Wikipedia:Reference desk/Archives/Science/2009 January 1

= January 1 =

Date
What year is it? ~ R . T . G  12:42, 1 January 2009 (UTC)


 * I'm pretty sure it's 2009 everywhere at this point. In the Gregorian calendar, of course. --98.217.8.46 (talk) 12:54, 1 January 2009 (UTC)

No time machine available in this age, sorry. This is year 2009; you better live with it... What year were you coming from?--PMajer (talk) 13:42, 1 January 2009 (UTC)
 * it's still the year of the rat until 1/26/2009 when the ox takes over --76.125.8.141 (talk) 16:47, 1 January 2009 (UTC)


 * It's also Year Heisei 21, in emperor era counting. Nimur (talk) 16:57, 1 January 2009 (UTC)


 * Take your pick, see year and list of calendars. I'd go for the 2008–2009 fiscal year. Also for date see date. Dmcq (talk) 22:31, 1 January 2009 (UTC)


 * @ Nimur wouldn't it still be Heisei 20 till the New Year somewhen in spring? Or do they use the Gregorian year for the era counting?76.97.245.5 (talk) 01:01, 2 January 2009 (UTC)
 * According to Japanese era name, and this citation: "In historical practice, the first day of a nengō (元年, gannen?) starts whenever the emperor chooses; and the first year continues until the next lunar new year, which is understood to be the start of the nengō's second year." I'm not actually familiar with the specifics but I can ask some Japanese colleagues and report back.  Nimur (talk) 16:59, 2 January 2009 (UTC)

An optional use for leeches?
A was looking at some stupid stars advocating leeches as detoxifier (pfff). Anywayit got me mind rolling in a sort of similar direction, could those blood sucking MOFOs be used in conjunction with a diet? I would imagine that there are strick homeostatic processes that keep the volume of blood and number of cells constant, so if blood was removed energy would need to be dissipated to restore balance. Does this theoretically make sense?78.133.19.131 (talk) 13:00, 1 January 2009 (UTC)


 * Cut the leeches out and just ask if moderated blood loss could be a way to diet. I suspect the replenishment of a small amount of blood is not a huge caloric drain but I'm sure someone can answer for sure. --98.217.8.46 (talk) 14:05, 1 January 2009 (UTC)


 * I'd say yes, except for the usual problem that your body will detect that it's losing weight, think you're starving to death, then decrease your metabolic rate and increase your hunger tenfold, making you actually gain weight. Also, you'd need supplements to ensure that you're replacing everything which is lost with blood, such as iron. StuRat (talk) 15:50, 1 January 2009 (UTC)


 * Here is a British Medical Bulletin on metabolic rate changes as a result of injury (I'm not sure if controlled bloodletting counts as injury). It may provide some insight on the complex effects that StuRat mentioned.  Nimur (talk) 17:02, 1 January 2009 (UTC)


 * Leeches have been used for curing diseases like paralysis with (supposedly good success) in Kerala, a southern state of India. Have a look at this and this and search for 'leech' - WikiCheng | Talk 03:53, 2 January 2009 (UTC)


 * That is totally unrelated to the question being asked. --98.217.8.46 (talk) 04:36, 2 January 2009 (UTC)


 * "blood sucking MOFOs"? Come now, let's avoid stereotypes. —Tamfang (talk) 19:14, 5 January 2009 (UTC)

This rings my bullshit detector Wiki Cheng Bastard Soap (talk) 11:23, 2 January 2009 (UTC)


 * It certainly does! The amount of blood you could lose without all sorts of other health problems (such as aneamia) is pretty small - the blood donation people say that you can safely lose (and recover) only about a half-liter every month.  The energy required to do that is tough to estimate - but it doesn't seem like it would be very significant.  No - I think you should stick to using leeches for storm prediction. SteveBaker (talk) 14:30, 2 January 2009 (UTC)


 * The Mayo Clinic web site asserts that you 'burn' about 650 calories when you donate a unit of blood: . While most jurisdictions limit donors to one unit every eight weeks, that restriction has a margin for safety built into it.  If we assume blood loss at twice the permitted rate, that runs about 160 calories per week, or about 20 calories per day.  It's a trivial reduction that would probably be wasted.  (You're going to be hungrier than usual every time your body notices it's short on blood.)  You'd save about the same number of calories by switching from cream to milk in one cup of coffee each day, or by taking your tea with one lump of sugar instead of two. TenOfAllTrades(talk) 15:24, 2 January 2009 (UTC)

