Wikipedia:Reference desk/Archives/Science/2007 January 8

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January 8[edit]

electron hotel[edit]

i need to know the answer to n=4

For the hotel californium n=42 is the answer.--JWSchmidt 02:38, 8 January 2007 (UTC)
Wouldn't that be n = 98 ? See the periodic table. You can check it out any time you like. StuRat 15:43, 8 January 2007 (UTC)
Ah, that would be for californium. JWSchmidt was talking about Hotel Californium, which require deep thought to understand. School-boy error. Skittle 02:43, 9 January 2007 (UTC)

Your question isn't clear. First off, what is an "electron hotel" ? StuRat 15:49, 8 January 2007 (UTC)

Hi Stu! googled to find this "Complete electron hotel assignment: Create quality representation of electron orbitals from n=1 to n=4, include filling rules (DUE: Mon, 01/08)." I expect we won't be too late! As for the hotel, it may be taken as an analogy, electrons filling orbitals as customers fill rooms (?) -- DLL .. T 18:13, 8 January 2007 (UTC)
Hmmm, and the s-orbital electrons can be "charged based on double occupancy", I suppose ? StuRat 05:25, 9 January 2007 (UTC)

Diffuse/Lambertian reflection[edit]

The Lambertian reflectance article says that it is used as a model for diffuse reflection, and for most of its mathematics links to the Lambert's cosine law article which says that blackbodies obey it (the Stefan-Boltzmann law article corroborates this). However, while diffuse reflection provides equal intensity in every direction, and I was under the impression that black-body radiation carried that property (see for instance the end of the linked section: "the radiation is the same in all directions"), the cosine law does not appear to do so. What gives between these three concepts, each of which is attached to the other two in inconsistent ways? --Tardis 02:21, 8 January 2007 (UTC)

What gives is foreshortening. Read the second paragraph of Lambert's cosine law, and the "Details of equal brightness effect" section, again carefully. —Ilmari Karonen (talk) 00:32, 9 January 2007 (UTC)
I actually understood that; I was just trying to figure out how the radiation could be "the same in all directions" as mentioned in the BBR article. I have since determined that the specific intensity (measured along a radius from the source) is isotropic although the irradiance is not (in terms of the normal to the surface with which it is measured). I wonder if the irradiance is isotropic (for the directions toward the source) for an infinite planar black body? --Tardis 19:27, 11 January 2007 (UTC)

Provisions for recharging electric vehicles from the grid by cities[edit]

What cities offer on street parking meters and off street parking spaces which are fitted with electric vehicle recharge stations (including area or spaces reserved for electric bikes under 750 watts) and ask a lower price for recharging than the equivalent energy cost of gasoline? -- Barringa 21:13, 7 January 2007 (UTC)

Note that you can't just do a straight comparison of the amount of electricity to drive X distance versus the amount of gasoline to travel the same distance. This is due to the relative efficiency of electrical power versus gasoline is higher for stop and go traffic than constant speed travel. This is because a gasoline engine still must burn fuel to idle, while an electric engine doesn't need to do so. Thus, the cost advantage of electricity will be higher (or the disadvantage lower) for city driving and rush hour driving. StuRat 15:33, 8 January 2007 (UTC)

Is meme a scientific concept?[edit]

Is meme a scientific concept? How does one find out? Is there a procedure to determine if a concept is scientific or not? 04:21, 8 January 2007 (UTC)

There is no procedure to determine if something is "scientific" or not, and this bothers some people, and it may or may not be good. There are however, a lot of qualifications that we like to say. I recommend reading: falsification, verifiability, Occam's razor, scientific method, logical fallacy, double-blind, skepticism, peer review, and scientific misconduct. Others are welcome to provide more attributes and related information. However, this is something a bit different. I would say this is a scientific concept, if I had the option of saying it was or it wasn't. This is based on its relation to science, although you could say anything really is related to science, since it can be described most likely somehow scientifically. X [Mac Davis] (DESK|How's my driving?) 05:18, 8 January 2007 (UTC)
I think the overall link you are looking for is demarcation problem, which is specifically about the difficulty in coming up with rigorous criteria for what is and isn't "scientific". -- 15:40, 9 January 2007 (UTC)

I would say that gene is much more 'scientific' than meme; the former has a huge number of ancillary terms surrounding it, while meme does not. Vranak

Gods, there's the problem of measuring how scientific words are? Scientifically related sounds better. "Tau meson" is more scientific than "polyethalane" though? There have got to be ranks in science, with something like, brane cosmology, superstring theory, spintronics, and particle physics being way up top. X [Mac Davis] (DESK|How's my driving?) 13:18, 8 January 2007 (UTC)
I'm just using my intuition, as usual. Vranak
In science we study many concepts that are not scientific of and by themselves: hunger, jealousy, pollution, taste, and so on. The scientific method involves hypothesis testing. The aim is that the process is reproducible, so that other scientist who independently test the same hypothesis will reach the same conclusions. This requires that concepts used in the hypothesis be defined in a very precise way (for instance by operationalization), so that the interpretation is not up to the subjective whim of the individual scientist. It is only in the context of this process that the concept becomes a scientific concept. For some concepts (temperature, energy) there is broad consensus among scientists what definitions to use, so you do not have to supply them each time; they are understood. For a concept like jealousy, no such consensus exists and you'd have to supply an operationalization if you want to make it a subject of scientific research. The same applies at present to the meme concept. One can study certain aspects of the reproduction of human cultural behaviour, where said aspects conform to the notion of memetic transmission. To do so in a scientific way, you probably need to be more precise about how you define the notions involved in your study than by saying "self-propagating cultural unit".  --LambiamTalk 13:50, 8 January 2007 (UTC)

