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May 25

Can sea water be purified and made into fresh water?

There is more water than land on this planet, Earth. And yet, some people complain that there is not enough fresh water. Now, I know sea water is not drinkable. But, water can be purified by various ways - reverse osmosis, distillation, de-ionization, filtration. And water can be collected from the rain. Earth is a very watery planet. Humans already collect sea salt from the sea. Why not the water as well? 50.4.236.254 (talk) 01:23, 25 May 2017 (UTC)

1) It takes a lot of energy and/or expensive facilities to desalinate the water.

2) It takes money and infrastructure to distribute that water inland.

Collectively, the result is that rich nations can do this, but not poor nations. As for collecting rain, they do this, but it doesn't always rain in all places. Large cisterns are needed to survive multi-year droughts, and those aren't always practical. Then the flooding carries soil inland, where it can nourish plants there. StuRat (talk) 01:25, 25 May 2017 (UTC)

As for collecting rain, the problem is that it falls over a large area. So in many places the most efficient way to collect it is to let the water flow naturally into or over the ground until it reaches a river, which can then be dammed to create a reservoir. This is done in many places. (Added later: Obviously there are also many places where it won't work. For example, maybe the terrain is the wrong shape for the water to flow to a suitable location for a reservoir, or maybe the climate is so arid that the water evaporates before it can be collected.) --69.159.60.50 (talk) 21:55, 25 May 2017 (UTC)

Desalination of seawater / ocean water is actually pursued on a large scale in places where electric power is available but fresh water is scarce. Our desalination article describes the technological approaches used; in a nutshell, they are distillation and reverse osmosis, both of which the OP has already mentioned in the question. Here's a good list of Desalination facilities. --Dr Dima (talk) 03:06, 25 May 2017 (UTC)

There are two problems with water supply. One is that in some areas there just isn't enough to do everything that the people want to do with it. If they are rich enough, desalination is an option - though it is usually cheaper to pipe it in from further away. In other areas, there is plenty of water - but it isn't safe for people to drink. That is the real problem today - because it kills large numbers. Wymspen (talk) 14:08, 25 May 2017 (UTC)

• Reverse osmosis requires a pressure differential of about 50 psi, which we supply using pumps driven by electricity. But this pressure is equivalent to about 150 feet of rise. That means that desalinated seawater delivered to a town 150 feet above sea level is twice as expensive as that delivered to a town at sea level. So San Diego California may be able to use desalinisation but Reno cannot, even ignoring the cost of the pipeline. -Arch dude (talk) 15:41, 25 May 2017 (UTC)

Water purification is Wikipedia's article about large scale, municipal water purification. The article Desalination describes methods for extracting potable water from sea water. Blooteuth (talk) 16:37, 25 May 2017 (UTC)

You can extract pure water straight out of the atmosphere. The theoretically minimum energy required is then the Gibbs energy difference between the water vapor at the actual relative humidity r and at 100% relative humidity, which is -N k T Log(r) where N is the number of water molecules and T the ambient temperature. Count Iblis (talk) 22:04, 25 May 2017 (UTC)

Soil formation on the bank of the Nile river

Some time ago, I asked on the Humanities desk about the Fertile Crescent. The responders seemed more focused on rejecting the claim that the Fertile Crescent is a desert, even though I looked at the provided pictures and saw desert land. One person pointed out that the bank of the Nile river has soil and flooding, probably due to the seasonal tides, so it allows plant colonization. But, that still leaves a mystery for me. How can the Nile river bank be fertile while a sandy beach seems so barren? How is the soil formed in the first place, thereby allowing plant colonization on land? 50.4.236.254 (talk) 01:32, 25 May 2017 (UTC)

Plants have a lot to do with it. Many plants can't take salt-water, so don't grow on ocean beaches. Also, the major waves and tides on ocean beaches are rough on plants. But river banks tend to be more gentle, allowing plants to grow roots there, which then retain the soil which would otherwise wash downstream. StuRat (talk) 01:54, 25 May 2017 (UTC)

If you want some additional reading on the Nile, Wikipedia has an article titled Flooding of the Nile which is sadly a bit brief, but hints at some importance including the deposition of silt from upstream sources, an important source of nutrients. The Wikipedia article titled Ancient Egyptian agriculture has more information. This brief article from the Smithsonian Institution also discusses the importance of the nutrient-rich silt carried by the Nile from volcanic sources further south. This article at Britannica discusses the Nile Valley soil formation in more details. this book hints at the importance of fresh alluvium from the Nile inundations. This article is a rather detailed survey of modern Egyptian agriculture, with a focus on the soils of Egypt. If you really wanted to get detailed on the soil science this paper looks like a good launching point. I hope some of that reading helps explain things. --Jayron32 03:41, 25 May 2017 (UTC)

This makes me happy. :) 50.4.236.254 (talk) 04:27, 25 May 2017 (UTC)

How did the common people come to define "organic" to mean "without pesticides"?

There was one time when I asked my chemistry instructor about the meaning of the term, "organic". He said, "comes from life". I didn't get it, because then I wondered whether my fruits and vegetables in my refrigerator and on my table were "organic". They came from life, so I figured they must be organic. Later, I found out that "organic" meant "without pesticides". How did the common people come up with this definition? In terms of agriculture, if a large conventional farm borrows "organic" farming practices for better environmental management and increased yield, then has the farm suddenly changed into an "organic farm"? And in terms of pesticides, are large herbivores (deer, rabbits) considered "pests" too? The farm basically grows a lot of food intended for human consumption. But, given that the plants occupy a significant amount of land, and that the plants are edible, it stands to reason that hungry deer and rabbits and field mice would happily munch on the plants, reducing yield. Also, these large pests are vertebrate mammals, so they may be very phylogenetically related to humans, making it harder to treat by pesticide poisoning. I mean, they may be killed, but if a poison intends to kill them, the poison can also kill humans due to the shared biology. 50.4.236.254 (talk) 04:54, 25 May 2017 (UTC)

Organic in the broader biological sense and organic in the Organic food culture sense are not related. It's like how when real doctors use the word "medicine," it's a very different word from when homeopaths use the term. You can read more about the disadvantages of organic farming in our article on the subject. Ian.thomson (talk) 05:01, 25 May 2017 (UTC)

There's a significant flaw in that article: the word "recent". First it's undefined, a weasel-word. Second, this concept has been around for well over 50 years. It was referenced in a Stan Freberg recording called The United States of America Volume One: The Early Years - a satirical history recorded in 1961, in which he has an Indian trying to persuade Columbus to eat some "organically grown vegetables." The casual use of that term indicates it was well-established by 1961. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:26, 25 May 2017 (UTC)

EO says the meaning "free from pesticides and fertilizers" dates to at least 1942.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:28, 25 May 2017 (UTC)

Organic does not mean without pesticides. See Organic farming#Pesticides. Pesticides used in organic farming can have additional safety concerns, as it is prohibited to process them from their "natural" state to be safer. 91.155.195.247 (talk) 05:06, 25 May 2017 (UTC)

• It is important to note that words, in different contexts, can have different meanings, and that is OK, and completely normal and how all languages, including English, works. So, in the context of Chemistry, organic means "chemistry of carbon"[2] and in the context of farming, it means "grown without the use of man-made chemicals or GMOs".[3] Some people get pissy about this, and I don't know why, because they can happily carry other words in their brains that have different meanings in different contexts. "Organic" is not special nor difficult in this regard. --Jayron32 12:47, 25 May 2017 (UTC)

Chemists worry about chemophobia, I think. shoy (reactions) 13:27, 25 May 2017 (UTC)

• Look at the history through the Soil Association. This goes back to WWII, their first certification for organic farms was in the mid '60s. Andy Dingley (talk) 13:17, 25 May 2017 (UTC)

• According to our organic food article, this usage was originated by Lord Northbourne in a 1939 book, based on his conception of "the farm as organism". Looie496 (talk) 13:54, 25 May 2017 (UTC)

• Think of "organic" as meaning "100% organic". So, if even a tiny portion of the chemical residue on the skin was made in a lab, that's not "organic". However, there are organic pesticides, like vinegar: [4]. Lab-produced pesticides have a history of being dangerous to people, however, with Round-up being the latest.

