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January 18

Coherent or highly monochromatic terahertz

Brain fart corrected in title, sorry

I was looking at a paper about imaging cancer with terahertz that is monochromatic, but I'm not sure how monochromatic:

Measurements were performed using a THz time-domain spectroscopy (THz-TDS) system based on a Ti:sapphire femtosecond oscillator (Synergy; Spectra-Physics) pumped by a 10-W diode laser, Verdi. The laser delivered 10-fs pulses at a wavelength of 800 nm with an 80-MHz repetition rate. The laser beam was separated by a polarizing beam-splitter and turned towards the emitter and the detector separately. The emitter was a p-InAs crystal that utilized the photo-Dember effect, and the laser beam was incident at 78° on the surface of the crystal for high THz intensity51. The THz beam that radiated from the emitter was gathered by a parabolic mirror and focused onto the sample holder by a pair of THz focusing lenses

My assumption is that this generates noncoherent light with a narrow range of frequencies. But I don't see how narrow.

The issue here is that they detect methylated DNA in cancer cells as a little bump, maybe a bit more than a tenth of the total signal present. Most of the signal is from a smooth curve of absorption by ice. The thing I'm getting at is that if they had a tighter range of frequencies, they might get a higher signal if they tune precisely right. I also don't know whether the absorption by ice might break up at a very fine scale, with bands where there is no absorption, if you had truly monochromatic terahertz waves to test with???

Obviously what I want to do is find something only the cancer absorbs and turn it up to MICROWAVE HIGH setting until every last tumor cooks through and through, while normal tissue with just a little methylated DNA gets toasty warm but not damaged. Wnt (talk) 01:24, 18 January 2018 (UTC)

Looking at graphs in this doi=10.1088/0022-3727/47/37/374002 paper, you only get about one full cycle of the THz radiation, and it drops off exponentially with time on the scale of 1ps. So it is actually hardly monochromatic, and would have a bandwidth of 100s of GHz. This would depend on the duration of the laser pulse. If you could pulse your laser every 2 ps perhaps you could get it as coherent as the pulse rate, but then you would have a near THz generator driving your laser anyway! On the topic of selecting DNA methylation, it is found in all kinds of cells, so perhaps it is not targetable. A vibration of a methyl group in a liquid environment may have a band, but it would not break down into fine lines due to the varying environment of the liquid. Graeme Bartlett (talk) 05:26, 18 January 2018 (UTC)

So is there any known way to make more monochromatic THz radiation? I would think this should be the hottest topic in weapons work right now (to DNA-identify people from space or displace specific binding factors and cause a different syndrome in every member of the political opposition), but all I want to kill this time is cancer. Wnt (talk) 14:55, 18 January 2018 (UTC)

You should read Terahertz_time-domain_spectroscopy. Ruslik_Zero 20:32, 18 January 2018 (UTC)

Canon de 75 modèle 1897: The Italian Response

I need help finding an artillery gun based on this information.

After taking notice of the success of the Famous French 75, Italy manufactured their own, indigenous design of the artillery piece. Although it had the same rate of fire as the Canon de 75 modèle 1897, it was more mechanically complex and was not as successful. Arima (talk) 04:42, 18 January 2018 (UTC)

Cannone da 75/27 modello 11 seems a possible candidate. The main italian field gun in WWI, the Cannone da 75/27 modello 06, was a licence-built Krupp design. Try List of artillery by country#Italy. Alansplodge (talk) 11:07, 18 January 2018 (UTC)

Cold desert at night

So if rock holds heat so well, why does the desert get freezing cold at night? Rock does hold heat well, right? Anna Frodesiak (talk) 09:12, 18 January 2018 (UTC)

Not as well as bodies of water. Also deserts have low precipitation, so often clear skies, thus the optimum for radiative losses.

It's a delusion amongst the flat earth people that "Moonlight radiates cold". Indeed, moonlit rocks are often colder than those which aren't. However the reason is that days are hotter than nights, and so night temperatures depend on how fast things are cooling, not how well they're being heated. An area exposed to clear moonlight is the same area that's losing the most by radiation. Andy Dingley (talk) 09:29, 18 January 2018 (UTC)

Thank you, Andy. So this is about very clear air above allowing heat to escape, and about lack of moisture within the ground, which holds more heat than dry sand? (I've slept on both sun-baked earth and desert, and wow, that sand and air gets cold.) Anna Frodesiak (talk) 11:22, 18 January 2018 (UTC)

Yes. We have an article: Radiative cooling. "The exact process by which the earth loses heat is rather more complex than often portrayed..."

Here's a great free textbook on weather: Aviation Weather. I actually like the old version - I keep a link to it on my user-page - the AC 00-6A version - it still has the original cartoons from 1943's Meteorology for Pilots!

If you like math, you can use the Stefan-Boltzmann law to study why deserts get cold. Here's some science from Arizona State University - a world-reknowned center for excellence in both deserts and planetary science: Stefan-Boltzmann law for radiative cooling. In my old planetary science class, we were taught by a radioscientist, so he made sure we corrected for the non-zero cold sink of the cosmic microwave background radiation: on a clear night with no clouds, your desert ground is essentially losing heat to a cold-sink that's only a few kelvins! This is why it is possible to use a clear desert night to produce ice, even if the air temperature is above freezing! If you're really smart, you can make the physicists mad by pretending to violate the second law of thermodynamics, like this Nature letter demonstrates! Hey, I recognize that photograph - I've spent a lot of time on that roof looking skyward!

Nimur (talk) 17:18, 18 January 2018 (UTC)

The theoretical Volumetric heat capacity of Silica (Sand, Sandstone, Glass) is 1.5, of Water 4.18 and of Air 0.0013 J⋅cm³⋅K⁻¹ (Joule per cubic centimeter per temperature difference of 1 Kelvin). So Sand, which always contains some air is not a good material to store heat. Like a battery that can store 1 Kw/h compared to one that stores 4 Kw/h. The volumetric heat capacity of Sand is actually only around 0.8 tho there are many different "mixtures" of minerals called Sand and thus it can be a bit higher or lower. Additionally by definition deserts contain the least amounts of water. Thus a desert is physically less able to store the heat from sunlight and it gets hotter with less "energy efford" aswell as cold faster when the heat disperses. --Kharon (talk) 13:59, 18 January 2018 (UTC)

It has not been mentioned yet, but the ability to store heat (measured by the heat capacity) is not the same as the ability the regulate the environmental temperature. The specifics depend on a lot of complex phenomena (see convection), but one key variable is thermal conductivity.

For a quick example, in cold weather, it is less unpleasant to touch ice than a metal bar, even though the specific heat of ice is more than twice as high as that of aluminium (per kg, so that is even more per volume). (Solid-to-solid contact does not involve convection, and the driving variable is thermal effusivity.) Tigraan^{Click here to contact me} 10:34, 19 January 2018 (UTC)

Thank you, especially Nimur for the really good pdf. Weather has always mystified me and this is really interesting. And no, anything about maths goes way above my head. :) Anna Frodesiak (talk) 22:10, 18 January 2018 (UTC)

One reason for the "Moonlight radiates cold" adage is that moonlight indicates a lack of clouds, and clouds act like a blanket to hold in some of the radiant heat. —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 05:40, 19 January 2018 (UTC)

If the daily temperature range's x tens of degrees in Atacama-grade air will it be at least 1°F less if there was more water vapor? (but not so much that condensation wets the ground at dawn or causes cloud) Sagittarian Milky Way (talk) 07:15, 19 January 2018 (UTC)

"Rock holds heat well" hides some complexity. What it's really about is that rock is a good insulator. This means it doesn't exchange heat quickly with its surroundings. This means hot rocks will stay hot for a long time (and, of course, the inverse). That's heat that isn't leaving the rock for its surroundings. Meanwhile, once the Sun goes down, atmospheric heat gets carried away via convection, which occurs rapidly. You probably don't live in an underground burrow, so you lose heat to the atmosphere. --47.157.122.192 (talk) 09:37, 19 January 2018 (UTC)

I can't find any good references at the moment, but one thing to consider is that "rock holds heat well" really only applies on a per-unit-mass basis. Rock is opaque, solid, and a poor conductor, so only the very surface gets heated by the sun, which in turn means it can loose that heat relatively rapidly once heating stops. In contrast, water is transparent, so solar heating affects a larger volume. Depending on the weather, it can also be physically mixed, transporting surface heat to a greater depth. This means that water bodies have a much larger effective heat capacity than rock, and so take longer to both heat up and cool down. Iapetus (talk) 10:55, 19 January 2018 (UTC)

Carbon fibre

How much weight can a carbon fibre sheet hold, in:

1) 1 inch thick sheet.

2) 1 feet long stand, filled round stick or non-filled round stick.

Also,

I require a calculating method or so, to calculate weight vs. height, length, filled/non-filled carbon fibre base.

123.108.244.156 (talk) 15:45, 18 January 2018 (UTC)

There are enough varieties in construction of such materials that you would need to be much more specific if you want quantitative results.

Typically, material properties can be found from whomever sells such materials. For example, here is one vendor listing, technical data sheets from PlastiComp. You can use standard-form equations from our article on flexural modulus to model the material. Beware that fibers and textiles are not always well-modeled by simple equations! In such a case, you'll need to track down data from an empirical test.

Nimur (talk) 16:41, 18 January 2018 (UTC)

Isn't pure carbon fibre better than mixed with plastic? What is used in formula 1 Cars? What material would you say is solid and light? 123.108.244.156 (talk) 16:55, 18 January 2018 (UTC)

Have you read Carbon fibres and Carbon fibre reinforced polymer? Also do you know what fibre means? Nil Einne (talk) 17:08, 18 January 2018 (UTC)

MPG - casues of significant improvement?