People such as Ed Wilson have explained the biological basis for memes. The main problem is that while the physical basis of genes has been very well defined by molecular biologists the neural networks that allow memes to exist are still being is a much more technically difficult problem. Secondarily, the idea that our genes have influences on our mental lives it not currently a popular idea within the soft sciences. Anyone who studies the links between genes, memes and culture is attacked by thought police who are not interested in the science. --JWSchmidt 18:24, 8 January 2007 (UTC)

From what I have read, it is not a hard scientific concept. I have read of criticism leveled at Wilson because of this (I believe in a New Yorker article earlier this year). It is an alluring concept and sounds convincing, but is not anywhere near the same as a gene. But a lot of sociology is not as cut and dry as the stuff of "hard science" so it can be held to a different standard if we don't put it side by side with genes, proteins, and hormones (for example). Also, give it more time, as it is a new concept still and if it has merit, we can hope to see it become more popular and eventually more accepted. Muerteverde 04:54, 13 January 2007 (UTC)

Atmospheric pressure[edit]

What would the atomospheric pressure be at an elavation euqual to the bottom of the Atlantic seafloor, but uncovered by water? In other words, if there was an open place on earth where the elevation was that low, would the pressure still be significantly different than sea level?

Klatue 06:23, 8 January 2007 (UTC)Klatue

(I fixed the spelling of the question title.)

This table is extracted from the 1986 edition of the "Rubber bible". The left-hand column is depth below sea level in meters, the right hand air pressure in millibars.

                   0   1013.25
                 500   1074.7
                1000   1139.3
                1500   1206.9
                2000   1277.8
                2500   1352.0
                3000   1429.7
                3500   1510.9
                4000   1595.9
                4500   1684.8
                5000   1777.6

The book does not say how the pressures were determined, and does not go to greater depths, but it's easy to extrapolate approximate values to moderately greater depths. Several of the Atlantic's deep basins have points between 5000 and 7500 meters deep, according to the atlas I checked, so the pressures you're askingabout could go to somewhat over 2000 mb, maybe up to around 2300 mb. --Anonymous, elevation 130 m (or so), January 8, 2007, 08:44 (UTC).

Aren't there mine shafts that deep ? In this case, wouldn't it simply be a matter of measuring the air pressure at the bottom of the shaft ? StuRat 15:21, 8 January 2007 (UTC)
I don't know the answer to the original question, but the deepest mine is about 3585 meters [1] or about 11,700 ft. Cheers Geologyguy 19:04, 8 January 2007 (UTC)
That source has the quote "...nobody has ever been able to drill down further than 15 km". So why don't they consider a 15 km deep hole to be a mine ? In any case, assuming the hole is filled with air, it seems possible to drop a probe to the bottom to measure the air pressure. StuRat 05:18, 9 January 2007 (UTC)
Why isn't it a mine? Because people don't go down it and extract minerals. --Anon, Jan. 9, 22:29 (UTC).
The minerals that were in the location which is now a hole were certainly "extracted" from the hole. So, is the fact that people don't fit down it what makes it no longer a mine ? StuRat 04:21, 10 January 2007 (UTC)

Hall effect sensor/switch identification[edit]

I'm trying to identify a Hall effect sensor or switch which I am pretty sure is a switch instead of a linear sensor because three of them are recessed into the stator to commutate a 3 phase DC brushless motor through a controller with what I judge to be a square wave from the amount of torque ripple the motor produces under load at startup. Once up to running speed, however, the motor purrs. The only reference I have is a barely visible designation on two of the sensor/switches which is: "F41.5Gc". The "G" in the "5Gc" could be an "0" or a "6" but I'm with 99% confidence sure it is a "G". It is most likely manufactured in Asia, probably China but possibly elsewhere. Allegro sales office says they are not able to identify it and Google produces no reference or clues. Thanks in advance. Barringa 08:27, 8 January 2007 (UTC)

This is a SS41 Honeywell equivalent bipolar switch with a hys. of about 30. 02:41, 12 January 2007 (UTC)

radio broadcasting[edit]

What is the name of the phenomenon in which a radio frequency transmitter transmitting with enough power, causes undesired sound to come from the speakers of and audio system. In every instance that I've heard of it occuring, it was caused when someone has audio system too close to a comercial radio station tower or an amateur transmitter that is using too much power.

Thank you for your help. 08:38, 8 January 2007 (UTC)

See Audio feedback. Natgoo 10:46, 8 January 2007 (UTC)
I don't think the audio feedback article is relevant. There is no signal feedback from receiver to transmitter, either audio or otherwise, is there? The problem is to do with the signal being to strong, but I don't know of any name for the "undesired sound".--Shantavira 11:12, 8 January 2007 (UTC)
Whoops you are correct. I misread the question in my not-yet-caffeinated state. Sorry. Natgoo 11:59, 8 January 2007 (UTC)
Interference caused by Electro-Magnetic waves of Radio Frequency. In Wikipedia, Radio frequency interference (RFI) redirects to Electromagnetic Interference. Apart from its "usefulness" application in electronic warfare, are there beneficial applications of the phenomenon? It would be unusual if no one has found such a useful application, but I can not think of one. --Seejyb
You might be hearing the RF transmission because it is saturating an amplifier circuit, or because of inadequate shielding or a poor connection on a low level input circuit. I have heard a voice radio signal come out of the speaker of a stereo console, even with the unit turned off. In that case it was either Citizens Band or "Ham" radio, but no aspersions, it just happened he was nearby and a commercial transmitter wasn't. The speaker wiring was acting like a Crystal radio, picking up signal voltage from the radio transmitter, and rectifying it by an imperfect metal to metal contact of a loose speaker connection. There was apparently enough capacitance in the speaker or the splitter capacitor between the bass and treble speakers to serve the function of integrating the RF voltage to make the modulating voice signal audible. In times past, radio experimenters would make a detector out of a broken razor blade, and listen to AM signals through headphones, also with no amplification. They would have an inductance and capacitance combination to tune the reception, but if there is a powerful enough local transmitter, it may drown out the others avoiding the need for tuning. People have reportedly heard radio transmissions through fillings in their teeth. Sometimes a Public address amplifier system picks up radio stations or aircraft transmissions for similar reasons, and bypass capacitors are used to shunt out the RF signals from the microphone inputs. Edison 13:23, 8 January 2007 (UTC)
This reminds me of the time I was in the kitchen making breakfast when my boom box, turned off at the time, said to me (quite loudly) "How's it going, good buddy ?". I, of course, said, "It's going just fine, Mr. Radio, and how are you today ?". StuRat 15:17, 8 January 2007 (UTC)


From The Core article:

  • Moving closer to the center of the Earth should result in a decrease in the force of gravity, but no such effect is shown in the movie.