• Large herbivores can be kept out by non-chemical means, like fences, or dogs to chase birds away. StuRat (talk) 14:47, 25 May 2017 (UTC)

Thank you for giving me an opportunity to shit on a common chemophobic claim: "organic" pesticides can be toxic as well. See pyrethrin for example. Someguy1221 (talk) 06:48, 26 May 2017 (UTC)

That " as meaning "100% organic"" claim is sheer OR, matching neither the chemists' definition, nor the Soil Association's. Andy Dingley (talk) 15:55, 25 May 2017 (UTC)

This isn't about how chemists define organic, it's about how food consumers do. StuRat (talk) 16:23, 25 May 2017 (UTC)

The US Food and Drug Administration has a set of standards that define what can be labeled "organic" in the United States[5]. These standards have nothing to do with whether the product was treated with a substance "made in a lab". And yes, some synthetic pesticides are allowed on organically labeled food, as well as a variety of non-synthetic pesticides, some of which are quite dangerous to humans and/or damaging to the environment, such as boron, copper sulphate, and rotenone.[6] CodeTalker (talk) 22:12, 25 May 2017 (UTC)

The OP's question may be more suitable for the Languages reference desk. The chemistry teacher's answer "organic means comes from life" can be challenged in the case of Urea, an organic compound now synthesized from inorganic starting material. The common people did not come up with a definition of "organic" to be used as a marketing category for farm products that often carry a premium price or are less superficially attractive; this usage is agenda driven, see this outline. To be marketable as a Pesticide, a product ideally harms only small pests that cause harm and elicit no sympathy. For control of animals larger than an insect with which one might feel empathy, a humane person may prefer to employ an Animal repellent instead of a lethal biological agent that is predictably destructive to humans, their pets and the enviranment. Blooteuth (talk) 15:16, 25 May 2017 (UTC)

The OED has literally dozens of different senses of the word organic, many of them obsolete, but the OP might be interested in the definition for chemistry (first cite 1822): " Originally: relating to or designating compounds which exist naturally as constituents of living organisms or are formed from such substances (all of which contain carbon and hydrogen). Later: of, relating to, or designating any compounds of carbon (other than certain simple compounds such as oxides, carbides, carbonates, etc.), whether of biological or non-biological origin", and for farming (first cite 1942): " Of a method of farming or gardening: using no chemical fertilizers, pesticides, or other artificial chemicals. Also designating a farmer or gardener utilizing such a method, or a farm on which the method is employed.". Dbfirs 05:52, 26 May 2017 (UTC)

"Organic" refers to running the farm as an organism, where crops are rotated and animals are part of the system: cows help refresh fallow soil, chickens get rid of weeds and bugs, pigs dispose of waste. It is in contrast to specialized farming, where only one crop or animal is raised, hence the need for artificial fertilizers and pesticides. Organic standards limit the use of pesticides, which is one of the reasons people buy them, but not why they are called organic. TFD (talk) 06:27, 26 May 2017 (UTC)

Human size and power of blows, strikes, kicks

Is there an optimal average size for maximum striking power? The rationale is that although you'll need mass, maybe from a certain mass on your speed start going down. Would then someone be stronger but lighter due to this higher speed? --Hofhof (talk) 10:41, 25 May 2017 (UTC)

The evidence from boxing and shot-putting would I say indicate otherwise. Anyway do you really think anyone could stand up to being whacked by the tail of a whale? I guess there is a limit eventually but it must be pretty huge. Dmcq (talk) 11:33, 25 May 2017 (UTC)

Yes, but for the tail of a whale the rule still applies. Maybe other animals are much faster, even if less massive, and can hit harder. Many other factors also apply, starting by the fact that claws would be much more damaging than the smooth skin of a whale.

Where's the evidence from boxing and shot-putting? Has this been analyzed scientifically? AFAIK, the athletes are massive, but no one is like 400 pounds, which would prove my point. Hofhof (talk) 11:41, 25 May 2017 (UTC)

Sorry I didn't know you were trying to prove a point. Dmcq (talk) 12:20, 25 May 2017 (UTC)

I mean, it's a hypothesis, it can be refuted, or not. — Preceding unsigned comment added by Hofhof (talk • contribs) 13:41, 25 May 2017 (UTC)

We have had 400 pound wrestlers, even up to 800 (Happy Humphrey): [7]. However, if we move up to 1000 pounds, you have a point. The limits may be more due to them dealing with their own weight, than the relative effect of blows. At 1000 lbs the human body may be seriously injured by falls, and just moving around takes a huge effort. Of course, that's because the design of the human body doesn't support that type of weight well. Larger animals can manage that weight just fine. When fighting a much larger wrestler, the strategy should be to hit and run, and don't allow them to hit you or get hold of you. Just let them tire themselves out chasing you. StuRat (talk) 14:54, 25 May 2017 (UTC)

Well, when fighting a much larger wrestler, you probably do the same thing as when fighting a smaller man - you follow the script. --Stephan Schulz (talk) 12:04, 26 May 2017 (UTC)

What matters is if you can do these exercises. Count Iblis (talk) 19:27, 26 May 2017 (UTC)

16 Psyche on earth

If 16 Psyche, the metal asteroid, was somehow to be gently brought to earth (not a giant crash), would the mass be enough to disturb the earth's orbit? What changes in position and duration would occur? -- SGBailey (talk) 13:54, 25 May 2017 (UTC)

• If we assume that the asteroid magically teleports onto the Sahara without any immediate change to the Earth's rotational motion except the added mass, none because mass does not matter for orbits (also, 16 Psyche has a negligible mass compared to the Sun's). On a fundamental level, this is linked with the equivalence principle (saying that the "mass" used for inertia in Newton's second law and for gravity in the gravitation law).

However, if the asteroid is somehow towed towards Earth, surely while it is in transit close to Earth it would attract it and hence modify its orbit. By how much would depend of how long the towing takes etc., though I would guess "not much". Tigraan^{Click here to contact me} 14:28, 25 May 2017 (UTC)

• Agreed. The Earth's mass is some 200,000 times more, so any effect would be minimal. StuRat (talk) 15:01, 25 May 2017 (UTC)

From our archives, I dug out: August 2012, "What If..."

“ We get this question a lot. If I may quote myself, from March of 2012, when I quoted myself from a similar question in September of 2011: (I have taken some liberties to modify the quote to increase relevance to the current question):

"The answer to this type of physics question always depends: how would [the asteroid magically transport to a position near Earth]? If you can specify that, we can follow through with the consequences by solving the equations of motion for the Earth-Moon[-Asteroid] system.

For example, if you hypothesize that a giant comet large and fast enough to change the [asteroid's orbital position] impacted [16 Psyche], .... well, we would need to calculate the effect that such a large comet has on the orbits of Earth and everything else in the solar system, too. We could solve that problem by setting up an n-body problem to model the solar system, including Earth, Moon, Sun, and other planets; and we would use perturbation theory to study how sensitively the system reacts when we add in a new comet on a course to impact the [asteroid]. The results are difficult to compute, but this can be done in a reasonable amount of time with a reasonable amount of effort.

...

On the other hand, if you just want to make something up, "just imagine" that the [asteroid] magically changes its [orbit], all bets are off. We can't meaningfully speculate what consequences follow when one law of physics breaks "because of magic." Anything could happen. Everything we know about the way the [asteroid] orbit couples into the Earth's rotation depends on the rules of physics as we currently understand them.

”

So - does that answer your question? Anything. Anything could happen.

You cannot magically transport mass from one point to another - in any circumstance, let alone in orbital mechanics. It takes a change in energy and momentum to change an orbit - even if the final position has no net motion relative to Earth, and even if the relative velocity exactly equals zero at the moment of contact with Earth. You have to do something to cause the energy and momentum of the asteroid to change; how you do so must be in compliance with these conservation laws, and how you do so would profoundly alter the outcome. The ensemble set of these conservation laws, ostensibly, constitute the single absolute most important-est and most inalienable part of our understanding of our physical universe. If you try to bend them for the purposes of the hypothetical, all you get is the principle of explosion - it is absolutely meaningless to proceed from a logical falsehood.

To put the absurdity of the original question in to terms that you might be able to explain to your kids: "Imagine that you knocked a brick off of the top of the roof of a very tall building, and the brick dropped down towards the ground. But, instead of falling down really fast and impacting the ground, the brick just remained stationary and rested on the ground and didn't move. (Not a giant crash). When it hits the ground, does the brick shatter on impact?" Yes? No? Use your imagination! The question asks about a situation that doesn't even make sense!

