Wikipedia:Reference desk/Archives/Science/2011 September 24

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September 24

Energy

i just saw this question on a discussion page, if energy cannot be created nor destroyed, where did it came from?

It has always been. At least as far back as the Big Bang. Modern science can't really even begin to speculate on what, if anything, existed before that. APL (talk) 03:20, 24 September 2011 (UTC)

To expand on that slightly, matter and energy can be exchanged in certain cases, but the total matter and energy in the universe is the same as it ever was. APL (talk) 03:21, 24 September 2011 (UTC)

You can read Big Bang and Timeline of the Big Bang and Planck epoch and so forth ... which kind of dance around the main point: we don't know. There always has been energy and always will be. Wnt (talk) 03:30, 24 September 2011 (UTC)

In general relativity, energy is not really conserved in general, and according to inflationary cosmology the energy of the early particle soup essentially did appear out of nowhere, with the help of general relativity. More broadly, physical principles (like energy conservation) aren't given to us engraved on stone tablets. We deduce them from experiments we do in the here-and-now, but we don't know if they're valid in absolutely every circumstance. -- BenRG (talk) 04:49, 24 September 2011 (UTC)

superfluidity react to Neutrino hypothesis

very long and totally unreadable list of incomprehensible questions
The following discussion has been closed. Please do not modify it.
How hydrogen Absolute zero superfluidity react to Neutrino? neutrino travel near speed of light if accelerated infinitly increase in mass? could massive neutrino webs be used to gather their particals for energy? fold space superfluidity of anti matter (?dark matter)? graviton of gravity yet has force to pull photons without mass itself emitted powerful gamma ray jets? do gamma ray column ever are parallel with another jet and collide? would this travel faster then light? the universe is curved were is its centre and does it have a gamma ray jet? are there super symetrical forces surrounding the universe one universe being symetrical to the next and particale infintly symetrical in mass interger or fractal, both ? or nothing beyond its perameter and finite? do all objects in the universe travel at one constent relative to the big bang as other mass moves or are all things static, relative to other moving objects? is time a mesurement of one thought to the next and it is humans inability to use sensury perseption to notice? Is there 5 or 11 dimention then would it be possible for any number of dimentions to exist. If all things are made of two dimentional particals they can make up anything could a single string be a unverce, a person, a star and if a human brain are made up of the universe is that why we have imagination, then all we think, imagine exists as some string, would this be a fact if energy can not be destroied or created changed or redirected does that apply to all particals? Before a chemical reaction between two particals occurs it is not a molacule itself or the other what is it does it exist as anything? If there is zero its angle would be nothing; does nothing exist? Regardless of any mathematical equation; explanation, metaphysical, religeus ,quantum. the expressions are diffrent yet it seems that their solution to the system is an assignment of values to all the unknowns so that all of the equations are real, conclutions the same; is their a formula for all that we concieve becomes reality? Even if it contradics physics with diffrent formulas of the orgin of reality; is there abstract formula were our law of physics do not function the same values and particals do not have the same properties? Is reality just a matter of perception? If physiologicly we are made of strings and have imagination would that mean that our thoughts, dream could become what is considered sensery perception reality,(like miricals)? Do we exist on some level of a reverberating string like dimention where anything probable or not all happen simutaniosly ? It just our sences absolute threshold to notice what is around us and do we ignore this human potential and just mirror quantitivly, qualitivly? without the ability to imagine would we ever evolve, one nerve net react to stimuli of simple life? Similar to boson gauge? Is it nerves ,brain imagined the next step reacted evolved by ingesting a amino acid and replicated itself adapting one gene at a time why we evolve? To understand that this is all placed in thought; the entire universe, trilions or infinate (for every string in the brain) and each mind of every person as though we all share one? Would naturaly we evolve with our imagination to create miricale? no longer phenominon being made entirerly of strings a part of many facts that build reality? If knowlege is built on knowledge, based on more resent finding of quantum physics these formulas ancient; human know this as a fact? Being so why hide reality from the world considering there are more pros then cons? — Preceding unsigned comment added by 207.6.211.175 (talk) 01:04, 24 September 2011 (UTC)

Defense against positrons

Okay, maybe it's best if I just came out and asked about what I'm specifically looking for. I'm writing a story where I've got a stream of near-light-speed positrons being used as a weapon. I'm trying to come up with some kind of defense against said weapon. Thus far, thanks to the previous question I asked, I've got the following possibilities:

1. A strong and properly angled magnetic field, which uses the Lorentz force to deflect/curve the positrons away from their target;
2. A positively-charged electric field - possibly just from a big mass of protons - which will repel the likewise positively-charged positrons;
3. A stream of electrons, aimed precisely at the thing generating the positrons, with the intention of meeting the positrons in flight and annihilating them ahead of the target. (Keeping in mind, though, that as we're talking about very tiny particles traveling very fast, I don't know how effective that would be.)

Does anything I just mentioned have any bearing whatsoever on reality? Am I at least close to something scientifically plausible? If not, could you guide me in a better direction?

Thank you very much for your time. --Brasswatchman (talk) 03:30, 24 September 2011 (UTC)

None of those things will work if the positrons are moving too fast -- whatever you do needs to overcome their kinetic energy. Even intercepting them and annihilating them will result in a beam of high-energy gamma rays shooting straight toward you. Looie496 (talk) 03:37, 24 September 2011 (UTC)

Wait a second, though. Doesn't the Lorentz force actually increase in proportion to the velocity of the incoming particle? Or am I reading that wrong again? --Brasswatchman (talk) 03:42, 24 September 2011 (UTC)

How high energy and how many positrons? Until you get to really high energies positrons really have very little penetrating power. You could stop them with a several feet of air or a few inches of water / brick. They'll annihilate into gamma rays which could be a worse risk than the positrons themselves depending on how many of them there are. Dragons flight (talk) 04:41, 24 September 2011 (UTC)

It is useful to know the radius of the circle on which a positron will move in a (homogeneous) magnetic field. The formula is

$r={\frac {p}{e\cdot B}}$

where p is the momentum of the positron, e is the charge of the positron and B is the magnetic flux density. In the low-speed limit the momentum is just the product of mass and velocity, but for speeds close to the speed of light (denoted by c) you need the relativistic formula:

$p={\frac {m\cdot v}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$

Expressing the momentum in another way, in terms of kinetic energy (E) instead of speed:

$p={\sqrt {{\frac {E^{2}}{c^{2}}}+2\cdot E\cdot m}}$

For the highest values of B that are currently technically possible, see Electromagnet#High field electromagnets

