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May 26

Example of a distributed parameter system

Can someone give me an example of the equation for a distributed element model? For example, for a circuit with an inductor, $V=L{\frac {dI}{dt}}$ is the ODE for the lumped parameter system. Can someone give me an example of a distributed parameter system? 203.45.159.248 (talk) 02:23, 26 May 2014 (UTC)

Sure: the telegrapher's equations provide differential equations to define the voltage at each point in the signal path. You can do the same thing for the derivation of the radar equation, but that equation is conventionally simplified to solve for power received at a fixed location.

The key concept is that your lumped-element equation is an ordinary differential equation in one variable (time). When we model a distributed system, we must use a partial differential equation with variables for time and position. The telegrapher's equation is of course simplified to one position-parameter: distance along the transmission line. In full three-dimensional representation - like a full-form RADAR scatter solution - we need three position variables x,y,z; and before long, we are actually solving the general form of the wave equation, as expressed by Maxwell's equations, with electromagnetic parameters specified for every point in the model-space. Nimur (talk) 03:50, 26 May 2014 (UTC)

OK. Thanks for your answer. I see the full telegrapher's equations under "Lossy transmission line" on the article. I am interested to know the three-dimensional equation, and how that reduces to Maxwell's equations. Also, are L, R, G, and C functions of position and time too? 203.45.159.248 (talk) 06:25, 26 May 2014 (UTC)

Those parameters might vary with position. That will make the solution more difficult - at a certain point, an analytic solution is impractical, and we would use a numerical method to solve.

For three dimensions, we have many options. I would solve the nonhomogeneous form of Maxwell's equations, where the nonhomogeneous term is a field function describing the resistance and inductance (in terms of permittivity and permissivity). I would solve this using the staggered cell method, which is pretty stable but slow. A friend of mine works for a small company and writes commercial software to solve this equation by the Galerkin method. A few other options include solution by Fourier transform or solution by multiresolution methods. All of these fall under the giant umbrella of finite element analysis, but they are simply techniques to deal with the many many terms in these equations.

Unless your simulation environment is mostly empty, a closed-form analytic solution is probably impractical. Nimur (talk) 15:19, 26 May 2014 (UTC)

Also, at the reference section in our article lists several of the standard textbooks on this topic. Nimur (talk) 17:07, 26 May 2014 (UTC)

What can be taken to heal mouth ulcer?

Zonex shrestha (talk) 04:42, 26 May 2014 (UTC)

We have an article on mouth ulcer which explains there are different kinds. If your interest is academic you might want to narrow down your question. If you're looking for treatment for your mouth ulcer, people here can't readily diagnose which kind you have, and there are some people who are dogged about preventing people from even trying. Wnt (talk) 04:59, 26 May 2014 (UTC)

Zonex, the majority of your questions can be answered by googling or searching wikipedia. Try those first and come back if you have questions that weren't answered by your searches. Justin15w (talk) 15:11, 26 May 2014 (UTC)

Banana worms

I often hear of stories of people seeing worms or parasites in bananas but yet I've never seen one and can't even find a picture on the web. Are there really works which live inside bananas or is it just a figure of people's anxieties about parasites? — Preceding unsigned comment added by 82.40.46.182 (talk) 15:09, 26 May 2014 (UTC)

There are a few that attack the roots, and we even have some pictures. Please see List of banana and plantain diseases#Nematodes, parasitic. Not sure whether any get to the fruit.--Shantavira|^{feed me} 15:26, 26 May 2014 (UTC)

Our article on banana has a section on pests. Most of the pests that affect the fruit are fungi. Nimur (talk) 15:31, 26 May 2014 (UTC)

Fruit fly larva are "worms". And, as you know, "Fruit flies like a banana, but time flies like an arrow". StuRat (talk) 15:35, 26 May 2014 (UTC)

I believe the OP is referencing a fairly recent urban legend making the rounds that the little smutzy bits at the end of each banana (i.e. the little chunks that usually stay in the peel or you otherwise pick off and throw in the trash) are parasites or discrete living things of some sort. Complete nonsense. There's a bit of background here. They're slightly fibrous and a bit squishy, but harmless. Matt Deres (talk) 01:32, 27 May 2014 (UTC)

Perhaps they are talking about soft/semi-dried bananas (like this) popular in S.E.Asia. Worms are pretty common in those. They're still delicious with the worms. Sean.hoyland - talk 07:20, 29 May 2014 (UTC)

May 27

Synthesising milk in bioreactors?

Could milk be made in bioreactors using engineered bacteria to make the proteins? --78.148.110.113 (talk) 02:36, 27 May 2014 (UTC)

Probably, but why ? Are you hoping to make it more cheaply than from actual cows ? Are you hoping to make it healthier ? If so, removing the fat from cow's milk or using one of the many substitutes, like almond milk, soy milk, and rice milk, might be a better option. StuRat (talk) 04:28, 27 May 2014 (UTC)

It's hard to do better than real casein when it comes to colloidal stability. Nobody likes milk that precipitates on dilution or heating, and that's one thing that milk substitutes generally don't get right. To get back to the original question, there's no real reason you couldn't make a construct that codes for coexpression of certain key milk proteins. But, a lot of them have substantial glycosylations and disulfides, so you'd want to use a higher organism to guarantee appropriate post-translational modifications, as opposed to -say- an E. Coli based expression system, I'd bet you could get CHO cells to do this quite well. The real issues is that I don't really know why you'd ever actually want to make completely recombinant milk. It would give very precise control over the composition of the resulting milk and probably eliminate any potential immunogenicity of the type commonly associated with cow's milk, but from a business standpoint, would be very hard to market. Laypeople are already basically convinced that biotechnology is witchcraft. (+)H₃N-Protein\Chemist-CO₂(-) 14:56, 29 May 2014 (UTC)

The basic problem I see is that when making milk you want to keep your nutrient stocks, active enzyme, production apparatus, and finished product all separate. To turn precursors to milk with E. coli, you have to completely convert all the precursor material into milk with nothing extra or left out, then strain out all the E. coli without leaving so much as a flavor of them behind. It seems a lot easier to do this with a macroscopic organism that is evolved over tens of millions of years to do the process efficiently. Wnt (talk) 23:08, 29 May 2014 (UTC)

I'd say that, on evolutionary timescales, the innovation of turning cows into industrial-scale milk factories is fairly recent, and not especially efficient, probably doesn't do much for the cows either. Besides, people don't seem to have issues with using microorganisms to make consumables, and for the most part using cell culture to make biologics seems pretty uncontroversial as well. And, as I said before, you could generate completely non-immunogenic milk using some very simple biotechnology that's already used for the production of pharmaceuticals. Besides, filtering cells out of culture media isn't especially challenging. It's purifying down to a single component that's actually the difficult part, which as you point out wouldn't need to be done in this case. But, the point is still moot, even if it's more efficient and produces a better product, would still be impossible to market. If no one will buy it, then it's still pointless. (+)H₃N-Protein\Chemist-CO₂(-) 13:12, 30 May 2014 (UTC)

Cosmic Microwave Background radiation

According to Fred Hoyle c.s.,

“It has been known for many years that the energy density of the microwave background is almost exactly equal to the energy released in the conversion of hydrogen to helium in the visible baryonic matter in the universe [..] Thus the energy released in the production of this He through the conversion H → He is 4.5 × 10^{– 13} erg/cm³, which if thermalized gives a radiation field of 2.78 K.”*

According to present measurements the temperature of the CMB is 2.72548 K.

My question is

1. Does the temperature difference –Hoyle’s 2.78 K versus 2.72 K – invalidate Hoyle’s statement that the CMB may originate in the H → He conversion?
2. How is radiation is thermalized?
3. How does the baryon-to-photon ratio determine the temperature of the CMB? Has this ratio been set to produce the desired temperature or is it measured –and, if so, how?

• From: Further astrophysical quantities expected in a quasi-steady state Universe Hoyle, F; Burbidge, G; Narlikar, J.V.; Astron. Astrophys. 289, 729-739 (1994), Ch. 4.1, http://adsabs.harvard.edu/abs/1994A%26A...289..729H

Antonquery (talk) 03:06, 27 May 2014 (UTC)

Woah, dense questions! I'd love to tackle all of them, but let's start with the easiest: how is radiation thermalized? We can throw some handwaving around about poynting vectors and energy density... if you spend any reasonable time with those equations, somebody (either you or your intellectual superior) will eventually derive a relation between radiation temperature and energy density. But I couldn't remember exactly how that worked out... so I pulled out Pacholczyk's Radio Astrophysics, which has an appendix working the math out. In broad brush strokes, we start out from the plane wave solution to Maxwell's equations, in empty space. From this, we write the intensity of the radiation in terms of its field amplitude. Apply the Poynting theorem (Pacholzyk spells this "Pointing") to relate intensity to flux. Then some gorey math to transform the beam to equivalent Stokes parameters (just a different coordinate frame to completely define an arbitrarily-polarized wave)... literally four pages of heavy mathematics later, and we can write this as a Planck function - which you obviously already know is nearly the blackbody radiation equation..., and presto, we have a effective temperature directly derived from an energy density. Just putting a bunch of joules in a box means that there's a corresponding temperature, no matter how you arrange that energy. (Of course, that energy is, in this case, arranged as oscillation of electric and magnetic fields). My textbook then cites Chandrasekhar, Radiative Transfer (1950), as its reference... and that's probably the direct path to the original source of this particular unit of knowledge (as discovered by our species). So, there you have it: electromagnetic radiation is thermalized because it inherently has a radiation temperature. Nimur (talk) 05:51, 27 May 2014 (UTC)

... It seems that your Question 3 is answered by Hoyle's reference to his own 1968 lecture, which is available on JSTOR or from the publisher. (On closer inspection, it's the transcript of his award lecture). If I can get access tomorrow or later this week, I'll read through it and report back. I don't think we can answer Question 1 until we know how he arrives at the 2.78 K number, which he calls "fortuitous." I think your answer hinges on whether that value is intended to be very accurate, (i.e. no handwaving). Nimur (talk) 06:27, 27 May 2014 (UTC)

Fascinating lecture. It can be accessed at no cost if you create a JSTOR account.

A few more comments: there is no mention of "baryon to photon ratio." The Hydrogen-Helium conversion rate appears to be a direct observation, made consistent with known nuclear chemistry.

Based on the number of significant figures, and based on Hoyle's collection of several disparate sources of radiation lumped together by "approximately" equal temperatures, I doubt he would have worried too much about accuracy to a few hundredths of a Kelvin. You can read his paper to make up your own mind; but he lists several sources that are equal in order of magnitude, and calls this an unlikely coincidence.

Whether his thesis has merit is a different issue altogether; but I don't think a 2.72 K measuresd, vs. 2.78 K predicted, effective temperature in itself is sufficient to invalidate his theory. Nimur (talk) 07:14, 27 May 2014 (UTC)

Fred Hoyle: “It is often stated that the big bang cosmology explains the microwave background. It does no such thing, of course. Big bang cosmology assumes the microwave background, and it does so in a quite arbitrary way, requiring the baryon-to-photon ratio to be close to 3 × 10 ^{– 10}, without offering a convincing explanation for this number, which could just as well be anything at all.” *

If what Hoyle says is true, then how does the CMB temperature relate the baryon-to-photon ratio?

* From: A quasi-steady-state cosmological model with creation of matter, Hoyle F., Burbidge G., Narlikar J.V., 1993 The Astrophysical Journal 410: 437 – 457, 1993 June 20 p 443, http://adsabs.harvard.edu/abs/1993ApJ...410..437H Antonquery (talk) 02:08, 29 May 2014 (UTC)

Nimur, the thermalization problem is how you get from H → He fusion in stars to a near-perfect 2.7 K blackbody filling all of space, not how energy is related to temperature.

I'm not well informed on this, so take what I say with a grain of salt, but re question 2, the paper attributes the thermalization to scattering by dust, "much of it in the form of iron needles". Re question 1, it also mentions a prediction of 2.68 K for the blackbody temperature, a full 0.1 K away from 2.78 K, so it's plausible that with more tweaking they could get 2.73 K. Re question 3, I don't know if the baryon-photon ratio is related to the CMB temperature but it is related to the anisotropy of the temperature via acoustic oscillations. Measuring the ratio and setting it to produce the desired (observed) result are the same thing, so the answer to that part is both. In addition to the temperature anisotropy, I think the ratio is independently constrained by big bang nucleosynthesis and by direct measurements of the baryonic matter and CMBR photon density in the present-day universe, but you could take any of those to be the measurement and the others to be tests of a prediction based on the measured value. There isn't really any difference.

