution scheme is not the answer to any problem if an anthropogenic one is ever conclusively demonstrated. I am also hugely in favor of nuclear power, a consumption (i.e., carbon and other materials) tax, and encouraging the development of fusion via tax and patent incentives. That actually seems like a rather sober and objective viewpoint if you ask me. μηδείς (talk) 21:29, 1 January 2013 (UTC) Except for the part about fusion power, it is. Fusion is at least fifty years away from being commercially viable; nuclear fission, on the other hand, is not only viable but is actually cost-competitive with coal and natural gas, and is also very safe for the most part (especially with the new generation of super-safe nuclear reactor designs in development right now, like the lead-bismuth-cooled fast-breeder, or the General Atomics graphite-helium reactor). 24.23.196.85 (talk) 01:01, 2 January 2013 (UTC) I don't have an educated opinion as to how far distant viable fusion power is (and 50 years is soon) but I am in favor of granting a fifty year patent on it and waving all tax on profits associated with it for that period. That should incentivize it like you can't imagine. μηδείς (talk) 02:46, 2 January 2013 (UTC) (ec) And I'm a socialist, so we could squabble all day. Instead, since this is the science reference desk, I'll provide a scientific reference, because there's an overwhelming consensus among climate scientists against your unsupported assertion that "other factors obviously hugely drown out that signal". From the Medieval Warm Period article: "globally the Medieval Warm Period was cooler than recent global temperatures" (with a citation). From the graph in that article, the temperature peak representing the MWP is 0.1-0.2 C in height and a few hundred years in width, whereas the global temperature has risen 0.8C since the beginning of the 20th century. I could not find any temperature estimates of the Roman Warm Period. --99.227.0.168 (talk) 01:05, 2 January 2013 (UTC) Your "overwhelming consensus" is that of politically motivated liars who've been caught out over and over. There's no suitable long term sample, just recent flawed cheerleading models for the refuted hockeystick. But do cite away til you feel warm and cozy. μηδείς (talk) 02:42, 2 January 2013 (UTC) Even if this is true, this does not prove that CO2 is responsible for the warming trend -- there's a lot of other crap being released into the atmosphere that didn't used to be back then, like methane, nitrogen oxides, all sorts of halogenated hydrocarbons, and the above-mentioned glyoxal derivatives, ALL of which are considered to be much more potent "greenhouse gases" than CO2. Add to that the concurrent increase in solar radiation (which is right now the only plausible explanation for the warming trend currently observed on Mars), and then anyone can see that CO2 is by far NOT the only factor at play here, nor is it even necessarily the biggest. Correlation does not imply causation! 24.23.196.85 (talk) 01:23, 2 January 2013 (UTC)

If you are asking historically — e.g. what did the people who started the Industrial Revolution think — it's worth pointing out that 1. nobody really consciously started the Industrial Revolution, and 2. the amount of coal is quite vast, even today, and was considered essentially limitless at the time of the Industrial Revolution. So I doubt they worried much about it running out in the short term. --Mr.98 (talk) 03:29, 2 January 2013 (UTC)

Eliptical Machines

I am using an eliptical machine as a cross training activity for long distance running. I find something about them strange. Why do I not feel sore at all the day after a strenous workout on an eliptical machine (eg doing fast paced intervals or going for a long period of time), but feel sore the next day after a equally strenous run or weight lifting workout? I know they are supposed to be low-impact, but I would expect to feel some muscle soreness. Same thing with swimming. -anon

I'm guessing you're in good shape, so the exercise doesn't overtax your muscles and cause soreness that way. Thus, the only soreness you normally feel is from microscopic injuries caused by impacts. You might want to increase your resistance/weight/reps/time to make it more of a challenge. StuRat (talk) 03:35, 1 January 2013 (UTC)

Stu's on the right track. It probably also means that you have a good elliptical, or at least one that suits you well. I've used at least three different styles of elliptical and had different experiences with each regarding muscle tiredness, joint sensitivity, and so on. Matt Deres (talk) 04:40, 1 January 2013 (UTC)

My experiences and opinions. I think elliptical machines are very low impact. Your feet are on the paddles ALL THE TIME. And your muscles are working nearly ALL THE TIME. The machine is quite friendly to your legs. You can you your arms if you really want to. I can usually "run" maybe 1.5 times of distance on a elliptical machine than actually jogging.

This may not be a fair comparison because we have air conditioning in a gym. This is not fair. It can be very hot outdoors. I also drink less when I am jogging. You always have water in a gym.

I think treadmills are friendlier than jogging and elliptical machines are even more friendlier than treadmills. However, jogging outdoors can be much more fun. I just hate to jog in summer. -- Toytoy (talk) 16:05, 1 January 2013 (UTC)

Did any of you use an eliptical at any point? What is a suggestion as to how much I should increase the duration of my workouts every sesson? Is increasing the duration of my workouts by 2 minutes each sesson reasonable? — Preceding unsigned comment added by 99.146.124.35 (talk) 23:14, 1 January 2013 (UTC)

We can't give that sort of advice for practical and legal reasons, but you may have a personal trainer or other professional available at your gym who can--do ask them. μηδείς (talk) 02:37, 2 January 2013 (UTC)

The advice I was given was to slowly increase the workout until I do get sore, or at least feel muscle fatigue. This is basically the "no pain no gain" advice, although I think "pain" is a bit strong. You should feel it, but not be in agony. You might also want to strap weights on your legs or otherwise increase the difficulty level. StuRat (talk) 03:21, 2 January 2013 (UTC)

Alexander graham bell

complaint over priority referred to article talk page
The following discussion has been closed. Please do not modify it.
Alexander graham bell did not invent the telephone, that went to an inventor a few years earlier. Putting a sentence saying he invented a working telephone, insults all pioneers and their inventions. You should change the reference to include the Alexander Graham was created the first telephone the concept and design for which was invented by.... I cant recall the person who actually invented the phone. — Preceding unsigned comment added by 124.148.227.176 (talk) 03:35, 1 January 2013 (UTC) This belongs on that talk page. However, Leonardo da Vinci had diagrams of helicopters [22], but his designs wouldn't fly, so should he be credited with their invention ? StuRat (talk) 03:38, 1 January 2013 (UTC) Bell's article says he is credited with inventing the first practical telephone, a big difference from what you're complaining about. Invention of the telephone lists various candidates for the telephone's daddy. Clarityfiend (talk) 05:29, 1 January 2013 (UTC) Closing--OP has been refererred to article talk page. μηδείς (talk) 16:35, 1 January 2013 (UTC)

