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August 26

Leaf Color

I want to know why most plant leaves are green. I know that is it because of the pigments in the leave reflecting green light, but what I want to know is why that holds true for most all plants. Why is the green wave lenght of light something that needs to be reflected by the plant? Why not blue? Is there something about the middle of the visible spectrum that makes it disadvantagous to absorb? Does it have have to do with the amount of energy in that part of the spectrum?--98.240.70.102 (talk) 00:08, 26 August 2009 (UTC)[reply]

Chlorophyll is one of the main chemicals involved in absorbing light energy to begin the process of photosynthesis. If you use the search box at the top of this ref-desk page to look for "chlorophyll", you can find several previous discussions about its color. DMacks (talk) 00:24, 26 August 2009 (UTC)[reply]

(e/c) Its not so much that green light needs to be reflected, the reason most plants look green is a consequence of what wavelengths of lights need to be absorbed (and, as you said, the non-absorbed part of the light spectrum is what gives plants their colour).

Different wavelengths of light require different accessory pigments to be effective for photosynthesis. In green plants are green because for chlorophylls and carotenoids mainly absorb violet-blue and red light. Its difficult to know why green plants evolved their particular system to take advantages of the blue/red light, but it is clear these spectra are extremely effective in producing energy in the ecological niche green plants find themselves in. That is not always the case, though, in red algae, for example, the spectrum is different due to phycobilins, which absorb blue-green light. This allows algae to grow in deeper waters that filter out the longer wavelengths used by green plants. Again, their colour is a by product of the most effective absorption spectra for their niche. Rockpocket 00:33, 26 August 2009 (UTC)[reply]

For what it is worth, some researchers (PMID 17407409) have proposed that there is logic in why green plants do not absorb green light. The propose that the absorbance peaks are determined by three factors:

(1) the wavelength of peak incident photon flux; (2) the longest available wavelength for core antenna or reaction center pigments; and (3) the shortest wavelengths within an atmospheric window for accessory pigments.

Personally, I don't fully understand these three factors, but I thought I would throw them out there... Rockpocket 00:48, 26 August 2009 (UTC)[reply]

Really, red or blue plants would be even better. The Sun makes more green and yellow light than any other colors. Possibly no other photosynthetic chemicals were suitable? Is it albedo? Wavelength diffraction/scattering thing with some size scale of the cell? It's suprising. If this happened (red plants), and sentients evolved to have red blood, green wouldn't be especially calming and our instinctive color for danger and calming might be conflicted. Thank goodness the Borg didn't design plants or they'd be black from UV to IR and have gears. Sagittarian Milky Way (talk) 06:42, 26 August 2009 (UTC)[reply]

I'm pretty sure this has been discussed before and so should be somewhere in the archives Nil Einne (talk) 08:50, 27 August 2009 (UTC)[reply]

I thought this little black snake was harmless, can someone help ID it?

What type of Black Snake is this, I can't make a positive id

I was handingling this little black snake on a beach in southern BC and I thought it was a garter snake and I considered it harmless, but now that I am zooming in on the photo off camera it doesn't look so much like a garter snake anymore and I since I can't really identify it I was wondering if anyone recognized it or could make an id on it, as I would like to know if I almost got myself bit by a poisonous snake? GabrielVelasquez (talk) 03:32, 26 August 2009 (UTC)[reply]

There are relatively few species of non-rattlesnake, non-coral snake (both of which are easily and instantly recognizable) in North America. So barring it being a Cottonmouth or a Copperhead (which it isn't), it isn't poisonous. (Hooray.) It looks like a racer to me, or even a garter. (Note that I guessed that BC meant either British Columbia or Baja California, so if either of those are wrong, you'd better make it more clear which BC you meant!) --68.50.54.144 (talk) 04:14, 26 August 2009 (UTC)[reply]

Sorry, British Columbia the Province in Canada, I have never been to Mexico.

It turns out that garter snakes do actually produce some poison, but not enough to be dangerous to people. See garter snake#Venom. --Anonymous, 04:22 UTC, August 26, 2009.

To a first approximation (as in: Don't Bet Your Life on it) all Snake venom which are harmful to humans have two prominent fangs, and snakes with just teeth and no fangs aren't lethal. But usually if you're close enough to see the fangs, you're too close for comfort. -- 128.104.112.102 (talk) 16:58, 26 August 2009 (UTC)[reply]

Despite what this article says, I believe quick way to check if a snake is venomous -- check the underside of the tail (posterior to the anal slit). Non-venomous snakes underbellies feature single scales that extend from left to right up until the anus but two adjacent scales posterior to the anal slit. Venomous snakes continue the single scale feature.[1] DRosenbach ^{(Talk | Contribs)} 22:06, 26 August 2009 (UTC)[reply]

Um, but then you're picking up a potentially venomous snake. (Also, the article's mentioning of stripes as a criteria really ought to say, "unless it is a coral snake") --68.50.54.144 (talk) 04:46, 27 August 2009 (UTC)[reply]

Are coral snakes the only venomous snakes which can't be identified about the scale thing? I have no idea. [2] does give the thing DRosenbach mentioned, although it notes it's useful for when the snake is dead (although do note even a dead snake must be handled with care), as do a number of other sources. But I noticed one thing; all of them are American including DRosenbach's one. Other sources such as our article which Rosenbach mentioned and [3] all say there is no single method when you are referring to diverse geographical locations. While the original question is referring to North America, DRosenbach's claim lacked any qualification (other then I believe) and you should be very careful when making a point blank statement of that sort. Does your method work throughout Asia? What about Australia? Africa? I don't know but it's entirely possible the answer is no. BTW, even if the method does always work in identifying venomous snakes, it may not be any use if all the snakes in the area have that feature including non-venomous ones as in that case you're going to be thinking all snakes are venomous (which is not a bad thing in any case, but clearly defeats the purpose). P.S. I found [4] which may be of interest Nil Einne (talk) 05:57, 27 August 2009 (UTC)[reply]

Yeaup, the good Doctor starts off saying all snakes have venom glands (page 11) and then starts a characteristic chart for non-poisonous snakes and poisonous snakes (page 14), and I'm left going "Oh shyt!" it has "broad ventral scales!" - but the tree continues and the the remaining level tells me it is not a Viper or Cobra. Interesting but incomplete. GabrielVelasquez (talk) 06:27, 28 August 2009 (UTC)[reply]

Would it be possible to run a power plant with dissimilar metals?

You see nuclear plants, but they take so long to build. You always hear that solar panel electricity costs too much money (but they're very useful for portable or low power and remote things) What could be something we could do right now and will be finished quicker, so it will tide us over and help a few percent and not cost as much money?

If you lay an enormous area of continous copper plates on a desert and paint them black maybe cover it with glass plates (finally the greenhouse effect will help us), place a similar zinc plate next to it, join them with power lines, and connect the other two ends to the power grid would any electricity flow? Or would that work only with expensive doped semiconductors? Would a conductive bath replacing the short wire help? Or use more traditional methods of temperature gradient exploitation with pipes and turbines and stuff except imstead of having to continously make the gradient with fuels we just do something as simple as change the thermal properties? Desert caves could be the cool end. The temperature just a little inside a cave is constantly similar to the average annual temperature, which is not hot. I've never heard of "caval energy" before. Edit: Or nearby high altitude mountains. Or find an already naturally dark desert and do.. something.

They can print solar panels now. On plastic film like an inkjet printer. So what about pouring them? Some sort of viscous liquid that would be dropped from planes or helicopters over a large square area of desert, left to dry set freeze cool down or whatever until it builds up a layer, and then do it all over again with the other pourable substances: the insulator, maybe a protectant and base layer, and of course the opposite semiconductor (p and n), then after that's done, we just build power lines connect it to the grid, and use it forever? If exploitation of artificially-created albedo (and thernal mass etc.) asymmetry is done on a truely massive scale, maybe we should be careful not to negatively impact local or even global climate, but even the entire global heating and precipitation from heat-island effect from partly changing the color of 0.01 of all land plus all the energy use is positively miniscule, and local precipitational changes are small, so it might be benign? Either that or find some ways to make solar panels less like microchips and more like roadwork. I'm all out of ideas now. Sagittarian Milky Way (talk) 06:05, 26 August 2009 (UTC)[reply]

Wikipedia is not a suitable forum for discussing original proposals for machines and such, so we can't go into detail here, but other forums on the internet are great for this kind of discussion. As for the question in your title, you have to consider that these metals are not found in their pure form in nature. It takes energy to extract them and purify them. So even if electricity did flow, you would probably spend more energy building this contraption than you would get out of it. And you'd be left with a lot of waste when the battery ran down. When it comes to using thermal gradients, you may enjoy reading up on our articles on geothermal energy and Heat pumps. EverGreg (talk) 08:48, 26 August 2009 (UTC)[reply]

FWiW, as far as I can remember, your proposal for covering the desert with copper and zinc plates is similar to one of Nikita Khruschev's pet projects, to surround all the steelmaking furnaces and whatnot with layers of semiconductor thermocouples to use the waste heat for electricity production. Well, it turned out that the amount of energy produced in this way would be negligible, more energy would be spent manufacturing and installing the thermocouples than they would produce, and in any case it was more economical to surround the furnaces with water jackets and tap the steam from the jacket to run a power turbine. So, sorry to shoot down your proposal, but it just won't work. 98.234.126.251 (talk) 09:55, 26 August 2009 (UTC)[reply]

Hmm, it would appear dissimilar metals are not needed for the thermoelectric effect. Hey, if it won't work, it won't work. There's always the black pipe and turbine method.. Sagittarian Milky Way (talk) 11:46, 26 August 2009 (UTC)[reply]

There is great potential to harvest solar energy in the desert, with photovoltaic panels, or with solar reflector arrays focussed on a boiler to make steam. For a building, solar heat can be collected with a home built or commercially made collector with glass over a black-painted sheet of metal. This can heat air, or it can heat liquid flowing through metal tubes connected to the metal plate inside the well insulated collector panel. I don't see any merit in the idea of having dissimilar panels in the desert. They would been to be connected by electrolyte to act as a simple primary battery. Just as in the early 19th century, the zinc plate basically is burned up in the process, and zinc costs far more than fossil fuel, even allowing for the high efficiency of battery versus engine. Electricity could have been economically important by the 1840's if anyone had realized that a motor could be used as a generator, and powered by falling water of a steam engine instead of batteries. There will likely be great advances in lowering the cost of making semiconductor photovoltaic panels. I particularly like the idea of "solar shingles" so the entire south-facing (in the northern hemisphere) roof half would be a solar collector, perhaps with the roof (where feasible) built at an angle equal to the latitude to maximize efficiency. The solar energy striking a collector is about a kilowatt per square meter at peak intensity. Such solar shingles should be lower cost and more durable than solar collectors now for sale. Another fruitful area for research is better storage batteries. In 1908, electric cars were commonly available which had a 100 mile all-electric range. A century later, car companies promise us that in just a few years we will be able to buy electric cars with--ready for this A 100 MILE RANGE! Of course today's cars go 70 miles per hour, and the 1908 cars went only about 15 miles per hour, but that just means that your days driving is over in about 2 hours. Edison (talk) 16:28, 26 August 2009 (UTC)[reply]

All those damn cul-de-sacs! Causing millions of solarly disadvantaged roofses to have random azimuths which would otherwise have the common N-S!

