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December 17

sodium iodide catalysis of SN2 reactions of diols on dichloromethane

I have an acid-sensitive catechol (which I believe is vulnerable to oxidation in acidic conditions) which I plan to methylenate under basic conditions. Reacting catechols with dichloromethane is discussed in the literature, but one way for me to increase yield would be to convert the dichloromethane into a more active form using an iodide catalyst. However, sodium iodide is not very soluble in dichloromethane. For various reasons, I plan to run the reaction in cyclohexanol with DCM dissolved in it, because the first step that leads to my catechol derivative relies on a ~1% catalytic impurity found in technical grade cyclohexanol (cyclohexenone). I shouldn't expect sodium iodide to be very soluble in cyclohexanol either.

If I produce diiodomethane using the Finkelstein reaction by dissolving DCM and sodium iodide in acetone, the problem is that even if I evaporate the acetone and any leftover DCM (leaving just the diiodomethane) I think the acetone will form an azeotrope with the diiodomethane, and this acetone will act as a surfactant and interfere with acid-base extraction during workup. (The octanol/water logP is -0.042, or an octanol/water partition coefficient of 0.9). At what points would diiodomethane and acetone form a zeotrope? (The liquid range of DIM is 6-182C, acetone -94 to 57C) Yanping Nora Soong (talk) 07:55, 17 December 2015 (UTC)

Diiodomethane is itself available (or can be made and isolated separately ahead of time). Why are you trying to make it in situ, with resulting complications from acetone? But thinking about separation process, I don't quite see why the data you have would necessarily leave acetone present. At say 60°C, most of it should evaporate easily. However, if it is a problem, there are azeotropes of acetone with cyclohexane and with hexane that could be used to drive out the acetone and leave instead a hydrocarbon that is much less water-soluble. DMacks (talk) 10:37, 17 December 2015 (UTC)

DIM is expensive, 5-10 times more expensive than dichloromethane.

NIST reports Antoine constants for DIM [1]: p(in mmHg) = 10^(7.16 - 1715.7/(218.17 + T(in deg C)) -- these constants are however based on very low pressure points however (0.67 to 7.53 mmHg) plus the BP data

selected points for DIM:

57C => 8.4 mmHg (0.011 atm)

100C => 0.077 atm

130C => 0.225 atm

160C => 0.55 atm

182.7C => 0.998 atm

183C => 1.005 atm

(the "max deviation" and "standard deviation" reported for this regression are 0.005 atm and 0.001 atm respectively)

based on the Antoine curve for acetone, acetone reports a vapor pressure of 3.7 atm at 100C, so from this data, should I predict against the formation of an azeotrope? I'm not sure how to put an upper bound on azeotrope formation based on "common sense" or ab initio assumptions. Yanping Nora Soong (talk) 23:15, 17 December 2015 (UTC)

The other question I have is -- what would be the concentration of acetone required (given a partition coefficient of 0.9) to "fuck up" the acid-base extraction workup process? I'm not sure how to model that either. For example, knowing acetone's partition coefficient, and assuming our organic layer has similar lipophilicity to octanol, how much of a problem in acid-base extraction would 0.01%, 0.1% and 1% acetone in the reaction pot be respectively? Yanping Nora Soong (talk) 23:21, 17 December 2015 (UTC)

black holes, space physics stuff

(I don't really know how to word what I want to know properly and I'm a complete astrophysics layperson, so I apologize in advance if it's not clear and I'll try to clarify if need be.)

Been reading black hole and related articles because I want to understand how black holes "work", in a sense. One thing that's mentioned in the main black hole article here is that black holes don't actually suck in all objects around them unless those objects are within their "horizon" (I assume this means the event horizon); from a distance, it has the same gravitational field as normal objects of the same mass. At least, that's my understanding of what's written. What confuses me about this statement though, is that black holes have an enormous amount of gravitational pull (I think because of its incredibly high, dense mass, if I understood correctly?), and I would think that anything caught by its pull would get pulled in eventually. Galaxies are basically a ton of stars being slowly-but-surely pulled in by a black hole at the center, aren't they. Doesn't that mean that black holes do slowly suck in everything around them, or am I just misunderstanding something about how bodies orbiting a significantly greater mass works? Thanks, Drapsnagon (talk) 12:50, 17 December 2015 (UTC)

No, an object can orbit around a black hole in the same way as around a smaller object such as a star or planet. Basically if an object is not moving directly toward a black hole it has angular momentum, and needs to lose it in order to fall in. The usual way for an object to lose angular momentum is by collisions with other objects moving along different trajectories. Looie496 (talk) 13:15, 17 December 2015 (UTC)

(edit conflict) No, not really. Black holes operate under normal gravity, not magical "suck everything in" gravity. Consider the following thought experiment:

• Q? What would happen to the earth if we replaced the Sun with a black hole of the exact same mass in terms of the Earth's motion?
• A? Not a damned thing. Everything would work the same. All objects have a center of mass, which is the imaginary point to where its gravitational pull attracts other objects. If you replace one object with a different object of the same mass in the same location, its gravitational effects would be identical.

The ultimate fate of the universe depends greatly on the exact effects of attractive forces (mostly gravity) and repulsive forces (mostly the metric expansion of space due to inertia left over from the big bang. Again, since black holes don't have magical gravity, just normal gravity; taken in the bulk their gravitational effects are not greater on the whole universe than other objects. While there has been historically some debate over what will ultimately happen to the universe (it really depends on small differences in assumptions between how much various kinds of "stuff" exists that a) we don't know if it really exists and b) if it does, we're not entirely sure how much exists and what it does.), things like dark matter and dark energy. Consensus today is roughly that the universe will keep expanding forever, but evidence is not strong in any direction. Hope that all helps. --Jayron32 13:25, 17 December 2015 (UTC)

To pick a nit: a spherically symmetric body has a g-field equivalent (outside itself) to that of a point mass. —Tamfang (talk) 01:13, 18 December 2015 (UTC)

(ec)"Galaxies are basically a ton of stars being slowly-but-surely pulled in by a black hole at the center, aren't they?" No they are not. Just like the moon is not falling onto the earth (in fact, it is getting further [2]), objects can orbit each other for all of eternity.

Thanks for the answers (and take it easy on me-- as I mentioned, astrophysics (and physics in general really) is a little difficult for me to wrap my head around, and I did mention having a feeling I had it wrong about how orbiting objects work...) Drapsnagon (talk) 13:50, 17 December 2015 (UTC)

• Let me add a footnote that a black hole is not exactly the same as a smaller attractor, because for objects orbiting near it, the gravitational field can be so strong that general-relativistic effects come into play. In particular orbiting objects can radiate energy in the form of gravitational waves, and thereby fall into gradually lower orbits. But this effect is only significant for objects lying very close to the black hole. Looie496 (talk) 14:35, 17 December 2015 (UTC)

  Not really that much of a footnote. General relativity (the modern theory of Gravity) operates on all objects equally, not just on objects near black holes. In close proximity to black holes, the effects of general relativity are more pronounced, but that's not different from saying that "near black holes, gravity is more pronounced" because for our purposes general relativity = gravity, and it's still not magic created by the black holes, simply expected increase of effects that happen everywhere. For example of general relativity effects showing up in a "smaller attractor", see Perihelion precession of Mercury. --Jayron32 14:47, 17 December 2015 (UTC)

  Yes -- but the rate of energy loss via gravitational wave radiation only becomes significant when the field is extremely strong. It's true that the effect exists for smaller attractors, but it is too weak to be meaningful. (I don't think we are disagreeing, just emphasizing different aspects of the situation.) Looie496 (talk) 14:56, 17 December 2015 (UTC)

  • Or just say that the surface of the body interrupts the nice increase of the gravity and prevents the field from getting any stronger. Sagittarian Milky Way (talk) 15:30, 17 December 2015 (UTC)

I think you might find Crash Course Astronomy interesting. Here's the episode on black holes. --71.119.131.184 (talk) 04:55, 18 December 2015 (UTC)

Let me contradict with some of what you said above. In some sense, black holes do suck in objects that orbit very close to them. There are locations around a black hole where the gravity is so strong that no matter how fast you orbit, you can't stay there. This actually applies not only to black holes, but to objects that are almost as dense as black holes. It does not apply to ordinary non-sense planets or stars though. If you don't collide with the atmosphere or other objects, you can orbit a spherical planet arbitrarily close. (You could count this phenomenon as black hole magic, because it happens only in relativity, not in Newtonian gravity.)