Icek (talk) 14:21, 24 September 2011 (UTC)

So, basically, if I've run through the math correctly here - for a 1000 Telsa magnetic field, the distance moved by the positron by the Lorentz force is on the order of microns. Yeesh. Do I have that right? --Brasswatchman (talk) 19:16, 24 September 2011 (UTC)

Um, I haven't checked your arithmetic, but I think you're misinterpreting the answer. If you got the right number, then it does not mean that the positrons would be deflected by only microns. It means they would travel in a circle whose radius is only microns. That is, the small answer means they would be deflected very strongly, not very weakly as you seem to have interpreted it. --Trovatore (talk) 22:03, 24 September 2011 (UTC)

That... makes quite a bit of difference then, doesn't it? :) That works, then. Thank you! --Brasswatchman (talk) 23:35, 24 September 2011 (UTC)

You seem to simply use p = m*c. If you look at the relativistic formula, you can work out that this would be the real momentum if the speed would be c/sqrt(2). That seems like pretty low-energy positrons. Their energy would only be 212 keV. The highest energy man-made positron beam was at the Large Electron–Positron Collider at 104.5 GeV, that would translate to a radius of about 35 cm at 1000 Tesla (but that was a very large machine). High-energy positrons will also create a lot of synchrotron radiation in a magnetic field, and you would have to shield against that. Wnt's suggestion of just using something massive makes sense, as you have to use it anyway due to the synchrotron radiation (the synchrotron radiation is emitted in all directions in the plane of gyration, and if you let the positrons impact on matter there will be bremsstrahlung which will at least be preferentially emitted toward the direction the positrons were coming from). Icek (talk) 21:48, 24 September 2011 (UTC)

You're correct. Sorry, was just simplifying the math for myself so I could try and get a basic if inaccurate idea of what the effect would be. Either mass or a very strong magnetic field would work as a solution, then. Radiation is less of an issue for me, since I was thinking about this weapon in the context of an unmanned weapons platform. (Yes, I know that radiation does affect computers and machines; but at least it's a bit more plausible that they could be engineered to resist those kinds of stresses than a manned spaceship or station.) Thank you very much for your time, and for all the effort you've put into instructing me. I very much appreciate it. --Brasswatchman (talk) 23:35, 24 September 2011 (UTC)

You could use an electric or magnetic field to gently nudge them around and back at the source, but only if you can, say, set up something on the order of a particle accelerator out in space (around the size of the one accelerating them in the first place, that is). Doing this in a hurry would seem to require quite a set-up.

If you have any access to mass, I'd say that's your answer. Throw a brick out at the beam and (assuming it's strong) it'll blow to smithereens, and the vapor/dust thus created will screen a large area, at least momentarily, so after that your enemy can't just fan the beam around your settlement at will. Throw a large number of bricks and he'll be left heating a dust cloud in space with no real prospect to get through to you, I think. Wnt (talk) 14:37, 24 September 2011 (UTC)

An electromagnetic field would be your best bet. But like what someone else said, if their energy is too high, they will come through. Just posit an immensely powerful electromagnetic field. ScienceApe (talk) 18:23, 24 September 2011 (UTC)

Okay. What about the second possibility I mentioned? Putting a positive electrostatic charge on a surface in the path of the beam, for instance? Would that have much influence at all, or is the kinetic energy in this case simply too great for it to have much influence? --Brasswatchman (talk) 19:16, 24 September 2011 (UTC)

So far I don't see enough scientific context in the question to be able to answer it. How near light speed are you talking about? The difference between 0.99c and 0.999c is greater than the difference between 0 and 0.9c. It makes all the difference in the world how much energy the particles actually have. Secondly, unless you are using this "weapon" in a near vacuum, then the whole notion of them being positrons is moot. In the presence of air (or anything else) low-energy positrons annihilate into gamma rays, while high-energy positrons will scatter into showers of secondary particles. Either way, the only place you'd have a pure positron beam is in a vacuum. Hence it matters what environment the beam travels through in order to determine what kind of shielding is actually necessary. At the moment it just sounds like a very contrived plot device. If your weapon is going to be pseudo-scientific, then I'm not sure why you are looking for a scientific defense. Dragons flight (talk) 23:09, 24 September 2011 (UTC)

Let's say I am talking about a vacuum weapon, as in space-based. So the mass shielding suggested before does work for me; I'm just looking for options, that's all. --Brasswatchman (talk) 23:35, 24 September 2011 (UTC)

Just wanted to thank everyone who responded to this thread again. You've been a big help. --Brasswatchman (talk) 23:36, 24 September 2011 (UTC)

UARS: the falling, burning re-entering satellite

The UARS satellite should have reentered, but there is no update, more than one orbit past the re-entry time NASA picked as most probable, plus or minus a few hours.. Does NASA, or the various world powers, have radar to actually track a satellite, or do they wait for reports from amateur astronomers, commercial airline pilots, commercial shipping, Inuits, or African villagers who might have seen or heard something? The US and the other world powers are supposed to have the capability to track things in space in real time, to detect nuclear attacks, for instance. Edison (talk) 04:48, 24 September 2011 (UTC)

The last update had it falling between 3:45 and 4:45 UTC. Yes, they can track it. Dragons flight (talk) 05:04, 24 September 2011 (UTC)

NASA web page, if anyone is interested. Mitch Ames (talk) 06:07, 24 September 2011 (UTC)

... and an update therefrom ... "NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty."

The re-entry seems to have been chaotic (in the sense of there being too many unpredictable variables to calculate accurately), but at least it seems to have been over the sea. Dbfirs 08:45, 24 September 2011 (UTC)

NASA was able to rule out only one continent, North America, as a place the satellite might land.[1] In other news, see this lovely video from Alberta.[2] ;) After all these nimble flips I'm inclined to give the satellite a 9, provided it stuck the landing. Wnt (talk) 14:47, 24 September 2011 (UTC)

It was under 130 km altitude perigee in the South Pacific shortly after it passed over New Zealand around Midnight Eastern. That would have had to have snagged it, the air is just too dense. 208.54.86.178 (talk) 16:30, 24 September 2011 (UTC)

The latest reports are still inferential. They think it fell in the Pacific, because it's altitude was dropping. and it did not seem to have reached North America. They have not reported any actual radar measurements of when and where it reentered. There appear to be spots on Earth where they can measure the apogee and perigee and location of orbiting objects. but there are also apparently large gaps, somewhat worrisome when ballistic missile subs or surface ships might launch from anywhere. Satellites looking down might be able to detect launches. NASA was relying on "amateur satellite watchers," who failed to see it, so by inference it fell in the Pacific. Recent news reports, [3], say they are hoping for reports from airliners or ships of fireball sightings. If someone like the North Koreans fired an ICBM at the US, would they be similarly unable to track it by radar? Edison (talk) 03:39, 25 September 2011 (UTC)

Yes, they would not. Nobody has missile detection capability good enough to keep strategic defense command locations outside mountains. At Saturday the 24th at 04:05 UT, UARS' orbit was in perigee at 3.3 degrees North by 159.9 degrees West at an altitude of 126.1 km. That was the first time it was under 140 km. There's no way it could have continued from there. 69.171.160.56 (talk) 07:40, 26 September 2011 (UTC)

Why don't plants have white blood cells?

