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Paul Dirac

by James Reason8
Tags: dirac, paul
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James Reason8
#1
Jun24-10, 06:45 PM
P: 2
Good book, The Strangest Man by Graham Farmelo a biography of Paul Dirac man into antimatter, not just physics but also generally how things were in the 1900`s including the wars and politics
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Dickfore
#2
Jun24-10, 06:53 PM
P: 3,014
Paul Dirac was born in 1902, so he was at most in 2nd grade by the end of 1900's.
James Reason8
#3
Jun24-10, 06:58 PM
P: 2
Hey the root, besides the book tells about his father Charles and the first thought of antimatter was late 1800`s, not by him

Dickfore
#4
Jun24-10, 07:39 PM
P: 3,014
Paul Dirac

Quote Quote by James Reason8 View Post
...the first thought of antimatter was late 1800`s, not by him
True, but those were associated with ideas about matter with negative gravity and aether theories as sinks in the flow of aether as opposed to sources (squirts) which were interpreted as ordinary matter.

Both of these ideas ware discarded by the time Dirac proposed his own theory. The most important aspect of matter and antimatter is that there is a gap between the two states equal to 2mc2, which can be considered a consequence of Special Relativity - a theory which made aether obsolete. Also, antimatter has the same gravitational properties as ordinary matter.
Theorem.
#5
Jul8-10, 04:31 AM
P: 237
The book is one of my favorites. It is very engaging and not technical. I think when the topic creator refereed to the 1900`s he was referring to the 20th century in general, which is entirely correct. There are few books I have read (and I read a lot) that rival this one.
Ken Natton
#6
Aug1-10, 05:38 AM
P: 272
Following George Jones’s recommendation, I have now obtained a copy of this book and I am still in the early chapters, but already I can quite understand the enthusiasm expressed by the other posters on this thread. Of course, I want to read the whole thing before I have too much to say about the book itself, but there was one particular passage I have already read that was so striking and actually amusing for reasons not particularly related to the subject of this book itself, that I thought it worth an early mention.

I have seen how many of the more established contributors to these forums like to have signatures to their posts that often contain some pithy aphorism, often one that has something to say about their view of less experienced contributors, and their sometimes over hastiness to post. In the early chapters of the book, Farmelo is dealing with all of the disparate influences on Dirac in his formative years and makes mention of one individual called Charlie Broad who was Professor of Philosophy at the University of Bristol. If you feel your defences rising at that mention of Philosophy then relax, Farmelo nicely explains how Broad was one of the more reliable lecturers on Relativity Theory in its early days and as such someone who had a rare ability to command Dirac’s serious attention, even though Broad himself later referred to Dirac as ‘…one whose shoelaces I was not worthy to unloose…’ There are a couple of direct quotes from Broad that Farmelo offers that could stand very well as signature aphorisms. Ones that also nicely demonstrate how little has changed in the ninety something years since Relativity Theory burst onto the scene. (Yes I know the first paper was 1905, but late 1919 is when Relativity Theory first started to receive wide attention). I apologise if I’m stating the obvious, but just trying to anticipate and prevent any objections, let me just mention that one does need to catch the dry tone of the first one in particular to properly understand it. In any case, just consider these:

‘A philosopher who regards ignorance of a scientific theory as insufficient reason for not writing about it cannot be accused of complete lack of originality.’

‘popular expositions of the Theory are either definitely wrong, or so loosely expressed as to be dangerously misleading; and all pamphlets against it – even when issued by eminent Oxford tutors – are based on elementary misunderstandings.’

I used to engage with another forum on Darwin & Evolution which was, inevitably, plagued by anti-evolutionists. Oh how well that second quote could be applied to them! I like this Charlie Broad character. I like him a lot.
yossell
#7
Aug1-10, 06:51 AM
P: 341
Quote Quote by Ken Natton View Post
‘A philosopher who regards ignorance of a scientific theory as insufficient reason for not writing about it cannot be accused of complete lack of originality.’
Nobody who doesn't write with insufficiently few double negatives cannot be regarded without a certain amount of lack of disrespect.
Ken Natton
#8
Aug1-10, 07:48 AM
P: 272
Ah yes yossel, an absolute masterpiece. I trust that I can expect to see your own version as your signature aphorism then? You have succeeded in making me read Broad’s quote a little differently, but I still think it was underpinned by a similar dry, pretension bursting intention as your own. My impression, from Farmelo’s account of him, is that Broad’s outlook was of the same school of thought as your own.
yossell
#9
Aug1-10, 10:07 AM
P: 341
Quote Quote by Ken Natton View Post
Ah yes yossel, an absolute masterpiece. I trust that I can expect to see your own version as your signature aphorism then? You have succeeded in making me read Broad’s quote a little differently, but I still think it was underpinned by a similar dry, pretension bursting intention as your own. My impression, from Farmelo’s account of him, is that Broad’s outlook was of the same school of thought as your own.
I agree - I actually felt guilty and cheap after posting that comment; in those days, for a certain kind of wry, independently-schooled Oxbridge academic, it wasn't unreasonable (sic) to speak in such a way.

