Wikipedia:Reference desk/Archives/Science/2006 December 24

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December 24

Observation whilst feeding the gulls...

I was giving the gulls their lunch today and I noticed another odd behaviour pattern (actually, it's something they usually do but I've never really thought much about it). The (small) black-headed gulls often see the pile of food first, yet flutter around in the air above, or perch nearby for several minutes. No bird seems to want to be the first one down to eat. The (large) herring gulls and great black-backed gulls have no qualms about hanging back and dive down to stuff their faces as soon as they become aware of the food.

At this point, the BH gulls see their larger relatives eating and descend en masse to join in. They usually don't end up with much of a feed and get pecked at and chased quite a bit. I've tried to figure this in my head - do you think the black-heads, being much smaller and more vulnerable on the ground are waiting for the big gulls to land before they decide to eat, figuring that the bigger, stronger, more aggressive birds will protect them from any passing predator? In a way, it seems counterproductive - less food and more aggro, especially considering that there are very few predators of gulls in an urban environment. Opinions? Anyone else noticed them doing this? --Kurt Shaped Box 01:37, 24 December 2006 (UTC)

Sounds to me like the smaller gulls are simply being considerate of their larger brethren. A couple points:

1. A bigger gull needs to eat more per day to stay alive; I wouldn't assume that it's beyond a small gull to know this and act accordingly, waiting to snack on little crumbs.
2. No doubt a tacit pecking order has been established, and if a small gull were to violate it, it would be on the receiving end of some 'social pressure'.

——Vranak→

Thanks for your answers, folks. Does anyone know how much your average 'large white headed gull' eats per day in the wild? I know from personal observation that they can eat about the same amount as a human in one sitting (then they go off to rest, digest and take a nap). I'm not sure if they eat as often as we do if given the opportunity. --Kurt Shaped Box 10:06, 24 December 2006 (UTC)

I'm interested in what gulls eat, period. I mean, I'm sure it has it all listed in the gulls article, but I can never discern what it is they peck off the ground. --Vranak 19:10, 24 December 2006 (UTC)

I usually feed my local gulls cooked meat, bread, cheese or whatever kitchen scraps I have lying around most lunchtimes. I cut/break it all into smallish pieces, bag it, then tip it into a pile in my garden. Gulls have their preferences but will eat just about anything organic if they're hungry enough. They'll kill for food if they have to but they usually just scavenge. --Kurt Shaped Box 22:31, 24 December 2006 (UTC)

Maybe the small gulls don't have as keen of a sense of smell so rely on the big gulls to tell them if the food is safe to eat. If the big gulls eat it, then they know it's fine for them to eat, too. StuRat 04:46, 24 December 2006 (UTC)

I think it's more likely dominance/submission behaviour. Anchoress 05:22, 24 December 2006 (UTC)

It may be an order of feeding based on strength or fear of harm, but that does not explain the smaller birds actually waiting until the larger, stronger birds appear. Nor does it explain why the smaller birds then come down to feed while the large ones are still there. A clue might be found in the fact that these birds are all in the role of scavenger, as opposed to hunter. When hunting they can select the type of food which they are suited to catch, kill and ingest, i.e. appropriate to their strength and abilities. When scavenging they have to take whatever there is. In this situation, if they perceive the food as too large to break up into small edible pieces, they may simply be waiting for larger birds with the ability to tear off the skin of a dead fish, or slit open its body, before taking what they are capable of from the left overs, i.e. this may be the only way for them to get at the meat inside. This determinant of feeding order (or lack of it) has been described for a mixture of sea and land based birds feeding on carrion and seems to be valid in the case of vultures specialised for eating specific parts of a dead animal (I enjoyed the bit in the first article on how a bird was more interested in defending his territory than in actually eating the fish). The crucial point of such an explanation is how the birds perceive the food, i.e. do they think they are capable of successfully breaking up the food into eatable pieces. This theory may possibly be assessed by lumping similar food all together in a large piece, or spreading it out as small bits, and comparing behaviour. --Seejyb 11:30, 24 December 2006 (UTC)

Gulls do have this huge personality flaw (I'm not sure what the more scientific amongst us would call it) when it comes to considering it more important to strut around with chest puffed out, defending a pile of food from the other gulls than actually eating it themselves. Invariably, the lone 'dick waving' bird gets overwhelmed by sheer weight of numbers and ends up being pecked and jostled out of the way, often ending up with no food at all. There's also the 'must steal food from another gull' mindset. One bird picks up a piece of meat and flies away with it, at which point the majority of the other gulls give chase, leaving behind the rest of the food for the two or three birds that hung back to eat at their leisure - whilst the others flap, squawk and squabble in the air above. --Kurt Shaped Box 22:43, 24 December 2006 (UTC)

