User talk:Cruithne9

Made quite major changes to the calcium metabolism page, which contained many inconsistencies. Hope this finds favor with the readers, as this is a very popular article. Cruithne9 (talk) 09:48, 25 May 2015 (UTC)

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 * fixed Cruithne9 (talk) 16:09, 14 June 2015 (UTC)

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 * fixed Cruithne9 (talk) 12:23, 11 July 2015 (UTC)

Motion of 3753 Cruithne is not an instance of the Coriolis effect
I'm not sure where you got this idea, but it is simply not true (I'm a PhD physicist, so I knew that immediately). They are completely unrelated effects, other than the fact that both are seen in rotating reference frames, they have no other connection.

I've removed your additions from those articles. Please remember that Wikipedia requires that any information added to articles be verifiable in reliable sources, and there are no reliable sources which would ever make that claim. I see that these were your first 2 edits to Wikipedia, and I hope that your subsequent edits conform better to our policies and standards (I don't have time to check them all). Thanks.--Seattle Skier (talk) 19:43, 17 July 2015 (UTC)


 * Hi Seattle Skier. I’m intrigued by your very brief explanation of the Coriolis effect. The Coriolis effect is a deflection of moving objects when the motion is described relative to a rotating reference frame. This rotating reference frame can be a turn table in your home, a rotating bowl of water in a laboratory, or the motion of water, air, or long-range ballistic missiles over the earth rotating on its axis. It also applies to the geographic paths seen to be taken by artificial satellites that orbit the earth, and it is a Coriolis “force” that keeps geostationary satellites above a fixed position on the earth’s surface. The curious motion of the planets that intrigued the ancients, but are now known, thanks to Copernicus, Galileo and Newton, to be due to Coriolis effects caused by the planets’ and the earth’s independent orbits round the sun. Similarly 3753 Cruithne’s strange orbit, as seen from earth is an example of the Coriolis effect. But, from what you say above, it seems that Coriolis mathematics does not apply, or is inappropriate at some arbitrary altitude above the earth’s surface. I’m obviously missing a very fundamental principle here. I’d very much appreciate getting the distinction of what happens when an ant on a turn table watches a fly fly straight across that turn table, and what happens when we, on our rotating and orbiting earth, look up into the skies at the objects in our solar system moving in accordance to Newton’s Laws. I’m sure that it has a very simple explanation, which I have overlooked. Cruithne9 (talk) 06:07, 20 July 2015 (UTC)


 * Cruithne9, you appear to be misunderstanding some basic physics here, such as the extent of what the Coriolis effect is and what it applies to, and you are thus misapplying it to cases which really have nothing to do with it. Take your statement that "it is a Coriolis “force” that keeps geostationary satellites above a fixed position on the earth’s surface." That is completely untrue: the Coriolis force $$\boldsymbol{ F}_C = -2 \, m \, \boldsymbol{\Omega \times v}$$ on a geostationary satellite is zero, because its velocity in the rotating frame is zero. In the rotating frame, it is entirely the centrifugal force $$\boldsymbol{ F}_c = - m \, \boldsymbol{\Omega \times (\Omega \times r)}$$ which is nonzero and keeps the satellite in place versus plummeting downward, not the zero Coriolis force.
 * Your next statement that the "curious motion of the planets that intrigued the ancients, but are now known, thanks to Copernicus, Galileo and Newton, to be due to Coriolis effects" is also completely untrue, although for different reasons than the prior statement. The "curious" apparent retrograde motion of the planets can be explained without any reference to Coriolis effects or to any fictitious forces at all, it is a simple case of geometry and does not even need Newton's laws or any physics at all to explain. See the diagrams in that article which should make this quite clear. Similarly, the motion of 3753 Cruithne can be explained by simple geometry in the rotating frame as shown in the animated image File:Horseshoe_orbit_of_Cruithne_from_the_perspective_of_Earth.gif, without needing Coriolis effects or any physics at all.
 * Your statement that "I’m obviously missing a very fundamental principle here" appears to be quite true. Hopefully these examples provide some of the very simple explanation which you have overlooked, and will make it clearer where the Coriolis effect actually applies, and where it does not. --Seattle Skier (talk) 08:37, 24 July 2015 (UTC)

