Wikipedia:Reference desk/Archives/Science/2008 May 10

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[edit] May 10

[edit] Could magnetism be said to warp space-time in a similar way to gravity?

And spare me “jokes” about luminiferous ether. It’s just that there are obvious similarities between the attractive effects of those two forces on distant objects. (Although there seems to be no repulsive action with gravity). So, can magnetism curve space and slow down time like gravity? And if not, how does a magnet ATTRACT a distant object? Myles325a (talk) 00:19, 10 May 2008 (UTC)

I don't think so. As I understand it, the electromagnetic force (of which magnetism is one aspect) works by an exchange of photons, rather than a curvature of space. However, a magnetic field does involve energy, and I believe energy does warp spacetime (E=mc2 and all that), but that warping isn't what we feel as magnetic force. Physicists are working on theories that unify the various fundamental forces, so it's possible there are theories in which EM works in a similar way to gravity by curving spacetime, but in the standard theories EM is described by quantum field theory (exchange of particles) and gravity is described by general relativity (curvature of space) - trying to describe one in terms of the other is very difficult and no-one's quite managed it yet. --Tango (talk) 00:31, 10 May 2008 (UTC)
This is not such a crazy idea. See Kaluza–Klein theory. Nothing has really worked though. Quantum mechanics gets in the way. I have to run though. Sorry for the shoddy explanation. — gogobera (talk) 02:00, 10 May 2008 (UTC)
Magnetism follows an inverse cube law not an inverse square law like gravity. The electric force would therefore be more similar to gravity. Magnetism is similar to frame dragging though. Em3ryguy (talk) 12:57, 10 May 2008 (UTC)
It follows an inverse square law. It's just that every north pole is paired with a south pole and vice versa. The further you get, the proportionally closer the two poles are, and the more their effects cancel. — DanielLC 23:18, 10 May 2008 (UTC)
Its not really that simple. There are no north or south poles. A single electron moving through space produces a magnetic field that does follow an inverse square law but the field is complex. it is strongest perpendicular to the motion of the electron and nonexistant in front of and behind the electron which therefore makes it even less like gravity. If gravity and the electric force are like the stretching of space then magnetism and frame dragging are like the twisting of space. Em3ryguy (talk) 20:38, 11 May 2008 (UTC)

OP Myles325a back. Ok gogobera you SHOULD be sorry, because throwing Kaluxi—Zippi …Lapis—Laputski …Lupus—Kaluah …Whatever the hell those jokers are called—at me and then saying BYEEEE…. This is just what the other clown was doing. I would hardly be asking THIS question if I could UNDERSTAND anything on that page, would I? Now, instead of throwing someone to the most esoteric edges of physics, how about starting somewhere closer? Isn't it true that Einstein's General Theory received its first big corroboration when it was observed that light rays were deflected by the Sun's gravity? So, let me ask then, does Magnetism similarly deflect light? And it has been demonstrated that time slows down for objects in strong magnetic fields. So is anything like that observed in strong magnetic fields? And wouldn't such effects be much stronger as magnetism is so much stronger than gravity? And don't magnets just work on metals? In that case, how do those particle accelerators bend deflect those particles in a curve? See, just take it from there, and we will all be soaking up Kalitsy—CalvinKlein or whatever in no time at all. Myles325a (talk) 05:35, 12 May 2008 (UTC)

A magnetic field only has a very small effect on warping space-time. The reason is that a magnetic field contains energy. But you would need a collosal amount of energy in a small space to have a significant effect, so in practice we do not see it. Magentic fields also work on moving charges. The particles in a particle accelerator are charged and are deflected sidewasy by the magnetic field. If you have a CRT monitor or TV you can hold a magnet near the screen and see the distrotion in the picture. A magnetic field also has an effect on atoms, for example the Zeeman effect, because atoms are made from "moving" charged particles. Magentic fields of extreme levels (too strong for humans to make) will make atoms lose their spherical shape and become long and thin stretched out along the magnetic field lines. This may happen on neutron star surfaces. Graeme Bartlett (talk) 05:49, 12 May 2008 (UTC)

OP myles325a back. Again. Graeme Bartlett gets me confused by saying:

A magnetic field only has a very small effect on warping space-time. The reason is that a magnetic field contains energy. But you would need a collosal amount of energy in a small space to have a significant effect,…

Now, the ambiguity is: Are you saying that the BECAUSE a magnetic has energy it warps space-time, or are you saying that BECAUSE a magnetic field has energy it has ONLY A VERY SMALL EFFECT on space-time? Also, I thought that magnetism was much more powerful than gravity, as evidenced by my fridge magnets staying on my fridge even though the whole world is pulling them the other way. So why does not magnetism have a greater effect on space-time? And could you, with a sufficiently strong magnetic field, slow time down for particles a la neutron stars? Have any relativistic effects through magnetic forces been experimentally observed? Myles325a (talk) 03:37, 15 May 2008 (UTC)

I'm sure he is saying that the energy has a tiny amount of mass which produces a gravitational field that warps space. now its true that electric and magnetic fields are similar to gravity and frame dragging but there is no reason to think that they are identical. Em3ryguy (talk) 04:24, 15 May 2008 (UTC)

[edit] Dogs and cats

I sometimes see dogs and cats licking their privates. Do they ever do this to the point that they, shall we say obtain their jollies? FairmontMN (talk) 01:54, 10 May 2008 (UTC)

You may find Animal_sexual_behaviour#Autoeroticism_.28masturbation.29 interesting. --Tango (talk) 01:58, 10 May 2008 (UTC)

[edit] Conditioning

If you reward a behavior irregularly, it will condition that behavior very strongly, even when the rewards disappear. If you punish a behavior irregularly, it will tend to prevent that behavior very strongly, even when the punishments disappear. What happens if you both punish and reward a behavior, both irregularly? Will the animal shoot up a convenience store? Black Carrot (talk) 02:53, 10 May 2008 (UTC)

