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October 31

Can neutrinos collide with each other?

If so, how often would this happen? Would collision be more common among extremely low energy neutrinos?Rich (talk) 07:28, 31 October 2019 (UTC)[reply]

Apparently so. --Jayron 32 11:37, 31 October 2019 (UTC)[reply]

thanksRich (talk) 12:34, 3 November 2019 (UTC)[reply]

It’s less common at low energies, like neutrino-electron interactions. The interaction cross section increases a lot when the center-of-mass energy gets closer to the mass of the weak gauge bosons (W boson, Z boson). Icek~enwiki (talk) 08:33, 2 November 2019 (UTC)[reply]

But at higher energies the neutrinos are moving faster, doesnt thet mean less time to exchange the boson? I thought if the neutrinos were moving quite slowly(which might be unusual but seems possible)then there would be more time to interact.Rich (talk) 12:34, 3 November 2019 (UTC)[reply]

More important than this time of being close to each other is the energy available - or in a slighty different view, the frequency matching. Like all particles, the neutrinos have a wave nature, with the wavelength inversely propertional to the momentum and the frequency inversely proportional to the total energy. In this sense, the W and Z boson have a large minimal frequency due to their large rest mass-energy.

If we don't have the required energy to create @real@ W or Z bosons, the W or Z field will fall off exponentially with distance instead of propagating like a wave.

For details on how to calculate such things, see quantum field theory and Feynman diagram.

Icek~enwiki (talk) 17:50, 4 November 2019 (UTC)[reply]

Destructive interference and conservation of energy

Two waves that move in opposite directions meet and for a single moment cancel each other. When dealing with, say, water or sound waves, at the moment when two waves interfere and cancel each other, energy is preserved in the medium momentum. The water are briefly flat, but the water molecules are in motion. Where to the "missing" energy when electromagnetic waves meet goes? -IlanMa

The energy is to be found where the waves reinforce each other. The fields add together, and the energy/power is proportional to the square of the field. So you might think that with two waves you get four times the power, but that only compensates for the destructive interference. Graeme Bartlett (talk) 21:10, 31 October 2019 (UTC)[reply]

If one of the waves has positive amplitude and the other negative, there will be no reinforcing. Also, conservation of energy has to be satisfied for each point in time, and not be an average over an interval. The answer must be something else. אילן שמעוני (talk) 03:54, 1 November 2019 (UTC)[reply]

If you could launch two waves from the same point with opposite "amplitude" then they would cancel each other out. What would happen is that energy would go from one source which had current and voltage in-phase, to the other source that had the current opposite to the voltage. With alternating waves they will often be averaged over time to measure the power. But if you want instantaneous in time then you will get a sinusoidal power transferred. The energy will move from one point to another at the speed of light, and where there is reinforcement, the energy will travel there, and away from the cancellation area. Graeme Bartlett (talk) 10:58, 1 November 2019 (UTC)[reply]

Not necessarily. Take the most "primitive" way to create electromagnetic wave - simply to shift the position of a statically-charged object. Take 2 such objects, and shift them perpendicular to the line between them, but in opposite directions. You'll get an two electromagnetic waves propagating, with opposing amplitudes. The wave form will be whatever you desire (determined by changing the velocity during the shift). Anyway, I still think that satisfying energy conservation over time is not enough. It must be conserved for any given time, down to Plank time. I may be missing something obvious, but so far I see no answer to this conundrum. It's not that I believe that Mr. Anonymous found a breech in physics, but I still can't see any direction towards an answer. אילן שמעוני (talk) 11:19, 1 November 2019 (UTC)[reply]

Moving a charge to excite an electromagnetic wave requires adding work to the otherwise-closed system. In this scenario, energy is conserved only when you correctly account for the added work. Nimur (talk) 14:23, 1 November 2019 (UTC)[reply]

In the case of two moving charges moving in opposite directions close to each other, energy has to be put in when they approach each other, and it is extracted when they separate. So they will bounce backwards and forwards like a spring, and no energy will be radiated, it will just come in and out of the system via the "antenna". Graeme Bartlett (talk) 21:28, 1 November 2019 (UTC)[reply]

When two waves traveling in opposite directions meet and interfere as you describe, the result is called a standing wave. With water or sound waves, for a single moment the displacements cancel out, and the velocities add. A little later, the displacements add, and the velocities cancel out. With electromagnetic waves, something very similar happens when you include both halves of the word electro-magnetic. If at a given moment you make the electric fields cancel, the magnetic fields will add, and vice versa. --Amble (talk) 05:33, 1 November 2019 (UTC)[reply]

You seem to assume that the oscillation in the magnetic field in 180 degrees phase shift from the electric field. I see no reason to assume that. The 1st diagram in Electromagnetic radiation, for example, illustrates perfect same-phase on both fields. In such case your suggestion fails. Anonymous already stated that the situation with in-medium waves is known to him (I didn't know up to this point, btw) and drawing mysterious hints. Last but not least, Standing wave is a totally different phenomenon - I asked what happens in a single pulse, which fits the original question, and will not produce standing wave. A knowledgeable answer is required. אילן שמעוני (talk) 07:10, 1 November 2019 (UTC)[reply]

Why not review Poynting's theorem in your favorite book on electrodynamics? In Griffiths' Electrodynamics, this is section 8.1.2 (Work) and 9.2.3, (Energy and Momentum in Electromagnetic Waves). To put it bluntly, the math is quite difficult, but it is well understood by knowledgeable physicists - it just takes some effort to study it. Nimur (talk) 13:54, 1 November 2019 (UTC)[reply]

In the standing wave, an equivalent wave is travelling in the opposite direction as the forward wave, and the electric field is flipped compared to the forward travelling wave if there is a short circuit at the end. If there is an open circuit then the magnetic filed will flip 180° at the termination. You can use a right hand rule to work out the direction of travel given a magnetic and electric field. If one is switched 180°, the the direction of travel will also switch 180°. ~~In this case the energy is quadrupled where the waves reinforce, and zeroed where they cancel.~~ The average is double because you have two waves, one forward and one reverse. Graeme Bartlett (talk) 10:37, 1 November 2019 (UTC)[reply]

Take note that electricity flow through a conductor, unlike photons in vacuum, has a medium. It's just the same as the water/sound/spring - the medium movement (the electrons in the conductor) take care for energy preservation, so trying to sort this puzzle through electrical signals thought experiment is unlikely to provide an answer.::::EDIT: I never thought such simple trivial question would give me such pain. אילן שמעוני (talk) 11:26, 1 November 2019 (UTC)[reply]

...Have you ever worked a problem in mathematical physics before? Simple questions often have alarmingly complicated implications. Part of formal education in physics is the repeated re-working of difficult standard-form equations in trigonometry, analytic geometry, and calculus, so that we can rapidly reduce to a previously-solved and easily-recognized standard form. After a few years and a couple thousand iterations solving for sinusoid coefficients, you too can follow along with the abbreviated shorthand notation that summarily executes the same equation-solving methods, and you start to focus only on the nontrivial parts. Nobody knowledgeable says that physics is easy. Nimur (talk) 14:15, 1 November 2019 (UTC)[reply]

Two similar electromagnetic pulses of the same amplitude travel in opposite directions towards each other. If their E-fields are aligned, then their H-fields must be opposite (because the direction of propagation is E×H). The energy density at any point in space is (εE²⋅+μH²)/2. For each pulse, half its energy is in the E-field and half in the H-field (because |E|/|H|=Z₀=√(μ/ε)). When the pulses meet, the E-fields add and the H-fields cancel. The total energy in the E-field doubles (because the square of the sum is twice the sum of the squares). The total energy in the H-field is reduced to zero. The total energy in the E- and H-fields together is therefore conserved. catslash (talk) 14:04, 1 November 2019 (UTC)[reply]

For a pulse travelling along a conducting wire, the energy is not in the movement of the electrons (or not much is). The energy is still mainly in the electric and magnetic fields. The mobility of the electrons (imperfectly) prevents the fields from entering the conductor (because the electrons move to cancel the field). Consequently, the fields carrying the energy slide along the outside of the wire like a bead. catslash (talk) 14:28, 1 November 2019 (UTC)[reply]

Quite right - and in the even more generalized statement, it is only meaningful to calculate the energy of an electromagnetic wave when you correctly manage the bookkeeping for both fields, plus the energy in any coupled charges and currents. In this fashion, because of the coupled fields, an electromagnetic wave is entirely dissimilar to a simple acoustic wave or a transverse vibration on a string: an electromagnetic wave is a coupled system: its field amplitudes are described by a different wave function and different propagation equation; its energy is defined by a combination of two, coupled, energized fields, related by our great and powerful friends: the Maxwell's equations for electromagnetic dynamics. Nimur (talk) 14:33, 1 November 2019 (UTC)[reply]

user:Catslash, I want to see if I got this right, and I'll walk through each step seperately. I assume E-field is electrical, so the H-field is magnetic (usualy denoted as B)? אילן שמעוני (talk) 16:52, 1 November 2019 (UTC)[reply]

H and B are two different ways of quantifying a magnetic field. H is the magnetic field strength and quantifies the field by the current needed to sustain it (including displacement current). B is the magnetic flux density and quantifies the field by the force it produces on a moving charge. The two are related by B=μ₀H. Physicists tend to prefer B, calling it the magnetic field and regarding it as somehow more fundamental than H. My own field of endeavour is not mathematical physics but microwave and r.f. engineering; in this discipline B is almost never used. catslash (talk) 16:07, 2 November 2019 (UTC)[reply]