But it is true that this applies only to regions of space very close to the black hole, to a distance comparable to the event horizon. So indeed stars in a galaxy aren't "slowly-but-surely pulled in by a black hole at the center", because they are far from the black hole where they can have a periodic orbit. – b_jonas 11:32, 18 December 2015 (UTC)

Cloud seeding to prevent floods

Recently there was severe flooding in Cumbria caused by a storm. With weather forecasts giving a few days warning of a big storm's approach, would it be practical to seed clouds while they were still over the sea, and prevent dangerous levels of rain falling on land? I have read the cloud seeding article which doesn't seem to rule this out, but doesn't mention it happening either. 94.1.53.114 (talk) 15:19, 17 December 2015 (UTC)

Hey, it's December - the week of the American Geophysical Union Fall Meeting! If ever there were a group of respectable and informed scientists who could take this kind of question seriously, it would be them. A few years ago - 2013, I think - the entire "theme" of the fall meeting was developing new science to support geoengineering as a response to climate change. Here's their policy statement: Geoengineering Solutions to Climate Change Require Enhanced Research, Consideration of Societal Impacts, and Policy Development. "Three proactive strategies could reduce the risks of climate change: 1) mitigation: reducing emissions; 2) adaptation: moderating climate impacts by increasing our capacity to cope with them; and 3) geoengineering: deliberately manipulating physical, chemical, or biological aspects of the Earth system (emphasis added).

Here's another workshop from 2014 - Refilling California’s Reservoirs—The Roles of Aerosols and Atmospheric Rivers, presented by Scripps from San Diego. Again, the take-away is that serious scientists have actually investigated this kind of idea.

And here's a 2009 blog, A Cold Drip: Emergency Water from the Air, which presents the more dismal view that "there isn’t much scientific evidence that cloud seeding actually works well enough to be useful." So, not everyone is enthused by the idea!

You can scour their publications - here's a search query for GRL - to see what has been studied specifically with respect to cloud seeding; mostly, the best scientific answer we have today is that we need more research.

Nimur (talk) 15:48, 17 December 2015 (UTC)

China is the world's leader in attempting cloud seeding for weather modification. Most of the time they are trying to increase rainfall for crops, but at least occasionally they do something more like what you have in mind. During the 2008 Olympics, they announced an effort to use cloud seeding on weather fronts approaching the Beijing Olympics in an effort to get them to rain out before they got to Beijing. [3] I am unaware of any effort to try and determine how effective these or similar efforts actually are at reducing downstream rainfall. Dragons flight (talk) 10:40, 18 December 2015 (UTC)

Glaciers on Pluto

[4]

That article talks about water ice "mountains" on Pluto up to 1.5 miles high. On Earth, those wouldn't last more than a few thousand years, because gravity would cause the ice to flow as glaciers and flatten out.

1) Does the same process work on Pluto ?

2) Does the lower gravity slow it down proportionately ?

3) Do colder temps slow it down ?

4) Any other reason it would differ on Pluto ? StuRat (talk) 16:03, 17 December 2015 (UTC)

Yes! There is an emergent system-property called the critical angle of repose that is studied in geology, in the study of granular materials, and in related fields. This property determines how steep and how tall mountains can be - and it is widely studied in planetary science, because it depends on the gravity and the material composition of the world, and lots of other factors. Ice is an even more complicated scenario, because it's not quite a perfect solid material (it deforms in a non-elastic fashion).

As always, I defer to my favorite planetary science book, de Pater and Lissauer, which does have a chapter on the geological process that shape a planet - including its highest and steepest geologically-sustainable mountains. We have only just begun to have high-resolution data for Pluto, so it'll probably be a while before we have great geophysical models for it; but to answer everything StuRat asked in one shot: yes, all these parameters contribute to the sustainable mountain heights and slopes. You might also want to read our article on orogeny, which regrettably has a decidedly Earth-based bias.

Nimur (talk) 16:21, 17 December 2015 (UTC)

As to your third question, the lower the temperature the slower ice will deform under its own weight. Glaciers flow because for the temperatures we experience on Earth, ice is always not too far from its melting point. Compared to other materials, this is a high homologous temperature and makes crystalplastic processes more likely. At the surface temperature that we think is likely on Pluto (~44 K), such processes are unlikely to be active, so the interesting question is, how did the mountains form in the first place? Mikenorton (talk) 11:32, 18 December 2015 (UTC)

My bet for how it formed is a water volcano. That is, water squirted up and froze immediately when it hit the surface. Now that poses the question of where the heat came from to produce liquid water in the first place. Of course, Pluto would have been plenty hot when it formed, along with the solar system, some 4.3 billion years ago. So ice volcanoes could have formed after the surface cooled but the interior remained warm. But how long would the interior remain warm ? Well, it gets little solar heating to seep down to the interior, but it does have a rather large moon, Charon, along with some smaller moons, and that might provide enough tidal heating to have kept the interior warm (along with radioactive decay). So this all relates to my Q. Could those ice mountains be billions of years old, or only millions or thousands ? If not billions, then that implies that the interior of Pluto is still warm.

Another possibility is that Pluto wasn't always where it is now. That is, it was captured from somewhere else in the solar system or even outside. The capture process might have generated the heat required. StuRat (talk) 15:22, 18 December 2015 (UTC)

Evidence for cryovolcanism - here and possible explanations. Mikenorton (talk) 11:05, 19 December 2015 (UTC)

As to the age of the mountains - NASA reckon about 100 million years. Mikenorton (talk) 11:09, 19 December 2015 (UTC)

Also, of course, Pluto <troll>isn't really a planet</troll>, and its surface gravity is a measly 0.063 g. So a 1.5 mile high mountain of ice on Pluto weighs the same as 500 feet of ice on Earth. Wnt (talk) 14:26, 18 December 2015 (UTC)

Does the curvature of the surface play a role? Contact Basemetal here 14:40, 18 December 2015 (UTC)

As far as I can see, the biggest difference is that the reduced pressure at the base of the glacier due to lower gravity, combined with lower temperatures - would combine to make it difficult (and maybe impossible) for liquid water to form under the ice as it does here on Earth. That water lubricates the flow of the glacier - and without it, everything happens much more slowly.