I have recently noticed a significant improvement in the mpg I get from my Fiat Punto Mk2 1.2l 8 valve. In the past I have usually got about 40-45 mpg, but the last two fills I have got 50 mpg. The types of journeys and loads have not changed. What could cause such an improvement? DuncanHill (talk) 19:40, 18 January 2018 (UTC)

Setting aside that fascination of such minutia is possibly a sign of a mental disorder ; -) It may be that DH lives in the northern hemisphere where it is currently winter. Cold air is denser. Thus the compression ratio is slightly raised thus increasing engine efficiency. 10-20 % seems a lot however. Is this metered fuel from the pump or what appears on the gauge or a mixture of both? As you may be aware, gasoline/petrol and diesel have large coefficient of heat expansion. This is why aircraft are fuelled by weight and not volume. Therefore, volumetric gauges can easily be out by 10-15% over the course of a year. RH can affect MPG as well. Oh, and of course, have you recently inflated the tyres/tires ? That can reduce the rolling friction too. So that dispenses with the most obvious. Back to you to add more info. Aspro (talk) 20:25, 18 January 2018 (UTC)

Metered from the pump, Northern Hemisphere, no change to tyre pressures. Nothing mentally disordered about noticing that you're saving money! DuncanHill (talk) 20:54, 18 January 2018 (UTC)

Perhaps you are just driving more efficiently since you have become interested in mpg. Dmcq (talk) 23:36, 18 January 2018 (UTC)

• Another possibility, seasonal change of boutique fuel: [1] , [2] , [3] , etc., etc., etc... (no article?) —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 00:23, 19 January 2018 (UTC)

I don't think we have "boutique fuels" in the UK. DuncanHill (talk) 00:26, 19 January 2018 (UTC)

I haven't done an exhaustive search, but its possible that your fuel provider changes blend seasonally; cf:[4] —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 01:29, 19 January 2018 (UTC)

If there's a way to get 11-20% better fuel efficiency from a car (similar to my own), I'd really like to know about it! The only possible factor I can think of in this instance, Duncan, is that it's been somewhat windy in the UK of late – is it possible that by lucky chance your recent journeys have experienced more favourable wind assistance (and less wind resistance) than average? {The poster formerly known as 87.81.230.195} 90.200.41.3 (talk) 00:45, 19 January 2018 (UTC)

Or, he drives downhill -- both ways. —2606:A000:4C0C:E200:3C54:1374:B00A:7382 (talk) 01:14, 19 January 2018 (UTC)

Gasoline is denser at cold temperatures, so you get more kgs per gallon. Add to that that maybe you took an extra motorway trip or avoided some traffic jams (maybe roads were quieter because of holidays), and 10-20% is certainly possible, especeially if you have a 30-40 L tank. — Preceding unsigned comment added by 78.0.222.210 (talk) 02:23, 19 January 2018 (UTC)

@Aspro: Cold air is denser. Thus the compression ratio is slightly raised thus increasing engine efficiency. - huh? The compression ratio is a geometric factor, and while it may be affected by a few ppm by metal contraction in cold weather, it has little to do with air density. Tigraan^{Click here to contact me} 10:22, 19 January 2018 (UTC)

Gasoline is indeed denser in winter, but it does not explain everything. The CTE is about 0.1% per °C, so assuming a 30°C swing between summer and winter temperature, that explains 3%. Significant, but certainly not "10-15%" (that would require a 100-150°C swing, which no place on Earth has ever seen). Tigraan^{Click here to contact me} 10:28, 19 January 2018 (UTC)

Thanks for all the suggestions. I haven't noticed similar improvements in previous winters. Indeed, if memory serves, cold damp weather in the past has led to an increase in consumption which I have put down to it being a bugger to start and misfiring until it warms up (if it passes the next MOT I might buy it new coils and HT leads as a treat). Hmm. I think my last couple of long-distance trips were smoother than usual - there's a new bit of dual carriageway over the moors, that would help. And it's possible my driving habits have improved. It's just rather disconcerting to get such a major improvement on an old car - was worried it might be a sign of impending doom! DuncanHill (talk) 14:36, 19 January 2018 (UTC)

The way to mitigate miss firing is to treat yourself to a 'sports' coil and new HT now ! For Italian's are cheap skates and just deliver cars at the lowest possible price. Then spray the HT over with 'damp start' to seal out the moister. Cost-wise this will pay for the outlay. Another is to use a sump heater such as [5]. They use so little paraffin/kerosene per week that the running cost is negligible. Throw an old woollen blanket over the bonnet/hood, as the engine is a big block of metal and acts as a thermal store, so capitalize on it. Finally, don't forget the battery/accumulator. Short runs in cold weather may lead them to sulfate up – requiring a not cheap replacement. Make sure the terminals are clean and there is good electrical contact. Silicon grease is better than Vaseline in this respect and a hydrometer will indicate the condition of your battery so you can take proactive active measures before problems surface. Also, water thermostats. It should not open until the engine is up to running temperature. But if it is tired, it may not be closing properly to start with – so replace it. Some people when they start off on a cold winters morn, scrap off the ice on their widows whilst have their cars running on full choke and with the heater on full blast. Again, it is chilling the engine before it has chance to warm up and doesn’t 'pull' properly until several miles down the road. Aspro (talk) 19:41, 19 January 2018 (UTC)

Sealed battery (haven't seen an unsealed one for years). No choke (haven't seen one of those for years either). And I doubt the police would look kindly on someone leaving lit paraffin heaters under cars in the street (and where would I put it once I had driven off?), and I'm sure my insurers would have kittens! I do know not to run the heater until it's warmed up. A blanket over the bonnet would either blow away or get nicked. DuncanHill (talk) 17:35, 20 January 2018 (UTC)

I must admit seeing lorry drivers light heaters under their fuel tanks gives me a feeling of, ah um, trepidation. Dmcq (talk) 19:07, 22 January 2018 (UTC)

I hate to say it, but the most probable explanation is that one or two of your measurements were off. Wnt (talk) 12:51, 20 January 2018 (UTC)

Mileage taken from trip meter, fuel volume taken from the pump. And I can see that the gauge is going down less for a given journey now. DuncanHill (talk) 17:35, 20 January 2018 (UTC)

Could some intermittent mechanical problem you were used to have gone away? I know practically nothing about cars, but if this one has fuel injectors, could it have had a plugged fuel injector that spontaneously started passing fuel again? You mentioned something about misfiring. Wnt (talk) 17:50, 22 January 2018 (UTC)

Physics Question (one more)

Are the standard sizes and masses of a proton, neutron, electron etc. are naturally selected and why do they not change over time?

Similarly, nature has the ability of random selection too, therefore, we can't neglect completely the chances of varying masses of subatomic particles instead of standard as a proton is approx. 1850 times’ massive/heavier than an electron so it means the chances of the diversity in the masses of subatomic particles in the random selection are more than the chances of the standard masses of subatomic particles. Please disregard if not interested 50.66.1.32 (talk) 21:04, 18 January 2018 (UTC)EEK

Relevant articles include Proton-to-electron mass ratio, Time-variation of fundamental constants, and perhaps Fine-tuned Universe. -- ToE 22:12, 18 January 2018 (UTC)

Natural selection in the usual scientific sense requires the populations of entities being selected producing similar but not identical progeny with slightly varying characteristics due to occasional errors in the functioning of a genetic code. Since particular kinds of subatomic particles do not have a genetic code (or any analogue to it) and do not reproduce their own kind (though they can give rise to different kinds by decaying or combining) the concept is not applicable. The OP's second sentence ("Similarly [. . .] particles.") does not appear to be meaningful English in any of its clauses. {The poster formerly known as 87.81.230.195} 90.200.41.3 (talk) 00:41, 19 January 2018 (UTC)

The anthropic principle, while not selection, is a selection bias relevant to this question. -- ToE 02:36, 19 January 2018 (UTC)

Another possibility is that Big Bang(s) that reach 2018* tech are unlikely to end before Big Bang-causing tech makes Big Bang(s) that reach 2018* tech and are unlikely to end before Big Bang-causing tech makes Big Bang(s) that reach 2018* tech and are unlikely to end before Big Bang-causing tech makes Big Bang(s) that.. Thus if humanity doesn't want reality itself to be something a pimply alien made one science class or a quantum of hyperdrive exhaust it can help by not inventing universe-causing technology or non-human(s) that might invent it. *increment number by 1 each year. Sagittarian Milky Way (talk) 08:31, 19 January 2018 (UTC)

"Turn that off now Zxyygjqck it's time for bed"; "Aw, can I have one more billion years ma - it's just getting interesting" Gandalf61 (talk) 09:57, 19 January 2018 (UTC)

The anthropic principle seems like it may be baked in to the idea of "collapsing the state-vector", at least under some face-value versions of the Copenhagen interpretation. An electron does not pass through one slit or the other unless/until you observe it. Does this mean that the positions of all the stars in the cosmos were a blur until the First Man looked up and saw them? For that matter, were they a blur until the Last Man saw them, and the other Men before him were part of that collapse of probabilities? Is there something special about some past, present, or future consciousness of person that makes it better positioned to be the one to perceive a state that allows Him/Her/Itself to exist? What if the seventh seal is the distinction between the past and the future? Wnt (talk) 20:43, 19 January 2018 (UTC)

If you put Schrodinger's Cat box in an anechoic room, leave a microphone that can hear cat heartbeats at its distance from the box in the room before you leave and have it send the reading to you over wifi to a phone with a bushel over it do you think the screen is both cat organ noise and no cat organ noise till a human looks?Sagittarian Milky Way (talk) 22:50, 19 January 2018 (UTC)

Well, inside the box, there's no cat's meow without a live cat. Outside the box, it doesn't matter if you look by light or by a wi-fi transmission ... I think. Wnt (talk) 01:27, 20 January 2018 (UTC)

Lee Smolin's Cosmological natural selection (last version of our article before it was merged, perhaps more specifically informative) from his The Life of the Cosmos may be close to what the OP has in mind.John Z (talk) 01:02, 21 January 2018 (UTC)

• Why doesn't square green become anxious vanilla as the clock ticks below the Tropic of Cancer? See category error and The Fallacy of Fine Tuning. μηδείς (talk) 02:30, 21 January 2018 (UTC)

As others have pointed out, there is no evidence that the masses are changing. Somewhere in the last couple of months I saw someone say that the particles are defined by their mathematical values of properties. The proton is the particle that has this particular mass, etc. You don't have protons that have different masses - those would be different particles. Bubba73 ^{You talkin' to me?} 16:33, 25 January 2018 (UTC)

January 19

What's a cryogel?

Hi. The word "cryogel" appears in various WP articles but doesn't have its own article or redirect. There's also no Wiktionary entry, and I ask as someone who works on Wiktionary. Could someone give us a quick but clear definition we can use, that distinguishes a cryogel from other things (gel, aerogel, xerogel, whatever)? Thanks! Equinox ◑ 06:56, 19 January 2018 (UTC)

I can't seem to find an explicit definition of the word, but the various things I find that are referred to as "cryogels" have in common that they are made by first dissolving something in a solvent, and then freezing and thawing until it polymerizes. Someguy1221 (talk) 07:19, 19 January 2018 (UTC)

Cryogel seems to be a registered trademark. What would be the inclusive uncapitalised term? I suppose the word might enter the language as a normal term like hoover and vaseline. Dbfirs 08:12, 19 January 2018 (UTC)

This is the website of the company which manufactures it, with plenty of details [6]. Here is a definition from a technical glossary [7] which might be a basis if you wanted to write something, but that is Russian, and elsewhere there might be trademark issues. Wymspen (talk) 10:11, 19 January 2018 (UTC)

Thanks for the feedback! So I gather it might be a trademark. But if ya look at Google Books [https://www.google.co.uk/search?q="cryogels"+the&btnG=Search+Books&tbm=bks&tbo=1&gws_rd=cr&dcr=0&ei=FcZhWo34AcbbgAbirqeQDQ] you can see a lot of apparently generic talk about "cryogels". The plural and lack of caps suggests maybe the writers often see it as a generic term. Equinox ◑ 10:20, 19 January 2018 (UTC)

Found a review of the biological applications, which describes them as "macroporous gels produced at subzero temperatures (known as cryogels)". Klbrain (talk) 00:55, 20 January 2018 (UTC)

References

Current uses of radium-226

Does anyone actually still use radium-226 for anything? (That's the most stable isotope, which used to be the common one used; I know ²²³Ra is used as a radiopharmaceutical). The sources in our radium article on current uses are from last decade, and even then those uses were being supplanted: we usually use other isotopes (e.g. ¹⁹²Ir, ⁶⁰Co) for industrial radiography instead, and we usually use actinides (Pu, Am, Cf) for neutron sources instead of Ra. Is the main use of ²²⁶Ra really just to get rid of it by transmutation to ²²⁷Ac, like Ullmann's Encyclopaedia said in 1993? Double sharp (talk) 13:01, 19 January 2018 (UTC)

