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Jan 27, 2020
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"If I had to write this paper, this is what I would write."
2.1.1. Kinematical définition. If I had to propose a definition of the energy associated with a Dirac particle, I would say first that such a definition implies a) the mathematical knowledge of the Minkowski spacetime M = R1,3, b) the physical notions (which are not pecular to Quantum Mechanics) of the local energy and momentum-energy of a system. Then I would continue to suggest: We will define a Dirac particle as being an oriented plane P(x) of M, called the “spin plane”, passing through a point x of M. P(x) is orthogonal, at each point x in M, to an unit time-like vector v(x) of M, called the “velocity unit vector” of the particle. Furthermore, we will suppose that the plane P(x) satisfies the following
Feb 19, 2020
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John McCarthy 10/24/2011
Douglas Engelbart 7/2/2013
Marvin Minsky 1/24/2016
Wes Clark 2/22/2016
Seymour Papert 7/31/2016
Jay Forrester 11/16/2016
Bob Taylor 4/13/2017
Chuck Thacker 6/12/2017
Larry Roberts 12/26/2018
Fernando Corbató 7/12/2019
Larry Tesler 2/17/2020
Bert Sutherland 2/18/2020
Feb 19, 2020
That ARPA/IPTO funding in the 60s was some good shit.
Mar 17, 2020
@mgreeley Eames' "Mathematica" exhibit from 1961. There are three today, in Boston, Queens, and Detroit.
Jun 15, 2020
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@ivanhzhao @ccorcos It's striking (heartbreaking?) to compare the focus and concerns in the Obj-C HOPL paper to those in the Smalltalk one. Cox and Kay live on different planets. worrydream.com/EarlyHistoryOfSmalltalk
Sep 16, 2020
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Brillouin, 1942
CHAPTER IX MATRICES AND THE PROPAGATION OF WAVES ALONG AN ELECTRIC LINE 47. General Remarks In the historical summary given in the first chapters, it was explained how the theory of wave propagation first started with the discussion of waves along a discontinuous string. Then followed the theory of waves in a continuous medium, and we emphasized the importance of some of Lord Kelvin's remarks on waves in a discontinuous structure and the existence of a cutoff frequency. Up to Kelvin's time only one type of wave had been discussed, viz., elastic waves. Later electromagnetic waves and, still later, electron waves in wave mechanics were discovered, and the properties first obtained for elastic waves were immediately translated for these new waves. For instance, Lagrange's theory of how to pass from the discontinuous string to the limit of a continuous string was used by Pupin in his discussion of loaded telephonic cables. The deep discussion of Kelvin, related in Sec. 2, led him to imagine a new model for an optical medium. A similar mechanical model was built by Vincent and proved to have the properties of a mechanical band-pass filter. This model was translated into an electrical circuit by Campbell and was the point of departure for his invention of electric filters, of which he gave a number of important applications. Hence, for scientists of the last century, it was common knowledge that the special nature of the waves did not matter and that the same general properties could be found for any type of waves. The general relations among the various types of waves seem to have been forgotten for some time. Physicists developed the theory of electromagnetic waves for optics and X rays. Then theoreticians discussed very carefully the properties of electron waves (wave mechanics) in crystals and too often did not pay attention to the fact that a great part of the work had already been done in the theory of X-ray propagation in crystals.On the other hand, electrical engineer one lines on analysis on the theory of propagation of waves along lines, cables, filters, etc., but omitted to notice that many important facts had already been discovered by theoretical physicists (see Secs. 13 and 14). More recently, practical acoustics was revived, mostly by electrical engineers, who were especially well trained in electriccircuit theory and found it easier to translate mechanical problems into the equivalent electric circuits before discussion. These scientists at last rediscovered the similarity of all problems of vibration and wave propagation, but they did just the opposite of what their ancestors had done. Pupin and Campbell started from mechanical models to discuss electric lines and filters. A modern engineer, wishing to discuss wave propagation along a train of railway cars, translates the problem into an electrical one (an impulse propagating along a filter) and then translates the answer back into mechanical terms. This explains why we want to include a general discussion of wave propagation along electric lines and filters in this book. Many modern theoretical physicists have hardly heard of these problems and do not realize the very great advance in the theory by this engineer's art. Engineers, on the other hand, have a tendency to imagine that any wave problem can be reduced to a problem in electric lines, and this is not entirely true. We have already discussed in Chap. V the importance and the limitations of the concept of characteristic or surge impedance. This concept is fundamental for one-dimensional structures such as mechanical or electric lines and filters. Its generalization for three dimensions is not so easy, and we noted that the definition of energy flow, exemplified by the Poynting vector for electromagnetic waves or similar definitions in wave mechanics, is better adapted to the three- or four-dimensional problems. Recent developments in wave mechanics point to the importance of matrix calculus and its very close connection with a number of problems of wave propagation. It is very interesting to note that electrical engineers have independently come to the same conclusion. Matrix theory is now commonly used in the discussion of problems of waves in electric filters.