User:אילן שמעוני: I was responding to the original question, which posits two waves of equal amplitudes traveling in opposite directions. This is precisely a standing wave. The important thing is that you have to include the energy in both electric and magnetic fields, and it's not possible for both of them to cancel at the same time. This is similar to mechanical waves where you have to include the energy in both displacement and motion. No, I don't assume that the electric and magnetic fields are out of phase; it simply isn't relevant to the original question. --Amble (talk) 22:07, 1 November 2019 (UTC)[reply]

OK, still, if the phase of the magnetic and electric fields are identical, we still have a problem - they will both cancel out at the same moment. It seems User:Catslash answers that the fields can not be at the same phase, and must be shifted 180 degrees from each other. If that's true, it will solve the problem completely. It also means that the illustration at the beginning of Electromagnetic radiation is totally misleading. One thing at a time. אילן שמעוני (talk) 10:58, 2 November 2019 (UTC)[reply]

That 180° phase shift is happening when the waves are travelling in opposite directions. But perhaps they are starting from nearby points, as in an antenna array or diffraction grating. Then as you get far away the angle difference gets smaller and smaller and closer to zero. The waves then do cancel to close to zero in some directions and reinforce in others. Graeme Bartlett (talk) 11:54, 2 November 2019 (UTC)[reply]

User:אילן שמעוני No, it’s not just a question of phase, because the electric and magnetic fields are everywhere perpendicular to each other and perpendicular to the direction of travel (assuming we’re talking about free space). The two waves traveling in opposite directions have Poynting vectors pointing in opposite directions as well. This guarantees that, if the electric fields of the two waves cancel, the magnetic fields reinforce, and vice versa. If you try to make the two waves cancel in both the electric and magnetic field at the same time, they will necessarily have the same Poynting vector, and oops! now they’re traveling in the same direction instead of opposite directions, as specified in the original question. —Amble (talk) 14:38, 2 November 2019 (UTC)[reply]

Getting to the bottom line

The answers diverged into several branches. To get this right: Is the situation depicted in this illustration not possible and can never happen? If so I would love to dig a little further. If it is possible, I'm back to square 1. A definitive Yes/No will be much appreciated.

I'm tagging those brave men and women that tried to clarify this mystery: User:Graeme Bartlett, User:Nimur, User:Catslash, User:Amble

אילן שמעוני (talk) 09:24, 6 November 2019 (UTC)[reply]

The illustration is possible, but it does not depict two waves travelling in opposite directions. The Poynting vector (ExH) is in the same direction for both waves. They are thus both travelling in the same direction. It also confoundedly defines z in two different directions just to add to the confusion. SpinningSpark 12:53, 6 November 2019 (UTC)[reply]

There are arrows denoting the waves propagation directions, that is head to head. This is my own illustration. and I ask - Is this possible? If not, why? Reading about Poynting vector, it just states that it's "represents the directional energy flux (the energy transfer per unit area per unit time) of an electromagnetic field", with various ways to define it, a cross product of the electric and the magnetic fields. It deals with the energy flux (charge density can be very low, as in vacuum in space, so I figure that's negligible). It's been decades since I used such math stuff in college, and I was never too brilliant with it, still I can't see how it helps. It forces non-zero values for energy flux, but does not show how this comes to be true in the case I illustrated. אילן שמעוני (talk) 14:52, 6 November 2019 (UTC)[reply]

'stressing out: I see no constriction that forces that opposing waves will both not have the same phase to E and B fields. In such case ALL factors of energy flux are zero at the moment of destructive interference. אילן שמעוני (talk) 15:08, 6 November 2019 (UTC)[reply]

One can not completely describe an electromagnetic wave by illustrating it in graphical form as you have done. It is not even clear what you have drawn - and truthfully I'm not interested in finding out: as an analogy, if I were to write a bunch of random squiggles and lines, and I told somebody it was Russian and I needed help to translate it... I mean, I might send the non-Russian-speakers in circles while they looked up resources and tried to help me correct my errors...

But a fluent Russian speaker would not be fooled by my nonsense. It is immediately obvious that my squiggles are not Russian; they are not even Cyrillic characters with a couple of errors; they are just squiggles. Reasonable people would not be able to meaningfully answer "yes/no" questions about the literary implications of these squiggles.

This is what your diagram looks like to a physicist. Creative, perhaps - but ... I'm not going to help you or anybody else decipher it, because it is essentially a grapical-form of nonsense.

One must properly write the wave equation, and then one can completely and correctly solve for the propagation (e.g. time evolution) and for the change in energy at each point in space at each moment in time; and then one can talk meaningfully about how wave interference moves - or does not move - the energy around.

Trying to solve a question of physics without using the tools of physics is like trying to build a house without wood, bricks, hammers, or nails. You're not even using the tools wrongly: you're just not using them - so how do you expect to fruitfully proceed?

Grab a good book on electromagnetic waves from your local library or school. If you like, we can recommend several great books at various levels of difficulty. If, as you say, you have not used these tools in decades and "can't see how it helps," then I think our discussion devolves in this manner: please accept on good-faith this argument from authority: very smart people work these questions of physics on a daily basis, and they all say that the study of electromagnetic waves requires a lot of math. If you want to work through problems about electromagnetic waves, you must learn this math, or you must let other people solve these problems without you. In a specific situation, we might be able to provide a simple summary of "how we fixed it," but there is no way to simplify the general answers. The reference desk isn't a suitable place for any of us to work your equations for you - what we can do is point you to encyclopedic reference material.

Nimur (talk) 15:46, 6 November 2019 (UTC)[reply]

The notion of electromagnetic wave as derived from charged objects displacements predated wave equations, and is still valid. If you wave a charged object you create an electromagnetic wave, this is straightforward and is beyond doubt. What isn't beyond doubt, not for me, is what is the form and phase of the accompanied B field wave.

I really appreciate the offort - no cynicism - and patience you put into this, but I don't think you are totally spot-on with the role of mathematics in physics, not at least as I've been taught some 30 years ago in collage. Mathematical considerations are of course essential, but they can not be used without a set of underlying theory and concepts. The complete physics package has to include both underlying concepts AND mathematical procedures. So I am looking for the concepts here, and expect the math to go hand in hand - so to speak - not to lead.

I recall a famous quote (by Feynman?) shut up and do the math, but this saying had a specific context - namely quantum mechanics - and here I think we're still in the realm of Maxwell's theory (from which, alas, I remember close to nothing, except that it can be summed to 4 differential equations, and that I had 82 in this course, to my relief).

However, if someone (I suspect that's you) was taught Maxwell's theory by means of close to pure math, it is more than like that it will be close to impossible to him/her to formulate explanations otherwise. To use your analogy, it is to describe something in a language that you are fluent with to someone who is fluent with another language.

אילן שמעוני (talk) 16:46, 6 November 2019 (UTC)[reply]

It's not entirely clear what you mean by the diagram. However, I can speculate that you mean to ask "can an EM wave in free space travel to the right while its Poynting vector points to the left?". The answer to that question is No. --Amble (talk) 19:32, 6 November 2019 (UTC)[reply]

At first glance the diagram seems to be asking "Can I draw the same EM wave twice, once in right-handed coordinates and once in left-handed coordinates?". The answer to that question is Yes (although I don't think this is the question you intended to ask). --Amble (talk) 19:40, 6 November 2019 (UTC)[reply]

If I may speculate a little more, you may be assuming that you can choose some configuration of E and B, and then also freely choose ∂E/∂t and ∂B/∂t, so that you can set up "this wave traveling to the left" and "this wave traveling to the right". But Maxwell's equations don't let you do that. Once you have chosen the configuration of E and B, you can plug them in and calculate the unique solutions for ∂E/∂t and ∂B/∂t that tell you the dynamics (in this case, how the wave will propagate). (We're talking about a wave in free space, where ρ and J are zero). --Amble (talk) 22:04, 6 November 2019 (UTC)[reply]

Salmon foam

After I cook salmon sous-vide, there's a white foam on top that solidifies when it cools. What is this, and is it healthy to eat ? SinisterLefty (talk) 22:27, 31 October 2019 (UTC)[reply]

Probably fat and gelatin from the fish. Fats will liquefy as they reach their melting points and then solidify as they cool; think of melting butter. I sometimes notice some foamy white stuff when I make salmon, usually by grilling. --47.146.63.87 (talk) 23:28, 31 October 2019 (UTC)[reply]

I was thinking either fats or cholesterol, but then the question remains, are those good fats and cholesterol I should eat, or bad fats and cholesterol to avoid ? Gelatin would be fine to eat, I assume. SinisterLefty (talk) 02:13, 1 November 2019 (UTC)[reply]

That depends nearly entirely on your BMI status. If your weight is of no concern, there is close to no reason not to consume fat and cholesterol. There is only weak correlation between cholesterol consumption and blood cholesterol. Over 90% of the blood cholesterol is produced in your liver. Overweight, on the other hand, has been shown again and again to be a serious health risk and to lower life expectancy. — Preceding unsigned comment added by אילן שמעוני (talk • contribs) 03:51, 1 November 2019 (UTC)[reply]

I get the impression that everyone should consume as much good fat and good cholesterol as possible, while minimizing bad fat and bad cholesterol. Not an easy task, though, as they are often mixed together. SinisterLefty (talk) 06:09, 1 November 2019 (UTC)[reply]

There are many publications here's one that there is little to no effect of cholesterol consumption on cholesterol in blood. Sure, high LDL levels in the blood are lethal, but you will have them with or without cholesterol consumption as your liver is the culprit. Unless you suffer from another condition that makes cholesterol consumption bad for you, you can munch on cholesterol to your liking.