According to this the main use is the production of radon. Mikenorton (talk) 13:25, 19 January 2018 (UTC)

That's interesting, though I'd like to see where they got that information from. At first glance it seems to me a bit overdoing it to produce pure Ra specifically to get Rn: you can get Rn from anything above it in its decay chain quite easily (it's a gas, while its parents aren't, so the separation is trivial), so isn't a chunk of uranium ore already a serviceable radon source? Double sharp (talk) 13:49, 19 January 2018 (UTC)

For uses of Radon see Radon#Applications, although it doesn't look like it gets much use these days, for production see Radon#Industrial_production, which supports it being produced normally from radium, even if the need for it is not great. Mikenorton (talk) 16:35, 19 January 2018 (UTC)

January 20

Astronomy Question

The First and the Last Noon of the solar year don’t coincide. This means solar noon lags 24 hours, which appears in what we call leap year. Although we update our calendar every after 4 years for our own conveniences, however, it doesn’t mean an earth also adjust its axial and orbital motion for the sake of our calendar. This small change reverses days into nights and seasons as well (summer into winter after 720 years approx.) over time, if the real position of the earth is observed in its orbit around the sun instead of adding Feb 29 in leap years. Your comments, please. 50.66.1.32 (talk) 19:54, 20 January 2018 (UTC)EEK

This user's edit at Talk:Season#Earth’s Rotation and its Orbital Motion may be useful in determining their misunderstanding. -- ToE 20:59, 20 January 2018 (UTC)

We adjust our clocks and calendar to match the observed rotation of the earth. Much calculation over the centuries has ensured that our day and year never deviate far from the norm. If we are still around to observe, the day length (via leap seconds or hours) and the calendar (via leap years) will be adjusted as required over the next few thousand years to closely match the exact periods of rotation. Dbfirs 21:49, 20 January 2018 (UTC)

I sort of doubt that prediction, actually. Leap seconds were a mistake from the start. They cause continuing annoyances in the computer age because they make it impossible to match a civil time in the future with a timestamp based on count of seconds. They were never necessary; the drift in (say) the civil time of sunset is slow enough that no one would be disturbed by it over the course of even a long life.

My counter-prediction is that leap seconds will eventually be dumped in favor of some version of TAI or GPS time, possibly with a constant offset to avoid a discontinuity at the time of changeover. There have been several attempts to do this; the last one, if I recall correctly, didn't miss by much. There's a lot of resistance to such a change, of course, but hopefully it will eventually happen. --Trovatore (talk) 21:59, 20 January 2018 (UTC)

I was looking ahead to a possible further slowing in the axial rotation (not that I'm predicting it -- we just don't know). If leap seconds are abandoned then the alternative is an eventual leap hour that I mentioned above. This would easily be implemented by those countries who have summer time or daylight saving time. We seldom notice that the sun is not exactly overhead when we expect it to be, but eventually an adjustment might be needed to avoid hot sun at midnight. I suppose, by the time it is needed, we might have the technology to speed up the rotation of the earth to match atomic time. Dbfirs 08:51, 21 January 2018 (UTC)

I'd recommend the original poster to read about the Sothic year and Analemma. --93.136.126.95 (talk) 19:19, 21 January 2018 (UTC)

January 21

TGV

Were there any cases when a TGV train had to stop on a steep grade for some reason (the steepest grade on the Paris-Marseilles line is a whoppin' 3.5%!) and then couldn't get moving again unassisted? Or is the TGV powerful enough that this cannot happen? 2601:646:8E01:7E0B:C81D:59C2:9A63:53DF (talk) 07:00, 21 January 2018 (UTC)

They can reach 300 kph and electric motors have high torque from 0rpm, they probably could start on a grade. Sagittarian Milky Way (talk) 08:46, 21 January 2018 (UTC)

• It's an electric loco, not a diesel-electric (or turbine-electric). So the limit is almost always the torque available from the traction motors, not the total power of the prime mover - for a TGV at least. The TGV isn't designed for slow speed haulage, but it does have sufficient surplus, and at low speeds, to be able to do this. Also the Sud-Est sets have 12 powered axles per set, not just 8, as there's a powered bogie on the adjoining passenger carriage, not just the power cars.

I don't know what you mean by "a whoppin' 3.5%", but for railways that's (1 in 28) very steep for any main line.

This also brings in the issue of rated speed, the lowest speed from which full power is usable - usually limited by the torque capacity at low speeds. Diesel-electrics have often been restricted here (as your question implies - railway traction motors do not have particularly high torque and their power rating is severely restricted at low speeds.). Diesel-hydraulics have better ability to use their power as low speed torque. Andy Dingley (talk) 10:49, 21 January 2018 (UTC)

Since we're talking about the original line, let's look at the SNCF TGV Sud-Est trainsets. The spec sheet linked from that article gives the mass of the trainset as 385 t. Multiplying by 9.80665 m/s², its weight is 3775 kN, and 3.5% of that is 132 kN. The force/speed graphs at the bottom of page 3 show a force of 210 kN available at low speed: more than enough to get moving on a 3.5% grade, provided only that the wheels do not slip. --70.29.13.251 (talk) 20:13, 21 January 2018 (UTC)

So, the TGV can't get stuck on a hill? Thanks! 2601:646:8E01:7E0B:0:0:0:64DA (talk) 07:38, 22 January 2018 (UTC)

Compare this with the Eurotunnel Class 9 locomotive’s design specification to be able to start a shuttle train on a 1 in 160 (0.625%) gradient. 82.38.221.49 (talk) 10:30, 22 January 2018 (UTC)

• The main issue here is that the TGV is a railcar set, not a train-hauling locomotive, and a fast railcar at that. It simply weighs less than a heavy freight train, and it's also (because of the need for speed) powerful. Two other potential limits would be low-speed torque from the traction motors, and also adhesion limits. 3.5% is very steep in railway terms, but even so, the numbers for the TGV sets supports it being able to make a start on such an incline.

Plenty of freight trains would have difficulty in starting on such an incline, or may require banking assistance. Andy Dingley (talk) 17:28, 22 January 2018 (UTC)

What is the source of this "chapter 43" that found in a lot of sites on the internet?

I've got this document about "Antihyperlipidemic Drugs" which is "chapter 43". It is found in a lot of sites (such here), but the issue is that as much as I looked for the name of the book that it came from, I couldn't find it. What is the name of the book that it was taken from? 2A02:ED0:6F4E:6D00:F198:54F3:E7C4:F74B (talk) 15:34, 21 January 2018 (UTC)

It is:

Roach, Sally S. (2004). Introductory Clinical Pharmacology (7th ed.). Lippincott Williams & Wilkins. ISBN 978-0006262367.

Or possibly some other edition or format. DMacks (talk) 15:43, 21 January 2018 (UTC)

Indeed, it is accurately this book! Thank you. 2A02:ED0:6F4E:6D00:EA:29A2:D26A:5986 (talk) 01:04, 22 January 2018 (UTC)

Any spaceship prototype based on capturing dust and using it as propulsor?

Could a spaceship be based on the capture of matter found in outer space - like dust and asteroids - and posterior use a propulsor? As least, could a satellite use this matter to correct its trajectory? --Hofhof (talk) 22:44, 21 January 2018 (UTC)

Like a Bussard ramjet? Sagittarian Milky Way (talk) 23:55, 21 January 2018 (UTC)

I think OP is proposing to use dust as reaction mass, not as fuel. —Tamfang (talk) 08:51, 22 January 2018 (UTC)

You mean like a Ram Augmented Interstellar Rocket? (Mentioned in the above article.) Nil Einne (talk) 14:54, 22 January 2018 (UTC)

All of these Bussard based designs are for interstellar travel, so they're very theoretical, no prototypes. ApLundell (talk) 16:00, 22 January 2018 (UTC)

…could a satellite use this matter to correct its trajectory? You can't cheat physics. Conservation of momentum dictates that if the satellite hits something else to "scoop it up", no matter how tiny, it's going to lose momentum. Colliding with matter will slow down the craft, not speed it up. Even if you later eject the material, you're never going to get back more than the momentum you lost, and in practice you'll always get less because no real system is perfect with zero energy losses. The aforementioned Bussard ramjet is based on scooping up hydrogen and then fusing it to harvest the nuclear potential energy. Solar sails are more promising for non-rocket spacecraft propulsion, as you get essentially "free" energy if you're close enough to a star, and in addition you can use lasers to transfer more energy to the craft, beating the tyranny of the rocket equation. --47.157.122.192 (talk) 10:38, 23 January 2018 (UTC)

No, you won't lose momentum if you eject the scooped particle at a higher speed that it hits. — Preceding unsigned comment added by 31.4.136.130 (talk) 11:36, 23 January 2018 (UTC)

47.157, That is a misapplication of the conservation of momentum.

Momentum is conserved because the vectors are in opposing directions. (ie: You eject the dust particle at fantastic speed 'backwards', and your craft accelerates 'forwards'. Add those vectors up and you get zero.)

So long as you eject the particle faster than it was going when you first encountered it, the particle will have a net 'backwards' increase in momentum, therefore your craft will have a net 'forwards' increase in momentum.

ApLundell (talk) 16:48, 23 January 2018 (UTC)

But don't you need to expend energy to accelerate the particle out the back? That has to come from somewhere. And if you're carrying some kind of propulsion mechanism that ejects stuff, well, just use an ion thruster. I guess harvesting dust to use as propellant might be an option for some spaceship intended to operate indefinitely, since even an ion thruster will use up its propellant eventually. --47.157.122.192 (talk) 02:24, 24 January 2018 (UTC)

Yes, you would still need energy. (Perhaps from a nuclear reactor.) But using a Bussard collector would cut down on propellant needed, which for an interstellar journey might be non-trivial, even if you're using an ion thruster. ApLundell (talk) 17:13, 24 January 2018 (UTC)

I was thinking the description reminded me vaguely of a magnetohydrodynamic drive on a submarine, which acts on the water it is moving through/around. That article actually talks about using them on spacecraft, but Variable Specific Impulse Magnetoplasma Rocket and magnetoplasmadynamic thruster both seem to be about things that carry their own propellant rather than trying to do something to a handful of particles in empty space. I know nothing about this, just throwing out some terms for comparison. Wnt (talk) 23:48, 24 January 2018 (UTC)

January 22

Pyrogens as alternatives to DNP for weight loss?