Hi Seattle Skier. Thank you for this extensive explanation. I will need to ponder over it for a while to let the implications sink in, particularly in the light of the remarks about the apparent motion of distant stars as seen from the rotating earth in the "Distant stars" section in the Coriolis effect article, which seems to suggest that any motion (which I would imagine would include objects with an apparent velocity of zero) observed from a rotating frame of reference can be referred to as a "Coriolis effect". (No reference is provided in that section, so I cannot check whether astronomers are comfortable with the term or not, and what they would apply it to, if the term is used by them.)  Cruithne9 (talk) 13:04, 24 July 2015 (UTC)

PS. I don't want this to sound as if I am arguing with you. I'm looking for information and enlightenment. So I hope you will bear with me here. As you say above, the Coriolis force is an entirely fictitious "force", as is the Centrifugal "force". Both effects can be explained in terms of simple geometry and physics. I therefore struggle with the dismissal of one fictitious force (the Coriolis effect) in favor of another fictitious force (the centrifugal force) to explaining the apparent behavior of a geostationary satellite. These comments probably sound ridiculous to you, but I would desperately like to know what types of motion viewed from a rotating frame of reference can and cannot be termed "Coriolis" effects. Cruithne9 (talk) 14:04, 24 July 2015 (UTC)

PPS. I think I may have discovered why we seem to be talking at cross purposes. When an object moves over the earth's surface (and is partially or wholly detached from that surface) it seems to follow a curved path. For someone observing that curved motion, and is unaware that the earth is rotating, it would seem as if the object is subject to a sideways force causing it to deviate from traveling in a straight line. One can calculate the force that would account for this motion, and call it a "Coriolis Force". But it is an entirely fictitious force. The formula you use applies to this situation, which a special case of the Coriolis effect. When a straight-line motion across the solar system is viewed from our orbiting perspective, the path would also appear curved. The formula needed to calculate the "force" that might be responsible for that would be different from the one you present above. Things become mathematically horrendously difficult if the "real" motion is circular or elliptical round the sun. But that does not mean that the distorted motion as viewed from the orbiting earth is not an instance of the Coriolis "effect".

3753 Cruithne's bean shaped orbit in the vicinity of the earth is not due to Coriolis Forces (or, let's say, it would be foolishness to calculate them, as they would be unique to Cruithne, and applicable nowhere else in the universe). But that does not mean that its motion as seen from earth is not an instance of the Coriolis Effect. I hope this makes sense. Cruithne9 (talk) 20:34, 24 July 2015 (UTC)