Lizzie Velazquez - A Rare Condition

Speaking in a strictly academic capacity with perfect propriety, my first question is what actually is the name of the rare condition Lizzie Velazques has? I can't seem to find anything on wikipedia. I don't think she has a page. All the articles, everything I see on google/youtube, no one actually mentions the name of the condition. They just keep saying that it is such a rare condition that only 2 or 3 people in the world are known to have it. Any useful informative references on the disease will be useful. Second question, from what I understand, she weighs just 60 pounds and has no adipose tissue, and cannot create muscle, store energy, or gain weight. She has no body fat or muscle tissue but then how come her mammary glands are so swollen? Maybe it is my ignorance of human physiology but I thought that subcutaneous adipose tissue (according to wikipedia anyway) gives breasts its shape and size. So if she's not supposed to have any fat or muscle in her body, then how come her breasts are so big and shapely? At least to me they look unusual compared with the rest of her stature. Is it known if she ever got artificial enhancements/supplements or if the condition takes away fat/muscle from certain parts of the body and leaves the rest alone? Thanks! - Looking for Wisdom and Insight! (talk) 10:49, 1 January 2013 (UTC)

Second Google hit references [23] which says neonatal progeroid syndrome is the current best guess (we only have progeria written so far); during her childhood de Barsy syndrome had been suspected, but she didn't have learning difficulties. It says she is currently being studied by Professor Abhimanyu Garg, MD, at the University of Texas Southwestern Medical Center in Dallas, who came up with the NPS diagnosis. Wnt (talk) 13:17, 1 January 2013 (UTC)

Perhaps they are just falsies or implants, allowing her to look normal in at least one respect. StuRat (talk) 03:17, 2 January 2013 (UTC)

Air refueling stealth fighters

F-22s and F-35s are capable of air refueling.

Why do they need air refueling? Certainly, they need extra fuel to extend their ranges.

But unlike many other airplanes, these airplanes do not have hardpoints, as a result, they can always add a central hardpoint for an external fuel tank.

I know that external fuel tanks are radar reflectors.

But air refueling also gives away a stealth fighter's position. The tanker airplane is a much larger radar reflector and air refueling is slow.

On the other hand, external fuel tanks are lighter, more efficient and they can be dropped.

Why don't stealth fighters use external tanks? -- Toytoy (talk) 15:54, 1 January 2013 (UTC)

From Wikipedia's article on the F-22: "the wings include four hardpoints, each rated to handle 5,000 lb (2,300 kg). Each hardpoint has a pylon that can carry a detachable 600 gallon fuel tank or a launcher holding two air-air missiles."

Our article on the F-35 don't mention it, but this link seems to point ot at least two of the hardpoints being plumbed for droptanks. Since the F35 is still years away from being in service, take any information regarding it with a grain of salt though.

WegianWarrior (talk) 16:18, 1 January 2013 (UTC)

You can carry more weapons without a heavy external fuel tank. And carrying an external fuel tank for the home trip into a combat zone makes you slower and less maneuverable. Air refueling is usually done in an area considered relatively safe from enemy attack. (Have planes ever been attacked during the procedure?) See more in Aerial refueling. PrimeHunter (talk) 16:45, 1 January 2013 (UTC)

And using a safe area for refuelling (which is necessary mostly because the tankers are vulnerable) means that if the enemy does realise the fighter's presence, they'll likely lose track of it once it detaches from the tanker and moves into the hot zone. With the exception of a tiny handful of convert assassination and first-strike operations, the purpose of stealth isn't to conceal the presence of the aircraft, but to prevent enemy missiles from successfully engaging it. The air defence system around Baghdad in 1991 was perfectly well aware that there were F117s around (once stuff started exploding) but they couldn't get their radar-guided weapons to acquire a lock on them. I guess there may be some interest in a stealthy refuelling system, to support the tiny number of cloak-and-dagger strikes, and perhaps to maintain stealthy drones. -- Finlay McWalterჷTalk 17:09, 1 January 2013 (UTC)

Is there any reason why there couldn't be a stealth refueling plane, or why refueling itself couldn't be stealthy? I mean, stealth doesn't require a plane to perform like a fighter, does it? I imagine they don't tell us everything they waste money on... Wnt (talk) 19:13, 1 January 2013 (UTC)

It seems that it could in principle be done, but there's not a lot of good reason to do it. (Note that even very 'stealthy' aircraft would be vulnerable during midair refuelling; the aircraft performing such a manoeuvre are necessarily flying relatively slowly, carefully maintaining constant speed and altitude. I also don't know what wrinkles might occur in developing a stealthy fuelling boom.) Consider the biggest 'stealth' aircraft ever built, the Northrop Grumman B-2 Spirit 'stealth bomber'. Normally, it carries up to 76 metric tons of fuel, and up to 23 tons of ordnance; it has an operational range of a whopping 11,100 km. Conceptually, there's no serious difficulty with stripping out the bomb racks and replacing them with another 23 tons of internal fuel storage, deliverable up to a third of the way around the world. I suspect that if you cut into the B-2's own existing tanks to trade range for deliverable capacity, you'd probably get close to the same fuelling capabilities as a KC-135.

For reference, the McDonnell Douglas KC-10 Extender carries a maximum fuel load of 160 tons and has an operational range of 7,000 km; its still-in-service predecessor the Boeing KC-135 Stratotanker carries up to 91 tons and has a range of 2,400 km. (The actual amount available for refuelling other aircraft depends on how far the tanker has to fly and how long it has to loiter; our articles don't break out the specific amount of fuel available for transfer from these tankers versus the amount required for their own use.) Our hypothetical B-2 Stratotanker costs about $800 million (plus development costs for the midair fuelling variant), whereas a KC-135 costs about $40 million. TenOfAllTrades(talk) 21:35, 1 January 2013 (UTC)

Our article on the F22 says: "Range: >1,600 nmi (1,840 mi, 2,960 km) with 2 external fuel tanks" - so it does indeed have the capability to extend it's range in that way. Furthermore: "Fuel Capacity: 18,000 lb (8,200 kg) internally, or 26,000 lb (11,900 kg) with two external fuel tanks"...and that's the problem. With in-flight refuelling, you can almost double your range - with external tanks you gain at most maybe 40% more range. (Also, those tanks cause drag and extra weight - which means that the aircraft is less fuel-efficient when carrying them - so they clearly don't extend range by as much as you'd expect from the raw numbers). Furthermore, you can (and routinely would) refuel on the way out to the target and on the way home - which triples your range. SteveBaker (talk) 02:08, 2 January 2013 (UTC)

I noticed that F-22's long flights over the Pacific Ocean require external tanks. I still think that carrying multiple external tanks are more reasonable than air refueling.