People in the past took a chemical called dinitrophenol to raise basal metabolism but it has a narrow therapeutic index and a propensity to cause cataracts, particularly in women. Pyrogens are a type of chemical which includes some proteins made by immune cells which raise body temperature to fight an infection. Could small amounts of a suitable pyrogen have a similar effect to DNP? Would the therepeutic index be just as narrow and dangerous as DNP? --129.215.47.59 (talk) 14:49, 22 January 2018 (UTC)

Leukocytic pyrogen is studied in relation to metabolism as well as many other health subjects, such as fever reduction and muscle injuries. 209.149.113.5 (talk) 15:14, 22 January 2018 (UTC)

The history of weight loss drugs is marked by the widespread use of one compound after another that turn out to be killers. See [8]. Even herbal supplements not covered in that publication turn out to be killers, like Ephedra. I can't think of any other area of medicine where a new drug - even one asserted to be safe by government agencies - should be viewed with more trepidation. With that warning out of the way, I should note it is not hard to find people claiming to sell pyrogens for weight loss. [9] There are endogenous cytokines like cachectin (i.e. TNF-alpha) that cause severe weight loss (cachexia). [10] But then again obese people produce lots of TNF-alpha and it is more often blamed for diseases associated with "low-grade inflammation" [11] than cheered on as an effective means of weight loss. Wnt (talk) 16:36, 22 January 2018 (UTC)

Dyson sphere

Hi. I have read the article and still have a question. Why is it necessary to collect the star's energy from artificial objects orbiting it? A planet is an object orbiting the star, why not collect the sun's energy directly from collection devices on the planet instead of building them in space? I would like to understand why a dyson sphere/ring would be an advantage, how collected energy gets transmitted back to the planet, and why that's more efficient than collecting it when it arrives at the planet instead. Ta. 70.67.222.124 (talk) 17:10, 22 January 2018 (UTC)

Assuming that more energy is required than can be collected from the star from a planet's surface, a larger surface area could allow more collection. Enclosing the star, partially or completely, would increase this surface area and even prevent radiations from leaking out, permitting even better harvest. The hypothesis is that such energy quantities could be useful for particular advanced future technologies (perhaps including time-space bending), interplanetary civilizations and industries, etc. —PaleoNeonate – 17:23, 22 January 2018 (UTC)

(edit conflict) Of course you can collect some of a star's energy from a planet's surface, just like we already do with solar panels on Earth. However, only a small part of the energy/light that a star emits strikes the surface of planets and other natural orbiting objects. Most of a star's light escapes into deep space simply because there's nothing that stops it. The idea of a Dyson sphere is surrounding a star, so that little to nothing of the star's usable energy escapes.

As to how energy can be transmitted from collection device back to a planet, there are a number of options, e.g. lasers that are directed at the planet or storing the energy in fuel to transport back to the planet. - Lindert (talk) 17:31, 22 January 2018 (UTC)

"I know - lets build a device to collect the entire power output of the sun, and then turn it into lasers and fire it at our home planet! What could possibly go wrong?" Iapetus (talk) 17:29, 23 January 2018 (UTC)

Good point, but it doesn't really matter how you transport the energy. People on a single planet simply won't be able to handle all the heat generated by using so much energy. So the Dyson sphere only makes sense if there's a considerable amount of space colonization/exploration. - Lindert (talk) 17:51, 23 January 2018 (UTC)

(Whoops -- this is an answer to why it should be a complete sphere ... which wasn't the question. But I hate to delete my fine answer!) I've never read the original thesis, but I would assume the shell theorem is involved. A closed sphere will exert no net gravitational pull on the star; hence the star will exert no net gravitational pull on it. If it can be set up where the radiation pressure and gravity equal one another it might not even need much compressive or tensile strength. But if there is a hole, some pattern of orbiting is required, and things get (at least) more complicated to arrange with ultra-strong elements or moving parts or something. Wnt (talk) 17:40, 22 January 2018 (UTC)

A Dyson sphere is built presuming all the planet is already rigged for solar. It also often comes with an assumption that some kind of actual habitat with people living on it might actually extend all the way around the star, with the solar panels powering their local needs, or beaming the energy to a range of smaller settlements possibly in orbit. Wnt (talk) 17:46, 22 January 2018 (UTC)

The Earth intercepts solar power over an effective surface of about $A=\pi r^{2}.$, where r= about 3963 mi. The area of a sphere at the earth's orbital radius of 1 AU= 9.2956×10⁷ mi, is $A=4\pi r^{2}.$. So if you covered the earth with solar collectors, you could capture about (1.55×10⁷)/(3.43×10¹⁶) of the total energy that reached earth's orbital distance from the sun. That's about one part in 500,000,000, or 500 parts per billion. If your civilization needs more solar power, you need to go beyond Earth. -Arch dude (talk) 22:30, 22 January 2018 (UTC)

2 ppb. Sagittarian Milky Way (talk) 05:18, 23 January 2018 (UTC)

And I get a 1 AU Dyson sphere area of more than you for 1/2 ppb, not 2 ppb. Sagittarian Milky Way (talk) 05:28, 23 January 2018 (UTC)

Keep in mind that this is a thought experiment at an era where creating the structure is far beyond our capability. 10,000 years ago, imagine cavemen thinking about how to grow trees inside complex cave structures so they would always have firewood. They understand campfires, caves and wood as fuel. With the benefit of hindsight, campfires, trees and caves are no longer our primary habitat. Nor would a 10,000 year old plan to seek out advanced civilizations by looking for signs of giant caves with underground arboretums powered by large campfires be particularly insightful. Dyson spheres are an entertaining thought experiment limited by our current understanding. The assumption is that a civilization may eventually need all of a stars energy output and the thought experiment is how to contain it without simply appearing as a blackbody radiator as we currently do. --DHeyward (talk) 03:32, 23 January 2018 (UTC)

Exactly. And the concept of a "whole star energy budget" as described by Dyson is a variation on the theme of the Kardashev scale: it's a thought experiment that models major technology levels by comparing the energy budget of a society to different natural scales. A small and primitive society increases its energy production until it captures all the energy of its entire home-planet; to get any more, it must do something dramatically different. For a long time, there can be no progress (measured by growth in energy budget) until some major breakthrough makes off-planet growth practical. Presumably, the society and its energy use grows steadily, until the next big milestone - capture of the entire energy of the local star. Then, for a long time, there can be no further progress... and so on. This entire model of life in the universe is a thought-experiment; the Dyson sphere is a specific detail on the theme.

Obviously, this line of reasoning, subject to literary license, is like a great field of wheat: we have the potential to thresh a kernel of scientific insight only if we can discard a great deal of silly scientific-fiction chaff; hence we can mill the science into flour to create space-dough.

The famous paper was published in Science in 1960, and it met the bar for peer-review, and it was lauded by many respectable experts. Freeman Dyson did not ever, in his paper, discuss space-dough; but some twenty years later, he did write about space chickens and space eggs.

That original paper is the optimist's version of SETI. Quoting Dyson: "The material factors which ultimately limit the expansion of a technically advanced species are the supply of matter and the supply of energy." In other words, we pesky Earthlings can - in principal - keep growing and progressing and evolving until we eat every single molecule of matter on this Earth, drink every single watt of fresh-squeezed solar power, and distill every last drop of stored fermented energy! By the end of it, we Earthlings surely won't look like mammals! And then, we either extinguish, or we find a way to move off-world - to eat and drink every atom and ion and watt produced in the gravitational potential energy well of the local star, perhaps becoming some kind of space-jellyfish. ... with apologies: "I do not argue that this is what will happen in our system; I only say that this is what may have happened in other systems."

The pessimist's version of SETI, largely attributable to Frank Drake's work during that very same era, proposes a different limit to the ultimate expansion of a technically advanced species: as indicated on the great equation emblazoned on the wall at the entry to the SETI Institute, the scale factor L describes the longevity of an intelligent species. Intelligent species seem prone to self-annihilation; it hardly takes a measurable fraction of a Scale I energy budget to destroy intelligent life on a single planet, and I wake up each morning surprised we've made it through another orbit-fraction. This is one of the most probable resolutions to the so-called Fermi paradox.

I met Frank Drake this summer while I was stationed at SETI; and I had the opportunity to ask his opinion on our prospects; but all he wanted to talk about was the proliferation, diversity, and beauty of orchids on planet Earth. I had to acquiesce - of course, as difficult as it is for a self-locomotive mammal-brain to recognize, truly intelligent life is almost certainly autotrophic.

Nimur (talk) 06:04, 23 January 2018 (UTC)

• Without having seen the original paper, I'll go out on a limb and opine that what Dyson had in mind was not "if we build a sphere, we can capture all the sunlight" but rather that, as a civilization grows, it will seek to capture more and more sunlight, with the result (not a goal) that its sun is eventually hidden. —Tamfang (talk) 03:48, 24 January 2018 (UTC)

Thank you all for the thoughtful answers; this has cleared up a lot. You all helped, but Lindert especially got to the nub of my confusion. I've added some text to the article, including the crucial link to "thought experiment". 70.67.222.124 (talk) 16:09, 24 January 2018 (UTC)

Human head hair - changes from child to adult.

I have noticed that human head hair tends to darken as the person gets older, and that curly hair tends to straighten. (This is in people of European descent). What causes this? DuncanHill (talk) 19:44, 22 January 2018 (UTC)

You can look at Human_hair_color#Aging_or_achromotrichia. Ruslik_Zero 20:34, 22 January 2018 (UTC)

(edit conflict) Some information at Human hair color#Aging or achromotrichia which says "This is caused by genes being turned off and on during early childhood and puberty". This is referenced to Ask a Geneticist: Why does the hair color of children often change color as they grow older? (2010) by Dr. Barry Starr from Stanford University.

I also found an article about The HIrisPlex System for Simultaneous Prediction of Hair and Eye Colour from DNA (2013). In Section 3.3 Age-dependent hair colour changes and consequences for hair colour prediction the authors say: "Age-dependent changes in hair colour are evident from anecdotal knowledge. The most often observed age-dependent hair colour changes occurs from light blond during childhood towards dark blond/light brown as an adult, but can also occur from light brown to dark brown/almost black. Suggestions of hormonal changes during adolescence have been advocated as a possible explanation, but the molecular basis are yet to be unveiled". Alansplodge (talk) 20:36, 22 January 2018 (UTC)

Thank you, anything about curls? DuncanHill (talk) 00:09, 23 January 2018 (UTC)

Why does hair curl with age? says: "Dr. Barry Starr, a Stanford University geneticist thinks (according to an article on NPR.org) that most people’s hair doesn’t change from straight to curly. He doesn’t know why some do have this change and is skeptical that we will ever know! Scientists do know that curly hair follicles have a different shape than straight hair follicles. Therefore, according to Dr. Paradi Mirmirani (dermatologist), if your hair is changing, the follicles must be changing. She thinks it is related to hormones. Dr Val Randall (endocrinologist at the University of Bradford in England – according to NPR) also believes it is hormone related but says there is no evidence to prove it – and she is doing research on hormones and hair. She also claims it doesn’t happen very often!" Alansplodge (talk) 16:02, 23 January 2018 (UTC)

My observation is that curly haired children tend to grow into straight haired adults, the opposite of the agingbodies.com question. DuncanHill (talk) 16:30, 23 January 2018 (UTC)

The NPR ref does mention children although also with straight hair changing to curly. It also mentions people (well at least one, the other I'm unsure) who have had hair changing back and forth. It also mentions there is a a fair degree of funding for research into trying to change hair shape for cosmetic reasons which makes me think any common childhood changes would have been studied but I couldn't find anything from a quick look earlier. (I also would have expected them to be mentioned in the NPR ref but easily possible for it to be missed I guess.) Nil Einne (talk) 02:36, 24 January 2018 (UTC)

Looking a bit more I found [12] which also talks about hair changing from straight to curly when people were teens. It does talk a bit about hormonal changes in general (not specifically relating to childhood). This not very good source [13] suggest hair gets thicker during childhood which can lead to straight hair becoming curly. I found a case report on a single African-American teen who's hair changed shape after treatment for hair loss due to alopecia areata [14]. Anyway I mostly mention it because the new hair was straight which is said to be similar to the hair during early childhood, while the hair which wasn't lost was curly, implying his hair changed from straight to curly during childhood. Nil Einne (talk) 12:17, 24 January 2018 (UTC)

January 23

What substance is responsible for a metallic taste/smell?

