Wikipedia:Reference desk/Archives/Science/2014 May 27

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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)

Perhaps they are thinking of a location where cows would be impractical, like a space station. StuRat (talk) 00:00, 1 June 2014 (UTC)

What about spherical cows in a perfect vacuum? 24.5.122.13 (talk) 01:31, 2 June 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)

Minor point: thermalized photons aren't Maxwellian; they're, well, Planckian. --Tardis (talk) 03:39, 2 June 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)

The problem of present cosmology is that it conceives of the universe as an ordinary object which has particular properties as a whole which change in time –so would, as seen from an imaginary observation post outside of it, look different at different (cosmic) times, as an object which lives in a time realm not of its own making.

The fact that it cannot actually be inspected from the outside (or, equivalently, that mass, energy, space and time aren’t defined outside of it) wouldn’t matter if particles would have been provided with properties at their creation: if they only would be the cause of their interactions. Now if the universe would contain only a single electrically charged particle among many other kinds of particles, then it wouldn’t be able to express its charge –in which case it cannot be charged itself. A property, any property, for that matter, then must be something which lives within particle interactions.

If in a universe which creates itself out of nothing, without any outside interference, particles must create themselves, each other, then particles, particle properties must be as much the cause as the effect of their interactions.

In that case it is no longer legitimate to conceive of the universe as an ordinary object which has particular properties as a whole, as an object which only for practical reasons cannot be observed from the outside.

If the very most fundamental law if nature is the (conservation) law according to which what comes out of nothing must add to nothing, then in a universe which creates itself out of nothing, everything inside of it, including space and time, must add to nothing, cancel –which is not unlike how the sum of all debts and credits on Earth is always zero. The universe then is that unique, paradoxical, extraordinary ‘thing’ which has no external reality as ‘seen’ from the outside but only exists as seen from within.

So whereas a Big Bang Universe evolves in (cosmic) time, lives in a time realm not of its own making so has a beginning, a certain age, since a Self-Creating Universe doesn’t exist as ‘seen’ from the outside, it ‘contains’ and produces all time within –so here clocks must be observed to run slower as they are more distant even when at rest to the observer.

If the universe cannot have particular properties as a whole as ‘seen’ from the outside, then it also cannot have particular properties and be in some particular state as a whole as seen from within.

If particles, particle properties are both source and product of their interactions so owe their properties to one another, and the same holds for the objects they form, if we can only speak about the properties of an object if there is an environment in which they can be expressed in interactions with other objects, then in speaking about the properties of the universe, we in fact state that it owes its properties to something outside of it: that it has been created by some outside intervention.

The Big Bang hypothesis therefore is a naïve, essentially religious tale, never mind the observational ‘evidence’.

This is why I'm looking for an alternative explanation as to the origin of the CMB. Antonquery (talk) 03:31, 31 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, 27 May 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)

A masonry drill would qualify as "special equipment". What did you use, diamond-tipped drill bits, or maybe just corundum ? You don't find this stuff in the average tool box. We used a regular drill with steel bits. They were too short, so we had to drill from both sides and try to get it to meet in the middle. Also, the brick dust was rather annoying, requiring a breathing mask and goggles. And the drill kept overheating, too. Sure, we could have bought a masonry drill and bits, but we've never had to drill through masonry before or since, so that would be rather expensive for a one time use.

Re "as far as I can see", yes, that's the problem, you can't see past the shores of Australia. StuRat (talk) 05:42, 31 May 2014 (UTC)

What did I use? A masonry drill of course. Drill (hammer drill with 18 mm chuck) and masonry bit purchased in local hardware store. Drill made in Spain for Bosch and cost probably about $60. Hardly "special equipment". Drill bit, 30 mm cutting and 18 mm shaft made in Australia and cost about $10 - lasts for years, proably a lifetime. For almost all bricks for small holes you don't really need the hammer drill - an ordinary electric drill will do just fine. Manually bang it in and out every second or so. You really only need the masonry bit. They get very hot but they are designed to take it to a certain extent. House bricks are quite soft compared to concrete, monazite and granite, and mortar even softer. You don't need diamond tipped bits for bricks and mortar. If you have to drill through 100 mm or more solid concrete it's best to use a hammer drill. You know you write nonsense as you go along. Only an idiot would use an ordinary HSS drill bit in masonary. Floda 121.221.223.1 (talk) 07:04, 31 May 2014 (UTC)

Only an idiot would spend $70 for a tool they will only ever use once. A normal drill did eventually get the job done, it just took a long time and was quite annoying. And $70 is about the cost of the entire "window rattler", so you're really increasing the costs by switching to another type. StuRat (talk) 21:02, 31 May 2014 (UTC)

You said you cracked bricks - surely your landlord did not appreciate that. You are very silly StuRat. Can't you read? My drill has been used hundreds of times, for all manner of jobs. Don't you know you can switch hammer mode on or off? - you can use the drill as a plain drill. If I need to use a tool only once, I can rent it. A hammer drill would probably cost about about $10 to rent for the day - I imagine the USA is no different in that regard. I had mentioned it in the context of drilling a hole to install a spit system airconditioner - these typically cost about $700 upwards. Window rattlers cost about $300 upwards, but most folk avoid them because they are unsightly, they make more noise, and you either have sacrifice part or all of a window, or cut a dirty great rectangle out of a wall. A window rattler nearly always has to be positioned so that your neighbour hates the noise too. Spilt systems compresor units, because they can be physically larger and werigh more, are quiet and can be better located so as not to annoy the neighbours. That's why they've pretty much driven window rattlers out of the market. And don't claim I'm only looking at Australia. You and I both know that Chinese factory's main market is the USA - and the factors I've mentioned apply anywherre in the World. Floda 121.221.223.1 (talk) 02:12, 1 June 2014 (UTC)

No, they don't, you just think they do. For example, a window A/C unit can be had here for far less, I found three models at Walmart for $109, and that's not even a sale price: [1]. You just ignore all differences in prices, climate, building construction methods, electricity prices, etc., and assume that whatever applies to Australia must apply worldwide. When you factor in all the differences, you find that things are actually done differently in different parts of the world, and for good reason, not because everyone outside Australia is an idiot. StuRat (talk) 02:47, 1 June 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)