Nimur (talk) 15:06, 25 May 2017 (UTC)

If Asteroid mining ever becomes feasible, 16 Psyche is believed to contain 1.7×10¹⁹ kg of nickel–iron, which could supply the world production requirement for several million years. Planetary Resources and Deep Space Industries are companies that are attracting investors to their plans for asteroid exploitation though this speculative list of target asteroids does not include 16 Psyche. The proposal of towing that 200 km (120 mi) diameter body to a gentle (!) touchdown on Earth is so daunting that we can only consider an exploitation scenario where manageable amounts of ore are first extracted and processed on the asteroid before they are shipped to Earth. Long before change to Earth's orbit becomes evident, this activity would have political repercussions on Earth (now addressed by the UN Office for Outer Space Affairs) and likely alter the trajectories of other asteroids with unforseeable consequences. Blooteuth (talk) 16:23, 25 May 2017 (UTC)

I remember when you first posted that, Nimur. I liked it then and I like it now, but please note that the OP said nothing about magic; they only suggested that its landing be non-catastrophic, which brings up any number of real world possibilities that enable controlled descent (albeit difficult given the proposal). Matt Deres (talk) 16:29, 25 May 2017 (UTC)

Indeed - and if he were to precisely explain the mechanism of mass transference - by describing a collision, or explaining a rocket-powered scheme to change the trajectory of the planet - I would be very happy to start pointing to real and useful resources that would help explain the outcome! One of my favorite books is To Rise From Earth: An Easy-To-Understand Guide to Spaceflight, and it shows the reader how to set up the basic problems in orbital mechanics. That book is written for a technically-inclined, but non-rocket-scientist, audience.

I'm sort of keen on running the math myself to figure out how much energy you'd have to expend if you attached rockets and conducted a Hohmann-transfer for the entire asteroid. I'm sort of curious whether we're in the ballpark of the order of magnitudes achievable with chemical rockets, or if we'd really need to dive into deep science-fiction to make it happen.

Nimur (talk) 22:16, 25 May 2017 (UTC)

Even if by some Non-Magical Magic the 200 km sized object was to land on Earth with zero relative velocity, it would not stay still. Rather, it would collapse under its own weight: the max mountain height on Earth is on order of 10 km, because taller objects produce pressures at their base which exceed the pressure of elasto-plastic transition in the material. Two things will happen: (a) the object will collapse and spread out as a pancake, and (b) the continental crust will deform and sink and/or flow outwards from the location of the touchdown. This is a Bad Thing. Dr Dima (talk) 17:27, 25 May 2017 (UTC) Also of note, the continental crust average density is 2.7 g/cm3, about a third of the typical Fe-Ni alloy density. There is therefore a distinct possibility that some (or all) of the Psyche material will end up sinking straight into the Earth mantle and towards the core. Oops. Dr Dima (talk) 17:55, 25 May 2017 (UTC)

Agree that isn't good, nevertheless, for two-body problems Kepler's third law assumes M>>m, where here M is the Sun's mass and m is the Earth's mass, and this assumption holds true when 16 Psyche's mass is added as well. However, more precise and accurate models do not make that assumption such that both M and m affect their orbital period and separation. Solar mass M_☉ is about 332946 M_E (Earth mass) (I've a textbook that says about 300,000 times so StuRat is not too far off the mark above). Currently, our article on the Sun shows that we know the Sun's mass to within about one M_E, hence any simulations of this are not going to be able to include mass changes smaller than that. Still, I am certain that with conservation of angular momentum we can determine how much the year is shortened by some tiny amount even if it's not measurable. This is because bringing in an object from beyond the Earth's orbit increases its angular speed (much like a skater spins faster when they pull their hands in) and so the interior orbital periods are shorter consequently and that any accretion of mass on Earth simply increases its gravitational acceleration towards the Earth's and Sun's common barycenter and that brings about a faster and tighter orbit (thereby conserving momentum too). This imaginary barycenter is the system's mass center which has to move closer to the Earth as their mass imbalance is reduced. Conservation of angular momentum for a mass m on a string of length r requires that (mr^2)/T be some constant where T is the orbital period. Thus given this constant the new radius is r=sqrt(constant T/m) where m is the new mass and T the new period which is the parameter we want to solve for by eliminating r using the equation for two orbiting bodies (I already linked to it). To further simplify that work, note that we have to include the mass and momentum of the asteroid body as it nears us. So the net mass m cancels and we really only have r=sqrt(constant*T) for the constant ((r^2)/T). Also, one must assume a greater precision than we have for the Sun's mass (by appending a spherical cow of zeros beyond the current precision that we have) to get different mass totals, but we are not interested in their absolute values anyway, only the magnitude of relative change that occurs for these parameters. @SGBailey: I'm not a physicist, but I did take this stuff in high school and college like decades ago... thus some of the things I learned have stuck with me more than others, but I hope this helps more thoroughly answer your question. -Modocc (talk) 21:47, 25 May 2017 (UTC)

@Dr Dima: I agree what you say is true, but ... well, a while ago I asked about mantle hotspots and learned that ordinary granite is a rheid. So I realize now to take some of these terms about plastic flow with a grain of... caution. When you say that the asteroid would collapse and cause the crust to buckle, are you talking about a geological timescale, or something more dramatic? Wnt (talk) 23:46, 25 May 2017 (UTC)

@Wnt: This is not really an appropriate place for original research, and I don't have solid literature to cite because the whole scenario is obviously hypothetical. However, since pressure wave travels at least with a speed of sound, the material near the point of contact between Psyche and Earth will start to yield within seconds if not faster. The whole of Psyche will then proceed in a nearly free fall for at least a while, until the pressure force produced by compression and heating of both crust and asteroid material will sufficiently exceed the Psyche weight to decelerate and stop the Psyche fall. This will be followed by a rebound, etc. I think. Dr Dima (talk) 01:27, 26 May 2017 (UTC) (To be clear, when I say "Psyche weight" and "Psyche fall" I don't at all imply that it will behave as a solid. Rather, it will behave more like a blob of liquid, given the pressure values produced). Dr Dima (talk) 01:32, 26 May 2017 (UTC)

BTW, here's another way to look at it. at 100 km above the surface of the Earth (which would be the initial position of Psyche's center of mass, as well as its equatorial plane), a potential energy of 1 kg of iron is mgh = 1 kg * 10 m/s2 * 100000 m = 1e6 Joules. This energy has to go somehwere as the iron falls down to Earth. Heat capacity of iron at room temperature is 444 J / kg K, and latent heat of fusion (melting) is about 1e5 J/kg; so assuming half the energy (5e5 J per 1 kg) goes into heating the iron and half goes into heating air and crust material, the temperature of the Psyche material will, on average, rise by over 1000 K. It will not all melt, but some of it will actually melt, and the rest will be rather unpleasantly hot for a while :) --Dr Dima (talk) 02:41, 26 May 2017 (UTC)

@SGBailey: All else equal, if 16 Psyche's mass was added to the Earth's mass then the year and the semimajor axis distance to the Sun would be shortened by about 0.72 milliseconds and 1.7 meters respectfully. I calculated these from the equation for two orbiting bodies: $T=2\pi {\sqrt {\frac {a^{3}}{G\left(M_{1}+M_{2}\right)}}}$ and $r={\sqrt {T*constant}}$, where the $constant={\frac {r^{2}}{T}}$ is from the conservation of angular momentum of any fixed mass constrained to radii r with periods T. Letting r = a, solving for T gives: $T=(2\pi )^{4}{\frac {constant^{3}}{G^{2}\left(M_{1}+M_{2}\right)^{2}}}$. Also, $M_{1}+M_{2}={\frac {(2\pi )^{2}{\sqrt {\frac {constant^{3}}{T}}}}{G}}$. Therefore, $\left(M_{1}+M_{2}\right)+\Delta M={\frac {(2\pi )^{2}{\sqrt {\frac {constant^{3}}{\left(T+\Delta T\right)}}}}{G}}$ and $\Delta T=T_{2}-T_{1}=(2\pi )^{4}{\frac {constant^{3}}{G^{2}}}({\frac {1}{(\left(M_{1}+M_{2}\right)+\Delta M)^{2}}}-{\frac {1}{\left(M_{1}+M_{2}\right)^{2}}})$. Solving for r instead $\Delta r={\frac {(2\pi *constant)^{2}}{G}}({\frac {1}{\left(M_{1}+M_{2}\right)+\Delta M}}-{\frac {1}{\left(M_{1}+M_{2}\right)}})$. For our Earth the constant is about 7.0915e+14 m²s^-1 (for r=149598023000 m (the Earth's orbit's semimajor axis) and T=31558149.5 s) and gives a total mass 1.9885e+30 kg within the error range given at Solar mass. I then crunched these numbers with WolframAlpha here and here. -Modocc (talk) 07:07, 29 May 2017 (UTC)

