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March 13

Objects in Earth's orbit

The Pluto article says that "Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit". Meanwhile, the Moon infobox gives its mass as 7.342×10²² kg, and its statement that this equals approximately 0.012300 of Earth's mass is compatible with the Earth infobox's claim of a mass of 5.97237×10²⁴ kg. Am I missing something, or is Earth's mass less than 100 times the remaining mass in its own orbit? Nyttend (talk) 01:47, 13 March 2017 (UTC)[reply]

I don't believe they are including the Moon as being "in the Earth's orbit" (that is, while it orbits Earth, it does not orbit the Sun in the exact same orbit as Earth), but they should state so clearly. StuRat (talk) 01:51, 13 March 2017 (UTC)[reply]

The article has a link to Clearing the neighbourhood which explains this in detail. Dbfirs 12:53, 13 March 2017 (UTC)[reply]

Why not replace sodium by potassium?

From table 4 on page 149 of this article we can deduce that the Yanomamo Indians have a salt intake of about 60 mg a day (the sodium intake is 23 mg) and a potassium intake of about 6 grams a day. Their salt intake is more than 100 times less than that of most of us, while their potassium intake is higher.

This combination of (by our measure) extremely low salt intake and a higher potassium intake is what all people were subject to until a few thousand years ago when we started to use salt as a preservative. Since that time we have gotten used to extremely high levels of salt, but at the price of doing severe damage to our cardiovascular system. Life expectancy was not long enough to notice the problems and when about a century ago life expectancy started to increase, the heart attacks and strokes due to high blood pressure were wrongly blamed on old age (the blood pressure of Yanomamo Indians does not increase with age, as the article shows).

So, why don't we just dump sodium and replace it with potassium? There are people who use certain types of diuretics who must avoid potassium, but they can just stick to low potassium foods. Count Iblis (talk) 02:21, 13 March 2017 (UTC)[reply]

NB — a big reason for recent increases in life expectancy is improved care on the other end of things, reducing deaths in childbed (thus increasing the percentage of adult women who lived to menopause) and slashing infant mortality (thus increasing the percentage of children who became adults). I suppose the life expectancy of individuals at age 50 has increased (penicillin and organ transplants have surely contributed to this), but increases in average lifespan for people who reach "old age" is probably less of a factor than increases in the percentage of people who reach "old age". Nyttend (talk) 02:56, 13 March 2017 (UTC)[reply]

Don't forget sewage treatment and water treatment, together making huge improvements in life expectancy. StuRat (talk) 02:58, 13 March 2017 (UTC)[reply]

Have you tasted potassium chloride ? It's OK in small doses, but nasty in concentration. It's also somewhat radioactive (not enough to be a real concern, but people get all upset about eating anything radioactive). And it's also used to execute people, adding to potential resistance from the uneducated. StuRat (talk) 02:58, 13 March 2017 (UTC)[reply]

Personally I think the main reason we get such an overdose of sodium is that it makes you thirsty, and beverages are a high-profit item in restaurants, leading them to pack in as much sodium as they can get away with. People then get accustomed to that level of sodium and replicate it in food they prepare themselves. Until you remove the profit motive, say with laws fining restaurants (enough to make the difference) for high sodium levels, there won't be much change. StuRat (talk) 03:04, 13 March 2017 (UTC)[reply]

Both Na⁺ and K⁺ are necessary electrolytes and dumping the former is a good way to get hyponatraemia. Na⁺ is the dominant one outside cells and K⁺ is dominant inside cells, and the balance between them is regulated by ion transporter proteins to allow the cell to generate an action potential. KCl injections work by disrupting this balance irreversibly, giving a lot of K⁺ outside cells. (Yes, their chemistry is different enough for this to work, even in this model example of group trends. Rb⁺ can partially replace K⁺ in some systems, which Cs⁺ cannot do at all, but even that is still inadequate as a total replacement.)

The taste of KCl varies with concentration. Generally cations and anions with higher atomic masses cause a more bitter taste; LiCl is very salty, while KCl, RbCl, and CsCl are bitter at all but the highest concentrations. Double sharp (talk) 04:32, 13 March 2017 (UTC)[reply]

Oh shit, you mean my eating calcium chews (I prefer cheese) and potassium- and magnesium-citrate has all been a big scam, and my sodium levels (from .5 to 1.5x normal) have all been a huge mind fuck (fuck)? I see my endocrinologer this coming 3/16. Please try not to die until I can report advice meant only for me personally. μηδείς (talk) 07:08, 13 March 2017 (UTC)[reply]

Hyperkalemia. --Jayron 32 12:09, 13 March 2017 (UTC)[reply]

The claim that KCl is bitter really surprises me. I've long used a "salt lite" that is half KCl because I prefer the taste to straight NaCl, and because I think a craving for "salt" is often a craving for potassium. (I think our ancestors evolved to seek crude mixtures from the earth, rather than purified sea salt) Honestly I still use it despite taking some lisinopril, which is a theoretical no-no but the potassium level on a blood test is still no where near the top of the normal range - I'm not recommending others do that, but when you want potassium the other sort of salt doesn't really satisfy. I keep both around. Between straight KCl and straight NaCl I'd prefer KCl by taste, but straight KCl has a noticeable coldness from dissolution and actually costs enough to notice, and doesn't taste quite as good as the mixture.