You just drop the tanks and then you're OK. -- Toytoy (talk) 03:40, 2 January 2013 (UTC)

About vulnerable stratotankers, it might be less of a vulnerability than you think, with all those fighters moving back and forth. It could be an issue if there was another (non-US) power using stealth aircraft, trying a sneak attack on the refueling fighters and the KC herself, but as of now, non-stealth fighters are detected from 100's of miles away, and refueling doesn't last that long. They could intercept any non-stealth intruder without penalties to their weight/drag/stealth.

Keep in mind that applying a layer of stealth skin to a drop tank is not an option. You don't want to give away stealth technology, lest the enemy copy or defeat them.

About stealth refuelers, some jets including the Tornado GR.4 have been converted to tankers in small numbers, so it is likely that some stealth planes have been converted, too. - ¡Ouch! (^{hurt me} / _{more pain}) 08:33, 2 January 2013 (UTC)

Ahem, Panavia Tornado. - ¡Ouch! (^{hurt me} / _{more pain}) 08:57, 2 January 2013 (UTC)

Of course we're missing another use of inflight refuelling - which has little to do with extending range. When you want to carry the maximum possible amount of munitions. The maximum weight that the aircraft can take off with is considerably less than the amount it can fly straight and level with. So one trick is to take off with a minimal fuel load (thereby allowing more payload to be carried) and to almost immediately refuel when at altitude. Once at altitude, the total of fuel plus payload can safely exceed the maximum take-off weight. SteveBaker (talk) 15:27, 2 January 2013 (UTC)

Gravitational and magnetic force

why we can't relate gravitational force with magnetic force? since most of the living and non living things contains elements that can be attracted by magnetic force. 116.202.68.193 (talk) 16:31, 1 January 2013 (UTC)

I would attempt an answer to that question if only it made any sense... Dauto (talk) 17:58, 1 January 2013 (UTC)

I'm guessing they mean "replace it" as in artificial gravity in a space station.--Gilderien Chat|List of good deeds 18:39, 1 January 2013 (UTC)

They are similar in some ways, but not similar enough. For starters, everything accelerates exactly the same under gravity (this has been tested to one part in ten trillion), but some magnets are much stronger than others. Plus, magnetism can't explain the bending of starlight or the anomalous precession of Mercury's orbit. -- BenRG (talk) 18:40, 1 January 2013 (UTC)

Ben, I'm not sure I understand what you mean by "everything accelerates exactly the same under gravity" - are you referring to Galileo's experiment showing that different masses accelerate at the same rate (and thus fall at the same rate) due to gravity? Because if so the obvious rebuff is, just as some magnets are much stronger than others, some masses are much more, er, massive than others... (so the distance between two 1-kg masses finitely far apart in a vacuum with no other forces decreases faster than that between a 1-kg mass and a 1-g mass in the same situation, for example).

@OP: I'm surprised no one's mentioned this, but there is the fact that magnets have poles, and we have never discovered a magnetic monopole (this not to say they don't exist, of course), and precisely the opposite, gravity is only ever attractive so far as we can observe, there is no "negative mass" that repels the mass we observe (even antimatter attracts matter via gravity, likewise darkmatter). Even if there were, it wouldn't line up with how we observe like charges and magnets to repel, because it would have to be opposites that repel and likes that attract (to see why this is, consider the sun, the earth, and the moon. They all attract each other, so they are likes, because if they were opposites this couldn't be the case) 72.128.82.131 (talk) 04:20, 2 January 2013 (UTC)

General relativity and electromagnetism do fit together rather nicely, in the form of Kaluza–Klein theory. There's also gravitoelectromagnetism, although that's just an analogy that only works in an approximate sense under certain conditions. Red Act (talk) 22:54, 1 January 2013 (UTC)

Any studies on whether whale strandings may have analogue in human stampedes?

67.243.3.6 (talk) 17:09, 1 January 2013 (UTC)

• The dynamics are unsimilar, whales are not crowded onto the beach or crushed or trampled by other whales. (My personal bet is that there is a microorganism to blame which spends part of its life cycle on the beach, similar to other parasites which drive their hosts to odd behaviors like rabies or fungi that cause snails and ants to climb to high locations in order to be eaten or to spread spores in the wind.) μηδείς (talk) 21:18, 1 January 2013 (UTC)

"Citation needed". :) Though it is a creative idea, and could be true. I would suspect that there could be a common basis - stranding of whales and dolphins are widely though not unanimously blamed on loud sonar arrays (see whale beaching), and I suspect that loud noise contributes greatly to the confusion in some human stampedes. But I can't find a reference for that, either... Wnt (talk) 02:03, 2 January 2013 (UTC)

If you are asking me regarding my personal guess, I already quoted myself. Do you want me to put it on my talk page so someone else can quote me here? μηδείς (talk) 02:29, 2 January 2013 (UTC)

Meideis' ridiculous speculation aside, see beached whale#Causes for more credible explanations. Beaching of single whales is much more common than beachings of multiple whales, and is usually caused by injury or disease. Multiple-whale beachings are sometimes caused by strong social cohesion--one whale sends out a distress call while close to the shore, and other whales follow. By contrast, human stampedes are caused by panic or disasters, and death is usually by asphyxiation. If you've been to any major event, like Toronto's New Year countdown, you know how easy it is for the crowd to squish you when lots of people are pushing. I don't see any obvious connection between the two, but if the OP wants to point out what kind of similarities he's thinking of, he might receive a better answer. --99.227.0.168 (talk) 05:41, 2 January 2013 (UTC)

Hiding behind an IP does not give you any special privilege to ridicule the posts of others here. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:26, 2 January 2013 (UTC)