Gulls aren't the only ones with this defect. Watch kids get jealous of each other's Xmas presents; they show no interest in the toy until the other kid does, then they all of a sudden have to have it, LOL. StuRat 12:11, 25 December 2006 (UTC)

I suppose it makes sense to fight for every scrap in their natural environment when food/desired objects are scarce - I guess that it's a survival instinct built into most living things. If another of your kind possesses something (be it food, nesting material, or a toy), then it must be of value for survival and therefore it would be advantageous to possess that thing yourself. However, some gulls have definitely figured out that in an urban environment, where the food supply is plentiful and almost 100% assured, that they don't need to do this - and that it's actually beneficial to let the 'sheep' do their thing and nip in when they're distracted. I guess it just comes down to individual intelligence and life experience. --Kurt Shaped Box 23:58, 25 December 2006 (UTC)

Several plausible answers have been offered already, so I'd just like to mention my personal guess: the smaller gulls are simply waiting until the big ones are distracted by the food before diving in and attempting to snatch their share. If they went in and started eating while the bigger gulls were still circling, they'd be easy and conspicuous targets for attacks from above, and would probably get more than just "pecked at and chased quite a bit". This is not a trivial risk for them — herring gulls can and do occasionally kill black-headed gulls.

Put it this way: if you had to share your meal with a hungry tiger, wouldn't you want to wait until the tiger was busy eating before trying to take your share? —Ilmari Karonen (talk) 02:50, 28 December 2006 (UTC)

Good point. As a matter of interest, do the gulls kill each other in fights over food and territory, or is it a case of a larger gull killing a smaller gull for food? Whenever I've seen gulls confronting each other, it's mostly bluster and posturing, with the occasional plucked feather and drop of drawn blood. Seems to be more like duelling for status (or whatever) than an intent to kill and maim - it stops when one bird backs down. --Kurt Shaped Box 03:06, 28 December 2006 (UTC)

The only cases I've personally witnessed have involved smaller gulls building their nest too close to a herring gull nest. Since the smaller gulls haven't been willing to abandon their nest after the eggs have already been laid (and even hatched), in spite of harrassment from their larger neighbors, the territorial conflict has sometimes continued to escalate until the larger gulls have managed to destroy the nest and the offspring, or, in some cases, kill at least one of the parents. Mind you, this is all based on a few isolated incidents I've observed. I've never seen nor heard of gulls killing other gulls for food per se, but I won't swear it could never happen. Still, I expect there is usually easier prey to be found; gulls, unlike raptors, aren't that well adapted to catching other birds in the air. —Ilmari Karonen (talk) 22:13, 28 December 2006 (UTC)

Hello, I gather You are the people I need to expose my predicament to.

Do Laughing Gulls fly with plastic bottles tied to their backs? Apparently they do and surprisingly well. An adult (we don’t know if male or female, an expert may be able to tell) member of the local flock at the beach I visit in Yucatán, México, has an empty plastic 600 ml. bottle (like those used for drinking water) tied to its back with a fishing cord. The bottle is few inches shorter than the gull’s body. As how and who performed the –unexplainable- act of catching the bird and securing the bottle, there are several hypotheses amongst the beach goers that have seen the animal. One thing is evident: it is not any kind of scientific experiment.

The gull seems to fly and feed normally. The flock doesn’t seem to mind the stigma the bird has been subjected to, however the bird is wary of humans. Laughing gulls will come for the usual crumb but they fly away if one tries to approach them.

The materials (the bottle and the fishing cord) were clumsily tied behind the wings and under the belly, and are madly endurable. Sometimes the bottle has water inside, which I suppose should increase in weight and make the flight more difficult.

It has been already a year since we saw it the first time. And the last post in this page is 24 December 2006. I wonder if any of you will see this before Botella -as we call it- either gets rid of the bottle or otherwise. There should be a way to help this laughing gull. Does anybody know?AlbatrosV27 (talk) 03:32, 17 October 2009 (UTC)

cognitive intelligence - name for the occurrence of role reversal between subject and object in test situation.