Though while I'm at it, I should mention that even Epsom salt isn't always bitter to me. Usually it is, though not tremendously so even though I typically just pour a little in my palm and wash it down with diet soda or water. Maybe one time in ten it has a pleasant sweet flavor - same stuff, same bag, same way - and I really have no idea why. (I eat a bit of now and then for energy and also to "antidote" the unpleasant effects of ham and other preserved meat on my heart - that's just a subjective sensation, which if left unopposed might lead to a skipped beat/"palpitation", but it seems worth a moment's opposition) Wnt (talk) 13:29, 13 March 2017 (UTC)[reply]

It could very well vary between observers, as a cursory Googling of various people's reports on the taste of KCl reveal. (It is already known to vary with concentration, after all.) Maybe pure KCl would taste more bitter, though; it is not clearly salty until about 0.1 M, according to the reference I gave. Double sharp (talk) 16:37, 13 March 2017 (UTC)[reply]

There is also the possibility that depending on bodily needs, the taste varies. This reminds me of over-salted meals prepared by first-term pregnant women, to the point of being nearly unpalatable to others present. PaleoNeonate (talk) 18:20, 13 March 2017 (UTC)[reply]

Hmm Life expectancy was not long enough to notice the problems is a lol statement that I love to hear when people complain about diet. --DHeyward (talk) 18:53, 13 March 2017 (UTC)[reply]

Shouldn't the title of this section be, "Why not replace sodium with Potassium?" All one can do is Kackle. μηδείς (talk) 20:34, 13 March 2017 (UTC)[reply]
- Indeed. The problem is that the OP's assumptions are wrong. The extreme demonization of NaCl salt was based on poor science, as with many (most?) other mainstream nutritional recommendations of the past few decades. If you aren't a Yanomamo, you may not have much to fear from salt, and slowly and quietly the mainstream is dumping and qualifying the defective science. Including such now rare populations in studies making recommendations for the vast modern majority descended from people using salt for millennia was one technique of this poor science. That being said, as suggested above, lite salt can be a good idea as it provides both major electrolytes in rough balance. Needs for electrolytes can vary between people and their living conditions. For instance, it is not uncommon that insufficient potassium intake can lead to the body breaking down muscles to obtain potassium, so sufficient potassium can cause instant muscle growth.John Z (talk) 00:52, 14 March 2017 (UTC)[reply]
  - I know that Dr. Alderman disagrees, but as pointed out here, he doesn't have good arguments. Count Iblis (talk) 02:06, 14 March 2017 (UTC)[reply]

There is sodium sensitive hypertension, which can be a serious problem for those who have it. StuRat (talk) 20:40, 15 March 2017 (UTC)[reply]

Is weight a net force?

A person stands on the scale to measure weight. The person has mass, and the mass of cells push on the scale because of the Earth's gravity. The scale has mass and pushes back. Also, what about the person's arms? Are they included in the weight even though they are attached onto the main body by joints? Would a swing set scale take into account of the person's whole body? 107.77.192.34 (talk) 13:53, 13 March 2017 (UTC)[reply]

Assuming the person is immobile in an inertial frame of reference (the Earth's surface is not, but it is close enough), Newton's first law applies to all parts of their body. The head is pushed down by gravity but up by the neck reaction which exactly compensates it (excluding negligible buoyancy effects). The neck is pushed down by gravity, down by the head (by exactly as much as it pushes the head up, per Newton's third), and up by the chest reaction that exactly compensates it etc.

You can decompose the body in your mind in as many parts as you want, the back of the feet are always pushed down by a force equal to the sum of the weights of all that is above, arms included, by a force equal to the total person's weight.

Notice also that the scale need not have mass the scale's mass is irrelevant - it merely needs to be able to provide a reaction force that equilibrates the person's weight (to avoid them falling through). The way the scales work is that the reaction force is measured and converted into a weight (by some mechanism). Tigraan^{Click here to contact me} 15:39, 13 March 2017 (UTC)[reply]

If you have a scale that has no mass, I'd like to see it. --Jayron 32 15:41, 13 March 2017 (UTC)[reply]

@Jayron32: How about a mass spectrometer? (oh, wait, I guess that has some in the name nyuk-nyuk. And ... oh, phooey, does a magnetic field necessarily have mass (in terms of there being some energy stored in it), or not? Wnt (talk) 23:20, 13 March 2017 (UTC)[reply]

How do you generate a magnetic field with no mass? The magnets have mass. The lenses have mass. The flight tube has mass. The electron gun has mass. --Jayron 32 01:25, 14 March 2017 (UTC)[reply]

Amended. Tigraan^{Click here to contact me} 15:54, 13 March 2017 (UTC)[reply]

In September 2010, we talked on the topic of how measurement really works in physics: "The scale can't actually measure a force - we're really measuring a compression of the spring inside the scale! ...we can simply relate spring force to mass; and we could have a standard spring-scale - so we could actually measure a mass in meters - even though mass is not measured meters!" All that was in response to a question about why physicists commonly describe mass using electron-volts, which sounds like a unit that ought to be better-suited to describing electricity! Nimur (talk) 18:58, 13 March 2017 (UTC) [reply]

Yes, it is determined by the mass of the person and the mass of the earth which is a "net" effect. I believe gravity is better described as a tensor field generated by objects with mass. --DHeyward (talk) 16:15, 13 March 2017 (UTC)[reply]

Clarifying the standard terminology: when we say "net force," we mean the sum of multiple forces.

When we measure weight for any object that isn't a point particle, we generally just use the total mass of the object and assume it can be well-modeled as a point particle at its center of mass. Weight is simply total mass multiplied by the acceleration due to gravity: typically, the little g constant). When we use that simplistic model, there's no "summing" of forces, so weight isn't a "net" force.

If you wanted to calculate the weight from a stack of point particles that are rigidly attached - and you don't care about the dynamic interactions of those objects, then you can just add up all the individual weights and compute their sum. That would be a net force due to multiple individual masses, and you might choose to ignore any of the complicated details about how they are connected. As a first step, you might want to consider the net force and the moment arm - the net displacement of the force from the center of mass - so you can determine if the grouping of mass exerts a net weight and a net torque. This complication is usually one of the first methods taught to aspiring physicists.

If the object has a complicated shape, and the weight is supported by more than one point of contact, we could use elaborate and difficult methods from engineering and physics, like rigid body mechanics and D/H parameterization to compute where each element of the force shows up, and how much weight is supported at each point of contact. If you wanted to design a control system for a human, or a bipedal robot, you'd probably have to know how much weight to put on each foot - how much force each muscle needs to exert - else there will be an unbalanced net force and the robot will either jump upward, fall downward, or topple to the side!