This is a reference desk, not a "make up your own theories and post them" desk. I see no rule that says IP users cannot correct non-IP users when the non-IP user posts no references and the IP user does. --99.227.0.168 (talk) 07:07, 2 January 2013 (UTC)

Your term "ridiculous speculation" does not belong here. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:15, 2 January 2013 (UTC)

Well, editors really ought to be providing referenced facts rather than "personal bets". However, "It is by politeness, etiquette and charity that society is saved from falling into a heap of savagery". Alansplodge (talk) 17:53, 2 January 2013 (UTC)

Anyhow, back to the point. I've had a fairly good trawl through Google and found Keeping Together in Time, or the Natural History of Social Cohesion. A Critical Evaluation of W.H. McNeill's New Book (1995) is an article that seeks to compare a new work on human social cohesion with mammalian behaviour. The Google search result for the page says "It (presumably group behaviour) may take precedence over all other forms of behaviour, as for instance in lemming migrations or mass stranding» of whales; but much more often it is integrated with other modes of social interaction." You can't view the article without subscription. Sorry, that was all I could find. Alansplodge (talk) 18:17, 2 January 2013 (UTC)

Understanding the EPR paradox

In the article on the EPR paradox an explanation is given on how the experiment was or can be performed. The part about this experiment I'm trying to get is not the faster-than-light aspect, but rather the certainty or not of a state.

I'm very familiar with 3D vector math, so the part that puzzles me is when they talk about the spin that can be seen as "a superposition of two states". I view the spin as an "axis" (about which the electron "spins"). Surely this must lead to an infinite number of possible states, corresponding to directions. Is the article saying that the experiment can be set up in such a way that only those two states are possible?

And then, when the measurements along a particular axis is made, are we talking about projections (like dot product) or is there some quantum effect that causes the vectors to become 100% parallel to the measured axes? Or is some quantum effect simply making all measurements binary (with no possibility of zero or small values) along all possible axes? 105.236.57.198 (talk) 19:03, 1 January 2013 (UTC) Eon

This is a basic fact of spin (quantum mechanics). Spin can be along any axis, but when measured, it always has one of a few discrete values according to which way you looked. As I understand, remeasuring it from another angle has a chance of getting the other value, depending how wide the angle - and if you remeasure again from the first angle, it could then be different from what it was the first time! So defining the axis is ... difficult. Most of the physics types will say don't even think about it in classical terms, it's just a number, but we find this ... unsatisfying. Not when it still sorta kinda is like something you can picture. Note that the general idea that angular momentum is quantized is absolutely fundamental to quantum mechanics - people might talk about how, say, an electron has quantized "energy", but really, it has equally spaced increments of angular momentum that determine its energy because if it had any more or less with a given angular momentum it wouldn't be in orbit. Every photon carries the exact same angular momentum, the reduced Planck constant, and that is what an electron changes by when it flips from one spin state to the other, just as when it goes up a level in energy. Wnt (talk) 19:16, 1 January 2013 (UTC)

Thanks for an excellent summary. Actually, I couldn't figure it out from that description because it doesn't go all the way. I found this article by a user here that continues the explanation to the point that I fully understand the weirdness of entanglement. It doesn't appear to be an official article, but I think it would be great if that was included. The official article merely "tells" one how it works. That explanation convinces one by tracing the path to the conclusion. 105.236.57.198 (talk) 20:10, 1 January 2013 (UTC) Eon

Astronomical naming conventions

I get a bit confused over the names of some things. Our star, and its planets, are collectively known as the "solar system", but "solar" comes from Sol, the name of our star. What, then is the general name of such a system called? Star system apparently refers to systems of multiple stars, while planetary system seems to exclucde the star (the article specifically mentions The Sun and its planetary system).

Similarly, what would a "solar flare" on any other star be called? A stellar flare? 90.193.232.232 (talk) 19:24, 1 January 2013 (UTC)

• The expected term would be stellar system, but you don't often find it, most people being ignorant of Latin and etymology in general nowadays. You do hear "planetary system". μηδείς (talk) 19:53, 1 January 2013 (UTC)

Basic commutativity. If the sun is a star, then a star is a sun, right? Poetically I've heard of the "children of other suns". I would say that there are many solar systems but only one Solar system. The same astronomers probably have a pet "Dog" :) But I'm not an astronomer, sorry. Wnt (talk) 20:01, 1 January 2013 (UTC)

This seems to me just like first having the Moon, and then finding out that there are other natural planetary satellites and calling them moons. There are lots of moons but only one Moon. I've often heard of other stars referred to as other suns, although there is only one Sun. So the analogy would be that there are many solar systems but only one Solar System. Words' meanings evolve as semantic needs evolve. Duoduoduo (talk) 22:25, 1 January 2013 (UTC)

We have adequate terminology now, if only I we were able to force convince people to use it. In the long term, better usage will evolve. Then people will move to other stars and the provincials will start talking about earthquakes on their new planet and sunstorms on their new star. Depressing. μηδείς (talk) 02:27, 2 January 2013 (UTC)

An earthquake is when the earth shakes, not when the Earth shakes, so "earthquake" is fine on Mars, when the good red Martian earth starts quaking beneath your pressure-suited feet. --Trovatore (talk) 05:39, 2 January 2013 (UTC)

As noted below, Moonquakes and Marsquakes and even Sunquakes are attested. μηδείς (talk) 17:18, 2 January 2013 (UTC)

The terms earth, moon, planet and sun are all carryovers from the assumption that we are the center of the universe... which, for most practical purposes, we are. The earth is the ground we stand on, the "moon" is cognate with the "month", the sun is cognate with words that mean "shine". Medeis is right that if and when we migrate to other planets and stars, terms will evolve. If you're on Mars, there's a reasonable chance you'd call it a "Marsquake", but if we establish a civilization there, in some future generation they might come up with different names, as the notion of it being the realm of the god of war would seem silly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:23, 2 January 2013 (UTC)

No, earth meaning dirt is the older usage. The planet is named after the dirt. There's nothing wrong with talking about an earthquake on Mars, as it is indeed a quaking of the earth that's there. (Not sure Mars actually has tectonics at all, but that's a side issue.) --Trovatore (talk) 07:48, 2 January 2013 (UTC)

Sure, and that's where the planet's name came from. At that time, no one knew there was soil on other planets (not for sure, anyway). You may find Quake (natural phenomenon) of some interest. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:56, 2 January 2013 (UTC)