Definition of incident for which a name or term is being requested:

(first part)

When your research leads you to the point of discovering that you have previously been unwittingly playing the role of the subject in someone else's experiment.

(second part)

Being thus aware as to the presence of observation, the subject then embarks on behaviour directed to illicit a response from its observers, for the benefit of acquiring knowledge on them.

For example;

(first part)

A psychologist was taking turns locking different animals inside a small room. After the door was shut, he would observe the animals behaviour through the keyhole. He continued doing this and taking notes until he came to a chimpanzee. He shut the chimp in the wooden room, put his eye to the keyhole only to observe that the room now appeared dark. The chimp had put it's eye to the keyhole on the other side of the door.

• There is no name except role reversal for this contrived situation. alteripse 15:56, 24 December 2006 (UTC)

Are you asking whether there exists a name for this situation, or are you asking for suggestions for a newly-made-up term? I agree with alteripse that you're not going to find an existing name for this. The first part made me think of the famous Milgram experiment. While contrived, I vaguely remember a science fiction story that had the same premise, where the original observers were aliens.  --Lambiam^Talk 16:09, 24 December 2006 (UTC)

Niklas Luhmann's term observation of the second order (Beobachtung zweiter Ordnung) comes to mind, a relevant key to his theory on social systems. Though his definition of observation is different than common usage and mostly refers not to psychical but to social systems (such as economy or religion) which observe their environment and themselves, while also observing the observations and so forth. Observed and observer switching roles back and forth, flickering hierarchies - Douglas Hofstadter might have called it a strange loop.---Sluzzelin 00:25, 25 December 2006 (UTC)

Aged whiskey

is 50 year old whiskey ok to drink?

As long as it has been properly stored, emphatically YES. Enjoy; you are undoubtedly the subject of envy for most of the people who read this. Anchoress 05:20, 24 December 2006 (UTC)

"50 year old whiskey" might not mean what you think. Whiskey "ages" in the cask, but (unlike wine) once it's decanted into a bottle it largely doesn't. When you buy whiskey the age on the label is the time it spent in the cast - if it spent another ten years in the bottle on a shelf somewhere, it's still the same "age" it was when it was bottled. Now, if the whiskey really is labelled "50 year old" on the bottle, it's been in the cask for 50 years. I'm not aware of any major manufacturer who keeps their product in the cask remotely as long; 21 years is just about the limit. The longer the whiskey is in the barrel the stronger it gets (slightly), and the more flavour will percolate from the wood into the spirit. After 50 years the whiskey will be very heavily flavoured, and very dark in colour. I rather suspect too much so. Now if you mean some old whiskey you found, say that was 20 year old when it was bottled in 1976. That's still just 20 year old whiskey, and always will be. -- Finlay McWalter | Talk 13:35, 24 December 2006 (UTC)

Rumour has it that Johnnie Walker Blue has 50-60 year old elements to it. --jpgordon^∇∆∇∆ 18:27, 25 December 2006 (UTC)

It is not a universal constant that wood-flavoured beverages taste better than not. I recently tried a bottle of 'Naked Grape' white wine that boasted of it not being aged in oak. It was quite good. Vranak

If it's been sealed in the bottle all this time it should be fine, by which I mean not poisonous. It might not taste so good, however, but that's for you to judge. StuRat 12:06, 25 December 2006 (UTC)

Dominant genes?

I was wondering whether something such as dominant genes existed. I am doing a holiday job in Canal Walk shopping mall in Cape Town, where I see thousands of people everyday. What I have noticed, is that almost 9/10 couples which have a parent with dark hair and a parent with blonde hair and blue eyes, the children end up with the blonde hair and blue eyes. I have also seen hundreds of Europeans who have married with Asian people (mainly Japanese, Chinese and Malaysian people), who also have one parent with blonde hair and blue eyes, then the children also end up with blonde hair and blue eyes. I thought that if this was meant to go on, one day we'll all have blonde hair and blue eyes. PS: All of the Asians who I asked if they were related to these blonde children said they were. This is really something that fascinates me. Anyone with information about this? ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 07:29, 24 December 2006 (UTC)