Nimur (talk) 18:15, 13 March 2017 (UTC)[reply]

The human probably doesn't have to know. Nature already has done the work. 107.77.193.67 (talk) 22:23, 13 March 2017 (UTC)[reply]

To maintain balance, those difficult control-equations have to be solved somewhere, even if you're just barely conscious of most of the things that are happening inside of your own nervous system! It's hard to blame you, because a significant amount of that work is done by your spinal cord without ever asking your brain for permission... when it comes to the difficult philosophical problems of sentience, everybody seems to forget about the lowly spinal cord. It's been doing your most difficult math homework for years, and your brain probably never even really knew it! Nimur (talk) 23:19, 13 March 2017 (UTC)[reply]

Isn't the cerebelum technically "doing the math" in this case though? PaleoNeonate (talk) 00:30, 14 March 2017 (UTC)[reply]

No. --Jayron 32 03:01, 14 March 2017 (UTC)[reply]

This somehow reminds me of Sumotori Dreams

(example link: [1]). PaleoNeonate (talk) 20:16, 13 March 2017 (UTC)[reply]

Ecological niche of Homo sapiens

1) What is the ecological niche of Homo sapiens?

2) Are they supposed to be fruit eaters and seed spreaders?

3) I have read that avocados were eaten by other animals before becoming human food. Humans bulldoze a lot of trees to make room for farming edibles. And many organisms are made more palatable by selective breeding. How do humans fit in nature?

4) What are they designed to do?

5) How can plants spread their seed when they are tightly controlled by humans? 107.77.193.67 (talk) 22:36, 13 March 2017 (UTC)[reply]

I added numbers to better answer your Qs. StuRat (talk) 22:40, 13 March 2017 (UTC)[reply]

5) "Control" is an interesting question. If an animal or plant we farm spreads because we farm it, are we controlling it, or is it using us ? StuRat (talk) 22:41, 13 March 2017 (UTC)[reply]

"How can plants spread their seed when they are tightly controlled by humans?". Plants have master the art of manupulating the dumb humans to spread their seeds for them by a very simple trick of making the plant's seed taste yummy for humans. 148.182.26.69 (talk) 22:56, 13 March 2017 (UTC)[reply]

While not answering everything, I will comment on some of the questions: 3) Not only for farming, but for demand for construction materials, land management and building. You are right that humans are able to keep farming crops, or animals, which may have otherwise become extinct in the wild. We may also have made some dependent on us over time, which would no longer survive in the wild. 4) That is a tricky question: there was no directed design that we know of (other than various origin myths), but there was adaptation and selection. Evolution of the brain may possibly answer some of the questions. PaleoNeonate (talk) 23:10, 13 March 2017 (UTC)[reply]

I also recommend Anatomically modern human#Modern human behavior. It may appear contentious, but what humans are doing is part of their nature, even if creating artificial environments and destroying natural ones. Serious crisis can cause some humans to sometimes go back to an ancestral pre-agricultural hunter-gatherer life if the natural resources for hiding and food are available. There also have been other circumstances of plants or animals dramaticaly changing their environment, although not necessarily at the same scale. PaleoNeonate (talk) 23:25, 13 March 2017 (UTC)[reply]

One answer to question 1 is Apex predator. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:30, 13 March 2017 (UTC)[reply]

Thanks for this very relevant link. PaleoNeonate (talk) 23:58, 13 March 2017 (UTC)[reply]

As kind of an aside I should mention with #4 that there is an old discredited idea, the so-called "Aquatic ape hypothesis", which accounts for relative human hairlessness as an adaptation to swimming. The notion that humans were some kind of dugong wannabe does indeed seem far-fetched (especially since polar bears are better at it, with no hair loss) but I think it is striking that in modern national parks humans are sometimes videotaped jumping into mud pits to free trapped animals. The broad feet of humans also seem like they might be suitable for a little extra advantage in thick mud. There are places like the Okavango delta that are all mud and standing water for one season, and wildfires to dodge and roast meat to be found from animals that weren't so clever in the other. Wnt (talk) 23:42, 13 March 2017 (UTC)[reply]

The answer to #4 is "nothing". There is no design to anything in nature, it just happens by chance. Humans are not designed for anything, from a scientific perspective. If you want to find purpose in your life, religion may be a valid way to do that for you, but evolution doesn't work by design. --Jayron 32 02:21, 14 March 2017 (UTC)[reply]

We know how evolution works, but it seems a bit silly to say a bombardier beetle isn't designed to hit anything ("it just happens to do it very well"). Hmmm, would you say that a research team that isolates an aptamer to bind a certain protein "designed" it or not? Wnt (talk) 22:12, 14 March 2017 (UTC)[reply]

The point is that words matter. The bombardier beetle was not designed by anything. It evolved. --Jayron 32 01:29, 15 March 2017 (UTC)[reply]

Yes, but everyone here knows that, so repeating such a nitpick is just annoying. StuRat (talk) 03:04, 15 March 2017 (UTC)[reply]

It depends on how you use "designed". Not actively designed by some super-intelligent being, necessarily, but "designed" by random natural forces. Sculpted, as it were. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:18, 15 March 2017 (UTC)[reply]

A m ore neutral but similar words is "shaped". If you say the beetle was "shaped by natural forces, pressures and interactions", people usually don't complain, and know what you mean. Many of my evolutionary biologist colleagues say things just like that. But when you say a beetle was "designed by natural forces...", that word is unfortunately loaded, and subject to (sometimes willful) misinterpretation, and while many people will know what you mean, others will wonder if you really understand evolution. So it is indeed best to avoid "design" when talking about evolution, unless you're pretty sure you know your audience, and they know you. SemanticMantis (talk) 19:15, 15 March 2017 (UTC)[reply]

We've got much the same problem with "natural selection". It could imply some conscious action by the forces of nature. In Jurassic Park, the Jeff Goldblum character said about dinosaurs, "nature selected these animals for extinction." Presumably knowing full well that it was just random natural forces, not some deliberate act. But it makes for a good metaphor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:58, 15 March 2017 (UTC)[reply]

It is not certain what the original poster really meant by "designed" at 4, so I think that it was still sensible to state the obvious. I also wrote a note on it earlier. PaleoNeonate (talk) 03:22, 15 March 2017 (UTC)[reply]