It's enough of a difference in Earth's orbit to potentially alter who gets hit by some impact events. :-) --Modocc (talk) 08:15, 29 May 2017 (UTC)

Can hormones be secreted by the endocrine system only?

or it's possible to secrete hormones by another way in the body17:10, 25 May 2017 (UTC) — Preceding unsigned comment added by 93.126.88.30 (talk)

Wikipedia is your friend. Please read endocrine system, juxtacrine signaling, paracrine signaling, autocrine signaling, neurotransmission, and neuromodulation. These articles address the many specific aspects of your question. --Dr Dima (talk) 17:43, 25 May 2017 (UTC)

Part of the problem with definitions like this is that they are not divinely mandated or requirements of law or anything like that; definitions are human created for human convenience and as such, suffer from human uncertainty. Depending on how you establish your terms, you can set up rather obvious answers to questions like this. For example, the common definition of the terms endocrine system and hormone establishes a tautology such that we define the endocrine system as "The parts of the body that produce hormones" and thus hormones as "substances produced by the endocrine system", your question then answers itself in uninteresting ways; because the relationship between hormones and the endocrine system is tautological, there's no possibility that one could answer in the negative; if we should discover hormone tomorrow that was being produced by a part of the body that was not previously counted as part of the endocrine system; that organ would then be an endocrine organ because it is producing a hormone, and that's what endocrine organs do. There are, of course, organs which are part of the endocrine system and also part of other systems because they have multiple functions; for one example, the pancreas produces the hormone insulin, thus is an endocrine organ by definition, but it also produces Carboxypeptidase, which is a digestive enzyme, and thus that makes the pancreas a digestive organ. You can play with the fuzzy edges even more than that; neurotransmitters are not normally considered hormones because they don't use the circulatory system to get around the body, which is one of the sine qua non of hormones, and what makes them different from other secretions. However, there are some compounds, like Epinephrine, which are both hormones and neurotransmitters; but that does NOT make nerve cells that produce it endocrine cells; because when it is used as a neurotransmitter it isn't acting as a hormone. The TLDR version is this: You can't make these categories exclusive for individual components, because then you create contradictions (that is, you can't demand that the pancreas ONLY be part of the endocrine system) and you also shouldn't get too hung up on uninteresting tautologies. Instead, the more interesting use of your brain power is to understand process and relationships, rather than getting hung up on definitions. --Jayron32 13:41, 26 May 2017 (UTC)

Solar and lunar eclipse in Toronto

When was the last time that the City of Toronto observed the lunar and solar eclipses? Donmust90 (talk) 23:40, 25 May 2017 (UTC)Donmust90Donmust90 (talk) 23:40, 25 May 2017 (UTC)

You can work this out yourself by researching at Lists of solar eclipses and Lists of lunar eclipses. --Jayron32 00:39, 26 May 2017 (UTC)

Technically "never" as lunar and solar eclipses never happen at the same time. They are typically two weeks apart. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:47, 26 May 2017 (UTC)

At least! —Tamfang (talk) 08:07, 26 May 2017 (UTC)

Or to nitpick in a different way, never, because cities do not have qualia. --Trovatore (talk) 09:56, 26 May 2017 (UTC)

Often, though not always, lunar and solar eclipses will occur in "pairs" - about two weeks apart. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:45, 26 May 2017 (UTC)

Any lunar eclipse is visible from about half the Earth, so this basically just asks when there was a lunar eclipse when it was night-time in Toronto—which, from the lists linked above, would be February 11 this year. However, to actually observe the eclipse the sky would have to have been clear, and I don't think it was.

For solar eclipses, each one is only visible from a narrow track. This page links to a set of maps of such tracks, each map covering a 20-year period, over a span of thousands of years both past and future. If you look at the 5 most recent maps, [8] [9] [10] [11] [12], you will see that the most recent annular eclipse visible in Toronto was in 1994 (and I remember that that was a clear day, so it was visible) and the most recent total solar eclipse was in 1925 (but I don't know about the weather then). --69.159.60.50 (talk) 15:42, 26 May 2017 (UTC)

There are solar eclipses that don't even have paths. Partial eclipses. Also the penumbras of total or annular eclipses. Those can be 10,000 kilometers wide when the shadow's at the Arctic and equator simultaneously. Or any other time an eclipse is on the horizon and (near) overhead simultaneously. There are even total and annular eclipses that have no path. The centerline never touches Earth's surface and the totality barely touches it leaving a small blob instead of a path. Sagittarian Milky Way (talk) 23:01, 26 May 2017 (UTC)

To look at it that way, there is a perpetual "solar eclipse", because there is always a cone-shaped shadow cast by the moon. When that shadow happens to touch the earth, we call that a solar eclipse. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:40, 27 May 2017 (UTC)

Touch the Earth how? In this graph the eclipse "path" is the fan-shaped blob about the size of Tasmania. The centerline is not on the Earth. (or at least, it's not on the idealized (equatorial radius?) Earth. The gamma is minus 1.0000 Earth radii so it's really close.) The partial eclipse is the gigantic thing that goes from the tropics to Antarctica even though the other side falls on outer space. P.S. the perpetual "solar eclipse" is not perpetual because Earth hides the Sun every total lunar eclipse. Sagittarian Milky Way (talk) 07:24, 27 May 2017 (UTC)

The cone-shaped shadow is always there, and sometimes that cone intersects the surface of the earth. Hence, an "eclipse". ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:14, 27 May 2017 (UTC)

There​ are 3 cone-shaped shadows, the umbra, antumbra and the penumbra. The cones are not always there. If you consider the refracted, red, indirect sunlight of a total lunar eclipse to always make the cone then you should also call total solar eclipses annular since moonscapes can be at least 480,000 times darker whenever eclipsed while total solar eclipse landscapes are only ~50,000 times darker. Even the corona alone is only ~420,000 times darker than the regular Sun (which isn't visible in central lunar eclipses anyway as the naked eye corona can only be about 1.5° wide while the Earth is 2° wide from the Moon). Also the Moon's "umbra" when it's totally eclipsed is several times shorter than when it isn't eclipsed because the Earth is 4 times bigger than the Sun in the Moon's sky. Is it really the same cone if it's 150,000 miles shorter and made by moonscapes so dim as to be invisible to the naked eye? (a Danjon scale zero "black eclipse" which happens after severe volcanic eruptions) Sagittarian Milky Way (talk) 20:34, 28 May 2017 (UTC)

The moon always casts a shadow. Or three shadows, if you will. But it's always there (except during a lunar eclipse, when obviously the sun is obscured by the earth). If you happen to be inside the shadow(s), you'll see an eclipse... even if you're flying through space at the right time and location. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:43, 29 May 2017 (UTC)

That's true. Fun fact: The Moon casts that shadow on an outer planet not too infrequently. It's penumbra is gigantic at that distance (up to hundreds of Jupiters wide) but the annular solar eclipse is so mild the planet getting dimmer probably cannot be detected from Earth. Here's the article. Sagittarian Milky Way (talk) 05:39, 29 May 2017 (UTC)

And to answer the solar half of the original question, the last solar eclipse observed at Toronto was seemingly either Solar eclipse of June 10, 2002 or Solar eclipse of December 14, 2001, both of which occurred near sunset in south-central Canada, and it's possible that one or both of them occurred too late for viewers in Toronto to see them. Nyttend (talk) 12:00, 29 May 2017 (UTC)

No, it was the partial phase (of course) of the partial eclipse of 10/23/14. The Toronto downtown airport weather record says it was clear. Sagittarian Milky Way (talk) 19:48, 29 May 2017 (UTC)

May 26

Mammals that sexually mature later than humans?