Really? Why? And how would one observe such an effect—that is to say, what would happen? -- 10:21, 8 January 2007 (UTC)

Lets say you are in the middle of the earth. Half of the earth is above you and half below. They each attract you with equal and opposite force and cancel out. You feel no force. Something like that.WP 10:39, 8 January 2007 (UTC)
Gravity is caused by attraction of objects. When you bore towards the center of a solid sphere, there is less matter below you to pull you down. So you get lighter. At the center you get zero gravity (which way would it point anyway?) The force of gravity is as if all the mass above you didn't even exist; only the mass below you matters. For a mathematical formulation, see the "solid spheres" section of shell theorem. Weregerbil 10:42, 8 January 2007 (UTC)
(after ec) Great film, but dreadful science ! Our article on Earth's gravity says:
If the earth was of perfectly uniform composition then, during a descent to the centre of the earth, gravity would decrease linearly with distance, reaching zero at the centre. In reality, the gravitational field peaks within the Earth at the core-mantle boundary where it has a value of 10.7 m/s².
As Weregerbil says, the decrease in gravity inside a sphere is due to the "shell effect" - inside a spherically symmetric hollow shell, the gravitational attraction due to the shell is equal in all directions, so the net gravitational force on an object inside the shell is zero. The shell theorem article contains a detailed mathematical derivation of this effect. You could observe the effect because objects in the hypothetical capsule would weigh less as it approached the centre of the Earth. Gandalf61 11:03, 8 January 2007 (UTC)

For convenience the earth is considered to be a point mass, therefore in calculations like this all its mass is located just at the centre of the earth. Gravitiy is proportional to distance from the centre, and I have forgotted exactly what my point is, but I think I have just disproved it. Or I might not have.Hidden secret 7 20:57, 8 January 2007 (UTC)

The Earth's gravity resembles that of a point mass if you're not inside the Earth. As soon as you descend a significant depth, gravity decreases for the reasons explained above. --Anonymous, January 8, 00:22 (UTC).

Gravity of the moon? ...the sun?[edit]

The discussion above leads me to wonder: What is the value (in Gs, in the vicinity of the Earth) of the moon's gravitational attraction? ...of the sun's gravitational attraction? It's obviously non-trivial since it leads to tides on the Earth's surface, but I've never noticed the value being stated.

Atlant 15:24, 8 January 2007 (UTC)

Well, let's see ... the distance to the Moon is about 64 times the Earth's radius, and its mass is about 1/80 of the Earth's mass, so the force of the moon's gravitational attraction at the Earth's surface is about 1/(80x64x64) of the Earth's surface gravity, so about 3x10-6g. The distance to the Sun is about 25,000 times the Earth's radius, but its mass is about 33,000 times the Earth's mass, so the force of the Sun's gravitational attraction at the Earth's surface is about 33,000/(25,000x25,000) of the Earth's surface gravity, so about 5.3x10-4g. So the Sun's gravitational attraction on the Earth is much greater than the Moon's (which makes sense, otherwise the Earth would be in orbit around the Moon instead of around the Sun), but both are miniscule compared to the Earth's surface gravity.
However, the Moon has a much greater effect on the tides than the Sun does because the tides are caused by the gradient of the gravitational field, not its strength. As our article on tides says: Though the gravitational force exerted by the Sun on the Earth is almost 200 times stronger than that exerted by the Moon, the tidal force produced by the Moon is about twice as strong as that produced by the Sun. The reason for this is that the tidal force is related not to the strength of a gravitational field, but to its gradient. The field gradient decreases with distance from the source more rapidly than does the field strength; as the Sun is about 400 times further from the Earth than is the Moon, the gradient of the Sun's field, and thus the tidal force produced by the Sun, is weaker. Gandalf61 15:54, 8 January 2007 (UTC)
As an aside of sorts, the gravitational effects of the moon are actually great enough to produce earth tides, up and down motions in the rocks themselves. These are on the order of an inch or so, but are measurable with Gravimeters and must be corrected for in gravity surveys for oil exploration, for example. Cheers Geologyguy 16:03, 8 January 2007 (UTC)
Thanks! Yes, I read the Tide article, but I was interested in the absolute magnitude of the force rather than the tidal effects, so thanks for the calculations. And with regard to earth effects, I understand (per a recent article in New Scientist magazine) that scientists are starting to believe that these tidal forces may serve as part of the ultimate trigger for earthquakes.
Atlant 17:05, 8 January 2007 (UTC)
I was told that the moon has 3 times the gravitational tidal influence of the sun in my Nautical Science classes. —The preceding unsigned comment was added by (talk) 17:37, 8 January 2007 (UTC).
If you want the absolute magnitude of the force, then the force that the Sun pulls on the Earth (and that the Earth pulls on the Sun by Newton's 3rd law), is around 3.5×1022 Newtons - roughly the amount of force needed to break a high-tensile steel cable around a mile or two in radius. The force that the Moon pulls on the Earth (and hence also that the Earth pulls on the Moon) is around 2.0×1020 Newtons. Richard B 13:34, 9 January 2007 (UTC)
Gandalf61, you're a bit light on the Sun's mass. The Sun is ~330,000 times the mass of the Earth, but somehow you've come to the right final answer for the gravitational field strength from the Sun. ;-) If you want to work out the tidal force, then you just need to work out the gradient of the field strength, which is proportional to the mass divided by distance cubed.
So the ratio between them is (using the numbers above);
Tidal force (Moon)/Tidal force (Sun) ~ Mass (Moon) * Distance (Sun)3 / (Mass (Sun) * Distance (Moon)3
Ratio ~ (1/80) * 25000^3 / (330000 * 64^3) ~ 2.3 Richard B 13:28, 9 January 2007 (UTC)

Work-Energy theorem[edit]

Is Work-Energy theorem valid in a non-inertial frame of reference?