It's pretty clear he was referring to humans. The question also has an agenda, as with other recent IP's who've been asking about vegetables and the like. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:31, 15 March 2017 (UTC)[reply]

I think there is also an agenda in saying that nothing that evolved can be "designed" or have a "purpose". This is merely atheism masquerading as science. Scientifically we don't know whether evolution of organisms, like evolution of an aptamer selected by scientists in a lab, had an intended goal or purpose. There is a widespread religious belief in a "causality" that begins with a few random events in the distant past and proceeds to the present instant without any kind of planning. But that causality is at most an assumption, and I don't think it's even true. I think that the proper "causation" of events is more like a Sentience exists, it looks out and perceives a universe, and the universe is ... sculpted ... via the strong anthropic principle or more explicitly religious means to have a past consistent with that first initial cause. Some of that may be ordinary quantum mechanics, especially in the Copenhagen interpretation. And that process, whether unconsciously or not, is not merely the creation of logic and mathematics and ideas and natural selection as a tool, but also might require or even specify certain ecological features. And so the things we see may be random or they may be divine providence and there is no scientific principle I know of to tell us which with any great confidence. Wnt (talk) 13:54, 16 March 2017 (UTC)[reply]

No intelligent being required for them to form, and no known reliable evidence of any having been found, is indeed very different than everything being useless, or that there were no (at least natural) causes involved. If there's anything intelligent outside the world we know which could have been involved, there are many other new problems to consider, like the reason of suffering, for non-divine interference in the world, the culture-specific aspects and traditions, which are very interesting to study, even scientifically through archeology and other sciences. It would be right to say that science cannot disprove the existence of the divine, but it also happens that science can only deal with what is evident and palpable, what can be studied and worked with, and is often pushing the divine further away in the gaps of knowledge. Some people also live spirituality in a way that does not conflict at all with all that science discovered (an example being naturalistic pantheism). The need for spirituality, personal spiritual experiences and origins of religion can also be increasingly understood by science today, although there is still much more to be learned. Some proposed that we may live in a simulated universe... PaleoNeonate (talk) 02:17, 17 March 2017 (UTC)[reply]

5)See seed dispersal, e.g. zoochory, myrmechory, frugivory, wind dispersal,ballistic dispersal, and links therein. gene escape and hybridization are also relevant. SemanticMantis (talk) 19:19, 15 March 2017 (UTC)[reply]

Black dwarf atmosphere

The black dwarf article mentions that the atmosphere would be very thin, but with a citation needed tag. Considering the high mass of these objects, would it be likely to attract a lot of nearby gas but to also cause it to compact as a solid on the surface? If so, how could any gaseous carbon atmosphere persist? Perhaps that some particular gas could still persist as a thin atmophere? Any relevant source would also be appreciated. Thanks, PaleoNeonate (talk) 23:45, 13 March 2017 (UTC)[reply]

I can find no sources of any kind discussing the hypothetical atmosphere of a black dwarf, and I also doubt the unsourced statement that the atmosphere would be mostly carbon. Looking at White_dwarf#Atmosphere_and_spectra, the precursor to a black dwarf, though it has a mass of mostly carbon and oxygen, will have a primarily hydrogen/helium atmosphere, with heavier elements having sunk to the degenerate interior region due to gravitational separation. I can fathom no reason a hot object could retain this atmosphere for billions of years, but a cold one of the same mass and composition would be expected to lose it. Maybe a black dwarf is expected to lose its atmosphere to space in arbitrary time, but that means time scales matter, and the "carbon atmosphere" is only expected to exist after a certain point of time. Our article also refers to the atmosphere as "thin", but that needs clarification. A white dwarf's atmosphere is "thin" in that it forms a small portion of the star's mass, and is thinner than that of a yellow dwarf, and a black dwarf's atmosphere, being cold, would be thinner still. But what does that mean? So tldr, I can't find any sources on this, and the statement in our article, even if it's true, is too vague to convey any useful information. Someguy1221 (talk) 02:25, 14 March 2017 (UTC)[reply]

I'll leave the article as-is for now, but it's unfortunate that those claims cannot be reliably sourced or better explained at current time. Thank you very much. PaleoNeonate (talk) 03:45, 14 March 2017 (UTC)[reply]

Because a black dwarf is cold, the atmosphere would condense on the surface. If oxygen is in excess then an atmosphere of oxygen and nitrogen and inert gasses may exist like on earth. But if it is cryogenically cold, it may be more like the atmosphere of Pluto. It would not be thick due to the high gravitational field about 1,000,000 times Earth's, perhaps 10 cm thick. Graeme Bartlett (talk) 04:45, 14 March 2017 (UTC)[reply]

Hmm it makes sense, yes. Thanks, PaleoNeonate (talk) 03:17, 15 March 2017 (UTC)[reply]

From reading the article, the term "black dwarf" is not precise: it's just a white dwarf that has cooled. Two temperatures are mentioned: 5 K and .06 K, and the article states that the universe is nowhere near old enough for any white dwarf to have cooled down to 5 K yet, so there are no black dwarves. If we assume a definition of 5 K, I think that all gases except hydrogen will have condensed. But you can have fun thinking about warmer "almost black" dwarves and compute (guess) what the surface gravity will be, and therefore what gasses would be present. -Arch dude (talk) 04:17, 15 March 2017 (UTC)[reply]

Exactly. The article tentatively gets there, yet only barely (and so far without sufficient references, unfortunately). A fascinating topic, though. PaleoNeonate (talk) 05:30, 15 March 2017 (UTC)[reply]

This unreferenced section of the article has been cleaned out by Someguy1221 for now, so unless we find a good reference and rewrite it, this issue is now solved. Thanks to all. PaleoNeonate (talk) 09:16, 15 March 2017 (UTC)[reply]