Ned Wright's page on steady-state cosmology may be a useful source of references, and it also explains the reasons that no one takes Hoyle et al seriously any more. Wright mentions "carbon and iron whiskers" as the agents of thermalization. -- BenRG (talk) 08:34, 27 May 2014 (UTC)

Everything thermalizes. If you have a bunch of hydrogen nuclei, and they undergo fusion, then the individual nucleons have kinetic energy. After some time, the ensemble will arrange itself to follow a Maxwell distribution. Or, if you have a bunch of photons, and you let them bump around for the lifetime of the universe, it too will start following a Maxwell distribution. I think the question here was whether the particular spectrum we see in the microwave background would be unique to big-bang processes, or if it could come from any of several other sources (including thermalization of energy released during stellar nucleosynthesis and galactic formation). Hoyle clearly believes that the cosmic background radiation spectrum is not unique, and could be explained by any of the five or six possible sources he lists. Most other scientists believe that the cosmic background radiation is not explained by stellar nucleosynthesis: there is a reputed mismatch in the spectra we observe vs. the spectra predicted by H->He fusion; hence, the "problem." It is this specific problem that caused many cosmologists to refute Hoyle's ideas. But, I guess it's up to each individual to make up their own mind about whether this actually is a "problem," based on your confidence in our observations and theories, and your willingness to accept or reject any particular mismatch. Nimur (talk) 16:51, 30 May 2014 (UTC)

Some of the fusion energy to convert H to He is also "wasted" on energy in relic neutrinos (aka Cosmic neutrino background) which will account for some of the missing energy too. Also don't expect that the average density of He or H in the universe is accurately known. Graeme Bartlett (talk) 11:09, 27 May 2014 (UTC)

Thank you all very much for your reaction!

While I do reject Hoyle’s Steady State Theory, I also cannot accept the Big Bang hypothesis as it is based on a conceptual fallacy –which is why I’m trying to find an alternative explanation for the CMB.

My question is how the CMB temperature is related to the baryon-to-photon ratio (see quote above, the bold text) and whether Hoyle’s idea that the CMB originates in the H → He is a realistic explanation?

Or does the difference between the 2.78 K H → He and the measured 2.72 K discredit this idea decisively? Antonquery (talk) 02:19, 29 May 2014 (UTC)

No one is going to care about the small temperature difference.

If you assume that the CMB obeys a blackbody radiation distribution (and it certainly appears to) and is uniform through space, then the photon density is directly linked to the apparent temperature.

In standard big bang cosmology, the universe was hot enough near the very beginning to allow for photon-photon interactions that would create matter-antimatter pairs (pair creation), which would have led to an initial baryon-to-photon ratio of approximately one. As the universe cools, and pair creation ceases to be common (roughly 10 seconds after the Bang), and the existing matter-antimatter pairs would annihilate and convert back into photons. This would result in far more photons than baryons. The residual density of baryons that remain after the annihilations is controlled by the initial matter-antimatter asymmetry, which is not well understood theoretically, and hence we can't predict the resulting baryon density. So, while photon density is tightly constrained in the theoretical underpinnings of the Big Bang model, baryon density is poorly constrained. Hence, the baryon-to-photon ratio is not well constrained by fundamental theory. That said, baryon-to-photon ratio does play a role in big bang nucleosynthesis. While we don't know why the baryon-to-photon ratio takes on a particular value, we can say that only a limited range of values are consistent with the relative abundances of hydrogen, helium, and other primordial elements we observe in the universe. We can further observe that the currently measurable baryon-to-photon ratio is consistent with what we expect based on the observed element abundances. (Big Bang cosmology predicts that the ratio will not have changed significantly since the end of matter-antimatter annihilation.)

It is worth noting that the CMB doesn't just have a blackbody spectrum, it is probably the most perfect blackbody spectrum known in nature. Most of the time when blackbody radiation is created by a physical object you see an imprint of the molecular structure of the physical object on the resulting radiation. It seems very implausible to me that any physical process could convert stellar radiation from fusion into microwave background radiation (i.e. the "thermalization") without leaving a signature of the underlying physical process on the radiation spectrum. Dragons flight (talk) 03:38, 29 May 2014 (UTC)

Gull knows how to turn on tap/faucet to get water?

See this video, found today after randomly browsing gull vids. Is this something that we already knew that they were known to do? Never seen or read about anything like it myself. --Kurt Shaped Box (talk) 07:16, 27 May 2014 (UTC)

I'm no "expert" on gulls, pigeons and chickens. But I have spent a lot of time watching them, just as a consequence of laziness. They certainly do have sharp eyesight and long-term memory, so I don't doubt this bird's motive was drinking.

But without knowing the backstory, exact shape or flavour of the tap, s/he may have been merely pecking at it, until something more interesting suddenly came along, for unknown reason. If I just happened to wander through the end of a rainbow, and instinctively caught the bright, loud leprechaun to get rich, I'll still have no idea why that (allegedly) happens.

We're not so different, mammals and birds. One huge similarity is how we prioritize water on a warm day. But priorities aren't always goals. It'd be nice to see some time-lapse birds around taps, and get to the bottom of this. InedibleHulk (talk) 07:42, May 27, 2014 (UTC)

If chickadees can figure out how to open milk bottles, then why do you suppose a seagull would be any less capable of figuring things out? 24.5.122.13 (talk) 08:24, 27 May 2014 (UTC)

I dunno, maybe I'm wrong, but biting a hole in something to get at what's inside (which gulls do all the time too!) doesn't seem to me anyway, to be as much of a leap of intellect as switching something on. Seems to be more of an abstract thought... --Kurt Shaped Box (talk) 18:47, 27 May 2014 (UTC)

light bulb air conditioning savings?

Suppose you replace 10 85-watt incandescent bulbs that are on for 10 hours per day with LED bulbs that use 9.5 watts. Is that going to make a noticeable difference in the electricity used for air conditioning, or is it negligible? (I'd say that 10 US cents per day is not quite negligible.) Bubba73 ^{You talkin' to me?} 07:31, 27 May 2014 (UTC)

This is a common question on Reference Desk. You might like to search the archives.

The answer is, it depends. Let's say its mid summer where I live. The diurnal mean ambient temperature is about 28 C. That will make me run the aircon on cooling all day long. To need 10 x 85 watt bulbs, you'd own a mansion with 10 rooms and be very wasteful. Let's be more realistic - my house has 1 kitchen, 1 laundry, 1 living room, 2 bedrooms, 2 studies/offices, and 3 toilet/bathrooms. Total 9 rooms. Each room except the kitchen and living has ONE 42 watt bulb, kitchen and living rooms each have 2 x 42 watt bulbs. On an average day all rooms except bedrooms, bathrooms & laundry has lights on 12 hours per day. Bedroom, bathrooms and laudry average less than one hour per day 0.5 hour per day - lets forget them.

So I have 5 x 42 W x 12 / 1000 = 2.5 kilowatthours per day consumption. The central aichon is rated at 9 kilowatt cooling and just manages to cope with the worst of summer. It's 40 years old and has a Coefficient Of Performance (ratio of cooling to consumption) of 2.2 (typical for its type). So if it has to shift out 2.5 extra kilowatt hours due to the lights, it will draw an extra 1.12 kilowatt hours. So the true cost of lighting to me is 2.5 + 1.14 ie 3.6 kilowatt hours per day.

Now if I replace all bulbs with LEDS, I'll save approx 3 kilowatthours per day, worth about 48 cents at the rate my power company charges.

Now, let's say its winter. Where I live, mid winter diurnal mean is about 16 C, and that means I run the aircon on heating mode all day. So the 2.5 kilowatthour draw of the lights ease the laod on the aircon, causing it to draw less. In heating mode its COP is only about 1.9, so the DECREASE in aircon draw (due to less heat required) is about 1.3 kilowatt hours. So my true cost of lighting with bulbs in winter is about 2.5 - 1.3 = 1.2 kilowatthours per day. If I replace all bulbs with LEDS, the true lighting cost is now reduced by about 17 cents.

Lets say I replace the aircon with the latest type with invertor unloading and economy cycling. I might get a COP of about 3, only a small improvement but I would save about 70 kilowatt hours per day, worth about $10 per day. It happens my total energy bill (lights, aircon, water heating, cooking, appliances, etc) is about $16 to $18 per day.

The moral of the story is that while more efficent LED lighting will save energy, who in their right mind cares? You and I would do better by carefully looking at what really pulls the power. When I replace the hot water system (they last about 10 years), I'll go for the heat pump tupes now available - that will save dollars per day, not cents.

Note that I have a somewhat large house, and work as a consulting engineer from home, so my power bill is quite large. Most would have a pwer bill much lower.

Floda124.182.50.125 (talk) 08:07, 27 May 2014 (UTC)

(ec)Total power used by incandescent lights = 8.5 kWh/day

Total power used by LED lights = 0.95 kWh/day

How efficient is the AC?

According to http://energy.gov/energysaver/articles/room-air-conditioners a reasonable Seasonal energy efficiency ratio (SEER) for modern room air conditioner is 10. EER is the BTU/h rating of the AC divided by the power consumption in kWh.

We need to convert between BTU and kW so that we use the same units for heat in and heat out. According to British thermal unit 1000 BTU/h is approximately 293.071 W.

The incandescent bulbs are therefor adding 8500/293.071 ≈ 29 BTU of heat to the room per day.

An AC with a SEER of 10 will consume 2.9 kWh to remove that much heat from the room per day.

The 950Wh/day from the LED lights converts to 950/293.071 ≈ 3.24 BTU

An AC with a SEER of 10 will consume 0.324 kWh to remove that much heat from the room per day.

So the total electricity saving (all other things being equal of course) by switching from incandescent to LED lighting is:

Incandescent lights - LED lights: 8.5 - 0.95 = 7.550 kWh

AC power saved 2900 - 324 = 2.576 kWh

Total daily electricity saved 7.550 + 2.576 = 10.126 kWh, a significant saving in anyone's currency! Roger (Dodger67) (talk) 08:20, 27 May 2014 (UTC)

Why mess about with BTU's? The heat put out by incandescents is, in SI, measured in watts. You can stay in watts for the whole time - much simpler. The heat shifted by an aircon is measured in kilowatts, the electrical power input is also measured in kilowatts. That's why the aircon industry uses the term COP (coefficient of performance), which is the ratio of heat shifted (in kilowat hours) to the electrical input (in kilowatt hours). Typical older domestic aircons have a COP of about 2.2 to 2.5. It can be improved by invertor techonolgy and other modern tricks. It would be even better if they had not banned freon.

Who the hell is going to run 10 x 85 watt globes unless they are very rich and wastefull dudes? An 85 watt glode will overheat in a standard light fitting anyway.

Floda 124.182.50.125 (talk) 08:36, 27 May 2014 (UTC)

It would indeed have been easier to work only in SI units but the sources I found used BTU, so I had to do the conversion. I chose to answer the OPs question as asked and not to create a totally different scenario. Roger (Dodger67) (talk) 09:09, 27 May 2014 (UTC)

Thanks all. My kitchen has nine can lights, plus two other lights in a fixture. These would be 65 watts each if they were incandescent. The house my father is in has a lot of 85-watt PAR 38 incandescent bulbs all over the house. I think there are at least 10 in the kitchen/dining/living area - probably a few more. My air conditioner is SEER 10 but the ones there are newer and should be more efficient. But from the figures above, it looks like the a/c savings are about 1/3 as much as the savings of LED over incandescent, when a/c is needed, which is about 250 days/year here. Bubba73 ^{You talkin' to me?} 16:38, 27 May 2014 (UTC)

When I ran the numbers for my house, it paid off nicely to switch from incandescent to CFL bulbs, but the additional step to LEDs did not make economic sense, because the energy savings relative to CFLs is minimal, and the purchase price is on the order of 20 times more for LEDs than CFLs here. There's also an oddity in CFL pricing here that 60 watt equivalent (13 watt actual) CFLs cost half as much as 40, 75, or 100 watt equivalent bulb purchases, and anything bigger than 100 watt equivalent is prohibitively expensive. I therefore purchased 7 floor lamps, at < $20 each, which accept 5 bulbs each, and I put the cheaper 60 watt equivalent bulbs in each socket, for 300 watts equivalent, and 65 watts actual, per lamp. I also retrofit a lamp which only had 3 sockets with a couple socket splitters, so I can put 5 bulbs in there, too. So, I can light every room this way now, and only have to pay 50 cents when I replace a 60 watt equivalent CFL, which is rarely, in any case.