What substance is responsible for the taste/smell that people describe as "metallic"? (The smell I'm talking about is what you get when you have a stainless steel pot on a stove that has boiled dry.) --134.242.92.97 (talk) 00:01, 23 January 2018 (UTC)

Sometimes the metal taste is from, well, metal. See here and, just for the cool link alone, also lasagna cell. Sometimes the metal taste is because of a medical condition. See here and also at metallic taste, but it seems like you're referring to the former rather than the latter. Matt Deres (talk) 02:32, 23 January 2018 (UTC)

The smell may be trans-4,5-Epoxy-(E)-2-decenal or Oct-1-en-3-one (cause by iron in contact with skin). The smell of iron dissolving in acid is due to methylphosphine and dimethylphosphine which may happen if you boil a food dry. You can also read A 'metallic' smell is just body odour or https://chemistry.stackexchange.com/questions/7916/why-can-we-smell-copper to see this explained more. Graeme Bartlett (talk) 11:42, 23 January 2018 (UTC)

Metallic taste independent of eating anything can also be caused by higher radioactive exposure. --Hans Haase (有问题吗) 18:42, 24 January 2018 (UTC)

Blue animals

When talking about animal skin, "blue" usually means blue-gray in color. Why is it so rare for animals to be the fully saturated blue?? Georgia guy (talk) 22:58, 23 January 2018 (UTC)

It's not just a rare case of animal coloration, but when it happens it usually happens by structural coloration rather than normal types of pigmentation. I don't know why it's rare or why it's not pigmentation, but those are some lead articles on the topic that could be expanded if you find more explanation. DMacks (talk) 23:04, 23 January 2018 (UTC)

"It's not easy bein' ... blue"

Btw, there is a c:Category: Blue animals. This NPR article discusses the question, but the bottom line as to why, is "still a mystery".

• Rae Ellen Bichell (November 12, 2014). "How Animals Hacked The Rainbow And Got Stumped On Blue". NPR.org.

—107.15.152.93 (talk) 00:19, 24 January 2018 (UTC)

There doesn't have to be a "reason", really. We humans like to look for teleology in everything, but evolution is undirected. It could simply be that the random walk of evolution on Earth didn't "come up with" blue coloration in animals often. Not that there's anything wrong with asking the question, of course. --47.157.122.192 (talk) 02:33, 24 January 2018 (UTC)

I don't think "a reason" implies teleology. A reason isn't the same as intention or purpose. Arguably everything (barring some truly random things like individual acts of nuclear decay) happens for a reason. Even if animal coloration was initially random and happened not to be blue, that then means that anything that subsequently became blue due to random mutation would stand out distinctly, and so be more likely to get eaten, and so fail to pass on its blue genes. That (to me at least) could be describes as a "reason", despite no direction being involved. Iapetus (talk) 11:13, 24 January 2018 (UTC)

The locus coeruleus is not really very blue either. Tyrian purple is a fair try by animals to produce a true blue pigment, but, well, it's purple, not blue. Indigo, closely related, was left to the plants, but is one of two pigments contained in Tyrian purple. Any animal ought to be able to evolve such a pigment since it is produced (via indican) from tryptophan. And yet ... they typically don't. You might see blue diaper syndrome or blue Fugates, though it may not be true blue enough. Curious... Wnt (talk) 03:04, 24 January 2018 (UTC)

look at how much of a typical color space is unambiguously some shade of blue, compared to a typical yellow

A few random comments. What is called "blue" in the English set of color names covers a huge swath of color-space, while "yellow" for example is extremely narrow, even though blue and yellow are generally considered opposites. This is misleading, because one can find shades of blue whose opposites are peach or brown.

Male Mandrill

Blue-lipped sea krait

Also, blue is very much like yellow, or a black and white pattern: either aposematic, warning of predators (think skunk, coral snake, blue-ringed octopus and kraits) or meant for sexual attraction (mandrill). Pure blues don't work very well for camouflage, so they are rare in general. Hence an animal is really going out of its way to produce a blue pigment, and again, most blue feathers produce the effect by iridescence, not pigmentation.

Variable ring patterns on mantles of the blue-ringed octopus, Hapalochlaena lunulata

μηδείς (talk) 03:54, 24 January 2018 (UTC)

That's not peach colour. It's just the colour you see when you look at a peach. A marketable peach, anyway. InedibleHulk (talk) 01:34, January 25, 2018 (UTC)

I should add that Larry Niven's Beowulf's Children, sequel to Legacy of Heorot, is a hard-science fiction novel based on several different ecological concepts in the colonization of a biologically highly advanced world (think earth w/o the KT event) where the most intelligent indigenous creature is an amphibian that as an adult eats its young (based on a recently described African frog tht lives off the tadpoles that eat the algae in its pond) and key species, symbiosis, ecological degradation, and the climactic discover of native aposematism, which saves the colony. μηδείς (talk) 07:23, 24 January 2018 (UTC)

This is speculation on my part, which someone might be able to refute or corroborate with, like, actual references, but is it not the case that blue chemicals and substances tend more than those of other colours to be poisonous to at least terrestrial metabolisms? {The poster formerly known as 87.81.230.195} 94.0.128.132 (talk) 01:13, 25 January 2018 (UTC)

My understanding is that blue pigments are not so much poisonous, as metabolically expensive. Keep in mind that the red end of the spectrum is low energy, so absorbing and emitting red is not very costly or damaging. But blue light is much more energetic, so it causes more damge, and re-emitting it is also costly as a matter of upkeep. (That is, things that reflect blue bleach easily under a yellow sun.) Also, the sun emits "white light" but it is white to us because it fully saturates our capacity across the visual spectrum. Nevertheless, yellow is more brilliant, given the sun's light is brightest in the yellow spectrum.

There's also the fact that red tends to look black rather quickly as one descends deeper in the see than blue does. Given all animal phyla I am aware of originated in the sea, a tendency toward blue for showiness at shallow depths (krait & octopus) implies we are incentivized by the color of our star Sol to produce blue only when the investment is worth the relative cost. μηδείς (talk) 03:23, 25 January 2018 (UTC)

The Sun actually emits most strongly in green. We don't perceive this because our photoreceptors are more sensitive to other wavelengths of light, and blue light is scattered by the atmosphere, so the Sun appears to have a yellow tint on a clear day. This, of course, also means that most plants reflect away the largest part of sunlight; the reason why is another little evolutionary puzzle. --47.157.122.192 (talk) 20:22, 25 January 2018 (UTC)

January 24

Could neutrinos be used practically for cooling?

I was looking at the Dyson sphere thread above and musing on other ways heat might be radiated, when I recalled vaguely the Urca process for cooling neutron stars via the emission of neutrinos. The cosmic neutrino background is at 2K, but it is very sparse - at best 1 million per cubic centimeter - so that's no use I think. [15] But the same paper suggests 0.2 eV is the upper limit of neutrino mass, so could you just make a bunch of neutrinos and antineutrinos from thin air, then use them to carry away heat energy in their momentum? If you knew how, I mean. Wnt (talk) 02:53, 24 January 2018 (UTC)

"If you knew how". There's the rub, innit? If you knew how to do magic, you could just cast a spell...--Jayron32 03:58, 24 January 2018 (UTC)

Well, 99.99% of the nifty things we want to do, physicists say it's impossible, you're nuts for trying, if you made it work it's a scam. So saying we don't know how to do it is like saying it's going to be in the supermarket in a couple of decades. I have no idea if [16] is useful for getting at how to do it or not. Wnt (talk) 08:44, 24 January 2018 (UTC)

The real trick is knowing which of the millions of possible lines of inquiry are likely to produce useful results. I can wish to do any of a number of fantastical things. I don't have time to test an infinite number of fantastical things. I need to pick ones that I expect to do something useful. --Jayron32 14:53, 24 January 2018 (UTC)

Taking a first stab at this, the Boltzmann constant tells me that there is 0.013 eV in each of three degrees of freedom at room temperature for about 0.05 eV of cooling per neutrino pair created. Our articles on neutrino mass and neutrino helpfully omit all guesstimates of neutrino mass except that the three flavors should add up to less than 0.120 eV, so the most they should weigh is 0.04 eV. That means that you should be able to get at least 1.2 units of cooling for every 1 unit of energy spent neutrino-making ... if your magic wand is perfectly efficient. But looking for guesstimates online I find this illustration from [17] indicating that with either possible configuration of neutrino masses there ought to be something with a mass^2 = 7.6E-5 eV^2 or 0.0087 eV per neutrino, a ratio of about 6 to 1. Which is ... cool. I mean, it seems like if you could make enough neutrinos and do enough cooling you could use this as a cold reservoir for a heat engine and have some kind of ridiculous dystopian "global cooling" problem from the rampant abuse of energy technology. ;) Wnt (talk) 14:32, 24 January 2018 (UTC)

The coupling of the matter in the system to the neutrinos must be strong enough. A lesson from history is the discussion in the early days of quantum mechanics about the photon mass. A wrong argument put forward was that the photon must be exactly massless, that it couldn't have even an astronomically small mass, because a massive photon would have a longitudinal polarization, so black bodies would also radiate photons with longitudinal polarization, therefore the Stefan–Boltzmann constant would have to be be 3/2 of the known value, and that's then obviously false. But this reasoning is flawed because the coupling of the longitudinal component to matter tends to zero in the limit of zero photon mass. So, matter becomes transparent to longitudinal photons in that limit. Count Iblis (talk) 15:06, 24 January 2018 (UTC)

@Count Iblis: I was thinking the invention of a small neutrino detector suggested better coupling was possible than commonly believed. This gives some comments about it but I don't pretend to understand, and I admit, it doesn't sound like a whole hell of a lot of coupling. But I find it uncommonly easy to believe that there is a lot of secret neutrino physics, since you can (possibly) use them to track nuclear submarines and other nukes, and AFAIK if you could do enough pair production, you could perhaps aim your beam at those nukes and make them go off spontaneously, not to mention secret comm networks and the for practical purposes all but perpetual motion machines described above. I am suspicious that the lack of a nuclear weapon(s) concealed in the collapsing WTC towers gives a hint that smuggling nukes into a country is harder than people think, which in turn makes me think that powerful, high-res detectors have been available for a very long time, so I wonder if physicisits might be many decades behind the spooks... Wnt (talk) 01:01, 26 January 2018 (UTC)

What factors can we say are responsible for the lifespans of Homo (human) members increasing to 70 years, as seen in modern hunter-gatherers?