Are there any plants that have recruited bacteria or single cell animals to patrol themselves as a natural part of their existence?

No. Plants do not have an adaptive immune system, though a lot of plants have coopted insects and whatnot as defenses, most notably ants. Plants only have an innate immune system (which can also be found among animals), they use defensive chemical warfare instead. It's the reason why so many plants are good sources of antibacterial and antiviral chemicals.

Plants are also a bit more resistant to injury than animals, and they have a greater regenerative capability. If they detect an infection, they isolate it by killing their own cells surrounding the site before it spreads (hypersensitive response). They then start producing messenger chemicals that in turn stimulate production of defensive chemicals in other uninfected parts of the plant at the same time (systemic acquired resistance). For larger attackers, they can also stimulate another response which not only triggers the production of defensive chemicals in the individual plant, but in surrounding plants as well. This includes production of poisons and whatnot against insects and larger herbivores.

See Innate immune system#Host defense in plants and Plant disease resistance.-- Obsidi♠n Soul 08:54, 24 September 2011 (UTC)

Oh and in terms of symbionts and commensals, they do play a part in plant defense. But it's all rather indirect and certainly not internal. The area of study is known as biological control of plant pathogens and is of great interest in agriculture. This usually involves symbiotic fungi or bacteria in the plant roots (and virtually every plant has a great variety of them, some plants barely survive without like orchids).-- Obsidi♠n Soul 09:21, 24 September 2011 (UTC)

I guess (as a non-biologist) that the key here is that this particular form of symbiosis or whatever it is requires circulation, whereas plants draw their fluids from the ground and move them one way. For something like white blood cells to work, they would need a way of moving within the plant. Moving up would be easy, but for moving down they would probably require a lot of energy. This would also require some way of signalling where to go, and it's not clear to me how that would work in a plant context. Hans Adler 09:40, 24 September 2011 (UTC)

Plants have a sort of adaptive immune system, and manage to circulate their counterpart to antibodies through plasmodesmata - namely RNA interference. The distinction is that this acts at a point later in the viral life cycle: not on the encapsulated virus outside the cell, but on its genetic material as it seeks to take over the cell. As that article explains, humans might have the same thing, but evidence has been elusive. Wnt (talk) 14:21, 24 September 2011 (UTC)

RNA silencing is new to me. :D But yeah I suppose it's adaptive. It's quite different from animal protein-based adaptive immunity though, and by its very nature, purely antiviral.-- Obsidi♠n Soul 20:57, 24 September 2011 (UTC)

Was Einstein wrong?

Was Einstein wrong in claiming that nothing can travel faster than the speed of light? --DinoXYZ (talk) 08:33, 24 September 2011 (UTC)

See the previous thread on this: #FTL neutrinos. Bottom line is it's probably experimental error. -- BenRG (talk) 08:38, 24 September 2011 (UTC)

Law One of the Universe: Einstein is ALWAYS correct. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 27 Elul 5771 18:19, 26 September 2011 (UTC)

Can we make high quality image of exoplanet with current technology?

100x100 image of Earth

Today we can make direct images of exoplanets, but with really poor quality. Its extremely complicated, I understand.

Can we make hight quality image of exoplanet with current technology? Is it possible?

What we need for 100х100 pixel image of the nearest exoplanet? Really big telescope? How big?

sorry for my English --Ewigekrieg (talk) 10:04, 24 September 2011 (UTC)

You can calculate from the diffraction limit - the minimal angle that can be resolved with a telescope of a given diameter is roughly λ/d, where λ is the wavelength of the light and d is the diameter of the telescope. Assuming there is a Jupiter-sized planet at ε Eridani, you want about 1400 km per pixel, you need an angle of 1.4*10^-11. At a wavelength of 500 nm (green light), the diameter of the telescope needs to be about 35.5 km. Maybe you should try to build an interferometer of that size instead. Icek (talk) 13:41, 24 September 2011 (UTC)

There is an active NASA Ames project called "lunar micro rover" which is building a system capable of lunar VLBI out of very inexpensive lunar rovers and orbiter, which could have a baseline (equivalent mirror size) over 2,500 kilometers. This sort of system was proposed by the Japanese in 1994 and has since become well understood using solid state heterodynes, e.g. at the Cambridge Optical Aperture Synthesis Telescope and UC Berkeley Nobel laureate Charles Townes' 10 micron VLBI at Mt. Wilson/Palomar. A lunar VLBI system would be able to detect and characterize Earth's nighttime electric lighting out to 100+ light years, and detect ozone (a likely sign of the kind of life we can eat) on exoplanets much further out.

However, there seems to be vast ignorance and some resistance to lunar VLBI in the professional astronomy community for some different reasons. The military has been withholding formation flight control systems for space VLBI since the 1990s so that synthetic aperture radar battlefield imaging -- which uses the same formation flight control systems -- won't fall into the wrong hands, I suppose. However, the average seismic displacement on the Moon is less than a micron, so closure phase computations in the interesting 9-15 micron band (including ozone in 9-10 microns as well as the first two coldest spectral lines of hydrogen for characterizing the coldest interstellar gas clouds and black hole microlensing) would be easy from digital heterodyne post-processing without any adaptive optics, let alone classified formation flight control systems. Combine that with the fact that such a system will, for less than $1 billion, perform with far more resolution, sensitivity, and important scientific results than any other telescopes yet contemplated, and it's not hard to see why this makes professional astronomers a bit uneasy, is it? 208.54.86.178 (talk) 16:58, 24 September 2011 (UTC)

Only if by "uneasy" you mean eager to get the project started. The system may, not will, perform with important scientific results. Synthetic aperture radar imaging seems well understood and is applied in Reflection seismology, see Reflection seismology#Marine(streamer). Cuddlyable3 (talk) 18:40, 24 September 2011 (UTC)

If you want a chance of working on such a project, study Mandarin, not English.