Sep 23, 2020
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Asim Barut on non-perturbative QED / Conal Elliott on non-monadic IO
The third period of electron's history opens with the unexpected wave and spin properties of the electron and leads to the picture according to Schrödinger and Dirac, the electron described by a wave equation, and ends with the QED picture of the electron. It is remarkable that such a seemingly simple object as an electron has produced so many surprises. In view of the appearance of heavy leptons, like muon and tau which are very much like the electron, I am tempted to conjecture a fourth period in which we may be again surprised by a nonperturbative internal structure of the electron. The perturbative treatment of electron interactions by Feynman graphs has somewhat diminished the preeminence of the electron; it is just one of the many “elementary” particles. But these results have not solved the structure problem. In the last sentence of his famous review article on Quantum Theory of Radiation Fermi writes: “In conclusion, we may therefore say that practically all the problems in radiation theory which do not involve the structure of the electron have their satisfactory explanation; while the problems connected with the internal properties of the electron are still very far from their solution”. Sadly–and here is the real intent behind my post–many Haskell programmers believe that IO is necessary to do “real programming”, and they use Haskell as if it were C (relegating lots of work to IO). In other words, monadic IO has proved to be such a comfortable “solution” to I/O in a functional language, that very few folks are still searching for a genuinely (not merely technically) functional solution. Before monadic IO, there was a lot of vibrant and imaginative work on functional I/O. It hadn’t arrived yet, but was still in touch with the Spirit of functional programming. With the invention and acceptance of monadic imperative programming, it’s like the Haskell community wandered into an opium den and are still lying there in a fog.
Oct 17, 2020
@smdiehl: Morning thought, I don't think I can point to /any/ programming book written after 2005 that was inspirational or really changed my thinking about the field.
Oct 17, 2020
@sjsyrek @smdiehl If you have an open-minded definition of "programming", "Exploring ODEs" by Trefethen and co came out in 2018, and it's nothing short of a masterpiece. It's basically a playable book! tobydriscoll.net/project/explode
The first thing to do with nonlinear problems is enjoy them. The chances are you can't solve a particular nonlinear ODE analytically, but there is a wonderful variety of effects to explore.
Nov 2, 2020
@pchiusano I think the binary coders also rejected asm because it required much more CPU time (= $$) and more card passes (submit an asm card deck, get back a machine code deck, then resubmit that!). For compilation to make sense, the *entire physical environment* had to change.
Nov 2, 2020
@pchiusano Genuinely transformative ideas initially tend to be awkward and impractical -- before they reshape the environment around them. It may be less that the experts are hardheaded and more that they care about getting something done "today", so they take the environment as given.
Nov 2, 2020
@pchiusano Which is to say, the experts may be making perfectly correct decisions with respect to getting short-term results, while simultaneously being a huge drag on long-term progress. Often, their explicit responsibility is to the former, not the latter.
Dec 28, 2020
@tophtucker: last night i dreamt i was in a giant @bw walkthrough room, all the pages were like six feet tall and everyone was there
Dec 28, 2020
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@tophtucker wait, sometimes I forget that instead of showing dumb mockups I can show the actual thing @glench @rmozone
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