The most prevalent condition that makes fat consumption a very bad idea is obesity. Across all food sources, fat contains most calories, double than pure sugar. אילן שמעוני (talk) 07:19, 1 November 2019 (UTC)[reply]

But that ignores the satiety effect of eating fats. If eating the sugar leads to a sugar crash and then you eat more to compensate, for several cycles, you could well end up eating more calories than in fat, if it keeps you feeling full. SinisterLefty (talk) 08:27, 1 November 2019 (UTC)[reply]

True, true. אילן שמעוני (talk) 08:59, 1 November 2019 (UTC)[reply]

The fat from salmon is pinkish-orange in colour (WP:OR); the white stuff is probably protein leaching out of the meat. Cooks refer to this stuff as "scum" (second def, I guess). On one of his shows, chef Alton Brown compares it to spume due to its similar content and consistency. Matt Deres (talk) 00:12, 3 November 2019 (UTC)[reply]

November 1

Amateur solar telescopes

The common designs seem to focus on blocking most of the sunlight, so it isn't blindingly bright. But this seems to be a wasteful approach, to me. Most telescopes try to maximize light gathering power, but solar telescopes try to reduce it. Why not project the image onto a large enough area that it isn't blindingly bright, so as to not lose detail by filtering out light ? Wouldn't that make features like sunspots more visible ? Watching eclipses (partial or full) would be another application. SinisterLefty (talk) 06:30, 1 November 2019 (UTC)[reply]

Your suggestion only fits small-aperture telescopes, here's why: with a big telescope (my guess is that 200mm is too large) the heat that will be focused through the eyepiece will be enough to crack it, or even blow it to pieces.

I know for certain that with a 70mm aperture you suggestion is safe. I tried that. Directing the telescope to the sun was very frustrating, btw.

EDIT: I noticed your "so as to not lose detail". You do not lose detail if you make the holes in the opaque telescope cover at its opposite edges. The detail is determined by the effective aperture, and the effective aperture stays the same this way.אילן שמעוני (talk) 07:32, 1 November 2019 (UTC)[reply]

Not following your last comment. If only one photon comes from a particular feature on the Sun, that would have been collected by the telescope, and that photon is filtered out, then you lost that detail.

As for heat, here I would think filtering out the light would make things worse, if that filtered out light is turned into heat in the telescope. Rather than absorbing it, reflecting the excess light or refracting it, to a place designed to take the heat, would help. But if all the light passes through the lenses, very little should be turned into heat there. Keeping dust off the end of the eyepiece would be critical, though, as that would absorb light and heat up. SinisterLefty (talk) 15:42, 1 November 2019 (UTC)[reply]

The problem is the CONCENTRATION of heat in the eyepiece. The main mirror focus the heat from its entire area into a much smaller focal plain. Much like burning a paper with a magnifying glass - but with a larger scale. The cover you must use sits at the telescope front end, and so just gets warmed normally as if you laid the cover out in the sun. Only a tiny fraction of the radiation is allowed into the telescope itself.

As for your concern for image quality: Telescope angular resolution is proportional to its aperture. since the light from both holes focus to the same focal plain, it builds a single image - so you get the full width resolution.

I do not know of a specialized screening eyepiece except digital eyepieces, which are either low quality or VERY expensive (sometimes both). Projecting straight from the eyepiece is manageable enough, you just have to position the screen perpendicular to the common L shaped focuser. I am quite sure I'll find illustrations for this arrangement. אילן שמעוני (talk) 17:08, 1 November 2019 (UTC)[reply]

FOLLOW_UP: Is there equipment designed to project the telescope image onto a large screen ? I imagine you might need a long distance, without a special lens, to get the image to be large enough to not be blinding. Would the image also go out of focus over this distance ? SinisterLefty (talk) 16:03, 1 November 2019 (UTC)[reply]

The Helioscope has been around for quite a while. Jeremiah Horrocks used one for his observation of the 1639 transit of Venus and it was invented long before that. See also https://www.skyandtelescope.com/observing/observing-the-sun/Richerman (talk) 17:21, 1 November 2019 (UTC)[reply]

Take a peek at this short guide. Also, be aware that without very expansive H-Alpha filter you can not see solar eruptions. You can see granules as in the photo there, and sunspots - but, alas, there are currently no sunspots. אילן שמעוני (talk) 18:35, 1 November 2019 (UTC)[reply]

Further to the article externally linked by אילן שמעוני above, the method shown in the section titled 'Projection with a Telescope or Binoculars ' is easy to perform and known to all amateur astronomers. (If using binoculars, only one 'ocular' is used, with the other covered by its lens caps.)

The screen can be placed at any convenient distance from the eyepiece (a lightweight screen-holder may be constructed to attach to the scope), and the image is easily focussed using the eyepiece focusser: however, the further away the screen is, the larger but fainter the image will be.

I myself used as a teenaged amateur to project from the eyepiece of an stopped-down 8" Newtonian telescope, within my school's small observatory, an image of a foot diameter on to a hand-held screen (with a pre-drawn circle for the sun's outline), which was entirely bright enough for making observations and sketches, but in astronomy society meetings I have seen an image of perhaps 8 feet diameter projected onto a white wall in a darkened room.

Professional Solar telescope observatories were purpose built to eliminate extraneous light and maximise contrast and size when observing a raw image, though often they instead added a spectrograph to the optical train to observe and record the Solar spectrum. Nowadays, of course, professionals (and many amateurs) mostly use digital cameras and computer screens rather than projections and naked eyes. {The poster formerly known as 87.81.230.195} 2.122.179.237 (talk) 06:20, 2 November 2019 (UTC)[reply]

I have a couple cheap telescopes that I wouldn't mind damaging, in order to give this a test. I assume that the image of the Sun should always be pointed down, and nothing reflective should be down there, to avoid risk of eye damage. I also have some loose large lenses, such as one from an overhead projector, that may work. And I have a nice set of binoculars, but don't want to risk damaging those. Is a flat screen OK, or should it be parabolic ? SinisterLefty (talk) 06:34, 2 November 2019 (UTC)[reply]

I have never seen anything but a flat screen used. In theory this might introduce a small distortion, in that the regions further from the centre of the flat-screen image will be slightly stretched, but for a home set-up this would be imperceptible. Additionally, the centre and edge of the image will be at best focus at slightly different distances, so close examination of one or the other might require very slight refocussing of the eyepiece. This would only matter if the 'screen' was actually a photographic plate being used to capture a single complete image. {The poster formerly known as 87.81.230.195} 2.122.179.237 (talk) 19:54, 2 November 2019 (UTC)[reply]

It should be obvious that observing a common star that is only about 93 million miles away is dramatically different from all other aspects of amateur astronomy. Eclipse observation presents a great opportunity to observe the sun in "non boring" circumstances. I have had the privilege of observing an annular eclipse in Redding, California in 2012 and a total eclipse in Madras, Oregon in 2017. At such events, you can meet amateur astronomers with a high degree of expertise in the full range of observing techniques. In Oregon, we had two inexpensive solar telescopes, two DSLR cameras with telephoto lenses, and a four inch telescope. Rigging up the cameras and bigger telescope with homemade but well researched solar filters was fun. Roaming around seeing the incredible variety of amateur telescopes and discussing telescope techniques with amateur experts was memorable. Cullen³²⁸ Let's discuss it 07:13, 2 November 2019 (UTC)[reply]

User:SinisterLefty, what are the apertures (diameters) of the telescopes you have in mind? I asked several friends that are in my amature astronomy club. On used 114mm f10 without a problem. Another tried 6" (approx. 150mm) and said the focuser got very hot very quickly so he aborted. I heard that some people had eyepieces literally explode, which is dangerous beyond damage to the telescope.

All in all you got it right. You can use plain white paper, or a wall as a screen.

important: You may be into disappointment. with 70mm no granules where seen, only sunspots - but currently there are no sunspots! To view granules I think you'll need 6" or above. Many people will be disappointed by granules, though - they're not that spectacular, and the changes are too slow to perceive. You can forget about these spectacular solar prominences - that requires H-Alpha filter. אילן שמעוני (talk) 12:58, 2 November 2019 (UTC)[reply]

Although there are currently no spots, there was a cluster of faculae the last time I checked: however these are a rather subtle phenomenon for a first-time solar viewer. {The poster formerly known as 87.81.230.195} 2.122.179.237 (talk) 19:54, 2 November 2019 (UTC)[reply]

My cheap telescopes are 2.5 inches and 3 inches in diameter, which I assume will be unable to show any detail other than sunspots. On the plus side, heating shouldn't be much of an issue. Is there a good site with sunspot forecasts ? Or can they only say what the current conditions are ? SinisterLefty (talk) 21:33, 2 November 2019 (UTC)[reply]

Forecasts aren't very good. If you wanted to see say the most spotted sun of the next solar cycle you'd have to check hundreds of times to be sure you don't miss it. Some scientists are predicting that sunspots might be going downhill in the first third of the 21st century and will stay infrequent for up to several lifetimes so the next sunspot cycle might be the most impressive you'll ever see. The cycles are slowing down so late 2020s might be a good bet. Now is a deep solar minimum, infrequent, few and small sunspots. In 2019 75% of the time the sun had no sunspots of any size. Sagittarian Milky Way (talk) 02:14, 3 November 2019 (UTC)[reply]

OK, late 2020s it is, assuming both I and the Sun are still around then. SinisterLefty (talk) 16:12, 6 November 2019 (UTC)[reply]

Distance between and position of objects in the galaxy

So, one thing I have noticed when reading about other stars and exoplanets is that we already have estimated distance from Earth for most of them in terms of parsecs and lightyears. Does this imply that their positions relative to Earth never significantly change as they orbit around the Milky Way galactic center and that the speeds in which they move is not really different from the speed of the solar system? Is it actually possible to draw a map of our galaxy with fixed position for every significant object inside it and use it as a long-term reference? 70.95.44.93 (talk) 09:17, 1 November 2019 (UTC)[reply]

No. While many stars do roughly move along around the galactic center, the variation is huge. For example μ Columba AE Auriga are moving very fast at a path unrelated to orbiting the center. I seem to recall an application or maybe a site that shows how the night sky will change in the future. Whithin 10,000 years the change is significant.