To clarify, are you talking about placing this array on the Moon ? I'm assuming you mean the far side, to eliminate Earthshine. This would certainly be a worthy scientific project, and we've been looking for some reason to go back to the Moon just to practice for Mars. However, I bet the cost would be a lot more than $1 billion, considering there's the delivery cost, the installation crew, the lunar satellites needed to relay the pictures back to Earth (or maybe a series of towers to transmit the pictures to the near side then down to Earth). And would there be a permanent maintenance staff located there ? StuRat (talk) 03:59, 25 September 2011 (UTC)

Not if the first step is to get a mostly self-sufficient robot economy started on the Moon... Wnt (talk) 15:03, 25 September 2011 (UTC)

It's just ~10 rovers with infrared scopes in craters or next to hills for sunshade, spread out on the lunar far side, and an orbiter (or possibly even the existing Lunar Reconnaissance Orbiter) to collect the digital data to be transmitted to Earth for closure phase combination. You don't need astronauts to set it up at all. You don't even need lunar GPS because each rover will have its own clock signal. The issues are: how do you keep the cryostat fluid from boiling off for as long as possible, and how do you keep dust out of the scopes -- point them down and tap them occasionally? Everything else about the system is relatively low tech, unlike the JWST which looks like it could end up costing over $8 billion and has a zillion single points of failure moving parts (while the lunar rovers are fully redundant with each other) without camera capabilities allowing for more than a pixel per exoplanet. The Google Lunar X Prize people say that they can place lunar landers for about $30 million each -- presumably less if a bunch of them go up on the same rocket. 69.171.160.110 (talk) 16:40, 25 September 2011 (UTC)

Species Identifcation

Species to be identified

To aid a rename request what is this specifcally? Sfan00 IMG (talk) 13:37, 24 September 2011 (UTC)

My guess is Myosotis latifolia ([4]) or Myosotis scorpioides ([5]), based on the broad leaves. --Mr.98 (talk) 14:38, 24 September 2011 (UTC)

Circumstantial evidence suggest the second of those - the photographer lives in Matlock, Derbyshire, which is in Europe and near water. 213.122.0.58 (talk) 17:00, 24 September 2011 (UTC)

existence of time

Is TIME just an idea, or does it really exist? how do you prove its existence? does this question make sense? — Preceding unsigned comment added by 203.112.82.128 (talk) 13:51, 24 September 2011 (UTC)

The question is a good one but is a bit hard to answer here. At its heart, time is just the way we mark sequential events. But it gets much more complicated (and interesting) from there. Start by reading the beginning of the article "time", and from then, if you're feeling adventurous, the article on Philosophy of space and time. --Mr.98 (talk) 14:30, 24 September 2011 (UTC)

Arrow of time also addresses your questions. Red Act (talk) 14:38, 24 September 2011 (UTC)

Time is, at root, simply change. Every time you speak a sentence that uses a verb, you presuppose the existence of change -- so this is really a self-answering question: the act of asking it implicitly answers it. Looie496 (talk) 15:01, 24 September 2011 (UTC)

A road changes from a six-lane metallised highway in the city to a dirt track in the hills. But time is not a necessary prerequisite for that change to occur. SpinningSpark 15:39, 24 September 2011 (UTC)

No, for several reasons:

• If time is exactly the same as change, then this is not an explanation. All you've said is that the word "change" could have been used in the question instead of the word "time".
• If time is not exactly the same as change, the question remains: how are they different?
• What SpinningSpark said.
• The fact that the OP is obliged to ask the question in a language with an embedded concept of time does not mean that the concept is correct or refers to any real thing. The English langauge also has an embedded concept of absolute certainty, for instance, which is at odds with fallibilism.  Card Zero  (talk) 17:11, 24 September 2011 (UTC)

Time... time is a magazine.-- Obsidi♠n Soul 16:50, 24 September 2011 (UTC)

Time as a pointer, singling out the present moment as being real, doesn't exist, see e.g. here. Also, simply from the fact that information is conserved, it follows that the distant past and the future exist on an equal footing as the present moment. Count Iblis (talk) 17:08, 24 September 2011 (UTC)

A little change in time is the difference between now and now. The progress of time is required for change. Plasmic Physics (talk) 23:39, 24 September 2011 (UTC)

The next moment already exists in the present moment, because information is conserved. If we assume the intuitive notion of time and assume that somehow the Unverse ended in 1980, we would still subjectively find ourselves alive in the year 2011 posting here on Wikipedia. This is because the physical state of the universe as it exists now in some reference frame can be defined in terms of the state in 1980 by applying the time evolution operator. Count Iblis (talk) 00:03, 25 September 2011 (UTC)

The OP got it right when he asked "Does this question make sense?" Such fundamental concepts as time are so necessary to thought that they are in effect axiomatic--they cannot be denied without implicitly being used in the very denial. For example, what would it mean to say "Elbert Ainstein has proven that time does not exist" or that the OP is waiting for us to answer his question? Another problem that may be lurking here is materialism, the belief that to exist is to be matter. That is a subtle misconception that lurks in our culture. The notion is, roughly, that everything is made of atoms, and therefore, since things like time or thought are not made of atoms they are not really real, just illusions, or so forth. (The obvious problem here is that it implies that illusions exist, which contradicts the premise that all things are only atoms. If you find it hard to believe that all things are not atoms, ask yourself if shadows are real, and if so, what is their molecular mass.) The correct way to analyze time is to see that while it is not an entity, (like a book or a body, or an atom, or a galaxy) and it is not an attribute, (like soft, or pink, or sticky) it is a relationship. Time in the concrete experiential sense is the relationship of before and after and so forth, just as size is the relationship of bigger or smaller than and direction is comprized of the relations nearness and being between and so forth. Time in the sense of "all of time and space" is simply the grand matrix of all the before and after relationships of all entities and the changes which they undergo. Indeed, time is relative, and without change or the entities which undergo change there would be no time. The Newtonian notion of absolute time is ultimately a confusion.