The Pluto-Charon system is the only known double planetary system, although the barycenter of our own Solar System lies Jupiterward of Sol. μηδείς (talk) 02:59, 19 December 2015 (UTC)

You didn't explain how that would affect glaziers. Pluto is tidally locked to Charon - so Charon doesn't cause periodic tidal effects - and the sun is too far away to have a significant tide. So there would be only the smallest of tidal forces on the glaciers. SteveBaker (talk) 03:32, 19 December 2015 (UTC)

About the tidal locking, do we know if there is still "tidal rocking" ? That is, do the two still rotate with respect to each other a bit, then go back the other way, and repeat ? If so, I would expect that this would still generate significant tidal heating. StuRat (talk) 07:00, 19 December 2015 (UTC)

You mean libration? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 03:04, 20 December 2015 (UTC)

Yes, thanks, that's the term. StuRat (talk) 03:40, 20 December 2015 (UTC)

I think glaziers would be pretty much out of luck on Pluto. Not too many people are going to go that far to buy a window pane. --Trovatore (talk) 03:34, 19 December 2015 (UTC)

Yes, anyone living on Pluto would have to be highly eccentric. But, reflecting on that paneful typo, rather than making light of it, I wonder how warm you could get it inside an ideal greenhouse on Pluto. Would anyone care to do the math, and illuminate me with your brilliance ? StuRat (talk) 06:55, 19 December 2015 (UTC)

• Thanks for the recommendation, User:Nimur. My alma mater has just instituted an ILL self-serve system, and my order for Planetary Sciences is their inaugural request. μηδείς (talk) 19:35, 18 December 2015 (UTC)

Infrastructure asset management

Do engineers who manage infrastructure assets ever go out on site? — Preceding unsigned comment added by 2A02:C7D:B901:CC00:7527:BB74:28CB:C5A3 (talk) 17:55, 17 December 2015 (UTC)

ObPersonal, but in my 20 years of experience working in the fields of Facilities/Asset Management and Engineering Administration, I would say that almost all such Engineers would go out on Site occasionally, regularly or very frequently. One who did not would in most instances be carrying out mere administration (as I do) that would not usually require engineering qualifications (which I myself do not have). An exception might be a qualified Engineer unable to work in the field due to injury or illness, who might then revert to a purely office-based role. (A Structural Engineer who works as a consultant in my office makes no Site visits, because he's 84 years old and has Parkinson's disease, but his expertise and knowledge is still valuable.) Of course, it's impossible to give a completely definitive answer to such a sweeping question about a broad field: there are bound to be exceptions. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 18:27, 17 December 2015 (UTC)

December 18

How will moving to the Grand Cayman Islands change my DNA?

I've asked the question before but it was interpreted differently and understand it is very scientific in nature. I am a male of Indian origin living in Florida for the better part of 15 years. I am probably moving to the Grand Cayman Islands and was wondering how a different land can change DNA, how it could change your appearance further down the line/genes etc.

In other words, how does changing the environment cause changes or mutations in one's DNA? — Preceding unsigned comment added by 99.229.130.56 (talk) 02:35, 18 December 2015 (UTC)

If I need to clarify, how can I edit the question? — Preceding unsigned comment added by 99.229.130.56 (talk) 02:02, 18 December 2015 (UTC)

Refer to the last time you asked this type of question, because the answers are the same. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:13, 18 December 2015 (UTC)

Your personal DNA will not change. Changes take place over many generations through processes described in the article titled Genetics which you can read and follow further discussions about. Reproduction is required for changes to propagate through a population. One person does not themselves "change their DNA" because of where they live. --Jayron32 04:02, 18 December 2015 (UTC)

Mutations can modify the DNA of individual cells in an organism (not the DNA of all cells in an organism as a whole, but a mutation in a reproductive cell will be passed down the line and will affect the DNA of all the cells of the offspring resulting from that particular reproductive cell) and some environmental factors may induce mutations but I'm not aware that living in the Grand Cayman is specifically correlated to any specific mutation. I think there's no such thing as the "Grand Cayman Islands". As far as I know there is an island called "Grand Cayman" which is part of the "Cayman Islands". Contact Basemetal here 05:01, 18 December 2015 (UTC)

Maybe he's hoping to mutate his tax liability. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:35, 18 December 2015 (UTC)

Well as far as you are concerned it will make no difference. But from my perspective without knowing you're in the Grand Caimans I'd say you had a reasonable chance of having dog DNA as in On the Internet, nobody knows you're a dog but now I'm more inclined to guess agouti. ;-) Dmcq (talk) 11:15, 18 December 2015 (UTC)

A change in environment can change your DNA, specifically in the case of DNA methylation. This is only a part of epigenetics and most of the changes would occur to histones that associate with the DNA but are not part of it. While a few epigenetic effects are known, I'm by no means ready to suggest any means by which I could predict specific changes in methylation pattern from moving to those islands - still, I wouldn't say it's impossible, with enough thought on the topic.

Also, if you spend too much time frolicking in the sun, pyrimidine dimers might make an unpleasant appearance - those changes however should be temporary, unless different, related bad things happen. Wnt (talk) 11:42, 18 December 2015 (UTC)

None of those things are particular to the Caymans though. He can frolic in the sun where he's at. --Jayron32 12:37, 18 December 2015 (UTC)

True. The question is, will moving to the Caymans, on average, tend to change some of these environmental influences? It's possible. I think if I had a database of DNA methylation comparable to what 23andme has for sequence, that included a lot of Cayman Islanders and others, it is possible that I could find enough things that correlate with Cayman Islands residency. Perhaps, given a DNA sample, I could come up with an improved guess whether that person lived there or not. I don't know that to be true, however; and even if it is true it would only be statistical, depending on someone there happens to live on a certain water source with a certain contaminant, eats a certain kind of fish, etc. Wnt (talk) 14:22, 18 December 2015 (UTC)

See Lamarckism. —Steve Summit (talk) 01:02, 19 December 2015 (UTC)

• I suspect User:Timothyhere's genes will never change, no matter what his island nation destination. μηδείς (talk) 02:55, 19 December 2015 (UTC)
  • If he got eaten by a Caiman, that could change his DNA. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:56, 19 December 2015 (UTC)

Yes, but in the Caymans his DNA stands a better chance than in Florida where it might be blasted to Kingdom come by a spree killer armed with an assault weapon and hundreds of rounds of ammunition. Akld guy (talk) 21:31, 19 December 2015 (UTC)

So they never have armed robberies in the Caymans??? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:29, 20 December 2015 (UTC)

But why did Florida come in to this? When Timothyhere was IP socking their IPs used to look up to Argentina. This IP seems a little different, actually looks to me more like the racist Toronto IP than Timothyhere. Nil Einne (talk) 17:35, 20 December 2015 (UTC)

The OP said right at the start, I am a male of Indian origin living in Florida for the better part of 15 years. I am probably moving to the Grand Cayman Islands... Akld guy (talk) 20:19, 20 December 2015 (UTC)

... but he didn't explain why he was posting from Mississauga, Ontario, Canada. There might be an innocent explanation, of course. People do go on holiday there, I guess. Dbfirs 09:39, 21 December 2015 (UTC)

Artificial Eggs

Is it possible to make hen's egg artificially? If yes then, is it cheaper to make eggs artificially than eggs from poultries ? — Preceding unsigned comment added by 117.247.217.62 (talk) 16:07, 18 December 2015 (UTC)

Basically: no. Making a synthetic peptide is possible but absurdly expensive, and because of the chemistry involved you'd be very reluctant to eat it. Albumin is a peptide - a longer one than is generally synthesized, because the yield drops for each amino acid added. And, of course, eggs, contain many other substances. Of course, with the right machine, you could make eggs cheaply and easily... that machine is called a hen. :) Wnt (talk) 16:11, 18 December 2015 (UTC)

I suppose I should add for fairness that there are publications about artificial meat grown in tissue culture - that is not quite "artificial" by my way of thinking, but already far too artificial IMHO ever to be affordable or safe. The idea is a darling of vegan activists, but the meat will not be purged of toxins or have its wastes recycled by the liver or guarded from pathogens by the immune system. Dialysis might largely replace the kidneys, but not with the same kind of resource reclamation. It's a myth, sorry - at least, that's what I think. Wnt (talk) 16:14, 18 December 2015 (UTC)

A company that's bankrolled by Bill Gates produced something called a ‘plant egg’, called Beyond Eggs, in Whole Foods in California. That was back in 2013. It's made from peas, sunflower, lecithin, canola, and natural gums - and it is indeed cheaper than real eggs - but it comes in a large sachet, not an egg-shell. So right there, you know that you're not getting a hard-boiled plant-egg. Is that good enough for you? Well, maybe - it's gotten reasonable reviews for some kinds of recipes - and terrible reviews for others.