The atmosphere is going to be "very thin" (width) in the sense that the scale height is ridiculously small. It is also going to be "very thin" in the sense that at a high multiple of the scale height few atoms will be present, and that at lower multiples any hydrogen present won't be atmosphere but metal or something, eventually electron degenerate matter as you go deep enough. But it should be very thick in the sense that no matter how much hydrogen you dump on that star the atmosphere shouldn't get any thicker -- the hydrogen should keep condensing to something else as fast as you put it on. Wnt (talk) 14:03, 16 March 2017 (UTC)[reply]

March 14

Interstellar travel and intergalactic travel

Does the entire planet Earth has enough resources for interstellar travel? Is intergalactic travel possible? --IEditEncyclopedia (talk) 00:14, 14 March 2017 (UTC)[reply]

Voyager 1 and Voyager 2 are engaged in interstellar travel. If you're talking about practical travel, i.e. by humans in something well short of an average lifespan, we don't have the technology to do that, so we can't say what resources it would require. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:33, 14 March 2017 (UTC)[reply]

Yeah it is about manned travel. --IEditEncyclopedia (talk) 00:35, 14 March 2017 (UTC)[reply]

And as the articles imply, interstellar would necessarily precede intergalactic, as the nearest neighboring galaxy is way much farther away than the width of our own galaxy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:43, 14 March 2017 (UTC)[reply]

I agree with the above; even human interplanetary travel further than the moon, or for any long stay, is currently very challenging. There are some complex scenarios being studied to send humans on Mars, and for colonization of Mars. PaleoNeonate (talk) 00:48, 14 March 2017 (UTC)[reply]

To quote Douglas Adams, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:55, 14 March 2017 (UTC)[reply]

IMHO, the lowest form of power source that might be viable for manned interstellar travel is a nuclear fission reactor, which could then be used to run a linear accelerator and send a matter stream out the back at near the speed of light, hopefully in quantities that can produce a constant 1 g acceleration. We have a huge quantity of fuel for such a reactor, especially if we were to decommission nuclear weapons for their atomic cores. This technology is available now. The next step up would be fusion reactors, which don't require specialized fuel, or better yet, matter-antimatter reactors (no article ?), which require extremely specialized fuel (the antimatter part), which we would need to produce on Earth, or hopefully someplace safer, like the Moon. Those technologies don't yet exist, at least in practical forms. As for the mass to shoot out the back, we could grab an asteroid for that. I like the idea of placing it in front of the ship, for the journey, to use it as a shield, while it is mined down to use as the propulsion mass. StuRat (talk) 01:09, 14 March 2017 (UTC)[reply]

Or just digitize your brain, send a simple radio message explaining how to decode and run the data in the next message and then go ahead with sending the data. We repeat this over and over again (so, we don't wait for a reply). If 2.5 million years later, ET in the Andromeda galaxy were to receive StuRat's digitized brain contents this way, they could run him and then StuRat, who would be long dead here on Earth, would wake up in the same state he was in when he was digitized. From StuRat point of view, this means that he has to be prepared for the fact that he could find himself in some ET's computer immediately after being digitized, even though he would yet have to be sent and the message would be received a long time after that. Count Iblis (talk) 02:03, 14 March 2017 (UTC)[reply]

Would that really be you or just something just like you? And no, he would not have to be prepared to wake up immediately after being digitized, the StuRat that wakes up will be a brand new sentience that never existed before. To show that this is true, what if some guy reanimated his brain into his clone on Earth while he was still young? Then he could immediately screw the clone. He will not be the bottom, a being that never existed before would be the bottom. Sagittarian Milky Way (talk) 15:32, 14 March 2017 (UTC)[reply]

That brand new sentience is nevertheless identical to StuRat because, by construction, he will react to every stimulus in exactly the same way as the "real" StuRat the moment he was digitized. It's basically what is pointed out here at the end of this story about identical copies of us in an infinite multiverse. Count Iblis (talk) 00:23, 15 March 2017 (UTC)[reply]

James Patrick Kelly's Think Like a Dinosaur and the subsequent Think Like a Dinosaur (The Outer Limits) episode were excellent fictional treatments of this topic, and, in particular, whether destroying the original is murder. StuRat (talk) 01:07, 15 March 2017 (UTC)[reply]

(Edit conflict) To elaborate on Bugs' earlier point, the nearby Andromeda galaxy is 2 1/2 million light years away. So even if we could quickly accelerate to near light-speed, it would take 2 1/2 million years to get there. So manned intergalactic travel is not possible unless we are willing to commit many generations of space travelers to the effort. Loraof (talk) 02:08, 14 March 2017 (UTC)[reply]
Understatement of the year. Anatomically modern human have only existed for about 45,000-50,000 years. So we'd have to survive as a species some 50 times longer than we already have, and do so on a spaceship. That is, if we had started traveling towards Andromeda at the beginning of when anatomically modern humans evolved, we'd only be 1/50th of the way there today. Good luck on making it that far... --Jayron 32 02:18, 14 March 2017 (UTC)[reply]

You've neglected time dilation. If close enough to the speed of light, very little time would pass aboard the ship. Of course, there may very well be nothing recognizable as human to report your results to, after making a round-trip. StuRat (talk) 03:53, 14 March 2017 (UTC)[reply]

Time would appear "normal" to those on-board the travelling ship. It would be the distance to the other galaxy that would appear contracted. (I agree that this depends on your speed of view.) Dbfirs 07:12, 14 March 2017 (UTC)[reply]

That's only unless people are able to achieve an alcubierre drive,which I'm surprised no one has even mentioned.Uncle dan is home (talk) 02:33, 14 March 2017 (UTC)[reply]

Be careful. Linking to that article will summon BenRG, and he will have to explain to you why people get way too excited about it. Actually, go and look for it in the refdesk archives, he's made some good comments on it. Someguy1221 (talk) 02:36, 14 March 2017 (UTC)[reply]

An infinite improbability drive or Bistromathic drive would both do the trick. --Jayron 32 02:42, 14 March 2017 (UTC)[reply]