I also have a 300 watt halogen floor lamp, but I've concluded that I should only use it during winter, and in the room where I am located, as it's rather like running a lamp and an electric space heater at once. (This can actually be beneficial form of zone heating, in winter.)

As for recessed "can lights", I used to have those, but concluded that they were absurdly inefficient, in that they only light a small spot directly underneath them. So, I can see why you might need so many of those to light a room. A light fixture in the middle of the ceiling is far more efficient. To verify this for yourself, I suggest you turn on the 9 can lights in your kitchen alone, and then the 2 fixture lights alone. I'd bet you get as much light or more from the 2 fixture lights.

One last comment on lighting is that you need light-colored walls. Dark wood paneling has the ability to absorb as much light as you shine on it, and still keep the room dark. StuRat (talk) 17:24, 27 May 2014 (UTC)

We have all light-colored walls, except for the dining room.

I don't like CFLs because they take so long to come on and get dimmer as they get older. I'm not taking out working CFLs to put in LEDs, though. And sometimes they start buzzing. And some CFLs last a long time (I've got some that are 11 years old) and some don't. I put CFLs in the kitchen when we remodeled it in November 2012 and already three of them have died (one today).

In the kitchen, seven of the cans are on one switch and two are on another switch. The two in the fixture are 40-watt equivalent each. Seven cans are much brighter than those two.

BTW (to all), I knew about the direct electricity savings. I was asking about additional air conditioning savings. I had googled and found it discussed in some places, but didn't find any figures, or even estimates. Bubba73 ^{You talkin' to me?} 18:35, 27 May 2014 (UTC)

I, like just about everyone else, have found that CFL's don't last long - around 4 to 12 months (varies depending on brand), which is not as good as incandescents. That makes them uneconomic. So I've given up using them, except in bathrooms. They are good in bathrooms because of their slow warm up. If I get up for a pee in the middle of the night, I'm not blinded by the sudden large amount of light you get from other types. I used to fit 25 watt incandescents in bathrooms/toilets, but sometimes you need a good light. I tried LED lighting in my home office, but the colour is not as good as incandescents. 60.230.250.114 (talk) 00:46, 28 May 2014 (UTC)

CFLs last for years for me. You can't use them where heat is an issue, like in those "cans", or where they will constantly be turned on and off, like when connected to a motion sensor. And you need special CFLs for dimmer switches or "instant on" ones where that is important.

As far as an estimate, I'd say just doubling the direct electricity savings, in summer, is a rough way to estimate your total savings. That is, the electricity wasted as heat requires roughly the same amount of electricity to remove that heat from the room. Some factors would push that up, like A/C not being 100% efficient, while other factor keep the costs down, like using more efficient methods of cooling, such as fans in windows or heat pumps, or not needing to get the temperature all the way back down at night. Also, the excess heat from incandescents is a slight benefit in winter, when it reduces your heating bill a bit. StuRat (talk) 03:35, 28 May 2014 (UTC)

They do seem to last a long time for most of us. I wonder if it would be worth checking your house voltage with a multimeter to see if there's something abnormal about it that could be wearing them out sooner. (I think low voltage would do that...) Wnt (talk) 18:27, 28 May 2014 (UTC)

An incandescent lamp (or a CFL or an LED) is a 100%-efficient means to convert electricity into heat. Even the light it produces turns into heat when it's absorbed by something. That means that if you're heating your house with electricity, the light source is costing you precisely $0.00 to run (assuming it's in a room where you heat - an outside light would be different). If you're using some form of energy that's cheaper than electricity to heat your house then it's a different matter...but in that case it's not the direct cost of the electricity used to run the lights that you should care about - it's the ratio of the cost of electricity to the cost of whatever energy source you're using. If you're air-conditioning your house then it's a different matter...in that case, you care a lot about how much energy your lamps are using because you have to pay three or more times that much to get that energy out of your house again.

The same thing is true of refrigerators and things like that. How much does it cost to run your refrigerator? Well, it's a 100% efficient means for converting electricity into heat - so the cost is zero...if you're electrically heating the room that it's in.

So the answer here is really subtle...it depends on where the lights are, how you are heating (or cooling) your home and a bunch of other factors. One consideration is that incandescent lamps typically burn out after 1,000 to 2,000 hours...LED lamps have such long lives that we don't really know how long they last because plenty of LED's that were made around about the time when they were invented are still running. Sure, incandescents are pretty cheap to replace - so the cost per hour is a small fraction of a penny - but if you have to drive to the store to buy a new one when the old one dies right when you need it - then the cost will be considerably higher. SteveBaker (talk) 15:48, 28 May 2014 (UTC)

I don't see how you can justify including the cost to drive to the store in the equation, any reasonable person would stockpile them and/or wait until they were going to the store, anyway. The price of both incandescent bulbs and CFLs seems so low that you can ignore it as insignificant, in the calcs. LEDs are a different matter, though, as they are far more expensive. Also, even with an indoor light, presumably some light escapes through the windows. StuRat (talk) 18:48, 28 May 2014 (UTC)

"So the answer here is really subtle" says SteveBaker. Well, too subtle for Steve anyway. He's written a lot of nonsense. Well an incandescent lamp, fridge, TV, and the like when enclosed in a building are indeed 100% efficient at converting electricity into heat, it does not mean that in an airconditioned home in heating mode that the cost of lighting, fridge etc is zero. As airconditioners do not somehow convert or ansorb heat, but shift it from one place (outside) to another (the inside), the electricity can be a lot less that the amount of heat shifted. As reported above, a typical ratio (COP) for a domestic aircon is about 2.2. That means the heat shifted is 2.2 times the electicity consumed. Aircon plants with chilled water circulation in large multistorey buildings can have a COP as high as 9. So, if a home is being heated by aircon pulling (say) 4 kilowatts electricity average (implying the transport inside of 8.8 kilowatts heat), and you turn on 1000 watts of lighting, the aircon now has to supply only 7.8 kilowatts heat average to maintain the same temperature, so its electricity consumption will drop by 1/2.2, resulting in a total power consumption of 4 -1/2.2 + 1 = 5.45 kilowatts. So the cost of lighting is NOT zero like Steve said, it's the price of 0.45 kilowatts, as was was essentially said in 2 earlier posts.

And if your electric heating is not aircon but is a bar radiator or similar, the cost of lighting still isn't zero. While aircon heatpumping is space heating, you can save considerable energy (even though for a bar radiator the electrical input exactly equals heat output) because you don't neeed to heat the whoile room. You just have the bar radiator close to you, so it heats YOU and the room as a whole doesn't need to be raised to the same temperature you'd need with aircon heatpumping. This means that you don't get the confort benefit from the lighting heat, so you won't turn down the bar radiator heat because the lights are on. So the cost of energy for lighting is in this case 100%.

And StuRat is right, anyone with a lick of sense will, and indeed does, keep a stock of incandescents and CFL's on hand.

SteveBaker is wrong about LED srvice life too. Those old LEDS made 30, 40, 50 years ago were milliwats size intended as indicator lights. They generate light (red or whatever colour depending on the semicondonductor used) directly by diode action and were rated conservatively. Their service life is essentially infinite. LED's inteneded for room illumination use dyes to convert the diode radiation to a more usefull light spectrum for illumination, and are not rated so conservatively. For these two reasons, their service life is finite, and very much dependent on how good the cooling (heaksink) is. Since heatsinks cost money and take up space, their is strong commercial imperative to provide the minimum the manufacturer can get away with. I do agree that LED lighting made by a reputable manufacturer and correctly installed will last a lot longer than incandescents or CFL's, the service life is not as SteveBaker claimed.

Having said all that, you'll find, as was said above, that in Western homes with all manner of electric appliances, that the practical impact on energy consumption of lighting, even with incandescents, is very low. So low, that if you seriously want to save energy, to save money or be kind to the planet, you should look at other factors - such as building construction with good insulative performance, aircon units with high COP, etc. Or just get used to setting your aircon temperature settings a couple of degrees lower in winter or higher in summer. You only need to buy an aircon with a slightly higher COP to save more electricity than you'll ever save with CFL or LED lighting. Another trick is using local instant-on water heaters for the kitchen and toilet washbasins. This means that energy isn't wasted filling a long length of pipe up with hot water everytime somebody wants to wash dishes or wash their hands. With a couple of teenage girls in the house, the energy savings here can be quite a bit higher than the cost of lighting.

Floda 58.166.219.242 (talk) 12:45, 29 May 2014 (UTC)

What you are calling air conditioning sounds like what we call a heat pump, in the USA. Specifically, a regular air conditioning unit has no provision to toggle to heating mode, as we generally use natural gas for that. StuRat (talk) 15:19, 29 May 2014 (UTC)

Ahah! Here in Australia, you can buy airconditioners without reverse cycle (as heating mode is termed), but they are quite rare. It costs the manufacturers (in China, mostly) probably only a few tens of cents to put in the solenoid valve to enable reverse cycle, and there is consequently little or no difference in retail price. Reverse cycle airconditioning is the cheapest form, in power consumption, of space heating, although as I showed above, it is not necessarily (and seldom is) the cheapest way to achieve personal comfort. Note that in both heating and cooling modes, an airconditioner is still a heat pump, pumping heat from one place to another. Many houses here use gas for heating, as natural gas is cheaper than electricity, but the aircons still have reverse cycle capability, and will be cheaper to run than gas for space heating purposes. And aircons don't make the house stuffy. For historical reqasons, what Australians call a "heat pump" is a water heater. In other words, a water heater than uses compressor technology to suck heat out of of the ambient air outside the house and us it to heat water for the bathroom. In some States the Government subsidises the purchase of heat pump hot water systems as a means of saving energy (the cost of heating water, a big part of your power bill, will be roughly halved) and being kind to the planet. That's a lot more sensible than subsidising the cost of photovoltaic power generation, as alot of governemnts have done, but which is completely stupid, and doesn't do a thing to save the planet, as they are made with lots of energy generated in (mostly coal-fired) power stations (It's the energy required to make them that makes them so expensive). Floda 58.166.219.242 (talk) 16:03, 29 May 2014 (UTC)

I think passive solar heating makes a lot more sense than solar cells, except in places where you can't get electricity off the grid, where solar cells are actually practical.

As for using an air conditioner in winter to heat the home, window units here are normally removed in winter, as they are poorly insulated. Also, I'd expect the cool portion to frost over, if used in winter, so it seems to me it's more of an issue than just running it in reverse. StuRat (talk) 14:00, 30 May 2014 (UTC)

I've never heard of freezing over being a problem. In most units, when you turn them on during winter, they don't start in the desired room heating mode straightaway. They begin with a "warm-up" phase to ensure the evap is not frozen over - this lasts up to 5 minutes if it's really cold. You may not be aware that this startup phase is happening - it makes the usually noises from teh conpressor and fan anyway. It never gets below about -1 C here anyway, and some aircons don't have this warmup phase, without any problem.

To recycle a well known marketing phrase, just as "oils ain't oils", airconditioners ain't airconditioners. Threa re three main types, relvenat to domestic use: 1) self contained unit Room Airconditioners (often called "window ratlers", 2) split-system room airconditioners, and 3) ducted central-compressor systems. In some houses of a more up-market nature, you sometimes see a 4th type - fan-coil chilled water systems. Clearly, there cannot be any issue with insulation with types 2 thru 4. In fact, the first type has an internal barier between the "inside" part and the "outside" part, and the physical size is such that I find it difficult to accept that there could be any REAL reason, as distinct from a hazy theoretical reason, to remove it for winter. Apart from heat conductedthrough walls, there is always significant heat loss due to what the aircon trade calls "infiltration" - the loss of heat by movement of air through door gaps, imperfect window sealing, ceiling vents, etc. Infiltration heat loss will outweigh any loss through a window rattler. In fact, if you have a house anything like airtight, you may sleep deeply for a somewhat excessive time! Window rattlers are just about obsolete anyway. They are unsightly, and all it takes to prepare a building for installation of a split system is to drill a 30 mm hole at a convenient spot in the wall, and put in a plinth or brackets somewhere for the external unit to sit on. Your comment about insulation is a bit like your suggestion that heat from lighting is lost through windows. That is obviously true in a strict theoretical sense, but in almost all domestic situations, the loss is insignificant. You have a history of making very strange comments about airconditioners, StuRat. Transmissiability of heat and light through glass of the sort used for windows can be approximated by a relatively high value from wavelengths below 4 microns, zero above 5 microns, and a straight line approximation between 4 and 5 microns. By convolution of this function with Plank's Law, a formula for the fraction of heat lost through glass as a function of the light black body temperature is trivially easily obtained. It is of the form Tr = G1 EXP(-G2 EXP(-G3 x T^G4), and for a typically window glass 6 mm thick, the constants are G1 = 0.490, G2 = 106, G2 = 0.280, and G4 = 0.425. Get your calculator out - you'll find the heat loss is tiny.