Egg substitutes lists other possibilities.

So you can definitely make an artificial thing that looks like an egg. You can probably make something that tastes like an egg...maybe you can give it most of the nutrients that an egg has...but then you also need to have it behave in the same way as a real egg when you cook it in any of a dozen different ways...maybe you can wrap it in an artificial shell that lets it last for a long time without refrigeration. But each step along the road gets harder and harder. What you can't do is "Make a truly artificial egg" that's indistinguishable from the real thing - there are just too many subtle details like membranes and such that are incredibly difficult to reproduce.

The question comes down to how much fidelity you need in your fake egg. If it's relatively low fidelity - it could maybe work out cheaper than a real egg.

This year, egg prices have oscillated between 10 cents up to 20 cents per egg. I can't see much benefit in building a completely authentic synthetic version of something that's that cheap - UNLESS there is something you want to happen differently. Maybe you want an egg with lower cholesterol content - or maybe a larger egg than a hen can lay - maybe you're a vegan. If there is something that you can do differently to make a better egg - then you can charge more for it - and then it might be possible to do that synthetically.

SteveBaker (talk) 17:07, 18 December 2015 (UTC)

If inaccurate reproductions are allowed, I recommend the caramel variety. Who needs chickens? :) Wnt (talk) 22:22, 18 December 2015 (UTC)

Powdered eggs are made from actual eggs. This ... food ... is sometimes used by long-range campers, and it is also ... eaten... as an emergency food supplement in disaster zones or war rations. They are cheaper than real eggs, and safer to store in hard conditions. You'd be hard-pressed to identify this ... cuisine ... as an egg if you ever have the misfortune to eat it.

WP:OR: Of all of the powdered food replacement products I've ever eaten - powdered milk, powdered onion, powdered fish, powdered soup... powdered egg is probably the one that is least similar to its fresh form.

Here is a blog post from the Icebreaker team, out of NASA Ames, who ate powdered egg during their Antarctic stay.

Incredibly, non-powdered (rehydrated and/or frozen) eggs were even available on the Space Shuttle. Powdered egg is only called for in the most extreme harsh environments.

Nimur (talk) 01:43, 19 December 2015 (UTC)

• The OP geolocates to Sawai Madhopur, Rajasthan. If the objection is to eating real chicken eggs, many recipes allow the substitution of vegetable oil or beans. It would be helpful to know the context in which the question is being posed. μηδείς (talk) 02:46, 19 December 2015 (UTC)

• If there is a moral objection to eating "living things", many consider unfertilized eggs to fall outside that category. Candling can be used to ensure you don't accidentally get a fertilized egg. StuRat (talk) 06:47, 19 December 2015 (UTC)

• Or just not having a rooster around? Contact Basemetal here 07:00, 19 December 2015 (UTC)

• Not always as simple as you might think. If you live in a place zoned for raising chicken, then your neighbors do, too, and they might have roosters, who will try their best to impregnate your chickens. So, you better not ever let them outside. (Domestic chickens might not fly well, but many can manage to make it over a fence.) StuRat (talk) 07:10, 19 December 2015 (UTC)

So, all such large amount of eggs are hens' productions? — Preceding unsigned comment added by 117.247.217.22 (talk) 11:39, 20 December 2015 (UTC)

Yes. Roosters hardly ever lay eggs. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:02, 20 December 2015 (UTC)

Hardly ever. Not that the Daily Mail is a reliable source. Tevildo (talk) 14:08, 20 December 2015 (UTC)

Baumgartner's balloon

Hello! I'm trying to calculate the buoyancy force acting on Felix Baumgartner's balloon at lift-off. However, I get a seemingly unrealistic 8.34 MN. The values I am using are 834.497,16 m3 for the volume of the balloon and 1.127 kg/m3 for the density of air. Is my math correct? If not, what am I doing wrong? Thanks. --Leptictidium (mt) 10:06, 19 December 2015 (UTC)

Your math is right, but the procedure is a little different than you might think after seeing illustrations of the enormous balloon next to the Statue of Liberty. High-altitude balloons are only inflated on the ground to a very small fraction of their capacity. This allows the helium to expand to match the pressure of air and fill the entire volume once the balloon reaches float. You can read a little about it here, although it's light on details. Let's say the balloon is fully inflated at 120,000 feet where the air pressure is 0.067 psi [5] or 0.0046 atmospheres. Let's also assume that the amount of helium in the balloon is the same at float as it was at the end of inflation on the ground. (In reality it will lose some helium, but this should be a small fraction of the total.) Then the volume of the balloon when it is launched should be 834497 m^3 * (0.0046 atm / 1 atm) = 3839 m^3 and the lift would be only about 38000 N. The total mass of the balloon + payload was a few thousand kg, presumably a little under 3800 kg so that the force of lift would overcome gravity plus a little more to give a gentle ascent. --Amble (talk) 20:20, 18 December 2015 (UTC)

You can also see this in photos of the balloon at launch and when it reaches float altitude. At float, the capsule is hanging just under the bottom of the balloon on a short cable [6]. At launch, it looks like it's at the end of a very long cable [7]. That "cable" is actually the rest of the balloon, while only a very small portion at the top has inflated so far. It slowly inflates as the helium gas expands during the ascent. --Amble (talk) 20:32, 18 December 2015 (UTC)

@Leptictidium: Your math looks suspicious. 834.497,16 m³? Do you mean 834 497.16 m³? (Let's just say 834 500 m³) What value are you using for the density of helium at sea level pressure? Dolphin (t) 03:30, 19 December 2015 (UTC)

@Dolphin51: That's just a difference of notation in what makes a decimal mark. --Amble (talk) 05:46, 19 December 2015 (UTC)

Many thanks for that. I wasn't familiar with the decimal comma or the point as a thousands separator until I read your link. However, I'm still suspicious about Leptictidium's math, or should I say his physics. He has quoted the volume and the sea level density of air, and arrived at a force in meganewtons. He hasn't disclosed his intermediate steps and I think they contain at least one error. (Anyone experienced in applied math or physics would not use 8 significant figures in a calculation of this kind.) I have tried a few simple calculations and I don't arrive at 8.34 meganewtons. Dolphin (t) 06:37, 19 December 2015 (UTC)

The intermediate step was, quite naturally, the buoyancy force equation: density of the gas displaced in kg/m3 * gravitational acceleration in m/s2 * volume displaced in m3: 1.127 * 9.8 * 834,497.16.Leptictidium (mt) 10:09, 19 December 2015 (UTC)

The numbers seem about right although, as explained by Amble, they are for the wrong calculation: Lep has calculated on the assumption that at ground level the balloon is filled with helium. The size of the balloon is confirmed here as "almost 30 million cubic feet": if it was exactly 30,000,000, then that would be just over 849,500 m³. The density of air depends on the temperature, but is 1.205 kg/m³ at 20°C; however, the correct value to use for the calculation is the difference between the density of air and the density of helium; at 20°C helium is 0.1664 kg/m³, so the difference is 1.039 kg/m³. By way of comparison, the Hindenburg had about 1/4 that volumne and a fully loaded mass of 214,000 kg on one of its trips (source: The Golden Age of the Great Passenger Airships: Graf Zeppelin and Hindenburg by Harold G. Dick with Douglas H. Robinson), thus requiring 2.1 MN of buoyancy. (Of course it used hydrogen, but the difference is small.) Something over 8 MN would be about right—if it was the right calculation. --76.69.45.64 (talk) 11:11, 19 December 2015 (UTC)

