Ian Brown
I am 78 and have a PhD In Mathematics and 53 years' experience teaching undergraduates maths but am ignorant of biology. Daughter did zoology at Reading! Fascinated by icosahedron structure in virus!
Location Surrey
Activity
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No I have not heard of flutter in this context and have no flying experience (in a cockpit) - ready to learn!
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Thanks Anne-Lise. It worked with the other link!
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Same -it only goes in short bursts.
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Ian Brown made a comment
Then on slide 20, I cannot see epsilon in the diagram. (I saw it somewhere before). Epsilons are usually very small! Is it usually negligible - or just hidden from my eyesight? Then, on slide 22, are the boxed equations vector or scalar? Is nXa a unit vector? If so, the right hand sides should be vectors, but I see no arrows.
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Ian Brown made a comment
On slide 6 of load factor pdf, I'm confused. It says vector P perpendicular to vector v. Shouldn't that be vector L perpendicular to v ?
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@Anne-LiseLuga Oh, no. I missed that answer page. Sorry, but encourging!
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Thank you, Stu Y. The expression 287 J kg^-1 K^-1 looks much more scientific and unambiguous. (I agree it is a pity we cannot write superscripts and subscripts here - as far as I know.)
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Ian Brown made a comment
I would have liked to have heard more explanation about r in the video.
I presume this is the constant of integration as in PV=RT.
In the formula P = (rho) r T
I feel I need to check the dimensions on both sides. As a mathematician who is very ignorant of physics I do not like r = 287J/kg/K
as it seems to need brackets. Is that 287 (JK)/kg or... -
I got aspect ratio lambda = 1.9 for the Mirage III using the interactive tool.
Is that any good?
Wasn't quite sure where to place the chord? -
Ian Brown made a comment
Hi everyone. I am retired after 53 years teaching mathematics to undergraduates. But I am quite ignorant of many technical and engineering matters. Now is the time to learn new things.
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Thanks for the reference. As you may imagine, I like 'fine tuning'. Re the beer, yes it is a pity you are more than a Boris walk away from me!
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@GarethWilliams No need to apologise. 'In normal times' I might not have been so prevocative. But I find that in other groups dedicated to other particular subjects, they are happy to include, at such a time as this, items that you might call 'trivia' or 'off subject' or even funny (to keep people's spirits up, especially if shutdown alone). Anyway, as I have...
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Ian Brown made a comment
* I meant to include this in my main comment below but I ran out of space.*
I was also pleased, as on any university course, to be helped in my learning not only by excellent staff but also by fellow students. In particular I would like to thank Gareth Williams who somehow had insights into what I found difficult and suggested many references for further...
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Ian Brown made a comment
Thank you to all the team for a great course. I was very impressed by the way educators answered any questions, promptly and personally. I did not understand everything but that was because my background was unusual. Unlike others who have written here, my mathematics was reasonably OK as I had taught it at undergraduate level for 53 years - even in the early...
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@GarethWilliams Once again, an interesting and helpful article, Gareth. (Symmetry Magazine)
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We are probably not allowed to raise 'faith' issues here but at the end we learn 'It turns out that the powerful equations that have been introduced in this course describe extremely well just 5% of the known Universe.' (lecture notes 6.6 p. 20). We have spent so long discovering so much (not just on this course but in the long history of science), yet we only...
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Indeed! I have been struggling a bit but this makes things clearer.
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@ChristosLeonidopoulos Thank you for these replies, Christos. I am getting rather behind but am slowly getting there; thanks for your help.
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Ian Brown replied to Peter Butlin
Thanks again: The Susskind lectures are another treasure trove for me to explore - just started. Also the 'Interesting article on the Higgs hierarchy problem' you suggested at the discussion at the end of last week's ( I am a week behind but at least you have kept me from giving...
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@BJohnson Thanks, this is very helpful list of references.
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Ian Brown replied to Peter Butlin
@GarethWilliams Thanks for this reference, Gareth. Once again you save the day when I am falling behind and thinking of giving up. This reference gives me what I needed. You have an amazing way of perceiving what other students need and pointing them in the right direction!
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Yes please.
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Thanks for accepting me into this group. More interesting and approachable stuff. I found Professor Ed Copeland and the new particle X17 interesing - even the possibilty of discovering another fundamental force (?).
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Thanks again, Gareth, you have an amazing store of links to supporting materials and an ability to encourage and find the level I am struggling with ... which is more like the introduction lecture of Tina's 'level down' lectures! I need to get all these particles sorted and understand the weak force more. I can see there is some good stuff here for which I am...
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WOW! Thank you for this link, Gareth. I have started to look at these and it seems just what I was looking for to stop me giving up on this course! Although Thomson goes on to things I do not understand, his approach gives me enlightenment on fundamentals I should have picked up by now!
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Thanks Marios, I have listened to this video again but it is around minute 2 that I begin to 'lose the plot' on this course. Perhaps I am too classical and macroscopic. I understand what the strong force is but where can I find a simpler explanation of the potential for the strong force? (Does the strong force not fall away rapidly with distance so how can...
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Alongside equation 1 in the lecture notes of video 4.3 we see the familar partial dv/dr showing force of order 1 / r^2 .
