5 ms·

Paul Dirac: The unsung genius

112 points by twidlit 15y ago

da-bacon 15y ago
One of my favorite Dirac stories "An interview with Dirac": http://www.math.rutgers.edu/~greenfie/mill_courses/math421/int.html http://www.math.rutgers.edu/~greenfie/mill_courses/math421/i...
richbradshaw 15y ago
There's been the same poster of him within an average of 1km from me since I was 17! My Physics class room at college had a copy, then my University had one, and now I have one in my Physics class room. So, pretty sure that he's well sung, at least in the rooms I visit!
archgoon 15y ago
You don't need the Dirac equation to understand semiconductor physics. Holes are not positrons, and I'm somewhat skeptical of the idea that if positrons had not been discovered or postulated, that the transistor would not have been invented. Without a doubt, it's really cool that we can say "Hey! We can actually predict that electrons will have spin!", but you don't need to understand that water is made up of hydrogen and oxygen to build a steam engine. However, if someone can point me to writings by Shockley, Brattain, or Bardeen, or a historical account that indicates otherwise, I'd be happy to read it :)
- Fixnum 15y ago
  I assume the article is referring to Fermi-Dirac statistics [1], not the Dirac equation. That said, the Dirac equation (or relativistic QM more generally) as well as the Feynman path integral (the idea of which originated from a 1933 paper of Dirac) are pretty indispensable in modern condensed matter physics. [1] https://secure.wikimedia.org/wikipedia/en/wiki/Fermi%E2%80%93Dirac_statistics#History https://secure.wikimedia.org/wikipedia/en/wiki/Fermi%E2%80%9...
  - archgoon 15y ago
    Two points 1) The article is primarily concerned with Dirac's relativistic formulation of quantum mechanics. This is why they make the claim 'Without understanding the origin of spin, and the Dirac statistics, you wouldn't have mobile phones, computers or anything else that runs on electronics.' However, Fermi-Dirac statistics can be derived directly from the properties of fermions. True, you can derive the fact that electrons will be fermions because of their spin from the spins-statistics theorem, but you only need to know the Pauli Exclusion principle to get the F-D statistics. 2) My understanding, and speaking with engineers in the field, is that most of the applied industrial research uses empirically derived band structures (which definitely does require Rel. QM to derive from first principles) and regular QM to design devices. This is also the approach I've seen in most semiconductor simulators. However, it is entirely possible that Intel or AMD take a different approach. Not having access to the tools they use, I can't speak to their tech. However, you seem to be a knowledgeable person, so I'd be more than happy to be informed that I'm full of shit here. :)
- anamax 15y ago
  > You don't need the Dirac equation to understand semiconductor physics. Holes are not positrons, and I'm somewhat skeptical of the idea that if positrons had not been discovered or postulated, that the transistor would not have been invented. The MOSFET was patented in 1925 by Julius Edgar Lilienfeld. I don't know if he knew about positrons. http://en.wikipedia.org/wiki/MOSFET http://en.wikipedia.org/wiki/MOSFET .
  - archgoon 15y ago
    >The MOSFET was patented in 1925 by Julius Edgar Lilienfeld. I don't know if he knew about positrons. He would not have known anything about positrons. Dirac's major triumph was the prediction of positrons in 1928, before empirical evidence for them existed. Thank you for reminding me about Lillienfield's patents. It is a good example of why the basic idea of transistors don't require even quantum mechanics (Schroedinger published his equation in 1926). Furthermore, since you need to toss in feedback in anycase, the need for accurately predicting the actual magnitude of gain, is significantly diminished for initial applications. If you read the Art of Electronics, you'll note that one of the things they point out is that you shouldn't base a circuit design that relies too heavily on a particular value of the amplification.