There certainly are dominant genes and recessive genes. The genetics of human skin and eye colour are beginning to be understood by scientists (indeed, just this week a huge breakthrough was made in understanding the genetic basis of blue eyes [1]). Regarding the idea that "one day we'll all have blonde hair and blue eyes", actually quite the opposite has been proposed. Since blonde hair (and to some extent, blue eyes) are recessive to darker pigmentation, it has been suggested they will die out at some point in the future [2]. If I may offer a personal observation (and I have a PhD in pigmentation genetics, so it is informed to some extent): this is quite a strange thing for a human geneticist to propose, really, as by their very nature truly recessive genes tend not to "die out" completely unless there is a very strong selective pressure on them. I don't see men running from blondes in disgust (or indeed vice versa if the female response to the new Blonde Bond is anything to go by) Therefore, I suspect this story has been spun by the media somewhat. Rockpocket 09:43, 24 December 2006 (UTC)

This article mentions the fact that many human have hair that grows darker as they mature. Some adults that would not be called "blond" were "blond" as children. --JWSchmidt 01:08, 25 December 2006 (UTC)

Me, for example. I am now starting to get blackish hair and was fairly blonde as a kid. In any case, hair pigmentation is fairly complex (skin pigmentation is dead simple by comparison, and that is nowhere cut-and-dried). Eye color is not that complicated, but it is more complex than long thought (green/blue eyes recessive vs brown eyes) and it is liked to hair color, and to some extent to skin color also. The latter may be an artifact of lineage sorting in ancestral populations (meaning that some combination of traits became predominant or more common in the population, such as fair skin and red hair in Ireland), but the former IIRC is genetically linked to some degree - red-haired people with naturally tan skin are occasionally found, but red-haired people with dark brown eyes are very very rare. That blondes usually have eyes not darker than hazel is an artifact of an overall low pigmentation, although this too differs in regards to different tissues - blondes with black body hair are not that rare. Dysmorodrepanis 04:35, 28 December 2006 (UTC)

The genetic link between red hair, pale skin and freckling is largely explained by variation in MC1R and its effect on phaeomelanin production. The reason both blondes and dark haired people will usually tan better than red-heads is that they both have higher eumelanin ratios (and it appears the structure of the eumelanin polymers differ between dark and blonde haired individuals). Rockpocket 07:26, 28 December 2006 (UTC)

monoline roots

sir/madam, I am interested to know more about monopoline roots.I been told that these are used to cure aids/hiv.I request resourceful persons to provide some more light on the topic . thanx, ajay jain <email address removed for security>

Many things are "said" or sold to cure or prevent AIDS. Mistrust anyone who wants to sell you something for which there is no evidence of efficacy. There are degrees of evidence, and no evidence of a reliable degree supports use of these roots for these purposes. alteripse 15:53, 24 December 2006 (UTC)

I can't find any information on the Web on "monopoline", except that another name is kanamrutakadugandha. I can't find any information on kanamrutakadugandha, except that another name is "monopoline roots". Most pages are about people asking what it is, or where they can buy it, or others trying to sell it. If there had been any research into whatever this is, there would have been at least some information somewhere. The use of untested drugs of unknown composition and strength can be dangerous to your health.  --Lambiam^Talk 23:45, 24 December 2006 (UTC)

Perfect Hurricane

Reading the article on the Great Storm of 1703, I noticed the term "Perfect Hurricane." What is it's meaning? Crisco 1492 10:05, 24 December 2006 (UTC)

It means a textbook example of a hurricane, including features like a well defined eye and eye-wall, symmetrical arms/feeder bands, etc. See perfect storm for the source of the term. StuRat 11:41, 25 December 2006 (UTC)

Squeeze Those LEDSs!

I have some LEDs to use that have a rated current of 300mA but a surge current of 3mA - can this surge current be exploited to acheive greater light intensity without damaging the LED? --Username132 (talk) 10:58, 24 December 2006 (UTC)

Surge current is 3A right (you wrote 3mA)?

Probably not continously - clearly something that works well at 300mA will still last for a long time at 310mA - the higher you go the more likely the thing will 'blow' - the life is shortened. However you could try pulsing to a higher current - if you have a suitable circuit - for instance at 1km 3A on 1/10sec of a second is more noticable than 3mA continuous - I can't say that doing this won't shorten the life of the bulb though. If the average current exceeds the rated continuous current the thing will start to overheat..87.102.4.126 11:39, 24 December 2006 (UTC)

FYI, when you overheat an LED they tend to explode, POP, little shards of plastic flying everywhere--71.247.120.5 12:36, 24 December 2006 (UTC)