Doesn't the photoelectric effect only work with blue photons and higher? Why are solar panels usually deep blue then? Is this why they're so inefficient? I'm suprised they can even print (and eventually paint) solar panels cause usually when you think of semiconductors you think 99.9999... pure silicon doped with 1 atom in 10000 of gallium or something like that. This raw stuff looks like inky goop. Sagittarian Milky Way (talk) 17:06, 26 August 2009 (UTC)[reply]

Doesn't having an irradiance comparison between Earth and New Extrasolar Planets make sense?

New planets that are being found are being referred to as being in or out of their parent star's "Habitable zone,"
Which basically refers to the distance range that water would be liquid.
But the concept is being used to insinuate more than water being present, it is used to suggest these systems could have life.
That is easy to accept if you ignore all the other factors involved in the process, and believe Water=Life.
As there are many factors other than irradiances that would keep H₂O from being liquid,(Mass/cohesion, Abundance of elements/Metalicity, Excessive X-rays/M-type star, Amount of CO₂) it is a little deceptive and irresponsible to make the suggestion to people that a planet may have life because it is X distance from its star. The idea of a habitable planet is flawed as it is, but I would like to know if anyone can find fault with the Solar Constant comparison between Earth and other planets?
Simply as a comparison of heat, a more direct comparison, no insuations, as heat does not itself equal life.
(note: Irradiance, Insolation, and Solar Constant are synonymous.)

Basic Insolation Figures Chart

Planet Distance	Insolation (W/m²)	% of Earth's.
55 Cnc f Apastron Flux	380.136	27.74%
Mars' Aphelion Flux	494.00	36.06%
55 Cnc f Average Flux	547.395	39.99%
Mars' Average Flux	590.589	43.11%
Mars' Perihelion Flux	718.545	52.45%
55 Cnc f Periastron Flux	855.305	62.4%
HD 108874 b Apastron Flux	1234.655	90.12%
Earth's Aphelion Flux	1,321.544	96.74%
Earth's Average Flux	1,366.079	100.00%
HD 108874 b Average Flux	1413.557	103.18%
Earth's Perihelion Flux	1,412.903	103.43%
HD 108874 b Periastron Flux	1634.359	119.30%
Venus' Aphelion Flux	2,585.411	188.72%
Venus' Average Flux	2,620.693	191.30%
Venus' Perihelion Flux	2,656.70	193.93%
Gliese 581 c Apastron Flux	3,619.829	264.97%
Gliese 581 c Average Flux	4,870.841	356.56%
Gliese 581 c Periastron Flux	6,903.119	505.32%

GabrielVelasquez (talk) 07:52, 26 August 2009 (UTC)[reply]

I agree with the OP that Habitable zone is little more than a hopeful categorisation. It means a range where water existing in liquid form is not strongly ruled out but not that it does occur or even necessarily would be liquid. As our article says, the zone may be further restricted by galactic location. I don't understand the OP's line of questioning. I find no fault with the Insolation comparison chart for 3 local planets though one might need to look into the sources to find whether precision of 7 significant figures is justifiable. However to the lead question, having an irradiance comparison between Earth and Extrasolar Planets makes no sense as long as we lack data to create one, and no numerical criteria are in evidence for using it to set further limits to planetary habitability.Cuddlyable3 (talk) 08:32, 26 August 2009 (UTC)[reply]

Remember also that the local solar constant is not the only possible source of heat with which to keep water liquid (a basic but not necessarily valid assumption underlying some definitions of a "zone of life") Contributory factors, difficult or impossible to quantify from interstellar distances, include nuclear fission energy released from transuranics in the candidate body's core, and tidal heat generation caused by any orbital eccentricity around its parent primary, whether a star or a larger planet. In our own Solar system, several satellites of the gas/ice giants are well outside the Solar Constant-based "habitable zone", but nevertheless may have subsurface liquid water, even oceans, due to such factors.

Some of Gabriel's not entirely clear question (which seems a little contradictory since the basic "possibility of liquid water" calculations are just initial extrapolations from the calculated insolations he espouses) implies he is aware of such factors, but merely because they cannot be certainly measured does not make it valid to ignore them entirely and revert to a single-dimension comparison between Earth and extra-solar planets; this latter is in itself inadequate because other factors like the candidate's size (not to mention composition) are crucial - consider that the rather diminutive terrestrial planet Mars is by most criteria just outside the crude "zone of life", but if Mars were Earth-sized it would probably be just within it.

I disagree with Gabriel's proposition that "it is a little deceptive and irresponsible to make the suggestion to people that a planet may have life because it is X distance from its star . . . ." Saying that, according to the criterion in question, something may be possible is not a claim that it necessarily or even probably exists. Moreover, while the possibility is is intellectually interesting and may have philosophical or even religious implications for some people, it is of little importance in most people's day-to-day lives. 87.81.230.195 (talk) 12:49, 26 August 2009 (UTC)[reply]

If you want liquid water, you are also going to need an atmosphere probably at least equivalent to earth at 25,000 ft or lower, or all your water might boil away. Googlemeister (talk) 13:27, 26 August 2009 (UTC)[reply]

And as it boils it would be building a (water) atmosphere, so no problem there. Dauto (talk) 15:31, 26 August 2009 (UTC)[reply]

That is going to depend on the gravity of the planet as a small planet might not be able to prevent that vapor from escaping. Also if its sun had a high level of solar wind, that might continuously erode the atmosphere as fast as it is built. I would imagine that a planet we have discovered would be fairly large, so gravity might not be too big an issue, but solar wind we probably can not determine from here. Googlemeister (talk) 19:27, 26 August 2009 (UTC)[reply]

Even harder to determine would be the absence/presence and strength of any planetary magnetosphere, and the consequent protection from the solar wind it might afford. Mars seems to have suffered from the multiple effects of an over-wimpy gravitational field, a lack of magnetic field-generating molten-mantle convection currents, a lack of plate tectonic movement and subduction to recycle back into its atmosphere gases and water chemically bonded to its rocks, and (more speculatively) a lack of life to beef up its water cycle and facititate said tectonics (according to the extended Gaia theory).87.81.230.195 (talk) 14:33, 27 August 2009 (UTC)[reply]

to Cuddlyable3 (talk)'s point:
In a lot of cases the Radius and Effective temperature of a parent star is known, or can be calculated using the formulas at the Luminosity article. The formula that calculates luminosity from Radius and Temperature and the formaula that calculates luminosity from distance and insolation are obviously Equal for the Sun and Earth data. and basic algebra yields:

$L=4\pi R^{2}\sigma T^{4}\,$ ...and
$L=4\pi d^{2}\ f\,$ ...therefore,
$4\pi R^{2}\sigma T^{4}\ =4\pi d^{2}\ f\,$ ... and
$R^{2}\sigma T^{4}\ =d^{2}\ f\,$
$\ f\ =(R^{2}\sigma T^{4}\,)/d^{2}$

...All I'm saying is it is not unknown.

code for Earth at Perihelion: $f_{p}={\frac {((6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (5778^{4})}{((1-(1\times 0.016710219))\times 149597876600)^{2}}}=1,412.903\ W/m^{2}$

code for Gliese 581 c at Periastron: $f_{p}={\frac {((0.38\times 6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (3480^{4})}{((0.073-(0.073\times 0.16))\times 149597876600)^{2}}}=6.9\times 10^{3}\ W/m^{2}$

Having said that I am not saying this should go directly into an article.
But I do remember reading a debate where it was pointed out that using known data with known formulas is not synthesis.
In a lot of cases scientists are going as far as to speculate on on effective temperature and surface temperatures, using this albedo or that emissivity,
but on the other hand if the algebra is correct then the insolation is closer to fact. Definitely less misleading than saying there may be life on Gliese 581 c:
(see Than, Ker (2007-04-24). "Major Discovery: New Planet Could Harbor Water and Life". www.space.com [5] )

${\frac {Gl\ 581\ c\ Periastron\ Insolation}{Earth's\ Solar\ Constant}}=$ ${\frac {6.9\times 10^{3}\ W/m^{2}}{1,366.079\ W/m^{2}}}=505\%$

GabrielVelasquez (talk) 07:40, 27 August 2009 (UTC)[reply]

I apologise for sounding so negative with my words "makes no sense". I do not mean that such a comparison using present estimates cannot be calculated. I do mean that it is not convicing that this gives such an improved criteria for habitability of planets that the water-as-liquid estimation must be discarded. If the OP's challenge is Find fault with this insolation calculation or confess that your ideas of habitable planets are flawed, deceptive and irresponsible, then I don't see that ever being resolved short of an interaction with lifeforms on Gliese 581 c. Cuddlyable3 (talk) 08:44, 27 August 2009 (UTC)[reply]

The OP sent the following spreadsheet to my home page. Cuddlyable3 (talk) 16:46, 31 August 2009 (UTC)[reply]

Since you seemed to be interested in the topic, I thought you might not have seen this:

Makeshift optical telescope

I've got a handful of different kinds of lenses and I'm trying to figure out a way to combine them into some sort of telescope. I don't need anything permanent, I'm not actually going to use it for anything, I'd just like to see how far I can see while keeping it in focus.

The different sorts of lenses I have:

- From my Nikon DSLR: 18-55mm 1:3.5-5.6G 55-200mm 1:4-5.6G (both are obviously complex lenses, I don't really know what that means towards putting them together with other lenses)

- Single simple lens (was junk), says 70-210mm 1:4-5.6 on it, but I think it might just be the top taken off of a larger photographic lens. either way, the single lens is convex on the outside and concave on the inside. According to the wiki page on lenses I think it's "negative miniscus" i.e. the concave lens is more extreme than the convex. Held close to my face it will slightly magnify my hand at a distance under 3 cm or so, and then it will only focus again if it's more than 20cm or so from my face.

- A pair of typical 7x35 binoculars (says 525 ft. at 1000yds.)

- A small fish-eye lens meant for a camcorder.