The idea behind this question is so good I imagine animal experiments must have been done on it, although I don’t know of any off hand. One would think it would involve how intense the drives to obtain a particular reward versus escaping a specific penalty were. In the case of things like food, where the need to obtain it can be absolutely vital, then perhaps a subject will risk much more than if the reward was less important. In human experience, some people will rob a bank at the risk of incurring long jail terms IF the potential reward is a very great deal of money. I suppose we all unconsciously work out negatives and positives for any action we are likely to take. After all, any action involves a cost in terms of effort, so everything we do is weighed up against the scenario of what would happen if we did not do it. Myles325a (talk) 03:08, 10 May 2008 (UTC)

Possibly, but the focus of my question isn't really on whether the animal will continue the behavior or not, it's what the side effects will be. See, if you do this to most humans, they'll get incredibly stressed-out and frustrated, whatever they wind up deciding to do about it. Some humans are pushed so far by conflicts like this that they become needlessly and self-destructively violent. I'm wondering whether animals have the same capacity for stress, and eventual mental illness, that people do, or if they respond to it more dispassionately, as merely a stimulus. Black Carrot (talk) 07:28, 12 May 2008 (UTC)

One of the assumptions of behaviorist school of psychological thought is that the behaviors are inherently dispassionate. The notion of isolating a specific stimulus and a specific response is hardly a complete theory of psychology, for animal subjects or for humans. Our psychology article has a good section on the rise of behaviorist thought and some of the later ideas that it spawned. Maybe this will give you some context - there are definitely realms where the simplistic experimental view of single-stimulus, single-behavior, single-response mappings do not really hold well, and you have described exactly such a case. Nimur (talk) 16:17, 14 May 2008 (UTC)
What does this sort of pychobabble mean, Nimur? If you are saying that animals feel no pain, then why bother with the animal cruelty laws? And as post-Darwin we all know that humans are animals as well, why should we get upset concerning human suffering? If someone forced your hand into a pot of boiling water and observed your sweating and screaming and face-pulling, would you approve of his dismissal of your extreme, albeit subjective, pain as an unscientific phenomenon? I would have thought this sort of uber-“scientific” rubbish had been thoroughly refuted by now. Here is a self-explanatory par I added to the talk page of Cetacean intelligence. As the page is transcluded now, I am posting both Nimur and OP Black Carrot this note on their talk pages.

With ref to Michele Bini’s comment above, dolphins are NOT the only animals that engage in self-destructive behaviour when panic-stricken or in extreme pain. All the ‘higher mammals’ including horses, cats, dogs and apes can present with human-like symptoms of severe stress. Dogs which lose a much-loved master can show every sign of ‘nervous breakdown’ and clinical depression, both behaviorally and physically. Other mammals will go on rampages, chew their own fur and eat their own excrement, refuse food and howl incessantly. Apes will throw themselves against their cages. In a series of notorious but well-conducted experiments of the 1960s, researchers tormented dogs to the point where they not only had ‘breakdowns’ but showed every sign of having become permanently insane through terror and pain. These were ‘higher’ animals. I have no idea whether you can make a butterfly mad, or drive a snail to distraction. Myles325a (talk) 04:36, 20 February 2008 (UTC) Retrieved from "http://en.wikipedia.org/wiki/Talk:Cetacean_intelligence"

Myles325a (talk) 04:13, 15 May 2008 (UTC)

I think you should see the behaviorism and psychology articles if my comments sound like "psychobabble." I did not even discuss the capacity of animals to feel pain or emotion! I don't see where you drew this conclusion from my statements. Nimur (talk) 14:56, 16 May 2008 (UTC)

Hi Nimur, thanks for your note re” “what you really meant”. Find below my response, which I am also posting to your Talk Page, and to OP Black Carrot.

There are many things in life that make me want to get down on the ground and pull up carpet tacks with my teeth, and one of the main ones is people who write or say something that reads as muddled or dead wrong and then, after they are taken to task for it, aver that the critic has misunderstood what was intended. The ensuing “debate” takes up everyone’s time, and WP talk pages, and archives, and bandwidth, and patience, and produces much more heat than light.

Your contributions, Nimur, are a copybook example of just such a skew-whiff dialogue. As WP is full of people waving hands and employing phrases that could mean any number of things, I will try to show you why writing clear English and saying EXACTLY what you mean in as concise and unambiguous way as you can, will render you far less misunderstood than you are at the moment. Before I continue might I ask you and others to re-read this and the preceding paragraph? You might not AGREE with the content, but is there anything at all there which you find less than crystal clear? Good. Then let's pass on to your recent offerings. I have put your words in bold type and my own comments in plain.

One of the assumptions of behaviourist school of psychological thought is that the behaviours are inherently dispassionate. Now what significance does dispassionate take on here? Let's not beat around the bush. Does this mean that animals don't feel pain, or that behaviourists don't believe they do, or don't care if they do, or don't believe that pain exists, or don't believe that animals feel pain the way humans do, or consider the subject of subjective feelings of pain as a metaphysical hobbyhorse external to scientific research?

And why would you opt for the murky term "dispassionate" rather than write "behaviours are inherently without emotion"? Dispassionate muddies the waters in this context because it can ALSO mean impartial, disinterested and the like. Are you using it as a "weasel word" because while it connotes "without emotion" it also tempers it with a soupcon of "impartial". Are the animal behaviours themselves "dispassionate" or are the scientists "dispassionate", or is it the methodology itself?

And what is the force of "inherently" here? How is "behaviours are inherently dispassionate" different from the shorter "behaviours are dispassionate". The addition of inherently would suggest that while some external observers might perceive certain animal behaviour as "passionate", objectively, that is "inherently", they are not. If this is not the meaning you intended, perhaps you could explain what you DID intend.

Now let us look at there are definitely realms where the simplistic experimental view of single-stimulus, single-behaviour, single-response mappings do not really hold well… Frankly, Nimur, there are NO interesting cases of animal, or human behaviour, which conform to the single-stimulus, single-response case. I spent a year of a University Psych course under a fanatical behaviourist learning about mice pushing levers for food. In the end, I ascertained that the good Professor preferred to record the highly circumscribed behaviour of mice because, as a scientist, he could not neatly explain what it is that HUMANS were doing, and as a border-line autistic, he was only dimly aware of the world of human experience, and cared even less for it.