The buoyancy force equation, as presented in our article, is relevant to a solid immersed in a liquid. The buoyancy force is only one of two forces acting on the solid (the other force is the weight of the solid object.) In this format the buoyancy force equation is not appropriate to determining the net force acting on a gas-filled balloon. I agree that it is the difference in density that is relevant, not simply the density of air. If a balloon with this volume is filled with CO₂ it would displace the same amount of air, but as CO₂ is 1.67 times more dense than air the result would not be a buoyant balloon. Quite the opposite. Dolphin (t) 12:10, 19 December 2015 (UTC)

The buoyancy force is the same no matter what sort of object is immersed in what sort of fluid. It is indeed opposed by the weight of the object, and Amble's comment below is also correct. --76.69.45.64 (talk) 23:08, 19 December 2015 (UTC)

I think Leptictidium was trying to determine the resultant force on the balloon at lift-off. That would be relevant to a lighter-than-air balloon because it would partly determine the initial acceleration away from the ground. I also think his math was deficient because he didn't take into account the properties of helium so he didn't find the resultant force. When a large helium-filled balloon first leaves the ground it accelerates very slowly so Leptictidium was expecting a small force. That is why he was surprised to find such a large force as 8 meganewtons. Dolphin (t) 04:31, 20 December 2015 (UTC)

He explicitly said he was trying to calculate the buoyancy force. His calculation was correct assuming the balloon is fully inflated on the ground -- but it isn't. --Amble (talk) 04:41, 20 December 2015 (UTC)

You can include the mass of the helium in the total mass of the balloon rather than the buoyancy force, so that's perfectly fine in the OP's calculation. It makes no difference to the buoyancy force calculation whether the fluid is liquid or gas, and whether the floating object is solid or gas-filled. --Amble (talk) 18:39, 19 December 2015 (UTC)

December 19

Orion, Sirius, and sunrise on Dec 25

I saw a thing on YouTube that says that the three stars in Orion's belt and Sirius form a line that points to where the Sun rises on December 25. Is that correct? Bubba73 ^{You talkin' to me?} 05:35, 19 December 2015 (UTC)

Where in the world would that be? Richard Avery (talk) 07:46, 19 December 2015 (UTC)

There appear to be some weird things going around about that, but they seem awfully vague. The main thing I would note is that you can use the belt of stars to find Aldebaran, a star in Taurus. [8] And the Sun isn't in Taurus on Christmas. Wnt (talk) 09:49, 19 December 2015 (UTC)

As noted, "where the Sun rises on December 25" is different for every latitude in the world: indeed, there are large areas in the Arctic where it doesn't rise on that date, but Orion is still visible.

In addition, alignments like "Orion's belt and Sirius" don't point in the same direction at all times; the place they point to would shift as the stars proceed from rising to setting.

In short, there may be some place and time where the claim is true, but in general it appears to be nonsense. --76.69.45.64 (talk) 10:42, 19 December 2015 (UTC)

I'm going to go out on a limb and guess this video is from some Biblical literalist trying to prove the Star of Bethlehem was a real event. --71.119.131.184 (talk) 11:50, 19 December 2015 (UTC)

No one knows the date or month Jesus was born, so such an effort would be useless. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:17, 19 December 2015 (UTC)

The question makes a nice exercise in spherical geometry, although some misunderstandings in the question need to be cleared out first. Any two points on the sky define a great circle, in this case we use Sirius and the central star of Orion's belt (Alnilam). Two great circles intersect in two antipodal points on the sky; in the question, the second circle is the ecliptic, the path of the Sun over the course of a year. It makes sense to ask when the Sun passes through these intersection points. That has nothing to do with sunrise or such topocentric points of time.

To do the calculation, take the equatorial coordinates of Sirius and Alnilam and convert them to cartesian coordinates (e.g. x-axis towards the vernal point (α=0, δ=0), y-axis to α=6 hours, δ=0, z-axis to the celestial north pole, δ=90°. This gives two unit vectors. The great circle through the stars is conveniently given by the direction of its pole, this is simply calculated as the (normalised) vector product of the vectors towards the stars. One intersection point of the circle and the ecliptic is now given by the vector product of the unit vectors towards the pole of the circle and the unit vector towards the pole of the ecliptic; the other is just its antipodal point. I find for the relevant intersection point α = 15h58m08s and δ = -20°29′27″. Stellarium puts the Sun in the position on 24 November, a month earlier than claimed. --Wrongfilter (talk) 12:30, 19 December 2015 (UTC)

Some of the comments above make it sound like the stars are getting stirred. If the Sun were in Taurus - and that does happen once a year, though not quite on the date the astrologers use - Orion's belt would be pointing at it when it rose, when it set, in London or Baghdad; even at the South Pole though you might need to invent a better neutrino detector to do the observation. The point where the Sun rises in the East may vary, but the Sun is always there! Wnt (talk) 17:05, 19 December 2015 (UTC)

Thank you for the replies. This is probably one of those things that people make up and hope to spread around. I saw a few seconds of it on a YouTube video, I don't know which one. They seemed to be getting to the point that the three stars in the belt are the wise men and Sirius is the star of Bethlehem, etc. Bubba73 ^{You talkin' to me?} 18:30, 19 December 2015 (UTC)

Oh, if that's what it's about then one needs to take precession into account. I used Stellarium for today; for 0AD, the sun is in that spot at a different date. If I'm not mistaken, it does take the date into December, although it doesn't reach the 25th. Not that I would support any wild speculations based on that. --Wrongfilter (talk) 18:51, 19 December 2015 (UTC)

There is no such date as 0AD. There is only 1BC and 1AD. Akld guy (talk) 21:19, 19 December 2015 (UTC)

For astronomical purposes, there is indeed a year zero. --Amble (talk) 21:55, 19 December 2015 (UTC)

This is apparently a bit of nonsense from the Zeitgeist movie. See [9]. --Amble (talk) 19:10, 19 December 2015 (UTC)

Probably so because I did see that word mentioned. Bubba73 ^{You talkin' to me?} 22:24, 19 December 2015 (UTC)

Truss type

What's that special vertical truss called? I think it has an Italian name. 82.132.223.218 (talk) 15:59, 19 December 2015 (UTC)

Have you read Truss? I'm not sure it's in there, but it might lead somewhere. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:13, 19 December 2015 (UTC)

If it's not there, can you give a clearer description of what you mean or where it can be found? --76.69.45.64 (talk) 05:11, 20 December 2015 (UTC)

I don't know of an Italian term, but do you mean a transmission tower (for electrical wires, etc.), or something like the Eiffel Tower ? StuRat (talk) 05:17, 20 December 2015 (UTC)

Piloti. Widneymanor (talk) 16:03, 20 December 2015 (UTC)

Those seem to lack the cross-supports I associate with a truss. StuRat (talk) 19:57, 20 December 2015 (UTC)

Weather balloons

What pressure differential (between inside and outside) can they withstand before popping ? StuRat (talk) 16:23, 19 December 2015 (UTC)

It's the degree of expansion (which is of course related to the pressure difference) that governs the altitude limit - see here for such a calculation. Mikenorton (talk) 16:32, 19 December 2015 (UTC)

You may be interested in our article Superpressure balloon. -- ToE 17:38, 19 December 2015 (UTC)

How do evolutionists explain that life appeared just once?