I agree with you on passive solar heating (sensible building design) though. Just about anything is more sensible than silly solar cells. However only in very remote areas is photovoltaic cost effecive - eg way out in the Australian central deserts. I own a holiday "get away from it all" house in a not so remote area where there is no electrical utility supply. It proved vastly more cost effective to just buy a gasoline powered generator. Mine was made in China (where else?), has excellent sound suppression, and cost only about $600. It has given splendid service without fault for several years now. Solar panels and batteries for the same output (2.5 kw) would have cost at least $200,000 even with the government subsidy. Floda 58.167.245.129 (talk) 16:06, 30 May 2014 (UTC)

"Window rattlers" are common here, and that's what I have. Drilling holes through the walls is not allowed in rental units and drilling through masonry requires special drill bits, in any case. (We did recently have to drill a hole for another purpose, and it was a major ordeal involving cracked bricks.) And what counts as insulation on a window A/C unit is just an accordion-shaped piece of plastic or two. I usually use an excessive amount of tape to seal the air gaps, but that's to keep insects out more than to improve insulation.

And you seem to be guilty of provincialism, thinking however things are done there must be the same way they are done in the rest of the world. StuRat (talk) 16:28, 30 May 2014 (UTC)

Gee, at best, it's a case of Pot calling Kettle Black (see Wikip article on that) there, StuRat! In fact I know that the Chinese and Japanese manufacturers of split systems and ducted system components sell worldwide - even in good old backward USA (their biggest market actually)! And I've drilled lots of holes in brick walls, for plumbing and electrical upgrades, without any such problem. Same with everyone else as far as I can see. What did you use to drill the hole? A screwdriver and a big hammer? Try using a masonry drill next time. Floda 58.167.245.129 (talk) 17:24, 30 May 2014 (UTC)

Zone heating/area heating

Do we have an article ? Are these known under another name ? (They both mean that areas of a building can be heated independently, as with space heaters, to allow more heat where needed and less elsewhere.) StuRat (talk) 18:01, 27 May 2014 (UTC)

See Zone valve and Damper (flow)#Automated zone dampers. Red Act (talk) 21:12, 27 May 2014 (UTC)

Thanks. Those are related, but do we have an article on the exact topic ? StuRat (talk) 03:58, 29 May 2014 (UTC)

Why are fruits classified as living things?

Apples are given the species name of Malus Domestica. But I don't think fruits in general should have species names, because they should not be considered living things in the firs place.. Fruits are ovaries of plants. And an ovary of a human would not be a living thing. So why are fruits classified as living things? Ac05number1 (talk) 07:58, 27 May 2014 (UTC)

That's the name of the tree, not the fruit. The wording in the apple article is admittedly a bit confusing: "The apple is the pomaceous fruit of the apple tree, Malus domestica..." -- BenRG (talk) 08:42, 27 May 2014 (UTC)

..And in any case, you eat fruit and vergetables when they are fresh. That means when they are alive. Plants are not animals. Animal metabolism goes at a fast rate, generating considerable heat. When you cut off blood flow to animal parts, death occurs quickly. But plant material depends on the flow of sap, which is an extremely slow process. Plant metabolism gnerates negligible heat, however the minute oxygen/CO2 exchange of fresh fruit and vegetables can be measured. When you cut off the flow of sap to a plant part, it keeps on living. Floda 124.182.50.125 (talk) 08:47, 27 May 2014 (UTC)

• There are major problems with coming up with a concise, complete, and self-evident definition of "life". Whether something is defined as "living" really depends on how you carefully define your terms, and there's not a lot of agreement on this. Life#Definitions covers some of the multitude of problems with the definitions. Just be aware that even the experts don't have wide agreement on what life is. --Jayron32 17:10, 27 May 2014 (UTC)

Fruits are not ovaries, they are the product of male X female reproduction (pollen and blossoms, to put it simply). Also, it's important to keep in mind that flora and fauna could not care less how humans classify them. They just go on doing their thing as they always have. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:14, 27 May 2014 (UTC)

Um, you're going to have to inform every botanist and plant scientist in the world that fruit are not ovaries. From the Wikipedia article titled fruit, in the opening sentence,: "In botany, a fruit is a part of a flowering plant that derives from specific tissues of the flower, one or more ovaries, and in some cases accessory tissues" (bold mine) and later in the same article, the "Fruit development" describes, in some detail, the changes that occur in the ovary as it develops into the fruit. --Jayron32 21:10, 27 May 2014 (UTC)

The OP compared this type of "ovary" with a human ovary. From what you're saying, that is not a valid comparison. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:47, 27 May 2014 (UTC)

You said "Fruits are not ovaries." But they are. If you didn't mean that, you shouldn't have said that. --Jayron32 01:36, 28 May 2014 (UTC)

Yes, you're right, as per Ovary (botany). So when the OP said, "Fruits are ovaries of plants. And an ovary of a human would not be a living thing," he was almost literally mixing apples and oranges. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:25, 28 May 2014 (UTC)

So, you've established that humans are not plants. I'm pretty sure we all figured that out already. --Jayron32 02:41, 28 May 2014 (UTC)

Are you sure the OP has figured that out already? ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:05, 28 May 2014 (UTC)

So, eating an apple in a random place - say Paradise - would be oral sex? --Cookatoo.ergo.ZooM (talk) 21:23, 27 May 2014 (UTC)

This is the classic "Chicken and Egg" thing. Is an egg a living thing that is produced by a chicken - or is the egg a non-living thing that produces a chicken? Most fruit can be simply dropped onto fertile soil where they gradually turn into a full-blown growing plant. In a sense, an apple is just a baby apple-tree - in the same way that an egg is a baby chicken. You can alternatively say that the body of the apple is a mere container for the seeds inside...a "womb" - but it's a very grey area. Fruit often comes down to being a food supply or a protective shield for the seed inside - but denying that the fruit is a living thing is like denying that your own skin is "alive" (although, by some definitions, some of your skin layers are in fact "dead").

In cases like this, I'm with my personal hero, Richard Feynman - who frequently went to some pains to point out where an ill-defined word is a poor substitute for an understanding of the things it purports to describe. Really, it doesn't matter a damn whether a fruit is considered to be alive or not. "Alive" is just a word - a convenient short-hand representation of a much more complex concept. Arguing what the word means tells you nothing whatever about the nature of an apple. The apple carries the seed from parent tree to provide an environment for the child plant to grow. Whether it's "alive" or not is a trivial matter of linguistics. The science desk shouldn't even be involved here! This is a language matter! SteveBaker (talk) 15:33, 28 May 2014 (UTC)

Interesting take on the definition of life in this article. Count Iblis (talk) 16:43, 28 May 2014 (UTC)

If I could understand it...yes! It kinda sounds like almost any computer would be considered as "life" under that definition...but like I said, it's really hard to read.

But, again, we're fighting to define a word - we're not learning anything by nailing down the definition. A definition that said "Anything blue is alive" would have about as much value as all that babble about dynamic systems and so forth. "Life", "intelligence", "species" and even "planet" are all examples of words that people have long argued the definition of - but reality continues to toss up borderline case and things that force the definition to include things you don't want included - or exclude that which seems it should not. We had a really good discussion of this topic HERE a few years ago. Finding a definition for "life" is easy - but finding one that doesn't conflict with our emotional "I know it when I see it" thing seems to be impossible. Nobody likes when things that they don't agree with on a gut level get built into a definition. Note the upset when Pluto failed to qualify under the formal definition of what a "Planet" is. We have the same problems with things like viruses and intelligent computers. SteveBaker (talk) 19:58, 28 May 2014 (UTC)

Pluto didn't change, only somebody's definition changed. Unfortunately, the original meaning of "planet" was kind of lost in that debate. As regards fruits, etc., in the seed industry the product is considered to be a living organism. Granted, it doesn't "do" anything as-is. Soil and water cause it to "awaken", i.e. to germinate. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:37, 28 May 2014 (UTC)

That "babble about dynamic systems" is the fundamental point here and you do learn something from that, basically that this is has a lot more to do with physics than with biology. The problem really is about the macroscopic dynamics of a system, to what degree a description in terms of only macroscopic variables is going to correctly describe its macroscopic dynamics. I think Medeis has made the point here some time ago that you can't consider a lion as a collection of molecules. While I disageeed on some points here, I think this is how you can define life. You need to formalize what it means to have emergence of phenomena at a higher level such that a lower level description, while accurate, is no longer useful. Count Iblis (talk) 22:09, 28 May 2014 (UTC)

Masturbation/ejaculation and hormone levels.

Does masturbation or ejaculation increase hormone levels in men? Thanks in advance. --Thomas W. Richardson (talk) 19:15, 27 May 2014 (UTC)

Yes, in particular the hormones oxytocin and prolactin, according to the Orgasm article. Red Act (talk) 19:37, 27 May 2014 (UTC)

I imagine any effect on androgen production would be more pertinent to the intention behind the OP's question. Evan ^{(talk|contribs)} 01:46, 28 May 2014 (UTC)

There is a myth that you shouldn't exercise after orgasm because testosterone levels drop, but there doesn't seem to be any scientific evidence for this (and in fact there's some to the contrary). I wish I could find a more reliable source, but this page is the most relevant one I can find tackling the myths. --— Rhododendrites ^talk |  03:10, 29 May 2014 (UTC)

I haven't looked at what they say in detail but it seems to be on a mission so I would be careful about what they say. It probably isn't too strong bias but places like that tend to have only references that back what they say. Dmcq (talk) 11:51, 29 May 2014 (UTC)

Indeed. I did see that, but it seems like there are a whole lot of sites backing it up -- that was just the one tackling the myths directly. Nonetheless, I struck my last answer because there are just too many variables for me to feel comfortable responding as such (length of time without sex, hormone levels at different lengths of time afterwards, long-term vs. short-term, kinds of hormones, frequency of orgasm....). I think the only solution is to find the research papers themselves... --— Rhododendrites ^talk |  16:03, 29 May 2014 (UTC)

May 28

X:A ratio

The X:A ratio articles defines the X:A ratio as the ratio "between the X chromosome and the number of sets of autosomes in an organism."

But an X chromosome is not a number. Does the article mean "number of X chromosomes"? But an organism has either one or two X chromosomes... 65.92.7.8 (talk) 01:45, 28 May 2014 (UTC)

Fruit flies can have three... 24.5.122.13 (talk) 02:02, 28 May 2014 (UTC)

Yes, the article means "...number of...", so I just now clarified the article. And although it's uncommon, humans can also have more than two X chromosomes; see Aneuploidy#Types. Red Act (talk) 02:20, 28 May 2014 (UTC)

Okay, thanks. 65.92.7.8 (talk) 03:06, 28 May 2014 (UTC)

Radiation exposure

How do I go from roentgens to Sieverts? Thanks in advance! 24.5.122.13 (talk) 07:34, 28 May 2014 (UTC)

One sievert equals 100 rem. per the Sieverts article you linked. it also states it here. Richard-of-Earth (talk) 08:44, 28 May 2014 (UTC)

Note that one roentgen (R) is not the same thing as one rem. In practice, they're often fairly close for x-rays, but typically 1 R of x-rays is a bit less than 1 rem of equivalent dose. Roentgens are a measure of ionization in air whereas the rem or the sievert are (different) measures of equivalent or effective dose in a biological system. TenOfAllTrades(talk) 11:36, 28 May 2014 (UTC)

So how do I convert from roentgens to rems? 24.5.122.13 (talk) 23:15, 28 May 2014 (UTC)

To go from roentgen to gray you use F-factor (conversion factor) and to go from gray to sievert (rem) you use Radiation weighting factor (Q factor). Maybe Absorbed dose is worth reading. Thincat (talk) 11:16, 29 May 2014 (UTC)

Thanks! 24.5.122.13 (talk) 20:10, 29 May 2014 (UTC)

Down's Syndrome and obesity

Do we know why Down's causes obesity ? See Down_syndrome#Physical, if you don't believe that it does. I suppose one possibility is that it's merely mental. That is, while normal intelligence individuals know what they must do to maintain a low weight (eat right and exercise), Down's patients do not. Perhaps Down's patients are also less motivated to do so. Are these the only reasons, or is there a physical cause ? (I know that Down's patients tend to be shorter, but that doesn't automatically bring obesity with it.) StuRat (talk) 11:43, 28 May 2014 (UTC)

I found Obesity in Children with Down Syndrome: Background and Recommendations for Management which says: "Although specific associated problems of Down syndrome, both physiological and behavioral, foster the development of obesity..." (on the second page). Alansplodge (talk) 12:40, 28 May 2014 (UTC)

"Down's patients"? That is an insulting and thoughtless phrase. I have no idea how you treat people who have Down's syndrome in the USA but here in the UK they are individuals mostly integrated into the community and not regarded as 'patients' by anyone. The idea that if you know you must eat less and exercise to stay slim is well known by most obese people but they still don't. Richard Avery (talk) 06:32, 29 May 2014 (UTC)

I have no idea what your on about now. Down's Syndrome is a medical condition, therefore anyone with a medical condition can be accurately called a patient. Not even sure what term you would use instead.