There’s a study on modern Homo (human) hunter-gatherers that states that most of them live to 70 years: http://www.anth.ucsb.edu/faculty/gurven/papers/GurvenKaplan2007pdr.pdf but I’m in doubt that members of the Homo genus have always lived this long. Members of the other genuses in the Hominidae family, which are Pan (chimpanzee), Gorilla (gorilla), and Pongo (orangutan), usually live 30-40 years. So the earliest Homo members must have originally lived 30-40 years as well (and probably looked like Pan members). But I’m curious what factors we can say are responsible for the lifespans of Homo members increasing to 70 years, as seen in modern hunter-gatherers. I’m not sure if cooking was a factor. MisterH2005 (talk) 04:47, 24 January 2018 (UTC)

The following study posits (regarding Homo lifespan):

We suggest that lower adult mortality, distinctively short interbirth intervals, and early weaning characteristic of modern humans are derived features resulting from cooperative breeding.

• Robson, Shannen L; Wood, Bernard (2008). "Hominin life history: reconstruction and evolution". Journal of Anatomy. 212 (4): 394–425. doi:10.1111/j.1469-7580.2008.00867.x. ISSN 0021-8782.

See: cooperative breeding —107.15.152.93 (talk) 06:20, 24 January 2018 (UTC)

You are also ignoring the difference between (average) maximum life span, and (average) life expectancy. Life span is the normal length of a life not shortened by violence or the action of another (disease or enemy/predator) organism. That has long been around 70, and is increasing as we improve our medical technology. There is a trade-off involved here. 70 year-old grandparents make great child caregivers and stores of wisdom.

But certain other genes like ones for large breasts may increase fecundity and child survival, while killing the mother at 40 of breast cancer. Evolution tends to select for those genes which have the longest term benefit toward surviving children. In apes, wouded forty-year old males have little to offer, while medicine-men grandfathers among humans offer both wisdom and prestige.

The second issue is average life expectancy. A couple only needs 2.X (X being a small number to deal with non-breeding offspring) to replace it. A couple might have 11 children, and the wife die at forty in childbirth. But if she has a 20 year-old daughter who can help raise two other children to maturity, then although the father and two children might live to 70, the mother to 40, and 10 children to age 1, you have 260 years/13 people = 20 year average life expectancy, but a stable population. μηδείς (talk) 03:07, 25 January 2018 (UTC)

The question was addressed by Leslie Aiello in Evolution of Human Life History Patterns, eighth of nine lectures in the CARTA symposium Origins of Genus Homo held on Feb 5th 2016: see here. Each of the nine lectures lasts no more than 25 minutes (click on the little filmstrip symbol by each item to see it on YouTube), and I've linked the whole web page since the other eight lectures may be of some relevance and interest: I recommend watching all of them in order.

There are of course a number of other symposia on the CARTA website, some of which may also contain material of interest – search via the SYMPOSIA or RESOURCES drop-down menus. {The poster formerly known as 87.81.230.185} 94.0.128.132 (talk) 06:42, 25 January 2018 (UTC)

Reducing infant mortality is largely (and arguably only) major contribution in life expectancy at birth, followed by childhood deaths. This is evident in comparisons of third world and first world population graphs by age graphs. Nations with high infant/child deaths have a 1/x type graph of population by age, first world have a shifted gaussian. The telling statistic is actuarial table that estimate average lifetime at different ages. A 60 y/o person has a median remaining years of say 20 years more. An 80 y/o has a median of 5, at 100 it's about 1. At 110 it's about 6 months. The telling statistic is that maximum lifespan and actuarial tables beyond 60 years old have really not improved much. Certainly not as much as the lifetime from birth which gets a massive bump from vaccines, antibiotics and childbirth survival rates. --DHeyward (talk) 11:53, 25 January 2018 (UTC)

1. Diet - no chronic diseases such as stroke, congestive heart failure, diabetes, hypertension

2. No deadly infectious diseases - most are caused by domesticating animals

3. Isolation - limited contact with outsiders who spread deadly infectious diseases such as smallpox, gonorrhea and syphilis

4. Active - no obesity

5. Strong immune systems - exposed to environmental bacteria

6. Plenty of food (no famine) because of high infant mortality limits population explosions

7. No famine due to not relying on one variety of crop

8. No modern pollutants - no smog, engine exhaust, modern dyes, radioactive clouds from atomic bombs and reactor meltdowns

9. Sun exposure - synthesis of Vitamin D in the skin

The Kitavan islanders studied in 1989 are stone age tropical farmers who hunt fish, gather fruit and grow root staples. The gardens are infertile and only yield one crop before a new garden needs to be slash and burned. The men appear to be lazy as the diet only has 10% protein. The men fish and prepare the gardens for the women who also gather fruit.

The Hadza Bushmen of Tanzania are nomadic hunter gatherers that live in family groups of around 30 people

The Maasai of Kenya and Tanzania are stone age nomadic pastoralists who neither hunt nor gather. They eat milk, meat, blood and no vegetables. They are exposed to famine if their cattle die from an infectious disease.
Sleigh (talk) 12:41, 25 January 2018 (UTC)

I think everyone is drifting away from the OP's actual query. MisterH2005 isn't asking about the life-span contrasts between (modern) hunter gatherers and other modern humans, but about the evolved contrasts between the genus Homo (for whom modern hunter-gatherers merely provide a conveniently studyable proxy) and earlier non-Homo Hominidae – or so I read it. Paleoanthropological research (including that which I linked above) suggests that this increased lifespan evolved along with other distinctly Homo traits as a synergistic package (if I may coin a term). {The poster formerly known as 87.81.230.195} 94.0.128.132 (talk) 08:46, 26 January 2018 (UTC)

Oxyanion naming confusion

Where did IUPAC publish its decision (mentioned in the bohrium article) to name bohrium oxyanions bohriates to avoid confusing them with borates? There would of course be some precedent for this insertion of -i-, since lutetiate (e.g. here) seems to be more frequent than lutetate (I imagine because it is not at all clear how the latter ought to be pronounced), but I'd like to see the original source for bohriate.

Also, this is unlikely to come up (since Ra forms a strongly basic oxide), but is there a way to distinguish between radium and radon oxyanions instead of having both be radates? Double sharp (talk) 09:57, 24 January 2018 (UTC)

I can find nothing that uses the word "Bohriates" outside of Wikipedia and mirrors. I would tag the statement and/or remove it pending the production of an actual source. --Jayron32 11:49, 24 January 2018 (UTC)

ON the second issue (this is pure speculation), radonates would work, as some elements take the whole name + ate to form oxyanion names (c.f. zincate, nickelate), though I haven't looked for IUPAC rules on that one. --Jayron32 11:54, 24 January 2018 (UTC)

On bohriates, that was what I was going to do, but Martyn Poliakoff does mention it on The Periodic Table of Videos: "There's still a question with this name – boron and bohrium – because what happens when you start having the salts of these? Because borate and bohrate: sounds just the same! Nobody hears the h when you say it. So it's been decided that the salts of bohrium will be called bohriates rather than bohrate so that people won't be confused." I've cited him on the article. The question though is where he got that information from: I hope this isn't yet another case of citogenesis. Double sharp (talk) 15:21, 24 January 2018 (UTC)

I love Poliakoff and Brady Haran's videos in general, but that sort of pop-science stuff isn't the greatest as a scholarly source, I think we need to search for something a bit more definitive. I'd tag that source as "dubious" given that the purpose and nature of the video (as sciency entertainment) isn't quite what we would expect as a source for a statement like this. --Jayron32 15:25, 24 January 2018 (UTC)

Also, just for the record, PubChem only has records of 12 Bohrium containing compounds: [18] and none of them have oxyanions of bohrium. Maybe it has never come up... --Jayron32 15:28, 24 January 2018 (UTC)

It certainly hasn't come up in experimental chemistry, but it does make it difficult to actually write the articles. I mean, I mention predictions (cited) in Bohrium#Predicted properties, and BhO⁻
₄ is mentioned as the most likely way Bh^VII would be stabilised (analogous to Mn, Tc, and Re); it is frustrating to have to dance around it by never mentioning the name because we're not sure what it ought to be. And similarly for Rn: in Radon#Chemical properties I mentioned the predicted Rn^VIII compound Ba₂RnO₆, and named it rather straightforwardly as barium perradate. Except that now I've realised that that's actually ambiguous. If I can't find a good answer for each of these cases here I will take away those names and write around them, but I continue to hope that IUPAC has come up with an official answer. ^_^ Double sharp (talk) 15:38, 24 January 2018 (UTC)

According to the IUPAC Red Book: bohrate, argonate, kryptonate, xenonate, radonate. Burzuchius (talk) 15:59, 24 January 2018 (UTC)

Well, there you go. --Jayron32 16:03, 24 January 2018 (UTC)

Thank you! It's against common usage for perxenates, but for the rest (since oxyanions of Ar, Kr, Rn, and Bh are undiscovered AFAIK) I will edit the Rn and Bh articles accordingly. Double sharp (talk) 01:58, 25 January 2018 (UTC)

Why does a washing machine take hours to do the laundry?

Why can't it be done in, say, 15 minutes? Count Iblis (talk) 15:07, 24 January 2018 (UTC)

My washing machine has cycles that last from 14-6 minutes for the wash, with a rinse and spin dry lasting about 10 minutes. My washing machine has no cycle that lasts as long as an hour, even if you do a maximum wash time allowed with a double rinse cycle. I have a fairly standard washing machine which is common in most western households (washing machine designs are fairly universal except for higher end, new fangled front loaders, or high efficincy machines. The standard washing machine design hasn't changed in about 50 years, with some minor cosmetic updates). Your premise is wrong.--Jayron32 15:12, 24 January 2018 (UTC)

Washing machines are nothing like universal, even in "the West". There are national variations between US vertical axis top loaders, Western European front loaders, Northern European horizontal axis top loaders and in Greece and Turkey there are still plenty of non-automatic twin tubs in use. Also their uses of water temperature, detergent and even (in some backward countries) universal bleaching vary a lot.

My own washer (modern LG, but nothing radical) will do a load in between 2 hours and 20 minutes, depending on whether that's a super-medical-clean boil wash for white linen or a "clean shirt now!" panic. Andy Dingley (talk) 15:40, 24 January 2018 (UTC)

Fair enough. Of all the washing machines that I, or any of my family, have owned and used (and I've probably used a dozen or so in my life) they are basically all identical. Point taken. I have stricken the false statements I made. The premise that "a washing machine takes hours" is, however, demonstratedly false: My washing machine takes between 15-25 minutes depending on the cycle. If Count Iblis wants to know why HIS washing machine takes hours, he would need one of us to come over his house and look at it. But many washing machines get the job done in 15 minutes. --Jayron32 15:58, 24 January 2018 (UTC)

But you're in the US. Last time I did laundry there, it was typical to take the laundry from the machine pretty wet, and then move it manually to either a spin drier or a tumble drier. Here in the UK I line dry stuff, other people tumble dry, and many (who aren't watching the energy consumption!) use combination machines which tumble dry automatically, within the same drum.

