studiot

It's a right question. I think because theoretical physicists uses only math, and do not consider the phylosophic problems of particles. They adopt, by default, particles in the absolutely empty space (Nothing), which is impossible condition. Thank you for your reply. But you didn't say what you think a particle is. So please tell us since that is crucial to your proposal. One further question, how does your model describe shadows ? What are they made of ?

In all honesty most of the would be Pi is something else brigade have actually latched on to some obscure (real or imagined) effect which has Pi in its definining expression. They then treat this as the definition of Pi, rather than the other way round, and claim all other uses are secondary or flawed. Again rather than introduce a new constant or parameter for their purpose. So I prefer to wait and see what mike has to say when he can add to (improve) his posting.

I see you are also a maths wannabe But of course there are units in maths - it is how we distinguish between length, area and volume and how they are handled, for instance. How about this famous identity ? [math]{e^{\pi i}} = - 1[/math]

Before I bother to look, someone please tell me that this is not another one of those golden ratio cranks. They can hangout 20 pages of drivel without blinking an eyelid.

No you got that one wrong. It would be reasonable to request a discussion to help you clarify. Since you like arguing with your teachers I hesitate to say this but they are one of the most useful factors in your education. This is because they provide something that cannot properly be provided any other way. Good teachers provide marked work. That is they go through the reasons why and why not. Further you say that this was an internal test. Again a good sign lost in the West with too much management of 'education'. The point is that you learn more from your mistakes than getting something right. So doing things, getting it wrong and finding out why is part of learning. But you need to get them wrong with no penalty, hence the internal test. But you have also told us that you are not interested in Science in the long run or in academic progress. Setting this aside, a quick run through of the issue. Reactions can be classified in many different ways, depending upon the point of interest. Sometimes several different categorisations apply as with combustion and oxidation. Howevver not all combustions involve combination with oxygen. Also not all oxidations involve oxygen at at. Combination with oxygen is the most elementary definition and a starting point. What definition do you have ? I fully expect the test was to see if you know and understand the 'core lisr' you posted. So I am glad to see that you were actually thinking about it. A good trick to master for exams and tests is to be able to pick out the answer the examiner is looking for if there is more than one possible.

First Where did the figure of 38% come from ? You need to provide references for this. Second I agree with the point that if you were unwell enough to need the surgery, how would you fare in the ascent from Earth in the first place ? However Both NASA and my local sports medicine clinic disagree with Ken's bald statement about worse outcomes. Do you have evidence for this Ken ? I don't wish to advertise but my only reference for this comes from their information so I have clipped it. I have never needed this treatment, but their other NASA piece of kit (photobiomodulation) certainly helped with my osteo arthritis condition.

It is not clear to me. A plane is of genus 0. Which means we can shrink any circle on the surface to zero ie a point. Which is what the OP asked us to do. But that does not imply that any 'packing arrangment' of such points will fill the plane, you have to use the right one. But no you cannot Tesselate a plane with finite circles.

How will writing letters to a Republican Congress (or even a Democrat one if ever) make any difference ? There are quite a few well established drugs and treatments that the manufacturers have declined or ceased to make simply because it is not profitable enough.

Well I grew up a little bit before that. In those days I really enjoyed Traveller's Tales and hans and Lotti Haas - both in black and white. We did have some full colour but it was cinefilm, made by Unilever on the subjects of Physics and Chemsitry. They were really good and came with some full colour magazines to back them up. I still have these. Most of the lectures I gave at conferences and the like were on prepared slides, I only ever remember one definite ppoint, entitled 'Cracks', which I gave at the Concrete Society. You should also acknowledge that much learning used to go on in industrial labs up and down the country. Sadly many of these have disappeared and the rest are a pale shadow of their former selves.

Some more links An interesting american discussion site about the subject https://permies.com/t/208521/tech/Venturi-effect-air-flow-buildings A technical paper on Hawa Mahal https://www.irjet.net/archives/V9/i3/IRJET-V9I3386.pdf

That's the whole point, there are no gaps in the real number line.

Architecturally this is called passive cooling. Here are some links. https://en.wikipedia.org/wiki/Passive_cooling How India's lattice buildings co...How India's lattice buildings cool without air conFor centuries, India’s architecture featured intricate lattice structures. Now, as modern architects search for better ways to keep buildings cool, it’s making a comeback.