Why wouldn't new living beings be created again and again? However, all living beings are related to each other. You could say the conditions changed, and now, it's not possible to create life anymore. However, why, in the time it was possible, didn't several different life forms arise independent of each other?Scicurious (talk) 20:05, 19 December 2015 (UTC)

Life appeared multiply times on earth, but once the first life had a foothold, it became more efficient very quickly and thus out competed (ate) all the other times life appeared independently. Do you have any idea how competitive life is? Compare this with why despite the fact written numeral system appears multiple times independently, the Hindu–Arabic numeral system ate them all up instantaneously. 175.45.116.66 (talk) 22:01, 20 December 2015 (UTC)

Who says they aren't? And who says they didn't? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:08, 19 December 2015 (UTC)

I don't want to endorse the view the OP appears to be heading to, but Common descent answers your question, Bugs.--Denidi (talk) 20:12, 19 December 2015 (UTC)

There may have been other life started that didn't survive. Bubba73 ^{You talkin' to me?} 20:26, 19 December 2015 (UTC)

Yes, it's difficult to prove that life only originated once. In any case, other life forms didn't survive long. At least we can say that there is one common origin to viable life forms.--Denidi (talk) 20:36, 19 December 2015 (UTC)

Perhaps it is extremely unlikely for life to appear on a planet. If it is one in a billion chance then there maybe hundreds in our Galaxy, but probably none where it happened twice. Or maybe the chance is only 1 in 10⁴⁰⁰, in which case the Anthropomorphic principle ensures that we are on the one place that life appeared in the Universe. Or for life to appear by itself is impossible, requiring special creation, but evolutionists would not claim that. Graeme Bartlett (talk) 21:34, 19 December 2015 (UTC)

There's quite a few people who think life and even intelligent life elsewhere in the universe is very probable. I just have this picture of all these missionaries from Earth trying to convince some alien lifeform of why they should follow the teachings of Christ or Allah or the Buddha ;-) Dmcq (talk) 21:36, 19 December 2015 (UTC)

Anthropic principle, I think. The anthropomorphic principle is succinctly expressed in Rule 39. Tevildo (talk) 13:56, 20 December 2015 (UTC)

As has been mentioned above, it's quite possible that life did arise independently several times, but the earliest life on the scene used its head start to eat all the others. As everything at this point would have been microscopic single-celled (at best) organisms, no fossil evidence of this is likely to have been preserved.

A second possibility is that once one form of life had arisen, it ate the chemical precursors that might otherwise have given rise to other forms of life, so they never could.

A logical third possibility is that life forms arose several times (not necessarily on Earth) but were repeatedly wiped out by inimical conditions except for the most recent which persisted, giving rise to everythng now living on Earth. {The poster formerly known as 87.81.230.195} 94.10.79.49 (talk) 22:30, 19 December 2015 (UTC)

Perhaps multiple early life forms that began on their own merged to form those that survived. For example, Neanderthals seem to have merged with modern humans rather than simply becoming extinct. Mitochondria may have merged with other single-celled organisms early in the evolutionary process. Obviously Neanderthals didn't arise independently of modern humans, and mitochondria may not have, either, but there might be some other constituents of modern life that did. See symbiogenesis. StuRat (talk) 03:48, 20 December 2015 (UTC)

I think it's pretty clear that there are three possible reasons here:

1. The probability of a self-replicating molecule appearing spontaneously could be astronomically unlikely. But the universe is insanely large - and quite possibly infinite - and the amount of time available for this to have happened is insanely long (on the scale of chemical reaction times).
   • If this is the case, then life only happened sufficiently few times that it only ever happened once (and we're obviously the result of that).
   • Or the probability of it happening twice on the same planet is astronomically unlikely - so there is life elsewhere - but we just haven't found it yet.
2. The probability of that self-replicating molecule appearing spontaneously isn't high - but it's common enough to happen rarely over the life of our planet.
   • If this is the case, then perhaps we should expect to see several (or perhaps MANY) kinds of life that are fundamentally incompatible with each other (eg one uses DNA/RNA - and the other uses something completely different). We don't see that - so if this is what happened, then once one form of life appeared, it somehow suppressed the other forms.
     • ...by consuming the resources needed to build new lifeforms.
     • ...by out-evolving the other forms.
     • ...by changing the conditions sufficiently to shut down subsequent spontaneous formation events.
3. The probability of that self-replicating molecule appearing spontaneously is high. Life has been created multiple times here on earth - but for some reason we haven't recognized or discovered the other forms yet.
   • Maybe the other forms only live in very unusual places (under the ice-caps, in very deep ocean trenches, deep underground, in the ionosphere).
   • Maybe we see them all the time, but don't realize that they are alive because they are so unlike us.
   • Maybe there is only a very small set of initial replicating molecules that can actually produce life - and they all produce identical styles of DNA/RNA so we don't realize that they are the result of separate life-creation events.

The thing is - we don't (yet) know which of those things it is - there is research going on - but we really don't know. My money is on (1) because the simplest self-replicating molecules are pretty darned complicated and the probability of such a molecule just randomly appearing from the available raw materials is insanely small - but not zero.

There are perhaps ten trillion planets in our galaxy. There are at least 200 billion galaxies - but probably an awful lot more than that. 2x10²⁴ is a good number here. If 1% of them could support life - we still have 2x10²² of places where life could form. There have probably been planets in existence for 13 billion years - which is 4x10¹⁷ seconds. If these planets are about the size of ours, and they have similar volumes of water, the earth has 1x10²⁷ cubic millimeters of water.

That means that if one complex chemical reaction happens in every cubic millimeter of water every second - then there have been 2x10⁶⁶ chances for a self-replicating DNA molecule to happen by chance alone somewhere and sometime in the universe so far. Even if the odds of that happening is 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 to 1 against, then that's enough for us to exist.

But there have been "only" 3 billion years (1x10¹⁶ seconds) and only one set of oceans for life to have formed in here on earth - that's "only" 1x10⁴³ opportunities for life to form.

So if the odds of life forming spotaneously in one second and one cubic millimeter of water is worse than 10,000,000,000,000,000,000,000,000,000,000,000,000,000,000 to one but better than 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 to one - then it would be no surprise that it only happened once here on earth (so far).

Given the complexity of the simplest self-replicating molecules that we know of - I think those odds are quite reasonable. We have created artificial RNA molecules with a couple of hundred base-pairs that come close to being able to self-replicate...so probably the first ever RNA strand was about that length. With four base-pair "letters", the odds of this strand forming from a set of randomly connecting base pairs is 4²⁰⁰ to one against.

That's 1x10¹⁰⁰...which suggests that:

If one random collection of base-pairs was created in every cubic millimeter of water every second for the life of the universe, then the universe would need to be 1x10⁴⁴ times larger than the 'visible' universe that we can see. That's perfectly possible...and of course, chemical reactions happen faster than once per second, and many many more than one could happen in every cubic millimeter of water.

It's also possible that there are shorter RNA strands that could self-replicate - and they wouldn't have to be much shorter to erase all of those extra zeroes...also, we only have one example of such a short self-replicating strand that's been created in the lab - that doesn't mean that there aren't a lot of other similar ones that would work just as well.

It seems plausible - that with sensible guesstimates on the time to randomly create a sequence of base-pairs and a reasonably sized universe and a reasonably simple self-replicating RNA strand - that life could pop into existence just once and never again.

