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Everything posted by studiot

  1. 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)
  2. 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
  3. Hey folks it after christmas/newyear so I've gotta give this refreshing bit of 2024 sanity a thumbs up. +1
  4. Anything like this ? can you catch a screenshot of your own ?
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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 ?
  11. 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.
  12. 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.
  13. Do you understand the difference between a vector and a scalar ? You haven't responded to my statement about this.
  14. Exactly. Personally I am uncomfortable with the idea that the stated grease is 10% 'silica' , an known carcinogen.
  15. I've not seen that analogy before, +1
  16. I'm sorry, this is not a proper discussion. I am reading what you say, and addressing your points, a few of which I agree with a few I disagree with and some are just plain wrong by observation. You are simply writing longer and longer versions of the false assumptions without answering my questions about observations on reality. Another plain wrong statement would be If this is an answer to my comment about circuit theory then it is just plain wrong. The sign convention for charge (and current) is opposite to that of voltage (potential). Please answer the questions I have asked instead of ploughing on as if they had not been asked.
  17. How is this any sort of answer to my points? In fact all you have done is reiterated my point about the difference between charge and current. A further question, to emphasis the point raised by swansont. Every day, throughout the universe, electrons are taking part in chemical reactions, many of which give of photons. Those atoms concerned along with their electrons, will go on to take part in more chemical reactions up to an enormous number. If each time this happens how come the charge on the electron does not diminish by the charges you claim now reside in the electric fied of the photons ? In other words how come the charge on all electrons is not decaying over time in the whole universe ? Or do you not accept the principle of conservation of charge ?
  18. Not in the case of an EM field it doesn't. An electron in an atom can emit a photon in the ionisation process and then be destroyed by a subsequent nulcear reaction. Yet the photon will remain forever or until it is absorbed somewhere else, which ever comes sooner. What about answers to my questions ?
  19. A very disappointing response to my polite and pertinent question. I have another pertinent observation/question. The assignation/term positive or negative refer to different properties for charge and electric fields. This is reflected in the fact, often missed, that in electric circuit theory (where we have current not charge) there are two (not one) sign conventions in play. As a mechanical engineer you should have a good understanding of sign conventions and their implications. Charge is a scalar. the electric field is constructed from vectors and the sign convention lies in the vector in the latter and the scalar in the former.
  20. External intervention, deliberate or otherwise.
  21. Two things about bots. This piece of business news Apparantly NYT allege that ChatGPT was trained on many writings that are their copyright and is now regurgitating them, without permission. and my own recent experience with Google. I have noticed that when googling a question especially a technical calculation, the top reference is sometimes to a ChatGPT reply and this gradually getting more frequent. I will post a screeshot next time I get an example
  22. I am sorry to rain on your parade, but such theory already exists (and has done since Newton's forward and backward difference formulae) Iterative methods are also called recursive methods in Analysis and Calculus and come in two flavours : Linear and Non linear recursion. There are also iterated integrals (Fubinis Theorem) and iterated series.
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