What mammals reach sexual maturity later than human beings? I'm counting both the ability to sire/bear offspring and also having reached more or less adult size.Naraht (talk) 02:03, 26 May 2017 (UTC)

The elephant, for one. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:51, 26 May 2017 (UTC)

Great White Sharks may be the latest, possibly as late as 26ish. --Jayron32 02:54, 26 May 2017 (UTC)

Except they're not mammals. But if that's the latest reproductive age of any creature, that puts a boundary around it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:00, 26 May 2017 (UTC)

I don't think elephants is the correct answer. The elephant article does not mention when they achieve sexual maturity but mentions musth, which is not the same thing. Unfortunately I am at work and our connection is very slow so I can view Google results and Wikipedia but not much else. So Google provided the following results when I put in Mammals that sexually mature later than humans and that seems to indicate that humans are the latest. The partial result for the Quora site looks interesting. Then using Google to ask Sexual maturity elephants gives interesting results with this looking good. But exactly CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 07:32, 26 May 2017 (UTC)

Actually, the article on elephants says sexual maturity is at about 9 years for a female, and 14-15 years for a male (several of the larger mammals have a similar difference between the two genders). That does not mean that a 15 year old male elephant would get a chance to mate, as it is competitive and the older, stronger males would dominate. That would imply that male elephants reach sexual maturity later than male humans - but not the females. Wymspen (talk) 11:48, 26 May 2017 (UTC)

I'm surprised that I missed that when I looked earlier. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 12:24, 26 May 2017 (UTC)

Nine-year-old male elephants have been known to mate if all the big males have been killed by poachers. Abductive (reasoning) 17:46, 28 May 2017 (UTC)

Are they less interested in almost menopausal elephants when they start to like girls just like humans? Sagittarian Milky Way (talk) 19:21, 28 May 2017 (UTC)

It seems that female elephants have lifelong fertility http://www.abc.net.au/science/articles/2013/10/28/3874904.htm --Digrpat (talk) 11:58, 29 May 2017 (UTC)

Exocrine system + endocrine system =?

What is the title name for endocrine system + exocrine system? In another language that my friend speaks they are called "secretion system" but in English the term secretion system is different and it is about proteins in Gram-negative bacteria. 93.126.88.30 (talk) 08:08, 26 May 2017 (UTC)

I believe the term glands encompasses both of those and also excludes other systems. --Jayron32 10:52, 26 May 2017 (UTC)

You can call it the glandular system, glandular being the adjective from gland. Wymspen (talk) 15:38, 26 May 2017 (UTC)

How does a creature adapt to city life?

What are the characteristics that a creature must have to live in the city? I presume size is important. Anything too big can easily be spotted by humans. The city has cement, asphalt, and concrete, not soil. I think some plants can slide in among the cracks of sidewalk. There may be parks, separated by tall buildings and desert-like cement floors. And fast-moving objects on wheels with humans inside roam the streets with big, shiny, blinding lights. Then, there are bright lights right next to the moon, so bright that they block out the stars. How do rats survive in the city? What other kinds of creatures can adapt to city life or farm life or face extinction because of habitat loss? 140.254.70.33 (talk) 18:59, 26 May 2017 (UTC)

One obvious example is the Rock Dove, which finds the sides and roofs of tall human buildings just as habitable as the cliffs and caves of its wild habitats.

(But whatever birds lived in the trees that were growing there before the city was built, might be out of luck.) ApLundell (talk) 19:05, 26 May 2017 (UTC)

Rock doves of course would be the common pigeon. The infrequent pure white variety looks very dovey. Sagittarian Milky Way (talk) 07:31, 27 May 2017 (UTC)

Habitat loss is not really about cities, e.g. in the USA our city cores all combined are still tiny compared to the vast expanses in between them. Habitat loss is mostly due to agriculture and deforestation with suburban sprawl playing a much more minor role. Animals that do well living around humans are called synanthropes. We have articles on urban forestry and urban wildlife that describe what sorts of species live around our cities, and you can look in to each of them to see what traits they share in common. Our article on rats explains a lot about how they do so well in some human settlements. Other common urban/suburban animals of North American include squirrels, mice, ground hogs, deer, flies, snails, slugs, ants, mosquito, sparrows, cardinals, blue jays, mourning doves, robins, anoles, geckos, skinks, frogs, etc etc. Tons of stuff lives all around us. See also urban ecology for further reading and references. SemanticMantis (talk) 19:13, 26 May 2017 (UTC)

By my personal observations, Urban foxes are persistent and common in UK towns and cities – driving home through Gosport last week I saw four or five, and had to slow down and flash my headlights at one before it would deign to vacate the carriageway. In the same town's pedestrianised high street, my friend (who lives there) was walking home late one night eating a bag of chips when a fox stopped in front of him, clearly soliciting a handout. When he paused, it walked up to him and tugged gently at his trouser leg, whereupon it was rewarded.

Badgers are also not uncommon in the area (which includes the cluefully named Fort Brockhurst), though they are somewhat shyer and are most often seen crossing cycle paths. (The same friend once cycled into one and broke his wrist – the badger was doubtless unscathed.) {The poster formerly known as 87.81.230.195} 90.200.129.108 (talk) 01:21, 27 May 2017 (UTC)

While some areas in big cities may give the famous impression "the city never sleeps" most areas are in fact almost completely free of human activity during night hours. Animals instinctively use these hours to wander from one green or hiding zone to another. In fact most animals seem to have much better natural planning and mapping capabilities regarding their living area than humans. They know when and where to move savely and unnoticed. --Kharon (talk) 04:16, 27 May 2017 (UTC)

Animals adapted for cliff-dwelling do well in cities. Animals adapted to forest edge and open woodland habitats do well in city parks. Abductive (reasoning) 17:48, 28 May 2017 (UTC)

May 27

Feynman Lectures. Exercises PDF. Exercises 4-1...4-16

I have a general question. In exercises for Lecture 4 a principle "if system is in balance it is reversible machine" is used. But why is it true?
If a reversible machine is balanced it doesn't mean that anything else balanced is a reversible machine.
If Feynman uses this argument, then why doesn't he say that frankly in Lecture 4 (He says only "If we say it is just balanced, it is reversible and so can move up and down")?
But even with this argument there is a problem: at the moment of Lecture 4 we do not know that balanced system is a system without acceleration, because we do not know what acceleration is yet. Therefore, we can't know what a "balanced system" means. So we can't say is the reversible machine in Fig. 4–1 balanced or not at each moment of its operation.

We have:
1) Statement "balanced system is reversible machine" is unproven.
2) Statement "reversible machine is balanced system" is unproven.
3) Statement "if all reversible machines are balanced then all balanced systems are reversible machines" lacks logic. Username160611000000 (talk) 08:10, 27 May 2017 (UTC)

That part isn't quite as clear as the rest, but it does make sense. If you have a "machine" in the classical sense, specifically an inclined plane, with weights on the incline and vertically, then if one end pulls down i.e. it is unbalanced, it is not reversible. Presumably this is in the sense that once the one weight hits the ground, its energy is dissipated and (by conservation of energy) there's no way to reset the whole thing how it was without putting some energy back in. He is taking conservation of energy on blind faith, to be sure. Now, if you have the same machine and it is precisely balanced, then you can push it either way as you like, because, well, I think that's what balanced means. But ... yes, balanced is an imprecise term. After all, a screwdriver can be balanced on its tip, and in theory, you could have it sitting like that and with a push send it one way or the other, yet that is not reversible. The key distinction there though is that the screwdriver doesn't stay balanced. The inclined plane example, in theory, you can give it a little teeny weeny itsy bitsy push, and if it's a perfectly reversible machine, watch it creep down or up, one way or the other, over months and years and whole precessions of the earth, and yet, if you give it a little more push, or push it a little back the same way, it will then go at that new rate the same way. And so you see there that because it remains continually balanced, it never is in the point of giving up its energy, i.e. it does no mechanical work on the weights to get them moving this way or that, beyond what you yourself have put in. Wnt (talk) 20:12, 27 May 2017 (UTC)

Typical revolutions per minute of a fidget spinner

Not a specialised one designed to go ridiculously fast. Just a normal, hand-spun one. What sort of ballpark are we talking? 10rpm? 1000rpm? Amisom (talk) 21:05, 27 May 2017 (UTC)

This is still a very new field of research so there won't yet be much published literature on this particular aspect.----Seans Potato Business 21:57, 27 May 2017 (UTC)

A Fidget spinner is a type of stress-relieving toy. A video of children playing with the toy shows it spins at a rate a child can easily start and stop, apparently similar to a Gramophone record i.e. 16 to 78 r.p.m.. Blooteuth (talk) 22:55, 27 May 2017 (UTC)

A fidget spinner is hand spun to about 1000rpm in this YouTube video (1:06 minutes in). --Modocc (talk) 23:01, 27 May 2017 (UTC)

About 20,000 rpm or more to get failure. Count Iblis (talk) 23:54, 27 May 2017 (UTC)

Is there any pattern to warning symbols?