arethuza 15y ago
Not being a physicist, but hanging out with control engineers for many years, I was actually introduced to Dirac through his Delta Function: http://en.wikipedia.org/wiki/Dirac_delta_function http://en.wikipedia.org/wiki/Dirac_delta_function One thing I hadn't appreciated until recently was that Dirac held the Lucasian Chair at Cambridge. The list of people who have held this post is really rather impressive: http://en.wikipedia.org/wiki/Lucasian_Professor_of_Mathematics http://en.wikipedia.org/wiki/Lucasian_Professor_of_Mathemati...
- zerostar07 15y ago
  He was also quite modest, not naming equations after himself, and used to refer to Fermi-Dirac statistics as "Fermi statistics". Btw, how did PAM Dirac come up? Is it some celebration i am unaware of?
  - arethuza 15y ago
    The earlier HN thread about Feynman mentions Dirac: http://news.ycombinator.com/item?id=3230826 http://news.ycombinator.com/item?id=3230826
- apu 15y ago
  Hah I was just going through the list of Lucasian professors, and found http://en.wikipedia.org/wiki/Joshua_King http://en.wikipedia.org/wiki/Joshua_King When he died, it was felt that the memory of such an extraordinary man should not be permitted to die out, and his papers should be published. So his papers were examined, and nothing whatever worth publishing was found
Jd 15y ago
A bit of an aside, but one of the best Evangelion episodes invovlves a Dirac Sea: http://www.youtube.com/watch?v=-aoLMp6q3js http://www.youtube.com/watch?v=-aoLMp6q3js
- apu 15y ago
  I always cringe when I see math or programming or anything I know something about in popular media as it's usually done so poorly. So how badly did they butcher the concept of the Dirac sea for the episode? Of course it's all fiction anyways, so it doesn't really matter, but the inner geek in me wants to know!
  - Jd 15y ago
    Unusually, I don't think it was butchered particularly badly. The sea I believe existed inside of the attacking "angel," and had certain psychological-probing properties.
dlokshin 15y ago
"He accepted it [Nobel Prize] only when advised that, as the first person to refuse a Nobel Prize, the publicity would be even greater" Couldn't be more true.
- phaus 15y ago
  The Nobel prize has become such a joke in the last two decades I am surprised that rejecting it hasn't become the norm. The Nobel peace prize has been awarded to a child molester, a supporter of international terrorism, and a president who had just been elected. In addition to these travesties there was also the "Inconvenient Truth" debacle. (I'm not denying global warming, I just don't think being a narrator warrants a medal and a million dollars.)
  - SamReidHughes 15y ago
    What does that have to do with the physics prize?
  - nl 15y ago
    I think you might be talking about the Nobel Peace Prize? That is fairly different to the other Nobel prizes. As an example of how different they are, the Noble Peace Prize is awarded by a Norwegian committee[1], whilst the other prizes are awarded by various Swedish committees[2][3][4]. [1] http://en.wikipedia.org/wiki/Norwegian_Nobel_Committee http://en.wikipedia.org/wiki/Norwegian_Nobel_Committee [2] http://en.wikipedia.org/wiki/Royal_Swedish_Academy_of_Sciences http://en.wikipedia.org/wiki/Royal_Swedish_Academy_of_Scienc... [3] http://en.wikipedia.org/wiki/Nobel_Assembly_at_Karolinska_Institutet http://en.wikipedia.org/wiki/Nobel_Assembly_at_Karolinska_In... [4] http://en.wikipedia.org/wiki/Swedish_Academy http://en.wikipedia.org/wiki/Swedish_Academy
rb2k_ 15y ago
Little trivia: The BCC develops a wavelet based video codec they call "Dirac"[0] [0] http://en.wikipedia.org/wiki/Dirac_(video_compression_format) http://en.wikipedia.org/wiki/Dirac_(video_compression_format...