I know it's kind of a random assemblage of lenses, but I really don't know very much at all about optics, and even less about the math, so can anyone see any possible configuration that might give me a little more zoom than just the binoculars (at the moment, the most powerful of the lenses)? Thanks in advance! 210.254.117.186 (talk) 08:07, 26 August 2009 (UTC)[reply]

Good luck experimenting. I think you use the word "zoom" (variable focal length) when you really want just a fixed telephoto result. Wikipedia has articles on optics that can help. For cameras: Teleconverter and Tele extender. For Optical telescopes: Refracting telescope and Amateur telescope making. A problem you will encounter with telescopes is stable mounting. I think your Nikon 55-200mm lens with a teleconverter has possibilities. Cuddlyable3 (talk) 09:04, 26 August 2009 (UTC)[reply]

I concur with Cuddlyable3. Any telephoto camera lens is essentially a miniature telescope sans eyepiece, and can be used as the main or Objective lens (the big one at the front) of a telescope arrangement, but you will need to add an eyepiece or Ocular lens (the little one at the back you look through) whose qualities are more critical; obtaining actual telescope oculars should be both easy and relatively cheap given the number of small commercial telescopes around.

Your 3 main problems are to 1. mount the telephoto lens firmly, preferably on the biggest, heaviest moveable-head tripod you can find; 2. make a means of firmly attaching, and easily detaching, your ocular(s), exactly aligned with the optical axis of the main lens; and 3. incorporate a means of moving the ocular(s) back and forward to focus the arrangement - some sort of push-pull arrangement using nested tubes will be probably be much easier than more elaborate screw or rack & pinion mechanisms (though you could cannibalise a cheap microscope for the latter). Your resulting device will probably have a small field of view, making it quite difficult to find a target in the night sky, so you may need to add a pointing aid, which can be merely a slender open-ended tube fixed parallel to the lens body, through which you sight.

I myself once made a serviceable small telescope using an old theodolite tripod, a 600mm "mirror telephoto" camera lens (essentially identical to a small Catadioptric telescope) and an assortment of old eyepieces borrowed from my local Astronomy Club, plus various bits of camera mount conversions, plastic and/or cardboard tubes, etc. Good luck and have fun.87.81.230.195 (talk) 12:07, 26 August 2009 (UTC)[reply]

Thanks for the tips. Would the eyepiece from a crappy "toy" telescope work? I can get one of those easily, and hey the cheaper the better. And is there any system for testing out the "oculars" I have that I might be able to find something that actually magnifies quicker than just placing them all randomly? The main problem I can see just arranging them myself is that the field of view I get is almost always incredibly small, even as small as a dot in the near distance. 210.254.117.186 (talk) 12:54, 26 August 2009 (UTC)[reply]

A toy telescope eyepiece should certainly work (as might a toy microscope eyepiece), but the quality of image you will get in terms of general clarity (arising from the glass/plastic quality), resolution (fineness of detail), degree of aberration (distortions of the image) and width of field of view will doubtless be less than with higher quality telescope or microscope eyepieces (the latter are very similar in general design and quality to telescope eyepieces, and amateur astronomers sometimes use them).

As to magnification, bear in mind that this is not purely a function of the eyepiece alone, it arises from the combination of the eyepiece with the main lens: specifically M = F/f where M is the magnification, F is the focal length of the main lens, and f that of the eyepiece. For example, a telescope eyepiece of 10mm focal length (not untypical) combined with my telephoto lens of 600mm focal length would give a magnification of 60 times, but with your zoom lens racked out to 210mm the same eyepiece would give a magnification of only 21 times.

The apparent field of view you get depends more on the detailed design of the eyepiece - there are many different ones and new improvements are invented from time to time. In your actual situation, you can only see what different eyepieces you can actually get hold of and try them out to see what works best with whatever objective lens(es) you choose to use.

Depending on how far you want to get into this, you might benefit from getting hold of a relevant basic reference book, either new, second-hand or via a public library. A couple of venerable tomes from my own shelves are James Muirden's Beginner's Guide to Astronomical Telescope Making, Pelham Books 1975, ISBN 0 7207 0822 2, and J. B. Sidgewick's Amateur Astronomer's Handbook 4th Ed, Pelham Books 1979, ISBN 0 7207 1164 9, but there are many others with similar information. 87.81.230.195 (talk) 21:58, 26 August 2009 (UTC)[reply]

My understanding of a telescope is you need an object lens of long focal length to create an enlarged virtual image, then a lens of much smaller focal length to look through and magnify that image. Do not aim it at the sun, because it will start a fire or instantly blind you. If you have 2 lenses, check their focal lengths by forming an image from a distant light (do not set something on fire with a sun image). Then place the lens of longer focal length at the end of a stick or in a tube with duct tape (or precision machined holders). Aim it at the object you wish to observe and note where on the stick it forms a real image by holding a piece of paper parallel to the lens and moving it back and forth. Place your shorter focal length lens on the other side of that real image and remove the piece of paper on which the image from the object lens appeared. Adjust the spacing according to the lens formula or empirically. Look through your telescope and enjoy the world made closer. A fine adjustment method for the eyepiece lens is highly desirable. Cardboard or PVC tubes to exclude extraneous light, painted black inside to decrease reflections, are helpful. A larger object lens collects more light. Edison (talk) 03:05, 28 August 2009 (UTC)[reply]

Did Indians discovery Laws of Motion centuries before Kepler?

As a retired computer scientist, I've dabbled at reading some anthropological topics, including history of science, historical linguistics, and prehistoric discovery via Y-chromosome typing.

By coincidence(?) three of these topics had subtopics pointing to India. I'll ask a question about one, and make comments about the other two. The reason for combining three unrelated topics into one will become apparent.

1. History of laws of celestial motion.

The Laws of Motion of Kepler and Newton are a major triumph of Western civilization, and often treated as the single greatest discovery that ushered in Modern Science. Yet we see in Wikipedia and other websites that Indian astronomers, notably Aryabhatta and Bhaskara, had developed similar methods.

Is this true? I don't see a similar claim made in a 16-year old print encyclopedia. I'd hate to think that the claims of jingoists (associated with any country), abetted by tools like Wikipedia, could distort records of the history of science!

Assuming the claims about ancient Hindu astronomy are true, can anyone point to me on-line documents based on pre-Keplerian writings? In relevant Wikipedia pages I see no sources cited (except other source-free webpages). The matter affects me personally, as my own page recites these (unsourced?) claims.

  http://james.fabpedigree.com/mathmen.htm

2. Homeland of the Indo-European speakers

This age-old riddle was solved several years ago (at least by any "preponderance of evidence" standard), but some academic Indian writers continue to insist that the language originated in South Asia. Of these "Indocentric theorists", Harvard's eminent Professor of Sanskrit, Michael Witzel, writes:

"The revisionist and autochthonous project, then, should not be regarded as scholarly in the usual post-enlightenment sense of the word, but as an apologetic, ultimately religious undertaking ... [and such writings] should be regarded and used, not as scholarly contributions, but as objects for the study of the traditional mind."

3. Homeland of the R1a Y-chromosome Haplogroup

The most ancient Ydna Haplogroups of India (C5, H and L) are hardly found outside South Asia; this confirms that there has been no major post-paleolithic migration from India. The strong presence of R1a among Slavs and Hindu Brahmins confirms an "Aryan migration" from Central to South Asia (although the details are a mystery). Yet even this is denied by South Asian jingoists; nonsensical "theories" and faulty studies have polluted the relevant Wikipedia pages. Indian genetic studies suffer severe flaws which can be explained only as deliberate obfuscation of caste-haplogroup correlations. I have a page which discusses this:

  http://james.fabpedigree.com/hindu.htm

Summary. There is no need to debate the conclusions I offer in 2. and 3. As time permits, I will make corrections to the relevant Wikipedia pages. But I wonder if "Indian science" is like the caricature Americans used to have of "Soviet science."

Are the claims about the celestial motion knowledge of Aryabhatta and Bhaskara valid? Or do they suffer from jingoist misinterpretations similar to those of Indian genetic and linguistic "science"? —Preceding unsigned comment added by Jamesdowallen (talk • contribs) 08:40, 26 August 2009 (UTC)[reply]

I would not call the website you have linked a reliable source as it does not appear to have the hallmarks of reliability (editorial control independent of the author; peer review), so making the claims you are making based SOLELY on the text of that website in an actual Wikipedia article would be a bad idea. If you have reliable sources which show independent confirmation of these claims, you may have something, but that website does not appear to be it. --Jayron32 12:51, 26 August 2009 (UTC)[reply]

Just a note... It is actually his own website, not just some website that he found. So, he is using his own writings to justify his point. -- kainaw ™ 12:57, 26 August 2009 (UTC)[reply]

No, he made it clear that it's his own website: "The matter affects me personally, as my own page recites these (unsourced?) claims. http://james.fabpedigree.com/mathmen.htm" --99.237.234.104 (talk) 13:25, 26 August 2009 (UTC)[reply]

If you wish to comment on specific Wikipedia articles, it would be a big help if you mentioned the names of those articles. As far as I can see, our articles on Aryabhata and Bhāskara II do not claim that either of them discovered Kepler's laws of planetary motion. Both of these Indian astronomers may have postulated heliocentric systems, but that is a different matter. Gandalf61 (talk) 13:10, 26 August 2009 (UTC)[reply]

Hi, James again. First, my "complaint" wasn't "against" Wikipedia specifically -- I'm asking for knowledge, not Wiki editing. One claim is that Aryabhatta wrote orbits were ellipses. By itself this is only half of one of Kepler's Laws and of interest only if we can understand *how* Aryabhatta came to the conclusion. Brahmagupta is said to have discovered the law of universal gravitation; again it would be nice to read something close to contemporary. (Both these claims, by the way, are clearly made on the Wikipedia pages cited in preceding paragraph.) The claim that Bhaskara had equations of celestial motion as good as 18th-century Europe may not appear directly in Wikipedia, but is made elsewhere on 'Net. Again, my concern is NOT accuracy of Wikipedia itself, but rather: Are the claims true? Are there on-line translations of early (i.e. pre-Kepler) Indian writing to help one judge the claims? (My own pages are, of course, irrelevant to the question. I wouldn't have mentioned them if I'd anticiapted it wou lead to the confused tangential comments above.) Jamesdowallen (talk) 07:49, 27 August 2009 (UTC)[reply]

I agree that it's worthwhile to doublecheck these claims. Brahmagupta is quoted by al-Biruni as saying: All heavy things are attracted towards the center of the earth. [...] The earth on all its sides is the same; all people on earth stand upright, and all heavy things fall down to the earth by a law of nature. This is great, but it's not the law of universal gravitation which would have involved a mention of an inverse square. Neither do he seem to explain e.g. how the moon fail to fall down on earth. As for Aryabhatta it has been claimed that he proposed heliocentrism. Our article on him links to a rebuttal of this claim. The source of the misconception seems to be that his calculations involved an epicycle with a period of one year, which is how long it takes the earth to go around the sun once. The length of a year is ofcourse known to anyone keeping a calendar, even if they have no knowledge of celestial mechanics. Our article further states that no evidence has been found of him contemplating elliptical motions. In all this, it must be remembered that ancient civilizations were not completely isolated from each other. For instance, the Paulisa Siddhanta examplifies a transmission of greek astronomical theory to india. As for all the topics you've raised, I encourage you to edit any wikipedia articles that present false claims or which portray fringe opinions as mainstream facts. There's certainly room to mention differing opinions, but we should portray the opinion of the scientific community honestly. For that, we need people with knowledge of these topics. :-) EverGreg (talk) 12:56, 28 August 2009 (UTC)[reply]

Hoping for closure on this topic, I contacted a Professor of the history of math and science, who has written well-documented books on such topics; I learned that the claims about Hindu astronomy are exaggerated: Brahmagupta and Bhaskara seem to be very outstanding mathematicians but they used the Ptolemaic model and did NOT develop the celestial laws of Kepler and Newton. (Aryabhatta's contributions may be grossly exaggerated.)