 * Cruithne9, I will try my best to patiently re-explain things, as I've done this sort of thing many times in the past with students (I don't currently teach physics, but had to do so often in the past during several years of graduate work prior to my PhD and then several years working as research faculty after that). I apologize in advance if my comments seem snippy or curt, that is not my intent, but it is hard to convey tone properly in online writing. However, a real problem here is that you're just making up a lot of things out of thin air to fit your pre-existing beliefs, things which are not true, and some of this may be due to failing to read various statements carefully. Please be willing to read carefully and learn, while not clinging to your pre-existing beliefs about this subject. From your statements above:
 * "As you say above, the Coriolis force is an entirely fictitious "force", as is the Centrifugal "force"." I never said this in what I've written to you, you're putting words in my mouth. See above, I say "without any reference to Coriolis effects or to any fictitious forces at all", I do not ever say that the Coriolis force is an entirely fictitious force. The use of that term "fictitious" leads to a lot of needless trouble, perhaps it's best to call them pseudo forces or inertial forces instead, as they are very real effects in the rotating frame.
 * "Both effects can be explained in terms of simple geometry and physics." Not true at all, where did you get this idea? Simple geometry cannot explain or derive either the Coriolis or centrifugal force, you must use physics in a rotating frame to derive them. But as I stated, simple geometry CAN easily explain the apparent retrograde motion of the planets and the motion of 3753 Cruithne, without needing any physics. This is the most fundamental issue that you are having, by failing to understand this key point. You're trying to turn problems which need only simple geometry into physics problems, when they are not.
 * "I therefore struggle with the dismissal of one fictitious force (the Coriolis effect) in favor of another fictitious force (the centrifugal force) to explaining the apparent behavior of a geostationary satellite." As the equations show, the Coriolis force is dismissed in this case because it is ZERO. The centrifugal force is not dismissed because it is non-zero. That is it. There is nothing to struggle with. The Coriolis force turns out to be zero in this case, so it is not relevant to the behavior of a geostationary satellite.
 * "but I would desperately like to know what types of motion viewed from a rotating frame of reference can and cannot be termed "Coriolis" effects." The only types of motion are those for which the Coriolis force $$\boldsymbol{ F}_C = -2 \, m \, \boldsymbol{\Omega \times v}$$ is nonzero. Anything else does not involve Coriolis effects. And anything which can be explained using simple geometry (not requiring physics) is definitely not an example of the Coriolis effect either. These are the 2 key points for clearing up this misunderstanding.
 * "remarks about the apparent motion of distant stars as seen from the rotating earth in the "Distant stars" section in the Coriolis effect article, which seems to suggest that any motion (which I would imagine would include objects with an apparent velocity of zero) observed from a rotating frame of reference can be referred to as a "Coriolis effect"." Where did you get that idea from reading that section? Does it state that ANY motion observed from a rotating frame of reference can be referred to as a "Coriolis effect"? No, it does not say that. That section (which is somewhat confusing, totally unreferenced, and probably worthy of deletion) is entirely about the spinning motion of stars around the poles (see the circumpolar star article for more info on this). And as the equations in that section show, by the 3rd line the Coriolis term completely vanishes and the total $$\boldsymbol{ F}_f = m \, \boldsymbol{\Omega \times (\Omega \times r)}$$, which is only a centrifugal (centripetal) force with no Coriolis component remaining (there is no $$\boldsymbol{\Omega \times v}$$ term left). Therefore there is no Coriolis effect in the simple circumpolar rotational motion of the stars. The last line of that section says exactly as much ("therefore recognizable as the centripetal force that will keep the star in a circular movement around that axis"). Since there is no Coriolis effect in that motion, that section really does not belong in that article, and I may delete it after further thought on the matter.
 * "3753 Cruithne's bean shaped orbit in the vicinity of the earth is not due to Coriolis Forces . . . But that does not mean that its motion as seen from earth is not an instance of the Coriolis Effect" Your first statement is true, the second one is false. The first statement implies that it is NOT an instance of the Coriolis effect. The bean-shaped motion relative to the Earth is derivable from simple geometry alone without needing any physics or Coriolis or whatever, and the animated image File:Horseshoe_orbit_of_Cruithne_from_the_perspective_of_Earth.gif demonstrates this derivation nicely. Please don't go looking to desperately call it a Coriolis effect, when it's just a simple geometric effect caused by the relative orbits of Earth and 3753 Cruithne around the Sun. --Seattle Skier (talk) 05:15, 25 July 2015 (UTC)

More on the Coriolis effect
Hi Seattle Skier. Very many thanks for the time and trouble you have taken to extensively respond to my concerns and misconceptions. I entirely agree that I got the bullet shot vertically upwards wrong. I should have realized that it would indeed come back down straight into the barrel of the gun from which it was fired, whatever part of the earth it was launched from. It was 3 a.m. in the morning when this idea occurred to me. My apologies. Though the bent trajectories bullets follow upwards and downwards are fascinating examples of the effects of the rotating earth.

Although I have no idea of how much of this discussion should be continued on the Talk pages of Wikipedia, because, much of this discussion could be resolved very quickly and efficiently through a face-to-face interaction, and then posted on this page in a few sentences, I feel I have to respond to some of the comments you have made.

Firstly, all of the texts explaining the Coriolis effect, including the Wikipedia article on the subject, start with the example of a rotating turntable or carousel, across which a pencil line drawn with a ruler (by a person outside the turntable|) or balls tossed from the carousel either by a person on the carousel or by a person outside the carousel seem to follow curved trajectories when viewed by the person on the carousel.