Once I've worked out what my own aphorism actually says, if I find I agree with it, I may well include it as my signature.
Ken Natton
#10
Aug1-10, 12:29 PM
P: 272
Oh no, not at all yossell. I'm loath to take this discussion too far from the book about Dirac, but I do intend to post more about that when I've read it. I've already progressed a few chapters since this morning and it is deeply compelling.

But meantime, let me make it clear. While Broad's comment gave me a wry inward smile, your's caused me to laugh out loud such that my wife wanted to know what I was laughing at. I then had to explain it to her knowing that there was no way she would have the faintest idea why I found it so funny. You've got a lot to answer for yossell.
epenguin
#11
Aug1-10, 07:29 PM
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I made some comments on Dirac earlier to say that he made one contribution that seems to me quite unique: predicting from fundamental (though new) principles, and even aesthetic criteria, not just the behaviour of simple constituents of the world, but their existence.

http://www.physicsforums.com/showpos...&postcount=146

The book suggests he and his time were right for each other and for this discovery, that later as well as earlier his style would not have (and did not) yield such dramatic results. (This could be said for Einstein too).

From the book I now know another thing I would have had no way of guessing. He went to the same school and at the same time as Cary Grant.

No a lot of people know that.

Nor did they.
Ken Natton
#12
Aug2-10, 03:04 AM
P: 272
The idea that scientists tend to make their greatest discoveries at a relatively young age is something that has been much discussed and is a near universal truth. There are some examples of significant discoveries made by scientists at an older age, but that their greatest work was already completed by the time they were thirty is nothing unique to Dirac and Einstein. Equally, while we do sometimes hear of a particular discovery or an individual scientist being described as ahead of its or their time, the fact that such an idea is worthy of mention demonstrates that it is far more common for scientific discoveries and for scientists themselves to be considered of their time.

Farmelo gives a vivid account of how ripe many of the concepts of Quantum Physics were for discovery around the time that Dirac was producing his greatest work. I don’t have the text with me at the moment, but only last night I read Farmelo’s analogy of the (paraphrasing) bags of gemstones split open by Heisenberg and Schrödinger and the race that was on to find the diamonds. Several times Dirac thought he had made a significant advance only to find that someone else, sometimes more than one other, had reached a similar conclusion and published before him. It was cold comfort to Dirac to be credited as having stated the concept more concisely and elegantly than his rival. We all know the concept of the undefinability of a particle’s position and momentum as Heisenberg’s Uncertainty Principle. But until I read about it yesterday, I for one was completely unaware of how very nearly it was Dirac’s Uncertainty Principle.

And at best epenguin, your assessment of Dirac as a ‘miserable git’ is unsympathetic. As I was reading about it last night, I was thinking about how the people at Niels Bohr’s Copenhagen Institute responded to Dirac’s unusual character. Of course they would have found him off-putting, but if they had understood his inability to make an emotional connection with his own parents, they might have been more understanding of his inability to make any kind of connection, other than a purely scientific one, with them. I am not so far into the book yet, so I don’t know, but I am assuming Farmelo himself will address this issue at some point. But from the book’s cover I know that there is some question about whether or not Dirac was actually autistic. The notion that he might have been stems entirely from the accounts of just how severely he was emotionally crippled. Clearly his behaviour goes way beyond what would be considered ‘normal’. But it is perhaps also significant to recognise that he was no egotist. He made no demands whatever on anyone else. The only austerity he imposed was entirely upon himself. People’s only objection to him was because of the demands they placed on him to connect with them. And if they disliked the result, that was only because they didn’t understand that he simply wasn’t capable of it. Fortunately, some of the prominent figures around him did understand.
Ken Natton
#13
Aug8-10, 10:44 PM
P: 272
It doesn’t seem terribly likely that I am going to generate much discussion about this book. And I make no assumptions that anyone cares much about what I think of it. I might even have been concerned that posting about this book might be frowned on, given just how strongly Physics Forums seeks to defend its position as a purely scientific and not in any way a philosophical group of forums. Except that, of course, I didn’t start this thread, and more particularly, I was lead to this thread, and indeed to the book this thread is about, by one of the forum mentors. In any case, having read it, I have some points that I think are worthwhile making, so what the hell. If this post echoes around an empty chamber then, so be it.