A report from a single Professor may not be dispositive, but I will correct my own webpages. Some Wikipedia pages may parrot the exaggerations. I do not have the time, energy, or knowledge to correct them; is this message sufficient to bring the matter to the attention of appropriate Wiki editors, or is there a more appropriate forum?

Among Wikipedia pages which may need editing are: Bhaskara II:

"The study of astronomy in Bhaskara's works is based on a model of the solar system which is heliocentric and whose movements are determined by gravitation. Heliocentrism had been propounded in 499 by Aryabhata, who argued that the planets follow elliptical orbits around the Sun"

The page for Aryabhata already seems more correct: Aryabhata:

"It has even been claimed that he considered the planet's paths to be elliptical, but no primary evidence for this has been found"

Jamesdowallen (talk) 11:15, 29 August 2009 (UTC)[reply]

Thanks for researching this topic. I've edited the Bhaskara II article and I'll follow up any discussion that might arise from it. EverGreg (talk) 10:43, 31 August 2009 (UTC)[reply]

Cracking joints

Does any animal besides some H. sapiens do this habitually? -GTBacchus^(talk) 09:32, 26 August 2009 (UTC)[reply]

Most hedgehogs that I've had will stretch to the point of popping a few joints when they wake up. Since hedgehogs are at the very early part of mammal evolution and humans are at the very late part, I believe it is safe to assume that other animals in between do the same thing. -- kainaw ™ 12:59, 26 August 2009 (UTC)[reply]

Hedgehogs are at the very early part of mammal evolution ? I would think that honor would go to the monotremes, like the platypus. StuRat (talk) 14:56, 26 August 2009 (UTC)[reply]

Hedgehogs have a smooth brain - which is a characteristic of early mammal evolution. I don't believe many mammals still have smooth brains. I don't what the wrinkles in the average brain are called, so it is difficult to look it up and see where in mammal evolution that trait falls. -- kainaw ™ 16:08, 26 August 2009 (UTC)[reply]

Sulcus (anatomy)? Or Sulcus (neuroanatomy). Bus stop (talk) 16:17, 26 August 2009 (UTC)[reply]

Actually lots of mammals have smooth brains. Convolutions are more a function of body size than anything else -- so rats, mice, shrews, bats, and other very small mammals all have smooth brains. Looie496 (talk) 17:13, 26 August 2009 (UTC)[reply]

Thanks. I've only studied hedgehogs and mistakenly thought that their smooth brain was not so common a feature. -- kainaw ™ 17:44, 26 August 2009 (UTC)[reply]

I think Kainaw is referring to a view (which AFAIK used to be the established one for most of 20th century, but not anymore) that order Insectivora - now defunct - contained the "basal" placental mammals, least changed for the last 100 My. As of now, AFAIK, the hedgehogs and gymnures are placed in Erinaceomorpha (Gregory, 1910), an order of their own. There are modern genetic studies attempting to figure out the proper cladistics and taxonomy of placental mammals. Still, I'd wait another 10-20 years for a new established view to emerge. But strictly speaking no, hedgehogs are not representative of the earliest part of evolution of mammals (or even placental mammals). --Dr Dima (talk) 16:36, 26 August 2009 (UTC)[reply]

The echidna, a monotreme, is sometimes called a hedgehog because it looks a lot like one -- however its evolutionary descent is quite different from that of true hedgehogs, which belong to Laurasiatheria. Looie496 (talk) 17:08, 26 August 2009 (UTC)[reply]

Hedgehogs are at exactly the same time of mammal evolution as humans. Specifically, the mammals around in the year 2009. — DanielLC 03:43, 27 August 2009 (UTC)[reply]

DanielLC, I think what kainaw means is that hedgehog species evolved a long time ago (maybe 15 million years) and have not evolved much since. Humans evolved between 250,000 and 400,000 years ago. Axl ¤ [Talk] 09:19, 27 August 2009 (UTC)[reply]

Well, we're getting into deep issues here. At a molecular-genetic level, hedgehogs have probably changed just about as much as humans over the same time scale. At the level of visible bodily form, hedgehogs look a lot more like their ancestors than humans do, but which is the correct level to look at, the molecular or the macroscopic? Most modern biologists seem to go with DanielLC in thinking the molecular level is more important; I personally am not quite convinced. Looie496 (talk) 16:09, 27 August 2009 (UTC)[reply]

Scientists do look at the molecular-genetic level. What changes have happened to hedgehogs in that time, I don't know, but such studies are done. --Tango (talk) 18:00, 27 August 2009 (UTC)[reply]

Darwin's tree of life implies otherwise. 98.14.223.69 (talk) 12:14, 29 August 2009 (UTC)[reply]

So, you guys are talking about the basal versus derived distinction, right? Are hedgehogs more basal than humans, or do we not know that? According to our article on Laurasiatheria, "Within the Laurasiatheria, the Erinaceomorpha appears (surprisingly) to be the most divergent branch." Does that address the issue at hand? -GTBacchus^(talk) 15:20, 30 August 2009 (UTC)[reply]

movement of knee

Hi if someone were to be standing up and then lift one of their knees off the ground towards their chest is this flexion of the hip? Is this also flexion of of the knee? Thanks RichYPE (talk) 12:42, 26 August 2009 (UTC)[reply]

Yes, both (as long as you're not trying to keep your leg straight). Fribbler (talk) 12:44, 26 August 2009 (UTC)[reply]

Thanks a lot! RichYPE (talk) 19:48, 26 August 2009 (UTC)[reply]

Consider this image of reference desker user:Fribbler on the way to a WP meeting to discuss this very question. Image:Ministry of Silly Walks.jpg --Cookatoo.ergo.ZooM (talk) 06:55, 27 August 2009 (UTC)[reply]

Just for the record... The image of John Cleese shows him with a flexed hip with an adducted and partially extended knee? Is that right? Thanks RichYPE (talk) 19:09, 29 August 2009 (UTC)[reply]

Doubling your gas mileage

I saw this cool video on YouTube on how to double your gas mileage. http://www.youtube.com/watch?v=UHAUsGlfbx8&feature=channel

I just wanted to do a reality check with some people here. Are these tips effective and safe? ScienceApe (talk) 15:06, 26 August 2009 (UTC)[reply]

Most of the stuff is common sense (proper inflation, correct spark, no excess junk, don't run the A/C), and he claims a modest improvement on them (which means he had a badly maintained car with lots of crap in the trunk before). But the biggest improvement he reports is due to adding acetone. Snopes says these claims are "false" and Mythbusters says they're "busted". Moreover, the Car Talk says it's "worse than useless", in that it also destroys o-rings in your fuel system. Heck, whenever someone tries to justify their claim with a conspiracy theory like "what the car companies don't want you to hear" that should set major alarm bells ringing. -- Finlay McWalter • Talk 15:16, 26 August 2009 (UTC)[reply]

Agree. Also see Acetone#Domestic_and_other_niche_uses and the linked sources. --Stephan Schulz (talk) 15:18, 26 August 2009 (UTC)[reply]

The thing about switching to synthetic oil is questionable. There's plenty of online postings that claim you get up to a 4% improvement (and plenty that claim less, or none at all), I've not found a single reliable source that supports any of these claims. Worse, the Wikipedia article synthetic oil#Advantages says it helps gas mileage, but doesn't cite any source at all. There are other reasons you might choose to run synthetic oil, but there doesn't seem to be real evidence that it'll help gas mileage (never mind that it'd be cost-effective). -- Finlay McWalter • Talk 15:36, 26 August 2009 (UTC)[reply]

You may wish to read Hypermiling, which runs the gamut from sensible maintenance to "strategies" of suicidal stupidity. -- Finlay McWalter • Talk 15:40, 26 August 2009 (UTC)[reply]

Far from trying to cover it up, car companies would be delighted if this were true. They make far more profit on their low mileage SUVs than they do on their fuel efficient models. An invention like this would increase demand for SUVs and so contribute to their profits. Wikiant (talk) 16:20, 26 August 2009 (UTC)[reply]

Yep - you can be sure that there aren't secrets that the car company doesn't want you to know. Good gas consumption is a HUGE selling point! Why on earth would they hide a simple, effective trick from you? In fact, with most cars, you'll find many of these tips right there in the owner's manual. My MINI Cooper'S manual says that correct tire inflation, minimal A/C usage, keeping the windows closed over 30mph, keeping your car regularly serviced (ie good oil, good spark, tight belts, etc) trying to keep the engine RPM within the 2000 to 3000 range and not using the "Sport" button will all improve your gas mileage...and that's true. All of those things work. Many of the other suggestions (acetone?! Eeek!) are either dangerous, counter-productive (because the car's computer will be confused) or damaging to the engine. The hyper-milers are a weird bunch...some of the things they claim, simply don't work. Other things (like putting the car into neutral and coasting whenever possible - or disconnecting the power steering pump) are downright dangerous. SteveBaker (talk) 17:11, 26 August 2009 (UTC)[reply]

Agreed, Steve. It's only really the maintenance-free, everlasting car that the car companies are suppressing the patents on. It's Big Oil that's keeping down the really cool fuel efficiency stuff - the water-powered car or the 10,000MPG engine, for example (much in the same way that the battery companies don't want us to know about the universal battery charger that can reliably recharge all types of disposable alkaline cells)... :) --Kurt Shaped Box (talk) 04:10, 27 August 2009 (UTC)[reply]

But bare in mind that the car companies, and specifically GM, do engage in conspiracies against the public interest. My first example is in the middle of the last century, when GM systematically bought up cheap and efficient public transportation systems in cities across the US and then destroyed them, to increase reliance on vehicles they produced. My second example is in the 1990's, where they worked to undermine California's mandate to create electric vehicles (see the movie Who Killed the Electric Car?). StuRat (talk) 12:48, 27 August 2009 (UTC)[reply]