You're missing the point, and at this point I have to suspect you're being deliberately dense. It's not called an Earthquake, meaning the planet shakes. It's called an earthquake, meaning the dirt shakes. Mars has earth too. --Trovatore (talk) 08:20, 2 January 2013 (UTC)

Well, who should I believe, you or the wikipedia article? ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:23, 2 January 2013 (UTC)

The article does seem to source "moonquakes" and such, but surely those words were chosen a little facetiously. If not, it's just dumb. --Trovatore (talk) 08:25, 2 January 2013 (UTC)

I've certainly heard the term "moonquake" before. I can't vouch for the others as such. Maybe you would call it a Marsquake if you were observing from earth, and an earthquake if you were actually standing on Mars, or maybe just a "quake". Mars certainly has solid ground and some kind of soil or ground (let's not say "dirt"), but there's no guarantee that citizens of Mars would use the term "earth" to indicate the surface, at least not right away. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:41, 2 January 2013 (UTC)

It's interesting that the Latin terra is likewise used for both the land and for the planet.[24] The two concepts are closely linked. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:43, 2 January 2013 (UTC)

'Marsquake', How Earthquakes On Mars Could Sustain Alien Life is a Huffpost Tech article dated Feb 24, 2012 that is based on an interview with a NASA-affiliated scientist. Others based on the same report and with the same approximate date are [25] and [26]. Duoduoduo (talk) 13:42, 2 January 2013 (UTC)

However, the abstract and title of the study that those news articles are reporting on refer to "paleomarsquakes" and "marsquakes". Duoduoduo (talk) 13:58, 2 January 2013 (UTC)

Geology of Mars. Duoduoduo (talk) 12:54, 2 January 2013 (UTC)

If we ever got to live on a planet orbiting another star, I'm pretty sure we'd still say things like "What a pretty sunset!" and "Oh, look! A full moon. How romantic!" - and not get into tangled new vocabulary like "Alpha-Centauri-rise" or "A full Triton". It seems that when uncapitalized, "sun" and "moon" refer to whichever star and moon you happen to be nearest to and when capitalized "Sun" and "Moon" refer to the Earth's sun and moon. It's only in the last hundred years that it's mattered - and even then, not to many people and not in most conversations. But capitalization would rapidly get confusing in speech - so "Sol" and "Luna" are probably words we might take up if we lived elsewhere than on Earth and we needed to talk specifically about the Earth's sun and moon. In places like NASA, "earth" (as in dirt) is carefully called "regolith" in cases where ambiguity might result - and the Mars missions talk about "sols" instead of "days" to avoid confusion. Our language adapts as need arises. Words like "earthquake" are corner cases - but using terms like "moonquake" and "marsquake" makes it difficult to write sentences like "The comparative study of earthquakes on different celestial bodies is a branch of seismology." - you can't say "The study of quakes..." because the word "quake" can mean ground shaking other than of a geological origin (see Wiktionary). SteveBaker (talk) 15:14, 2 January 2013 (UTC)

Rydberg molecular hydrogen

A few more questions about Rydberg atoms forming Rydberg matter. (I also list some assumptions in case they're wrong...) Feel free to answer any part independently.

1. I assume it is possible for two Rydberg atoms of hydrogen to interact in such a way that they are not immediately disrupted, to form a Rydberg molecule of hydrogen with two protons and two electrons. ([27] describes one with three hydrogens, which I shall not even try to figure out.)

2. My recollection is that Rydberg atoms of hydrogen have something like n=20, maybe 50, and the electron can - somehow - be visualized as an isolated blob of negative charge revolving around a distant nucleus in a Keplerian orbit.

3. Suppose a Rydberg atom has a perfectly circular orbit, and does not emit a photon while being observed. Or suppose it has a perfectly linear orbit, with the electron falling straight through the photon on every oscillation. Can you call one a "50s orbital"? The other a "50p orbital"?

4. Suppose two Rydberg atoms are collided so that two electrons are somehow orbiting two protons in a stable configuration. What would that look like?

5. Is the bond qualitatively different if you have one electron with "n=49" and another with "n=50", as opposed to two with 50? Can you visualize the Pauli exclusion principle somehow because the spins have to be opposite for them to fall in the same orbital? Or is there a way to write a molecular orbital formula for the two electrons so that they sail neatly one after the other along the same course?

6. Is the angular momentum of each electron quantized in relation to each of the two protons? In relation to the other electron? In relation to the whole system? Do these conflicting demands for simultaneous quantization force them out of a perfectly elliptical orbit as measured?

Wnt (talk) 19:57, 1 January 2013 (UTC)

Brain question

I was wondering, since the brain is mostly controlled via electrical impulses, and you can mess with peoples heads by shocking parts of the brain (I think?), what would happen if you were to open up a persons skull and pour something like saline solution, or some sort of liquid that conducted electricity onto it? Would the brain short circuit? What if it were just dribbled instead of coating the whole of the surface? Gunrun (talk) 23:36, 1 January 2013 (UTC)

Neurons, including those in the brain, do indeed work on electric pulses, but they are not like currents flowing through a conductor: the ions are "pumped" chemically not electrically. So concepts like "circuit" in the electrical sense (and a fortiori "short circuit") simply do not apply. --ColinFine (talk) 00:14, 2 January 2013 (UTC)

However, it is possible to "mess with peoples heads by shocking parts of the brain" - see Electroconvulsive therapy. Don't try this at home. Alansplodge (talk) 00:56, 2 January 2013 (UTC)

A less-dramatic approach is transcranial magnetic stimulation. --Mr.98 (talk) 03:25, 2 January 2013 (UTC)

The brain is already immersed in saline solution, and it works just fine (in most people, anyway) -- so just on the face of it, the OP's suggestion won't work. 24.23.196.85 (talk) 01:07, 2 January 2013 (UTC)

Presumably the balance of the various ions that the brain uses would be kinda critical - so while dumping extra saline in there wouldn't short anything out - it would screw up all of the concentrations - and that might well be fatal. SteveBaker (talk) 01:45, 2 January 2013 (UTC)

The answer to this is complex. The conductance of the extracellular medium could vary, and would affect neural signalling. action potentials cross the membrane; even so, the voltage, and also specific ions that have to move, affect the opening of more channels up and down the axons and dendrites. Much of this happens inside the neuron where the change in medium might not affect it (depending on what exactly you did to it). See [28] for some basic biophysics of this - but I won't claim to have gone through it all. Wnt (talk) 01:51, 2 January 2013 (UTC)

Given the sophistication of the question, I think the prior answers (no, nerves and the brain don't work that way) are sufficient. The OP should read brain, neuron, and action potential, and then come back and ask for help if he wants it at that point. μηδείς (talk) 02:24, 2 January 2013 (UTC)

Replacing the CSF with saline would kill you, as Steve said. It doesn't have the calcium that is absolutely required for neuronal activity (and indeed for survival of all other cells. Cells are pretty good at concentration calcium, but stores would be depleted over time as they migrate across the concentration gradient. Fgf10 (talk) 11:45, 2 January 2013 (UTC)

CO2 laser - output power versus input.