The difficulties in finding a mechanism by which life is initially created is easily resolved if the probability of precisely the right molecules colliding in precisely the right way to make an RNA molecule in a protective coat of some kind is really insanely unlikely - but if the universe is truly immense and old, so it happens (rarely). That's a good enough explanation - and it follows Occams razor...which is always a good clue if you don't have a better idea. SteveBaker : <== (That was my 30,000th edit of Wikipedia BTW!) SteveBaker (talk) 15:51, 20 December 2015 (UTC)

Many scientists interested in abiogenesis think it's unlikely the first life used RNA, exactly because it's a relatively complex molecule. Life probably initially used something else to store genetic information; RNA and DNA came later. Of course, as with everything in this topic, these are just educated guesses at this point. (See abiogenesis and RNA world for some discussion.) --71.119.131.184 (talk) 13:47, 21 December 2015 (UTC)

New charity article may need a look for promoting AIDS denialism

Just seen a newly-created article about a UK charity called the Immunity Resource Foundation. The article so far is entirely written by a user who discloses that they were paid to write the article. I'm concerned that the 'non-incorporated' charity seems to be a front to promote HIV/AIDS denialism and that the article doesn't clearly explain this. Can someone look into this? 85.211.96.114 (talk) 22:50, 19 December 2015 (UTC)

WP:FTN might be a better place for this sort of question. The article makes the position of the organization clear, and appears (although I've not checked everything) to be adequately sourced - see WP:FRINGE for the relevant guideline. Tevildo (talk) 22:57, 19 December 2015 (UTC)

Article is going through AfD, discuss any issue there.--Bickeyboard (talk) 18:02, 20 December 2015 (UTC)

December 20

Electrochemistry of rust restoration by electrolysis

There's a method for restoring rusted items made of steel that can be found on many websites. The method involves immersing the item to be restored in a bath of aqueous Na₂CO₃ solution and connecting the item to the negative terminal of a power supply. A sacrificial iron electrode, also immersed in the solution, is connected to the positive terminal. Can someone provide the chemical equations for the reactions involved? Thanks. --98.115.39.92 (talk) 06:43, 20 December 2015 (UTC)

Not precisely, but it sounds like the idea is that the oxygen in the iron(III) oxide is absorbed into the solution, causing the iron to precipitate out (some back onto the original item). The oxygen then in turn is absorbed by the sacrificial iron electrode to cause it to turn to rust (iron oxide). Hopefully a chemist can confirm this and add in the missing details. I suspect that this technique would work a lot better on the initial stages of rust than after it is already flaking off in big chunks. StuRat (talk) 07:16, 20 December 2015 (UTC)

Never heard of a practical way to restore rusted steel but there are definitely chemicals and sacrificial electrodes (there z zinc one used in steel evaporative coolers also see galvanizing). I believe large industrial cooling towers use similar chemistry to protect pipes and equipments but I've never hear of it being used to repair rusted parts. There are many things that remove an adhesive oxide to make something shiny again though (i.e. remove oxides of silver and copper can be done chemically but it takes the metal with it). --DHeyward (talk) 23:21, 20 December 2015 (UTC)

Rust converter is to prepare before applying the Primer (paint). It is passivation (chemistry), only. The much rust is removed, the better it works. When the rust converter finisted it is being removed by washing and cleaning, before the primer is applied on a dry surface. Phosphoric acid and citric acid in coke can be used to passivation a rusted coffee mill. Coffee for espresso machines with integrated grinder is prepared with an oil film. The oil films also helps to stop the rust on the steel parts of the mill, when the oil is beeing transfered by touching the parts. --Hans Haase (有问题吗) 01:10, 21 December 2015 (UTC)

Snoring

Why do I only snore when I am asleep? Why don't I do it all the time? Is there any benefit to snoring?KägeTorä - (^影_虎) (もしもし！) 12:54, 20 December 2015 (UTC)

The website of the British Snoring & Sleep Apnoea Association has lots of information. Alansplodge (talk) 13:04, 20 December 2015 (UTC)

Thanks. Perfect answer. KägeTorä - (^影_虎) (もしもし！) 13:11, 20 December 2015 (UTC)

Ageing of heart

When does human maximum attainable heart rate start to decline? Is it at age 26? Or 30? — Preceding unsigned comment added by 2A02:C7D:B91D:8000:F968:F108:86EC:A569 (talk) 14:01, 20 December 2015 (UTC)

When I look for details, I find things like this - which references three separate studies, producing three different formulae:

1. The "usual" formula: MHR = 220 - age
2. Tanaka in 2001 looking at a broader age distribution: MHR = 208 – 0.7(age).
3. Gellish in 2007: MHR = 207 – 0.7(age) with a p value of <0.001.

The thing is that none of these studies suggest a peak. They are predicting that MHR is largest at birth and declines fron then on.

That finding seems unlikely - and I very much doubt they did stress testing on little children and newborns. However, I'm also pretty sure they tested people below the age of 26 and over the age of 30 - and none of them reported a peak between those ages.

So I'm doubtful of your premise. SteveBaker (talk) 14:34, 20 December 2015 (UTC)

My guess would be sometime in the late teens when the heart and the organs it supplies are mainly fully grown, but I hope someone else can find some studies to verify or refute this. Dbfirs 16:44, 20 December 2015 (UTC)

On the other hand, smaller animals have faster heart rates - maybe that's true of children & babies too? SteveBaker (talk) 19:31, 20 December 2015 (UTC)

Yes, and the formulas support that. Pediatricians need to know when a baby's heart rate is too fast, so they would have more specific figures, by age, such as these: [10]. StuRat (talk) 19:51, 20 December 2015 (UTC)

Those are way below the figures that the formula gives, but they are averages, not maximum heart rates. My intuition is supported by this article from the Cleveland Clinic, but perhaps someone can find some relevant research? Dbfirs 09:06, 21 December 2015 (UTC)

I thought those tables were mainly for calculating aerobic and anaerobic thresholds and were guidelines. Older people reach anaerobic rates at lower heartrates and the that rate was set at 80% of maximum. There are are studies of EKG by age and how the various peaks spread out as a person ages. A "normal" EKG at 80 would be a concern for a 20 year old even at the same heart rate. The sharpness of the peaks, their distance in time and other variables are all part of how the heart functions. Anecdotally, as I understand it, one of the benefits/dangers of pediatric cases is that they can continue exercising beyond where the imbalance of electrolytes would stop an adult (I think it's similar is small animals like rabbits). A child can jog to death from electrolyte imbalance (adults usually have an underlying heart/artery condition if they die during physical exertion and their skeletal muscles cramp before their heart does). --DHeyward (talk) 23:12, 20 December 2015 (UTC)

Electronics in ovens

Are there electronic devices that can be placed inside ovens, for measuring temperature or humidity wihtout opening the oven?--Jubilujj 2015 (talk) 19:24, 20 December 2015 (UTC)

The way temps are normally measured is by placing a temperature probe (thermistor) in the oven, that doesn't have any electronics in it, but just varies electrical resistance as electricity passes through it: [11]. The wire passes through a small port (hole) to outside the heated area, where electronics are then used to convert the electrical resistance readings into readable form and display them (or to control the temp settings, say by turning the oven down once it reaches cooking temp).