What sources do you have for this? 98.234.126.251 (talk) 05:58, 28 August 2009 (UTC)[reply]

Take a look at Great American streetcar scandal. -Elmer Clark (talk) 08:15, 28 August 2009 (UTC)[reply]

You actually believe this conspiracist rubbish? For the record, it wasn't GM or the National City Lines or any other conspiracy that killed the trolleys, it was their own inherent shortcomings (namely, the lack of flexibility, and the high capital and maintenance costs required to run streetcar lines), along with changing demographic trends in the post-WW2 era (suburban sprawl, interstate freeways, cheap mass-produced automobiles, etc.) What I'm saying is that all those trolley lines would've gone broke anyway -- all that GM could be accused of doing (if anything) is to accelerate the process that was already happening across the nation. 98.234.126.251 (talk) 23:36, 29 August 2009 (UTC)[reply]

Yes, I certainly believe that both of those conspiracies were real. The most obvious point is that, in both cases, GM destroyed items which would have had resale value. In the case of streetcars, they could have been sold to other cities which used streetcars, but GM destroyed them instead, then ripped up the rails so the cities couldn't buy more streetcars and continue service. In the case of electric cars, they still had plenty of life and a line of buyers waiting to purchase them, but GM crushed them instead. Why ? Wasting money like that only makes sense during a conspiracy to destroy those systems. In many ways electric streetcars are more flexible than internal combustion engine vehicles. Since the electricity can be generated from any source and quite far away, streetcars can essentially be powered by coal, hydro-electric power, nuclear, solar, wind, etc. Try doing that with a diesel bus. They also don't pollute the air in the city (they may pollute the air where the electricity is generated, but only if fossil fuels are used there). And population densities remain high enough today in downtown areas to support streetcars, especially during working hours. As for high capital costs, those had already been paid when the streetcars were originally purchased and the rail lines laid. GM then destroyed that capital, making it necessary to pay for it all over again if any city wanted to restore their trolley system. Also, suburban sprawl was largely created by acts of Congress, including the creation of the Interstate Highway System and the GI Bill, which paid for people to build new houses in the suburbs but not for them to buy and fix up existing homes in cities. GM may have had a hand in getting those bills passed, with those provisions, too. (BTW, I used to work for GM.) StuRat (talk) 12:12, 30 August 2009 (UTC)[reply]

"In the case of electric cars, they still had plenty of life and a line of buyers waiting to purchase them, but GM crushed them instead." -- Your claim about "a line of buyers waiting to purchase them" is counterfactual, since sales records actually indicate that demand for electric cars was low.

"In the case of streetcars, they could have been sold to other cities which used streetcars, but GM destroyed them instead, then ripped up the rails so the cities couldn't buy more streetcars and continue service." -- Although I don't have any definitive evidence, I strongly suspect that the same lack of demand was at work in the case of the streetcars -- many cities were converting from streetcars to buses at the same time, so the demand just wasn't there. As for ripping up the tracks, this is routinely done when railroad lines (including trolley lines) are abandoned, partly for safety reasons, partly so that the rails and cross-ties could be reclaimed (for melting and re-manufacture in the case of rails, for firewood in the case of cross-ties). OR: there used to be a branch line of the Union Pacific Railroad near my home, and they ripped it up completely when they abandoned it (I've actually watched them lifting the rails and then picking up the cross-ties with a bulldozer, and loading them onto trucks). Would you say that this is evidence of a "conspiracy" by the UP to get rid of this particular branch line?

"In many ways electric streetcars are more flexible than internal combustion engine vehicles." -- Also wrong -- the fact that streetcars run on rails makes it impossible to create new streetcar routes without major capital investment (this was arguably THE most important factor that caused their demise).

"They also don't pollute the air in the city" -- Correct, but this has absolutely no effect on the economics of streetcar operations, which is what this debate is all about.

"And population densities remain high enough today in downtown areas to support streetcars, especially during working hours." -- Then why is it that none of the streetcar companies in the world (to the best of my knowledge) actually turns a profit?

"As for high capital costs, those had already been paid when the streetcars were originally purchased and the rail lines laid." -- This ignores the fact that even after the rails were laid and the wires strung, they required regular preventive maintenance, at considerable expense. That, too, was a factor against the continued operation of streetcars and for their replacement with buses.

"Also, suburban sprawl was largely created by acts of Congress, including the creation of the Interstate Highway System and the GI Bill, which paid for people to build new houses in the suburbs but not for them to buy and fix up existing homes in cities." -- StuRat, please tell me true: Given a choice, would you rather live in a nice single-story house in the suburbs with a lawn and a picket fence, or in a high-rise apartment somewhere in the inner city?

"GM may have had a hand in getting those bills passed, with those provisions, too." -- This is pure speculation on your part -- do you have any documents backing this up??? 98.234.126.251 (talk) 07:12, 31 August 2009 (UTC)[reply]

"...sales records actually indicate that demand for electric cars was low". That may be an argument not to build more, but it's no argument to crush the cars already produced. They could certainly have been sold for more money than the scrap value of the metal. View the movie I listed and you will see several people who were willing to buy them (most of whom had leased them previously), but were prevented from doing so by GM. If you had a working electric car, would you crush it or sell it ?

You note that many streetcar systems were destroyed at the same time, but this isn't a coincidence, that's due to the action of GM and others. Had it happened naturally, it would have taken a very long time, like the conversion from steam locomotives to diesels.

Saying that I'm wrong when I said that in many ways streetcars were more flexible completely ignores my argument that they are more flexible both for fuel sources and pollution. And the expense of adding new lines doesn't apply to existing lines. That might be an argument for not adding new streetcar lines for new areas, but it's no argument at all for destroying the existing lines. In fact, it's an argument against it. If a city spent all that money to set up such a system, it certainly isn't in their interest to destroy such a large capital investment. And if you argue that no city can have multiple systems of public transportation, I'd point out that many already have; combining subways, buses, etc.

I claimed that GM's actions were "a conspiracy against the public interest", which includes air quality as well as economics. Also, the two aren't entirely separate, as efforts to improve city air quality (like factory emissions standards), do have an economic impact.

I don't believe a streetcar system costs any more to maintain than buses, since the streetcars are much simpler than buses and don't have the maintenance-intensive internal combustion engines and all the other systems that go along with that. Although there may be an effect now that streetcars are so rare that you must pay premium prices for parts and labor. This wouldn't have been the case, had GM not acted, however.

It so happens I do live in the city of Detroit, (not a suburb thereof). As inner cities now are in the US (due to those two bills), very few would choose to live there. They decayed directly as a result of the people and thus revenue moving out of the cities. If we hadn't had those two bills, and our inner cities remained more like those in Europe, then many would prefer to live there.

Check out Who Killed the Electric Car? and watch the creepy "Hiroshima" commercial GM had for the electric car. Unlike most commercials, this one was designed to keep customers away, so they could argue that nobody wanted electric cars and they shouldn't be required to sell them.

As for not having evidence about GM's role in passing those bills, they wouldn't make such deals in public, would they ? And "absence of evidence isn't evidence of absence". StuRat (talk) 17:38, 31 August 2009 (UTC)[reply]

Well, as a rule I don't believe in debating a point once a thread has been archived, but these arguments are so stupid that I just have to respond.

"You note that many streetcar systems were destroyed at the same time, but this isn't a coincidence, that's due to the action of GM and others." -- No, that's due to suburban sprawl, which happened post-war in many US cities at the same time and which was the main factor why streetcars stopped being viable (the existing routes weren't bringing enough revenue anymore, and there was no money to build new ones, etc.)

"Had it happened naturally, it would have taken a very long time, like the conversion from steam locomotives to diesels." -- You should know that the conversion from steam trains to diesels took only a decade or so, and not "a very long time" as you claim. Also, keep in mind that the streetcar lines were in a period of decline since the Great Depression, long before the GM-sponsored conversion to buses.

"Saying that I'm wrong when I said that in many ways streetcars were more flexible completely ignores my argument that they are more flexible both for fuel sources and pollution." -- This ain't what "flexible" means as far as urban transit is concerned -- in this case, the word "flexible" applies ONLY to routing flexibility (and in this respect, buses beat streetcars hands-down).

"And the expense of adding new lines doesn't apply to existing lines. That might be an argument for not adding new streetcar lines for new areas, but it's no argument at all for destroying the existing lines. In fact, it's an argument against it." -- Once again, you choose to ignore the maintenance cost of the tracks and the overhead wires, which is considerable even for existing lines. Also, the changes in urban planning (namely, the above-mentioned suburban sprawl) often meant that existing streetcar lines were no longer viable, so they had to be abandoned because it cost more to maintain them than what they earned in revenue.

"And if you argue that no city can have multiple systems of public transportation, I'd point out that many already have; combining subways, buses, etc." -- True, but in the case of buses and streetcars, they would essentially be competing for the same transit niche, while buses and subways fill different niches. That is a different situation altogether -- in the latter case, the buses act as feeders for the subway and therefore both systems benefit from a symbiotic relationship, while in the former case, there is direct head-to-head competition which ultimately leads to one or the other system displacing the other.

"I don't believe a streetcar system costs any more to maintain than buses, since the streetcars are much simpler than buses" -- They may be simpler, but they need rails to run on and overhead wires to provide current, both of which are expensive to maintain.

"If we hadn't had those two bills, and our inner cities remained more like those in Europe, then many would prefer to live there." -- Oh, really? Historical precedent shows that on the whole, most Americans prefer wide-open spaces, as evidenced by all the westward migrations from 1776 to the present. This has to do with the historical development of the American character, with independence and the "pioneering spirit" and all that stuff. To say that most Americans would prefer to be crowded into high-density inner cities is presumptious to say the least.