Assuming you mean dEkin = F·ds , where F = dp/dt, I think the answer is no. See Special relativity, which gives formulas for kinetic energy and force.  --LambiamTalk 14:28, 8 January 2007 (UTC)
A reference frame is called non-inertial if it is undergoing some acceleration a relative to an inertial reference frame. The acceleration will give rise to an apparent gravitational field g=-a in the non-inertial reference frame. There will therefore be a gravitational term to the force, leading to a potential energy term in the energy equation: dEkin + dEpot = F·ds, where dEpot = m g dz, where dz is the displacement in the direction of the acceleration. This is just like the reference frame we live in on Earth, where there is gravity due to the nearby mass of the Earth. According to Einstein's general theory of relativity, such gravity has exactly the same effect as an acceleration of the reference frame. --mglg(talk) 21:12, 9 January 2007 (UTC)

work done by a force[edit]

I came across something which seemed peculiar to me - "No work is done by a force on an object if the object moves in such a way that the point of application of the force remains fixed."-Is this true?How? —The preceding unsigned comment was added by (talk) 14:28, 8 January 2007 (UTC).

I'd say no, that's false. Consider two rollers with a tube between them being pulled through the rollers and raised in height. The location of the contact between the rollers and the tube remains constant, yet the tube ends up higher, and thus with more gravitational potential energy, showing that work was done. If they meant that "the point of application of the force remains fixed relative to the moving object", we could disprove that with the example of a rocket. The force remains at the end of the rocket during the entire burn, but still results in work being done on the rocket, again as shown by it ending up higher, with more gravitational potential energy. StuRat 15:06, 8 January 2007 (UTC)
Yes, the statement is true—provided that you're careful about your definitions. The 'point of application' of the force must remain fixed relative to two points: the object itself, and a fixed external frame of reference. In the 'roller' example above, this condition doesn't hold, as the point of contact on the tube is being moved. In the 'rocket' example, choosing the rocket itself as a frame of reference doesn't make sense.
From a technical (some might say semantic) standpoint It falls out of the definition of work (see mechanical work for details and formulae), that requires force to be applied over a distance for work to be done.
From a common sense perspective, the quoted rule applies to 'static' situations, like a brick sitting on a table. There's obviously a force being applied to the brick by the table, and vice versa :gravity pulls down on the brick, the table resists the brick falling through it. There isn't energy being created out of nothing by this interaction; the brick and table don't get warmer, the brick doesn't levitate, etc. There is a force being applied to the brick, but the point of contact is fixed, hence no work is done. TenOfAllTrades(talk) 18:22, 8 January 2007 (UTC)
But in your example the object is still, do you have an example with a moving object ? StuRat 04:47, 9 January 2007 (UTC)
That was troubling me too, would a brick on a table, falling off a cliff count? Vespine 05:40, 9 January 2007 (UTC)
In general, with an inertial frame and no relativistic velocities, it's quite simply that \vec F\cdot\vec v=0 at all times. (\vec F can confusingly be the net force on the object or the force from one other object, depending on whether you want to say "No work is being done on this object." or "That object is doing no work on this one.".) This means that something in a circular orbit counts, because the force is in towards the planet or so and the velocity is around it. The trick is that it depends on your reference frame: if you are drifting by the planet in the plane of the orbit, you say it is doing work on the satellite, because the satellite is moving faster when it's moving the opposite way you are (relative to the planet) and slower the other way, so its kinetic energy is changing. It also of course works when \vec v=0: if you watch a train go by, you say the tracks are doing work on it to make up for losses to air drag, but I on the train say that the train is not imparting energy to the air (merely diverting an oncoming wind) and is just clinging to the moving tracks to not be blown backwards. (I also say that since the train is pushing on the moving tracks, it is doing work on them!) Finally, in order for the "no work" condition to persist, it must also be the case that \frac{\partial}{\partial t}(\vec F\cdot\vec v)=\dot\vec F\cdot\vec v+\vec F\cdot\vec a=0, where \vec a:=\dot\vec v is acceleration. This means that you won't see it regardless of your frame for gravity's effects on things falling at small altitudes: the gravitational force is constant (\dot\vec F=0) so the only term is \vec F\cdot\vec a, and that would only be zero if \vec a=0 since they'll both point straight down. (You might argue that at terminal velocity this is the case, but there \vec F\cdot\vec v\neq0 in the first place.) Does that clarify it at all? --Tardis 18:08, 9 January 2007 (UTC)

What is the antonym of feral?[edit]

What is the word that describes a wild animal that appears domesticated. This usually happens on an individual basis, like a deer you can feed out of hand. There are stories about wild animals that seemed tame, but then just take off for the wild again.

The word isn't taming, nor is it domestication. It is a rare, technical term. I saw it once in 'New Scientist', but I can't remember what it is for the life of me. Can you help?

Meredith15:52, 8 January 2007 (UTC)15:52, 8 January 2007 (UTC)~

Habituated? —The preceding unsigned comment was added by (talk) 17:38, 8 January 2007 (UTC).