ionfish 15y ago
I recommend Graham Farmelo's 2009 biography of Dirac, The Strangest Man. http://www.guardian.co.uk/science/2009/apr/02/paul-dirac-strangest-man-farmelo-quantum http://www.guardian.co.uk/science/2009/apr/02/paul-dirac-str... I once started a physics degree at Bristol, where Dirac was born and raised, and the department made a big show of 'their' man. The house he grew up in is a few minutes' walk from the department, and has a blue plaque indicating its status. It was some years before I discovered that Dirac had never been in the physics department at all, but in fact studied electrical engineering, before entering Cambridge, where he flourished as a physicist.
- ikirill 15y ago
  One of the finer points of that book is that it is a biography of Dirac's life, not just a description of his insights into physics. His personal life was unhappy and makes for rather depressing reading. When Feynman was described as a second Dirac, only this time human, it is difficult to appreciate fully just how fundamentally different the personalities of the two geniuses were. Between studying electrical engineering and going to Cambridge he also earned a degree in mathematics, if I recall correctly. He was not given a sufficiently large scholarship the first time he was accepted to Cambridge, and so he had to wait.
- ig1 15y ago
  I believe Bristol didn't have a Physics lab until the late 1920s after Dirac's time. Dirac actually had two undergrad degrees from Bristol, the first in Electrical Engineering and the second in Mathematics.
deleted 15y ago
[deleted]
Dn_Ab 15y ago
Speaking of unsung geniuses there is someone who I am always surprised people don't mention more. Everyone knows of Turing - no doubt related to the tragic nature of his death due to disgusting treatment and the ubiquity of his eponymous machine - but not as many know of or laud this person whose influence is at least as great. I guess that is partially of his own fashioning. He laid the practical foundation of digital circuits by noting the applicability of boolean algebra to circuit design. Electronic devices and computers are descendants of his work. After a brief hiatus to work on mathematical biology and cryptography he laid the foundation to the internet with his work on Communications/Information theory and contributions to sampling. His work on information theory is also vital in machine learning, Natural language parsing, compression and more; it finds utility in quantum physics and controversy in gravitational physics. He also had some of the earliest working examples of wearable computing, algorithmic trading, and artificial intelligence. Arguably, mores so than any scientist of recent times, there is not a person whose work more thoroughly infuses and touches our lives than Claude Shannon.
- zerostar07 15y ago
  I don't get why geniuses need to be sung as if it's a popularity contest. It's virtually impossible to do information theory without stumbling on Shannon's theorems just like it's not possible to do physics without Dirac. Those who need to know, do know.
  - Dn_Ab 15y ago
    They need to be sung because they can motivate people like me who read their stories in isolation and proceed to cultivate an interest in science. The sung heroes shape the tide of the collective imagination. There is no need for affectations of wisdom; in an economy of attention, merit just as popularity is a component in the vector of notability. Seeking to not acknowledge these things in the name of purity only polarizes and does no one any good.
- dhimes 15y ago
  I nominate Emmy Noether, whose work on the relationship between mathematical symmetry and conservation laws is still the heart of theoretical physics. http://en.wikipedia.org/wiki/Emmy_Noether http://en.wikipedia.org/wiki/Emmy_Noether Hers is a remarkable story indeed.
stashdot 15y ago
Yeah, he won a Nobel when he was 31. He's only unsung among the under-read.