I know someone who contracted giardiasis, then deliberately didn't get treated, to assist with dieting. I've heard of people use a similar trick with tapeworms. Medical advice: I wouldn't recommend any of these methods. Axl ¤  [Talk]  09:59, 3 January 2009 (UTC)
 * Tapeworms work by consuming food in your gut before you have a chance to absorb it. However, that just makes you more hungry and causes you to eat more - so they may not help as much as you'd hope.   If you have the mental strength not to eat more as the tapeworms consume your food - then you'd probably have no problem sticking to a medically more reasonable diet.  Dunno about giardiasis - but the list of symptoms described in our article suggests that it's not going to replace the South Beach diet anytime soon! SteveBaker (talk) 13:26, 3 January 2009 (UTC)

do the congenitally blind understand literary descriptions?
There are some things I read, for example colors I don't know the names of, even vaguely (Carmine? Puce? Bimini?), where I don't know what they're talking abut. But do the congenitally blind understand most visual descriptions? Do they know the same thing everyone else does, like what a mirror is, etc, or are these things like these weird colors are for me? —Preceding unsigned comment added by 79.122.79.41 (talk) 21:31, 1 January 2009 (UTC)
 * They understand as it is described to them only. This reminds me of Thomas Nagel's essay "What is it like to be a bat?" where he talks about the subjective nature of consciousness.  Can you conceive of a bat's perception through echolocation? --  JSBillings  23:43, 1 January 2009 (UTC)
 * This is speculation but I would imagine that over time they pick up what visual based description might connote based on sighted people's reactions to them, although they cannot directly relate to it. If there is a gap in their knowledge about the appearance of something, they may miss an important visual indicator that would be apparent to sighted people. An example would be "the baseball player's shadows were long when they arrived at the field." This description would immediately indicate it a morning or evening setting, but a blind person who hasn't realized shadows change length over the course of the day will miss the time detail. If they were careful, they would ask themselves "what was the point about the shadows" and ask someone what it means. Something more difficult might be a description about a woman wearing a red dress to a party which would signal to a sighted person that she was trying to be seductive compared to say, the same woman wearing the same dress in blue. A blind person would probably realize that a red dress often indicates seductiveness only after connecting that detail with other description and then encountering the same literary red=seductiveness theme repeatedly. I would also imagine that the reverse hold true in that sighted people miss details that blind people would pick up on. A description about a blind person whistling a monotone as they walk through a doorway would not indicate to a sighted person that they were probably trying to get a feel for the size of the room by listening for the reverberations of the sound. (or something like that...) 152.16.15.23 (talk) 00:29, 2 January 2009 (UTC)


 * As this article shows they sometimes can't make sense of the image even if they can see again.  A blind acquaintance of mine said he got a much clearer idea about what an optical illusion was after someone had shown him a relief of the Necker Cube.76.97.245.5 (talk) 00:37, 2 January 2009 (UTC)


 * I came to different conclusions about the examples given. Red would be quite easy to associate with fire and then seductiveness. Shadows can be directly perceived by the heat of the sun. And going into a room I think they'd probably make a click or pip noise rather than a continuous tone to determine its overall size, it certainly works better for me. Interestingly on the last if it's quiet I seem to be able to hear which way a hall goes with my eyes closed quite easily even without making any noise. Dmcq (talk) 12:25, 2 January 2009 (UTC)

Also just as a note - A lot of blind people aren't walking around in total darkness (i.e. seeing nothing), but rather there are a wide degrees of what the blind can 'see' (changes in light, silhouettes etc.) - it really depends on the individual. 194.221.133.226 (talk) 10:36, 2 January 2009 (UTC)


 * I was told, ages ago now, by a cognitive scientist that it depends very much on the nature of the blindness. If it is due to "mere" problems with the eyes then the blind person thought in visual and spatial metaphors just the same as a sighted one (though clearly certain concepts like colors were going to be problematic). If it was due to a problem with the visual cortex of the brain, then the ability to visualize things in their head (and their understanding of visual metaphors) would also be affected. --98.217.8.46 (talk) 03:14, 3 January 2009 (UTC)

Mechanical device that keeps something spinning in exactly the right speed
Here's something I've been wondering since I was a wee lad (well, teenager, at least). I've asked a number of people this over the years (though obviously no engineer), but never gotten the answer. I've finally decided to find out the answer, once and for all, with the help of you fine refdeskers.

An old-timey mechanical wind-up clock works on this principle: you wind up a spring until there's lots and lots of tension in that spring. That tension is slowly released to the various cogs and gears inside the clock, and finally transmitted to the dials on the face of the clock. But here's my question: the spring can be wound with various degrees of tension, but the clock still goes at the same rate. If you wind the spring to half its capacity, the gears in the clock should only go at half the speed as if the spring was wound to full capacity (this is Hooke's law, no?) And yet, the dials on the face always moves at constant speed, regarless of how much tension there is in the spring. There must be some mechanical device doing this.

The reason I keep wondering about this is that there's all sorts of machines that seems to be using this same device, and whenever I see them, I wonder once more. Old movie cameras, for instance, were powered by springs or a hand-crank, yet regardless of how much tension there is in the spring or how fast you rotate the crank, the camera has to rotate the shutter and feed the film-stock at exactly 24 frames per second. Same thing with hand-cranked record players, they always have to move with the same rpm.