"As for not having evidence about GM's role in passing those bills, they wouldn't make such deals in public, would they ? And "absence of evidence isn't evidence of absence"." -- That's the TYPICAL fallacy of a conspiracy nut like that which you just admitted to being -- first making unsubstantiated claims, and then claiming that the lack of evidence is proof of a cover-up. For the record, "absence of evidence is not evidence of absence" is the EXACT SAME argument used by conspiracy freaks who claim that the astronauts didn't land on the moon... or that Amelia was captured by the Japanese while on a secret mission... or even that the CIA blew up the World Trade Center! Geez, what ever happened to "innocent until proven guilty"?! 98.234.126.251 (talk) 07:51, 2 September 2009 (UTC)[reply]

When you say "you can be sure that there aren't secrets that the car company doesn't want you to know.", you're specifically talking about gas mileage, right? I can't imagine a vast multinational corporation that doesn't have at least some secrets. APL (talk) 14:02, 27 August 2009 (UTC)[reply]

Yeah - of course - we were talking in the context of fuel economy. They might well hide crappy fuel economy from you - but good fuel economy is something they want to talk about very much! SteveBaker (talk) 00:10, 28 August 2009 (UTC)[reply]

I'm not so sure that oil companies would necessarily want to hide fuel-saving technology. The big threat to oil companies isn't low gas prices. It is gas prices so high that it becomes worth while to develop alternate fuel sources. For the record, gas prices (as a % of median income) have been falling (on average) since the 1960s. For a gallon of gas to cost the same, in percentage of median income, as it did in 1960, the price would have to be around $4.75 per gallon. Wikiant (talk) 01:16, 28 August 2009 (UTC)[reply]

True, but us driving longer distances in bigger vehicles with more horsepower these days means that high gasoline prices are more of a problem, than they were back then. StuRat (talk) 15:25, 28 August 2009 (UTC)[reply]

But those big-a** square vehicles that were 19.5 feet long and weighed 5,500 lbs. (as much as SUVs) still had to cruise just as fast as cars of today. There couldn't possibly be enough percentage of SUVs + pickups on the road today to make the average fuel economy worse than it was then. Remember that today's more powerful engine could only guzzle fuel faster when accelerating.

If those things were true, why then did it seem like an era of gas cheapness never to be exceeded before or since? Remember, even if you drove half as much in 1960, gas would've felt like (2009$)2.37⁹ Sagittarian Milky Way (talk) 18:42, 28 August 2009 (UTC)[reply]

What 1960 cars weighed 5,500 lbs. ? Perhaps you're thinking of the early 1970's, by which time the cars had gotten much bigger (for example, compare the 1960 Ford Thunderbird, at under 4000 lbs., with the 1972 Ford Thunderbird, which could top out around 5000 lbs.). And gas-guzzling engines guzzle gas at constant speed, too. For one thing, they need to move the mass of those huge engines around. StuRat (talk) 12:01, 29 August 2009 (UTC)[reply]

I was thinking of a 50s(?) Lincoln I saw in a recent car magazine, which might have been as low as 5,000 lbs but I'm pretty sure it said 5,500 lbs. Fuel mileage was, near 10. And old engines were huge! How could they be lighter than today's? Sagittarian Milky Way (talk) 23:25, 29 August 2009 (UTC)[reply]

I think our view of the past is biased somewhat, because the biggest and most extreme vehicles from then are the most memorable and those that get the most press attention. There were also many economy cars in the 1950's (like the 1963 Dodge Dart), but they aren't all that collectible, so you don't hear as much about them today. The main concern at the time was keeping the purchase price down, but this also resulted in the unintended consequence of saving gas, as a smaller, lower horsepower car will also tend to sip gas. StuRat (talk) 11:47, 30 August 2009 (UTC)[reply]

Addition Reaction of Alkynes to Alkenes

Hello. Which geometric isomer is favoured when halogens react with alkynes to form alkenes? For example, does 1-butyne react with Br₂ to yield 1,2-dibromo-trans-1-butene? Does the hydrogenation of haloalkynes differ? For example, does 1-bromopropyne react with H₂ to form 1-bromo-trans-1-propene hypothetically? Thanks in advance. --Mayfare (talk) 15:46, 26 August 2009 (UTC)[reply]

I found two sources which contain generic answers:

[6] and [7]

There's a slightly higher level analysis here [8]

For hydrogenation it depends (I think on the process and catalyst) - however when the alkyne is absorbed on a solid catalyst it is usually to expect cis addition of H2, but there are plenty of ways this can not be the case.

83.100.250.79 (talk) 23:15, 26 August 2009 (UTC)[reply]

In my experience, hydrogen-transfer hydrogenation of haloalkynes does not have noticeably different cis/trans due to the halide. DMacks (talk) 00:30, 27 August 2009 (UTC)[reply]

Exotic Matter

My understanding is if we could replicate exotic matter which negated the attraction of mass (gravity) then we could practically move a bus into earth orbit using a model rocket engine since it would be essentially massless.

So then why don't we have scientists at NASA working around the clock determining how to make this stuff? Even if we don't know exactly where to start if we know the characteristics of the final product we should be able to invent a variety of testable methods. Is this being pursued at all? TheFutureAwaits (talk) 16:23, 26 August 2009 (UTC)[reply]

It's probably being pursued by someone somewhere on a creatively written grant. However, there is no reason to believe it actually exists. There are a great many forms of magic that would be amazing if they were only non-fictional; thankfully, NASA isn't working around the clock on any of them. 24.159.32.213 (talk) 16:37, 26 August 2009 (UTC)[reply]

I always thought that the lack of a consumer Star Trek Transporter shows that capitalism doesn't work. Similarly the lack of an immortality pill on the market... --Stephan Schulz (talk) 16:45, 26 August 2009 (UTC)[reply]

We have the technology to make a wired transporter anyways. But if you want to do it, set some time aside since the computers would take years to finish the scan before transmitting, and you better not change anything during the scan. Googlemeister (talk) 17:56, 26 August 2009 (UTC)[reply]

And for chrissakes don't forget the Heisenberg compensators. (I was privately betting myself $5 that this wouldn't be a redlink - and I won!) How do they work? "Very well indeed". SteveBaker (talk) 20:37, 26 August 2009 (UTC)[reply]

No, the lack of a transporter likely shows that capitalism does work. Given the number of breakthroughs required, at the moment, the present discounted value of the expected future profits are less than the present discounted value of the expected costs. Capitalism is working by not diverting scarce resources to something whose cost exceeds its payoff. Wikiant (talk) 20:40, 26 August 2009 (UTC)[reply]

Um, I'm pretty sure Stephan was joking... Nil Einne (talk) 08:34, 27 August 2009 (UTC)[reply]

The lack of any serious consideration of transporters is simply that the underlying physics prohibits it. Until/unless there is some very fundamental change in our understanding of the universe, you can't even consider making such things. Ditto with what our OP is asking. Until some very basic physics says that the most basic part of the mechanism could even theoretically work - there is absolutely no point in spending money on how to build one! The kinds of physics that might one day make either of these things conceivable is being done...but not with the intent of producing teleporters or intertia-less drives. SteveBaker (talk) 22:11, 26 August 2009 (UTC)[reply]

I don't see anything in the laws of physics that prevents transporting a human being. It's simply a matter of quickly scanning a person down to the individual atoms, sending that information to a remote site, then quickly reassembling those atoms in that specific order at the new location from a stockpile of the various elements there. This is certainly currently well beyond our capabilities in every step, but nothing we can't one day hope to achieve. StuRat (talk) 12:37, 27 August 2009 (UTC)[reply]

The Heisenberg uncertainty principle puts a limit on how accurately you can perform that scan. Whether that level of accuracy would be sufficient or not, I don't know. --Tango (talk) 16:10, 27 August 2009 (UTC)[reply]

That limits us to not being able to know the exact position of an electron (if, indeed it has an exact position), but shouldn't make it impossible to determine the identity of a specific atom. I believe we can already do that, for a few atoms at a time, especially if we don't care if we destroy the organism attached to those atoms, in the scanning process. We just need a way to do it for all the atoms in the body, very quickly. StuRat (talk) 19:27, 27 August 2009 (UTC)[reply]

Identifying an atom is relatively easy, but you can't know its exact position and momentum at the same time. I'm not sure how precisely that information would be required, but that is the main issue with transporters. --Tango (talk) 19:34, 27 August 2009 (UTC)[reply]

All you'd have to know is which molecule the atom is within, and that doesn't require all that much precision, does it ? StuRat (talk) 15:04, 28 August 2009 (UTC)[reply]

It is far more complicated than that. Organic chemistry involves very complex molecules, simply knowing how many of each atom are in a given molecule doesn't tell you anywhere near enough. --Tango (talk) 21:19, 28 August 2009 (UTC)[reply]

Yes, you'd have to know where in the molecule the atom is, too. StuRat (talk) 03:27, 29 August 2009 (UTC)[reply]

And you would have to know where the molecules is. The combination of those facts is the position of the atom, which is precisely what we cannot know precisely. --Tango (talk) 15:31, 30 August 2009 (UTC)[reply]

You certainly can know approximately where the atom is, which should be good enough to find it's location in the molecule. To put it another way, all you need to do is identify the molecules and their locations and orientations. StuRat (talk) 15:41, 31 August 2009 (UTC)[reply]

See AEGIS for a possible test to see if antimatter is such an exotic matter. In any case, it would be cheaper to move the entire population of the Earth to Mars with conventional methods than it would be to create enough exotic matter to move anything visible to the naked eye into space. Also, antimatter has an annoying tendency to annihilate itself when it touches matter, so it would be particularly impractical. By the way, this wouldn't make it massless for the purposes of faster-than-light travel. You don't seem to have made that mistake, but I feel I should point it out anyway. — DanielLC 03:39, 27 August 2009 (UTC)[reply]

Nobody actually expects AEGIS to show any significant difference between matter and antimatter, do they? It's just a test to double check something that everyone is pretty certain is true - such tests are very important in science, of course. There is no way to know what the cost of producing exotic matter will be until we know how to do it (if it is even possible). It might turn out to be really easy once we know how. --Tango (talk) 16:09, 27 August 2009 (UTC)[reply]

For it's worth CP violation produced some interesting results showing that antimatter is definately different to matter in some ways. Whether this applies to yuor statement I'm not sure. Elocute (talk) 20:09, 27 August 2009 (UTC)[reply]

Fusion

I checked out this section on nuclear fusion, http://en.wikipedia.org/wiki/Nuclear_fusion#Important_reactions but it didn't list fusion between two plain old hydrogen atoms to produce helium. Why is this? ScienceApe (talk) 16:49, 26 August 2009 (UTC)[reply]

Plain old hydrogen contains no neutrons, and helium without neutrons is unstable. You need at least one; ordinary helium has two. Looie496 (talk) 16:57, 26 August 2009 (UTC)[reply]

See diproton for more info. Looie496 (talk) 16:59, 26 August 2009 (UTC)[reply]

What about plain old hydrogen fused with deuterium to produce Helium3? ScienceApe (talk) 18:55, 26 August 2009 (UTC)[reply]

As the page you linked to says, if there is only one product it is difficult (if not impossible) to conserve both energy and momentum. The momentum of the sole product would need to equal the total momentum of the two reactants as would the energy, but energy and momentum are closely related so it probably won't be possible to get them both right. --Tango (talk) 19:17, 26 August 2009 (UTC)[reply]

I'm not sure I understand. Are you saying that the conservation of energy won't allow for that fusion event to take place? ScienceApe (talk) 04:32, 27 August 2009 (UTC)[reply]