Consider a rotating carousel (or merry-go-round), which, seen from above, is rotating clockwise. We will call the person on the carousel the “rotating” person, and the one on the ground outside the carousel as the “stationary” person. Any ball thrown across the carousel by either person follows a straight line as seen by the stationary person. But the rotating person will always see a curved trajectory. From the rotating person’s point of view it therefore seems that there is a force that acts (horizontally) perpendicularly to the ball’s motion to cause it to deviate from the Newtonian straight-line motion. This in not a real force, but an artifact of the observation relative to a non-linear rotating reference frame. (This is a direct quote form a Physics text book. The Wikipedia article on the Coriolis effect calls it a fictitious force, as do several other sources at my disposal). The entire effect can best be explained in terms of simple geometry, which, in your terms, if I understand you correctly, means that it is NOT an instance of the Coriolis Effect.

Where a “real” force comes into play (and cannot be explained in terms of simple geometry) is if the rotating person tries to move from point A to point B on the rotating carousel. If point A is close to the center of the carousel, and point B is near the periphery, then, if this person sets out in what he imagines is the shortest distance between the two points, he ends up to the left of his target. In order to reach point B he has to exert a sideways acting force to move him more and more to the right as he moves outwards towards B. On the carousel he will have traced a straight line trajectory, but according to the stationary person on the ground outside the carousel he will have moved along a curved path which can only have been caused by a sideways force. This force (or acceleration) is indeed real, because it required the expenditure of energy from both the rotating and stationary observers’ points of view. Is this the only instance of the Coriolis effect you would recognize as such?

If the turntable and carousel examples provided in all the introductions to the texts on the Coriolis effect are genuine, prototypical instances of the Coriolis effect then, by extension, any Newtonian motion beyond the carousel, viewed by the rotating individual, will also subject to Coriolis effects. Thus a ball thrown away from, or beyond, the carousel’s rim will also follow a curved as seen from the carousel. Indeed if it stays in the air for several turns of the carousel it will appear to follow an outwardly spiraling trajectory. In all cases the motion can be explained in terms of simple geometry from the point of view of the stationary observer. But if Newtonian motion across the carousel is correctly described as Coriolisean by the rotating observer, then the motion beyond the carousel must also be due to the Coriolis effect. It then ineluctably follows that motion observed from our orbiting earth of the planets and other objects in the solar system are also affected by the Coriolis effect. The fact that the complicated motions observed from earth are best resolved by translating them into the motions that would be seen by an individual in a stationary position in relation to the sun does not negate the fact that from the earth these motions are due to Coriolis effects, even though the stationary observer would ascribe them to simple geometry. The Coriolis effect does not exist for a stationary observer. But they are very real for an earth-bound observer unaware that he is on a huge 3 x 108 km diameter carousel centered on the sun.

I know that you have said above that this nonsense, but you have not explained why it is nonsense, nor given any examples of when and how the Coriolis effect applies. For instance, are you suggesting that the turntable and carousel examples used in all the texts explaining the Coriolis effect are simply “lies to children” (to quote Terry Pratchett)? What would your interpretation of these examples be? In the “Visualization of the Coriolis effect” section of the Coriolis effect article in Wikipedia a puck of dry ice is slid across a bowl of spinning water. This puck follows an elliptic track (as seen by a stationary observer) across the parabolically curved surface of the rotating water in the bowl, although it bounces back and forth off the rim of the bowl. The Coriolis motion as recorded by a camera mounted on the rim of the rotating bowl is uncannily reminiscent of the orbit of Cruithne as seen from earth. Cruithne9 (talk) 12:42, 30 July 2015 (UTC)


 * This reply addresses both what you've written above, and your August 4 post on my talk page. Please understand that this will be my final comment on this topic, as I definitely don't have the time to continue this discussion any further. Sorry about closing it off, but you seem quite stubborn about this subject, which is frustrating for me and not enjoyable to deal with, and in some cases you also try to extend the scope of my comments too far beyond what I've actually written. I realize by now that whatever I say is unlikely to shift your views closer to the limits of what professional physicists consider to be Coriolis effects (versus the vast broad overextension that you prefer where Coriolis effects are seen everywhere in all situations that could be viewed in a rotating frame). So we'll just be going in circles here (!) if we continue this.


