studiot

Here are two quotes from the book I recently mentioned in the book talk section that aptly illustrate how readily Frank Close gets to the nub if the matter.

Oh! You may be about half right. Unfortunately this includes some serious misconceptions which could lead you far astray if this not not a one off. What a pity you didn't want to discuss the problem from start to finish. A good place to start would be to answer the one simple question I asked, or ask for more information about it.

Forgive me for knowing what i am talking about. You posted Applied Mathematics in the Analysis and Calculus subforum where it is certainly misplaced, but i thought it a small point, easily rectifyable. Perhaps @swansont would be kind enough to move it to Applied Maths where it truly belongs. So what is the triangle if it is not part of the physical world? This is just incorrectly imagined nonsense, as written above. It certainly has little or nothing to do with the 'triangle of forces'

Thank you for your reply. I am still not clear what is going on here and therefore what your actual question is. Can you (scan/photograph) and post the passage from the book as printed please. You need to be aware that there are (always) two triangles involved. There is the real world-object triangle which defines the geometry of the situation, both in terms of distances / positions and angles. And there is a purely theoretical abstact triangle others have referred to as a vector triangle. This second triangle is similar to, but not congruent with, the real world triangle. Two triangles are said to be 'similar' if they have the same angles, but not generally the same side lengths. Triangles which have both the same angles and the side lengths are said to be congruent. I am guessing that mixing up these two different triangles is the source of your difficulty, but I can't be sure without sight of the original.

Some Professors are noted for the wide understanding of their subject and how it all fits together and combine this with the ability to present an understandable and coherent picture. This ability picks out important insights. Firstly the 2022 book 'Elusive' by Frank Close, Professor of theoretical physics at London University offers a remarkably clear account of 'Higgs Theory' and its connection to Quantum Theory, Relativity, and particle physics, in plain English in the body of the text and in Mathematics in the appendices. Secondly the 2012 book '17 Equations that changed the World', Professor of Applied Maths at Warwick University is equally worth reading, especially the penultimate chapter on the 'Black-Scholes Equation' , which should be read by anyone who thinks they know anything at all about Economics. A real eye opener. The two books have one mathematical caveat in common. 'Consider the conditions of applicability of this theory, before use!'

Yes I think you may be missing something. Is your triangle a real object like a triangular shelf bracket, say a length of strip metal bent into a triangular shape ?

My apologies make that 14 seconds of arc

OK this (payfor) tutor site works through a question from Kreysig Functional Analysis and its applications https://www.chegg.com/homework-help/questions-and-answers/kreyszig-introductory-functional-analysis-applications-chapter-5-applications-banach-fixed-q34808855#question-transcript At the moment my copy of Kreysig is buried, I should be able to retrieve it tomorrow but this is the picture I was looking for 912 × 996 I don't know what you maths background is or if you are seeking the underlying pure math or the (very widespread) applications ?

It doesn't 'explain the equation'. You supply an equation, the theorem applies in one way or another to all equations. I will look out a picture that makes this clearer. Can't seem to find the best one on big G.

If you ever return to discuss your proposal I take your point "So far I have heard replies suggesting that I try something else" To deal with this enquiry, please note that this is not a new method of demonstrating (and measuring) the curvature. The Romans knew about it, as did they about the difference between using a water level and a line of sight. So let us fast forward to modern times when this difference was not appreciated, causing major disruption to a giant construction project I havd direct experience of. Over your distance of 1 km the a level line is approximately 79mm below straight sight line. however sight lines, including lasers, are not perfectly straight and refraction causes the line to dip below the straight by about 12mm over 1 km This has the combined effect of reducing the difference between a level line and a sightline to about 67mm. Another way to look at it would be to note that you would have to depress your laser sight line by nearly 2 seconds of arc to align on the level spot 1km away If you have the interest we can discuss this further.

The theory of this is given by the Banach fixed point theorem otherwise known as the contraction mapping theorem. https://web.stanford.edu/class/math51h/contraction.pdf https://en.wikipedia.org/wiki/Banach_fixed-point_theorem This gives the range on input values for which the process will converge to the desired solution and the conditions for convergence. The trick with iterative solutions is to arrange or transform the equation into a form that converges over the desired range.