No corresponing remark is made for equation 2. Why is this? Presumably it would involve partial dr/dr = 1 in the first case and the derivative involving the exponential in the other. Am I right in looking for an analogous force... -
Ah! Just looked back at my 1964 textbook Rosser, An Introduction to the Theory of Relativity. He has (r, ict) for the 4-vector where r (should be underlined) is the position vector and, yes, i = sqrt(- 1). He includes the c to balance the dimensions. By the 1970s I was out of this area and have hardly followed it since, so now I have retired I have 50 years...
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Thanks for sharing. I found Wilczek's lecture helpful (with the historical approach) till I got out of my depth. By dipping into such things, I am making some progress!
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Ian Brown made a comment
Small technical point: the sub-titles (which are helpful) sometimes obscure what the lecturer is writing. Perhaps this can be done in a different way. However the material can be picked up afterwards from the lecture notes.
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Ian Brown made a comment
This is a helpful introduction as it highlights the important things which I still feel wobbly on, and indicates where we are going. In particular I need to be enlightened on 'strong' and 'weak' forces, the 'bestiary of observed particles'
( I am encouraged to read that - was it Fermi who said - 'if I could remember all those names, I'd have been a... -
Thank you, Gary.
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To quote from the link above
"Four vector xµ: time + spacial coordinates
to give them the same units, define x0=ct
x0 = ct, x1 = x, x2 = y, x3=z, β=v/c "(Can't type subscripts here but the mu, 0, 1, 2, 3. should be 'downstairs' as you put it.)
So time comes in conveniently in the first component of a 'four-vector'. (In my day it was the... -
I was not sure what you meant, Gareth, by upstairs downstairs so I Googled it and came across this link to someone's lecture notes which I found helpful and reminded me of what, I think, you are getting at: covariant and contravariant tensors....
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Thanks again, Gareth. Like the previous link, this presentation helped me learn more about the things I am ignorant on, with challenges to learn much more about sorting out units and dimensions! A great presentation.
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@GarethWilliams Thank you for these links Gareth. To answer your questions on my background, I know of Group theory but not enough to call it a 'joy'. Similarly I knew of Planck's constant but am not confident about it at all. My background is that I lectured to mathematics undergraduates for 53 years (yes, is that a record?) But for all that, I am getting...
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@CalumMilloy Thank you for your prompt reply. This is a great feature of this course that it is so well mentored like this with prompt replies!
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These links have been very helpful to me. About the right level to increase my understanding but giving the opportunity to go much, much further. I see why you said you have done this course several times! Thank you Gareth.
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@GarethWilliams Thank you for your reply. I have always been fascinated by absolute constants, especially dimensionless ones and the idea of the 'hand of God' on the Unverse!
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Thank you; that was helpful.
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Ian Brown made a comment
Where can we find a simple introduction to Feynman diagrams with perhaps an explanation of how many possibilities there are? (several thousand?) The lecture gave a figure, I believe, but I did not get how it was arrived at. We were shown just a few. Also can you point me (?back) to a diagram of each of the basic fundamental particles showing their mass and...
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Ian Brown made a comment
A difficult topic beginning to come a bit clearer. But the 'creation' process is harder. An electron and its 'anti' (the positron) collide and produce radiation. OK. But radiation splitting back into electron and positron is not so clear. How does that happen? There is nothing to hit?
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Ian Brown made a comment
I am finding it hard to navigate through the course website, what 'to do' next etc. (This is sometimes harder than the content!). Where to go next? For example I have finished "1.14", where do I go now if I do not want to pay money to upgrade?
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Ian Brown made a comment
Delightful presentation. I just thought perhaps the conclusion might have been more convincing if 'sine squared + cos squared = 1' was explained as a precise result based on Pythagoras (which was indeed mentioned) rather than relying on: it looks true from the diagram!
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Ian Brown made a comment
Can you explain the integrals shown please, and what are the units GeV?
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Today's noon surface pressure chart contains a purple line fragment without any triangles or semi-circles as well as several black curved lines (troughs) which I asked about before. Are they all remains of declining occluded fronts?
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Ian Brown made a comment
Thanks for another good week. Outstanding question from before: I would like, please, to know more about "the thick black lines ... called troughs" on the charts. They are not "fronts". not centres of low pressure at ground level so what are they? I believe they represent turbulent air aloft that may cause showers, but how did they get there? Are they left...
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Are they the same as, or related to, 'TROWALS'?
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Ian Brown made a comment
I would like, please, to know more about "the thick black lines ... called troughs" on the charts. They are not "fronts" not centres of low pressure at ground level so what are they? I believe they represent turbulent air aloft that may cause showers, but how did they get there? Are they left overs from occluded fronts?
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@SylviaKnight That's a very useful link. Thanks. So is that two occluded fronts crossing SE England today? The weather seems to have been unusually quickly-changing recently!
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Ian Brown replied to Michael de Podesta
So "two contrasting air mass(es) meet, leading to ascending air". The Coriolis effect then deviates that air to the right causing a "westerly-flowing ribbon of air" (meaning - rather circuitously - towards the east, FROM the west)? Am I right? I am a bit muddled on cause and effect here. Do the rotating cells generate the jet streams? Or is it pressure...
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Ian Brown made a comment
I enjoyed week 1. I have recently retired after 53 years teaching undergraduates mathematics so I am OK on Coriolis but quite ignorant on meteorology generally. Joined RHS at Wisley yesterday (I see we have a tutor from there!). Forecast said it would start to rain at 3 p.m. Got totally soaked in an earlier cold sharp shower after lunch! There was I, trying...