112 points by twidlit 15y ago

One of my favorite Dirac stories "An interview with Dirac": http://www.math.rutgers.edu/~greenfie/mill_courses/math421/int.html http://www.math.rutgers.edu/~greenfie/mill_courses/math421/i...

richbradshaw 15y ago

There's been the same poster of him within an average of 1km from me since I was 17! My Physics class room at college had a copy, then my University had one, and now I have one in my Physics class room. So, pretty sure that he's well sung, at least in the rooms I visit!

archgoon 15y ago

You don't need the Dirac equation to understand semiconductor physics. Holes are not positrons, and I'm somewhat skeptical of the idea that if positrons had not been discovered or postulated, that the transistor would not have been invented. Without a doubt, it's really cool that we can say "Hey! We can actually predict that electrons will have spin!", but you don't need to understand that water is made up of hydrogen and oxygen to build a steam engine. However, if someone can point me to writings by Shockley, Brattain, or Bardeen, or a historical account that indicates otherwise, I'd be happy to read it :)

Fixnum 15y ago
I assume the article is referring to Fermi-Dirac statistics [1], not the Dirac equation. That said, the Dirac equation (or relativistic QM more generally) as well as the Feynman path integral (the idea of which originated from a 1933 paper of Dirac) are pretty indispensable in modern condensed matter physics. [1] https://secure.wikimedia.org/wikipedia/en/wiki/Fermi%E2%80%93Dirac_statistics#History https://secure.wikimedia.org/wikipedia/en/wiki/Fermi%E2%80%9...
- archgoon 15y ago
  Two points 1) The article is primarily concerned with Dirac's relativistic formulation of quantum mechanics. This is why they make the claim 'Without understanding the origin of spin, and the Dirac statistics, you wouldn't have mobile phones, computers or anything else that runs on electronics.' However, Fermi-Dirac statistics can be derived directly from the properties of fermions. True, you can derive the fact that electrons will be fermions because of their spin from the spins-statistics theorem, but you only need to know the Pauli Exclusion principle to get the F-D statistics. 2) My understanding, and speaking with engineers in the field, is that most of the applied industrial research uses empirically derived band structures (which definitely does require Rel. QM to derive from first principles) and regular QM to design devices. This is also the approach I've seen in most semiconductor simulators. However, it is entirely possible that Intel or AMD take a different approach. Not having access to the tools they use, I can't speak to their tech. However, you seem to be a knowledgeable person, so I'd be more than happy to be informed that I'm full of shit here. :)
anamax 15y ago
> You don't need the Dirac equation to understand semiconductor physics. Holes are not positrons, and I'm somewhat skeptical of the idea that if positrons had not been discovered or postulated, that the transistor would not have been invented. The MOSFET was patented in 1925 by Julius Edgar Lilienfeld. I don't know if he knew about positrons. http://en.wikipedia.org/wiki/MOSFET http://en.wikipedia.org/wiki/MOSFET .
- archgoon 15y ago
  >The MOSFET was patented in 1925 by Julius Edgar Lilienfeld. I don't know if he knew about positrons. He would not have known anything about positrons. Dirac's major triumph was the prediction of positrons in 1928, before empirical evidence for them existed. Thank you for reminding me about Lillienfield's patents. It is a good example of why the basic idea of transistors don't require even quantum mechanics (Schroedinger published his equation in 1926). Furthermore, since you need to toss in feedback in anycase, the need for accurately predicting the actual magnitude of gain, is significantly diminished for initial applications. If you read the Art of Electronics, you'll note that one of the things they point out is that you shouldn't base a circuit design that relies too heavily on a particular value of the amplification.

arethuza 15y ago

Not being a physicist, but hanging out with control engineers for many years, I was actually introduced to Dirac through his Delta Function: http://en.wikipedia.org/wiki/Dirac_delta_function http://en.wikipedia.org/wiki/Dirac_delta_function One thing I hadn't appreciated until recently was that Dirac held the Lucasian Chair at Cambridge. The list of people who have held this post is really rather impressive: http://en.wikipedia.org/wiki/Lucasian_Professor_of_Mathematics http://en.wikipedia.org/wiki/Lucasian_Professor_of_Mathemati...

zerostar07 15y ago
He was also quite modest, not naming equations after himself, and used to refer to Fermi-Dirac statistics as "Fermi statistics". Btw, how did PAM Dirac come up? Is it some celebration i am unaware of?
- arethuza 15y ago
  The earlier HN thread about Feynman mentions Dirac: http://news.ycombinator.com/item?id=3230826 http://news.ycombinator.com/item?id=3230826
apu 15y ago
Hah I was just going through the list of Lucasian professors, and found http://en.wikipedia.org/wiki/Joshua_King http://en.wikipedia.org/wiki/Joshua_King When he died, it was felt that the memory of such an extraordinary man should not be permitted to die out, and his papers should be published. So his papers were examined, and nothing whatever worth publishing was found

Jd 15y ago

A bit of an aside, but one of the best Evangelion episodes invovlves a Dirac Sea: http://www.youtube.com/watch?v=-aoLMp6q3js http://www.youtube.com/watch?v=-aoLMp6q3js

apu 15y ago
I always cringe when I see math or programming or anything I know something about in popular media as it's usually done so poorly. So how badly did they butcher the concept of the Dirac sea for the episode? Of course it's all fiction anyways, so it doesn't really matter, but the inner geek in me wants to know!
- Jd 15y ago
  Unusually, I don't think it was butchered particularly badly. The sea I believe existed inside of the attacking "angel," and had certain psychological-probing properties.

dlokshin 15y ago

"He accepted it [Nobel Prize] only when advised that, as the first person to refuse a Nobel Prize, the publicity would be even greater" Couldn't be more true.