That'll work! Thank you so much!

Gas Leak[edit]

What are some possible consequences of a city wide natural gas leak? Assuming also trace amounts of Mercaptan, other than the obvious smell of sulfur, which is unpleasent to say the least-- 16:03, 8 January 2007 (UTC)

A good place to start would be an MSDS for natural gas. (Here's one, in PDF.) This outlines some of the health and other hazards associated with natural gas. At moderate concentrations, natural gas is highly flammable; at very high concentrations it is an asphyxiant. TenOfAllTrades(talk) 18:26, 8 January 2007 (UTC)
Today's event bordered on mass hysteria. I have seen no proposed mechanism for a city-wide natural gas leak.
The temperatures were warm over the weekend and the river and sewers had that nice ripe smell they have in the summer. Normal, but a bit out of place in January. Evacuating office buildings and department stores and telling pregnant women to go home was absurd. -THB 04:09, 9 January 2007 (UTC)
I think something like that happened in 1992 in Guadalajara, Mexico, where gas leaked into the sewers and dispersed. I believe it detonated before it leaked out of the sewer throughout the town, but still killed around 200 people: [2]. It's not hard to imagine an even more serious event, especially if no odorant was added. StuRat 04:58, 9 January 2007 (UTC)


I know that bananas have alot of pottasium. But, what are the benefits or dangers of pottasium? —The preceding unsigned comment was added by (talk) 16:48, 8 January 2007 (UTC).

The article entitled potassium will tell you a lot about potassium; the section of that article entited "Potassium in nutrition and medicine" will probably be most helpful to you. DMacks 17:35, 8 January 2007 (UTC)

Clinical Physiologist.[edit]

I am awaiting notification as to whether I am successful in my job application for a position as a Trainee Clinical Respiratory Physiologist. I would like to know what kind of uniform i'd wear in the hospital. Would it be scrubs, normal clothes, white coat etc.

Thanks. Christopher. —The preceding unsigned comment was added by (talk) 18:37, 8 January 2007 (UTC).

It is a matter of local custom. What did they tell you at the hospital? What were the other respiratory physiologists wearing? alteripse 23:13, 8 January 2007 (UTC)
Whatever is the norm at the facility where you are working. Generally, scrubs or street clothes with a lab coat. Trainees or students may have to wear distinguishing uniform such as a short lab coat or a different color of scrubs. -THB 04:12, 9 January 2007 (UTC)

Darwinism; the human race compared to other animals[edit]

As I understand it, Darwin explains the existance of so many species by a very slow process of evolution whereby the fittest survive. Did he, or any of his successors postulate any explanation for the fact that, although all species appear to have changed over time, the changes in homo sapiens and the capacities that have been developed as a result of them seem so much more spectacular? Put another way, why has no other species developed the use of language, artistic abilities etc etc beyond a rudimentary level?

This is science, so most of it is random chance. And no other animals have much chance to develop art &c, as they are too busy trying to survive.Hidden secret 7 19:39, 8 January 2007 (UTC)

Some other animals have some kind of language like: Birds, Dolphins and Whales. --helohe (talk) 19:55, 8 January 2007 (UTC)
Also, the development of culture is fairly recent in evolutionary time, and once it happened our species quickly achieved a huge advantage (advanced language and technology). In short, it seems spectacular because we were the first ones who got this far, and because it happened just a while back. — Kieff 21:14, 8 January 2007 (UTC)
The chance of two species simultaneously developing high intelligence is very low. Adding to what Kieff said, if another species were to be the first to develop language skills, don't you think someone from that species would be asking the exact same question? --Bowlhover 21:15, 8 January 2007 (UTC)

I think your question is this. Human development accelerate due to positive feedback so how come development of other animals did not enjoy this positive feedback? I believe that it is the development of language and writing that give humans the advantage of positive feedback. If other animal species develop language and writing then they will also "enjoy" positive feedback on their development.

As for why other animals did not develop language and writing, I believe it is because of their body structure, mainly their voicebox and the hands. It is a complete fluke of environment that lead to the development of a suitable type of voicebox and hands for human beings. 23:59, 8 January 2007 (UTC)

Why don't snails have wings? Why don't frogs have beaks? Why don't humans have eagle eyes? Why don't worms have four-chambered hearts? We can go on and on about why certain species don't have specific traits. I think the reason primates reign is because we've become so powerful that we've impeded whatever development other species have towards becoming more specialized. In other words, only one kind may prevail, us primates, at the expense of other animals. And who knows, if we let dolphins live they might develop high intelligence like ours in a few million years.

But these are only elementary speculations of mine; check out this part of Darwin's Descent of Man, where he talks about why humans develop complex language while other species lack it:,M1 Read the entire chapter if you like to understand it better.

Humans aren't the only artistic animals, others include bower birds. StuRat 04:42, 9 January 2007 (UTC)
Insects and fish are far more 'successful' without language, there are many more per species than humans. They are successful in terms of the number of copies of their genes are around. In evolution species fill a niche, i.e the working towards the best solution in their particular environment. There is no "perfect" ultimate goal of evolution, and if there is it isn't necessarily complexity and language. Just think for a minute what would happen if there was another species that had the same goals as us and the same intelligence and language skills. We have come close enough to wiping out our own species. Intelligence, art and language are successful in our environment (eating plants, animals, living in varied environments and making shelters etc), and there is no room for any other species to take over it. If an animal gained similar traits as us, they would compete directly with us, we would kill them before they had a chance to evolve. In this way evolution makes species that are not so similar as to compete that directly. 10:12, 9 January 2007 (UTC)
Darwin'sDescent of Man goes into just this issue at length. He primarily argues that you can see versions of any "uniquely human" trait in many other animals to lesser extents, and that nothing humans have are actually "unique" so much as exaggerated. An analogy—not Darwin's—might be that all animals have noses, though dogs can smell much better than most. We can recognize that the dog's nose evolved into a highly specialized organ due to some set of various evolutionary twists and turns; we don't really doubt that this is possible, since it seems pretty plausible. The human brain, then, would be similarly understood as a specialized organ, at least if we were not so 1. relatively clueless about how the brain works (even still), 2. vain about our own thinking abilities (which we elevate far higher than they probably ought to be, in the evolutionary scheme of things, and we also over-value brain power for a variety of cultural reasons, whereas evolution really does not care how you solve the fitness problem). -- 15:37, 9 January 2007 (UTC)