Also note that humidity can be measured by sucking out a small bit of air. I have a microwave oven that does this, but it seems rather unreliable as the humidity varies dramatically in and around the food. And also consider that the temperature alone isn't the only issue that's bad for electronics. There's also splattering grease, etc.. So, best to keep the critical electronics out of the oven. StuRat (talk) 19:37, 20 December 2015 (UTC)

Ours has a thin wire that doesn't significantly impede closing the oven door or getting a good seal. The electronics can sit a few feet away on the countertop and reports temperature and elapsed time - and goes "BING!" as needed. I haven't seen one that measures humidity...but similar principles apply. SteveBaker (talk) 19:49, 20 December 2015 (UTC)

See thermocouple. Two dissimilar metals will create a measurable voltage and can be very accurate. Only the wire needs to be in the oven and it's well below the melting point. Note, that the Peltier effect is used to also drive a voltage on the same junction and forcing a temperature. This is how active cooling is accomplished (those 12DC fridges with no compressor or active heat-sinks on CPUs). I think metallic heat transport makes passive Peltier junctions impractical. Microwave ovens I believe use changes in the cavity impedance matching to determine heating profiles. As water changes phase, the impedance match changes which the micro-controller detects and responds. There might be other types though that don't create field discontinuities though. --DHeyward (talk) 23:01, 20 December 2015 (UTC)

See [12] for measuring temperature. Measuring humidity is not so easy - for a commercial oven you can use something like this but I would imagine it's rather expensive. Richerman (talk) 23:16, 20 December 2015 (UTC)

There is an interesting article about measuring humidity in ovens here. Richerman (talk) 23:27, 20 December 2015 (UTC)

Are you asking just out of curiosity, or is there something you're trying to do? --71.119.131.184 (talk) 13:41, 21 December 2015 (UTC)

Pistol Star magnitude

What is the absolute magnitude of the Pistol Star? I wasn't able to navigate to the full chart that's given in the "list of stars about 30000 ly distant please" section from December 16 (every link I checked failed to download), and I couldn't find any reliable online resources unambiguously giving the figure. Several pages claimed that it was -14.2, but all were unreliable (typical example). I tried searching for <"Pistol Star" "absolute magnitude" 14.2> and found this number appearing on the bottom of page 11 of [13], obviously a reliable source, but I don't know what the authors are talking about in this section. Nyttend (talk) 22:55, 20 December 2015 (UTC)

It should be on one of our Lists of stars. I don't think H-R diagrams even go above magnitude -10 and it would take over 40 of those already rare stars to reach -14.2. So that's bright. Sagittarian Milky Way (talk) 22:59, 20 December 2015 (UTC)

There are many different ways to calculate absolute magnitude. Do you mean the absolute magnitude in visual wavelengths, or the absolute magnitude for all wavelengths? Since almost all of the Pistol Star's radiation is ultraviolet, there is a big difference between the two.

Let's take the visual magnitude first. Our article says that if galactic dust did not exist, the star would appear as magnitude 4 for observers on Earth. The star is 8000 parsecs away. By doing some math, we find that the star's absolute visual magnitude is 4 - log(8000^2/10^2)/log(2.51188) = -10.5.

Let's now consider the bolometric magnitude, which includes all wavelengths. Our article lists the star's luminosity as 1,600,000 solar luminosities. The Sun's absolute bolometric magnitude is arbitrarily set to 4.75, according to our article on absolute magnitude. Doing some math, we find that the Pistol Star has an absolute magnitude of 4.75 - log(1600000)/log(2.51188) = -10.8. --Bowlhover (talk) 01:02, 21 December 2015 (UTC)

I think the 14.2 figure in the arxiv paper is referring to a different star, LBV 1806-20. --Amble (talk) 01:15, 21 December 2015 (UTC)

December 21

Why did predators evolve??

It seems odd that predators evolved. What's the point? Non predators seem to do just fine so I'm not sure why there was ever a demand to predate other species (and possibly your own)

Was it just a fluke or something. — Preceding unsigned comment added by 80.195.27.47 (talk) 00:35, 21 December 2015 (UTC)

Every creature is a "predator", in that every creature has to eat. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:45, 21 December 2015 (UTC)

The way I learned things, biologists classify life forms into autotrophs and heterotrophs - and in that scheme, many life forms are not "predators." A moss, for example, is a life form that is not a predator. A moss generates its energy by photosynthesis; and it retrieves other nutrients by consuming non-living material like air, water, and minerals. A moss could be said to be the pinnacle of evolution, exemplifying noninterference and self-sufficiency; and it would probably hold the high ground in any moral or ethical debate. But, for nearly every ecosystem that sustains moss, there exists some niche life-form that eats the moss, getting energy and nutrients without having to expend the effort to generate its own sustenance. This is such an efficient way to gather dietary needs that those moss-eating life-forms have surplus energy to evolve more sophisticated traits and behaviors. For every advantage the moss evolves, the moss-eater gains; and for every advantage that the moss-eater develops, it self-limits by over-eating its sustaining food-supply. This is the standard trophic model of population dynamics, which tends to cause predator-prey populations to mutually oscillate around a stable equilibrium. So - as much as we can answer a "why" question in evolutionary biology: predators evolve because the natural mathematical dynamics of a system are maximally stable when there is a trophic relationship. By application of the weak form of the anthropic principle, that which we observe in nature is probably going to be the most-likely scenario, which would be the maintenance of a stable equilibrium. Nimur (talk) 02:53, 21 December 2015 (UTC)

Strictly speaking, there are no predators. Merely food that moves around, hides from you and capable of defending themselves. Did I mention that you are food too? 175.45.116.66 (talk) 01:01, 21 December 2015 (UTC)

The essential point to make here is that _everything_ is "just a fluke or something". There is no goal to evolution, there is no progress towards anything, it's not looking for an optimum solution to a problem (or, if it is, it found it with the prokaryotes, but it didn't stop there). "Survival of the fittest" is a very misleading phrase - "survival of the adequate" would be better. I know this is not going to be a popular suggestion, but you could do worse than read Full House, bearing in mind that Stephen J Gould has many critics. Tevildo (talk) 01:42, 21 December 2015 (UTC)

But is this also what God intended, as he created all life? Especially since he has no predators. — Preceding unsigned comment added by 80.195.27.47 (talk) 08:54, 21 December 2015 (UTC)

Define "God". ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:49, 21 December 2015 (UTC)

There is no scientific basis for "Intelligent Design." Therefore, there is no way to ask "Is that what God intended?" As with everything, if you start getting into what God wants, you will do nothing more than create groups of people who will eventually feel that what God really wants is for them to kill each other. 209.149.113.52 (talk) 14:09, 21 December 2015 (UTC)

The bottom line is that predators exist because prey that needs to be eaten exists. For every living thing there exists at least one other living thing that eats it - this applies equally to whales and pond-scum. Roger (Dodger67) (talk) 11:34, 21 December 2015 (UTC)

I suppose, in a way, this applies to Apex predator, but not in the usual sense of prey. Dbfirs 11:58, 21 December 2015 (UTC)

Indeed - apex predators generally end up as dinner for bottom feeders. Roger (Dodger67) (talk) 12:04, 21 December 2015 (UTC)

• As Tevildo said, the basic error in the OP's premise is the idea that evolution has a point. Features evolve because they improve the chances of surviving and reproducing, not because they have a point. Looie496 (talk) 12:48, 21 December 2015 (UTC)

Vitiligo

In reference to the condition Vitiligo. My understanding is that it effects the pigmentation of the skin. Does this differ by race? More specifically, would the affected skin of a Caucasian person turn black, while that of an African American turn whiter?

Thank you for your assistance. I am new to Wikipedia and I hope that I am using this forum correctly.

David L Boca Raton, Florida — Preceding unsigned comment added by 99.10.176.177 (talk) 04:03, 21 December 2015 (UTC)

See our article Vitiligo. The condition is a partial lack of pigmentation. As such it results in a lightening of the skin. The article contains pictures of both black and white sufferers. Rojomoke (talk) 05:48, 21 December 2015 (UTC)

But note that the lighter the rest of the skin, the less noticeable it will be. StuRat (talk) 08:07, 21 December 2015 (UTC)

Does libration cause tidal effects ?

...such as tides in liquid, and tidal heating in rock ? StuRat (talk) 08:06, 21 December 2015 (UTC)