DEFINE TIME if you wanna get a result from that discussion...--Irrational number (talk) 15:49, 26 September 2011 (UTC)

There is no mystery about time, as such. The spacetime that we inhabit has four (macroscopic) dimensions, one of which is distinguished by having a signature in the metric tensor that has the oppsoite sign to the other dimensions - this dimension is time. The existence of the arrow of time - the fact that we cannot travel in either direction through time as we can in any of the spacelike dimensions - is where the real mystery lies. Gandalf61 (talk) 16:21, 26 September 2011 (UTC)

Thats the problem, i cant even define time.  — Preceding unsigned comment added by 203.112.82.128 (talk) 17:08, 26 September 2011 (UTC) 

It is highly unlikely that it looks this much like time exists if it doesn't. That said, it most likely doesn't exist as an explicit dimension. The nearby universe (see many-worlds interpretation) that you'd call the immediate future is generally in a different direction than the immediate futures of other universes are from them. This is known as Timeless Physics. It's not well-known enough to have a page on Wikipedia, but it's much simpler and more elegant then any other interpretation, and therefore much more likely to be correct, by Occam's razor. It's hard to say how likely it is compared to ideas that we haven't considered, but there's no reason to suggest that they would have time as an explicit dimension. — DanielLC 23:47, 27 September 2011 (UTC)

Taking other universes for granted but implying that the existence of time is an open question is the fallacy of the stolen concept. μηδείς (talk) 23:23, 28 September 2011 (UTC)

Horizontal penis

http://en.wikipedia.org/wiki/Bushmen#Neoteny

"Ashley Montagu noted that Bushmen have the following neotenous traits relative to Caucasoids: "large brain", light skin pigment, less hairy, round-headed, bulging forehead, small cranial sinuses, flat roof of the nose, small face, small mastoid processes, wide eye separation, median eye fold, short stature and horizontal penis"

What exactly is a horizontal penis? ScienceApe (talk) 15:48, 24 September 2011 (UTC)

Maybe it means that the opening to the urethra (or w/e it is called) is horizontal as opposed to vertical? Other than that I can't imagine (unless these dudes have a permanent priapism. :p) Sir William Matthew Flinders Petrie | ^{Say Shalom!} 25 Elul 5771 15:54, 24 September 2011 (UTC)

At a complete guess, it means the penis points horizontally when erect. Erection notes most penises point upwards but some are more or less horizontally straight forward. It gives stats take from "Sparling J (1997). "Penile erections: shape, angle, and length". Journal of Sex & Marital Therapy 23 (3): 195–207" which suggests that study found only about 10% had a penis that was more or less horizontal when erect. In the article on Bushmen it's suggested it's a trait associated with Neoteny which I guess means the the curvature or angling of the erect penis often becomes greater during puberty. Nil Einne (talk) 16:32, 24 September 2011 (UTC)

Googling around suggests that Ashley Montagu is the only source for this. Maybe they were just pleased to see him.--Shantavira|^{feed me} 16:46, 24 September 2011 (UTC)

And why was "large brain" placed in scare quotes, while the rest are not? Werdnezz!-- Obsidi♠n Soul 16:49, 24 September 2011 (UTC)

It isn't in the source [6]. I don't think it's that weird either, anything concerning the brain tends to make some people uncomfortable because of perceived connections to intelligence. Also because of the complexity of the brain, large could be taken in different ways. However IMO the quotes should be removed. Incidentally, the source doesn't seem to have any explaination of the penis thing in the part available thru Google Books (to me) although does note persistence of penile prepuce as a neotenous trait but it seems that isn't related to the horizontal thing. I note the page after the section on neotenous traits which refers to penile prepuce (and that is the last visible entry in the table) isn't available so it's possible I'm not seeing some relevant stuff that is in the source. Edit: It seems the larger brain part was removed by the person who added the AM source as they believed it was not in the source [7], and then re-added upon checking the source along with the quotes [8]. On second thought, perhaps quotes are because of confusion as they didn't understand why a larger brain is a neotenous trait, but of course babies and children have much larger brains compared to their bodies then adults because the brain and head doesn't grow as much. Nil Einne (talk) 16:54, 24 September 2011 (UTC)

Wouldn't a small brain (relative to the size of an adult brain) also be a neotenous trait? Which means that an ordinary-sized brain shows inclination towards two neotenous traits.  Card Zero  (talk) 17:24, 24 September 2011 (UTC)

Nope, It's relative to body size. i.e. Small body, big head. Even tiny embryos have larger heads relative to their bodies than adults.-- Obsidi♠n Soul 21:01, 24 September 2011 (UTC)

Yes, I get it: I was just wondering whether a single part of the body which doesn't grow as much as the rest, such as the left hand of a person with Poland syndrome, would also count as a neotenous trait. Neoteny mentions down syndrome, which is associated with microencephaly, I think*, so in that case small brains - in absolute terms - are neotenous, which seems to mean all sizes of brains are neotenous and undermines the meaning of the term.

* Google thinks  Card Zero  (talk) 21:21, 24 September 2011 (UTC)

It was discussing neoteny. It would have been understood that it was referring to physical size relatively. Placing it in scare quotes only makes it more like it was an attempt to appease the which-race-is-more-intelligent moot-pointers. :/ -- Obsidi♠n Soul 18:18, 24 September 2011 (UTC)

I don't see any reason to think the person who added the original ref and placed the quotes understood or even appreciated this. Note as I said above, I agree the quotes should be removed, however I don't think their placement is that surprising and there are plenty of reasons why they could have been added. Nil Einne (talk) 03:13, 25 September 2011 (UTC)

acu

whats the official army acu glove for cold weather — Preceding unsigned comment added by 64.38.197.221 (talk) 17:33, 24 September 2011 (UTC)

I assume acu is Army Combat Uniform. This is what the British army wear (note the trigger finger). Cuddlyable3 (talk) 19:19, 24 September 2011 (UTC)

Factoid WRT pesticides on unwashed shop-bought fruit...

"You take in more toxic chemicals from drinking one cup of coffee or smoking one cigarette than you do from eating unwashed fruit every day for a year".

True or false? It's a line that I've heard people quoting when it comes to people who are concerned that shop-bought fruit is covered in large amounts of highly-toxic (poss. carcinogenic) pesticide residue - as one of those 'well, smart people know that...' things, though I'm not sure where it comes from... --Kurt Shaped Box (talk) 17:49, 24 September 2011 (UTC)

See http://www.thedailygreen.com/healthy-eating/eat-safe/Dirty-Dozen-Foods#fbIndex1.