A mouse pushes a lever and gets a food pellet. Great! Now, Cindy likes going out and often says "Gee, swell! When do you want to pick me up?" when she gets an invite, uh, sorry, the stimulus of a speech segment over a phone to that effect. But today, Cindy got just such a stimulus and replied to the effect that she was doing her hair. Now, we airy-fairy metaphysical types might just say that's because Cindy did not think that the boy who phoned was a "real spunk rat" or a "hunk". But, and I quote my erstwhile teacher on this, scientifically it should be said that there were "intervening variables" between the stimulus and the response, which made Cindy behave differently. What an absolute laff riot!! Everything—but everything—interesting in this episode lies in these "intervening variables". And as for Cindy, so for all humans, and the great bulk of life. It is another example of weasel words for you to say that the single stimulus – single response model does not (in some cases) old really well. Apart from jumping up when you sit on a tack and the like, there is NOTHING in life which can be described by such a mechanism, and it is an absolute indictment of the entire psychological "profession" that it was not laughed out of business when it was first proposed. So, do tell us, Nimur, what does "does not hold really well" mean?

Nimur, if you cannot quantify the stimulus – response model in life, can you at least quantify how often and in what circumstances human responses DO conform to such models? After all, if we are unable to record and quantify human responses, then we should be able to at least quantify the success to failure ratio of its predictions. My own estimate is that, after all those experiments, the success rate is close to zero. Millions of mice and pigeons pecked and pushed at levers and ran down mazes, and in the wash-up, decades later, I think it was B.F. Skinner himself who gave a description of how behaviourist theory can have some practical significance. Some college was having problems with student stragglers coming late for lunch and thus keeping kitchen staff waiting. Skinner suggested ringing a bell that would summon the students and then denying lunch to those who came more than 30 minutes later! Yes, we are indebted to Skinner and the behaviourists for this and many other such breakthroughs.

You end your piece on another weasel note. After noting that you did not say that animals did not feel pain, you finish with I don't see in any way how this has anything to do with the capacity for the animal to feel pain, nor the ethics of animal testing While OP Black Carrot's original post does not directly deal with animal cruelty, it broaches the subject of highly stressful / painful experiments in which an animal is rewarded and punished randomly for the same behaviour, and links it directly will existential pain felt by humans who might be exposed to such treatment in a social setting. It is hard to credit that you really have no idea how any of that can impinge on the broader topic of animal cruelty.

Moreover, I do not see why you simply do not declare yourself and say that what it is that you DO believe in this regard. Why duck the issue of animal (or indeed) human pain by sweeping it under the carpet of "complex behaviours"? And the question of animal pain is not a red herring. Descartes publicly propounded the theory that animals were no more than machines—a prototypically behaviourist notion—and that the noises they made when they were killed were no different in type to those of a creaking wheel. France, which still venerates Descartes has—for a European nation—a backward attitude toward animal suffering precisely for this reason.

But to get back to the main thread. Nimur, if you said exactly what you INTENDED clearly and without ambiguous weasel-words, then you would find yourself misunderstood on fewer occasions. As it is, if I have misunderstood you, then the preceding will give you fair indication why. Myles325a (talk) 04:55, 17 May 2008 (UTC)

[edit] sauna temperature control

How does the copper tubing temperature sensor in a sauna provide feedback to the electrical control box to maintain the temperature?

Will throwing some water on the copper tubing sensor damage the control box?

Will intermittent water squirted on the copper sensor eventually damage the sensor over a period of time? Jaimegonzo (talk) 03:05, 10 May 2008 (UTC)

I can't say I know exactly what the “copper tubing temperature sensor in a sauna” is, but I imagine that you might start with Bi-metallic strip#thermostats. Maybe that's entirely not what you're wondering about, though?
About the water… it seems likely to depend on the housing for the control box -- is it water resistant? Does the thermostat rely on electrical conductance at all? I would hazard a guess that in sauna temperatures, if “throwing some water on [it]” doesn't cause problems, then “intermittent water squirted on [it] … over a period of time” won't do much either. Of course, “period of time” is a bit vague. :P  — gogobera (talk) 06:02, 10 May 2008 (UTC)
If you have a real Finnish sauna it will tolerate water, as throwing water on the stove ("kiuas") is an integral part of sauna. A Finnish kiuas that doesn't tolerate water is a nonsensical concept. Check the stove manufacturer's instructions though; other types of steam rooms from other countries might not be designed for water. If the temperature sensor is inside the stove it will be protected from water. The sensor can also be inside a thermometer on the wall, turning the heating elements on and off based on air temperature rather than stove temperature. Weregerbil (talk) 09:43, 10 May 2008 (UTC)
The copper tube is likely a thermocouple. (A friend of mine recently cut one like this on a hot tub when he assumed it was a grounding wire). -- Flyguy649 talk 14:31, 10 May 2008 (UTC)
In thermostats, the copper bulb is usually just a gas-filled copper bulb, connected to the thermostat by a very thin copper tube called the capillary. Within the thermostat, the pressure of the gas within the copper bulb bears on a bellows and that presses on a mechanical switch. Heat the bulb enough and the mechanical switch opens the electrical contacts, shuts the gas valve, or what-have-you, shutting off further heating until the copper bulb cools down again.
Atlant (talk) 16:00, 12 May 2008 (UTC)

[edit] Rube Goldberg pendulum

In a Rube Goldberg machine I am building, a marble hits 'something' which causes a pendulum on the top of a tower to swing back and forth a few times before it hits another marble which rolls down the tower. I'm having some trouble deciding what must be used to do what I just described. What should that 'something' I mentioned earlier be? --hello, i'm a member | talk to me! 03:29, 10 May 2008 (UTC)

In truth I have some ideas, it wouldn't hurt if I get some more. --hello, i'm a member | talk to me! 03:30, 10 May 2008 (UTC)