And obviously Down's Syndrome is not the sole cause of obesity, so that comment is rather useless, too. StuRat (talk) 15:09, 29 May 2014 (UTC)

(Shakes head sadly) Richard Avery (talk) 08:01, 30 May 2014 (UTC)

A patient is any recipient of health care services. Down syndrome patients are afflicted by a genetic disorder that is incurable. Ongoing improvements in health care has increased their life expectancy from 12 years in 1912 to 50-60 years in the 2000s. Charity and advocacy organisations exist for Down's patients in the UK and in the US that you may contact if you really wish to help. Down's patients are not helped by admonitions about PC wordage. That seems to be what you're (not "your") headshaking about. 84.209.89.214 (talk) 19:38, 30 May 2014 (UTC)

Why were the stellar nursery clouds spinning in the first place?

My understanding is that stellar systems of stars (at least the current "generation") with planets orbiting them started out as clouds of dust ("dust" being a catch-all word for the matter that came from dying stars) which eventually collected due to gravitational forces until the internal forces of the accreted blob were enough to cause fusion to start, and of the matter that spewed out after the sun "started", planets accreted. Of course this is a very simplified summary by me. My question is what causes those initial clouds and subsequently accretions destined to be stars to be rotating in the first place? 75.75.42.89 (talk) 18:04, 28 May 2014 (UTC)

A very small initial rotation turns into a much greater rotational speed, as the cloud collapses, due to conservation of angular momentum, just as an ice skater spins faster as she brings her arms in. As for the source of that initial rotation, there's the rotation of the galaxy, and that in turn came from the gravitational interaction with nearby galaxies, I suppose, as they were forming. How any rotation at all started comes down to the problem of why matter was unevenly distributed initially in the universe, and had different relative velocities. To that, we have no answer. StuRat (talk) 18:10, 28 May 2014 (UTC)

"To that, we have no answer" In fact we do. During the first extremely small fraction of the second after the Big Bang the world was so small that quantum fluctuations affected this super fluid (my term, sorry). Those quantum fluctuations which may be observed now in some artificial conditions led to unequal matter density in the early universe and subsequently resulted in gravitational galaxies formation. --AboutFace 22 (talk) 21:18, 28 May 2014 (UTC)

And what causes the quantum fluctuations ? StuRat (talk) 03:57, 29 May 2014 (UTC)

Quantum fluctuations are an intrinsic part of the universe (according to modern quantum field theory), and are essentially a direct consequence of the uncertainty principle. The underlying physical processes are believed to depend upon probabilistic effects and hence have an intrinsic degree of randomness. These effects are generally negligible on the macroscopic scale, but are important on very small scales. However, inflation made small things very large very quickly and carried and imprint of the quantum fluctuations with it. Dragons flight (talk) 04:35, 29 May 2014 (UTC)

Why would the nursery clouds not be spinning in the first place? Zero is just another number, and any little nudge from a nearby supernova would make a non-rotating system rotate. --Bowlhover (talk) 05:16, 29 May 2014 (UTC)

Under Occam's Razor, zero is simpler. For example, having zero whales in you back yard is a lot more logical than any other number. StuRat (talk) 14:53, 29 May 2014 (UTC)

You're missing the point. In space, a spinning object will continue to spin due to lack of friction. Any little nudge from supernovae, gravitational interactions, collisions, radiation pressure, and the like will make an object spin. In order for an object to not be spinning, the millions of torques that it has ever encountered must EXACTLY cancel out. That is virtually impossible in a complicated universe. --Bowlhover (talk) 16:44, 29 May 2014 (UTC)

Once we assume there was a non-uniform distribution of matter in the initial universe, then yes, spinning is a natural result of that. It's that non-uniform distribution which is the oddity. StuRat (talk) 13:50, 30 May 2014 (UTC)

Bowlhover has a good point. The chance of throwing a dart at a real number line and hitting zero is zero. Assuming zero is most certainly not simpler than assuming non-zero. SemanticMantis (talk) 15:24, 29 May 2014 (UTC)

One galaxy might have rotational momentum or energy in one direction that is balanced by that of others, such that over a large enough scale (or over the universe) it sums to zero. Edison (talk) 20:11, 29 May 2014 (UTC)

The thing is that if the universe started from a literal singularity (a point of zero size) then from an argument of symmetry, then in 'classical' physics, everything that follows should produce a universe that's perfectly uniform in every direction...and there could be no rotation whatever because that would be an asymmetrical thing - and no initial source of asymmetry is possible.

We really need some random quantum-type effects to break up the perfect symmetry and allow the statistics of that randomness to generate asymmetry. Once you have a breaking of that perfect uniformity - however tiny - then chaos theory can produce all manner of complicated motion and clumping.

SteveBaker (talk) 15:58, 30 May 2014 (UTC)

Whatever the sources may be of initial non-uniformity, energy and angular momentum in a hypothetical initial universe they manifested in a F.O.P. once-only event. A bell cannot be un-rung; every event that follows, including you reading this, is F.O.P. uniquely predetermined by that primordial event. I suggest that the Predeterminism implicit in the prevailing Big Bang cosmological model is inseparable F.O.P. from conscious or unconscious dependence on a metaphysical causation, while less dogmatic steady-state and Multiverse world views provide more fertile scopes for human intellectual development and expression. F.O.P. = from our perspective. 84.209.89.214 (talk) 18:39, 30 May 2014 (UTC)

Native aluminum

There is an old story from Pliny's Historia Naturalis about what some sources suggest was an aluminum goblet given to Tiberius: "One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had made the metal from plain clay. He also assured the Emperor that only he, himself, and the Gods knew how to produce this metal from clay. The Emperor became very interested, and as a financial expert he was also a little concerned. The Emperor felt immediately, however, that all his treasures of gold and silver would decline in value if people started to produce this bright metal of clay. Therefore, instead of giving the goldsmith the regard expected, he ordered him to be beheaded." ^[1]

However, a recent translation I searched tells this a very different way: "There is a story that in the reign of Tiberius there was invented a method of blending glass so as to render it flexible. The artist's workshop was completely destroyed for fear that the value of metals such as copper, silver and gold would otherwise be lowered. Such is the story, which, however, has for a long period been current through frequent repetition rather than authentic."^[2] A forum I stumbled across cites some similar glass-based variants of the story.^[3]

Now I can't account for the differences in translation, which is something more worth asking at Humanities, but the preceding forum provided another interesting reference to native aluminum in the "Nanjing Belt".^[4] Apparently an ancient belt was found to contain twenty pieces of metal, including four that turned out to be aluminum; it doesn't sound like fraud is clearly ruled out but it wasn't proven either.

More interesting is that not only is there this artifact, but actual native aluminum has been reported to have been found in China. We cover this a bit at Aluminium, but to add some other references, a tungsten-gold deposit in Lianhuashan^[5] and volcanic rocks, hydrothermal deposits, and in ocean sediments in tectonically active areas.^[6] (our article mentions cold seeps) Apparently though some identifications have been in error, due to aluminum wrappings for explosives in mining?^[7] According to [8], " there are three models of the formation of native aluminium, such as carbon deoxidization in the high temperature environment, endogenous processes of high hydrothermal activity in the submarine hydrothermal fluids, element replacement amond Al,S,K,Na." However, our article on aluminum mentions another, the biological reduction of Al(OH)4-.

Now to put together a highly speculative model, I would suppose it should be possible for some people, perhaps in Guangdong, to find some placer deposits with aluminum grains and try smelting or glassmaking from them at high temperatures (higher than known to be used at that period, it would seem) and end up with small amounts of apparently precious metal. Seeking a wealthy novelty market, these could have been traded far and wide, to the Wu capital in Nanjing and even down the Silk Road to the Romans. Tiberius' reaction might be accounted for not as a matter of suppressing technology, but because practically any piece of aluminum coming out of the Silk Road would have been traded hand to hand, gradually rising up the Roman hierarchy until it came to him... putting the "inventor" in a bad spot when his piece wasn't the first. (Either that or he turned it over and spotted the "Made In China" on the back :) The industry might have plausibly collapsed and the technology forgotten once the best known deposits were worked out, since without a clear scientific appreciation of the elements as Napoleon III had, its value might have been limited to something near the value of silver no matter how expensive heating mountains of sediment became.

Anyway, my question here is: can people recommend some more data to suggest that native aluminum was available to Chinese from 100BC-300AD, that they were capable of working it, that other aluminum artifacts than these two fringey cases exist? I realize that right now this is still at about a "paranormal" level of evidence, and yet... how often have the ancients ever turned out to have been less than what we expected? Wnt (talk) 19:22, 28 May 2014 (UTC)

The credibility of this report of an ancient aluminium gear piece in Russia is not helped by using a photograph twice as mirror images. A link fallen from a watch strap perhaps? 84.209.89.214 (talk) 20:00, 28 May 2014 (UTC)

Aluminum is highly susceptible to oxidation by air, so any significant deposits of native aluminum are highly unlikely -- it would oxidize as fast as it forms. The version with the glass is more likely -- this could have been done simply by adding borax (which was readily available in the Roman Empire) to the molten glass to make essentially a variety of Pyrex glass. 24.5.122.13 (talk) 23:24, 28 May 2014 (UTC)

To be clear, our article on aluminum does currently credit reports of native aluminum granules. Gears, of course, are another story (I expect something interesting but not that interesting involving explosives or drilling). Wnt (talk) 02:08, 29 May 2014 (UTC)

What the typical man's and woman's voices sound like. Disagree?

Sometimes, there are people who say a particular person doesn't sound like the typical man/woman when he/she talks. But we need to know what is considered the typical man's/woman's voice.

I believe the voice of Douglas Rain (the narrator heard in the video below) is what's considered the typical man's voice:

http://www.youtube.com/watch?app=des...&v=pkx86BbAvsM

I believe the voice of Majel Barrett (yes, the dark haired woman in the video below) is what's considered the typical woman's voice:

http://www.youtube.com/watch?v=YuodlFsfosA

To make it simple: The typical man sounds like Douglas Rain. The typical woman sounds like Majel Barrett.