—Wavelength (talk) 17:59, 24 September 2011 (UTC)

Mostly true. A study in Science from 1992 [9] looked at the known rodent carcinogens in foods. Such carcinogens can be naturally present, created by cooking / processing, or added as pesticides. They found that the known rodent carcinogens that one consumes from having three cups of coffee a day is roughly 300 times more potent than the total carcinogens the average person consumes via pesticide residues (based on typical American diets and EPA limits on allowable pesticide residues). Relative potency is estimated by looking at the chronic exposure required to cause cancer in 50% of rats. By this measure one can roughly estimate that consuming three cups of coffee per day regularly over a lifetime raises your cancer risk 0.05%. Pesticide exposure risk is similarly ~300 times lower. Now for some caveats. There are many naturally occurring chemicals that have never actually been measured, so the true risk of various foods / cooking is likely to be unknown. Secondly, rats are not necessarily a good model for humans in all, or even most, cases. Third, the risk does not necessarily scale linearly with dose, so figuring out the effect of trace carcinogens from the amount that causes cancer in rats may be misleading in some cases. Lastly, you can't really know whether the food in front of you complies with legal limits for pesticide. Dragons flight (talk) 18:32, 24 September 2011 (UTC)

PS. It's also possible for chemicals in food to be toxic without being carcinogenic. Carcinogens are generally the easiest form of long-term damage to observe though. Dragons flight (talk) 18:41, 24 September 2011 (UTC)

An excellent answer Dragons flight. Thank you. --Mr.98 (talk) 14:22, 25 September 2011 (UTC)

Indeed. Thank you very much for your answer, DF. Just the sort of thing I was looking for. --Kurt Shaped Box (talk) 22:14, 25 September 2011 (UTC)

God

is there any effort, outside religion, that is fully documented to prove God's existence? — Preceding unsigned comment added by 203.112.82.128 (talk) 18:11, 24 September 2011 (UTC)

No, by definition, god is unscientific because it can't be falsified. See falsifiability.

Although this is a science reference desk the OP did not specify that formal Scientific method must be involved in the effort. The question is ambiguous about whether it seeks "a fully documented effort" or "a fully documented proof"; the former seems more likely. Does an off-duty monk making extracurricular prayers for an epiphany count as "outside religion"? Cuddlyable3 (talk) 19:05, 24 September 2011 (UTC)

yeah, im asking if there is a fully documented effort to prove it. — Preceding unsigned comment added by 203.112.82.129 (talk) 19:29, 24 September 2011 (UTC)

First of all, you would need to define "God". If you define "God" as meaning, say, the god described in the Christian Bible, then you're wasting your time. Most Christians don't even think that god exists. If you want a more general definition, then it gets a little tricky. To prove the existence of a god, you need a miracle. That is, something happening that science says is completely impossible We don't have a complete understanding of science, though, so we can't say for certain if something is impossible or not. That means we don't know if it's a miracle or just a mistake in our understanding of science. --Tango (talk) 20:39, 24 September 2011 (UTC)

Does science really say that certain things are impossible, Tango? Scientists might make such pronouncements. My understanding, as a non-scientist, of the scientific method is that phenomena that actually happen are observed and explained. Science per se has an "open mind" as to whether it's possible for something to happen or exist, or not. Scientists sometimes have rather more closed minds, though. Also, a miracle is not something that anyone who knows what they're talking about says is impossible; it's something that has actually been observed to occur, but for which there is currently no scientific explanation. -- Jack of Oz ^{[your turn]} 21:39, 24 September 2011 (UTC)

"Most Christians don't even think that god exists"? That doesn't sound right to me, Tango. --Mr.98 (talk) 21:58, 24 September 2011 (UTC)

It depends on what the meaning of the word "that" is. I'm fairly sure that in the sentence "Most Christians don't even think that god exists.", Tango was using the word "that" as an adjective modifying the word "God", to indicate the god described in the Christian Bible, as opposed to other conceptions of God. But in your objection to that sentence, I think you're probably interpreting the word "that" as a conjunction introducing the subordinate clause "god exists", which I don't think was Tango's intended meaning. Red Act (talk) 05:51, 25 September 2011 (UTC)

Sorry, that was badly worded. Red Act is correct about my intended meaning. I should have said "Most Christians don't even think that that god exists". It was a reference to Biblical literalism being a minority viewpoint. --Tango (talk) 15:26, 25 September 2011 (UTC)

I agree with this, although it makes me wonder then why they are christian at all then. ScienceApe (talk) 17:44, 27 September 2011 (UTC)

This IS the Science reference desk, so we have every right to give a scientifically oriented answer. That answer is "No". HiLo48 (talk) 20:37, 24 September 2011 (UTC)

Just to be clear, im not asking if there is a fully documented proof of god, but if there is a documented effort to prove god. — Preceding unsigned comment added by 203.112.82.1 (talk) 21:07, 24 September 2011 (UTC)

That term you are using, "documented effort", seems a little strange, but important to you. Can you put it into other words? Exactly what do you mean by "documented effort"? HiLo48 (talk) 21:24, 24 September 2011 (UTC)

yeah, i think its a weird term as well, english is not my primary language, what i mean by documented effort is a study that is published recognized by credible people. — Preceding unsigned comment added by 203.112.82.2 (talk) 21:37, 24 September 2011 (UTC)

Most scientists who lived before 1850 believed in God. Many of the historic scientific discoveries could have confirmed the existence of God, assuming that God really exists (as most scientists used to believe). The "God hypothesis" was always the de facto null hypothesis, since before Galileo. But in every case where the Bible could have been proven correct, it was falsified. It is only because the believers have adapted their belief to make it consistent with every new scientific finding over the centuries, that they have ended up with something that is immune to falsification. Count Iblis (talk) 21:54, 24 September 2011 (UTC)

There have been, and are today, lots of efforts to try and prove God exists. For an historical approach, see, e.g., William Paley. For modern folks trying to do the same thing, see, e.g., Michael Behe or William Dembski. Lots o' documentation available; Ronald Numbers' The Creationists: The Evolution of Scientific Creationism (Univ. Calif. Press, 1993), is chock full o' documentation of these sorts of folks. These efforts have not been successful, if you mean, have actually proven God to exist, or have convinced mainstream scientists that their "proofs" are both accurate and mean what they claim to mean. --Mr.98 (talk) 21:58, 24 September 2011 (UTC)

Just above, our OP referred to credible people. Are creationists, starting as they do from the position that God does exist, credible people in this matter? HiLo48 (talk) 22:02, 24 September 2011 (UTC)

Some are certainly more credible than others. Behe and Dembski are as credible as any other scientist types. What matters is not the starting position — everyone comes to every question with their own starting positions, some quite sane, some quite looney — but how compelling their arguments are for their position. (Newton's starting position for his physics was that God existed and was holding it all up in an active way. But that's not what made him right or wrong in his work, in the end.) In the end, as I've noted, most scientists don't buy their arguments and aren't convinced. But my point is that they've certainly made an effort. --Mr.98 (talk) 22:28, 24 September 2011 (UTC)