No ideas but what you said doesn't really make sense to me. The pendulum will swing the greatest distance on the first swing. Thus it will reach the marble on the other side of the swing on the first, not necessarily the second, third, etc. swing. Dismas|(talk) 03:38, 10 May 2008 (UTC)
True if the pendulum swings in one plane. If the 'something' can provide an offset that causes the pendulum to oscillate in two dimensions, it can oscillate through several perioed before striking the target. Example: The pendulum bob might be held at an angle tothe vertical by a hook. the 'something' strikes the bob at an angle that dislodges it from the hook and imparts momentum that is not in the plane of the top of the pendulum. -Arch dude (talk) 04:07, 10 May 2008 (UTC)
This is what is so difficult about creating a pendulum to the marble on top: how do I create the nesscesary torque to cause the pendulum to oscillate like such (so that it eventually hits the marble)? --hello, i'm a member | talk to me! 04:21, 10 May 2008 (UTC)
Have you considered driving the pendulum by using another pendulum? Suspend two pendula from one crossbar such that both pendula have the same period of oscillation. Set one pendulum in motion. The system will be a bit 'leaky', and energy will be transferred from the moving pendulum to the stationary pendulum, driving it to oscillate. (The effect only works if both pendula have the same period.) TenOfAllTrades(talk) 06:00, 10 May 2008 (UTC)
Addendum: It's a fairly popular physics demo; here's a YouTube video of the principle in action: [1]. TenOfAllTrades(talk) 06:03, 10 May 2008 (UTC)
For another idea of how to get torque look at Driving wheel. We may have a page that describes it better, but I don't know where. Maybe s.o. else does. Otherwise just look at a model train. 71.236.23.111 (talk) 13:47, 10 May 2008 (UTC)

[edit] What is a "geographic feature"?

I've just created the article geographic feature, but I'm not sure I've defined the class entirely correctly. I took some of the material from other Wikipedia articles, and I don't know if they were correct.

For example, are countries and other administrative divisions geographic features? What about imaginary lines like borders, the Equator, etc.

I said they weren't (except for settlements), but I'm not 100% sure.

Wikipedia isn't consistent on geographic features, landforms, etc., and it isn't clear what is or is not a geographic feature. The article landform implies that landforms are not geographic features.

I couldn't find a definitive treatment of what is or is not one, so that leaves a bunch of things up in the air:

What about national parks?

Nature reserves?

What about orchards?

And then there's the sea floor, and its features, like trenches, submerged reefs, etc.

I look forward to your edits and comments.

The Transhumanist    07:28, 10 May 2008 (UTC)

Political boundaries and the like are not geographical features. That's why they are not invariably found on geographic (=physical) maps; they are found on political maps. - Nunh-huh 07:41, 10 May 2008 (UTC)
In the field of GIS, as well as cartography to some degree, a geographic feature is anything spatial you are representing on a map or in a geodatabase. The usual term is just "feature", but it's not uncommon to hear "geographic feature". I would argue that political boundaries and the like are geographic features. The field of geography includes political geography, not just physical geography. Pfly (talk) 07:59, 10 May 2008 (UTC)
I agree. It seems bizarre to me to say that political boundaries are not geographical features; maybe this is not as well-defined a concept as you seem to think. And while this is not the place to debate it, I don't see what the point is of having an article about geographical features in the first place. If they're things shown on maps, why shouldn't that article say whatever is to be said about them? --Anonymous, 08:30 UTC, edited 10:27, May 10, 2008.
Here is a great method of finding out what is a geographical feature and what isn't. Position yourself in a landscape, and point at anything that you know is there. Is it visible? If so, you've located a geographical feature. If it is a resident house, it is a very minor geographical feature, and a man-made one at that. If it is a tall mountain, it can be considered a major geographical feature. If it is a river, it is also a geographical feature, notable if it is big, not notable if not so big. What does the geography feature? It may feature a border station with customs, barracks and wire. The border control station is a feature - the political border is not. The wall of wire is a feature (major if big, minor if not), but is entirely disjoint from what is defined to be the end of a geographically defined administrative region. Hereupon lies the source of confusion with regards to wether or not a border is a geographical feature. Political boundaries are not geographical features. The wall the Israelis built just recently is, however, a geographical feature that signifies a political boundary.
I don't wish to take to the refdesk what should otherwise be on the article's talkpage, but you aired a question here, and as such it deserves my best answer. Scaller (talk) 12:19, 10 May 2008 (UTC)
Note that some non-geographic features are often included on geographic maps simply to help us locate the geographic features. State, provincial, and national boundaries and large cites might be included, for example. In the case of a map of California fault lines, it would be useful to know where Los Angeles and San Francisco are located. StuRat (talk) 20:58, 10 May 2008 (UTC)
I think what Anonymous said about the terms being only loosely defined is right. I know the word "geographic" is often used for physical things only, which would leave political boundaries out. But this usage is not the only one, nor necessary "correct". I just went and picked up a book I have called "Modeling our World: The ESRI Guide to Geodatabase Design". Here's a quote from page 25: "Geographic features are located at or near the surface of the earth. They can occur naturally (rivers, vegetation, and peaks), can be constructions (roads, pipelines, and buildings), and can be subdivisions of land (counties, land parcels, and political divisions)." Pfly (talk) 21:21, 10 May 2008 (UTC)
Another example is the USGS Geographic Names Information System. Although they mostly use just the word "feature", as in "feature name", "feature class", etc, they do use the term "geographic feature" on their FAQ page: "GNIS public Web site: Directly queries the database for official geographic feature names, their locative attributes, variant names, and other data..." The geographic features in the GNIS database all kinds of non-physical things, like counties, states, etc. Pfly (talk) 21:49, 10 May 2008 (UTC)

[edit] Screech of Chalk on a Blackboard

Has anyone done a Fourier analysis on the screeching sound which can be made by chalk or fingernails on a blackboard. Does anyone know why this sound is so unpleasant. 90.206.167.42 (talk) 10:49, 10 May 2008 (UTC)

Yes [2], and surprisingly the answer is the middle frequencies make it horrible, not the high frequencies. There is some suggestion that the sound is similar to primordial alarm calls and this is what makes us sit up and take notice. You can take part online in that sites study into what makes horrible sounds horrible. But be ready to cringe before you turn up the volume! SpinningSpark 13:20, 10 May 2008 (UTC)
And of course, I should have known, Wikipedia really does have an article on everything.SpinningSpark 13:23, 10 May 2008 (UTC)

[edit] determining the sugar content of grapes

hi, can anybody tell me how i would find the sugar content of grapes using the equipment found in a small lab? —Preceding unsigned comment added by 82.45.96.96 (talk) 10:56, 10 May 2008 (UTC)

Homework alert! Makey melly (talk) 11:10, 10 May 2008 (UTC)
Have you another looked at Sugar#measuring sugar ? SpinningSpark 14:48, 10 May 2008 (UTC)

[edit] Aircraft as flying disc

Can an aircraft able to transport a human being have the form of a flying disc? 217.168.4.133 (talk) 12:44, 10 May 2008 (UTC)

Yes it can, take a look at Avrocar, British Rail flying saucer and also Military flying saucers is interesting. There is also Lenticular Reentry Vehicle although this was not intended as human transport. SpinningSpark 13:03, 10 May 2008 (UTC)

[edit] Accelerated Thought.