Also (which I should have noted) my machine weighs the load and adjusts run times accordingly. Andy Dingley (talk) 18:20, 24 January 2018 (UTC)

Our article suggests that top-loading machines (more common in the US) are faster, though less effective and efficient, than front-loading machines, common in the UK and Europe. See Washing_machine#Comparison. DuncanHill (talk) 20:00, 24 January 2018 (UTC)

Yeah as I noted below even for a top loader 15 minutes sounds like the time it would take for the wash or spin cycle in NZ or I think Australia. Even if you're able to wash and rinse the clothes with a full cycle in 15 minutes, I can't imagine you can magically get them as dry one with a 15 minute spin cycle in a top loader you may find in NZ or Australia which makes me think the clothes are probably a fair amount wetter. So they're either going to take longer to dry on the line, or your tumble dryer is going to be doing more work. Or you're spin drying them in a separate machine. Nil Einne (talk)

He never mentioned a clothes dryer. He only mentioned a washing machine. If he meant both washing and drying his clothes, he would have said so. That takes another 50-60 minutes to dry the clothes. I'm not sure a practical way to speed that up. I mean, one could just raise the temperature, but I want my clothes dried, not scorched. --Jayron32 13:42, 25 January 2018 (UTC)

Jayron, I think you are getting confused between a spin dryer and a tumble dryer. Nil Einne was commenting on the degree of dryness after spin drying. DuncanHill (talk) 13:45, 25 January 2018 (UTC)

Regardless, we're dicking about minutes here. The OP said it takes hours, as in at least 2, for him to wash his clothes. I can't even run my washing machine for as long as one hour, if I even wanted to. I'd have to run two cycles. A full cycle, including wash, rinse, and spin takes about 30 minutes, which leaves the clothes slightly damp. But hours seems outrageously long. --Jayron32 15:40, 25 January 2018 (UTC)

Two points - 1) Did you bother to read the comparison between top and front loading machines linked above? and 2) "hours" is colloquial English for "ages", "a long time", "longer than thought reasonable or necessary". And, as pointed out elsewhere in the thread, some programmes do take more than two hours. DuncanHill (talk) 15:57, 25 January 2018 (UTC)

Two points: You are right, and I am wrong. Everything you said is correct, and everything I said is wrong. I apologize for being so misleading. I will try to do better in the future. --Jayron32 16:06, 25 January 2018 (UTC)

I'm glad we got that cleared up! DuncanHill (talk) 21:10, 25 January 2018 (UTC)

BTW in case there still doubt, my main point was that I don't want to get into debate whether American machines get clothes as clean as NZ and Australians ones and whether they do it by eg using a much hotter wash or detergents which are nastier. But here where top loaders are still common, I'm fairly sure 10-15 minutes or more will be normal for the spin dry cycle of a top loader and it's hard to imagine the shorter US cycle will get clothes as dry. This implies as Andy said that clothes likely come out wetter. Whether this is a bad thing is again not a debate for the RD but it does seem to suggest a longer dry time whether line or tumble. The tumble dryer will likekly use more energy than the spinning. Alternatively you may use a separate machine for spinning only. P.S. There may also be differences in average size of loads, materials, etc which will affect spin time drying efficiency. Also I do agree multi hours isn't the norm for standard top loader cycles in NZ although they do tend to be longer than those quoted here for US washing machines. The Choice ref suggests maybe close to an hour. As I said below this seems more likely at least in part to do with front loaders which in many countries are not new fangled. Nil Einne (talk) 14:32, 26 January 2018 (UTC)

Also although I'm fairly sure this has nothing to do with the question, it's worth noting combination washing and tumble dryer machines are a thing as others have noted. These are still rare in NZ but my impression is they're getting more common in Malaysia where the climate and tradition of line drying even in apartments means stand alone tumble dryers are AFAIK very rare. These mean you just load clothes once and don't have to worry that much about when they finish unless you need them urgently. As I'm sure one of the linked wikipedia articles notes, if you include parts of Asia there is also the difference between the design if top loaders, impeller design for top loaders common there vs agitator common here and my impression is in the US too. I'm not saying this affects times. Nil Einne (talk) 15:13, 26 January 2018 (UTC)

(edit conflict) Machines obviously vary considerably. Here in the UK, my cheap front-loader takes nearly two hours, and that's without a pre-wash, and only a spin dry. It does have a quick wash option, but I seldom use it. Dbfirs 16:02, 25 January 2018 (UTC)

Per earlier comments, you need to be more specific on what you're measuring. For example, I have a fairly modern front-load washer. When I set it for a "normal wash", the timer suggests things will be done in 1:15 (or thereabouts, depending on weight), but I typically select "short wash" (we just don't get that dirty), which cuts the time in half and still includes final spin and tumble. Now if you're talking about the industrial jobs you see in laundromats, my experience - though dated - is that they sacrifice speed for durability and may take longer than equivalent-sized personal machines. That's just a (dated) personal observation, though. Matt Deres (talk) 17:20, 24 January 2018 (UTC)

The manual for my Zanussi automatic front-loading washing machine lists programme times from approx. 50 minutes for woollens, to approx. 147 minutes for the heavily soiled whites programme. In my experience these times are fairly typical of automatic machines in the UK. The manual notes that "actual times will vary depending on incoming water temperature and pressure". These times include spin, but not tumble (I have a separate machine for that). DuncanHill (talk) 19:52, 24 January 2018 (UTC)

To bring this back to a scientific angle, I suspect the ultimate answer has something to do with chemical kinetics and reaction rate constants. Insofar as we can simplify a complicated process, a washing machine can be described as a chemical reactor, in which we emplace fiber, dirt, detergent, and water, and use an agitator to encourage mixing and to accelerate mixing, and to physically dislodge particles. The goal is to chemically or physically separate dirt from fiber, by any means necessary.

To what extent can we quantitatively model the rate of chemical and physical action until a material is free of debris, dirt, and chemical contaminant? To what extent does a petri-dish model scale up to provide useful descriptions for a real-world washing-machine?

I know, for example, that autoclaves (professional cleaning machines that are used to sterilize medical and scientific materials) have carefully prescribed durations, pressures, settings, and so on: here's an example blog series on autoclave basics, including data such as exposure duration. Bear in mind that in those contexts, the goal is to kill microbacteria, not simply to dislodge dirt and contaminant - but the idea is that we can directly measure how many minutes are required to get something clean, and then we build a machine to automate that cycle-time using a mechanical process.

Nimur (talk) 19:24, 24 January 2018 (UTC)

On the subject of "how many minutes are required to get something clean", how is this affected by the type of soap or detergent selected? 86.169.56.163 (talk) 19:59, 24 January 2018 (UTC)

A lot more of it changes because of engineering, not the chemistry of the cleaning products.

For one thing, cleaning products have a short time to market. I can buy (tasty, tasty) Tide pods today, but my machine will still have a soap drawer designed around loose soap powder and I'm pouring liquids in there from a generation inbetween. I'm unlikely to change machine just because the consumables suggest so. It took a very long time before the majority of European machines in service could wash at the lower temperatures which newer detergents had permitted from the '90s.

Mechanical changes have changed the washing cycles. Water consumption in particular has dropped, encouraged by Europe's pretty fine-grained energy rating system. We've also seen a shift to single connection cold-fill machines (electric heat of less water, inside the machine) than the old approach of hot fill, as a gas-heated supply was considered to be cheaper (this is turn has even affected European domestic solar power designs - not much point in the difficult problem of solar heating truly hot water for laundry, if the detergent doesn't need it and the machine won't even use it). We now see a lot more use of low-volume continual pumping water systems which recirculate as sprays. More efficient rinsing also reduces the time and water volume needed to do it inefficiently (one area where horizontal axis really beats vertical axis). Andy Dingley (talk) 20:02, 24 January 2018 (UTC)

What in the world? Are you still having your womenfolk bang your shirts on rocks, Count Iblis? I usually just let the launderer do my laundry, since it comes back folded, mended, and unharmed at the same price I would pay in quarters; and I tip. The standard setting on my parents' and my sister's machine is 12 minutes, plus a drain/rinse/spin cycle, for a total of about 15-20 minutes depending on how long it takes to fill (a small wash is 1/5th the volume, and goes much quicker than the largest load.

There is a presoak cycle that adds either 10 or 30 minutes of soaking (with just enough agitation to distribute the detergent) which is followed by the normal run. But I almost never use that option. Even back in the 80's, commercial washers only took about 30 minutes, and they were monsters. The dryers often took two hours, so the trick was to do the jeans and towels separate from the lighter items. But an average hour-minimum cycle for a standard washer? μηδείς (talk) 02:52, 25 January 2018 (UTC)

As already noted, one big issue is probably the difference between the type of washing machine used. An hour or longer for a standard wash on a domestic front loader isn't exactly uncommon, and these washing machines are more common than top loaders in a number of countries and are definitely not "new fangled". As high efficiency top loaders often share some similarities in operation principle with front loaders, they are generally similar. This US source [19] notes the time difference so I don't think even the US has front loaders with such short cycle times. That said, 15-20 minutes for a normal full cycle even for a top loader seems fairly short to me, the responses here make me think this is a US thing. 15-20 minutes sounds more like the time for the wash or spin cycle. See e.g. this info from an Australian source with average times [20] Nil Einne (talk)

My answer was typed hours before it was posted, I didn't notice it didn't upload. That being said, my parent's machine is a top-loader and the was cycle is 12 minutes, with time added for a two filling and draining cycles, the time of which depends on the volume of water, and a two-minute rinse cycle. When I use their machine it is usually for the largest load, since I will be doing bedclothes and whatever clothes I have with me for the weekend/holiday. The full cycle runs about 20 minutes from start to finish.

My sister has a side loader. She and her husband are clean freaks (they all bathe twice a day at least, and three changes of clothing is normal) and they have an industrial strength machine that is in almost constant use, and it does have quite long cycles and will also heat the water already hot from the main. But that was all by choice, not due to a set limitation of the machine, and it will happily do a normal load without all the extras meant to sterilize ebola and vaporize bedbugs in about 20 minutes. With the outrageous money they spend on bathing, dishwashing, and laundry, they could go to Disney World every year. μηδείς (talk) 17:09, 25 January 2018 (UTC)

If I was the designer at a company that manufactures washing machines I would be looking at the size of the market; and what proportion of the likely customers are interested in a machine that can wash a load in 15 minutes, and whether they are willing to pay the premium cost associated with such a machine. I would be likely to conclude that potential customers are looking for a machine at a low cost; and doesn't damage the clothes. They are likely to see little or no advantage in a machine with a cycle time of 15 minutes compared with one that has a cycle time of 45 minutes or longer. The end result is that I wouldn't even bother recommending to the Board that the company adds a "15 minute" machine to its stable of products. Dolphin (t) 06:03, 25 January 2018 (UTC)

I should clarify when I said front loaders with such short cycle times, I mean a standard cycle time. I believe my front load does have some super quick cycle that is 15-20 minutes although I can't recall if it includes spin drying. Nil Einne (talk) 06:08, 25 January 2018 (UTC):