EDIT: Didn't find app, but found a relevant vid. אילן שמעוני (talk) 10:27, 1 November 2019 (UTC)[reply]

And it may seem like the objects in the sky are moving slowly, but keeping in mind that the distances are huge, maybe thousands, millions, or billions of light years, it takes a long time to move a significant portion of those huge distances, even at extremely high speeds. SinisterLefty (talk) 15:48, 1 November 2019 (UTC)[reply]

The answer is complicated because many Star systems are "binary"(2), "trinary"(3) or even hole "clusters" of suns (1000), sometimes assumed with a dominating Black hole or alike "monster"-object in their center, so the movement of individual suns in that system may change very dynamically over short time.

Also realize that this field of research has actually just started and demands very, very expensive tools and instruments. The James Webb Space Telescope will be launched next in March 2021 and NASA has projected the costs at roughly over 10 Billion $ then. Just for this single Telescope! --Kharon (talk) 22:22, 1 November 2019 (UTC)[reply]

Meanwhile, Gaia has done a fine job of cartographing a significant part of the Milky Way, including measuring the velocities of millions of stars. The James Webb is completely unsuited for that sort of work. --Wrongfilter (talk) 22:46, 1 November 2019 (UTC)[reply]

אילן שמעוני in 5,000 years the night sky will change more due to precession of the earth axis, then due to stars proper motion. The whole cycle for precession takes 11,000 years. AboutFace 22 (talk) 01:45, 2 November 2019 (UTC)[reply]

It wouldn't. The poles will be elsewhere, but you would just have to take the current maps and adjust the coordinations grid. That's true for most visible naked-eye stars, there are some exceptions, but not because of percession. אילן שמעוני (talk) 12:46, 2 November 2019 (UTC)[reply]

26000Sagittarian Milky Way (talk) 03:25, 2 November 2019 (UTC)[reply]

The Sun moves at 220 km/s around the center of the Milky Way, around 1/1400 the speed of light. That means it takes 1400 years to move a light year so if another star somehow stood still in the galaxy and the Sun moved directly towards it, it would take 1400 years to change the distance by a light year. And the relative speed between stars is usually much lower. If a star is measured to be n light years away then it doesn't matter much in what year it was reported, considering how briefly we have been able to make such measurements. But it does matter over many millenia as seen in File:Near-stars-past-future-en.svg. It takes the Sun 225 to 250 million years (a galactic year) to orbit around the Milky Way center. PrimeHunter (talk) 03:52, 2 November 2019 (UTC)[reply]

That's interesting. So the Sun has only circled the galactic center some 17-19 times. SinisterLefty (talk) 05:33, 2 November 2019 (UTC)[reply]

And it takes 171 to 190 years for the Sun to circle 1/360/60/60 times which is about 1 pixel through a telescope limited by the inability of humans to take 0.001 second retina snapshots to freeze twinkling blur. Sagittarian Milky Way (talk) 19:02, 2 November 2019 (UTC)[reply]

Standing wave, not

See [1]. The article describes an actual standing wave, where two waves of the same period coming from opposite directions create a resultant wave that doesn't move horizontally, but changes greatly in magnitude, and features many equal peaks and troughs (see this video at 1:20: [2]). However, the pic at the top of the article is another phenomenon, where a wave doesn't change in either position or magnitude, and there is no interference between waves. This type generally has a large central peak/trough, with progressively smaller peaks and troughs following it, and seems to result from the geometry of the river bed just upstream. What is the real name for this phenomenon, and the physics behind it ? SinisterLefty (talk) 17:03, 1 November 2019 (UTC)[reply]

A Stationary hydraulic jump. Mikenorton (talk) 17:31, 1 November 2019 (UTC)[reply]

Thanks. SinisterLefty (talk) 18:32, 1 November 2019 (UTC)[reply]

Resolved

November 2

Electric current

Does it flow, or does it just exist,? — Preceding unsigned comment added by 213.205.242.221 (talk) 00:35, 2 November 2019 (UTC)[reply]

In DC current, the electrons do actually flow in a steady direction, like a river, although far slower than the speed of light. In AC current, they flow forward and backward, so that there is no net movement, similar to the tides coming in, then going out, in a repeating cycle. SinisterLefty (talk) 01:50, 2 November 2019 (UTC)[reply]

Kind of? The question sounds simple, but its more complex than posited, because there are different things being asked by the question "Does electricity flow?" There's a YouTube channel called "The Science Asylum", which is fantastic for rather well-explained, intuitive videos on very complex issues like electricity. His videos on electrodynamics are rather good, and directly address the OPs question. Does Electricity REALLY Flow? and Energy doesn't FLOW the way you THINK! are two electrodynamics videos that have some rather non-intuitive facts about electricity. You'll also probably want to watch some of his earlier videos like What is electric charge. --Jayron 32 16:25, 4 November 2019 (UTC)[reply]

Flux in cores

Does the flux in a transformer core increase as the power transfer increases? — Preceding unsigned comment added by 213.205.242.221 (talk) 00:37, 2 November 2019 (UTC)[reply]

Yes, the current will increase, causing more flux. Graeme Bartlett (talk) 12:57, 2 November 2019 (UTC)[reply]

Up to a point. Transformers can saturate their cores, if there's too great a flux.

As an efficient transformer (i.e. for production cost relative to power capacity) will run their flux close to, but not exceeding, this saturation point, it's not a good assumption to expect that transformer power can be increased beyond their design value – even ignoring any heating or insulation problems with the windings.

Deliberate saturation is used in a few devices as a limitation mechanism, such as transductors or even the current-limited isolating transformers for shaver sockets in UK bathrooms. Andy Dingley (talk) 16:09, 2 November 2019 (UTC)[reply]

What's the velocity never exceed of an SR-71 and X-15 at sea level?

If they're unclassified by now that is. Sagittarian Milky Way (talk) 02:52, 2 November 2019 (UTC)[reply]

At sea level they'd start taking on water. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:02, 2 November 2019 (UTC)[reply]

There's lakes below sea level. Sagittarian Milky Way (talk) 03:33, 2 November 2019 (UTC)[reply]

How many SR-71's or X-15's buzzed the Dead Sea? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:53, 2 November 2019 (UTC)[reply]

But Baseball Bugs, the term "at sea level" in relation to air speed doesn't mean actually flying level with the surface of the sea (which as you say would be dangerous), it means flying at "standard sea level air density", at least according to our Equivalent airspeed article. Alansplodge (talk) 17:51, 3 November 2019 (UTC)[reply]

This is definitively a military secret. It depends on temperature in theory but these "crafts" are build to "work" securely at a given height far above sea level anyway, so its nonsense to ask. Also they are build to fly long distances for their purpose, so their top-speed is actually not that high (X-15 2000m/s) compared to for example the russian S-500 missile systems that manage 7000m/s but "just" over 600km distance. --Kharon (talk) 05:09, 2 November 2019 (UTC)[reply]

You can't really compare speeds of planes and missiles, that's apples and oranges. But yes, they can only reach top speed in thin air, so their speed at sea level would be far less. SinisterLefty (talk) 05:27, 2 November 2019 (UTC)[reply]

Going on a tangent; reading our article on the S-500, as well as other sources, indicates that the S-500 is claimed to be capable of intercepting a target moving at 7000m/s, NOT that the missile itself is capable of achieving that speed (intercepting a fast missile with a slower missile isn't all that hard, as long as you don't get caught in a tail chase). The missile itself is likely developed from the missiles used on the S-400, which have speeds up to 3840m/s. WegianWarrior (talk) 06:01, 2 November 2019 (UTC)[reply]

According to page 5-9 in the declassified SR-71 flight manual, the Blackbird was restricted to a "mere" 500 knots equivalent airspeed... which at sea level with a standard atmosphere should equal 257.2 m/s (575.4 mph / 926 kmh / 0.75 Mach). Further reading in the manual indicates the limiting factor was the compressor inlet temperature (CIT), which should not exceed 427°C (800.6°F).

According to the declassified flight manual for the X-15, section V, the absolute speed limit at sea level is comparable to the SR-71. However the limiting factor for the X-15 is the max q, which should not exceed 2200PSI (154kg/cm2 / 151.7 bar) to avoid structural damage.