The real problem with traveling fast enough to get to Andromeda in a few years is that your spacecraft will be exposed to extremely high energetic radiation and dust particles. At a gamma factor of a million, the kinetic energy of a dust particle will be a million times its rest mass; being hit by a microgram dust grain will lead to about $10^{14}$ Joules of energy being deposited, which is similar to the yield of the atomic bomb dropped on Hiroshima. Count Iblis (talk) 00:41, 15 March 2017 (UTC)[reply]

This is why I propose travelling with an asteroid in front of the ship, to use as a shield. StuRat (talk) 01:00, 15 March 2017 (UTC)[reply]

The classic hard science fiction story about this is Tau Zero. If you can continue to accelerate at 1 G, your velocity will eventually (within two shipboard years?) get so close to C that time dilation becomes extreme ("Tau" approaches zero) and you can reach anywhere in the universe. This is not possible with today's technology because the amount of fuel would be "very large." The author avoids this by using a Bussard ramjet, which gathers hydrogen from the interstellar/intergalactic medium while the ship is in flight. -Arch dude (talk) 03:31, 15 March 2017 (UTC)[reply]

I think, given the way commercial spaceflight companies are booming, in the next 200 years, humans will established permanent lunar base for mineral extraction and space experiments. In the next 500 years, asteroid mining might well become commercially viable. So human will colonize gradually, starting from moon, then mars, then expanding to outer solar system. I might well take 5000 years. After that, they will start colonizing extra solar planets. So, say, lets assume, 1 million years from now, humans will colonize the entire Milky Way. So the starting point of journey towards another galaxy will not be Earth, but some other star system in our galaxy. Should be reduce the distance between the starting point of journey and the other galaxy? --IEditEncyclopedia (talk) 01:36, 16 March 2017 (UTC)[reply]

Anything's possible, but we're still using conventional rocketry for transportation. And no matter where you start within the Milky Way, you're way much closer to anything in the Milky Way than you are to the nearest neighboring galaxy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:41, 16 March 2017 (UTC)[reply]

pinpointing science fiction movie with "very noisy rain dropping down"?

I'm trying to pinpoint/remember a science fiction movie staged at a planet with devastating rain and two guys taking shelter in some mushroom shaped structure so they wouldn't turn crazy from the noise of the rain which (I think) was amplified due to the planets high gravity. Lots and lots of years have past since I saw that (part of?) the movie. I guess it's from the 80's or early 90's. Quite grateful if someone can resolve that brain fart of mine.--TMCk (talk) 01:32, 14 March 2017 (UTC)[reply]

You may get an answer here but I would suggest you move this to Wikipedia:Reference desk/Entertainment TracyMcClark. MarnetteD|Talk 01:35, 14 March 2017 (UTC)[reply]

(ec) I'm asking it here on the science desk since I might have some science related followup questions.--TMCk (talk) 01:36, 14 March 2017 (UTC)[reply]

The film is The Illustrated Man, and the story on which this part of the film was based is The Long Rain by Ray Bradbury. DuncanHill (talk) 01:39, 14 March 2017 (UTC)[reply]

Thanks. That sure must be what I watched some late night years ago. Now the next question is if there is some science of such "hard dropping noisy" rain causing any mental harm in real life.--TMCk (talk) 02:27, 14 March 2017 (UTC)[reply]

Perhaps I was over confident - it was also adapted as an episode of The Ray Bradbury Theater in 1992. DuncanHill (talk) 01:45, 14 March 2017 (UTC)[reply]

Also sounds vaguely like an original Outer Limits episode, where being caught in the rain caused one to become evil, grow comically large eyes, and gain the powers to read minds and vaporize people with a touch. Not their best work. StuRat (talk) 02:10, 14 March 2017 (UTC)[reply]

There's noise pollution, but that fortunately seems nowhere near that. PaleoNeonate (talk) 02:52, 14 March 2017 (UTC)[reply]

The Mutant is the episode in question, but it was chemicals in the rain, not the noise, which were the supposed problem. StuRat (talk) 03:46, 14 March 2017 (UTC)[reply]

I have to wonder if the author had a metal roof on his house, which seem like they could drive one insane from the noise, during rain. StuRat (talk) 03:48, 14 March 2017 (UTC) [reply]

Much of Futurama is a reference to other work. The episode Brannigan, Begin Again features high velocity rain on a high gravity planet, but I don't see anything indicating that the high gravity rain has anything to do with previous work. I hoped there would be some geek reference system that would say, "The high gravity rain is a reference to..." 209.149.113.5 (talk) 17:55, 14 March 2017 (UTC)[reply]

This is where ear plugs come in. But then you wouldn't have a story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:20, 14 March 2017 (UTC)[reply]

I'm fairly sure a survey of literature with a 19th-century colonial setting would find instances of Europeans supposedly being sent mad by unending torrential monsoon rain on a corrugated tin roof: that and the continual drumming of the locals is something of a comedy cliché. I can't however bring any specific instances to mind. {The poster formerly known as 87.81.230.195} 90.202.209.145 (talk) 18:42, 14 March 2017 (UTC)[reply]

Honey, I Shrunk the Kids? --Hans Haase (有问题吗) 11:32, 16 March 2017 (UTC)[reply]

March 15

Fire engines on rails?

Are there currently, or were there ever, fire engines which ran on rails (either rail-only, or road-to-rail)? Also, while I'm sure there aren't any such engines now, but were there ever steam locomotives which were outfitted to fight fires using their onboard water supply (similar to Belle in Thomas & Friends)? If there were (or still are) any such fire engines, what is/was their firefighting niche? 2601:646:8E01:7E0B:45D4:4D76:B31B:9250 (talk) 10:37, 15 March 2017 (UTC)[reply]

I know of no such engines, as dedicated fire-fighting vehicles - either locomotives or trucks.