Anyone disagree with this? Stoned stoner (talk) 21:31, 28 May 2014 (UTC)

What's your basis for this assumption? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:33, 28 May 2014 (UTC)

Well, people largely associate female computer voices with Majel Barret and male computer voices with Douglas Rain. Stoned stoner (talk) 21:42, 28 May 2014 (UTC)

Who says that? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 29 May 2014 (UTC)

A google search shows that when people bring up examples of male and female computer voices, it is HAL (the computer voiced by Douglas Rain in 2001: A Space Odyssey (1968)), and the the starship Enterprise's computer (voiced by Majel Barrett) in Star Trek (1966-1969), that are most frequently given examples. — Preceding unsigned comment added by Stoned stoner (talk • contribs) 00:33, 29 May 2014 (UTC)

They probably bring up HAL because it's familiar. You didn't initially ask about computer voices, just voices in general. I always thought HAL sounded too breathy for a normal male voice. A typical male TV newscaster would work better. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:20, 29 May 2014 (UTC)

The Ref. Desk should not be used to convass opinions. Boys and girls have roughly similar vocal pitch, but during puberty the male voice typically undergoes a downward Voice change (see article). Voice therapy (trans)#Differences between male and female voices analyses their pitches and resonances. This study explains the differing ways the brain interprets male and female voices. 84.209.89.214 (talk) 00:30, 29 May 2014 (UTC)

Yes, a statement followed by "anyone disagree?" isn't a great way to approach us. If you'd like a reference on vocal typicality, I suggest this freely-accessible article titled "Vocal Attractiveness Increases by Averaging" [9]. It even has examples of averaged voices, you can ask at WP:REX if you're having trouble getting access. They might even sound to you like your examples. The point is, averaging voices is a scientific notion of typicality that has been studied. You might also be interested in the analogous research on averaged faces, some of which is summarized here: [[10]]. Perhaps someone has done research where participants are asked to rank vocal samples in terms of typicality, you might be able to dig something like that up on google scholar. ( As for your claim: it's ill-defined and poorly scoped, to the extent that I can't even disagree  ;) SemanticMantis (talk) 02:23, 29 May 2014 (UTC)

"Vocal Attractiveness Increases by Averaging" was an interesting read. Thanks, Mantis, for the link. It left me wondering, however, whether "vocal attractiveness" would be judged differently by people of different cultures (I imagine it would). The article didn't mention in the methodology section if the "listeners" represented a cross section of world cultures or if they were all from Western cultures. I once heard a Southeast Asian man praising the voice of a particular Thai actress as "beautiful" and "most pleasing", but to me her voice sounded so high pitched and nasal as to be almost annoying. "Typical" men's and women's voices and their level of perceived attractiveness probably varies significantly by culture. Odd that I can't find, through an admittedly hasty search, any papers on that aspect of the topic.--William Thweatt ^TalkContribs 03:38, 29 May 2014 (UTC)

This whole situation sounds somewhat comparable to the Theory of Forms, the Platonic concept of ideals. Probably everyone has an idea of what the typical man or woman sounds like, and probably everyone's idea is slightly different from everyone else's; this isn't something that can be quantified or measured. Nyttend (talk) 04:03, 29 May 2014 (UTC)

I beg to differ. Stoned stoner (talk) 05:01, 29 May 2014 (UTC)

You have my permission: go ahead and differ. —Tamfang (talk) 16:45, 29 May 2014 (UTC)

Agreed that there will likely be cultural norms that influence how voices are perceived. My impression was that e.g. Anglophone listeners would rank averaged native-Anglophone voices as more attractive than "raw" single native Anglophone voices, and likewise for other groups listening to averages of people within their groups, be they political, ethnic, linguistic, etc. I also disagree with Nyttend that this cannot be quantified or measured. I do agree that it is difficult to study these ideas with rigorous methods and get repeatable results. Social psychology and sociolinguistics deal with this kind of vagueness all the time. That the study is difficult is no reason not to engage! SemanticMantis (talk) 15:20, 29 May 2014 (UTC)

Any question worded like "Do you agree?" could be answered with a simple "Yes" or "No". ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:18, 30 May 2014 (UTC)

@Baseball Bugs: (off-topic but I think this is interesting stuff) I think that's only true for well-defined, clear claims of fact. E.g. "All swans are white -- do you agree?" I can't in good faith agree or disagree with the OP's claim. See e.g. not even wrong for the idea I'm going for. Also perhaps loaded question. For example "Bill has stopped beating his wife -- do you agree?" Whether you answer "yes" or "no", it implies wife beating occurred in the past, and a simple yes/no answer will not suffice, if we want to be fair to Bill. SemanticMantis (talk) 15:25, 30 May 2014 (UTC)

Ah, good point. Hence the need for a third possible response: "No opinion". As you and others have indicated, there could be studies or surveys on the subject - but even that still really comes down to individual opinions. My GPS has some type of computerized male voice that sounds exactly like the computerized male voice on NOAA weather radio, and would never be mistaken for the voice of HAL, but somebody somewhere decided that that sounds like a proper male voice, at least for those applications. As to a woman's voice, I'd have to say that the female voice they use on NOAA is kind of similar to Majel Barrett's computer voice, except they've added inflection to the voice so it sounds more "normal" than the Star Trek computer's deliberately monotonic voice (which sounds very dated by today's standards). The recorded female voice you often hear on telephone answering systems often seems to be the same woman (which it might well be) - and I'm pretty sure it's not Majel Barrett. In fact, it's more like a female version of HAL's soft but clear enunciation. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:57, 30 May 2014 (UTC)

May 29

Cats drinking

Why can't cats drink "normally", e.g. slurping or sucking liquids as we do? Is it perhaps the mouth shape? I found this through Google (it's interesting, but doesn't explain the "why"), and it was the least un-useful thing I could find. Nyttend (talk) 04:00, 29 May 2014 (UTC)

Could it be because they don't have lips? 217.158.236.14 (talk) 08:17, 29 May 2014 (UTC)

Cats CAN suck. I've never seen one that couldn't. Granted they tend to stop doing it once they are weaned but I have seen adult cats suck on a bottle with a teat. As to why they don't suck up water out of a bowl is a mystery to me. 196.214.78.114 (talk) 09:22, 29 May 2014 (UTC)

Perhaps drinking "normally" is simply the more efforted method? Plasmic Physics (talk) 11:03, 29 May 2014 (UTC)

Humans drink by sucking, as their relatively flat facial shape and use of hands to hold the drinking vessel (or use hands as a drinking vessel, as do monkeys) allows the nose to be kept out of the water, and sucking is pretty efficient. Snouted animals such as cats and dogs drink by putting heir heads down to reach the water. This means that if they put their mouths far enough into the water to allow sucking, their nostrils will be submerged. Water up the nose isn't nice. Other snouted animals such as lizards drink the same way for the same reason. Floda 58.166.219.242 (talk) 11:54, 29 May 2014 (UTC)

I think human hands have a lot to do with it. We can hold a drinking vessel or make a cup out of our hands, held together to get water from a stream. Without doing either of these, sticking our faces down into the water is possible, but any waves would likely splash our faces/go up our noses. It's also a rather vulnerable position to be in, if there might be an alligator/crocodile in the water. StuRat (talk) 15:03, 29 May 2014 (UTC)

Bovids, (cattle, sheep, goats, antelopes) all drink by sucking, and they have snouts. It is of course not difficult to suck liquid while the nostrils are submerged, it means holding your breath briefly. Richard Avery (talk) 08:09, 30 May 2014 (UTC)

Do those animals also have muscular control over their snouts, i.e. the ability to close them? Humans generally don't, but we're built somewhat differently from bovines. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:16, 30 May 2014 (UTC)

Cats have rough tongues, supposedly an adaptation that allows them to clean all the meat off a bone. It supposedly also acts like a little collection of "cups" so that slurping liquids is pretty efficient. And of course, as noted above, and like most any mammal, as newborns they suck milk from their mother, hence the term "suckling". ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:14, 30 May 2014 (UTC)

"Why" is usually a tough question for science. A cat's tongue is very rough, not only for removing meat from bones, but also for keeping themselves clean and groomed. However they "choose" to drink, their tongues would remain the same, so this evolutionary "choice" costs them little or nothing; there's no structure being built that wasn't already in use. Matt Deres (talk) 15:07, 30 May 2014 (UTC)

I am highly dubious about some of the previous responses here...too many rash assumptions are being made.

I'm not 100% convinced that all baby mammals are actually sucking when they feed from their mother's milk. Here are my reasons for being doubtful:

1. (Warning: original reasearch ahead!) When we just got our newly weaned puppy a couple of weeks ago, he liked to sit on my lap and "suck" on my finger...presumably it reminded the little guy of his mommy. It was pretty clear to me that he wasn't creating a seal with his lips and inhaling (as we'd do when we suck) - but rather just doing licking motions with his tongue from inside his mouth - repeatedly pressing my finger against the roof of his mouth.
2. When you think about how you manually milk a cow (by squeezing the teats from the base to the tip) - you're presumably mimicking what the baby calf would do. You could easily imagine that the animal is squeezing the milk out by pressing it's tongue upwards. That licking motion is not all that different from lapping up water from a dish.
3. This idea is kinda confirmed by our Milking machines information - which says that these machines (which do work by creating a pulsating suction) "work in a way that is different from hand milking or calf suckling"...implying that at least calves don't just apply suction.
4. Human babies also do quite a bit of tongue movement - although they most definitely *do* form a tight seal and suck.
5. In evolutionary terms, early mammals produced their milk as droplets oozed out through the skin that was licked up by the offspring. Demonstration of that fact is that the modern Platypus has mammary glands but no teats. Milk oozes out of pores in the skin and pools in grooves on her abdomen where her babies lap it up, just like a cat laps up water from a dish.

So it's clear that in evolutionary terms, lapping is a much older behavior than sucking - and it seems fairly likely that many modern mammals still produce milk from their mothers by using a lapping-like motion with the tongue against the teat rather than sucking.

I'm not saying that this is a definitive conclusion - only that we shouldn't jump to the conclusion that kittens can suck just because they are mammals...and even if they do indeed suck their milk - you can easily see that the older (in evolutionary terms) instinct to lick milk from mother's skin can easily provide the instinct needed for young animals to lap up water instead of sucking it.

SteveBaker (talk) 15:48, 30 May 2014 (UTC)

Yes, a dog's mouth is long, so there's more lip area that needs to be sealed to create a suction. A circular mouth opening is ideal for creating a good seal on a circular teat, and we humans are pretty close to that. StuRat (talk) 16:01, 30 May 2014 (UTC)

How do doves and pigeons make their vocalizations?

I have researched but found little to no information. i'm baffled at how they make their "cooing" sound. --Coo coo pigeon (talk) 05:22, 29 May 2014 (UTC)

Maybe doves coo (I have no idea what doves sound like) but I've never heard a pigeon say "coo". Have you? Cats literally say meow. Chickens really make pocks. It's not like the two things pigeons say are hard to spell or look un-English (like turkey & pig). Sagittarian Milky Way (talk) 11:02, 29 May 2014 (UTC)

Feral/rock pigeons definitely 'coo'. I think that it's predominantly a mating call from the males. Their throats seem to expand when they do it (don't think that it's just the feathers), so maybe there's some sort of echo chamber in there? collared doves definitely also coo. --Kurt Shaped Box (talk) 11:52, 29 May 2014 (UTC)

Feral pigeons say "Croo! Croo! Croo! Croo! Croo! Croo!" A thing fatter pigeons say is "Crook-Croo!, Crook-Croo!" until the bullied smaller pigeon goes far enough away to the bigger pigeon's satisfaction. He or she (both do it) puffs it's feathers up to look bigger and alternate body rotations and short charges with pauses while gobbling the magic words. While moving, they spread the tail like a fan and bend it's feathers to the ground to make a scraping sound. They stop before hitting the chasee, though. Especially bold pigeons sometimes try to make thinner birds afraid of being landed on, and I've seen a thug pigeon or two land on it's smaller competitor, but not with full force. I think they do that (the landing) when they get fed up that he/she keeps running in circles back to the good area with uneaten seeds. Sagittarian Milky Way (talk) 13:16, 29 May 2014 (UTC)

Bird vocalization is produced with an organ called the syrinx. Richerman (talk) 14:55, 29 May 2014 (UTC)

Richerman, Doves and Pigeons have no vocal cords. Zero. Zip. None. and i can't imagine that the Syrinx would synthesize a sound like that. Other birds create a "twittering" sound or melodious songs. --Coo coo pigeon (talk) 17:18, 29 May 2014 (UTC)

Who said they do have vocal chords? As it says in the the Syrinx (bird anatomy) article (the right link this time) "Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals". Have you ever seen or heard organ pipes? The small ones produce high pitched notes and the large ones deep sonorous notes. And if you want to know how the syrinx works in a pigeon there is a rather technical explanation here, summarised here. It would help if you did a bit if research before rubbishing others' contributions. Richerman (talk) 18:20, 29 May 2014 (UTC)

Speaking for birds in general, the syrinx can produce sounds just as effectively as our larynx. Surely you must have encountered a talking bird before? Also, not all birds twitter or sing. Some can make incredibly loud and harsh calls - far more powerful than you'd expect for a creature of that size. --Kurt Shaped Box (talk) 22:11, 29 May 2014 (UTC)

Sometime I mimic the coo rather well with a very open mouth(low pitch) whistle. Maybe its some type of whistle mechanism.165.212.189.187 (talk) 17:24, 29 May 2014 (UTC)

Binary problems with Kepler 64

Hello all!