To summarise; both the SR-71 and X-15 was built to reach high speed at high altitude. Near or at sea level they would have to fly at roughly the same speed as a modern airliner's cruise speed to avoid damage (engine and/or structure). WegianWarrior (talk) 05:50, 2 November 2019 (UTC)[reply]

Bob and Ray once proposed a satellite that would orbit 6 feet off the ground, so advertising could be posted on it. The notion of flying such high-speed aircraft at sea level is a similarly silly idea. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:28, 2 November 2019 (UTC)[reply]

A quick back of the envelope calculation gives an orbital speed for such a satellite of 7905m/s, which is clearly too fast to be able to read^{[citation needed]} any advertisements posted on it... WegianWarrior (talk) 14:13, 2 November 2019 (UTC)[reply]

Bob and Ray were satirists. :) And I say again, if those high-speed planes were flying at sea level anywhere except places like Death Valley and the Dead Sea, they would soon become ladened with water. I'm still trying to comprehend what the OP is trying to get at. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:26, 2 November 2019 (UTC)[reply]

In practice sea level V_NE speed shouldn't be much lower than buzzing the ocean in good weather. They were optimized for high altitude but I was just wondering if the fastest manned plane and plane* could fly really fast by low altitude standards too. But now I know that the X-15 was a structurally weak rocketplane that could only break speed records in extremely thin air and that the unique or nearly unique air compression heat surviving Blackbird features I've heard about do not include "engine that isn't destroyed by ~9/11 airliner speeds". Apparently it's so good at collecting air that it can exceed 800°F before the "turbocharger". Which can compress air to 8.8 times inlet pressure.Sagittarian Milky Way (talk) 16:45, 2 November 2019 (UTC)[reply]

Keep in mind that both the experimental X-15 and the reconnaissance Lockheed SR-71 Blackbird are in the past tense. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:34, 2 November 2019 (UTC)[reply]

Wiki-markup lacks tags for marking tounge-in-cheek humour and intentionally missing the point - there are a couple of issues with a 6' orbit apart from going to fast to read... :P

Both the X-15 and SR-71 was built to be good at one thing, and that thing was not going very fast low down. I'm actually surprised to see just how low the load factor of the SR-71 was at full speed (-0.1 to 1.5G, compared to the F-16's -3 to 9G). WegianWarrior (talk) 20:18, 2 November 2019 (UTC)[reply]

FWIW (i.e. not much), you do not need to search online very long to find claims of varying reliability that the true top speed of the Blackbird was higher than publicized - according to some claims, as high as Mach 4. In instances like this, there are competing agendas where the government obviously doesn't want to publicize their actual mission limits, while pilots and people who were involved in the Skunk works are obviously proud of this incredible machine. There's no way to know for sure at this point. Matt Deres (talk) 00:23, 3 November 2019 (UTC)[reply]

A few weeks back, Brian Shul gave a presentation at the Museum of Flight. As he writes in his book Sled Driver, the top speed (and V_NE, for that matter), was really fast.

As an aside, I have frequently pointed out to many of my friends and colleagues that the fastest, highest, and most secret airplane ever built did not ever carry munitions: the SR-71 was a giant carrying-case for a very fast telephoto camera. More on the topic: ...Overhead Reconnaissance (1992). That book cites some speed and altitude numbers for the aircraft, but it also describes some different speed and altitude considerations for its payload...

Nimur (talk) 16:28, 6 November 2019 (UTC)[reply]

What is the rate of Rapid Eye Movement?

In what speed do eyes move in the REM sleep phase? One source I found (and I couldn't find another) stated an average rate of 15 ’cycles’ a minute. That's a cycle in 4 seconds, pretty much the speed you'd move your eyes if someone asked you to ’move your eyes slowly from side to side’. If that source is correct, why keep calling it REM and not SEM? Gil_mo (talk) 18:05, 2 November 2019 (UTC)[reply]

I think by 'cycle' your source may have meant distinct 'clusters' of movements, with successive clusters separated by an average around 4 seconds. In films of REM I've seen, the eyes when moving made a few movements in short 'bursts' of a couple of seconds or less each, separated by a few seconds of stillness. {The poster formerly known as 87.81.230.195} 2.122.179.237 (talk) 20:05, 2 November 2019 (UTC)[reply]

Could you please place some links to those videos? Thanks Gil_mo (talk) 08:58, 3 November 2019 (UTC)[reply]

Videos of interest: Baby REM sleep. Stages of sleep: [3], [4], See REM waves at 3:10, Sleep basics, See REM at 7:35. Normal sleep EEG: [5], [6]. REM sleep disorder RBD: [7], [8], [9]. DroneB (talk) 15:23, 3 November 2019 (UTC)[reply]

Thanks, will definitely look at those!! Gil_mo (talk) 05:43, 4 November 2019 (UTC)[reply]

As you can see in the first (cute) video, the eyes are moving at a fairly slow rate. None of the other videos/talks are mentioning the actual eye movement, but rather the brain waves connected with the eyes. Gil_mo (talk) 09:01, 6 November 2019 (UTC)[reply]

November 3

Atmosphere suitable for humans?

Let's ignore possible airborne pathogens as factor for this question. How much differences an atmosphere of an exoplanet could have compared to the Earth's current one in order for humans to still be able to function effectively without negative effects on the body? For example, if a planet has an atmosphere like the one on Earth during the Carboniferous period with 30% oxygen in composition, would it still be safe for humans to breathe freely in it? What about increased pressure at the surface? 70.95.44.93 (talk) 01:10, 3 November 2019 (UTC)[reply]

What a great idea to get into theoretical questions. Though are you sure the Earth's atmosphere has ever been 30%? I've seen a table in a microbiology textbook on how long the atmopshere was been 21% - since 800-900 million years ago, 10% at 1.25 billion years ago, and 1% at 1.9 million years ago. 67.175.224.138 (talk) 01:24, 3 November 2019 (UTC).[reply]

Regarding the 30% figure, the graph at the start of our Great Oxidation Event (showing the upper and lower estimates for peak P_O₂ of about 0.33 atm & 0.20 atm) is from Heinrich Holland who wrote in 2006 that "Atmospheric oxygen levels during stage 5 (0.54 Ga–present) probably rose to a maximum value of ca 0.3 atm during the Carboniferous before returning to its present value.".

Also, the lede of Carboniferous says, "The atmospheric content of oxygen also reached its highest levels in geological history during the period, 35%[7] compared with 21% today, allowing terrestrial invertebrates to evolve to great size.[7]"" with the reference being David Beerling's 2007 The Emerald Planet. -- ToE 15:23, 3 November 2019 (UTC)[reply]

Since we don't use nitrogen from the air, it could be completely removed, and either replaced by another inert gas, or we could have lower pressure but with the partial pressure of oxygen similar to what it is here. We also don't need carbon dioxide in the air, so that could be eliminated. Of course, plants would die, but you didn't ask about those. So, when you get right down to it, all we really need is oxygen, and some water vapor so we don't dry out. SinisterLefty (talk) 01:55, 3 November 2019 (UTC)[reply]

[Edit conflict] The human body can cope with pressures several times the current norm, as when using Scuba or other apparatus in deep dives. Problems with the bends may arise when returning to normal atmospheric pressure, but living for extended periods, or permanently, under such pressure seems to be possible.

Markedly lower pressures will be limited by the body's requirement, even after acclimatization, for a minimum amount of oxygen – biologically this would be around 1/5 current atmospheric pressure if 100% oxygen, but such an atmosphere would be impractically flammable in combination with fuel materials such as plants. Of course, an absence of toxic gases (where toxicity is dependent on their partial pressure) would be a prerequisite.

Permanent use of relatively simple breathing apparatus might well extend the limits of atmospheric composition somewhat. A more critical restraint might be ambient temperatures. Such considerations have of course been studied in the context of a future Mars habitat. {The poster formerly known as 87.821.230.195} 2.122.179.237 (talk) 02:16, 3 November 2019 (UTC)[reply]

I don't believe 100% oxygen would increase flammability, as long as the partial pressure of oxygen remains the same, because no more oxygen is available than before. Or are you thinking the nitrogen in our air interferes with combustion ? SinisterLefty (talk) 03:19, 3 November 2019 (UTC)[reply]

The nitrogen interferes with combustion by taking away some of the heat. Suppose you burn one carbon atom with one oxygen molecule. That gives one very energetic carbon dioxide molecule. Now add four nitrogen molecules. The heat gets spread over all molecules (not completely equally, as the carbon dioxide has more internal degrees of freedom), resulting in less kinetic energy per molecule and therefore a cooler flame. PiusImpavidus (talk) 09:12, 3 November 2019 (UTC)[reply]

Yep. Oxygen Partial Pressure and Oxygen Concentration Flammability:Can They Be Correlated? (Journal of ASTM International, 2016). Last sentence of abstract: "The findings presented in this paper suggest flammability is more dependent on oxygen concentration than equivalent partial pressure." I was looking for an older NASA paper which said the same thing (without proposing a mechanism) when I found this one. I think the phenomenon is at first counter-intuitive to those who work with hyperbaric physiology where equivalent partial pressure is paramount. -- ToE 12:56, 3 November 2019 (UTC)[reply]

Does the (partial or real) pressure of carbon dioxide of air in respiration affect the exchange of CO₂ out of the blood, and therefore affect things like carbonate pH buffering? Or is 0.04% too low to have a relevant effect? DMacks (talk) 02:35, 3 November 2019 (UTC)[reply]

I believe it is too low to matter, since those filling oxygen tanks don't bother to add in carbon dioxide. SinisterLefty (talk) 03:23, 3 November 2019 (UTC)[reply]

Earth's atmosphere may be relevant (note that they don't include water vapor in the pie chart, since the proportion is too variable). SinisterLefty (talk) 03:20, 3 November 2019 (UTC)[reply]

Inert gas partial pressure may be a concern at elevated absolute pressure due to Nitrogen narcosis. Extended exposure to oxygen at elevated partial pressure may be a concern due to Oxygen toxicity. — Preceding unsigned comment added by 2A01:E34:EF5E:4640:6450:7CCB:76D1:CFE1 (talk) 08:02, 4 November 2019 (UTC)[reply]