Just droppin' objects[edit]

I'm pretty ignorant. So I need help understanding what the deal is with falling objects all falling at the same rate. While I know and can see this to be true (doing some 'experiments' of my own), I wonder why. If all objects fall at the same rate without the influence of air resistance, when why are some of them heavier than others? If I put an object on the scales it might be 'pulled down' by Earth's gravity more or less than another object. So it would seem that the 'hardness' of the force on the object does not affect the speed that it falls at. That's pretty counterintuitive, as if I shove an object in a gravityless (?) environment hard it'll go faster than if I tap it gently (that'd probably a better analogy if I were tugging on an attached string hard or softly, but whatever). So what's the hole in my understanding? Vitriol 19:35, 8 January 2007 (UTC)

Well air resistance of course is a force that retards falling in an atmosphere, much as friction retards sliding of something sliding on the ground. Air resitance can be so great that a falling object reaches a terminal velocity, and its rate of fall does not increase any more. We do not really understand gravity. All we can do is measure it and form theories or laws about it, like Newton's law of gravity of Einstein's theory of gravity. The weight does not affect the speed in a vacuum, you are correct. Aristotle felt that the weight would affect the speed, and heavier objects would fall faster. Galileo tested this (by rolling objects on an inclined plane, not by dropping things from the Tower of Piza as the popular myth goes). Galileo found all objects fall at the same rate. So...there you have it. We do not know why really just that it happens. --Filll 19:41, 8 January 2007 (UTC)
The trick is that you have to account for mass. Recall one of the formulations of Newton's Second Law of Motion: F = ma (F = force, m = mass, a = acceleration). Rearrange and you get a = F/m; that is, to get the same acceleration of a large mass (compared to a smaller mass) requires a correspondingly larger force. Conveniently, the gravitational force scales precisely with the mass (inertia) of the object, so all objects accelerate at the same rate under the influence of gravity.
Now, there's a much more subtle underlying question that physicists haven't been able to answer satisfactorily here. You can measure mass in a couple of different ways. Gravitational mass is a measure of how strongly an object attracts other matter through the force of gravity. Inertial mass is essentially a measure of how strongly an object resists acceleration. Why is it that these two ways of measuring mass always work out to be equivalent? TenOfAllTrades(talk) 19:52, 8 January 2007 (UTC)
See, I don't think I'm understanding still as what I can glean from what you say a object with a larger mass is pulled on harder by gravity to get it moving in the first place... and gravity doesn't pull on some things harder than others. Doesn't it? Vitriol 20:02, 8 January 2007 (UTC)
Yes, gravity DOES "pull harder" on heavy objects than on lighter ones, according to Newton's Law of universal gravitation. The gravitational force exerted on one object by another is linearly proportional to the mass of the object. -sthomson06 (Talk) 20:53, 8 January 2007 (UTC)
Think about it like this: gravity pulls harder on objects with more mass. But objects with more mass are also harder to accelerate. From the equation F=ma, imagine if you multiplied m by 3 and also F by 3. 3F=3ma, so there's no need to change a. --Bowlhover 21:12, 8 January 2007 (UTC)
Actually, what Vitriol has asked about is a very beatiful and profound physical concept - the equivalence of 'inertial' mass and 'gravitational' mass. The fact that gravity pulls just hard enough on any mass to accelerate it at the same rate as all other masses is the profound insight that Einstein had which led him to realize that gravity is a geometrical phenomenon. Cool stuff. --Bmk
It's 'cool', eh? Thanks for the responses, forks. Vitriol 01:39, 9 January 2007 (UTC)
Great discussion; I don't think I've ever thought about things this way before. Does this all work out to be another way of expressing our lack of a unified field theory? Is it the fact that only gravity, of all the forces, depends on the very quantity that controls acceleration that both allows it to be interpreted geometrically and sets it apart from the other forces? --Allen 03:32, 9 January 2007 (UTC)

N.H. Horowitz[edit]

I have found paper after paper by this guy in biology and exobiology etc. He is a professor at Caltech. Is he famous ? Does he need his own biography?--Filll 19:37, 8 January 2007 (UTC)

This piece on Norman H. Horowitz should help you decide. Wolfgangus 21:40, 8 January 2007 (UTC)

I-V characteristics of Josephson junctions[edit]

Why do people investigate the I-V characteristics of Josephson Junctions, other than for the fact that the I-V curves are not what you would expect from a normal semiconductor junction? i.e. what kind of physical impact / application do the I-V characteristics have say, for example, in SQUIDs (Superconducting Quantum Interference Devices)? --RaGe 20:43, 8 January 2007 (UTC)

For a while, it was hoped that Josephson junctions might replace transistors as the basis for the high-speed electronics used in computers. IBM did a ton of research into this.
Atlant 13:50, 9 January 2007 (UTC)
cheers for the responce --RaGe 00:10, 12 January 2007 (UTC)

Looking for scientific journals[edit]

Today on new pages I ran across someone who has come up with a slightly different theory of the origin of the solar system. He was trying to use Wikipedia to publish his original thought. I prodded his article and explained to him why it doesn't belong on Wikipedia. Now he'd like me to suggest other places that might be more receptive. I'd like to suggest he try some scientific journals but don't know any specific journals to point him towards.