The concept of gaining command over the matter, that is the entire nature through the process of accelerated thought demands attention. Is there any model which presents the operative dynamics of "accelerated thought"? —Preceding unsigned comment added by Dr.Ramakrishnan (talk • contribs) 13:22, 10 May 2008 (UTC) Dr.Ramakrishnan (talk) 13:31, 10 May 2008 (UTC)

Psychokinesis and James Randi --71.236.23.111 (talk) 14:19, 10 May 2008 (UTC)
I don't think this is about telekinesis. I think he means "How can we improve web-based education?". --Heron (talk) 14:24, 10 May 2008 (UTC)
Perhaps you are asking about the Future Shock effect, which predicted an ever-increasing rate of technological advance. IMHO this effect has failed to materialize. Can you clarify your question please ? StuRat (talk) 20:50, 10 May 2008 (UTC)

[edit] Photon energies in cosmological redshift.

Asked my physics teacher a rather obvious question after being taught about cosmological redshift the other day: If the energy of a photon is given by E=hf (planck's constant * frequency), yet the frequency decreases over time due to the expansion of the universe, then doesn't this violate conservation of energy? Won't photons from distant stars lose energy before they reach us? Where does the energy go?

I've had four thoughts about this:

1. Is planck's constant really a fundamental constant? Could it change related to the age of the universe so as to conserve photon energies?

2. Is the problem here that cosmological redshift (though not redshift due to relative motion, which I understand has energy conserved in a specific reference frame) is a prediction of general relativity, which is incompatible with quantum mechanics (which is where I assume the E=hf equation comes from)?

3. Moving on from the last point, does general relativity actually include conservation of energy? what about other conservation laws?

4. If it does, then is photon energy somehow conserved in a specific reference frame within general relativity, and the apparent loss of energy due to considering the photon from different reference frames?

Or is it something else altogether?

JMatopos (talk) 13:26, 10 May 2008 (UTC)

Photons do lose energy as the universe expands, and the simplest explanation is that it becomes potential energy of the gravitational field. But in a broader sense, energy actually isn't conserved in general relativity. There's a good (though somewhat technical) discussion here. On your four thoughts: 1. It's possible that the fundamental constants could change with time, but this has been tested and ruled out to pretty high precision. So this can't explain the loss of energy, and anyway it's predicted by general relativity without changing the constants. 2. There's nothing wrong with E = hf, but you could say the lack of gravitation in the standard model is the problem. 3&4. General relativity does predict differential energy conservation (the energy at a point equals the energy that was there before plus the energy that flowed in from elsewhere minus the energy that flowed out). But this has to be taken with a grain of salt because the "energy" here doesn't include gravitational field energy. Energy from the photons gets transferred to the gravitational field despite this law seeming to say it can't. Defining an "energy of the gravitational field" is surprisingly difficult. The page I linked says more. -- BenRG (talk) 14:46, 10 May 2008 (UTC)

[edit] Proving alcohol

Suppose, I'm filming a glass of vodka (or, generally any alcohol). How can I prove to the audience that this is vodka, not water? A litmus paper? --85.132.14.38 (talk) 13:43, 10 May 2008 (UTC)