Iron-rich food

If blood slightly tastes iron, why iron-rich food doesn't taste iron as well? Also relevant to food reach in other elements. Thanks. 212.180.235.46 (talk) 12:10, 3 November 2019 (UTC)[reply]

The taste or smell is actually due to Oct-1-en-3-one. This is made when oxidised skin lipids meet ferrous iron ions. The food may not contain free iron in this form. The iron will usually be trapped in metalloproteins in a sulfur rich cluster and not be free to make the odorant. Graeme Bartlett (talk) 12:37, 3 November 2019 (UTC)[reply]

Doesn't liver have an iron taste ? SinisterLefty (talk) 16:22, 3 November 2019 (UTC)[reply]

It doesn't really taste like iron, it just tastes like liver. Which is gross enough. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:17, 3 November 2019 (UTC)[reply]

Seems to taste metallic to me, which is why it's so nasty. SinisterLefty (talk) 03:05, 4 November 2019 (UTC)[reply]

You're supposed to cook it first. 93.136.71.107 (talk) 22:37, 4 November 2019 (UTC)[reply]

Cook it long enough, and you can use it to re-sole your shoes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:48, 5 November 2019 (UTC)[reply]

The taste we associate with metals isn't really a taste, it is a smell. What we think of as "flavor" is mostly smell, strictly speaking we can only taste the 4-5 basic tastes of bitter, sour, sweet, salty and umami. Any other aspect of taste is really smell which your brain interprets as taste as your mind merges the two senses into a single sensation. What we think of as "metallic" actually isn't the metal at all. Metals neither activate taste buds nor produce a vapor that you can pick up in your olfactory senses. Instead, what you smell or taste is usually the compound Oct-1-en-3-one, or other related compounds, which is mentioned above. This class of compounds are produced when metals react with various compounds (such as the oils in your skin or components of your saliva) to produce a sensation we learn as "metallic". This video is a pretty good explanation. --Jayron 32 14:53, 4 November 2019 (UTC)[reply]

What's an easy method or solvent to remove the odor from strongly metal-scented metal objects? That would be a real nose opener about the common myth that metals evaporate far below their melting point. Sagittarian Milky Way (talk) 18:40, 4 November 2019 (UTC)[reply]

Watch the video. He explains that. --Jayron 32 19:01, 4 November 2019 (UTC)[reply]

There are also other elements that contribute to the experience of consuming a food, such as mouthfeel. Fatty foods tend to "coat" the inside of the mouth, and depending on composition may also start to melt from body heat, chocolate being a good example. Tannins and some other compounds create an astringent sensation. Spicy foods contain chemicals that don't act on taste receptors, as you noted, but instead on other receptors located on skin and mucous membranes. --47.146.63.87 (talk) 01:14, 5 November 2019 (UTC)[reply]

Touchscreens.

Some of these touchscreens like at the self-checkout at grocery stores, don't work if you tap while wearing gloves on. Even the kind of gloves that are like a cloth, even with tapping the screens really long and hard. So as soon as I take the gloves off and tap with my fingertips, it works. How does it know human skin from gloves? My only guess is human emits weak IR radiation but I doubt that's the case. 67.175.224.138 (talk) 12:28, 3 November 2019 (UTC).[reply]

see Touchscreen#Capacitive and Capacitive sensing to see how this works (or not). Graeme Bartlett (talk) 12:39, 3 November 2019 (UTC)[reply]

So gloves block an electrostatic field, making an unmeasurable change in capacitance? 67.175.224.138 (talk) 12:45, 3 November 2019 (UTC).[reply]

It's measurable. They also make special gloves for use with touchscreens. SinisterLefty (talk) 16:24, 3 November 2019 (UTC)[reply]

Why point out a contradiction? 67.175.224.138 (talk) 17:03, 3 November 2019 (UTC).[reply]

What contradiction? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:33, 3 November 2019 (UTC)[reply]

What I copy/pasted. 67.175.224.138 (talk) 17:48, 3 November 2019 (UTC).[reply]

You didn't copy/paste anything in this section, that I can see. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:16, 3 November 2019 (UTC)[reply]

From the see Touchscreen#Capacitive, I copy/pasted the 2nd sentence then put it in a form of a question. 67.175.224.138 (talk) 00:54, 4 November 2019 (UTC).[reply]

OK, I meant that the difference in capacitance between touching the screen (with) or (without gloves) is measurable, while you meant that it makes the difference in capacitance when touching the screen too small to detect, when wearing gloves. Both are true. Or perhaps the difference in capacitance could still be detected when wearing gloves, but setting the sensitivity that high would also mean it would have false positives, thinking it detected a touch, when a fly lands on the screen, for example. SinisterLefty (talk) 03:03, 4 November 2019 (UTC)[reply]

I can attest to the existence of the fly problem on Amazon Kindle. You'd never expect such quick page flipping from those tiny legs... 93.136.71.107 (talk) 22:35, 4 November 2019 (UTC)[reply]

If you were reading Charlotte's Web, your fly would get trapped on the screen. :-) SinisterLefty (talk) 02:01, 5 November 2019 (UTC) [reply]

The touch screens are designed to detect the capacitance when actually touched, so if the finger is just near the screen it does not trigger. It would be hard to use if it was so sensitive. Graeme Bartlett (talk) 21:13, 4 November 2019 (UTC)[reply]

Okay going back to gloves block an electrostatic field, what electrostatic field, from the touchscreen, or from the human body? 67.175.224.138 (talk) 15:20, 6 November 2019 (UTC).[reply]

Lethal bronzing?

Here is a definition. I'm surprised it's not on Wikipedia. Also palm oxids.— Vchimpanzee • talk • contributions • 19:50, 3 November 2019 (UTC)[reply]

The Mark Trail comic led me to search Haplaxius crudus, which has an extremely brief article but points to lethal yellowing, which appears to be the article you're looking for. A redirect from "lethal bronzing" might make sense, assuming the comics people didn't just make a mistake. --Trovatore (talk) 20:04, 3 November 2019 (UTC)[reply]

Thanks. He usually seems to know what he's talking about but occasionally the commenters will catch a mistake.— Vchimpanzee • talk • contributions • 20:57, 3 November 2019 (UTC)[reply]

@Vchimpanzee: Actually a quick search suggests that the correct article is Texas phoenix palm decline, a related disease to lethal yellowing but apparently not exactly the same. See here. I'll go ahead and make the redirct to that article. --Trovatore (talk) 21:16, 6 November 2019 (UTC)[reply]

Okay, thanks.— Vchimpanzee • talk • contributions • 22:44, 6 November 2019 (UTC)[reply]

November 4

Smallest animal with red blood

Which is the smallest animal which has red blood along with bones — Preceding unsigned comment added by 42.110.198.41 (talk) 06:21, 4 November 2019 (UTC)[reply]

I understand that fish have red blood, with a few exceptions [10], so look at our list of smallest fish for some possible contenders for the title. SinisterLefty (talk) 06:41, 4 November 2019 (UTC)[reply]

The smallest vertebrate, according to Wikipedia, is the tiny frog Paedophryne amauensis. The article doesn't address whether it has red blood, but nearly all vertebrates do, so that seems likely. Dragons flight (talk) 10:36, 4 November 2019 (UTC)[reply]

The frog may be slightly shorter, on average, but some of the fish in the list above appear to have the lower volume/mass/weight. SinisterLefty (talk) 14:20, 4 November 2019 (UTC)[reply]

Cochineal?--Shantavira|^{feed me} 17:19, 4 November 2019 (UTC)[reply]

I don't think that's blood per se (insects don't have circulatory systems), and of course cochineal isn't a vertebrate. --jpgordon^{𝄢𝄆 𝄐𝄇} 17:30, 4 November 2019 (UTC)[reply]

Hmmm? --Jayron 32 19:00, 4 November 2019 (UTC)[reply]

That link says it's more like lymph than blood. SinisterLefty (talk) 21:23, 4 November 2019 (UTC)[reply]

That link says that there's a circulatory system, which contradicts the statement "insects don't have circulatory systems". The problematic statement wasn't "I don't think that's blood per se", which is correct, it isn't blood, it's hemolymph. However, insects do have a circulatory system that pumps the substance around their bodies. --Jayron 32 12:07, 5 November 2019 (UTC)[reply]

Thanks for the clarification. However, it would be helpful if you initial responses would be clearer. SinisterLefty (talk) 14:33, 5 November 2019 (UTC)[reply]

Fair point. I will work harder to be a better person in the future. --Jayron 32 14:35, 5 November 2019 (UTC)[reply]

Cochineal don't have blood or bones. "The insect produces carminic acid that deters predation by other insects. Carminic acid, typically 17-24% of dried insects' weight, can be extracted from the body and eggs, then mixed with aluminium or calcium salts to make carmine dye, also known as cochineal". Richerman (talk) 17:37, 4 November 2019 (UTC)[reply]

I squished a couple a week ago. It sure leaves a nice stain on the skin. --jpgordon^{𝄢𝄆 𝄐𝄇} 17:46, 4 November 2019 (UTC)[reply]

Are there smaller ones with red blood and no bones? Sagittarian Milky Way (talk) 19:09, 4 November 2019 (UTC)ll[reply]

Earthworms have hemoglobin in their circulatory system, and so have red blood. Not all annelids use hemoglobin, some use chlorocruorin, which isn't red (it's amazing how a small change to the conjugated pi system can have such a drastic change in color). Some echinoderms have hemoglobin as well, at least sea cucumbers. --OuroborosCobra (talk) 21:42, 4 November 2019 (UTC)[reply]

Apparently planorbidae, unlike other mollusks, also have hemoglobin, and red blood, as opposed to green copper based blood. Several forms of crustaceans use hemoglobin. I would bet there is where you will find the smallest organisms with red blood. --OuroborosCobra (talk) 21:49, 4 November 2019 (UTC)[reply]

Offsprings and mutations

I've heard a concern which says that because insects on average produce more offsprings than many other mammals, including humans, their adaptive radiation should have progressed faster due to higher probability of mutations in every generation. Yet, despite their species diversity, the insects remained basically the same on average as they were millions years ago whereas most mammals evolved noticeably faster despite less offsprings (in case of human evolution, on the order of "some 15–20 million years ago" starting from the divergence of the Hominidae). The number of orders in insects also stays roughly similar to that of mammals (around 30 vs 26). Why is that? Thanks. 212.180.235.46 (talk) 17:33, 4 November 2019 (UTC)[reply]

why do you say that "insects remained basically the same"? Because a few insect species you know (that is, very successful) appeared long ago? Rest assured that quite a number were wiped out. Or because the differences between, say, a Macrotermes and a Nasutitermes mean less to you that the difference between, say, a chimpanzee and a gorilla?