What are some names of journals where he might be able to try to get his theories published? ~ ONUnicorn(Talk|Contribs)problem solving 21:13, 8 January 2007 (UTC)

Try reading scientific journal? :) He can try[3], or Physical Review D[4]. X [Mac Davis] (DESK|How's my driving?) 21:18, 8 January 2007 (UTC)
Thanks for the quick response. I'll suggest those. :) ~ ONUnicorn(Talk|Contribs)problem solving 21:23, 8 January 2007 (UTC)
You could also try spiked com 00:35, 9 January 2007 (UTC) NOTE: SPIKED COM APPEARS TO BE URL SPAM --Wjbeaty 00:37, 10 January 2007 (UTC)
And The Edge. AKA Edge Foundation. Anchoress 03:52, 9 January 2007 (UTC)
See List_of_scientific_journals#Astronomy_and_astrophysics and List of scientific journals in astronomy. StuRat 04:35, 9 January 2007 (UTC)

relation of the sun and wind[edit]

hello, i would like to know the role played by the sun on creation of wind on earth thank you, anu —The preceding unsigned comment was added by (talk) 01:41, 9 January 2007 (UTC).

Have you tried reading the article wind? It has quite a bit of information in it. -- 02:08, 9 January 2007 (UTC)
I was going to go ahead and add a little capsule definition anyway, but I clicked on that article and the opening paragraph is very good! Vespine 02:41, 9 January 2007 (UTC)
I've just evaluated that article, and found it to be quite acceptable, as well. In other words, I've just passed wind. StuRat 04:32, 9 January 2007 (UTC)

Propranolol side effects[edit]

Is there any evidence that this Beta blocker can cause chronic itching all over the body in some patients suffering from hypertension?--Light current 01:56, 9 January 2007 (UTC)

Yes, itching Appears to be a known side-effect, especially upon exposure to light. DMacks 02:00, 9 January 2007 (UTC)
Ah no. My itching is where the sun dont shine (under my clothes). 8-|--Light current 02:02, 9 January 2007 (UTC)
There's your answer then, just head for the nearest nude beach. StuRat 04:28, 9 January 2007 (UTC)

Escherichia coli[edit]

Specifically how do virulent strains of E. coli cause the well-publicized complaints (bloody stools, diarrhea)? I was looking the question over, and couldn't really find any specific steps. bibliomaniac15 02:01, 9 January 2007 (UTC)

Have you read the e. coli article? This section seems to answer your question. Anchoress 02:09, 9 January 2007 (UTC)
This article is getting a bit old, but it describes some of the virulence factors such as shiga toxins that will damage and kill intestinal cells. --JWSchmidt 02:20, 9 January 2007 (UTC)

Horst Tube Submarine[edit]

Does any one know where I can get info on the Horst Tube, used in submaries by the Germans in ww11. This tube completely covered the propellor of the submarine, to increase speed or thrust. —The preceding unsigned comment was added by (talk) 02:31, 9 January 2007 (UTC).

Are you maybe thinking of Kort nozzles? 7:05pm, 8 January 2006 (PST)

Sounds also like it could be the UW version of Ducted fan.--Wjbeaty 00:32, 10 January 2007 (UTC)

Electromagnetic Radiation from the end of coaxial cable[edit]

If an electromagnetic wave is travelling towards the open end of a coaxial cable, what proportion of the incident wave is radiated from the end. We may assume that the cable Z0 is 50R and the impedance of free space is 377R. THis is not a homework question as I finished my formal education many years ago. I try to learn from WP now.--Light current 02:46, 9 January 2007 (UTC)

Caps and Baldness[edit]

Can wearing hats/caps give you a higher chance of baldness in the long run? PitchBlack 02:46, 9 January 2007 (UTC)

See Fred Dibnah —The preceding unsigned comment was added by (talk) 02:50, 9 January 2007 (UTC).
No, check out the baldness article. It says wearing a hat should not cause traction alopecia, which is the only cause of baldness through physically pulling the hair. Normal hair loss is genetic and caused by hormones (described well in the article). --liquidGhoul 03:06, 9 January 2007 (UTC)

A fungus among us[edit]

OK, thanks. Another question. Why is it that mold easily grows on bread when it's closed in the pantry, and not when it's in a open bag in my room?(I'm trying to grow mold and bacteria, but all it does is get hard) PitchBlack 03:13, 9 January 2007 (UTC)

When it's in a closed container, it retains the moisture needed to support the growth of mould. Mould is another term for fungus which is what actually forms visible mass on bread (green/white) rather than bacteria. FYI; it's customary to create a new heading for a new question or else a lot of people that may be drawn to mould questions (freaks!) might miss it, being put off over the apparent talk of 'caps and baldness'. :) Why are you trying to grow fungus anyway? Green fungus should be kept away from people with penicillin allergy in case its penicillium --Username132 (talk) 03:58, 9 January 2007 (UTC)
I've added the heading. StuRat 04:26, 9 January 2007 (UTC)

Yeah, my mistake. I wanted to post quickly to get an answer, but I also know you can't double post. PitchBlack 08:59, 9 January 2007 (UTC)

Weird science...[edit]

I eliminated strait glucose from my diet well over a year ago by switching to Sweet & Low and a store brand of Aspartame. I “discovered” that if I mix the two in a ration of 3 packets of Sweet & Low to 5 packets of Aspartame that I get sweetness even more intense than glucose except, but maybe not, pure cane syrup or HFCS. Its so intense that I can even mix it with plain sour yogurt and the sweetness takes over and rules. My question before I get side tracked is why is it that when I add this combination to coffee and then sprinkle some cinnamon in that I get a brown oozy slime in the bottom of the cup like extremely nasty sickening snot? What reaction causes this slime and why is there so much of it? I guess ouster lovers could suck it right down but to me it is disgusting. What is it??? -- Barringa 04:09, 9 January 2007 (UTC)