So, what is this magical mechanical device? How does it work? The only thing I can think of is that there somehow is something that applies a smaller counteracting force to the gears that is just big enough to ensure that they always rotate at the same speed, but increase and decrease at the same rate as the main gear (so if the tension in the spring doubles, the counter-acting force doubles too, but the difference between it and the main gear is constant), but I can't quite work out the details. Is that how it works? Do we have an article on how this device? Does it have a name?

I'd be most grateful for any answer, as I said, this has been bugging me for two decades, at least. Belisarius (talk) 23:25, 1 January 2009 (UTC)


 * Older mechanical clocks used a Fusee, which was later replaced by improvements in technology such as the Pendulum clock and Escapement. Clocks are pretty neat, you can make a fairly reliable pendulum clock out of tinker toys if you want.  The articles I mentioned are actually very interesting reads, if you've been curious about this for a while.  --  JSBillings  23:33, 1 January 2009 (UTC)


 * An interesting device (a bit off point) is the centrifugal governor ...used in a spring-loaded record player and a spring-loaded telephone dial to limit the speed.  hydnjo talk 23:58, 1 January 2009 (UTC)


 * In clocks the wound spring is used as an energy store to power the clock, but not to govern its speed, (various other aforementioned mechanisms are used for that) and so the tension in the spring (until it approaches zero) has no affect on the speed at which the clocks mechanism ticks over. —Preceding unsigned comment added by 92.16.196.156 (talk) 00:10, 2 January 2009 (UTC)


 * For a rotating machine, Centrifugal governor is exactly right. For a time piece, you might look up Balance wheel and Pendulum.--GreenSpigot (talk) 02:28, 2 January 2009 (UTC)
 * Some devices like clocks had an escapement, which went tick-tock, and used a limited amount of energy for each incremental movement of a clock or watch. Other windup devices used a Centrifugal governor or flyball governor, similar to the one used on some earlier steamengines, to regulate or limite the speed. On a windup phonograph there was no intermittent escapement like on a watch, but a continuous rotation at a desired speed. If the speed tended to increase, as when the spring was wound tightly, the spinning caused the flyballs to move farther out and bend the springs to which they were attached, causing movement of the ring attached to tone end of the springs, and applying greater pressure to a braking mechanism, reducing the speed. On Watt's steam engine, the flyballs rotated about a vertical axis and governed the steam flow. On windup phonographs, the axis might be horizontal, and spring pressure rather than gravity was usually the force the centrifugal force of the balls worked against. The flyball governor worked well to prevent the fully wound spring from running the phonograph faster than was desired, but when the spring was nearly run down, it had used up all its range of regulation and could not prevent the mechanism from running slower and slower until it ground to a halt. Edison (talk) 06:03, 2 January 2009 (UTC)


 * The simplest governor to understand is a pendulum clock. At it's simplest:
 * The spring is attached to the gear wheel.
 * A lever arm with a single triangular tooth on each end is wedged into the gear to stop it rotating.
 * A pendulum swings back and forth.
 * At the end of the pendulum's travel it pushes on the lever arm - letting it up just enough for the tooth on one end to disengage from the gear while the tooth on the other end engages and grabs the next tooth in the gearwheel. This allows the wheel to turn by exactly one tooth for every swing of the pendulum.
 * The gear wheel also drives the hands of the clock through successive reduction gears to get hours, minutes and seconds (and perhaps days, months, etc in fancy clocks).
 * In the process of doing that, the gear wheel's rotation applies a small, fixed amount of energy to the pendulum to keep it swinging.
 * Since the period of a pendulum swing depends on its length and not on how hard you push it, the pendulum swings at the same rate no matter how much energy is in the spring.
 * This limits the amount of energy the spring can release for each swing of the pendulum - so the clock runs at the same speed until there is insufficient energy in the spring to keep the pendulum swinging against the forces of friction and air resistance.
 * In most long-case 'grandfather' clocks, the pendulum is set up to swing once a second because that makes a pleasing 'heartbeat' and makes the subsequent gearing that drives the hands of the clock a little bit simpler. The repeated release-and-grab cycle of the spring-driven gearwheel is what makes the characteristic ticking sound you hear in most mechanical clocks.  There is generally a small adjustment you can make to the weight on the end of the pendulum to adjust the length - and hence to make the clock tick faster or slower.
 * Clocks that chime generally have another spring mechanism for doing that which is held in check with another lever arm that's tripped when a tooth on a wheel attached to the minute hand reaches the top of the hour (or whatever).
 * My long-case clock has a 30 day movement - you wind up TWO springs - one for the chimes and one for the hands. On my clock, the chime mechanism actually runs down after about three weeks - but the hands run for well over 30 days - which is a pretty amazing thing for such primitive engineering and a 100 year old mechanism.
 * On mechanical wristwatches, the pendulum is replaced by a wheel that is spun back and forth by a 'hair spring' - replacing the force of gravity with a spring force - but the principle is the same. SteveBaker (talk) 14:12, 2 January 2009 (UTC)