phaus 15y ago
The Nobel prize has become such a joke in the last two decades I am surprised that rejecting it hasn't become the norm. The Nobel peace prize has been awarded to a child molester, a supporter of international terrorism, and a president who had just been elected. In addition to these travesties there was also the "Inconvenient Truth" debacle. (I'm not denying global warming, I just don't think being a narrator warrants a medal and a million dollars.)
- SamReidHughes 15y ago
  What does that have to do with the physics prize?
- nl 15y ago
  I think you might be talking about the Nobel Peace Prize? That is fairly different to the other Nobel prizes. As an example of how different they are, the Noble Peace Prize is awarded by a Norwegian committee[1], whilst the other prizes are awarded by various Swedish committees[2][3][4]. [1] http://en.wikipedia.org/wiki/Norwegian_Nobel_Committee http://en.wikipedia.org/wiki/Norwegian_Nobel_Committee [2] http://en.wikipedia.org/wiki/Royal_Swedish_Academy_of_Sciences http://en.wikipedia.org/wiki/Royal_Swedish_Academy_of_Scienc... [3] http://en.wikipedia.org/wiki/Nobel_Assembly_at_Karolinska_Institutet http://en.wikipedia.org/wiki/Nobel_Assembly_at_Karolinska_In... [4] http://en.wikipedia.org/wiki/Swedish_Academy http://en.wikipedia.org/wiki/Swedish_Academy

rb2k_ 15y ago

Little trivia: The BCC develops a wavelet based video codec they call "Dirac"[0] [0] http://en.wikipedia.org/wiki/Dirac_(video_compression_format) http://en.wikipedia.org/wiki/Dirac_(video_compression_format...

ionfish 15y ago

I recommend Graham Farmelo's 2009 biography of Dirac, The Strangest Man. http://www.guardian.co.uk/science/2009/apr/02/paul-dirac-strangest-man-farmelo-quantum http://www.guardian.co.uk/science/2009/apr/02/paul-dirac-str... I once started a physics degree at Bristol, where Dirac was born and raised, and the department made a big show of 'their' man. The house he grew up in is a few minutes' walk from the department, and has a blue plaque indicating its status. It was some years before I discovered that Dirac had never been in the physics department at all, but in fact studied electrical engineering, before entering Cambridge, where he flourished as a physicist.

ikirill 15y ago
One of the finer points of that book is that it is a biography of Dirac's life, not just a description of his insights into physics. His personal life was unhappy and makes for rather depressing reading. When Feynman was described as a second Dirac, only this time human, it is difficult to appreciate fully just how fundamentally different the personalities of the two geniuses were. Between studying electrical engineering and going to Cambridge he also earned a degree in mathematics, if I recall correctly. He was not given a sufficiently large scholarship the first time he was accepted to Cambridge, and so he had to wait.
ig1 15y ago
I believe Bristol didn't have a Physics lab until the late 1920s after Dirac's time. Dirac actually had two undergrad degrees from Bristol, the first in Electrical Engineering and the second in Mathematics.

deleted 15y ago

[deleted]

Dn_Ab 15y ago

Speaking of unsung geniuses there is someone who I am always surprised people don't mention more. Everyone knows of Turing - no doubt related to the tragic nature of his death due to disgusting treatment and the ubiquity of his eponymous machine - but not as many know of or laud this person whose influence is at least as great. I guess that is partially of his own fashioning. He laid the practical foundation of digital circuits by noting the applicability of boolean algebra to circuit design. Electronic devices and computers are descendants of his work. After a brief hiatus to work on mathematical biology and cryptography he laid the foundation to the internet with his work on Communications/Information theory and contributions to sampling. His work on information theory is also vital in machine learning, Natural language parsing, compression and more; it finds utility in quantum physics and controversy in gravitational physics. He also had some of the earliest working examples of wearable computing, algorithmic trading, and artificial intelligence. Arguably, mores so than any scientist of recent times, there is not a person whose work more thoroughly infuses and touches our lives than Claude Shannon.

zerostar07 15y ago
I don't get why geniuses need to be sung as if it's a popularity contest. It's virtually impossible to do information theory without stumbling on Shannon's theorems just like it's not possible to do physics without Dirac. Those who need to know, do know.
- Dn_Ab 15y ago
  They need to be sung because they can motivate people like me who read their stories in isolation and proceed to cultivate an interest in science. The sung heroes shape the tide of the collective imagination. There is no need for affectations of wisdom; in an economy of attention, merit just as popularity is a component in the vector of notability. Seeking to not acknowledge these things in the name of purity only polarizes and does no one any good.
dhimes 15y ago
I nominate Emmy Noether, whose work on the relationship between mathematical symmetry and conservation laws is still the heart of theoretical physics. http://en.wikipedia.org/wiki/Emmy_Noether http://en.wikipedia.org/wiki/Emmy_Noether Hers is a remarkable story indeed.

stashdot 15y ago

Yeah, he won a Nobel when he was 31. He's only unsung among the under-read.