Is there by any chance any milk or cream in the coffee ? If so, perhaps you have caused it to curdle. In which case, I agree, that's whey cool. StuRat 04:19, 9 January 2007 (UTC)
No creamer or lactose derivative of any kind. Its Folger 100% Columbian coffee + Aspartame + Sweet & Low + cinnamon + less than 10 seconds and ...ha-choo! ...a couple of tablespoons of slimmy goo right in the old cup of coffee! -- Barringa 06:25, 9 January 2007 (UTC)
What color is your blob? Does that suggest it's mostly made of sweeteners, or that it has a lot of cinnamon (or coffee components) in it? What happens if you repeat your experiment with cinnamon but omit the sweeteners entirely? What happens if you use just hot water and cinnamon, with and without sweeteners? What order are you adding the sweeteners and cinnamon? If the cinnamon floats, then adding sweeteners after it could form a mixed-solids surface layer that sinks; try dissolving the sweeteners first. In my experience, powdered cinnamon does not dissolve in coffee, but floats in a thin layer on the surface at first and sometimes winds up as a gelatinous mass by the end. Same with powdered cocoa actually. DMacks 06:37, 9 January 2007 (UTC)
The dark brown color is obviously the wet cinnamon and possibly coffee. The goo is the part I'm trying to identify. Since ground cinnamon is nearly 100% dietary fiber I would assume it is for this reason sticking to whatever the goo might be. I can speculate that it is some sort of reaction of the sweetners with the fiber but was hoping there might be a chemist who already knew. Barringa 08:56, 9 January 2007 (UTC)
You have four ingredients for your goo recipe. Could you experiment and see whether perhaps some smaller subset already undergoes gooification (for example leaving out the coffee, or the Weet & Slow?).  --LambiamTalk 11:59, 9 January 2007 (UTC)
Sounds like a fine experiment. Try the process of elimination, and dump each batch through a coffee filter to extract the goo. Silly Putty , penicillin and saccharine were discovered in similar lab accidents. Cinnamon is believed to have medicinal properties. Be cautious about consuming the results of experiments. Edison 17:12, 9 January 2007 (UTC)
Teflon too was serendipitously discovered.  --LambiamTalk 22:39, 9 January 2007 (UTC)

Noodle soup[edit]

I once heard a counter-intuitive anecdote about making noodles for noodle soup. In Japan, a good noodle factory may add more water to the noodles if the noodles are for take-out use. Possibly, noodles with less water would absorb too much water and become soggy in less time. Is it true? If you have a pasta-making machine you may want to try it. -- Toytoy 04:35, 9 January 2007 (UTC)

If you're asking whether the practise makes sense, then I'd say it does to a certain extent. Uncooked pasta is usually covered in a fine layer of pasta "dust". When the noodles go in the water, some of the dust gets washed right off of course, but some will stick to the noodles. Nothing wrong with that - it helps sauce to stick to the noodles too - but if the noodles aren't being consumed right away, the now gooey dust will start to get everything soggy. Rinsing the noodles off can get rid of even more of the starchy dust, but will also usually chill the noodles, which will also make them sticky, defeating the purpose. Boiling the noodles in a larger quantity of water would be ideal because it will be able to absorb more of the pasta dust without adversely affecting the noodles. Matt Deres 16:49, 14 January 2007 (UTC)


At school we frequently tackle momentum probllems using the general equation: mAuA + mbub = mava + mbvb.

To work out the result when two bodies collide using this equation, if they do not coalesce, you need to know something about the result of the collision, such as the velocity of one of the bodies. Knowing only the m and u values, is there a way of working out exactly what type of collision it is, and what speeds the two bodies will move off at?

Many thanks! -- 07:50, 9 January 2007 (UTC)

Generally not. The exception is for very small particles, such as atoms, where the collisions are elastic; as kinetic energy is conserved as well as momentum, using the formula for KE (1/2mv2) you can work out
1/2mAuA2 + 1/2mBuB2 = 1/2mAvA2 + 1/2mBvB2
simultaneously to find vA and vB. Unfortunately, this does not work for everyday macroscopic objects, because when they collide, they deform, which looses energy to the surroundings as heat. Laïka 08:05, 9 January 2007 (UTC)
...or you need to know the coefficient of restitution, which is the ratio of the difference in velocities after collision to the difference in velocities before collision. It is number between 0 and 1; it takes the value 1 for perfectly elastic collisions and 0 for perfectly inelastic collisions. Gandalf61 11:22, 9 January 2007 (UTC)
It works fairly well for objects that hardly deform under normal collisions, such as billiard balls when playing pool, or a penny "shot" at another penny. Here is an interesting, not well-known consequence of the two equations combined if the masses of the two objects are the same: ma = mb = m > 0. We can then divide out this common factor from the two equations:
ua + ub = va + vb;
1/2ua2 + 1/2ub2 = 1/2va2 + 1/2vb2.
Note that in the simplified momentum equation the velocities represent vectors. Squaring both sides (using inner product as the multiplication operation) gives us:
ua2 + 2uaub + ub2 = va2 + 2vavb + vb2.
Now take half of this and subtract the simplified energy equation, resulting in:
uaub = vavb.
So in an elastic collision between two objects of the same mass the inner product of their velocities is preserved. When one of the two objects was at rest, its initial velocity is zero, so uaub = 0, and therefore afterwards vavb = 0. So if a billiard ball hits another identical ball that is at rest, one of the two will be at rest afterwards, or they will take of in directions that form a right angle.  --LambiamTalk 11:52, 9 January 2007 (UTC)
Noone's mentioned it yet, but you should be aware that your "general equation" is merely a restatement of the Law of the Conservation of Momentum applied to interactions involving two "particles". -- 19:12, 12 January 2007 (UTC)