For a biography written with quite such acute judgement and unerring professionalism as this one, it is quite surprising to have Farmelo afford real insight into his own personal response to Dirac, into his researches for this book, and even a little insight into his own career in the penultimate chapter. The first person pronoun suddenly appears unexpectedly when you are nearly through what is a deep and penetrating third person account that does demand quite a bit of effort from its reader. Its not that it is unwelcome or intrusive, it just takes you by surprise a little bit. It is a real change of mood just as you are reaching the end.

From that chapter, it emerges that Farmelo is himself a student of theoretical physics. I suppose that it would seem that he would have to be to write any kind of an insightful biography of a man who possessed one of the twentieth century’s most exceptional scientific minds. But it is clear enough that Farmelo is a bona fide writer, and while he does undoubtedly deal with the science very skilfully, I would suggest that anyone coming to this book looking for a deep technical understanding of Dirac’s scientific work is likely to be disappointed. It does do a very comprehensive job of laying out the precise context for each of Dirac’s important scientific achievements. Personally, I find that fascinating and believe in the value and importance of that insight. But I can understand that many would not share that view. Dirac, for example. It is clear that Einstein was a genuine scientific hero for Dirac, but I have the strongest feeling that he never read a biography of Einstein. In any case, it is clear enough to me that the exercise of writing this book was, and the value and benefit in reading it is entirely philosophical.

This goes to the heart of my own personal drive to understand. When I hear some of the more seemingly outlandish, counter-intuitive, sometimes scepticism provoking scientific ideas, I don’t just want to have the technical details explained to me, I always feel a compunction to understand what generated the idea, what lead serious, dispassionate, rational scientists to offer such a challenging idea as a scientific explanation. That is why I found such a resonance in the account of Dirac’s efforts to find out more about relativity theory when few courses were available and very little literature about it was reliable. Farmelo tells us that
‘[Dirac wanted to] find an accessible technical account of the [relativity] theory that would explain, step by step, how Einstein had developed his ideas.'
And yet, and yet, when Dirac himself later became an educator, both as an author of text books and as a lecturer, his reputation was built on a straight to the heart of the matter approach that was most appreciated by the best students. Farmelo gives a telling account of the occasion when Niels Bohr first received a copy of Dirac’s textbook The Principles of Quantum Mechanics.
‘Even if the author’s name were not on the cover, his identity would have been obvious to Bohr from a quick flick through: the unadorned presentation, the logical construction of the subject from first principles, and the complete absence of historical perspective, philosophical niceties and illustrative calculations.’
A little like the music of Bach, the most telling evidence of just how good his work was is the response it drew from those best placed to know.
‘Dirac’s peers marvelled at its elegance and at the deceptively plain language, which somehow seemed to reveal new insights on each reading, like a great poem.’
And for me, the reality of the impossibility of penetrating Dirac’s great contribution to scientific literature comes in Farmelo’s next comment:
‘The book had been written with no regard for his readers’ intellectual shortcomings…’
But the book is not just a comprehensive account of Dirac’s own life, it also paints a very vivid picture of many of Dirac’s contemporaries. Heisenberg and Schrödinger, Bohr and Born, Kapitza and Ehrenfest, Pauli and Fermi, Oppenheimer and Feynman. It is interesting to think that biographies of nearly every one of these individuals could serve as a different perspective on virtually the same basic story – that of the early development of Quantum Physics. Many other prominent figures make their appearances like, Edward Teller and Eugene Wigner – the latter brother to Dirac’s wife.

And also in that same penultimate chapter, Farmelo does, finally, give his own consideration of whether or not Dirac was truly autistic. He considers the key criteria for a modern diagnosis of autism and notes that Dirac seems to fit every one. Except that autism is a condition from which its sufferers do not escape, and the story of Dirac’s life that the book has just finished telling does reflect the reality that Dirac did mellow in later life. Not just because of a marriage to someone that it was his great and unlikely good fortune to find, but because of the realities of being a professor at Cambridge that necessitated the learning of effective communication skills, and because of his membership of a scientific community that also made its contribution to drawing him out of himself. Ultimately I suppose, Dirac’s upbringing was just a prime example of the kind of thing that Larkin’s infamous poem refers to and his extreme introspection in his younger days was caused by demons that he never totally exorcised, but ones he eventually learned to live with and to control.


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