 * Key points to remember to unravel and understand the Coriolis effect:
 * Only the most simple (trivial) examples used to demonstrate the Coriolis effect can be solved using simple geometry. In general, to solve any problem, physicists prefer to use the most simple description / method / frame of reference which gives a valid solution, so if you can solve a problem with simple geometry or by physics in the stationary frame, then great, do it that way, and don't bother using the rotating frame or Coriolis. You're confusing trivial demos which can be used to demonstrate what the Coriolis effect is (some of the simplest cases from the turntable / carousel demos) with problems which actually require using Coriolis effects in a rotating frame for their solution. The simple demos are great for an educational purpose, because they can be solved in both the stationary frame and the rotating frame.
 * Real non-trivial examples of the Coriolis effect can NOT be solved by simple geometry, nor can they be solved in the stationary frame. It is simply not practical or possible to solve for the motion of the winds in the atmosphere, long distance artillery shells, Foucault pendulum, or various other classic real-world examples, using simple geometry or the stationary frame. These problems can only be handled in the Earth's rotating frame, leading to Coriolis effects. These are the cases that professional physicists would normally refer to as examples of Coriolis effects.


 * Returning to the original issue at hand here: in order to include anything in Wikipedia, it must be verifiable in reliable sources. There are no reliable sources which state that 3753 Cruithne's motion as observed from Earth is an instance of the Coriolis effect (nor the motion of any other astronomical bodies), and so it can not state that in the article. Thanks. --Seattle Skier (talk) 18:14, 4 August 2015 (UTC)

Thank you very much. That makes a lot of sense, and clears up all my concerns. I'm very grateful. Cruithne9 (talk) 05:29, 5 August 2015 (UTC)

Note:
 * This entire discussion has been reproduced on the Coriolis Effect Talk page, where it belongs, and where this very topic is being debated at present. Cruithne9 (talk) 09:41, 26 August 2015 (UTC)

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 * ✅. Cruithne9 (talk) 06:59, 25 February 2016 (UTC)

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A barnstar for you!

 * Hi Thank you very much. Cruithne9 (talk) 14:52, 24 February 2016 (UTC)

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 * ✅.Cruithne9 (talk) 13:08, 3 June 2016 (UTC)

Gas exchange
Thanks for your contributions to the gas exchange article. One of my students also edited it as part of an educational project. I was not blown away with the results, and have spent some time trying to get their contributions into a better shape, but I'm pretty much done now. The material on counter/concurrent flow in the physical principles section could do with expanding - in particular, if crosscurrent flow is sufficiently distinct, it would be useful to add something there (and to the diagram?) too - you seem much more familiar with that topic than I am. One small thing: phylogenetically birds are reptiles (as the bird article states), because the 'Reptilia' are paraphyletic w.r.t. the birds (and arguably w.r.t. the mammals too, depending on whether you avoid the term mammal-like reptile). The common use of the word is at odds with modern biological classification; although there's the same issue with 'fish' and 'invertebrate' too, so *eh* polypompholyx (talk) 11:43, 24 April 2017 (UTC)


 * Hi Polypompholyx. Thank you for the compliments. When I changed the "Reptiles (including birds)" to "Reptiles and birds" I was tempted to make allowance for the fact that the birds are living dinosaurs, and therefore reptiles. But I could not think of a succinct way of acknowledging that without getting wound up in an unnecessarily complicated phylogenetic discussion which would detract from the "Gas Exchange" topic of the article. I eventually opted for the rather simplistic distinction between reptiles, birds and mammals, as they all use different gas exchanger techniques.


 * I will work on a diagram of a cross-current exchanger. But have to admit that I find it a very strange way of doing things - I have not come across any engineering application of a cross-current exchanger to reveal its interesting potentials. My guess is that the dinosaurs almost certainly had lungs like those of modern birds, and managed very well with them. I have added a sentence which explains the end-result of a cross-current respiratory gas exchanger, but I am not convinced that this could not be achieved by much simpler and more versatile techniques. But then we don't live in a Panglossian biological world! Cruithne9 (talk) 13:52, 24 April 2017 (UTC)


 * Living things are such a kludge of compromised 'design' decisions, you sometime wonder how any of them survive at all :) polypompholyx (talk) 08:46, 25 April 2017 (UTC)
 * Breed faster than they die off will do it. Efficiency and elegance optional extras. Good argument against intelligent design. Cheers, &bull; &bull; &bull; Peter (Southwood) (talk): 19:01, 2 June 2017 (UTC)