I see sometimes common warning symbols in orange squares or white diamonds with red outlines or yellow triangles with black outlines or white triangles with red outlines. Is there some situation where one is preferred? Can an nuclear trefoil, for example, be put in any of these?

See the article about [Hazard symbol]s. Their use of hazard symbols is often regulated by law and standards organisations who direct different colors, backgrounds, and borders. The radiation Trefoil symbol was originally majenta on a yellow or blue background but is now internationally recognized drawn in black, see Hazard symbol#Ionizing radiation trefoil warning symbol. See the article Warning sign about national traffic hazard signs. Blooteuth (talk) 22:44, 27 May 2017 (UTC)

See also Globally Harmonized System of Classification and Labelling of Chemicals and GHS hazard pictograms. Also Hazchem used in some Commonwealth countries. Alansplodge (talk) 23:18, 27 May 2017 (UTC)

May 28

If babies are never weaned, then will they be able to digest lactose at later ages?

I know babies are weaned from breastmilk. But what happens if they are never weaned? Will babies continue to feed on breastmilk and be able to digest breastmilk at later ages? 50.4.236.254 (talk) 02:07, 28 May 2017 (UTC)

Most people can digest milk their entire lives. Why would this matter? --DHeyward (talk) 02:28, 28 May 2017 (UTC)

It may be true in D's country, but it is not true in general that "most people can digest milk their entire lives". --69.159.60.50 (talk) 02:40, 28 May 2017 (UTC)

Agreed. Most people of the world live in Asia, and Asians, with exceptions of North Asians, are largely lactose-intolerant. 50.4.236.254 (talk) 03:22, 28 May 2017 (UTC)

Fine, but the question seems to be, if they never stop drinking milk, can they avoid the onset of lactose intolerance? I think the answer is "no", but I'm not really sure, and it's an interesting question. --Trovatore (talk) 03:39, 28 May 2017 (UTC)

I agree I think the answer is no. First, I don't see any reason to think breast milk will make a difference so without ruling it out, I'll let someone else look for any evidence about that. While I couldn't find a source specific placesspecifically commenting on the issue, remember in plenty of places cow milk consumption is fairly common from weaning or before. Most sources like [13] [14] discussing lactose intolerence refer to differing ages of onset etc. They don't say anything about how people can avoid it if they make sure they always consume milk. Note that although people who regularly consume milk may have less symptoms of lactose intolerance [15], according to [16] which is from the dairy industry of Canada, there's no evidence that this is due to increased lactase production and actually they acknowledge they don't know for sure why there seems to be this adaptation, but just that there is evidence does. This doesn't rule out a higher level of lactase production in people who have always consumed milk (nor for that matter that there really is no increased production in people who start to later regularly consume milk even if they lack the various known lactase persistence alleles), still it makes it seem less likely. Nil Einne (talk) 04:26, 28 May 2017 (UTC) 07:04, 28 May 2017 (UTC)

If I'm reading your question right, you're not talking about any old milk (like from cows or goats) but from human breastmilk. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:46, 28 May 2017 (UTC)

There is a specific gene (MCM6) which has the role of switching off lactase production after weaning: it generally kicks in when the child is about four, and had an evolutionary advantage, in that it prevented the older child from hogging the mother's milk, and let the next baby get its share. The mutation which changed Europeans, and some other populations, means that this gene does not work: we continue to produce lactase, so can continue to digest lactose. Without that mutation, the gene is going to switch of lactase production: a child will stop wanting to breast feed because it will start getting bad tummy aches. Wymspen (talk) 10:26, 28 May 2017 (UTC)

Actually re: my answer above, I intentionally didn't link to or check out our articles because I assumed the OP had read them. It seems this was a mistake and I'm now assuming they didn't. While Lactose intolerance isn't that helpful (that I noticed), we also have an article Lactase persistence which specifically covers the issue "While a variety of genetic, as well as nutritional, factors determine lactase expression, no evidence has been found for adaptive alteration of lactase expression within an individual in response to changes in lactose consumption levels.[1]". I haven't checked the source, so I'm not sure if it specifically comments on continuous lactose consumption, I think the evidence is now fairly strong that it's unlikely it will ward of the development of lactose malabsorption/intolerance.

About your comment, I believe we covered the question of why lactase nonpersistence is the norm recently. While it's possible it did provide an evolutionary advantage in some species including humans, for the reasons you stated, I would be careful about assuming that this is a significant factor. Lactase nonpersistence seems to be the norm in most mammal species so it's not clear that preventing older offspring from hogging the milk would be a significant factor.

Nil Einne (talk) 11:32, 28 May 2017 (UTC)

Reading a bit more, I see I missed this part:

Multiple studies indicate that the presence of the two phenotypes "lactase persistent" (derived phenotype) and "lactase nonpersistent (hypolactasia)" is genetically programmed, and that lactase persistence is not necessarily conditioned by the consumption of lactose after the suckling period.[11][12]

Nil Einne (talk) 11:36, 28 May 2017 (UTC)

Decades ago I read a book about a European's life among the Inuit. It may well have been "Arctic Adventure" by Peter Freuchen. In it the author told of a custom among the local Inuit of mothers continuing to breastfeed their offspring into adulthood, such that a grown man would proudly take a suck from his old mother's breast. I wonder if lactose intolerance is common among the Inuit? (PS) I found the actual passage, confirming what was stored in my memory from 50 years ago! [17]. Edison (talk) 13:09, 28 May 2017 (UTC)

Hmmmm... I may have contributed to confusion here before. I went on recently about lactase being inducible in humans, being sure I'd read something to that effect, yet now as you say there are sources being cited to the contrary. Looking at it this time, I ran across a curious bit of data: [18] says that "The mean level of lactase activity among subjects with C/C-13910 genotype was 6.86 ± 0.35 U/g, with C/T-13910 genotype 37.8 ± 1.4 U/g, and with T/T-13910 genotype 57.6 ± 2.4 U/g protein" So at this key genetic locus, it is less than a ten-fold difference in level - and homozygotes and heterozygotes, differing by 2-fold, are taken to be essentially the same. That paper also concludes that lactase levels have to be less than 10 U/g for lactase intolerance to occur. Now that strikes me as a really small difference in enzyme activity, when we consider that some of us are afraid to put milk in coffee and others of us will kill an entire container of ice cream in no time! I also ran across an indication that intestinal flora contribute to lactase levels in rats [19] but haven't looked into this further. There's something I don't understand here... Wnt (talk) 00:10, 29 May 2017 (UTC)

Effect of bovine milk and human milk on human babies

Humans probably agree that human babies should be fed human milk. But in case the mother dies in childbirth, has HIV, or (A) just doesn't want to or can't breastfeed for some reason, (1) how good is unpasteurized, grass-fed, raw bovine milk as a replacement for human breast milk? (B) Human breast milk may be flavored with whatever food the mother eats. So, (2) does that mean if the mother eats crappy doughnuts and soda, the child will grow up to eat crappy doughnuts and soda? (C) And if the mother eats fruits and vegetables, then her veggie-flavored or fruit-flavored breast milk will cause the child to eat fruits and vegetables and reject crappy doughnuts and soda because they are too sweet to be palatable? (3) What about the breast milk of the biological mother compared with the breast milk of the adoptive mother or wet nurse? 50.4.236.254 (talk) 17:17, 28 May 2017 (UTC)

[I have lettered your premises and numbered your questions to facilitate others' who may wish to address them. Please be aware that (A) elides the fact that many mothers find themselves unable to breastfeed their infant(s), no matter how much they'd like to – glossing over this fact can cause offense and distress. {The poster formerly known as 87.91.230.195} 90.200.129.108 (talk) 20:07, 28 May 2017 (UTC)]

I made small adjustments by adding the word "can't". 50.4.236.254 (talk) 20:23, 28 May 2017 (UTC)

(1). Cow's milk compared to human breast milk contains too little iron, retinol, vitamin E, vitamin C, vitamin D, unsaturated fats or essential fatty acids for human babies. It also contains too much protein, sodium, potassium, phosphorus and chloride which may put a strain on an infant's immature kidneys. In addition, the proteins, fats and calcium in whole cow's milk are more difficult for an infant to digest and absorb than the ones in breast milk. United States Centers for Disease Control report 148 outbreaks, 2,384 illnesses (284 requiring hospitalizations) as well as 2 deaths due to unpasteurized dairy products between 1998 and 2011.