It would make it very unlikely to take place. It could only take place if the initial momentum and energy was such that it could all be given to a single particle. I'm not sure if that is ever possible (I would need pen and paper to work that out, and I don't have any), it certainly isn't likely. --Tango (talk) 16:12, 27 August 2009 (UTC)[reply]

Tango is right that a reaction with just one product would be unlikely because of energy conservation. But nothing keeps it from sheding the extra energy as a photon (a second product) as you can see for instance in the article Proton–proton chain reaction. Dauto (talk) 02:06, 28 August 2009 (UTC)[reply]

Note that in order to "stick together", one of the protons must turn into a neutron through positron emission. I don't remember where I read it (and unfortunately got no way to find the source), but I've read somewhere that only a small fraction of protons do that upon colliding with another proton -- the vast majority just bounce off again. FWiW 98.234.126.251 (talk) 06:15, 28 August 2009 (UTC)[reply]

That's not the case for the specific reaction we are talking about which is H+D->He3+gamma. Dauto (talk) 15:34, 28 August 2009 (UTC)[reply]

I just read the article and explained the reason given therein, if it is wrong don't blame me! What you say makes sense, but there must be something else preventing that reaction taking place, otherwise it would be far more common than it is. --Tango (talk) 21:22, 28 August 2009 (UTC)[reply]

The article seems to be concerned with only pure nuclear reactions (Strong interaction) and the emition of a photon requires a mixed reaction that also includes the electromagnetic interaction since the photon does not interact through the strong interaction. I was just pointing out that the Hydrogen-Deuteron reaction is possible and non-negligible in many situations. Dauto (talk) 20:26, 29 August 2009 (UTC)[reply]

True, the article does explicitly say it is ignoring EM interactions. Do you know why the article doesn't like EM reactions? --Tango (talk) 15:33, 30 August 2009 (UTC)[reply]

drifting

Approximately how long does it take for something to drift from South America to Cape Hope? Just need a ballpark, 2 months about right? Googlemeister (talk) 17:37, 26 August 2009 (UTC)[reply]

1-3 mph is ballpark. Did you drop the engagement ring? Sagittarian Milky Way (talk) 19:31, 26 August 2009 (UTC)[reply]

Message in a bottle. Googlemeister (talk) 19:34, 26 August 2009 (UTC)[reply]

Yeah, I know. I threw one once. It washed back in seconds. Sagittarian Milky Way (talk) 19:54, 26 August 2009 (UTC)[reply]

Did it still have the same note? APL (talk) 20:00, 26 August 2009 (UTC)[reply]

Well, duh. Yes. If it was a different bottle now that'd be a coincidence.. Sagittarian Milky Way (talk) 20:12, 26 August 2009 (UTC)[reply]

Ah - but if it was the same bottle but a different message - it would be a conversation! SteveBaker (talk) 20:35, 26 August 2009 (UTC)[reply]

I was typing up a long detailed message in my other office, but had to run and shut off the computer without sending. Very briefly, you are going the wrong way. Chances are you will drift to the Indian Ocean, missing Africa all together. If you do hit Africa, it will be a long trip anywhere from about 1,000 to 2,000 miles (it is a circular current. The inside is shorter than the outside.) Your speed will be, on average, less than a knot. So, you are looking at a mile an hour (as Sagittarian Milky Way noted). Best luck will be about 40 days. Real experience will likely be much longer. Now, if you asked about going from Africa to South America (which is what I asked a long ago), you will get a completely different answer. -- kainaw ™ 20:34, 26 August 2009 (UTC)[reply]

Human Genetic Trait Pairings

What are some Human unusual genetic trait pairings? I mean, for instance, if you have Human genetic trait 'A' most likely you have Human genetic trait 'B'. I think there is one pairing that I am familiar with and that is if you have unattached earlobes, you most likely are right handed. But that can be wrong. --Reticuli88 (talk) 20:25, 26 August 2009 (UTC)[reply]

Maybe take a look at epistasis. You may be right, but if you're wrong, does that make it left? DRosenbach ^{(Talk | Contribs)} 22:10, 26 August 2009 (UTC)[reply]

The OP may be referring to genetic linkage and/or linkage disequilibrium. Genes that are located physically close to each other on a chromosome will be paired (to some extent), since the probability of them splitting up during meiosis gets smaller the closer they are. Thus, historically, Charcot-Marie-Tooth disease was known to be paired with specific Duffy antigen alleles, it turned out the genes responsible are relatively near each other.

You might also be asking about different phenotypes resultant from the same genes. For example, red hair is a genetic trait paired (at a high frequency) with pale skin and freckling. This is because loss of function alleles of the MC1R gene is largely responsible for all three phenotypes. I'm not familiar with the data the suggests that handedness is linked to ear lobes, though. Rockpocket 06:18, 27 August 2009 (UTC)[reply]

you are right, Rockpocket --64.148.9.225 (talk) 11:22, 27 August 2009 (UTC)[reply]

One well-known linkage is the "ginger" genes, which provide for both red hair and uneven skin pigmentation (which means both freckles and a tendency towards getting sunburns). StuRat (talk) 12:27, 27 August 2009 (UTC)[reply]

As stated above, that should be gene (singular). The same gene is (largely) responsible for both phenotypes. Rockpocket 17:37, 27 August 2009 (UTC)[reply]

And of course don't forget the old malaria vs sickle cell anemia story. Aaadddaaammm (talk) 19:33, 27 August 2009 (UTC)[reply]

Dulce Base/Nightmare Hall/Underground Tunnels

I read some supposed UFO conspiracy reports online about how there are vast networks of underground tunnels all around the world that, for instance, one can travel from Wyoming to Italy in a matter of hours or something crazy like that. If that were remotely true, wouldn't something or someone pick up on some vibrations, noise, etc? Is it technologically possible to create something underground where it can be virtually undetected by the human population? --Reticuli88 (talk) 20:37, 26 August 2009 (UTC)[reply]

There are a couple of different concepts here: can you detect the construction (yes if you want to); and is anyone trying to (probably not). Seismologists might be keeping an ear out for such noise, but they have a lot of data to look at and might not be very interested. But the trouble with such conspiracy theories is that they're quick to dragoon whatever resources are required to make the conspiracy so: we presume that the national geological services of the major nations will ibein on the act. There are very many other practical objections to the existence of such infrastructure. I'm reasonably confident that our lizard-like overlords probably take British or American Airways like the rest of us. --Tagishsimon (talk) 21:03, 26 August 2009 (UTC)[reply]

There have been proposals for such things - but certainly they couldn't be constructed without someone noticing. Forget noise and vibration just consider the size of the hole: From Wyoming to Italy is about 8,000 km. If the tunnel was big enough to get some kind of a super-sonic high-speed train into it, it would need to be (let's say) 3meters in diameter. That's 200,000,000 cubic meters of dirt. About ten million truckloads. Where the heck do you think you're going to hide ten million truckloads of dirt and rock - and how are you going to prevent even one of the 10,000 truck drivers from blabbing something about it to the press? How would the spectacular cost of this get covered up? Why on earth would anyone want it anyway? If you are some kind of high-up world leader, get someone to strap you into an SR-71 Blackbird and at Mach 3.2 (about 4,000 kph) and you'll make the trip in almost exactly 2 hours. This is so unreasonable as to be hardly worth consideration! SteveBaker (talk) 22:05, 26 August 2009 (UTC)[reply]

"Where the heck do you think you're going to hide ten million truckloads of dirt and rock?" Come on, the aliens would just use their anti matter ray to shoot a hole all the way through. Just focus it to 3m and aim through the end points, simple ;) Vespine (talk) 22:23, 26 August 2009 (UTC)[reply]

I'm sorry - how foolish of me not to have considered that! So I guess these tunnels are there to relieve the wear and tear on their (evidently faster than light) flying saucers due to shipping people from Wyoming to their research center in Italy where they can 'probe' them. The solution is obvious when you approach this with a mind that's clear of all of these rigid preconceptions. SteveBaker (talk) 12:07, 27 August 2009 (UTC)[reply]

200,000,000 cubic meters of rock, at a density of about 2.5 g/cm², equates to 500,000,000,000 kg. Ignoring where you're going to get the 500,000,000,000 kg of antimatter from, the 1 trillion kg of mass would convert to 9×10²⁸Joules, or, at the sun's output of 3.846×10²⁶ W, equals about 3.9 minutes of total solar output. Or, for just the amount of sunlight striking the entire earth (1.740×10¹⁷ W), 16,400 years of total solar input to the earth. I'd imagine you'd detect the digging by the fact that your eyeballs had been boiled. Besides, if Hollywood movies taught us anything, you dispose of the dirt by shaking it out of your trouser cuffs on the baseball field. Just look for an infield in Wyoming that's 265 km higher than the surrounding area. -- 128.104.112.102 (talk) 17:05, 27 August 2009 (UTC)[reply]

That's the vactrain idea; right now it exists only in some very preliminary paper studies, and in the minds of conspiracy theorists. The prevailing conspiracy theory (if such thing can be said to exist) does indeed claim a vast underground network of such tunnels, centered at Area 51 and connecting military bases and government buildings around the US. Of course, like all conspiracy theories, absence of evidence is taken (by such folks) to be ironclad evidence of a cover-up, and whether the cost, noise, vibration, or excavation-effects of such a monumental undertaking would be evident isn't important - The Conspiracy has eyes and arms everywhere, and those who can see can soon be disposed of. Steve asks "Why on earth would anyone want it anyway?" - the answer is simple - the reptilian humanoids who really control the US government need it to travel around - presumably from the big flat rocks they have in Nevada (to keep warm) to the hatch they have under the Resolute desk, so as to order their puppet B.O. around, and then back to Nevada for a hearty dinner of gerbils a-la-mode. -- Finlay McWalter • Talk 23:53, 26 August 2009 (UTC)[reply]

Reality check: smuggler tunnels under the Palestine-Egypt border certainly exist and have been kept secret for a while. Unreality check: there is alleged to be an entrance between the paws of the Sphinx to an Underworld. Cuddlyable3 (talk) 09:11, 27 August 2009 (UTC)[reply]

Our Smuggling tunnel article has some surprising stories to tell of tunnels from Canada and Mexico into the USA - as well as details of the Gaza strip tunnels to which you refer. Gaza Strip smuggling tunnels has more info about the Egypt/Palestine tunnels. However: in the former article - talking about a tunnel between Canada and the USA: "Authorities were alerted when a neighbour noticed the large-scale construction work being undertaken ... On inspection, it was apparent that tons of construction material was entering, and piles of dirt were coming out." - and this was for a relatively short tunnel by UFO-nut standards. However, the Gaza-strip tunnels only have to be secret at one end - removing excavated material at the non-secret end is fairly trivial. The problem with alien/UFO tunnels is that (like the Canada/US tunnel) both ends have to remain secret. SteveBaker (talk) 12:07, 27 August 2009 (UTC)[reply]

Sodium Sulphate solubility

See Sodium sulfate specifically the solubility curve, can anyone explain the 'knee' in the graph? Specifically does anyone know (or want to guess) 'exactly' what the species are that predominate before and after the knee.. please..expert attention only..ie no Yahoo! answers.. 83.100.250.79 (talk) 21:55, 26 August 2009 (UTC)[reply]

The paragraph adjacent to the graph in that article has specific information about the weird shape. DMacks (talk) 22:25, 26 August 2009 (UTC)[reply]

This (?):

This nonconformity can be explained in terms of hydration, since 32.4 °C corresponds with the temperature at which the crystalline decahydrate (Glauber's salt) changes to give a sulfate liquid phase and an anhydrous solid phase.