Lung
Hi Cruithne9 re your edits to the lung page - it seems to me that the additions are too lengthy - the article was passed as a GA - the sections on breathing are given undue weight imo - the section does have a main article hatnote. Best --Iztwoz (talk) 18:20, 30 April 2017 (UTC)


 * Hi Iztwoz. Thank you for commenting on my recent edits on the lung page. I made those edits because I thought that the balance between structure and function was skewed in favor of Structure. But on re-examining my edits there was a substantial section that was not strictly about the lung as such. That has been deleted, improving the subsection substantially. Thanks Cruithne9 (talk) 05:31, 1 May 2017 (UTC)

Internationally accepted notation for partial pressures
Hi Cruithne9, You mention an internationally accepted scientific notation for partial pressure in your recent edit summary at Respiratory system. Do you have a link to a reference for this? Cheers, &bull; &bull; &bull; Peter (Southwood) (talk): 18:53, 2 June 2017 (UTC)

Hi Peter (Southwood). There is great variation in the notation used in the various Physiology textbooks. A very common form is pO2, but a lower case p such as this means "the negative logarithm of the molar oxygen concentration” as in "pH" and “pKa” for the negative logarithm of an acid’s dissociation constant. This is clearly completely inappropriate and misleading when referring to the partial pressure of a gas; but like many of the other incorrect notations is simply copied from textbook to textbook without thinking. Others use PO2, or simply PO2 or P(O2). These are improvements on the pO2 theme, but although still strictly speaking incorrect, are one's only option when using MS Word, or other text editing computer program. But note that PO2 suggests a chemical formula, denoting an oxide of phosphorus! The correct notation is $P_{O_{2}}|undefined$ as indicated in . This is the notation used in the article on the Henderson-Hasselbalch equation and the article on Partial pressure, and probably elsewhere in Wikipedia where the authors have written chemistry and physics articles, making sure they use the internationally correct notation. The ppO2  used in Respiratory system article (which was actually originally entered as ppO2, but changed by me to ppO2) is an extremely rarely used notation, which the editor who changed all the $P_{O_{2}}|undefined$s into this format deemed “simpler”, though many readers of the article, if they do not notice "pp" definition in the “Control” subsection of the article are likely find confusing. Cruithne9 (talk) 08:15, 3 June 2017 (UTC)
 * Thanks Cruithne9, most obliging. I generally use the ppO2 notation in diving related articles and this is one of the notations I often find in the industry literature. It is simpler to code, but I don't see that it is any different in simplicity to read. I have also seen PO 2 used, which I assume is a kludge for the option. ppO2 is simply wrong, even ppO2 is better Cheers, &bull; &bull; &bull; Peter (Southwood) (talk): 08:34, 3 June 2017 (UTC)
 * You may be interested in the discussion at Wikipedia talk:Manual of Style Cheers, &bull; &bull; &bull; Peter (Southwood) (talk): 12:15, 18 June 2017 (UTC)
 * Thanks that makes interesting reading. (I think that whatever symbol is used, it should be defined when it is first used.) Cheers Cruithne9 (talk) 15:02, 18 June 2017 (UTC)

Comments on Respiratory System
I really appreciate your editing to respiratory articles, and I understand it can be frustrating to deal with other editors, particularly if there is a perceived or actual inaccuracy. However please refrain from making personal attacks as you have done here: "arbitrary, senseless ramblings of someone who seems not to have any knowledge of respiratory physiology, anatomy, zoology or physics. If this willful nonsensical editing..." (WP:NPA)

We are all here, devoting a lot of a time and effort, to contribute to this encyclopaedia. Some of us have subject expertise, that is great as accuracy is very important. Some of us have other focuses - forming a coherent and easily understandable encyclopaedia is almost just as important. But we should at least try and treat each other with respect even when frustrated.

Please understand this editor is, like you, trying to help communicate knowledge to readers, and is a human somewhere on this planet who has devoted a fair amount of time and effort to improving things around here (even if like most of us they make errors occasionally), just as you have. Tom (LT) (talk) 12:54, 24 July 2017 (UTC)