However railway wagons are a convenient way to move things, and it's easy to put a fire engine or a pump and tank combination, onto a flat wagon and then move that around the railway. These were widely used during the bombing of WWII, for the dockyards that already had good rail access and were bombing targets. The UK produced a few standard designs of trailer-pulled fire pump and as well as being towed on the road, these were used from rail wagons. More recently, preserved steam railways in the '70s and '80s (after the withdrawal of steam in the UK) often had a problem with lineside fires in inaccessible places and so these also made use of them, as the site could be more easily accessible by rail than by road. Andy Dingley (talk) 10:56, 15 March 2017 (UTC)[reply]

A quick google came up with the Burlington Northern Santa Fe (BNSF) Fire Train. http://www.firefighternation.com/articles/2013/11/bnsf-railway-s-unique-firefighting-tank-car.html amongst other webpages and there is a video on youtube. --TrogWoolley (talk) 12:09, 15 March 2017 (UTC)[reply]

The answer is yes. I've placed an illustration of one at right. A Google search for "firefighting trains" will find articles about this or a similar one, and plenty of others today: [2][3][4][5]

Their niche is, as you might expect, fighting fires that are close to the railway tracks and not close to roads.

The above examples are modern, but at least one railway, the Southern Pacific, also had firefighting trains in steam days. They did not use the steam locomotive's water supply (which the train needed in order to move), but carried separate water tanks.[6]

--76.71.6.254 (talk) 12:11, 15 March 2017 (UTC)[reply]

The Swiss firefighting trains are presumably useful because of the large number of (rail-only) tunnels there. If there's an accident inside a tunnel and a train catches fire, there's no way to reach it except with another train. --79.237.64.244 (talk) 04:41, 16 March 2017 (UTC)[reply]

Microwave oven effectiveness decline with use

I know that a microwave oven becomes less effective with use but I don't know whether this means it consumes less electrical power or because it becomes less efficient and consumes the same power. Which is it? — Preceding unsigned comment added by 192.41.131.255 (talk) 11:02, 15 March 2017 (UTC)[reply]

The microwave emission from the Cavity magnetron, a kind of Vacuum tube decreases as the cathode coating degrades. As a result, If a new microwave oven boils a cup of water in one minute, after five or 10 years it may take 90 seconds. The oven remains usable but consumes more energy to do the same job slower. See Microwave oven. Blooteuth (talk) 14:25, 15 March 2017 (UTC)[reply]

Does insufficient protein intake seemes as causing Erectile dysfunction in a healthy person?

If it is, than what is the mechanism? I didn't find information on this in Erectile dysfunction. 77.179.179.98 (talk) 15:57, 15 March 2017 (UTC)[reply]

Erectile dysfunction is usually a matter of blood flow, or hormone levels. Neither of these is directly related to protein insufficiency per se, although if you get to the point of muscle wasting there might be other complicating factors, such as the fact that lean muscle mass tends to increase testosterone levels. So, basically, "no, but..." and if you have a specific concern, see a medical professional. μηδείς (talk) 18:42, 15 March 2017 (UTC)[reply]

"Low levels of protein are linked to high levels of sex-binding globulin, which locks up testosterone so the body can't use it, according to a study by Dr. Christopher Langcope of the University of Massachusetts Medical School.": [7]. Now low testosterone reduces libido, but that's not quite the same as erectile dysfunction, which is when a male with the desire is still unable to get an erection. The two conditions might be confused, however, especially if the male in question hides the fact that he has no interest in sex with his partner. StuRat (talk) 20:31, 15 March 2017 (UTC)[reply]

Hiding the fact that he has no interest in sex with his partner is matrimonial deceit not erectile dysfunction. The point about erectile dysfuncition is that erection is desired but unobtainable. Richard Avery (talk) 09:28, 16 March 2017 (UTC)[reply]

Solubility of sugar in salt solutions

What data are available on the solubility of sucrose in sodium chloride and other salts aqueous solutions compared to solutions without salts? Is there any salt that could increase the solubility of sugar compared to solubility in pure water?--5.15.12.130 (talk) 19:15, 15 March 2017 (UTC)[reply]

I have not found any research paper on the subject of solubility of sucrose in saline solution, per se. But I have found this article, which suggests that NaCl and C12H22O11 both dissolve in water fully. For solubilities of NaCl and C12H22O11, you may check out this picture. Apparently, they dissolve independently of each other. One does not act as a catalyst or inhibitor for the other. 50.4.236.254 (talk) 00:52, 16 March 2017 (UTC)[reply]

Reference: Wang, Xiao-Lin; Zhang, Chenghong; Ouyang, Pingkai (2002). "The Possibility of Separating Saccharides from a NaCl Solution by Using Nanofiltration in Diafiltration Mode". Journal of Membrane Science. 204 (1–2): 271–81. {{cite journal}}: |access-date= requires |url= (help)

See also Salting out. But some otherwise insoluble carbohydrates, like chitin can be dissolved in N,N-dimethylacetamide and lithium chloride. Graeme Bartlett (talk) 01:06, 16 March 2017 (UTC)[reply]

I've tried to test the solubility of sugar in a saturated salt solution. The noticed result has been indeed salting out with the solubility reduced to about half compared to pure water.--5.15.12.130 (talk) 17:40, 16 March 2017 (UTC)[reply]

Apparently there is cooperative effect of sucrose and sodium chloride dissolving in water, where presence of either one increases solubility of the other. See:

Prinsen–Geerligs, H. C. (1908). "Molasses: Its Definition and Formation". The International Sugar Journal. 10: 227–235, 284–292.

DMacks (talk) 01:47, 16 March 2017 (UTC)[reply]

It seems that salting in for sugar at some concentrations range is given only by urea.--5.15.12.130 (talk) 17:57, 16 March 2017 (UTC)[reply]

I notice that the mentioned journal The International Sugar Journal is not present on Wikipedia!--5.15.12.130 (talk) 18:05, 16 March 2017 (UTC)[reply]

Can sugar(s) present both salting out and in by the same salt?(another related question in this context) Thanks!--5.15.12.130 (talk) 18:15, 16 March 2017 (UTC)[reply]

What quantitative data regarding the intensity of salting in and out are there as a function of mixing ratio(s) of sugar-water-salt? (I see that these articles salting in and salting out are rather lacking quantitative data! Also I see that there is only fucose (data page).)--5.15.12.130 (talk) 18:38, 16 March 2017 (UTC)[reply]

How do double sided cylinder locks work?