Huh? No way. I overheated lots of LEDs and the worst that happened was that the inside turned brown and the thing heated up and melted. No explosion. Nothing. You generally don't have to worry about overloading an LED unless you're in a room full of nitrogen triiodide. Ilikefood 23:48, 25 December 2006 (UTC)

If you apply a surge at just the right voltage they'll pop instead of browning out--71.247.120.5 00:17, 26 December 2006 (UTC)

In the 1970s, Hewlett-Packard reported (in an article in HP Journal about the design of the HP-35 calculator) that an LED repeatedly pulsed very briefly appeared brighter to the human eye than an LED carrying a continuous current with the same average value. For this reason, they chose to multiplex the 15 digit display of the HP35 one LED segment at a time rather than the more-usual one digit at a time. (The energy was stored in inductors and then dumped into the LEDs.) I don't remember whether they cited a reason for this effect and I certainly don't know if it's still true with modern LEDs, but it might be one reason to consider exploiting the surge-current rating of an LED.

Atlant 14:58, 26 December 2006 (UTC)

This may be related to the Broca-Sulzer effect, which can cause a brief flash of light to appear brighter (or dimmer) than a longer one. We don't seem to have an article on it, but you can read a brief description here. (While Googling for it, I also found this recent paper, which describes an interesting related phenomenon.) —Ilmari Karonen (talk) 03:30, 28 December 2006 (UTC)

Thanks for that reference!

Atlant 12:27, 28 December 2006 (UTC)

One Device. One Non-rotating Speaker. 360 Degrees

I want sound from a single speaker to be effectively spread over 360 degrees without rotating it. I figure if the speaker is directed towards an appropriately designed surface, sound will be directed in all directions. It doesn't need to carry far - 60+ m radius is fine. Eighty or so desicbels at source. --Username132 (talk) 11:10, 24 December 2006 (UTC)

The hi-fi world is full of these - 'fire' your sound device up or down onto a conical or similar surface - http://www.fcsurplus.ca/shopping/shopexd.asp?id=1525 is this picture you can see the cone, the speaker is above the cone. The sound reflection cone is supposed to be hard and rigid - to get good sound reflection. As for the volume - I think horn speakers get quite loud - (the sort that garble the announcements at train stations (in the UK at least)87.102.4.126 11:45, 24 December 2006 (UTC)

I would second the upward or downward speaker pointing at the outside surface of a cone on the speaker axis. Some commercial systems use this method.--Light current 19:42, 24 December 2006 (UTC)

Also see the description of the "Walsh" transducer at Loudspeaker#Conical bending wave transducers.

Atlant 15:03, 26 December 2006 (UTC)

Reading in the Dark

Is it really bad for you? If so, why? Sashafklein 11:33, 24 December 2006 (UTC)

If you feel like your eyes are straining, or you're getting a headache, it's definitely a bad idea. It's a matter of personal sensitivites though. I sometimes read by a single candle without much trouble, though not for more than ten minutes at a time. --Vranak 19:05, 24 December 2006 (UTC)

This is a folk medicine concept, and likely bogus. There is no evidence and it makes no sense that using your eyes in dim light harms them. alteripse 19:16, 24 December 2006 (UTC)

It does open up your irises though and maybe your depth of field and focussing ability is reduced. I know mine is.--Light current 19:45, 24 December 2006 (UTC)

I remember reading a couple of years ago a science news article reporting on research in which the hypothesis had been investigated. The outcome was that no significant ill effects had been found. Sorry, I have no reference for this except my memory, and I have no information about the actual content of the research – such reports by science journalists are often seriously misleading.  --Lambiam^Talk 23:55, 24 December 2006 (UTC)

Yes. i remember reading a report which finally stated that reading in dim light does not damage the eyes any more than using a camera in dim light damages the camera. But I know that to read in dim light, you need to strain your eyes a bit but may be the effect is just temporary. In any case, I believe that it is not good. whenever you need to strain your organs to do something, I believe that it may not be very good. -- WikiCheng | Talk 17:48, 25 December 2006 (UTC)

Regardless of whether you believe it, I must politely call it nonsense. You strain muscles to build muscles. You strain your brain to build your brain. In the case of reading in dim light, it is your brain that does the straining, not your eyes. alteripse 19:45, 25 December 2006 (UTC)

Yeah a bit like straining your 'ears' to hear quiet sounds does not harm them. Its not the transducer that is being strained, its the processor that is having to work harder.--Light current 20:04, 25 December 2006 (UTC)