(2) There is no evidence of eating habits being inherited through breast milk.

(3) What about it? Wet nursing is not widely practiced now. A more acceptable substitute is screened, pasteurized, expressed milk (or especially colostrum) donated to milk banks, analogous to blood banks. Blooteuth (talk) 19:40, 29 May 2017 (UTC)

What does the word "refractory" in "refractory period" refer to?

I know what it means "refractory period" (both, absolute and relative) in the action potential graph, but I don't understand what the meaning of "refractory" in this context is. What is it refractory for? 93.126.88.30 (talk) 12:49, 28 May 2017 (UTC)

See refractory. Refractory is an adjective usually used around high-temperature resistant materials, indicating that they are unaffected by outside influences, such as heat. This is extended by analogy to physiology, to where there is a time period during the potential graph, during which this too is unaffected by further outside stimuli. Andy Dingley (talk) 13:07, 28 May 2017 (UTC)

Also see meaning 4 in the Wiktionary entry: wikt:refractory. Looie496 (talk) 14:05, 28 May 2017 (UTC)

Thank you. I found the answer here. "After repolarization there is a period during which a second action potential cannot be initiated, no matter how large a stimulus current is applied to the neuron. This is called the absolute refractory period, and it is followed by a relative refractory period, during which another action potential can be generated, but only by a greater stimulus current than that originally needed. This period is followed by the return of the neuronal properties to the threshold levels originally required for the initiation of action potentials." 93.126.88.30 (talk) 14:45, 28 May 2017 (UTC)

• This is really a language question. The word "refractory" means "very difficult to change." See refractory (disambiguation) for several non-metallurgical examples.-Arch dude (talk) 22:45, 28 May 2017 (UTC)

Re: whale death due to ship strike. Why not attach a beeping horn to the ships bow to provide warning to whales in imminent danger?

Blue whale gets hit by big ship and dies. Question: Would some kind of underwater horn that emits a warning sound towards the area of travel help whales avoid getting hit by the ship? My guess is, this would have been tried already and found to be unhelpful. But I'd like to know why it wouldn't work?

Thanks, --InverseSubstance (talk) 15:48, 28 May 2017 (UTC)

• I'm sure it has not been tried. Abductive (reasoning) 17:49, 28 May 2017 (UTC)

• Ships already make a large amount of noise, and whales not only have excellent hearing but also have natural sonar. The problem is that the whales make little or no attempt to avoid being hit by ships.[20]. The currently favored technology to reduce whale strikes is a combination of reduced ship speed,[21] routing shipping lanes away from where whales are most common,[22] and sonar and other alarms so that the ships can avoid the whales.[23] --Guy Macon (talk) 18:31, 28 May 2017 (UTC)

Whales evolved for tens of millions of years in an environment which did not include large, hard, fast counter-current-moving surface objects. They likely lack the cognitive ability to understand the ramifications of such objects, in the same way that many land mammals fail to cope with the characteristics of motor vehicles and end up as roadkill. Some of the latter may to some extent be evolving instincts helping to avoid traffic, but are evolutionarily aided by greater numbers and shorter generation lengths. {The poster formerly known as 87.81.230.195} 90.200.129.108 (talk) 20:17, 28 May 2017 (UTC)

The research papers are helpful. Thanks for that. I agree, the whales that avoid ships will be selected in, and the ones that don't will get selected out. There are deer whistles sold that one puts on the front of one's truck, and its supposed to warn deer to get out of the way. Maybe just another gimmick, eh? I have an idea! How about a giant airbag that inflates at the front of the ship to cushion the blow? Or maybe some powerful jets of water to give a warning? Just thinking out loud here... --InverseSubstance (talk) 20:34, 28 May 2017 (UTC)

Whalebags? Sagittarian Milky Way (talk) 20:42, 28 May 2017 (UTC)

Its very, very unlikely whales collide with ships because the oceans are really huge areas and shipping lines only use a tiny tiny fraction of the space. Also whales, especially as in this case a blue whale, usually avoid humans. Strangely in this case there are no reports about evidence like huge wounds or broken bones, far as i have read. So i wonder how this "ship collission"-Story made it to the news. Would not shock anyone if it turned out that someone boldly made it up just to fill some space and everyone else started copying it, would it? --Kharon (talk) 20:45, 28 May 2017 (UTC)

See here: "The entire left side of the whale was damaged from a boat strike, and the whale had 10 broken ribs and 10 fractured vertebrae from close to its tail to mid-body, according to Halaska. The whale was identified through photographs of its tail in a database of the Cascadia Research Collective. It was spotted 11 different years beginning in 1999, most often off Santa Barbara. The carcass will be left on the beach to decompose and be eaten by birds. A reef along Agate Beach would make towing the carcass back out to sea difficult." Count Iblis (talk) 00:30, 29 May 2017 (UTC)

[24] mentions "“It’s an unhappy coincidence,” Irvine says. Over a 2-week period in 2007, for example, at least three blue whales were killed by ships striking them near California’s Channel Islands. (Two other blue whale carcasses were spotted during the same 2 weeks, but the scientists weren’t able to study them.)" So actually it seems in the more reliable sources at least, when they say struck by a ship they mean we studied the carcass and decided it was most likely struck by a ship. This blog [25] by someone who seems to be a nature photographer is similar circumspect, it does have the photos if you want to check them yourself. Although interesting, the author does specifically note it was in an area with high shipping traffic. That was in Sri Lanka and [26] notes it's particularly an issue there (the claim is it's a leading cause of death). The first source suggests it is possible but less certain, it's also problem along the Californian coast. (Although the certainty may relate more to who's talking since one was a scientist studying whales whereas the other is an advocacy group.) I suspect some of the sources linked above by others before you posted also discuss the evidence blue whales are being struck by ships. Nil Einne (talk) 07:11, 29 May 2017 (UTC)

I think that a ship coming into port with a dead whale draped over its Bulbous bow is pretty good evidence that ships hit whales. -Guy Macon (talk) 14:47, 29 May 2017 (UTC)

There's several obvious flaws in your hypothesis. First, you can't say random chance is unlikely simply by saying the ocean is big, you need to determine what percentage of the ocean is covered by blue whales (in general) over a defined time period, e.g. ten years. If it's something like 0.00000001% then yes, random chance seems unlikely. But even at 0.1% it's starting to seem possible. Maybe you have some idea what this is based on evidence but that hasn't been presented here. And while I admit it seems likely it'll be small to me, you need to actually have some evidence (even OR) before you can just assume random chance isn't enough.

The bigger flaw though seems to be in assuming random chance. It's possible shipping lanes and the areas blue whales tend to swim in overlap for some reason e.g. favourable ocean currents or location near but not too near certain coasts. Maybe also favourable feeding/fishing grounds (yes I know blue whales are filter feeders but krill etc are eaten either directly or indirectly by some of the fish we eat); although shipping lanes was mentioned above I'm not sure if it's certain this was a cargo vessel (and of course if there is, it would be because the wounds etc have been carefully studies, as it seems they have been per Count Iblis). Maybe size would make it unlikely to be one but some Factory ship aren't exactly small. And these are a lot of assumptions, how well have you considered each one. To give a related example, if I see my neighbour on the bus in the morning on my way to work/uni/whatever regular activity and then see them on the way back as well, and then see them again tomorrow; thinking stalker is generally (but not always) silly regardless of there being many buses in Auckland. An even closer example, it's no surprise that whale watching ships can encounter whales somewhat regularly.