I'm doing some fiddling with a quite awesome star system: Kepler 64. I'm having serious trouble visualising the system (I may have to go and buy some marbles) especially when it comes to the two sets of binary stars that are involved. I've thrown out the planet that exists (sorry) and I'm making a new multi-planet system to go in there instead, but I'm having trouble with envisioning how their four suns (or two suns and two Venus-bright things) rotate around each other, at what duration and at what distance.

For the centre pair, they are known to orbit each other in 20 days. That's good. I cannot find anywhere how far apart they are (a diagram I found here (astro.twam.info/hz-ptype/) suggests 0.3 AU?) but specifically how that will look from the planets - say there's one in the habitable zone at 2.5 AU, how far would the red star ever get from the white star? The width of a full moon at most, or further, or less?

For the outer pair, they're 1,000 AU away and have a separation of 60 AU. Yay for hard numbers! But what would this look like down on the planet? Two Venuses a handspan apart? Would I be able to make up how long it takes them to rotate (I'd like it longer than the centre's 20 days) or is there a set speed? I can't work it out; I never learned how to calculate this stuff and I don't know where to start. I tried using a Kepler's Third Law online calculator to work out how long it would take these two to orbit the centre pair, and the result I got was just under 26,000 years; I've no idea if I'm barking up the wrong tree.

Whilst I may be doing creative stuff and it is tempting to wing it completely, I would rather get this right or as close to right-ish/plausible as possible. Otherwise it will bug me. So thank you in advance for your help in indulging one's mad hobbies!

Lady BlahDeBlah 09:38, 29 May 2014 (UTC)

See Kepler's laws of planetary motion#Third law: for a circular orbit the radius r, period T, and mass M are related by T²/r³ = 4π²/GM where G is the gravitational constant. Here M is the total mass of both orbiting bodies, but sometimes (as with the Earth and Sun) we can ignore the smaller one. Now a trick: use AU as the unit for radius, year as the unit for period, and solar mass (mass of our sun) as the unit for mass. So for the Earth orbiting the sun, we have T = r = M = 1 and therefore we know that G, expressed in these units, has the value 4π²; so we can reduce the formula to just MT² = r³.

Now the SpaceRef article linked as a reference from Kepler 64 gives the masses of the two close stars as 1.528 and 0.408 solar masses. So if T = 20 days = 20/365 years, we have r³ = (1.528+0.408)×(20/365)² = .0058, giving r = 0.18 AU or a separation of 2r = 0.36 AU.

But this is assuming a circular orbit. If the orbit is eccentric, that's the maximum separation but some of the time they will be closer. So if you're looking at the stars from a planet orbiting them, how far you see them separate will depend on where in your planet's orbit you are in relation to the aphelion (apocenter, whatever) position of the two stars.

Anyway, from a distance of 2.5 AU, a separation of 0.36 AU would appear as an angle of approximately arctan(.36/2.5) [more precisely 2 arctan((.36/2)/2.5)] or about 8° — about like the width of the bottom of the bowl of the Big Dipper, I believe. --69.158.92.137 (talk) 10:44, 29 May 2014 (UTC)

The r = 0.18 AU that you calculated is the separation between the 2 stars (not half the separation). Kepler's laws for a large mass and a small mass (limiting case of small mass becoming 0) can be derived quite easily for a circular orbit using Newtonian gravity. If the smaller mass is not so small, there are 2 common ways of treating the problem:

(A) Take the separation between the 2 objects as your radial coordinate. It then turns out that the same laws apply for the relative distance, but with the sum of masses $M+m$ in place of the larger mass $M$.

(B) Take the distance between the lower-mass object and the center of mass of the 2 objects as the radial coordinate. It then turns out that the same laws apply for that distance, but with ${\frac {M^{3}}{(M+m)^{2}}}$ in place of the larger mass (or equivalently, for the distance of the higher-mass object from the center of mass, the same laws apply for ${\frac {m^{3}}{(M+m)^{2}}}$ in place of the larger mass).

Icek (talk) 07:10, 30 May 2014 (UTC)

And if the orbit is not circular, the separation will sometimes be larger and sometimes smaller, but always smaller than twice the separation for a circular orbit (so always smaller than about 0.36 AU in our example); in other words, what you calculated as 0.18 AU is the semimajor axis of the ellipse. Icek (talk) 07:16, 30 May 2014 (UTC)

Thanks all muchly! Despite not having any formal tutelage on this subject I think you're helping me begin to vaguely understand the maths behind it all (now watch as my made-up solar system fails science spectacularly) I am going to keep eccentricity in mind but for simplicity's sake I might just apply it to the planets. I am still having trouble with plugging in the numbers I need for the outer binary pair into the equations the IP gave above, in an attempt to get their perceived separation - I think I get lost somewhere in trying to work out the degrees...I think I can manage the planets a little easier without having to bug any mathy people further, but it's just one binary pair that's still mucking things up... >.< The outer pair have a defined separation of 60 AU and solar masses of 0.99 and 0.51 solar masses, and a distance of 1000 AU...could I be cheeky enough to ask for one more sum to get me past where I get stuck? Lady BlahDeBlah 09:05, 30 May 2014 (UTC)

For the movement of the "outer" 2 stars around their common center of gravity, use the same formula, i.e.

t(years) = sqrt( (separation(AU))³ / (sum of their masses in solar masses) )

For the movement of the pairs around each other, use the same formula, but with the sum of all the masses involved (i.e. we approximate the situation as if the Aa and Ab stars would be one single object and the Ba and Bb stars would be another single object).

Note on the accuracy: The 1000 AU separation has a quite large uncertainty... because without observing the orbital motion (and for that we need either enough observation time for them to have completed a substantial fraction of their orbit or very accurate measurements of their apparent movement or radial velocity), all we have is the apparent angular separation of the 2 pairs and a distance measurement which translates the apparent angular separation to a projected separation; we do not have information how much the separation is along the line of sight (distance measurements aren't that accurate).

Icek (talk) 09:49, 30 May 2014 (UTC)

If 1000AU, they would be bright as a crescent and gibbous moon compressed into a point. Sagittarian Milky Way (talk) 17:12, 30 May 2014 (UTC)

Beyond cementite

At what carbon content does the iron-carbon system change from a cementite and carbon, to a iron-graphite intercalated phase? Plasmic Physics (talk) 10:54, 29 May 2014 (UTC)

6.70% by weight is where you go from a cementite-iron to a cementite-carbon binary system, according to William Callister's Material Science and Engineering. But in practice, you'll never want this much carbon in your cast iron, because that would make it very brittle. As for how to alternate between an iron-cementite and an iron-graphite system -- that depends on heat treatment and alloying elements, not carbon content. 24.5.122.13 (talk) 20:04, 29 May 2014 (UTC)

Thanks you. With regard to your final note: consider the ideal situation of a fully annealed, binary system with carbon as the only alloying element. P.S. I think that is would be appropriate to call 6.70% the critical content - that is to say, a technical demarcation between alloy and ceramic. Plasmic Physics (talk) 06:55, 30 May 2014 (UTC)

In your example, about 2% would be where the system goes from iron-cementite to iron-graphite (the former being known as steel, and the latter as cast iron). 24.5.122.13 (talk) 07:48, 30 May 2014 (UTC)

Where can I find a phase diagram that shows the fully equilibrated phases? Plasmic Physics (talk) 13:41, 30 May 2014 (UTC)

USRDA values for sodium in canned veggies

Does the values listed on the can include the liquid in which they are packed ? Presumably a large portion of the sodium is there, and I always drain and rinse them first, so do I get less than the amount listed ? If so, how much less ? StuRat (talk) 15:06, 29 May 2014 (UTC)

Here is the USDA searchable database of nutrition info online [11]. Here is a guide for reading nutrition labels [12], and here is a FAQ on nutrition labels [13]. Finally, here is the federal code regulating food labeling [14] I think you might need to wade into the last link for a clear answer. The FAQ link says that pickled vegetables use drained weight for serving size, but that other canned veggies include liquid in serving size. SemanticMantis (talk) 15:52, 29 May 2014 (UTC)

Wow, that last document is a mess (46 pages of text, with no table of contents, index, or even section headings). I'm sure glad the authors don't write Wikipedia articles. I was able to do a search on "canned" and found that they don't include the liquids in canned foods where the liquid isn't normally consumed. However, I have no idea which canned items do or do not qualify under that definition. For example, if I buy canned pineapple, I consume the liquid if it's packed in pineapple juice, and discard it if it's packed in sugar syrup. If they leave it up to the producers to decide, they will likely leave out the liquid, to make it seem healthier. StuRat (talk) 13:34, 30 May 2014 (UTC)

Time it takes for cigarettes to catch fire longer or shorter than time it takes to catch fire from matches?

I went camping this week, and I pulled out a box of Diamond brand matches. I lit a match to start a campfire and within maybe 1 second the fire on the tip of the match very nearly reached my hand that was holding the match. I like camping, but that was too close a call. I'm thinking of just lighting a cigarette (with my lighter) and throwing it on the tinder. If I use a cigarette instead of a match, will the tinder take more time to catch fire or will it catch fire more quickly? Stoned stoner (talk) 22:16, 29 May 2014 (UTC)

In my experience it is incredibly hard to make anything catch fire using a lit cigarette. You can drop one into a pool of petrol and all you get is a soggy ciggie. (But please don't try this at home. If you must try it, do so out of doors). And here's a citation for those who doubt my omniscience. Petrol lit with a cigarette? Only in the movies DuncanHill (talk) 22:42, 29 May 2014 (UTC)

Given the fact that gasoline fumes can ignite, I strongly recommend against trying that at home or anywhere else, except with a trained professional. Firemen will sometimes conduct fire extinguisher training by pouring gasoline into a large metal tray, and then setting it ablaze. Being careless with gas fumes can lead to the situation in this old Burma Shave series: "He lit a match / To check gas tank / That's why they call him / Skinless Frank." Like you, I question the notion of a cigarette being used to burn the kindling. But there are alternatives. For one, the OP could use the cigarette to light the next match, which might give him a little more time. Matches do burn quickly, though. Another alternative would be to use fireplace matches, which are several inches long. Or, if using a lighter, it might be safer to use the type of light that is likewise several inches long, as used for starting grills and the like. Regular lighters should work too, but that might put you too close to the kindling when it ignites. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:12, 30 May 2014 (UTC)

• Commercially sold cigarettes have additives that prevent them from self-extinguishing. (I don't smoke, and wont look, but you can.) They burn at a pretty constant rate without breath needed from when lit til when the flame reaches the filter. Joints, however, will go out if you don't drag on them. For this reason a cigarette itself might be good tinder. But I have never really had any trouble at all setting a campfire with a match and dry cellulose kindling. μηδείς (talk) 04:09, 30 May 2014 (UTC)

Your first sentence is rather out of date. See Fire safe cigarette, particularly the "Regional implementation" section. Deor (talk) 08:56, 30 May 2014 (UTC)

Thing things that happen when you are not paying attention! μηδείς (talk) 19:06, 30 May 2014 (UTC)

• Okay, lots of things going on here. First, the match won't burn that fast if you hold it angled upward instead of downward. Second, lighting a fire easily is all about having the right kind of kindling -- thin dry wood shavings are best. (Twigs are hard to light.) It's also essential to allow air to get in under the kindling. Third, a lighter works a lot better than a cigarette. Fourth, contra Medeis, don't try to use cigarettes as kindling -- they don't work. Fifth, at outdoor stores you can buy little "starter cubes" that work excellently -- you can light them with a match or lighter, slide them under your kindling, and they burn fiercely for a couple of minutes. In fact if you are feeling energetic you can make your own firestarters, by soaking compacted dryer lint in melted candle wax. Looie496 (talk) 13:33, 30 May 2014 (UTC)
  • Holding the match with the flaming end up, is an excellent point. If it's tilted downward, the flame moves much faster. Your mentioning candle wax made me think of a couple of things. One is that even getting a candle to light can take more than one match. But if you happen to have candles on that camping trip, once you've lighted one you can use it to light other things - like cigarettes - and like a piece of kindling wood (which, as Looie suggests, needs to be very dry). ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:10, 30 May 2014 (UTC)
    • The dryer lint makes a big difference. If you have compacted lint soaked in wax, it takes a little bit of effort to light, but once you've lit it, it will burn fiercely. Looie496 (talk) 15:12, 30 May 2014 (UTC)

The key is "temperature of combustion". Cigarettes must burn slower than kindling for obvious reasons - and burn at a lower temperature than is needed for combustion of kindling (shavings - not whole sticks) to catch fire as a rule. Matches, on the other hand, are designed to "burn hot and fast" so they can light other things. If you wish to light a campfire, I suggest you not use "kitchen matches" which are mainly used to start gas fires in a kitchen (and birthday candles). Campfire matches are generally of thicker wood (i.e. slower burning to your fingers) and longer. For us lazy types, roll up a cone of newspaper, place it into the kindling, and light the newspaper. Collect (talk) 14:37, 30 May 2014 (UTC)

If you're having trouble lighting a campfire (damp material, poor fuel, not enough tinder/kindling), there are ways to cheat. The simplest is to use a small tea light candle to start things off; the constant heat and flame will help dry out damp fuel and the long burn time ensures you'll get a chance to build up the fire. Slightly less wimpy is to make a crude candle yourself by squirting vegetable oil onto a rolled up paper towel, essentially turning it into a large wick. Not as long lasting, obviously, but less embarrassing than using the candle. :) Matt Deres (talk) 15:15, 30 May 2014 (UTC)

There are also some local solutions to things - for example, white birch bark is really effective. Wnt (talk) 16:23, 30 May 2014 (UTC)

Watch this from about 1:15 onwards. HiLo48 (talk) 22:20, 30 May 2014 (UTC)

May 30

Hair follicles

Is it possible that a grey hair can be produced as a result of a damaged hair follicle from over plucking? Has there been any research on this? And also, does the human body attempt to repair damaged hair follicles?