First I am going to say +1, for actually answering another member. First time that I can remember. Then I am going to say that light reflected off snow can lead to a conditions we call snow blindness. This is not permanent , means that your eye have been looking at a patternless reflection for too long. They will recover after closing them or looking away at something more normal for a while. Photokeratitis (Ultraviolet [UV] burn, Arc eye, Snow Blindness) - College of Optometrists (college-optometrists.org)

1) There is no difference. Groups are sets with a suitable associative binary operation. Some groups have additional structure, eg abelian groups, which have a commutativity requirement. Non commutativity is very important in QM and leads to the uncertainty principle. Try this postgrad book. 2) Hopf algebras also explot non commutativity. https://www.theoremoftheday.org/MathsStudyGroup/SeligHopf.pdf

Hey folks it after christmas/newyear so I've gotta give this refreshing bit of 2024 sanity a thumbs up. +1

Anything like this ? can you catch a screenshot of your own ?

How exactly does this address any of my principal points, rather than mocking my attempt as simple examples to help understand them, which you obviously don't. 1) There are several different types of evolutionary process. 2) Not all evolutionary processes involve selection. 3) Selection is itself a complicated process that involves criteria or standards to 'select' against. 4) Darwinian evolution involves what he dubbed Natural Selection, which was another word for the prevailing conditions. 5) For such a process to operate the prevailing conditions must remain sensibly constant for a long enough time. 6) The prevailing conditions can suddenly change (as with the dinosaurs) in the middle of such an evolutionary process.

Whilst I agree that selection and evolution can be connected I don't accept that this is always the case. They are separate distinct processes. Change over time is another thing again, which I think too large in scope. Usually the connection is that as small variation of an offspring of a member of a population leads to another slightly different member of that population. For example a smaller or larger elephant with a slightly longer or shorter trunk may have an evolutionary advantage, but is still an elephant. A dinosaur faced with the external event of the chixelub meteor underwent an entirely different change, although top of the then evolutionary tree.

Thanks. +1

We are all (well nearly all) learning things here. +1 Please note my comment about dialect and the pronunciation of the word bath. Also compare bath and bathilith.

So you are using this to preach that you know everything there is to know about these things instead of listening to see what others might know. ? I asked if you know the difference between a scalar and a vector to try to help you you understand what swnasont and I are both saying, but from different viewpoints. The positive and negative convention used in an electric field refers to the direction part of the electric field vector, it does not refer to the magnitude. Charge on the other hand does refer to the magnitude, since charge is a scalar and has no direction.

Would that not be artificial selection? I'm sorry I missed this reply. No it would not be artificial , nor would it be selection in the darwinian sense. I am suggestng the definition of the word evolution you are employing is too narrow to cover all possible/conceivable circumstances.

We all know that the Sun, the Earth, the Moon and the terrestrial waters are in motion. None is static. So static is the wrong word to use. We call what you mean by static theory the equilibrium theory and you are correct it was due to Newton, centuries ago. You are also correct that it is a very crude inadequate model, But is does correctly identify the forces involved as a combination of gravitational and rotational and that gravitational forces dominate the force part of the equation, but that rotational speeds dominate the timing part of the equation. A better theory, which also allows for the fact that the rotational axis of the Moon's orbit is not parallel to the Earth's own rotational axis and a few other effects is known as The dynamical theory of tides. But this is still based on Newton's force analysis. As I have shown your figure of 1600 km/hr is approcimately correct. But I have also shown that it does not correctly model the system as the timing of the moon's periodic function is not the same as the mechanical resonant frequencies of the water. Do you understand what this means ? The simplest method of approaching this is to model the hydrographic response as a fourier series rsonant with the lunar driving force, which introduces the humps you mention and use actual observations to calibrate the fourier coefficients to suit. A yet better mechanical model is to consider the lunar driving force as a 'Forcing Function' with a frequency near to the resonant to a non resonant system. Are you familiar with the maths of this ? It produces frequencies not in the oringinal lunar function nor the resonant response of the hydrographic system. So to echo swansont's words Why have you repeated your earlier posting ? What are you trying to achieve here ?

They used to add amyl meta cresol or hexachlorophene to toothpaste once upon a time, until it was banned. What is the form of this 'silica' it doesn't say. However I do take your point that it seems to be used in lots of other thing meant for ingestion.

It doesn't bother me, it was just an oddity that sometimes appears on my screen, like that business of the unidentified notification I reported and everyone tried to tell me was my doing until Capt'n sorted it out. I didn't think to get a screen capture last time it appeared, but I will do next time.

Do you understand the difference between a vector and a scalar ? You haven't responded to my statement about this.