Alcohol is flameable, right? Setting fire to it would prove its not water. Would spoil the drink though. —Preceding unsigned comment added by Makey melly (talk • contribs) 13:48, 10 May 2008 (UTC)
The simplest way isn't exactly scientific, but take a new, sealed bottle of vodka and open it in front of the camera. Any scientific test is just likely to confuse people, and could probably be faked anyway. I mean, if litmus paper worked, you might just end up trying to prove that it's real litmus paper. If you set fire to it, what's to say it's not just a liquid hydrocarbon or some other flammable substance? JMatopos (talk) 13:51, 10 May 2008 (UTC)
Well what is to prove you didn't fill a vodka bottle with water and then reseal it? Or change the label on the bottle? You could do all three; open a vodka bottle, drink some, set fire to some etc to prove beyond doubt. Or have a witness to say "yes, that is vodka". Makey melly (talk) 13:58, 10 May 2008 (UTC)
Yet in my mind, any attempt to 'prove' that it's vodka on camera would immediately raise my suspicions that it wasn't. Removing the foil seal on a new bottle of vodka is believable, natural and easy to do. Not that all these tests are a bad idea; I mean if you really wanted to 'prove' it, you could set some on fire, use a pH meter to show it's very mildly acidic and give some to a Russian who swears on his life it tastes like vodka. Seems like a lot of hassle, though. :-/ Besides, if I were watching this video, there's no way you'd prove to me 'beyond doubt' it was alcohol unless you personally gave me a sample to run through an IR spectrometer, and I figure that isn't an option. :) JMatopos (talk) 14:20, 10 May 2008 (UTC)
Having someone in the audience take a sip sounds like a best idea to me. --Tango (talk) 14:04, 10 May 2008 (UTC)
Dropping in some oil might work. It would separate out and float to the top in water. Breathalyzers use IR spectroscopy if you want something fancy. 71.236.23.111 (talk) 14:10, 10 May 2008 (UTC)
Ah, but how does he prove that the bottle of oil actually contains oil? Really, there's essentially no way to conclusively 'prove' the identity of a liquid in a videotape—virtually any conceivable test could be faked through mislabeling the reagents used, tampering with the instruments, swapping liquids during a cut between cameras, or using special effects. At some point, you have to rely on the trust of your audience.
The question here might be, "What property of the liquid is actually important?"
  • To show that it's nontoxic, just drink some.
  • To show that it's not straight water, use it to dissolve an ink stain. Test in advance to find an ink that will run in 40% alcohol but not (very much) in water.
  • To show it's not very viscous, slosh it around a bit.
To demonstrate much more than that, you're into a difficult place. Those three tests will demonstrate that it's a drinkable liquid of comparable viscosity to water with some hydrophobic solvent properties. The things that fit those criteria (especially the "I'm willing to drink it" test) are mostly distilled beverage spirits: vodka, white rum, gin, etc. Is that sufficient for your purposes? TenOfAllTrades(talk) 16:26, 10 May 2008 (UTC)
Of course one further problem is that people could easily feel the video may be faked. For example, it wouldn't be that hard to design a video that to the untrained eye looks like a continuous shot but in fact contains different shots and you could use one drink for the non-toxic part, one drink for the ink part and one drink for the not viscious part and one final drink for where you actually perform the final test on the alcohol solution (I guess there's a point to proving something is alcohol). Of course, you could add a billowing curtain or something similar in the background to help make this more difficult and you story more plausible. It would also be a lot more difficult, even without a curtain to ensure your video fools an experts. This really depends on a lot of things. If for example you are attempting a magic trick/illusion, some of the suggestions from TOAT or others combined with your assurances to the audience that it is alcohol and no camera tricks were used may be sufficient for many viewers. Obviously not everyone is going to be satisfied, but these sort of things generally require some degree of trust from the audience anyway Nil Einne (talk) 19:58, 10 May 2008 (UTC)
The problem to me isn't that you can "prove" it, but that it's illustrated to be Vodka -- whether the demo is faked or real, for the purposes of a video it illustrates your point. If it's to record an experiment then you;d be playing it straight for teaching purposes. Otherwise, I'm thinking advertising e.g. with two glasses, one labelled (our brand), and one (other brand) for example. Viewers know it's a setup but they suspend disbelief operating through the filmic "wall". Actors don't exactly scull drinks with litmus paper in them. Otherwise like comments above, you can also discredit your demo. Btw, if using a glass of vodka with the oil drop, it seems appropriate to have a glass of water + oil to compare results. Apols if this is all too beside the point, Julia Rossi (talk) 02:24, 11 May 2008 (UTC)
Goldfish. Put goldfish in the alcohol - dead goldfish proves its not water. Of course, it could still be turpentine, so personally I would not drink any on the basis of that proof, but it is definitely not water. SpinningSpark 20:52, 11 May 2008 (UTC)
give some to a member of the audience. --Shaggorama (talk) 05:56, 15 May 2008 (UTC)

[edit] aurora borealis from space

Can the aurora borealis be seen from space? Mr Beans Backside (talk) 13:55, 10 May 2008 (UTC)

Yes; see http://en.wikipedia.org/wiki/Image:Aurora_australis_20050911.jpg and http://en.wikipedia.org/wiki/Image:Aurora_Borealis.jpg - Bear in mind that the first image is a composite and has been enhanced, though - it's not really that bright. JMatopos (talk) 14:01, 10 May 2008 (UTC)
Yes. You can even see aurora on other planets (see Aurora (astronomy)#On other planets). --Tango (talk) 14:03, 10 May 2008 (UTC)
Absolutely. Here are links to some NASA images: [3], [4]. POES (Polar Operational Environmental Satellite) observes aurorae at the north and south poles; reports are available here, among other places. TenOfAllTrades(talk) 14:09, 10 May 2008 (UTC)

[edit] Why are magpie's tails so long?

What is the explanation for the length of the magpie's tail. It must be an adaptation to something, but to what? Since both sexes have the same tail length it cannot be sexual selection. 217.42.89.22 (talk) 14:17, 10 May 2008 (UTC)

I disagree that it can't be sexual selection. Both males and females may choose mates that have a long tail, as that's a sign of good health and genes. StuRat (talk) 15:17, 10 May 2008 (UTC)
Just a thought: Long tails are good for balancing. This may be a factor here. Since there are long and short tailed species (e.g. cats, monkeys), this is not a very selective trait, but it might cause a new species to split off. 71.236.23.111 (talk) 15:19, 10 May 2008 (UTC)
Every magpie in my area has a certain green-blue tint to their tails, very much like the plumage of a pigeon (bar then the red/purple). I will therefore present the argument that it can have a sexual purpose. Scaller (talk) 17:39, 10 May 2008 (UTC)
Edit: See this -> http://upload.wikimedia.org/wikipedia/commons/8/8b/Elster_wikipedia2.jpg Ah, what a beautiful picture. Serves my purpose perfectly, even. Scaller (talk) 17:41, 10 May 2008 (UTC)
See this research paper on the correlation between tail length and general health in black billed magpies. It looks like they are an honest signal on the overall health of the bird to prospective mates in boths sexes. Multiple elements of the black-billed magpie's tail correlate with variable honest information on quality in different age/sex classes. Lumos3 (talk) 22:19, 10 May 2008 (UTC)

[edit] machine that destroyeds itself

Who invented a machine that destroyed itself on purpose? Mr Beans Backside (talk) 14:44, 10 May 2008 (UTC)