One can investigate the universe by starting with "I'm going to find out how the universe began" or with "I'm going to prove that God created the universe". The former is a scientific approach. The latter is not. HiLo48 (talk) 22:49, 24 September 2011 (UTC)

It doesn't matter how you start, or why. What matters is what you end up finding. There have been lots of wonderful science done in the name of bad suppositions. Michelson started his interferometer experiments to find the luminiferous aether. What is found is that the aether didn't exist. He won a Nobel Prize for this, despite his own desperate desire, until his death, to prove the aether did exist. What made him a good scientist was that his results were solid. There are plenty of other examples to be found in the history of science. Every philosopher of science I have read (including the much vaunted Popper) has insisted that the sources of inspiration and direction are immaterial to the validity of the actual findings. This is not at all to deny the importance of context — just to say that you can't differentiate between science and non-science on the basis of motivation. --Mr.98 (talk) 02:08, 25 September 2011 (UTC)

I'll paraphrase what I said earlier in a related discussion. It is impossible to scientifically prove the existance of God. He's exsistance can only be reasoned for through personal experience. Here's a quote, "Then said Jesus unto him, Except ye see signs and wonders, ye will not believe."John 4:48 — Preceding unsigned comment added by Plasmic Physics (talk • contribs) 23:32, September 24, 2011 (UTC)

That's another classic Biblical quotations that can be interpreted in many ways. The word "signs" is obviously a simplification of or metaphor for something else. We all see signs every day, but the relevant signs mentioned there are obviously very special ones, and the quotation doesn't explain any further, so we are left to speculate and wonder. Which brings me to.... I see many "wonders", almost every day. Seeing them doesn't convince me of the existence of the Christian god. I tend to look for scientific explanations. The mystery to me is why some people think that something as yet unexplained (to them) proves that a god did it. HiLo48 (talk) 00:00, 25 September 2011 (UTC)

People have needs. One of them is a need for a kind of certainty about their place in the universe. For many people, that need is satisfied by positing a god as the only plausible explanation. If they say the existence of such a god is thereby proven, they're not thinking properly. It's still in the realm of belief, and will always be. But as far as they're concerned, they believe it, and they act as if it requires no further proof. That's what belief means. The same applies to those who say there is no evidence for a god, and therefore his non-existence is proven. Wrong again, but they still act as if there is no god and that is consistent with their belief system. -- Jack of Oz ^{[your turn]} 00:25, 25 September 2011 (UTC)

No, that's absurd. When people say "god doesn't exist" they mean it in the colloquial sense. In the same way as me saying Vishnu doesn't exist, or Thor doesn't exist, or Bigfoot doesn't exist. Do I mean that literally that it has been proven that they don't exist? No of course, not, it's impossible to prove a negative. But no one will knock you for saying Bigfoot doesn't exist, but when it comes to god, people get pedantic and start arguing about how you can't disprove god, thinking that's a good argument when they are actually committing a logical fallacy called argument from ignorance. In dealing with these pedantic idiots, you have to be more literal and say "I don't believe in god, I reject your claims unless you have evidence supporting them." ScienceApe (talk) 17:44, 27 September 2011 (UTC)

A common reason converts give, is that an atheistic view of their own existance is depressing - that it there is no point in living, you come and you go, you exist and then you don't, just another statistic. It is natural for people to seek self-justification/validation. The context of the quotation is: a man heard rumours of the Messianic wonders performed by a man named Jesus, who passed through his town some time before. He was desperate for a cure for his dying son, his last hope was this Jesus, who is rumoured to heal any affliction with word or touch alone. He does not believe, since he has not witnessed, yet he hopes. In hope, he pleads for one such healing wonder for his son. Through words alone from Jesus, his son is cured in an instant, and brought to perfect health. Thus he believes, and he doesn't doubt any further. He required personal experience to verify what he heard. Plasmic Physics (talk) 01:48, 25 September 2011 (UTC)

Your story can't be verified, it's just a story that was almost certainly made up. Even if it were true, how does that prove an entity created the universe? It just proves this man named jesus had super healing powers. ScienceApe (talk) 02:11, 25 September 2011 (UTC)

I'm sorry, but I don't follow your logic, how is it almost certainly made up? I didn't say that it proves that God created the universe. Plasmic Physics (talk) 02:31, 25 September 2011 (UTC)

I think what ScienceApe is getting at is, even if Jesus did heal the kid, all it would justify is a belief that Jesus can heal sick kids. Why would the father's experience justify a belief in God? HiLo48 (talk) 02:38, 25 September 2011 (UTC)

• This conversation has strayed well outside the purpose of this page, which is of course answering questions related to science. Beeblebrox (talk) 02:50, 25 September 2011 (UTC)

The original question has been answered, I'm just answering consequencial queries about the qute I gave. There is no point in giving a quote if no one understands it.

The Messiah was prophesied centuries before, and Jesus is the only one who fits the description. Basically whoever is the Messiah, is also the Son of God according to the prophesy. This man must have known about the prophecy, meaning that if Jesus is indead the Messiah, then He must also be the Son of God, hence God must exist according to the man who witnessed. Plasmic Physics (talk) 02:59, 25 September 2011 (UTC)

That would only work if the man believed the prophesies of the coming of the Messiah, so he was already a believer. HiLo48 (talk) 03:21, 25 September 2011 (UTC)

He was a sceptic, that is why he needed proof. Plasmic Physics (talk) 03:26, 25 September 2011 (UTC)

Proof of what? HiLo48 (talk) 03:31, 25 September 2011 (UTC)

Proof that the prophesies were true. Plasmic Physics (talk) 03:42, 25 September 2011 (UTC)

No, that's circular. For that to work he would have to believe Jesus was the Messiah. HiLo48 (talk) 03:47, 25 September 2011 (UTC)

It is also statistically meaningless: people make prophecies all the time. By simple chance, some will come true - and even more will be claimed to have come true by people reinterpreting later events as 'the prophecy being confirmed'. See Nostradamus and other hogwash for more evidence of the same... AndyTheGrump (talk) 03:53, 25 September 2011 (UTC)

It is not circular, MBR was predicted by the big bang theory. They found it, and other evidence, thus the big bang theory must be right. They were searching for evidence that is predicted by a theory. The prophecy was made several times over by different people over different times, and is too detailed to apply to just anyone. Plasmic Physics (talk) 04:18, 25 September 2011 (UTC)

You have missed the point. I have made mine. And we ARE way off topic. I'll stop now. HiLo48 (talk) 04:25, 25 September 2011 (UTC)

Clearly, there is an anthropic factor at work here:

So, the fact that we are neither machines nor part of a galactic civilization is consistent with anthropic reasoning. Perhaps anthropic reasoning can also explain why we aren't very rational beings. Most people still hold on to religious believes that are incompatible with (modern) science. Perhaps there is an anthropic factor that at work here. Scientific progress has been hindered by religion over the centuries. Perhaps civilizations consisting of more rational beings evolve faster than us and transform to machines in less generations than we will do. The total number of individuals that will ever have lived in our backward civilization may be much larger than in rational civilizations

Count Iblis (talk) 03:49, 25 September 2011 (UTC)

Oh, come on. We are not about to "transform" into machines. It is possible that humans might invent machine intelligences which will kill off or "outbreed" humans ecologically and send them to extinction. But your mind is a relationship between your body and the world. The end of your body is the end of your mind. A copy of your mind (if such a thing is possible) would not be your mind. It would just be a copy of your mind. This sort of "singularity" speculation is even less grounded metaphysically than is the notion of the prime mover. μηδείς (talk) 03:58, 25 September 2011 (UTC)

To try to understand God you must try to understand Good; you must learn and follow the positive movements of people driven by compassion, hope, and faith. If you can understand the historic patterns of these movements and find places and times of great significance, it is possible to encounter one or two of the Lamed Vav Tzadikim, as the Jews call them. Strange things can happen. Wnt (talk) 04:23, 25 September 2011 (UTC)

Here is an interesting answer for you, which would be a yes to your question. Given that Christians consider Jesus the moshiach, the Son of God and God himself, then the fact that archaeologists do actively search for evidence that Jesus Christ did exist (to my knowledge we still don't have concrete contemporary evidence) would mean that there is a serious and scientific effort to prove the existence of God (in one way). Then again, most of the archaeologists doing this are ike myself anyway, so we don't really believe he's God anyway (or the moshiach except for these guys (who are Christians anyway)). ;) You can find it all published in Hershel Shenks's sensational Biblical Archaeology Review. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 26 Elul 5771 06:14, 25 September 2011 (UTC)

What do you mean contemporary evidence? Use Gengis Kahn as an example, what contemporary archealogical evidence is there for his existance? Plasmic Physics (talk) 11:32, 25 September 2011 (UTC)

None that's written by the looks of that article, and I know we haven't found his tomb. Still, no one disputes the existence of Chinghis as far as I know (could be wrong). People do dispute the existence of Jesus and we would need contemporary writings for him. Poor Jesus; can't a Jew get a break? :p Sir William Matthew Flinders Petrie | ^{Say Shalom!} 26 Elul 5771 16:14, 25 September 2011 (UTC)

There's a difference. No one is making supernatural claims about Genghis Khan. No one said he created an empire by killing his enemies using laser beams fired out of his eyes. All of the claims made about him are, well, believable. It's the same thing about Mohammad, I don't dispute his existence, I just don't believe he was a prophet of god. Jesus may have existed, I don't really care either way, I just don't believe the supernatural claims about him. Also I don't believe the prophecies made about him because they may have been fabricated after the fact, and foretell of events that I, nor anyone else, can verify. ScienceApe (talk) 18:11, 25 September 2011 (UTC)

M'yes, and I don't believe the supernatural stuff about Jesus either, but that is not the issue. For many Christians, proving his existence would be proof of God. What I am talking about with regard to Jesus is not whether he was divine or has special power. I was saying that we do not even know if this specific Nazarene Jew even existed as a human being or just a made up character to be the central figure in a new sect of Judaism. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 26 Elul 5771 18:20, 25 September 2011 (UTC)

I know what you were saying. Personally it doesn't matter one way or the other to me. I can accept the claim that he existed but was a normal man. But once they start talking about prophecy and such, I will tell them I can't confirm their story, so their prophecies are meaningless to me. The prophecies, story about his life, and even his own existence could all be fabricated. That's the difference between jesus and Genghis. Mongolians aren't saying "Well we have prophecies that a man will come from poverty and grow up to become a great general who created an empire! This man is god!". Christians on the other hand are claiming this, so I need more evidence. The prophecy has to be true, and the event it predicted must also be true, but in the case of jesus, I can't confirm either. And even then, it still doesn't prove he is god. It would, at most, prove the prediction to be accurate, but the claim that jesus is god can't be confirmed from that prediction. ScienceApe (talk) 22:59, 25 September 2011 (UTC)

Frank Tipler is an example of a (once?) reputable scientist giving a scientific approach to God. Say what you will about his work (I'm unconvinced, to put it mildly), but it is absolutely "a fully documented effort to prove" God's existence using science. I'm sure he's not the only one, but maybe the most successful and visible contemporary one. Staecker (talk) 12:08, 25 September 2011 (UTC)

Perhaps I do not understand what you mean by a fully documented effort but I assume you mean an effort that is done for others in the first place. I know of one effort that was done mainly for the author's satisfaction of disproving a counter claim the author chose to share with others. --DeeperQA (talk) 03:11, 26 September 2011 (UTC)

air pumps

Hypothetically, if I have a narrow tube or pipe down which I want to force air, at a pressure of 0.5psi, say, but that it is in a rather awkward to get to place, then I think through all the options and somehow come to the conclusion that the best way to proceed is to build my own battery powered pump to move the air through, then, how small could such a thing actually be built? What component parts would it need to be made from, I assume there is some limit to the sizes at which they would be able still to work up to that pressure, anyone give some sort of rough estimate here?

148.197.81.179 (talk) 19:29, 24 September 2011 (UTC)

With enough effort it is possible to build a battery-powered pump so small you almost need a microscope to see it. Is that information useful to you? No? I thought not. How about a clearer description of the actual problem? Looie496 (talk) 19:46, 24 September 2011 (UTC)

So how would this microscopic thing actually work, though, would it need some particularly expensive materials to stop such a small thing breaking under the pressure perhaps? What about getting enough power to the mechanism itself? Would the tools to build it be hard to get hold of?

Or if you insist, how about this then, how small would be possible just using things that someone or some people could easily go out and buy and put together? Could people with enough knowledge, somewhere to work and not a huge amount of money build one that could fit through a hole perhaps say 10mm wide? What about 5? 148.197.81.179 (talk) 19:56, 24 September 2011 (UTC)

As Looie says, it would be much easier to help us if you tell us what you are actually trying to do. --Tango (talk) 20:50, 24 September 2011 (UTC)

It would be very much easier and cheaper to buy a standard air pump, site it some distance away, and just insert the outlet pipe through the narrow gap, but I assume your particular application precludes this simple alternative. Dbfirs 06:41, 25 September 2011 (UTC)