(I sort of asked a related question to this several years ago - but I remain puzzled.)

Our front door has a cylinder lock into which the key can be inserted from either side, in both cases with the spine uppermost (so it isn't pivoting levers) and the key is NOT symmetrical along its length. Additionally if a key is inserted on the inside and partly turned, an outside key can also be fully inserted and it freely rotates, achieving nothing. On realizing that you can't lock the door because the key is on the inside, you remove that key and the outside key still does nothing. So you remove the outside key and reinsert it and the door can be locked.

Without doubt, the mechanism is more involved than

. So, how does it work please? -- SGBailey (talk) 19:56, 15 March 2017 (UTC)[reply]

Not having examined your front door, I can only speculate from experience. Most likely the set up is similar to this [8], with two separate but identically keyed lock cylinders and a mechanism to disengage one of there is other is turned. If you live in Europe the setup is most likely like this [9], which is the same thing in a different package. WegianWarrior (talk) 20:19, 15 March 2017 (UTC)[reply]

Your second image looks plausible - they obviously have to have good tolerancing on the split positions in the pegs, but that isn't hard these days. Thanks. -- SGBailey (talk) 23:57, 15 March 2017 (UTC)[reply]

There are two lock cylinders, quite independent. The bolt is worked from the centre, between the two of them, and is operated by a loose dog clutch. Turning either cylinder can activate the bolt. If it's a removable one-piece Euro cylinder (or its variants), this dog clutch is between the cylinders and rotates a single "tooth" around it, which drives the bolt.

A drawback to some of these, if poorly engineered, is that the bolt can be moved back or forth without needing to defeat the key cylinder, by using some sort of wire pick around the cylinder and working the bolt directly. Andy Dingley (talk) 00:25, 16 March 2017 (UTC)[reply]

Sounds like a not-very-dead dead bolt. DMacks (talk) 01:30, 16 March 2017 (UTC)[reply]

It can be either - a dead bolt, or a sprung sash bolt. Andy Dingley (talk) 11:37, 16 March 2017 (UTC)[reply]

→[10] --Hans Haase (有问题吗) 19:54, 16 March 2017 (UTC)[reply]

March 16

What's the world's rainiest and driest settlement with >19,999 people?

By most average days per year with rain and highest average number of years between rains. Sagittarian Milky Way (talk) 15:31, 16 March 2017 (UTC)[reply]

I don't know. I know that Arica, Chile is often regarded as the driest place on earth, but the standard way of measuring this is in annual precipitation. Our article discusses the rather uncommon climate there. See here [11] for a list of other top driest places. As for most rainy days, Guiness [12] says that is Mount_Waialeale. By annual precip, see Mawsynram, and the links therein, leading eventually to the town of López_de_Micay. SemanticMantis (talk) 19:27, 16 March 2017 (UTC)[reply]

March 17

The expanding universe

Wikipedia's article states that the universe is expanding at large scales but that galaxies are not because they are gravitationally bound. This implies there will be an astronomical number of roughly spherical boundaries in space, surrounding every galaxy, on one side of which space is expanding and on the other side of which space is not expanding. The presence of such discontinuous boundaries in space seems extremely unlikely. It seems far more likely there is a smooth function relating the expansion of space to the force of gravity. In which case who is to say that galaxies may not expand with the universe albeit with a much reduced rate. A small residual rate of expansion for galaxies would be extremely hard to observe but could have major consequences. Comments please 165.120.168.239 (talk) 00:50, 17 March 2017 (UTC)[reply]

G_{\mu \nu }+\Lambda g_{\mu \nu }=8\pi T_{\mu \nu }

? Introduction to general relativity is our article on the topic. Nimur (talk) 01:22, 17 March 2017 (UTC)[reply]

Would there really be a hard "boundary" or more of a gradual transition, as with the gravitational influence of different objects? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:03, 17 March 2017 (UTC)[reply]

One qualitative way to look at this: the universe is expanding uniformly, but gravity locally retards the effects of this expansion. But you really need to do the math. Your vision of "roughly spherical" is a simplification that would be valid only if galaxies were point masses of equal mass. A more accurate(?!) image is a universe with a continuous density variation. For some critical local density, gravity is stronger than expansion. At lower density, expansion wins. -Arch dude (talk) 02:19, 17 March 2017 (UTC)[reply]

How accurate is this table?

Could someone verify the accuracy of this time dilation table,since I'm no expert in physics? It's the second table. I'm not sure whether the person who wrote the article has any expertise.Uncle dan is home (talk) 02:44, 17 March 2017 (UTC)[reply]

Which article? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 17 March 2017 (UTC)[reply]

This one: [13] — Preceding unsigned comment added by Uncle dan is home (talk • contribs) 03:11, 17 March 2017 (UTC)[reply]

Have you spot-checked any of the calculations in the table vs. the formula? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:19, 17 March 2017 (UTC)[reply]

How do doctors categorize something as a "disease"?

I know that there is variation within a species. Some individuals have a beneficial mutation; other individuals have a harmful mutation. But the ability of all modifications to pass down to future generations is dependent on the environment. Hereditary hemochromatosis is regarded as a "disease", even though those individuals may be just very efficient at absorbing iron from food. Meat is full of iron, so these individuals would fare poorly in a meat-rich (iron-rich) environment. Huntington's disease is caused by a lethal gene that manifests in adulthood. It is only a "disease" when that person lives long enough to manifest it. If the person reproduces at 15 and dies in childbirth at 20, then the gene may be passed onto the offspring, and the manifestation of the gene may not be shown. People on the autism spectrum seem to live happy, fertile lives. And people with Down's syndrome have children. So, my main question is, what are the characteristics of a disease? How is a disease different from a variation that just happens to be maladaptive in a given condition? 50.4.236.254 (talk) 03:13, 17 March 2017 (UTC)[reply]

See Disease. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:16, 17 March 2017 (UTC)[reply]

Mechanism of action?

See this article here What is the possible mechanism for their strengthened immune systems? (If this is true?) 64.170.21.194 (talk) 03:23, 17 March 2017 (UTC)[reply]