I concurr. X [Mac Davis] (DESK|How's my driving?) 00:10, 26 December 2006 (UTC)

I don't think it is just the brain. The eyes do strain to open the pupil as wide as possible. In dim light, I suppose the eyes will have some difficulty in focusing. I don't agree with the analogy of straining the muscles to build them. You can not make your eyes better by reading in dim light, unlike the muscles. It is the unnecessary strain I was referring to. Even in case of muscles, you can't build them just by straining them. It will do more harm than good -- WikiCheng | Talk 04:02, 26 December 2006 (UTC)

I thought the pupils opened up automatically and you have no direct control over pupil size. as per our article:

In humans and many animals (but few fish), the size of the pupil is controlled by involuntary constriction and dilation of the iris in order to regulate the intensity of light entering the eye. This is known as the pupillary reflex. In bright light, the human pupil has a diameter of about 1.5 millimeters, in dim light the diameter is enlarged to about 8 millimeters.

--Light current 04:07, 26 December 2006 (UTC)

Well... I might be wrong regarding the strain due to opening of the pupils :-) -- WikiCheng | Talk 04:50, 28 December 2006 (UTC)

Custard Bread?

Will adding custard mix to my mixture for banana bread make banana and custard bread or something barely edible? --Username132 (talk) 11:34, 24 December 2006 (UTC)

It's impossible to guess the result, just try it. Your financial loss, if a failure, will be trivial! But reduce the amount of water you add, to compenate for the custard. Let us know, here, how it turns out - Adrian Pingstone 11:42, 24 December 2006 (UTC)

Baking in progress. Stand by... --Username132 (talk) 12:16, 24 December 2006 (UTC)

If that fails, simply mix the custard up normally, and serve it on the banana bread... Laïka 13:32, 24 December 2006 (UTC)

How is it coming? Must be done now. Don't leave us in suspense over the holidays...  --Lambiam^Talk 16:21, 24 December 2006 (UTC)

Sorry about that. It came out okay. It should be noted that I used powdered custard and less than half the water one would usually require to make it up. I felt it was a little dry but everyone else seemed to like it. --62.100.22.29 00:51, 25 December 2006 (UTC)

FYI, if the goal is to make the banana bread smoother, finer, richer, etc, a couple of tablespoons of mayonnaise would work better. The problem with powdered custard mix is that it's usually just flavourings, colourings and either cornstarch or tapioca, no real 'custard' (i.e; eggs and cream), just absorbent starches (sometimes some powdered milk). This would have the effect of bulking up your baking, without actually adding anything useful to it. And FWIW, tinkering like that with a finer cake, like a plain cake or an angelfood etc, could actually ruin it. But cooking experiments are fun, I'm glad it turned out OK at least. Anchoress 05:02, 25 December 2006 (UTC)

Using custard to moisten the finished bread is a good idea, but you didn't implement it in quite the right way. Instead of mixing the custard in with the banana bread mix and baking them together, I'd encourage you to prepare the banana bread and custard separately, then combine them when served. A nice layered presentation would be good, with banana bread on the bottom, custard next, then more banana bread on top. I would keep them separate until ready to serve, however, as the custard may make the banana bread soggy after a while. StuRat 11:32, 25 December 2006 (UTC)

The ultimate expression of this might be the trifle or the Italian rum cake.

Atlant 15:06, 26 December 2006 (UTC)

Infrared Filters

I want to optimise the sensitivity of some infrared sensors, for using in laser tagging games. I've noticed that there are being produced some IR filters that block a lot of visible light from the sun, allowing most IR to pass through. My question pertains to the usefulness of these filters, since the IR sensors should only be activated by IR light anyway (sure, the suns light included IR, but the filter doesn't protect against sun IR, just sun visible light). Is it worth bothering with? --Username132 (talk) 12:34, 24 December 2006 (UTC)

Depends on the intensity of the IR from the sun cf the intensity you are trying to recieve from the source Transmitter. Iwould think a filter centered on your IR wavelength couldnt do any harm and in fact may stop false triggering. Is the IR source modulated?--Light current 17:36, 24 December 2006 (UTC)

It is modulated and you must be right - the sensors must react to non-IR light. However the signals are indeed modulated. --62.100.22.29 00:54, 25 December 2006 (UTC)

OK If its modulated , you can make a circuit to respond only to the modulation ( a detector circuit). Then you only have the problem of sensor overload from the sun. Filters may achieve this 8-)--Light current 01:10, 25 December 2006 (UTC)

I'm wondering how the IR sensor can detect IR. Doesn't it have to use a filter to do so? --Bowlhover 17:50, 25 December 2006 (UTC)

Well the semiconductor types are desinged to be sensistive to just a small range of wavelengths . See Infrared_detector--Light current 18:01, 25 December 2006 (UTC)

Even they all seem to have a filter in front of them, though. It commonly appears weirdly-purple when viewed in visible light.