The point is that polar coordinates will completely fill the plane or 3D space with the radius at infinity. David's problem is that he has used a boundary - the circle he wishes to fill. So you need to be able to describe that boundary in polar coordinates to use the method and further since he is filling a disk, the outer circle radius is constant. That means we can start with a single line of that radius and sweep it around one end in infinitesimal steps, remembering that a line has no width. As the radius sweeps around and angle of delta theta it covers all points in a sector bounded by the infinitesimal arc of the out circle. Summing all these goes to an integral as delta theta goes to zero.

It can be done if you rearrange your dots. The trick is to use polar coordinates not cartesian ones and arrange you dots (which in the limit have zero diameter) in radial lines and then consider the angle between each line, taking the limit as that angle tends to zero. You might also find the six circles and seven circles theorems interesting, along with Steiner chains. (they do not fill all the circle.) You may like to know that the radial method is part of the mathematics of s orbitals in quantum mechanics.

Despite the social media hype the presneter, Ella Al-Shamahi, is not Lara Croft2. She actually makes some very subtle points and questions. It is also true that some of her explanations have alternatives, but the story she tells does hang together in the large. Now that there have been 2 episodes that weave in lots of modern scientific analysis techniques, without baby explanations of radiological and other dating methods. Actually the dataing method I found most interesting were the growth 'rings' in teeth, not one I had heard of. Also interesting is the paleoclimatology evoked to explain why H Sap moved out of Africa and into Saudi and thence through S Asia to Indonesia and on to Australia. But yes the episodes are overlong because of the money wasted on CGI and dramatic music and repetition of clips where something useful was said or shown. Unfortunately that tendency is increasing and common to many programs these days. However you are under no obligation to watch it or expose yourself to the danger that you might learn something.

Not sure where to place this but anyway is anyone else watching the New BBC series about the evolution of Homo Sapiens. There are 5 separate 1 hour programmes in the series, of which the first has already been shown on BBC2. The presenter is a paleoanthropologist and interestingly a woman. I say interestingly not in a disparaging way but because there is a noticeably softer approach from previous 'hard sicence' programmes with male presenters. This programme is also bang up to date with much new material and hypotheses about the evolution of our species. As such it may well be of interest to all those who have been arguing about this subject recently.

Interesting. thanks. +1

The various terms associated with 'eigen' come from the German and are attributed to Hilbert. They are mathematical terms concerning linear mathematics so we have eigenspace, eigenfunction, eigenvalue, eigenvector and eigenstate. The german word eigen means 'proper' and can be used for several puroposes in linear mathematics depending upon what they are applied to. These words have pure mathematics meanings realted to the solution of equations, but also have specific physical meanings when applied to physical systems. The physical systems may be 'classical' or 'quantum' mechanics or even statistical. The first two replies here give some examples from classical and quantum physics. https://math.stackexchange.com/questions/26662/eigenvalues-and-eigenvectors-in-physics In pasing I note a sprinkling of downvotes, which I see no reason for and only serve to discourage someone who is 'doing their best'.

Diagrams can be very useful and informative. Do you mean portrayals of real world things like an internal combustion engines and abstract concepts like the carbon cycle or the hydrological cycle ? videos have their uses but still graphics can be studied more easily. I myself post a lot of sketches compared to some.

Depends what you mean by visuals. And also why you are 'adding' them.

Why is everyone so hung up on 'particles' these days, without any proper understanding of what they mean ?

Glad to hear it. +1 The moral of this is that you can't be expected to know all the tricks at once or without a lot of practice, so if you need help ask a question about what you wish to achieve.

First a question. How old is the child or are the children you have in mind ? There is no general answer to this question, every child is different with different needs and these needs change as the child grows eventually to approach adulthood. So for instance some forcing is necessary. This is the reason mothers (and hopefully fathers) hold their your child's hand tightly, when waiting at the roadside to cross. The younger the child is the more likely it is to be suddenly distracted. Sometimes this does not matter, but no one want their child run over. Parents should also offer a chance to try out all sorts of different activities and passtimes and be prepared for any given child to like some and dislike others. So you buy say some roller skates for birthday or christmas, and they are used a few times then forgotten. Do they like dolls or dogs ? Swimming or reading ? and so on. You can reinforce the likes and quietly drop at least some of the dislikes. But is is also necessary to discourage antisocial or other desireable behaviour, especially watch out for cliques that try to override adult guidance. Hope this is helpful.

Not sure I understand any of this but I do agree there are too many distractions in some modern cars. FYI the incident with the fire engine occurred in 1968 or 69 as I was walking my dog.

Considering the nature of the spam, I was wondering if it was not directed at SF at all. I wondered if it was simply to increase the mentions of certain organisations referred to and thereby increase the web footprint of those organisations. Somebody paid those spammers.