I have a CO2 laser (100 Watt) which is rated for 23mA of power at the power supply. The power supply was shipped with the current limiter set somewhere down around 8mA...so the laser wasn't performing very well. So now I've adjusted the limiter to provide the 23mA required - and I'm definitely getting more "oomph" out of the laser now - although the only measure I have of that is how well it cuts holes in things - and that's not linear with the laser energy anyway.

The question is: Is the amount of output laser power directly proportional to the input - or is there something more complicated going on?

Another issue is that these lasers degrade slowly over time (I believe the seals are imperfect so you get impurities leaching into the CO2 gas - which reduces the power you get out of the machine). Would it be reasonable to assume that the current consumed by the laser would be a reasonable measure of that deterioration - or does it consume just as much input current but produce less laser energy?

If it helps, this is a water-cooled device.

TIA SteveBaker (talk) 23:52, 1 January 2013 (UTC)

To the first question, no. The maximum power output is at the point where internal resistance of the power supply is equal to load. --Gilderien Chat|List of good deeds 02:16, 2 January 2013 (UTC)

That would be the maximum power output of the power supply - that's not what I'm asking. The power output of the laser is my concern. Not all of the electrical energy going into the thing emerges as useful light - much is wasted in heating the thing up (hence the need to water cool it). I'm interested in the relationship between the current going into the tube and the light energy coming out of it. SteveBaker (talk) 14:53, 2 January 2013 (UTC)

It's impossible to answer this question without details of the laser construction and its cooling. Why don't you perform an experiment to see how much it heats up identical volumes of infrared-opaque fluid (or just water) for the same duration at different power input levels? 70.59.14.20 (talk) 18:26, 2 January 2013 (UTC)

January 2

New comet and meteor shower

C/2012 S1#Associated Meteor Shower says that the Earth will pass through the path of this new comet, and may experience a meteor shower. The comet is on a hyperbolic orbit. It seems to me that any particles that come off the comet will be on a similar orbit and would not be around to form a meteor shower. What is right? Bubba73 ^{You talkin' to me?} 02:55, 2 January 2013 (UTC)

Diagram of a comet showing the dust trail, the dust tail (or antitail) and the gas tail. NASA

Yes the dust tail will be on a similar orbit, but it is expected to be very long, and part of it will have arrived on our orbit when we come around to it.--Shantavira|^{feed me} 09:11, 2 January 2013 (UTC)

The article says "Its orbit is nearly parabolic", which presumably means that it is elliptical with an eccentricity of just below one. Bubba, why do you say it is hyperbolic?--did you read that somewhere else? "Near parabolic" appears in two different refs sourced by the article: New Scientist and Astronomy Now. Also, I don't think that the nature of the orbit (hyperbolic or elliptical near parabolic) should even affect the likelihood of a meteor shower -- the comet is from the Oort Cloud, which is way out there, so it will be a long time before the comet itself reappears even if elliptical. So as Shantavira says, any meteor shower would come from the dust tail of the current passage. Duoduoduo (talk) 13:10, 2 January 2013 (UTC)

The article gives the eccentricity as 1.0000015, which makes it hyperbolic. If particles come off the comet, wouldn't they continue on their orbit? That is, how will it make an annual shower? Bubba73 ^{You talkin' to me?} 14:55, 2 January 2013 (UTC)

Our article Comet tail has a diagram which I have copied here, showing a dust trail following the comet's orbital path, and a dust tail or antitail coming outwards away from the sun, but at a different angle to the gas tail. I'm no expert, so I stand to be corrected. Alansplodge (talk) 17:44, 2 January 2013 (UTC)

So it does. But I can't find anywhere that says the meteor shower would be annual. Where do you see that? Duoduoduo (talk) 17:44, 2 January 2013 (UTC)

Pass. Sorry, I'm already out of my depth here! Alansplodge (talk) 17:46, 2 January 2013 (UTC)

I took out the part about the possible meteor shower this morning because of wp:ball. Look back a little in the article history. It does say that the Earth will pass through the orbit annually and it did say that the first meteor shower could be in January 2014. That seemed to imply an annual meteor shower. Bubba73 ^{You talkin' to me?} 17:54, 2 January 2013 (UTC)

Unfortunately what you left in in that section was pointless without the point that you deleted. I've put it back in with a correction to conform with the source -- the source doesn't say anything about "annually". It's okay to give a statement of what astronomers predict -- many of our astronomy articles do that. Duoduoduo (talk) 18:10, 2 January 2013 (UTC)

Plants on Mars

To be clear, according to [29] no known plant can grow on Mars without artificial assistance. And yet I wonder. The atmosphere of Mars has about 600 Pa of pressure of carbon dioxide; by comparison, unless I went wrong somewhere, 0.039% of Earth's 101300 Pa is 39.5 Pa. So Mars has plenty of atmosphere for plants (provided they don't try to do respiration...). The climate of Mars includes temperatures up to as much as 81 degrees Fahrenheit. Debatably, conditions in Hellas Planitia can even allow the formation of liquid water (though we have a citation needed there) and the crater includes glaciers. And we know at least microbes can survive beneath glaciers. [30] But potentially, we might be even more ambitious: boreal trees survive freezing even in liquid nitrogen, if given a chance to prepare. [31] It is considered at least possible to develop UV-resistant plants in response to destruction of Earth's ozone layer.. [32] So ... could the NASA site be too pessimistic? Do any of the (would-be) exobiologists think that plant life, perhaps (with a little tinkering) even plants we recognize, could actually be able to grow on Mars? Wnt (talk) 03:31, 2 January 2013 (UTC)