Atlant 15:09, 26 December 2006 (UTC)

Immitation compulsion

In a similar if not identical occurance of a child imitating an adult is one of the recognized reasons for society having laws against everything from Jay walking to playing basketball in the street to spiting on the sidewalk because other people have a tendency to compulsively imitate others in doing whatever they may see others do? Adaptron 13:30, 24 December 2006 (UTC)

No. Laws are to prevent the first person from doing it, not the second. alteripse 15:50, 24 December 2006 (UTC)

But laws are not written on the basis of speculating what someone might do but rather on the knowledge of what someone has done. Adaptron 21:41, 24 December 2006 (UTC)

While I don't think those laws are a good example, there are laws against "corrupting a minor", which is more like what you're talking about. They usually focus on minors being encouraged to have sex, use drugs and alcohol, etc. StuRat 11:23, 25 December 2006 (UTC)

Yes, now take that idea and apply it to peers or the more or less feeble minded. "Monkey see monkey do" kind of thing. Although a thing might make perfect common sense not to be done the law against it is necessary because some people do not have any common sense and when others see them doing the thing the seeing of it may outweigh their common sense as well. The law is there merely to outweigh the lack of common sense rather than to be oppressive or the work of a bunch of control freaks. Example: a law against playing basketball in a busy side street that happens to be a very common route that the majority of people take to get home. Some kids who lack common sense actually seek out friends who live on such streets so that can have more fun by making traffic one of the opposing players. Adaptron 03:03, 27 December 2006 (UTC)

Perhaps think more along the lines of game theory: what harm is it if I send you just one unsolicited advertisement via email, or perhaps throw a hamburger wrapper from my car window? But if the same behavior is global, so everyone throws a hamburger wrapper from their car window perhaps several times a day, then the city streets turn into snow-drifts of trash overnight. That's why littering is defined as a "bad thing." But *I* didn't cause the problem with my one wrapper, it was EVERYONE ELSE who did it. Yet everyone else is the same as me, and has identical reasoning, so they become angry at the thousands of litterbugs around them, yet don't stop littering. (And your little spammer-business should be perfectly legit, since its the millions of OTHER spammers who are wrecking the internet.) Then an extra party is added in the form of a policeman who writes you a $200 ticket even if you discard a tiny wadded-up gum wrapper on the street. And the terrible punishment applies even to *ME*, when obviously it should only apply to everyone else, since the huge litter problem is caused by all those thousands of strangers, not by me.

See what's going on? I want to be a "cheater," but at the same time want nobody else to cheat, because if they do, it makes the world a rotten place to live. I want to remove the inconvenience of having to save up my car trash and take it to the trash can, rather than just pitching it out the car window. One person's litter harms nobody. But as a human being, I'm just one identical bacterium in the huge culture dish, so whatever "bad" things I do will very probably be done by billions of other people as well, and that's what makes them "bad." One person spitting on the sidewalk is not problem, but what if 100K people in a city start doing it? We each cut down three trees, and Earth's forests vanish. We each catch five fishes, and no more fish exist. It has nothing to do with copied behavior, and everything to do with huge numbers of identical "actors" who all naturally end up performing the same actions for the same reasons.--Wjbeaty 07:15, 27 December 2006 (UTC)

One interesting effect related to this conversation is two methods of litter control. The "normal method" is just to let litter accumulate until it gets to a point that justifies hiring a crew to clean it up, then wait until it gets to such a level again. A newer approach, however, is to hire people to immediately clean up any litter. At first, this would seem to be less efficient, as most of the time this person won't be picking up litter, but only waiting around. However, when human psychology is taken into account, this strategy is effective, as few people want to be the first to litter, but many people are willing to add more litter to an area that is already littered. Thus, the majority of littering can be eliminated via this method. StuRat 14:15, 27 December 2006 (UTC)

Fluorescent light is dead...