Not according to the article. 24.5.122.13 (talk) 02:06, 30 May 2014 (UTC)

It doesn't mention overplucking, but it does mention stress. I went from having a few grey streaks when I was 33 to being about half grey when I was 34 after being hospitalized for several months and having several major surgeries. None of them involved plucking, however. μηδείς (talk) 04:23, 30 May 2014 (UTC)

The classic example of how stress causes grey hair is US presidents...just look at photos of them through their terms in office and compare them to other people of similar age. The result is fairly clear. SteveBaker (talk) 15:20, 30 May 2014 (UTC)

It's a popular and oft-cited example, but I doubt that it's a particularly good one. The average age of a U.S. President at accession is 54 years, 11 months. (Only two Presidents came in under the 45-year-old mark, Teddy Roosevelt – who assumed the presidency after McKinley's assassination – and JFK.) If you take a 55-ish-year-old man – particularly one who started out with a bit of that distinguished-elder-statesman grey at the temples – and add two terms, you get a 63-ish-year-old man. (George W. Bush, incidentally, hits those averages almost exactly spot-on.)

Additional grey should not be surprising or remarkable during the transition from late middle age into one's retirement years. I would also point out, rather cynically, that there may be less use of makeup, concealer, and dye if one's image consultants aren't prepping for another election campaign. "Compare them to other people of similar age" is a hell of a red herring. It's easy to find well-preserved and poorly-preserved individuals of any age. (The years have been much kinder to Sean Connery than they have to Keith Richards.) Ideally, we'd do some sort of twin study, but unfortunately no identical twins have (yet) been elected President. TenOfAllTrades(talk) 17:53, 30 May 2014 (UTC)

Then why do some young people, including some children, have a single strand of grey hair, when they are otherwise perfectly healthy? It can't be related to ageing. 2.221.69.177 (talk) 10:00, 30 May 2014 (UTC)

The article says "The age at which graying begins seems almost entirely due to genetics," and earlier "For some people this can happen at a very young age (for example, at the age of 10)." -- BenRG (talk) 18:12, 30 May 2014 (UTC)

Insect identification

Does anyone know what this flying insect is, please?—msh210℠ 06:18, 30 May 2014 (UTC)

I wouldn't be able to anyway, but from reading many similar queries on the Ask a Biologist website (have you tried there?), I can say that you'll need to state where in the World this was before anyone can have a realistic chance. The approximate date would probably also help. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:18, 30 May 2014 (UTC)

I hadn't and haven't tried there: it's for school use only AFAICT.—msh210℠ 21:35, 30 May 2014 (UTC)

Yes, more info will probably be necessary to get to family_(biology) level or more specific. At the order_(biology) level, I think it's a Hemipteran, a.k.a. a "true bug." The best way to confirm this would be to catch one, and check for sucking mouthparts and 5-segments on the antennae. SemanticMantis (talk) 15:16, 30 May 2014 (UTC)

Okay, more info: I found it in my home in St. Louis County, Missouri, the other day. There was only one of them (that I saw).—msh210℠ 21:35, 30 May 2014 (UTC)

Flouride

Is there any evidence which suggests that over use of flouride toothpastes are bad for gums?

Fluoride#Topical seems to say that concentrated fluoride itself is caustic, but of course toothpaste won't contain those concentrations. However, this isn't unique to fluoride, we also ingest many acids and bases every day, but normally not in concentrations that would harm our gums (or anything else).

Toothpaste is also abrasive, and a stiff brush can also irritate the gums with overly rigorous brushing. StuRat (talk) 13:28, 30 May 2014 (UTC)

Surely "over-use" is by definition bad.--Shantavira|^{feed me} 15:04, 30 May 2014 (UTC)

Yes, but not necessarally bad for the gums. StuRat (talk) 16:15, 30 May 2014 (UTC)

Flour (note sp.) can be even more hazardous for the general health than fluoride (note sp.). -- Jack of Oz ^{[pleasantries]} 21:29, 30 May 2014 (UTC)

Well, not in comparable quantities. --Trovatore (talk) 21:35, 30 May 2014 (UTC)

Optimum speed for an automotive alternator

I have searched for, but not found, speed/current curves for car alternators. Basically I'm looking for the lowest speed at which an alternator will deliver its rated current. I'm working on an alternate energy project where using widely available car alternators (70-100A range) makes the most sense, for a variety of reasons. The Alternator (automotive) article says alternators run at 2 to 3 times crankshaft speed, but says nothing about the optimal speed range. Another issue is the torque needed for starting and at rated output. I'm guestimating that a 100A alternator would need around 2kW of drive power, is that a reasonable estimate? Roger (Dodger67) (talk) 17:45, 30 May 2014 (UTC)

The voltage coming out of an alternator depends on two variables: the speed at which the alternator’s field is rotating and the amount of current flowing through the field coil (i.e. the strength of the magnetic field); a regulator varies the latter to keep the output at 14.4V to charge a 12V car battery. This article describes difficulties encountered if trying to run an alternator below the speed range for which it is self sufficient. From Bosch there is a technical specification available to credit card verification. 84.209.89.214 (talk) 19:07, 30 May 2014 (UTC)

I'm not sure I would trust that ebook site. If Bosch provides the spec for free then it should be available through them. I doubt that freebookez.com has distribution rights to that, and free things shouldn't need credit card information. Katie R (talk) 19:47, 30 May 2014 (UTC)

This has output curves for a generic alternator series. [15] Katie R (talk) 19:50, 30 May 2014 (UTC)

Alternators in cars and trucks are designed so that there is significant output at engine curb idle speed. Curb idle is usually around 600 to 900 RPM, at the low end for larger V8's and at teh high end for tiny bubble car engines. Large high speed diesel engines for industrial, marine, and heavy truck use all curb idle at 750 RPM. You can obtain the alternator speed by measuring the pulley diameters - alternator RPM = curb idle x crank pully / alternator pulley. Automotive alternators should be around 85 to 90% efficient at crusing RPM (1000 engine RPM typical), so your estimate of mechanical input power is not unreasonable. Flodad 121.221.223.1 (talk) 02:20, 31 May 2014 (UTC)

How was it possible to destroy treasure in a bonfire?

I've read multiple accounts of defenders in sieges, before a last stand, to make a bonfire and burn their treasure to prevent it from falling into enemy hands. However, as most treasure in pre-industrial times was made out of gold or silver, how can they be damaged or destroyed in a bonfire? If part of the treasure was velvet or similar luxury clothing, then fire can indeed destroy it, but what about gold, silver, gemstones, etc.? Is the heat of a bonfire enough to at least partially melt golden chalices and jewelry? This might decrease their value, but the material can still be salvaged. --5.15.0.179 (talk) 18:02, 30 May 2014 (UTC)

It might be helpful if you could link to some specific accounts so we could give a better answer. In some instances, 'treasure' might be rather broadly defined to include all kinds of valuable (including functional) items that could have worth not linked to their intrinsic metal content—tools and weapons, for instance. Going from an ingot of steel to a fine sword is a costly bit of labor. (And even when metal can be salvaged, it may require refinement or resmelting to remove impurities introduced during the uncontrolled melt.) Some gemstones will survive fire better than others; diamond will actually burn in a hot fire. (This PDF offers some guidance to artists who want to know if precious and semi-precious stones will survive in a kiln.) TenOfAllTrades(talk) 18:19, 30 May 2014 (UTC)

FWIW, some gemstones are heat treated for improvement of colour - lots of interesting material out there. Collect (talk) 18:23, 30 May 2014 (UTC)

Diamonds burn...but their ignition point is 850 to 1000 degC. Gold also melts at around 1000 degC, silver at 950. So doing anything much to these materials requires temperatures around 1000 degC...but a decent log bonfire can reach that kind of temperature in the center - so it's certainly possible. Gold is really unreactive though - you can't get rid of it by burning it.

I've also read about people in these dire circumstances either burying their gold - or tossing it into deep wells. That seems like a fairly reasonable strategy.

SteveBaker (talk) 20:23, 30 May 2014 (UTC)

It's irrelevant to the question, but Steve's last paragraph reminds me of the unusual way that two Nobel Prize gold medals were hidden from the Nazis when they occupied Denmark. On the other hand, around the same time Alan Turing buried some silver bars in case England was also invaded, and then never managed to find them again. --69.158.92.137 (talk) 21:18, 30 May 2014 (UTC)

It would be interesting to read the accounts. I imagine that sometimes this tactic would pay off handsomely. For example, if you throw some gold bars in a cottage and set it on fire, a group of raiders isn't going to want to hang around picking through the burning embers thinking there's gold in there somewhere. Then you come back, spend half a day searching, and your wealth is intact (except for the cottage). Wnt (talk) 22:48, 30 May 2014 (UTC)

Why do animal babies scream?

Why do wild animal babies cry out when you grab them?

What evolunentary purpose does it serve for example for a wild gosling to scream when you pick it up, and the parents don't even run towards you they just hiss a bit and then waddle off with the other babies leaving the captured one to die?

The hypercritical person released the gosling

This may be too simplistic of a view, and granted, it's from my own observations, but: It's a natural response for the young of many species, including humans. It attracts the parents' attention and lets the would-be predator know that help may be on the way, similar to a car alarm. Justin15w (talk) 21:52, 30 May 2014 (UTC)

If you'd been somewhat closer in size to the goose, then you might've found yourself being attacked by the parents in response to their offspring's alarm call. I have heard of angry parent geese absolutely wrecking dogs and cats, for example. A somewhat larger bird, the swan would likely seriously consider taking you on (yes, never mess with cygnets). --Kurt Shaped Box (talk) 22:56, 30 May 2014 (UTC)

bottled water

Why does bottled water have an expiry date? Does water "go off"? Think glass bottles because I know plastic bottles grow leeches into the water after a while

One would hope there are no leeches growing in the water! There should be an article on shelf life which could answer some questions. One thing about bottled water is that it seems typically to be dated to "expire" some number of full years after the bottling date. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:45, 30 May 2014 (UTC)

Glass bottles can still have plastic gaskets or seals in the screw top that can leach phthalates. [16]--Aspro (talk) 23:07, 30 May 2014 (UTC)

dream recall

What substances are scientifically proven to dramatically improve dream recall / memory? Like eating a slice a cheese and remembering every dream you had during the night, but I want references and verifiable facts not hearsay about cheese. Thanks InceptionFan (talk) 22:54, 30 May 2014 (UTC)

Here is an article that has some good references. Start there and see where it leads you. --Jayron32 23:02, 30 May 2014 (UTC)

A procedure of dream researchers that is also followed by writers intent on capturing plot ideas in dreams is to keep a notebook and pencil ready at their bedside. Dreams can be most vividly recalled immediately after gentle waking from the REM phase of sleep. 84.209.89.214 (talk) 00:22, 31 May 2014 (UTC)