Does that mean that the decahydrate is dissolving without dissociation ie as an ion pair surrounded by lots of H2O, or as clusters of (Na2SO4.nH2O)_m with a surface covered in -OH's ? (A bit like a sugar or polyol dissolving)

..And that these clusters break down above 35C

I didn't expect the decahydrate to survive per se on dissolution.

Is this a well known thing - I don't recognise the process I described above from any text book. Or is something else happening?83.100.250.79 (talk) 22:35, 26 August 2009 (UTC)[reply]

Or is all the above wrong? (the behaviour can be explained by the solid phase change of Glauber's salt)

Is it known what glauber's salt dissolves as ie as fully dissociated ions, or as the species I described above? I was thinking melting point depression - but that might not work -ie there might be the same number of species on dissolution despite being different species. Plus the glauber's salt would just come out of solution anyway. Vapor pressure I woundn't expect to work easily because the two components of the solution both have quite high vapour pressures..?

What to do?83.100.250.79 (talk) 23:53, 26 August 2009 (UTC)[reply]

Cerium Sulphate solubility

(edited once) Also the solubility behaviour of Cerium (3) sulphate with temperature - it decreases apparently? How can this be explained - anyone know? Specifically an theoretical model that explains this behaviour (it seems a no brainer that entropy will increase on dissolution - yet it appears that may be wrong?) Can it be that the high charge of Ce3+ induces medium range order into the solvent - decreasing entropy- anyone know about this sort of thing? 83.100.250.79 (talk) 21:34, 26 August 2009 (UTC)[reply]

Maxwwell's Demon

In the thought experiment, known as Maxwell's demon, there exists a hypothetical "demon" that guards a trapdoor between two containers filled with gases at equal temperatures. By allowing fast molecules through the trapdoor in only one direction and only slow molecules in the other direction, the demon raises the temperature of one gas and lowers the temperature of the other, apparently violating the Second Law of Thermodynamics.

I know this is only a thought experiment but even so shouldn't there exist a degree of reality if the results are to be taken seriously? I don't understand how this should work if the temperature of the gas is the same in both containers the speed of the molecules would also be the same? OK there is bound to be one molecules speed that would be faster or slower but then the experiment could not have started with both containers of equal temperatures?

I'm not an expert in these things so keep it light if that's possible

Thanks —Preceding unsigned comment added by Makemineateaplease (talk • contribs) 21:48, 26 August 2009 (UTC)[reply]

Saying that the temperatures are the same only means that the average speeds are the same. There is always a range of speeds. Imagine you have a pool table with a few dozen balls on it, and you shake the table: would you expect all the balls, as they bounce back and forth, to always move at exactly the same speed as each other? —Preceding unsigned comment added by Looie496 (talk • contribs)

Temperature is a statistical result for a large number of molecules, and there are lots of faster- and slower-than-average molecules. In fact, virtually none of them are actually the average value. Rather, there is a Maxwell–Boltzmann distribution (yup, same "Maxwell" guy:) of values (the math can be pretty dense, but the graph in that section is a good executive summary of the result that relates to your question). DMacks (talk) 21:59, 26 August 2009 (UTC)[reply]

Good one. Thank you. —Preceding unsigned comment added by Makemineateaplease (talk • contribs) 22:19, 26 August 2009 (UTC)[reply]

Incidentally, Maxwell's deamon only seems to break the 2nd law when you think about it at a superficial level. In reality, it can be shown that the energy it has to expend to measure the speed of the atoms and the effort to open and shut the trap-door cause it to consume more energy than it creates - hence it no more violates the 2nd law than does your refrigerator. SteveBaker (talk) 11:54, 27 August 2009 (UTC)[reply]

The 2nd law is how you show that. --Tango (talk) 16:15, 27 August 2009 (UTC)[reply]

That argument always seemed like begging the question to me: "A:Does the 2nd law *always* hold? ... how about a situation like Maxwell's demon? B:No. Maxwell's demon can't work because it violates the 2nd law." - Great, we can prove that the second law isn't broken by Maxwell's demon if we assume that the second law is valid when analyzing Maxwell's demon. -- 128.104.112.102 (talk) 16:47, 27 August 2009 (UTC)[reply]

You can't show by direct empirical observation that there is no possible way to implement Maxwell's Demon. The only way is to show that it violates a law that we have lots of empirical evidence for. --Tango (talk) 17:57, 27 August 2009 (UTC)[reply]

Tango and 128 were right and Steve was wrong, or at least misleading. The historical sequence is:

(1824) I have invented the 2nd law of thermodynamics: here it is. Can you falsify it?
(1867) I have invented Maxwell's demon. I can't build one, but there seems no reason it would be impossible, and it falsifies the 2nd law. Can you falsify my claim?
(1929) Yes! The demon must consume energy, so if it is possible to build one, the law can still be correct if Steve's statement about energy is also right. Therefore the 2nd law is not falsified.

Today we believe that the 2nd law is true, so from that point of view we can use it to prove things about Maxwell's demon, but only from that point of view. --Anonymous, 22:38 UTC, August 27, 2009.

If Wikipedia has multiple server sites, where is the real encyclopedia image (the one that gets edited) currently?

One can imagine all kinds of possible weird speed of light-related edits due to c, the speed of light in fiber optic cable, the different server continents, near-simultaneous edits to the same section of the same article, and the already irrational nature of relativity. What if the 3,000,000th article was created by two different people in two different continents, had the same name, but different text, the first bits arrived in Florida within 3 milliseconds of each other, and then the server synchronized. The later article had a closer sending PC, but longer fiber-optic path. The first PC to send bits had slower internet access so it wasn't finished till the other already did. The PCs were very near one other server site, and far from the other. One article version consisted of only a curse word repeated and was speedy deleted by a bot in milliseconds. Then the other was only barely above auto-bot deletion and deleted by a human doing recent changes patrol. Both PCs sent the edits in the form of a fast radio signal to their own fast private servers very close, but only to some of the Wikiservers. They automatically decoded them and made the same edits on local PCs held by fellow paradox creating comrades with senses of humor. And as we all know, if they do this fast enough, these will affect the servers before the ones on the Internet, because electromagnetic waves travel 200 million miles an hour faster through atmosphere than through glass fibers. They also did this with geostationary satellite internet connections. Another unrelated article arrived at Florida in the intervening time. Or maybe it was two other copies of 3,000,000A and B but they were encyclopedic ones. Okay, I'll stop now. Sagittarian Milky Way (talk) 22:21, 26 August 2009 (UTC)[reply]

I think I drifted off half way through. You measure the thing at one place (e.g. the nominated master database) based on one event (e.g. the completion of a database append operation). You do not concern yourself too much with the manifold other ways of considering the matter lest you go mad and start posting completely inarticulate queries about the issue. --Tagishsimon (talk) 22:34, 26 August 2009 (UTC)[reply]

If there are/is more than one 'main version' then I think they must converse changes to one another - otherwise there would be serious issues when editing, which I believe Sag..MilkyWay is talking about. Often I see a delay when submitting... An auxillary question would be - if there is/are more than one main server - how much bandwidth do they use on average.?83.100.250.79 (talk) 22:41, 26 August 2009 (UTC)[reply]

You might read federated database. That article explains the methodology of the computer system architecture that Wikipedia (and in fact, most other large data processing systems) use. The distribution of data over many different computers follows deterministic algorithms for resolving conflicts. Somewhere, somehow, there is a serialization process which maps the parallel processing task (executed on many computers, possibly geographically dispersed) into a serial-order-equivalent task - this is a basic tenet of modern parallel computing algorithms. You might also want to read Help:Edit conflict, which describes the result when two "simultaneous" edits cannot be automatically resolved by the algorithm. One or both edits fails to commit to the database, and it is up to the humans to either retry or abandon the edit(s). You might also be interested in data hazard, which formally defines (from the standpoint of computer science) the situation you have described. The computer can easily recognize that you have performed a "Write After Write" hazard - and it may choose from a wide variety of recovery methods to properly handle this. (Most commonly, the second write will be rolled back). Note that in the formal definitions of data management, a "delete" is the same as a "write", as they both involve a committed modification of data. Nimur (talk) 22:46, 26 August 2009 (UTC)[reply]

Okay, conflicting parts simply don't become part of the database, then. It always boils down to an edit conflict. It is just funny if it could be possible to have slightly disparate versions floating around, and there really is no absolute time frame of reference in relativity and then the servers have to synchronize. How often do they sync? I've seen changes to widely used templates that took 20 minutes to cascade down, maybe this is unrelated to synchronize frequency? Sligthly drunk. Usually this is a thing for the Internet Oracle, but I really wanted to know. Sagittarian Milky Way (talk) 23:27, 26 August 2009 (UTC)[reply]

There's only one server, but that's masked by degrees of caching. The database server has several read-only slaves, which try to replicate it in real time, but sometimes there's a lag (it's rarely more than 30 seconds). Then there's memcached caching, which caches pre-rendered(to HTML) fragments of articles. And then (mostly for signed-out visitors) there's squid webcaches in front of the web servers. So for editors there's a single definitive copy of the encyclopedia, but for visitors it's always a delayed (and often version-skewed) copy; visitors overwhelmingly don't know and don't care that they're lot looking at the absolute latest thing, but obviously for editors that's imperative. -- Finlay McWalter • Talk 23:37, 26 August 2009 (UTC)[reply]

And then there are templates, update to which must be applied to each instance of use of the template (that is not subst'd into the page); the amount of time to do the updates will depend in large part on the number of articles using the template, and the size of the job queue. Slightly drunk. Excellent. --Tagishsimon (talk) 23:49, 26 August 2009 (UTC)[reply]

The other issue is that the conversion of pages from the internal Wiki markup language to HTML+JavaScript is cached so that the task doesn't have to be repeated over and over when the same page is viewed by many people in quick succession. That process can sometimes lag the edit queue - so you make a change - and it's accepted without an edit conflict - but it takes a few seconds for that to be reflected on the viewable page. SteveBaker (talk) 11:50, 27 August 2009 (UTC)[reply]