Also for the claim that "especially" blue whales avoid humans, I briefly looked but couldn't find any source discussing this. And what is meant by humans? Swimming humans? Large ships? There's a fair chance the whales aren't going to see these as the same thing, as others have indicated. (Actually the view including from people who actually study blue whales seems to be the opposite, blue whales don't avoid ships.)

Nil Einne (talk) 06:55, 29 May 2017 (UTC)

P.S. Especially in light of my other comment above, I should also point out if shipping lanes and the grounds some blue whales tend to inhabit overlap in at least one instance, it's interesting but ultimately irrelevant when it comes to considering the likelihood of collisions; why there's this overlap. Nil Einne (talk) 07:16, 29 May 2017 (UTC)

So you mean, That's a Whale of a Story! --InverseSubstance (talk) 20:49, 28 May 2017 (UTC)

I agree with Guy Macon: the ships are already really noisy. Underwater noise pollution is widely thought to contribute to deaths from cetacean stranding and so forth. The ship could start beeping when it detected a whale, but how would a whale understand that is in reference to it? Still, the wildcard here is whale language. If someone can figure out something to play that means "MOVE IT!", and broadcasts that when a whale is detected, maybe you have a winner. But without the experiment, that's just pure hot air on my part. Wnt (talk) 00:17, 29 May 2017 (UTC)

[27] Sagittarian Milky Way (talk) 19:21, 29 May 2017 (UTC)

The interested reader may find the following to be helpful; Amazon has a bunch of reviews of the book How to Avoid Huge Ships by those who have successfully avoided huge ships (and a few cautionary tales by those who failed to do so). The reviews are here:[28] --Guy Macon (talk) 15:00, 29 May 2017 (UTC)

May 29

What is shame from an evolutionary perspective?

It seems to me that a large part of shame has to do with the fear of social rejection. So, one requirement may be that the organism needs to be able to predict the future or remember the past. Another requirement may be that the organism needs to fear social rejection. Another requirement may be recognition of the self. Ay, there seems to be so many factors that I wonder if humans are the only creatures that can experience shame. 50.4.236.254 (talk) 02:24, 29 May 2017 (UTC)

Well, dogs show behaviors that look a whole lot like it. Looie496 (talk) 03:01, 29 May 2017 (UTC)

That makes sense. Dogs are social animals. I bet one of the requirements of shame is fear of social rejection. An animal can remember the past and be self-aware, but does not really depend on social approval and acceptance. 50.4.236.254 (talk) 03:32, 29 May 2017 (UTC)

Your bet is as good as ours. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:40, 29 May 2017 (UTC)

Social systems in the natural world involve a pecking order, so I would guess that it evolved to help to assess if your current position is at risk of being challenged. Count Iblis (talk) 05:54, 29 May 2017 (UTC)

Why speculate when there is Google?

Evolutionary Neurobiology of Shame

Why humans evolved to feel shame

On the biological and cultural evolution of shame

Evolving Concepts of Evolution: The Case of Shame and Guilt

A little bed-time reading. Alansplodge (talk) 17:55, 29 May 2017 (UTC)

Charles Darwin, in his book The Expression of the Emotions in Man and Animals, described the effects of shame. Roger Scruton, in "Modern Sex: Liberation and its Discontents" wrote "the real purpose of shaming is not to punish crimes but to create the kind of people who don't commit them". See the article Shame that suggests the emotion stems from comparison of the self's state of being with the ideal social context's standard. Blooteuth (talk) 19:09, 29 May 2017 (UTC)

@50.4.236.254: Your question is an interesting one, but one which had led to anthropomorphic and anthropocentric answers. Most ethologists today would accept that vertebrates and some invertebrates are conscious and therefore may experience emotions. However, this is just about where the agreement stops, mainly because of our human inabilities to ask questions of animals about these matters in a scientifically robust and biological meaningful way. DrChrissy ^(talk) 20:47, 29 May 2017 (UTC)

Domestic irradiator instead of a refrigerator?

Could an irradiator be an economically-viable alternative to a refrigerator? Would it require too much shielding? --78.148.98.254 (talk) 12:43, 29 May 2017 (UTC)

Irradiator is supposedly a device that heat things instead of cooling them? Ruslik_Zero 13:37, 29 May 2017 (UTC)

No - I imagine it is a machine using beta or gamma radiation as a means of food preservation - Food irradiation. I don't think I would want one in my kitchen. Wymspen (talk) 14:07, 29 May 2017 (UTC)

Well then, first step would be to know whether food irradiation is comparable to refrigeration as a way to preserve food. Our article on decomposition seems to say that abiotic decomposition is possible. Tigraan^{Click here to contact me} 16:02, 29 May 2017 (UTC)

Then this might be why this was not tried in the 50s. Sagittarian Milky Way (talk) 18:22, 29 May 2017 (UTC)

Irradiating food to preserve it between uses (which is what we use refrigerators for in kitchens) would require an impractical amount of shielding, yes. According to our article Food irradiation, 1000 Gray is considered a "low dose" for food irradiation, while a 5 Gray dose of whole-body radiation is considered lethal to humans within 14 days.

Apart from that, it's not just microbes responsible for food spoilage which are changed by food irradiation. While a one-shot dose of gamma radiation retards spoilage of food enough to permit, say, fresh produce to be economically shipped very long distances (between continents) for sale, repeated irradiations intense enough to keep food from spoiling between uses (in the way we, say, keep a jug of milk in the refrigerator to keep it from spoiling) would also change many foods enough to make them not taste good. Milk and eggs are good examples of complex foods we refrigerate and which would not survive many irradiations without being made unpalatable. loupgarous (talk) 18:26, 29 May 2017 (UTC)

Help with understanding a U-series dating method

I'm working on ice core, and have found a reference in Landais 2012 (p. 192) to a U-series dating method, cited to Aciego 2010. The latter is an appendix to the proceedings of a conference, without much discussion, but the reference in Landais, which just calls it "a promising study", makes it worth a one-sentence mention (and I've seen it cited elsewhere in introductions to journal articles on this topic). However, I don't understand the method and was hoping someone here could enlighten me -- I don't want to cite something I don't understand. It looks like Aciego et al are discussing U-series decay in dust that falls on the ice core, but what exactly are they measuring, and how does it determine age? Thanks for any help. Mike Christie (talk - contribs - library) 14:17, 29 May 2017 (UTC)

It looks like they are discussing uranium-uranium dating and uranium-thorium dating. Double sharp (talk) 14:47, 29 May 2017 (UTC)

You may find this paper useful. Mikenorton (talk) 15:35, 29 May 2017 (UTC)

That does help, but I'm not sure what Aciego is referring to by "recoil products from dust into ice". Is she saying that the alpha decay in dust grains of ²³⁸
U leads to the product, ²³⁴
Th (or a later alpha daughter product in the decay series) recoiling into the ice, and that analysing the ice itself for daughter products, eliminating the dust, can be used to determine the age via the given equation? I looked through Mike Walker's Quaternary Dating Methods to try to get a better understanding of how U-series dating works, and it looks like it depends on an event that causes a disequilibrium, which can be dated by determining the extent to which the decay has returned to secular equilibrium. I don't see what is going on here that would allow that method to work. Mike Christie (talk - contribs - library) 16:10, 29 May 2017 (UTC)

"Recoil products from dust into ice" seems to refer to an impact. Meteor (especially bolide in the geological sense of the term) impacts in parts of the Earth where uranium is relatively abundant in the mantle which release much dust into the atmosphere could create such a disequilibrium. See Uranium–lead zircon systematics in the Sudbury impact crater-fill: implications for target lithologies and crater evolution by Petrus et al for an example of studies of such phenomena which use uranium dating. loupgarous (talk) 19:48, 29 May 2017 (UTC)

I don't have access to the paper, but from the abstract I don't think that can be the explanation. Aciego is talking about dust in ice cores with miles of ice below them; there's no possibility of an impact being on anything but ice. Micro meteorites are found in ice cores, but that doesn't seem to be it either. Mike Christie (talk - contribs - library) 20:09, 29 May 2017 (UTC)

Which plant?

Which plant is this?

• 

--Pyrophyt (talk) 16:43, 29 May 2017 (UTC)

To my eye, it resembles some type of bean plant. Alansplodge (talk) 17:46, 29 May 2017 (UTC)

I agree that it's probably a legume, the location and date of the photo might help narrow down the possibilities. Roger (Dodger67) (talk) 18:41, 29 May 2017 (UTC)