Tree(g) numberphile video

In a recent numberphile video "Tree vs Graham's number", rates of growth of series are compared to a hierarchy of functions called f0(x) defined as x+1 and then fn(x) defined by applying f{n-1} x times.

Do these functions have a name that I could look up?

2A01:E34:EF5E:4640:6450:7CCB:76D1:CFE1 (talk) 17:53, 4 November 2019 (UTC)[reply]

Consult large numbers and Names of large numbers Gem fr (talk) 18:05, 4 November 2019 (UTC)[reply]

found it by indirection from that article: Grzegorczyk hierarchy. Thanks.

2A01:E34:EF5E:4640:6450:7CCB:76D1:CFE1 (talk) 19:23, 4 November 2019 (UTC)[reply]

What is the accuracy of a lodestone on a string or a temporarily magnetized needle floating in a cup at different Earth field strengths?

Are these sensitive enough to show magnetic north till magnetic reversal temporarily causes more than two poles? I've made a non-magnetic needle work by rubbing it 100 times in the same direction with a small and weak permanent magnet, how much could Earth's field weaken before you'd need a stronger magnet, longer pointer or a more magnetizable material? Sagittarian Milky Way (talk) 18:23, 4 November 2019 (UTC)[reply]

It works fairly well. I am a science teacher who sometimes teaches a class called "Physical Science" where we discuss magnetism at some point. I have, for years, had a magnet hanging from a string attached to my ceiling. It has been pointing at magnetic North for at least 6 years at this point. At no time has it suddenly stopped pointing north. In general, any magnet will, if properly suspended and without too much friction to overcome, align itself with the local magnetic field and will point at magnetic north. In a frictionless (ideal) environment, every magnet will align itself with the magnetic field; it is only when friction prevents it that it doesn't. --Jayron 32 18:56, 4 November 2019 (UTC)[reply]

Also note that the magnetic north pole isn't exactly at the geometric north pole, and it also moves around and isn't exactly on the opposite side of the Earth from the magnetic south. So, all magnetic compasses could be off at some time in the future, prior to magnetic reversal. To some extent, we can compensate for the difference between magnetic north and true north (or the two south poles) if we know approximately where on Earth we are. Of course, these days we have many other options to use satellites and such, so putting too much effort into regularly adjusting magnetic compasses may not make sense. SinisterLefty (talk) 21:13, 4 November 2019 (UTC)[reply]

If the friction was low enough for it to not get stuck off azimuth your compass wouldn't be off, your map's declination would be. Sagittarian Milky Way (talk) 21:43, 4 November 2019 (UTC)[reply]

Lodestones were not widely used directly for making a compass. For one thing, they were too expensive to travel with. More commonly, a steel compass needle would be magetised with a lodestone in a workshop, then that would be used. This was also lighter, so responded more quickly to movement. Although you can use a suspended lodestone as a compass, they're very inconvenient on any sort of moving ship - mass and inertia swamps the magnetic effects.

It was recognised early on that iron and steel behaved differently as magnets, see remanence. An iron compass needle worked fine, but would lose its magnetism over a voyage (some well-funded ships carried a lodestone, and could use this to restore the magnetisation). This was even seen as a test of the quality of the steel. The traditional association of compasses and needles comes about not just from their shape, but because a sewing needle was often the only commonly available source of high-quality steel with good remanence, and they were also a convenient size and shape.

For a static compass, such as in surveying, a weakly magnetised needle will eventually settle. For use on ship, the more magnetic field it can produce gives more restoring torque, thus less sensitivity to interference from movement. Andy Dingley (talk) 11:14, 5 November 2019 (UTC)[reply]

November 5

Noble metals (Ru–Pd; Os–Au)

Why do the noble metals have such high electronegativity values (2.2 to 2.54)? — Preceding unsigned comment added by Sandbh (talk • contribs) 01:50, 5 November 2019 (UTC)[reply]

I don't know but if they were very low or high they couldn't be noble. They're also in the middle of the table where you would expect middling values. Sagittarian Milky Way (talk) 02:19, 5 November 2019 (UTC)[reply]

{{ec}} Looking at the table at Electronegativity#Electronegativities of the elements reveals an even more (by eye:) anomaly in Group 6 (Cr, more dramatically Mo, and even more dramatically W, as compared to the adjacent Group 5 and Group 7;. And most of the transition-metal block has electronegativity increasing down each group, which is again not the usual trend. DMacks (talk) 02:21, 5 November 2019 (UTC)[reply]

Maybe it has something to do with metallophilic interactions? Droog Andrey already explained this for Mo and W here: "Mo/W electronegativity is higher only on Pauling scale because of strong multiple homoatomic bonds between their atoms. In chemical sense, their electronegativity is not very high." Given aurophilicity the same thing may be at work for Au. Though I notice that Smokefoot also mentions there that apart from Au, electronegativity of metals is not really mentioned much in inorganic chemistry because ligands are much more important for determining the properties of complexes. Double sharp (talk) 07:59, 5 November 2019 (UTC)[reply]

BTW, note that Droog Andrey's electronegativity scale (which is on the table he and one of his colleagues publish) seems to be accounting for this and trying to show electronegativity in his "chemical sense". On that scale (with Li through Ne fixed at 1.00 through 4.50 at intervals of 0.50), the noble metals are not so high, only 1.62 to 1.93. (Including Hs through Rg brings the upper limit only to 1.99.) Though note that even here, Au (1.93) still shows up as more electronegative than Si (1.90) and almost on par with Rn (1.94); Rg (1.99) even shows up between Ge (1.96) and B (2.00). So I guess gold is still somewhat special, even if the rest aren't really, corroborating Smokefoot's observation. Ds, Rg, and Cn should also be special in that way if you could get any significant amount (which, at the moment, you really can't). (Pt appears at 1.84, between Pb and Sn at 1.82 and 1.86 respectively; the rest appear further away, behind Ga, Cu, and sometimes even the rather active Ni and Zn.) Double sharp (talk) 08:07, 5 November 2019 (UTC)[reply]

The answer for the OP is that electronegativity is a model, and all models are wrong (though some are useful). In the case of electronegativity, the scale is quite useful for determining bonding polarity among main group elements, but the model starts to break down when you get to the transition elements. As noted above, there have been some attempts to correct the scale so that there are not the anomalies you find with transition metals. --Jayron 32 12:03, 5 November 2019 (UTC)[reply]

There are some other correlations with the high EN values of the noble metals. They occur free in nature. They collectively have the highest standard reduction potentials of the metals. They have among the highest ionization energies of the metals. Ditto electron affinity.

In period 5, I see that Ru Rh and Pd are in a race to complete their 4d subshell, so much so that Ru and Rh each have only one 5s electron, and Pd has none. Contrast their lighter 3d congeners Fe, Co and Ni each of which have full 4s² subshells. I guess that the energy levels of the period 5 4d and 5s subshells are closer together, which facilitates movement by the 5s electrons (as influenced by the nuclear charge?).

I'm not that puzzled by the period 6 noble metals Os Ir Pt and Au, since they "suffer" from poor shielding by their 4f¹⁴ electrons. And I understand relativistic effects cause a contraction of their s orbitals, which presumably increases exposure to the nuclear charge. Sandbh (talk) 00:24, 7 November 2019 (UTC)[reply]

Horizon

Horizon#Examples says that for an observer standing on the ground with h = 1.70 metres, the horizon is at a distance of 4.7 kilometres. Unless I'm missing something, this looks too large. On a city street in a clear day I, standing 1.80 m tall, without elevation, see to a distance of around 1 km at most with unobstructed view and certainly not 4.7 km. To see or spot objects that far from me I need to walk or ride further. Do I misunderstand something? 212.180.235.46 (talk) 22:39, 5 November 2019 (UTC)[reply]

Very slight slopes of 1 part per hundreds would be enough to make the horizon a kilometer away. Sagittarian Milky Way (talk) 00:46, 6 November 2019 (UTC)[reply]

They aren't considering visibility. In many places fog or smog makes 4.7 km visibility quite rare. You said a city street, so some pollution is to be expected. It isn't all that apparent when pollution limits visibility from 4.7 km to 1 km. SinisterLefty (talk) 04:31, 6 November 2019 (UTC)[reply]

I was always told that a man of 2 meters could see 5 km if he was standing on the beach on a clear day. Hence without any obstruction or without any hills. I would suspect that this should be a known calculation and could quite easily be calculated by using the circumference of the earth. This may be best referred to the Mathematics desk... Thanks. Anton 81.131.40.58 (talk) 09:06, 6 November 2019 (UTC)[reply]