Evidence of liquid water has been observed on Mars, but we don't really know how long it lasted. If any plants were brought to Mars and exposed to the naked atmosphere, wouldn't any water in them be prone to evaporate rather quickly? Evanh2008 ^{(talk|contribs)} 06:46, 2 January 2013 (UTC)

The Martian atmosphere has an average pressure of about 6 millibars, as I recall. By my math that would put the boiling point of water right around negative five C (I may have gotten some numbers jumbled there, though). I guess if you could find a place on Mars where there was moisture and temperatures consistently below that mark, plants should grow just fine. Evanh2008 ^{(talk|contribs)} 06:49, 2 January 2013 (UTC)

Yes, to retain water they might look more like a cactus, and perhaps use oils instead of water for their circulatory system. I certainly wouldn't say it's impossible for some form of life to exist on Mars, just that it would have to be fairly different from Earth life. However, some form of microbe living in underground damp soil seems more likely than plants, to me. StuRat (talk) 06:55, 2 January 2013 (UTC)

To clarify, I'm speaking of plants from Earth here (presumably deliberately introduced) to keep things a little less open-ended. And yes, retaining moisture seems like it would be a huge problem, though if rooted in a glacier I'd think they might have a chance of preserving water balance. But I don't actually know if any plants can endure very low pressure conditions like this; I found a cite that vegetables can survive brief vacuum. [33] Wnt (talk) 07:08, 2 January 2013 (UTC)

Boiling point can not be lower than melting point. Martian conditions are close to the triple point of water, but, taking into account the low partial pressure of water vapor in the martian atmosphere, any melted water will likely start boiling almost immediately. Ruslik_Zero 07:27, 2 January 2013 (UTC)

Lower than local melting point, no. Lower than 'sea level earth melting point, of course it can. The triple point on Mars has to be different than the triple point on earth. That's how science works. Evanh2008 ^{(talk|contribs)} 07:47, 2 January 2013 (UTC)

First, the melting point of water lowers with rising pressure. Second, the triple point is a characteristic of water only, not ambient conditions. The phase diagram of water is same everywhere in the Universe. Ruslik_Zero 08:05, 2 January 2013 (UTC)

You seem to be confusing the concept of the triple point with the temperature at which thermodynamic equilibrium between the phases occurs. On Earth the temperature needs to be about 273 K. I'm not about to compute what it is on Mars, but it has little to do with the fact that water under a six-millibar (.1771 inches Hg) atmosphere will boil at -5 C, give or take a bit. Everyone is welcome to break out a calculator and check for themselves. Evanh2008 ^{(talk|contribs)} 08:21, 2 January 2013 (UTC)

Okay, I see what you mean now; my numbers were off. In theory the boiling point is around -41 C, but you're right about the triple point. I guess there is no true boiling on Mars then? Just sublimation? Evanh2008 ^{(talk|contribs)} 08:41, 2 January 2013 (UTC)

You're forgetting plants still need oxygen as well. Yes, I know (most) plants produce an excess of oxygen, but when not actively photosynthesising (ie in the dark) they need oxygen for respiration just as much as humans do. So just having the right partial pressure of carbon dioxide isn't enough. I guess you could just keep them in constant light, but I don't know what effects that would have. Fgf10 (talk) 11:41, 2 January 2013 (UTC)

Well, I was assuming that whenever they were in the dark they'd need to be frozen/inactive anyway. In theory I suppose they could store redox potential in some other form than oxygen. Wnt (talk) 15:32, 2 January 2013 (UTC)

At what distance from our sun would Sirius and the sun have the same brightness?

Pluto? The Oort Cloud? How many AUs? Thanks.Rich (talk) 04:51, 2 January 2013 (UTC)

The absolute magnitude of the Sun is 4.83, of Sirius—1.42. They will have the same brightness if the ration of distances to them from an observer is 10^{(4.83-1.42)/5}=4.81. The distance to Sirius is 2.6 pc. So this translates to the distance from the Sun of about 2.6/5.81=0.45 pc or about 90,000 AU. Ruslik_Zero 07:57, 2 January 2013 (UTC)

Which translates to beyond or near the presumed outer reaches of the outer Oort cloud (depending on how you define its extent). — Quondum 08:44, 2 January 2013 (UTC)

That calculation elided that the brightness goes down as the square of distance and the absolute brightness is got by multiplying by 0.4. Half of 0.4 is 0.2 which is 1/5. Dmcq (talk) 13:09, 2 January 2013 (UTC)

Physics and chemistry questions

I have a number of questions which are not being answered neither by my seniors nor my teachers. However, some of them are easy .It is better to ask some of them at one time instead of one by one.

1. Why do like charges repel each other and unlike charges attract each other ?
2. Why does water boil at a lower temperature at high altitudes ?
3. Why does cooking anything in water take longer time on mountain top than at sea level ?
4. When we twist our fingers, it produces sound. Why is it so ? Is there any suitable word instead of "twist" ?
5. Chemical formula of copper sulfate pentahydrate is "CuSO4·5H2O". What does ·5H2O represent ? Is it correct to say · as dot ?
   

Sorry, I have asked too much. BTW Thank you and Happy New Year. Want to be Einstein (talk) 07:31, 2 January 2013 (UTC)

1) I'm not sure that we really know why, it's just a fundamental observation that they do. It might be explained in terms of quantum mechanics, string theory, and such, but ultimately you still come to a point where we say "it's that way just because it is".

3) Since water boils at a lower temperature, that keeps the water at that lower temperature, assuming the steam is free to boil off (so not in a pressure cooker, say). It takes longer to cook things at a lower temperature, and, if the temperature is too low, it may never cook.

4) Do you mean cracking knuckles ? I believe that's caused by cavitation.

5) That means it has 5 water molecules loosely bound to the central molecule. Others can add details and how you say it. StuRat (talk) 07:47, 2 January 2013 (UTC)

Regarding item 2, Boiling point explains that the boiling point varies depending on the atmospheric pressure. The lower the pressure, the lower the boiling point. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:22, 2 January 2013 (UTC)

The "like repels like" thing with charges isn't something we have an answer for - all we know is that this is what happens. There are many situations in science where we have complete knowledge of how things behave without any understanding of why. About the best we can come up with is the Weak Anthropic Principle - which basically says that if the universe worked the other way around, then (presumably) atoms would not have formed and therefore there would be no stars, planets, people, Wikipedias and Wikipedia Science Reference Desks. Hence, only those universes where physics work the way our universe does will have people around to ask the question. It's an unsatisfying answer - but it's really all we have.