The Manhattan Project. FairmontMN (talk) 14:46, 10 May 2008 (UTC)
...or for that matter any explosive, used in war or peace, like blasting caps. I suppose an artist might also create such a thing for "artistic reasons". There are also disposable machines, like a disposable camera. Finally, there is "planned obsolescence", whereby a device intentionally fails after some period of time to make you go out and buy another. StuRat (talk) 15:23, 10 May 2008 (UTC)
Possibly you are thinking of Jean Tinguely [5].--Eriastrum (talk) 19:32, 10 May 2008 (UTC)
If with "machine" you are referring to the device commonly known as homo sapiens, all you have to do is to find the name of the inventor. --Cookatoo.ergo.ZooM (talk) 23:22, 10 May 2008 (UTC)
Someone recently reported in the Risks digest that he had been awakened one night by the carbon monoxide detector in his home beeping every 30 seconds, like the way some devices signal a low battery, but in this case it was displaying Err. He located the manual on the Web and learned that the manufacturer said the device should be replaced after 7 years -- and that they enforced this by having it count 7 years and then automatically stop working and go into this error state. (Wouldn't it be fun to be the company's lawyers if someone died of CO poisoning because this happened and then there was a genuine, undetected CO emergency before they could get to a store to replace the detector?) --Anonymous, 09:00 UTC, May 11, 2008.
Outside the US, I don't see how this would be a problem. If the device started to beep once it entered into a deactivated mode, then the person would either put up with it or turn it off. If you've turned off your device or are ignoring the beeping, you can hardly complain to the company that the device didn't detect CO. Outside the US at least, this would probably be far better for the company then if their device were to be ineffective after 7 years but if the device didn't warn you of this fact Nil Einne (talk) 17:18, 11 May 2008 (UTC)
I believe the person who posted the story was in fact in the US. In any case, I think there is certainly cause for complaint if the device deactivates itself without advance warning (and I don't consider the fact that the manual mentions it to be adequate warning). Even if one accepts that the basic idea is sensible, it could have started beeping a month ahead, for example. --Anon, 04:54 UTC, May 12, 2008.
Who's to say the device wasn't still working anyway? Did someone actually test it? There's a good chance the err mode still would have gone to emergency mode if there as a leak. In any case, any beeping is liable to result in the person with the device either ignoring the beeping (rare, I doubt anyone could stand the intermitent beeping for very long if it's like a smoke alarm) or turning it off, which as I've already stated, defeats the purpose of the device. Note that it's the manufacturer is going to say "REPLACE DEVICE NOW, IT NO LONGER WORKS" the same way they say "REPLACE BATTERIES NOW, IT NO LONGER WORKS" but I'm pretty sure if you actually test most devices, they may still work provided the problem doesn't stop them from working (which is one of the reasons why they tell you it no longer works). It's generally a bad idea to actually make a device completely deactivate since there's always a risk the device may do it without giving the proper warning somehow. Note that if the person wasn't already aware they should replace the device in 7 years or it's going to start beeping, which we can assume they weren't since they didn't replace the device, then they alway likely weren't aware they should replace the device in 7 years because it's likely to be ineffective after then. It is FAR, FAR better that they were actually made aware of the fact that the device was no longer effective then it is for them to go along their merry way with a non-beeping but ineffective device. Moving the time frame forward doesn't actually achieve anything, it just makes the problem worse (besides I highly doubt the device actually started beeping at exactly 7 years). Note that if you're referring to some sort of complex electronic alarm system which warns the user until he/she turns it off 1 month before, then say more urgently 15 days before, then say every day a week before, while this may sound good in practice, in reality something like this is 1) expensive 2) far more likely to go wrong meaning that in pratices it's simply a bad idea. A simple device which goes into 'error' mode when it has a problem (like the person forgot to replace it even though he/she was supposed to) is far, far better. Let's not forget in the end the only reason anyone will ever encounter this is because they were stupid enough to not replace their device when they were supposed to.Nil Einne (talk) 16:05, 12 May 2008 (UTC)
I think one could go so far as to say that a primitive animal trap like a rock held up by a precarious stick with bait on it is a self-destroying machine. --Shaggorama (talk) 05:59, 15 May 2008 (UTC)

[edit] airport security system x-rays (part I)

Are the airport security system x-rays the same in strength at those at the dentists? If so, why do the dentists run out of the room when they use the x-rays but the airport staff are next to them all day long? Mr Beans Backside (talk) 14:55, 10 May 2008 (UTC)

The X-rays at airports are contained within the box that checks your luggage by lead, whereas your dentist has no such protection from the X-rays.
Not sure about the relative strength, but the X-ray machines at the airport are shielded by those strips that fall down on either end, while the one at the dentist's office is not shielded, so that makes a big difference. StuRat (talk) 15:14, 10 May 2008 (UTC)
As a note, there are different grades of X-rays at airports. Checked baggage undergoes more intense x-raying than carry-on baggage, to the point that undeveloped film in checked baggage can end up getting fogged, whereas film in carry-on luggage will not. --98.217.8.46 (talk) 17:30, 10 May 2008 (UTC)
From what I can tell, this isn't universally true [6] Nil Einne (talk) 17:11, 11 May 2008 (UTC)

[edit] airport security system x-rays (part II)

Does the average airport security system x-ray the contents of your stomach? For example if you were hiding something illegal in there would they find it? Mr Beans Backside (talk) 14:56, 10 May 2008 (UTC)

Only if you jump on the conveyor belt along with your luggage. The thing you walk through is just a metal detector, not an X-ray machine, so it would only detect large metal objects in your stomach. StuRat (talk) 15:05, 10 May 2008 (UTC)
Oh, thank you. That clears a few things up. Mr Beans Backside (talk) 15:11, 10 May 2008 (UTC)
The metal detector would not detect anything other than metal in your stomach. You should probably check out this legal disclaimer and this medical disclaimer though, I seriously wouldn't advise trying it. It's dangerous from a legal and medical point of view. Regards, CycloneNimrodTalk? 15:13, 10 May 2008 (UTC)

[edit] rechargeable batteries

Can i use rechargeable batteries in television remotes? The instruction manual says not to use them. What damage would it cause? Mr Beans Backside (talk) 14:58, 10 May 2008 (UTC)

Generally it is best to follow instructions for the sake of safety, but in this case i'm pretty sure the only difference would be reduced performance in terms of the life of the battery. Regards, CycloneNimrodTalk? 15:08, 10 May 2008 (UTC)
I think it's more of an issue of the rechargeable batteries not having sufficient voltage to operate the remote, especially after they've been recharged hundreds of times (they get progressively weaker with each recharge). StuRat (talk) 15:09, 10 May 2008 (UTC)
Yes, the difference is 300mV per cell (NiMH or NiCd rechargeable against Alkaline). So assuming your remote takes two batteries it will start off 0.6V too low and then steadily deteriorate. Couple that with NiMH do not perform at their best in low drain/infrequent use applications you may find you have to take the batteries out to recharge quite often. On the other hand, disposable batteries in a TV remote would typically last a year or two, close to the shelf life of the battery. Another common problem with rechargeables in this area (though possibly not usual for TV remotes) is that any device with a low battery warning calibrated for alkalines is going to go off way too early. In short, I agree with the first answer - follow the instructions. SpinningSpark 17:08, 10 May 2008 (UTC)
Rechargeable batteries also have a very noticeable self-discharge phenomenon. That is, even without a load, they discharge themselves over a fairly short period of time (a few months). By comarison, I find that a fresh alkaline battery used in a typical infrared remote control can last several years in that very-light-duty service. This makes the alkaline battery more appealing to me.
Atlant (talk) 15:48, 12 May 2008 (UTC)