The math is literally given at the article linked by the OP. Someguy1221 (talk) 09:13, 6 November 2019 (UTC)[reply]

If the the temperature graph by altitude is unusual enough it can also refract the horizon closer. Sagittarian Milky Way (talk) 13:20, 6 November 2019 (UTC)[reply]

And if there's a dark surface in the direction viewed, rising and falling air currents of different temperatures and densities can also cause visual distortions. SinisterLefty (talk) 16:16, 6 November 2019 (UTC)[reply]

In a city you're really unlikely to find ground flat enough that you could see it curve away. Even roads that look totally flat to the naked eye can have a rise or a drop of a meter per kilometer, which is only felt by cyclists and probably creates the appearance that the road is flat but disappears behind the horizon too soon (when the rise breaks). Even if you're standing on a truly flat and straight road, but there's a two-meter-tall invisible hillock a kilometer away, it will still end your horizon. 93.142.93.32 (talk) 22:15, 6 November 2019 (UTC)[reply]

November 6

air conditioner refrigerant charge refill

I recently had had the refrigerant charge within my air conditioner refilled. The procedure was the same as described here[11][12]. But since I live in a high-rise building and my compressor is installed outside, the worker had to put on a safety harness, climb out my window, and carry the heavy steel refrigerant container with him to recharge the compressor unit. Needless to say it looked horrifically unsafe, but the worker told me there was no way to refill the refrigerant charge through the indoor unit. A quick search online would confirm this. I haven't been able to find any split-unit AC that you can refill through the indoor unit.

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor

My understanding is that the outdoor compressor and the indoor unit make up a sealed loop. How come it's not possible to inject refrigerant using the indoor part of this loop? Mũeller (talk) 04:15, 6 November 2019 (UTC)[reply]

The hot side should be at highest pressure normally, and thus designed to withstand higher pressure. Assuming the refill tank is at a comparable pressure, then injecting it into the low-pressure (cold) side might cause a leak, unless done very slowly while the A/C operates. If nothing else, you would think the manufacturer would provide a valve that leads to the high pressure side from the inside of the building, for service. SinisterLefty (talk) 04:28, 6 November 2019 (UTC)[reply]

According to the instructions, the AC is supposed to be recharged in the powered off state. Wouldn't the pressure be equalized after power has been off for a few minutes? Mũeller (talk) 04:47, 6 November 2019 (UTC)[reply]

That would depend on the design. The compressor probably prevents back-flow, and at the other end there may be a valve that closes, when off, to prevent pressure equalization. That would make it start up faster, more efficiently, and would avoid them having to make the cold side able to withstand high pressures. SinisterLefty (talk) 04:56, 6 November 2019 (UTC)[reply]

I see. That makes a lot of sense. Thank you!Mũeller (talk) 07:57, 6 November 2019 (UTC)[reply]

There are two filling ports: high pressure and low (usually coded red and blue). A refill manifold has a hose to the gas cylinder or vacuum pump (yellow hose) and valves and gauges to the high and low sides.

It's possible to refill low-side if it's only a minor top-up, but any significant refill needs to be done on the high side. For a through-wall unit, they're all in the same box and access is easy. If it's a split unit though, you'll need access to the piping around the condenser, somewhere between the compressor and the expansion valve - all of which is likely to be in the outside box, where the condenser needs to be, where the compressor is to avoid indoor noise, and where the expansion valve is so that the long flexible pipes between the boxes are all in the low-pressure part of the circuit.

They could provide a limited-use high pressure connection from indoors to outdoors, just for filling. I'm sure somewhere will have done this, for some application where access is particularly awkward. But it's not usual, just to avoid long high-pressure pipe runs.

It's also necessary to run the compressor a little, during the filling process, just to circulate the gas and ensure that the whole loop has been filled correctly. Andy Dingley (talk) 15:47, 6 November 2019 (UTC)[reply]

STIs emergence

How exactly STI pathogens, like bacteria, got onto humans in the first place? This only says that such diseases were known since antiquity, but it seems that the human-to-human transmission chain of all STIs should have its origin somewhere, similar to HIV emergence (something like evolutionary jump or picking up from soil). Thanks. 212.180.235.46 (talk) 12:07, 6 November 2019 (UTC)[reply]

See Coevolution. One likely possibility is that the pathogens may have been infecting species along the human ancestral chain back millions of years, and have evolved along with us. Or someone has some weird kinks... --Jayron 32 12:56, 6 November 2019 (UTC)[reply]

Also, a disease which wasn't solely sexually transmitted could have evolved to specialize in that mode of transmission, perhaps splitting from the original form, perhaps replacing it. Viral hepatitis is a disease which currently has multiple modes of transmission, with only Hep B being primarily sexually transmitted. SinisterLefty (talk) 16:22, 6 November 2019 (UTC)[reply]

Quote, R. D. Laing " Life is an STI with 100% fatality" Thanks Anton 81.131.40.58 (talk) 16:44, 6 November 2019 (UTC)[reply]

Just to avoid confusion, diseases don't really undergo biological evolution. Their agents do. This is an important distinction as illustrated by the example. From a quick look, the Hepatitis viruses: Hepatitis A virus, Hepatitis B virus, Hepatitis C virus, Hepatitis D virus, Hepatitis E virus don't seem particularly related to each other. While viral evolution is complicated and it's particularly difficult to discern the early evolutionary history, it's likely that the fact these cause similar diseases is more a result of convergent evolution and the mammalian host body. In fact, I just notice that Viral hepatitis mentions the unrelated bit. Hepatitis D seems a particularly interesting case, it requires a concurrent hepatitis B infection. See e.g. [13] [14] [15], Nil Einne (talk) 16:54, 6 November 2019 (UTC)[reply]

To clarify an additional point, a number of Sexually transmitted infection aren't exclusively sexually transmitted. This is particularly the case for viral diseases which may simply require blood or some other bodily fluids without even requiring contact with the genital area, HIV is far from an outlier. Bacterial STIs are more complicated, as quite a few of these only really infect the genital area and so at a minimum require contact with those. Still, these don't necessarily require weird kinks, someone contacting some non humans genital area such as when they are eating it (assuming no cooking) or preparing it to be eaten may not be that unlikely, and touching their own genital area not that long later, again maybe not that unlikely. While transmission through this means may be very rare, it may only take one case. That said, I suspect most STIs have simply coevolved as Jayron32 suggested. Nil Einne (talk) 17:16, 6 November 2019 (UTC)[reply]

Our article on History of syphilis may be instructive in showing how difficult it can be to determine the origins of a disease, even ones as sensational and infamous as syphilis. Matt Deres (talk) 20:21, 6 November 2019 (UTC)[reply]

Is there an element, alloy or other substance

That is less dense than osmium but, if the pressure got high enough, is predicted to compress to a higher density than osmium would at the same pressure? Sagittarian Milky Way (talk) 21:39, 6 November 2019 (UTC)[reply]

neutron, as in neutron star? Gem fr (talk) 22:46, 6 November 2019 (UTC)[reply]

As I understand it, the pressure needed to create neutron-degenerate matter, loosely called neutronium, would inevitably convert osmium and any other substance to neutron-degenerate matter also. The density of a single neutron is calculated here, and shown (at 3.0 x 10²⁶ kg/km³) to be 1.5 x that of a neutron star (which contains more than just neutronium). My back-of the envelope calculation (which may well be wrong – corrections welcome!) indicates this is about 1.3 x 10¹³ times the density of osmium at STP, FWIW. {The poster formerly known as 87.81.230.195} 2.122.179.237 (talk) 00:32, 7 November 2019 (UTC)[reply]

Construction companies

(Moved to Misc Ref Desk: Wikipedia:Reference_desk/Miscellaneous#Construction_companies. - SinisterLefty (talk) 04:44, 7 November 2019 (UTC) )[reply]

This is a conflict of ideology. Followers of capitalism will argue that its the "nature" of the system/humans to compete sometimes or even notorious beyond rules and regulations and that this ("free market") is in the end more helpful for society than Planned economy or more commonly called Socialism.

Strangely something called Third Way, a combination of both, seems to have won the competition historically. Unfortunately this includes benefits and flaws of both systems, including some companies that seem to exploit society and some that lake to much innovation to help society. Btw. there are 100001 books, studies and research papers about this out there. Go reading but you could aswell become a politician and waste your time that way. --Kharon (talk) 04:52, 7 November 2019 (UTC)[reply]

November 7

@@ Line 444: / Line 444: @@
 (Moved to Misc Ref Desk: [[Wikipedia:Reference_desk/Miscellaneous#Construction_companies]]. - [[User:SinisterLefty|SinisterLefty]] ([[User talk:SinisterLefty|talk]]) 04:44, 7 November 2019 (UTC) )
+:::This is a conflict of ideology. Followers of capitalism will argue that its the "nature" of the system/humans to compete sometimes or even notorious beyond rules and regulations and that this ("free market") is in the end more helpful for society than [[Planned economy]] or more commonly called [[Socialism]].
+:::Strangely something called [[Third Way]], a combination of both, seems to have won the competition historically. Unfortunately this includes benefits and flaws of both systems, including some companies that seem to exploit society and some that lake to much innovation to help society. Btw. there are 100001 books, studies and research papers about this out there. Go reading but you could aswell become a politician and waste your time that way. --[[User:Kharon|Kharon]] ([[User talk:Kharon|talk]]) 04:52, 7 November 2019 (UTC)
 = November 7 =