Water boils at the temperature at which the vapor pressure of steam equals or exceeds that of the air above the surface. At high altitudes, the air pressure is lower, so the vapor pressure of the steam can be lower - which happens at lower temperatures. Since cooking is mostly about getting the food up to some desired temperature, most things cook more slowly at high altitudes. Contrast this with a pressure cooker which deliberately increases the pressure inside the pot to allow the water inside to reach higher temperatures without boiling so that foods cook more quickly than they otherwise would. SteveBaker (talk) 14:38, 2 January 2013 (UTC)

I would quibble with StuRat's answer to #5, in that while water of crystallization includes water which is loosely bound (coordinated) to a central atom, this may be written (if the structure is known) in a different notation, e.g. Rhodium (III) chloride = RhCl₃(H₂O)_n. Sometimes waters not directly bound to the central atom nonetheless turn up in a structure, as with the [Cu(H₂O)₄]SO₄·H₂O mentioned in the article; but all are included when written generically in the dot notation the questioner used. There's a bit of inconsistency in the article regarding Glauber's salt - our article says only 8 of the 10 waters are directly bound, but the water of crystallization article writes it as if all 10 are. Anyway, my point is that if you look at the crystal structure the waters aren't always clearly associated with one particular molecule; it can be more like an aqueous solution that has simply become concentrated enough to take on a crystalline solidity. Wnt (talk) 15:29, 2 January 2013 (UTC)

I read this in "Microsoft Student with Encarta Premium 2007"
In one example of the electromagnetic force, two electrons repel each other because they both have negative electric charges. One electron releases a photon, and the other electron absorbs it. Even though photons have no mass, their energy gives them momentum, a property that enables them to affect other particles. The momentum of the photon pushes the two electrons apart, just as the momentum of a basketball tossed between two ice skaters will push the skaters apart.
This explains why like charges repel each other. I searched whole encyclopedia but it does not provide any information about unlike charges. Is this explanation correct ? Answer to Q.4 given by StuRat mean same as what I thought. One more thing I want to know is that Is it harmful to crack knuckles ? Want to be Einstein (talk) 16:07, 2 January 2013 (UTC)

Cracking knuckles is not harmful as far as we know yet, according to Cracking knuckles#Effects, except that "habitual knuckle-crackers were more likely to have hand swelling and lowered grip strength", which doesn't address which is cause and which is effect. From the article: "it remains unclear if knuckle cracking is in itself associated with any impaired hand function." Duoduoduo (talk) 17:52, 2 January 2013 (UTC)

With regard to the electromagnetic force question, the photon is the force carrier, a virtual particle exchanged in an exceedingly short period of time, which causes repulsion between like charges. The phenomenon is the same where attraction is concerned, in that photons are exchanged - it's just not as easy to describe intuitively as the basketball analogy does for repulsion. It is important to remember that the virtual particle model is just an interpretation of what happens, and although it gives correct results under enough conditions to be useful, it is only one possible way of looking at it, and has its limitations. 72.128.82.131 (talk) 18:27, 2 January 2013 (UTC)

Professional engineers

Are professional engineers used in any aspect of film production directly or indirectly? In which areas? 176.27.208.210 (talk) 11:20, 2 January 2013 (UTC)

Certifying the building drawings of the buildings (which are used in filming, as they house sets) on the studio lots. 67.163.109.173 (talk) 11:39, 2 January 2013 (UTC)

There are many different kinds of engineer, but see film crew and particularly sound engineer.--Shantavira|^{feed me} 12:10, 2 January 2013 (UTC)

Any movie with computer graphics (which these days is almost any movie!) is likely to have a bunch of professional software engineers working for them in various capacities. SteveBaker (talk) 14:16, 2 January 2013 (UTC)

We have an article, Professional engineer, which explains that in some countries like the United States, there are engineers who are licensed by the state or other government unit, and are allowed to plan projects that could impact public safety, such as electrical wiring in larger buildings, the structure of buildings, water systems, etc. This kind of licensure would not be needed for those aspects of film production that helps to make the film pleasing to the audience. Jc3s5h (talk) 14:31, 2 January 2013 (UTC)

Ah - yes. If we're talking about licensed professional engineers - then that's a different matter. I doubt that there are many jobs in the film industry that require such a license - although it might be that the strong union rules in the film industry could require a license in some cases. The use of the term "professional engineer" to denote someone in one of those niche engineering jobs that requires a state license is really annoying! I'm an engineer - and I get paid to do it - so I'm definitely a professional. So why can't I call myself a "professional engineer"? Weird! SteveBaker (talk) 14:48, 2 January 2013 (UTC)

Logic

Isnt everything logical, even creativity? I agree that being logical inhibits creativity as creativity requires thinking beyond things we already understand but the end product of creativity is logical. 176.250.156.24 (talk) 15:38, 2 January 2013 (UTC)

How does serendipity fit into your argument? — Preceding unsigned comment added by 217.158.236.14 (talk) 15:56, 2 January 2013 (UTC)

Serendipity is perfectly logical. There's always a probability that an event which is happy for some people will occur. 176.250.156.24 (talk) 18:18, 2 January 2013 (UTC)

People (and many of their beliefs and actions) are not logical, as Spock liked to remind us.--Shantavira|^{feed me} 16:04, 2 January 2013 (UTC)

Thats because people aren't perfect. We act based on emotion and our beliefs are formed by past experiences, and possibly genetics. Sounds logical to me. 176.250.156.24 (talk) 18:18, 2 January 2013 (UTC)

nicotine inhaler

I remember back in the 1990s I used to see commercials for a nicotine inhaler that was for quitting smoking and a alternative to patches and gum. This was available over-the-counter. This was a different thing than the E-cig. I don't believe it was electronic. Now all of a sudden it seems to have disappeared from the marketplace in the United States, what happened to it?--Jonharley667 (talk) 17:22, 2 January 2013 (UTC)

The NICORETTE® Inhalator is still available in the UK, but I haven't seen anybody using one for years. The only US product that I could find (after a very quick search) was the NICOTROL Inhaler which is "Prescription-Only". Alansplodge (talk) 17:32, 2 January 2013 (UTC)