Yes, in the UK I've not seen a domestic top loading machine since the 1970s although I've used commercial ones on camp sites. The shortest cycle on our front loading washing machine is 30 minutes but that includes 10 mins for the spin cycle. The longest cycle is for cottons and is 3 hours 10 mins which includes a prewash, 90 degree wash and spin. I can't imagine what you would have to do to your cottons to require that long a wash - we normally only use the 30 min or 45 min cycles and an occasional seperate wash for 'delicates'. Back in the 50s and 60s my mother used to send the cotton bedding to the laundry every week but those type of laundries seem to have gone as automatic washing machines became popular. There are self service launderettes that also do a service wash but these seem to be disappearing too in most places. Ironing services are becoming more popular though my wife and I find that with modern fabrics and careful use of the tumble drier there is very little to iron anyway. It's strange how things are done so differently in different parts of the western world. However, I must take issue with the description above of an autoclave being a "professsional cleaning machine" - it isn't! An autoclave is basically a large pressure cooker used for sterilisation, and anything that goes in it that will be re-used has to be carefully washed before it goes in or the dirt will just get baked on. The length of the cycles it uses are worked out to ensure all the microorganisms are killed in the minimum amount of time - nothing to do with cleaning. Richerman (talk) 10:56, 25 January 2018 (UTC)

Unless you're planning on hanging your laundry, there really isn't much benefit to having a private washing machine complete its task in significantly less time than it takes the dryer to do its task. As the laundry-doer (and general lazy ass), I would still only make the trek downstairs once I'd figured the dryer was finished and the time savings on the washing would be worth little to me. YMMV, of course, but I think many people do all their laundry on a specific laundry day and would have broadly similar habits. Matt Deres (talk) 17:14, 25 January 2018 (UTC)

In the UK most people have the washing machine in the kitchen (or, if they have a large house, in an adjoining utility room), so there is no trekking down and up stairs involved. It's always struck me as rather odd the way Americans seem to put the washing machine in the most inconvenient location they can find. DuncanHill (talk) 21:08, 25 January 2018 (UTC)

Kirstie Allsopp might disagree Andy Dingley (talk) 22:12, 25 January 2018 (UTC)

Well, granted (though we Canadians also like to stick the laundry downstairs), but it's really the timing that's important. If it takes 15 minutes to wash clothes and 45 minutes to dry them, you're going to have problems running the laundry in series. The first load will only be one third done in the dryer when the next load of washing is done. Matt Deres (talk) 02:07, 26 January 2018 (UTC)

• North Americans place the upright spinning washer downstairs so that their screams of delight as they sit upon it as it vibrates do not annoy those in the dining or sitting room, or the bedrooms.

I had my mother run a full "extra large (volume)" wash at hot-from-the-main setting on my bedclothes (sheet, "wool" (synthetic) blanket and pillow cases (8)) with the blue towels from the guest bathroom I use today. She said it ran for 26 minutes, being: filling hot; agitation 12 minutes; spin/drain; second filling on cold-from-main (much quicker than hot); second agitation; final spin/drain.

This took all of 26 minutes. No wash would ever take longer. The "Woolen" (synthetic) blanket was hung in the sun and dry in 15 minutes. The remainder was placed in the front-loading drier, and done at the lowest temperature (basically, "above ambient") within 30 minutes.

Usually heavy items like towels, blankets, and jeans are hung to dry, while light cottons and gotchies and socks are dried on low temp, like delicates, for 30-50 minutes. This is not an issue, since two or three separate washes done by dark/red/light color can be dried together, so the different cycles are an issue of tactics, not shear stupid serial mechanics. My drying reds have never turned my whites pink.

I think you Brits are being cheated by both your appliance manufacturers, and your state utility companies with this sill front loading, don't bend over to dry separately do goody-good bullshitt. μηδείς (talk) 03:46, 26 January 2018 (UTC)

We have not had state utility companies for over 25 years. AndrewWTaylor (talk) 10:43, 26 January 2018 (UTC)

We never had them. We had the gas board, the electricity board and the water board. 92.19.172.194 (talk) 15:34, 26 January 2018 (UTC)

I think it's because Europeans care about using less water, energy and soap than Americans, since front loaders are much more efficient on this front. US top loaders might save time but our front loaders save us money and we tend to like that. Regards SoWhy 15:37, 26 January 2018 (UTC)

January 25

Super blue blood moons

There's to be a "super blue blood moon" on 31 January, due to a triple coincidence of a super moon, a blue moon, and a total lunar eclipse. I read that the last time this happened was "150 years ago". What was the exact date, and does this come around in any sort of regular pattern? When were the earlier incidences? -- Jack of Oz ^{[pleasantries]} 10:30, 25 January 2018 (UTC)

The article you linked says that "super moon" has no precise definition, so it is not possible to list earlier occurrences. --70.29.13.251 (talk) 10:53, 25 January 2018 (UTC)

Ok, so what was the event that occurred "150 years ago"? -- Jack of Oz ^{[pleasantries]} 11:08, 25 January 2018 (UTC)

Unfortunately, the c. 1868 incidents at List of 19th-century lunar eclipses don't have articles, and Category:2nd-millennium lunar eclipses has no articles about individual eclipses between 1573 and the 20th century. Nyttend (talk) 12:54, 25 January 2018 (UTC)

A "supermoon" is a full moon which is unusually close to Earth (i.e. near perigee). There is a full moon roughly every 29 1/2 days, the "anomalistic month" is 27d 13h, and the full moon "gains" on the perigee about 2 days per month. Thus supermoons happen about every fourteen months. "Blue moon" is a fluid term but the writer's attention appears to have been attracted by the fact that this year January and March have two full moons apiece and February has none. In the last 150 years at Greenwich this has happened in 1866, 1885, 1915, 1934, 1961 and 1999. It is theoretically possible for this to happen in a leap year - anyone interested might want to check the records and let us know when the last time was.

For the moon to be eclipsed it must be at or very near a "node". The full moon "gains" on the node about 2 1/3 days per month. It is to be noted that the above mentioned "blue" moons often recur at intervals of nineteen years. The nodes line up with the full moon every 18.6 years and about 70% of the time an eclipse will be repeated nineteen years later (because the moon has moved round to the opposite node). The "blue moons" in the above sense were eclipsed in January 1915, January 1934, March 1961 and January 1999. 86.169.56.163 (talk) 13:15, 25 January 2018 (UTC)

... and, of course, Jack and 86.169.56.163 are referring to an American blue moon, as in J. H. Pruett's 1946 misunderstanding of the 1937 Maine Farmers' Almanac. The last spectacular British blue moon was in 1950. Dbfirs 15:16, 25 January 2018 (UTC)

On that point, we say: The March 1946 issue of Sky & Telescope misinterpreted the traditional definition, which led to the modern colloquial misunderstanding that a blue moon is a second full moon in a single solar calendar month with no seasonal link (my highlight).

I would argue that that "misunderstanding" has become "the common understanding" of the term. The article is very informative and instructive, but I have to say I have only ever known the term to mean the second full moon in a calendar month. Words and expressions mean what they are now generally taken to mean, not what we are told they once meant. -- Jack of Oz ^{[pleasantries]} 20:37, 25 January 2018 (UTC)

The American usage must have spread to your continent long before it spread to northern England, because I've only recently become aware of the American meaning. The literal British meaning has been around since 1702 according to the OED, though I admit that I haven't personally known of it for quite that long. Dbfirs 22:32, 25 January 2018 (UTC)

Consecutive Full Moons obviously cannot be blue. The 1st moon of the 2nd month would have to be only a few days after the 2nd moon of the 1st month. But if a month is shorter than a moonth it might be Full Moon-free allowing blue moons 2 moonths apart (similar to how twin primes are 2 numbers apart because it's not possible for consecutive numbers to be prime) This is only possible in February (moonths are 29d 6h to 29d 20h long) so twin blue moons are only happen in January and March. I searched this database of blue moons less than a year apart, a database of lunar eclipses and a database of supermoons and found the last blood double blue supermoon (Gregorian) was January 30 or 31, 1646 in all time zones. That total lunar eclipse was farther than 2018. Even so, the January 31, 2018 moon isn't a supermoon by strict definitions so I searched till 481.5 AD and couldn't find a double blue blood supermoon closer than this 2018's (unless I missed something). Obviously (to astronomers) both blue moons can't be lunar eclipses because lunar eclipses cannot occur 2 moonths apart. Sagittarian Milky Way (talk) 03:28, 26 January 2018 (UTC)

Nobody ever said consecutive full moons are blue. If two consecutive full moons both fall in the same calendar month, the second one - not both of them - the second one is a blue moon. In January 2018, there was a full moon on 2 January, and another will come on 31 January. The one on 31 January is blue, the one on 2 January wasn't. -- Jack of Oz ^{[pleasantries]} 04:20, 26 January 2018 (UTC)

The point about the original meaning of "blue moon" is that it's the fourth in a season. The moons are named, three to a season, so when a fourth one comes along it doesn't have a name. 92.19.172.194 (talk) 15:50, 26 January 2018 (UTC)

Detecting an aortic aneurysm

From A study in scarlet:

"Then put your hand here," he said, with a smile, motioning with his manacled wrists towards his chest. I did so; and became at once conscious of an extraordinary throbbing and commotion which was going on inside. The walls of his chest seemed to thrill and quiver as a frail building would do inside when some powerful engine was at work. In the silence of the room I could hear a dull humming and buzzing noise which proceeded from the same source. "Why," I cried, "you have an aortic aneurism!" "That's what they call it," he said, placidly. "I went to a Doctor last week about it, and he told me that it is bound to burst before many days passed."

Can an aneurysm be so advanced that a human could notice it without any equipment? I see from Aortic aneurysm#Abdominal aortic aneurysm that "A bruit may be heard from the turbulent flow in the aneurysm", but Bruit only mentions hearing it via a stethoscope, and anyway if it's in the chest it's not an abdominal aneurysm. I'm guessing that it's just a fictionalized device (Jefferson Hope needs to be strong and mostly healthy to do the murder, but he needs to be near death to have a reason to tell his story), but as the aortic aneurysm article says Most intact aortic aneurysms do not produce symptoms without saying anything really about bruits in thoracic aneurysms, I was curious. Nyttend (talk) 12:51, 25 January 2018 (UTC)

I'd say it was a case of WP:FILMSCI, but then again, Conan Doyle was a doctor. Gråbergs Gråa Sång (talk) 15:25, 25 January 2018 (UTC)

It is possible to feel an advanced aortic aneurysm. It feels like a throbbing in the abdomen. One that is likely to burst soon would likely be advanced. 209.149.113.5 (talk) 17:26, 25 January 2018 (UTC)

Anecdotally, my mother noticed throbbing or “thumping” from hers and the doctor confirmed it. It was repaired successfully. Edison (talk) 19:55, 25 January 2018 (UTC)

A palpable vibration over an aneurysm is an aneurysmal thrill. Klbrain (talk) 23:46, 25 January 2018 (UTC)

Gametes of decreased size occurring in evolution of sexual reproduction

Medium sized gametes would have been favored to increase in size (eventually leading to the appearance of female gametes) due to better nutrient storage, but soon after this size had begun to increase, a size decrease would begin among other medium sized gametes (eventually leading to the appearance of male gametes). Why did this occur in the evolution of sexual reproduction? MisterH2005 (talk) 21:53, 25 January 2018 (UTC)

Our writings on this: Evolution of sexual reproduction#Origin of sexual reproduction, and read other sections in this article too. Graeme Bartlett (talk) 23:07, 25 January 2018 (UTC)