In my bathroom, I have a standard 50W fluorescent lamp, which is fairly new (purchased in the last year or so). It is one of those ones which allows for "instant" powering up (not the like the older ones where you had to hold down the button to "charge" it up). In any case, the lughead repairman fixing some piping in the wall managed to drop it, breaking the bulb. I bought a new bulb, but now the lamp doesn't really work: it starts to "power up", gets very bright, and then shuts off completely. If you turn it off and on again it usually requires a few seconds in the "off" position before it will even do the "powering up" again.

Any idea about what's happened here? Is it fixable? Is it a problem with the bulb, or the lamp? Any thoughts? --24.147.86.187 17:26, 24 December 2006 (UTC)

Do you know if its got an electronic ballast or an inductance one (heavy coil in the base unit)? If its been dropped, who knows what circuit rearrangement there may have been inside the fitting. Its probably not worth trying to fix it.--Light current 17:40, 24 December 2006 (UTC)

I'm pretty sure it is a ballast. I opened it up awhile back and found there wasn't much to these lights -- a few wires here and there, the ballast being the only thing of any substance (a little plastic box). --24.147.86.187 22:36, 24 December 2006 (UTC)

Are you sure you bought the correct replacement bulb? I wouldn't expect a ballast (whether electronic or magnetic) to break upon being dropped. ("50W", by the way, isn't a standard size for any fluorescent lamp in common usage.)

Atlant 15:11, 26 December 2006 (UTC)

Lips

Why is homo sapiens appaerntly the only mammal to wear his lips on the outside?--Light current 17:51, 24 December 2006 (UTC)

As long as you realize that the answer to this type of question is basically a just-so story, I will tell you one. Humans have preferred to have sex with people with fuller, more visible lips, so there has been selection pressure over the eons for fuller, more visible lips. I realize this is perilously close to a tautology, but that is the problem with this type of explanation. Why do we prefer to have sex with people with fuller, more visible lips? I dunno, we just do. alteripse 19:12, 24 December 2006 (UTC)

Yeah its not quite the same kissing a chimp!--Light current 19:31, 24 December 2006 (UTC)

Alteripse's just-so-story is also called sexual selection, but the article doesn't mention lips. Are we really the only creatures wearing our lips on the outside, or are ours just red and more noticeable to us? What about other primates or the white rhino, for instance? ---Sluzzelin 19:57, 24 December 2006 (UTC)

OK a white rhino has nice juicy lips. Cant think of any other primates.--Light current 21:06, 24 December 2006 (UTC)

I once heard it was because naked human females, being bipedal, walk in such a way to conceal their vaginas. Therefore, the size of the lips were used to mimic the vagina. I, however, do not remember the source of this information.--Acewolf359 17:00, 29 December 2006 (UTC)

Why is the neutron more massive than the proton?

The neutron consists of two "down" and an "up" quark, the proton of two "up" and a "down" quark. An "up" quark has a charge of +2/3, a "down" quark has a charge of -1/3. So the quarks inside a proton repel each other much more than the quarks inside a neutron, meaning that you need more energy to hold them together. Since energy is mass, the proton should be heavier. Furthermore, the "up" quark creates a stronger electric field than the "down" quark, hence stores more energy, hence should be heavier. Both effects should add up and you (or rather, I) would expect the proton to be more massive than the neutron. Why does nature refuse to follow this logic? Thanks, AxelBoldt 20:59, 24 December 2006 (UTC)

You assume that the interaction between quarks can be described in terms of the electromagnetic force (mediated by photons), but the theory of quantum chromodynamics describes it as strong interaction, mediated by gluons. The properties of this strong force are completely different from the other fundamental forces.

True, both proton and neutron hang together because of the strong force, but I don't see how that would cause a larger mass for the neutron; the situation seems to be symmetric and based on the strong force alone I would expect equal masses. Quarks do feel the (comparatively weak) electromagnetic force in addition to the strong force, and this effect is not symmetric. AxelBoldt 01:34, 25 December 2006 (UTC)

Simple: down quarks have a greater intrinsic energy than up quarks. What I want to know is why the greater intrinsic energy of the down quarks in the neutron so nearly cancels the greater interaction energy of the proton (why their energies are so close). —Keenan Pepper 01:53, 25 December 2006 (UTC)

And of course like every child that has not yet tired of the game, I'll continue asking: why is the down quark more energetic, hence more massive? Is there any deeper way to understand it beyond "that's the way it is"? Thanks, AxelBoldt 20:24, 26 December 2006 (UTC)