[edit] Soil moisture measurement (copied from Misc. desk)

The following is on the misc desk. Doesn't seem to work there, so I copied it here: (don't know how to move stuff)71.236.23.111 (talk) 16:40, 10 May 2008 (UTC) Which method would be more reliable to measure soil moisture: resistance or capacitance? Does different soil type contribute much to the measured resistance/capacitance? Does capacitance method still work at freezing temperatures? I'm working for a automatic watering controller using soil moisture measurements and the accuracy doesn't have to be very high, but I do want it to work reliably between different soil types. --antilivedT | C | G 07:01, 10 May 2008 (UTC)

Take a look at Frequency domain sensor which seems to give some of the answers to this and Soil moisture#Geophysical methods has links to some other probe types. SpinningSpark 17:22, 10 May 2008 (UTC)

[edit] What's the name of the fish species...

... in which the male is far tinier than the female, and ends up living parasitically inside her vagina (or fishy equivalent)?

thanks, Adambrowne666 (talk) 17:59, 10 May 2008 (UTC)

Anglerfish. --98.217.8.46 (talk) 18:04, 10 May 2008 (UTC)
You might note that although the male does become a parasite attached to the female's body, this is not inside her oviduct.--Eriastrum (talk) 19:42, 10 May 2008 (UTC)
Thanks very much - so am I conflating two species then? - is there a happy, nonparasitic fish that does live in the oviduct? Adambrowne666 (talk) 23:23, 10 May 2008 (UTC)

[edit] Ridiculous genomic databases and their stupid lies

I'm trying to get a gene sequence around its transcription start-site, so I'm using this Japanese website: http://dbtss.hgc.jp/ - I am interested in the TJP1 gene: http://ensembl.genomics.org.cn/Homo_sapiens/geneview?db=core;gene=ENSG00000104067

When, on the Japanese database page, I set the category to Ensemble(ENST), and insert the code ENSG00000104067, I get the message: Sorry, there is no hit data. Your search keyword is 'ENSG00000104067'. Is there an alternative to way? ----Seans Potato Business 20:00, 10 May 2008 (UTC)

Sorry this may be way off, but would this help? [7] —Preceding unsigned comment added by Lisa4edit (talk • contribs) 22:45, 10 May 2008 (UTC)
Thanks, Lisa. If I go to the page you linked and click on the "genomic sequence" link on the left panel, it seems to give some potentially-useful information but I'm having trouble figuring out what's being displayed. The 'flanking sequence' form fields seem to have no effect and I can't find the transcription-start site. ----Seans Potato Business 23:09, 10 May 2008 (UTC)
That would be under "Gene information" and there's a link there for the start, at least I think that's it. --Lisa4edit (talk) 23:38, 10 May 2008 (UTC)

Personally, I use this site for all of my searches. Wisdom89 (T / C) 17:42, 11 May 2008 (UTC)

What settings do you use? I used Swiss-PROT/TrEMBL and search for TJP1 and then I get an information page, with links to other pages which include the sequence. But there's no way of telling where the transcription start site is. That ExPASy site seems to be mostly dedicated to proteins. ----Seans Potato Business 21:25, 11 May 2008 (UTC)
Why don't you export it directly from Ensembl? Find the gene you want, then choose the transcript you want (e.g. [8]). Then note where it says the transcript is found ("Chromosome 15 at location 27,778,863-27,901,974."). Since the gene is on the reverse strand, that means the beginning of the transcript is at 27,901,974bp on C15. The you can export the sequence from Ensembl. On the tab on the left, click on "Export transcript data". [9]. On this page you can choose the sequence you wish to export. If you would like to see 50bp either end of the transcriptional start you should add and subtract 50 from the start value: ("Chromosome 15, Bp 27901924, Bp 27902024") [10]. Choose your output format and, viola... you have the transcriptional start context. Rockpocket 22:21, 11 May 2008 (UTC)
If I go here: [11] to export a sequence and either a) retain the transcript value and continue (0 upstream and 0 downstream bp added) b) change to gene and enter tjp1 and continue, neither of the presented sequences begin with the start codon. Thinking more about the word 'transcript', I figure that in this context it just means the DNA sequence that is transcribed, so I'd expect a start codon at beginning of this sequence, even if not for the gene (which I suppose includes promotor info?). --Seans Potato Business 00:02, 12 May 2008 (UTC)
Transcripts don't typically begin with a start codon. They have something called 5'UTR first. If you want to start your sequence with an ATG then you want the cDNA sequence, not the transcript. Rockpocket 01:33, 12 May 2008 (UTC)

[edit] Seagulls

What was the natural habitat of the seagull before humans started interfering with the environment and encouraged them into towns and cities? Are there any seagulls left that still live as nature intended? --62.136.203.112 (talk) 23:30, 10 May 2008 (UTC)

We have an article on seagulls, you know. Anyway, as the name might suggest, they're seabirds, typically nesting on seasides. Their natural diet includes fish and other sealife, although they're opportunists and will readily exploit other available food sources. —Ilmari Karonen (talk) 23:50, 10 May 2008 (UTC)
Beat me to it. : Seagull isn't all the same. Our Gull page lists quite a few species. Some fish, some scavenge, some hunt other birds and eat eggs and some steal the catch from others. Most gulls live in costal areas. Only some species live near humans. (I guess if you eat dead tuna or dead duck it doesn't matter much if it has been in a can or trashcan before, or is "fresh" from the beach. :-) Lisa4edit (talk) 23:58, 10 May 2008 (UTC)