Re: [ccp4bb] popular piece on X-ray crystallography
The cycles of accretion, nuclear interconversions and cooling of matter is far from complete but if we fast forward the universe by n billions of years, it's remarkable how much of it turns out to be crystalline. A bit like a crystallization trial at a cosmic scale. Does assume an expanding(-enough) cosmological model though. I should have made clear that the humor was well taken. Best regards, Navdeep --- On Fri, Apr 19, 2013 at 03:11:13PM +0100, Peter Artymiuk wrote: Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisible best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND -- --- Dr. med. Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ ---
Re: [ccp4bb] popular piece on X-ray crystallography
James's original rather short comment about Debye's key observation in 1915 was clearly casting in to the CCP4BB fish pond to see who would bite. I guess I was that fish. There seems to be some confusion over dates (1914 or 1915) but this is not important. I agree that determining the size of atoms was significant but stating that it ended determinism is pushing it a bit. I don't think Debye, or anyone else at the time, recognised it as ending determinism. In fact, according to a recent book (Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913-1925. Helge Kragh - around page 130) Debye adopted a classical view of atomic orbitals in disagreement with Bohr. It seems that Debye believed up to about 1917 that his failure to observe these orbitals via x-ray scattering was due to inadequacies in his equipment. Max Born is often credited with ending determinism - for example annoying both Schrodinger and Einstein with his interpretation of Schrodinger's wave equation as the probability of finding a particle in a particular position. Debye's Wikipedia entry is short on science and long on controversy. He clearly needs a sympathetic biography written by an admirer with a broad scientific knowledge. When James writes this biography he should address the above. Debye made several important scientific contributions and clearly deserved his Nobel prize (for molecular rather than atomic structure). I will happily buy James' biography of him unless I get a complimentary copy for suggesting he writes it. Quantum Mechanics works. Most practitioners accept this and don't worry too much about the many interpretations - Copenhagen, Bohm, many worlds etc. (see http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics and choose your favourite). However, when considering coherent scattering processes, one is less likely to make a mess of things if one sticks to a classical wave description. This would be my advice - not taken by the person who wrote the article published in the Metro. Colin From: James Holton [mailto:jmhol...@lbl.gov] Sent: 20 April 2013 05:07 To: Nave, Colin (DLSLtd,RAL,DIA) Cc: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography It was the observation that atoms have size. Rutherford's alpha-particle experiment had shown that the nucleus was incredibly small, very much smaller than the distances between atoms, bringing about the solar system idea, which right away came into question because such atoms would produce synchrotron radiation and the electrons would rapidly decay from their orbits. So, every nanosecond that the universe has not tuned itself into powdered neutronium is evidence against electrons in orbit. I think it was Laue who then proposed that the electrons must be bound very close to the nucleus (somehow). Making the atoms very sharp points, and separated from each other by vast distances (relative to their size). However, if the electrons really were confined to very sharp points, then the x-ray diffracted intensities from things like perfect rock salt crystals would not fall off with increasing sin(theta)/lambda. They would be relatively constant (much like the scattering profile of Rutherford's experiment). This was explained away as thermal vibrations blurring the atomic positions, making them look like they have size, and causing the spots to fade with increasing resolution. What Debye showed was that the temperature-dependence of this falloff was insufficient to give the atoms zero size, even when extrapolated to absolute zero (yes, they had liquid air in 1914), and this residual size was still comparable to bond lengths. That meant the electrons really were distributed in a cloud very far from the nucleus, and apparently not falling in. The only explanation is that the electron must be de-localised. And that is a quantum effect. I always thought that the paper Debye (1914) Ann. Phys. 348, 49-92 is perhaps one of the most remarkable in all of science. It is the original reference for the B factor, the Lorentz factor, and also the paper that ended determinism. At least, that is how I understand it. I had to return my English translation of the Debye paper to the library. I'll order my own copy. -James Holton MAD Scientist On Fri, Apr 19, 2013 at 2:38 PM, colin.n...@diamond.ac.ukmailto:colin.n...@diamond.ac.uk wrote: James In 1915, I thought Debye and Scherrer were testing for interference between the electrons in different orbits within atoms. This was in order to test the Bohr model. They got rings but they were powder diffraction rings. The method never did identify planetary type orbitals. However Debye eventually adjusted his aims and the method did become useful despite the requirement for objects to force themselves into ordered arrays Was there some other key observation Debye made in 1915 which you refer to? Colin -Original Message- From: CCP4 bulletin
Re: [ccp4bb] popular piece on X-ray crystallography
Boaz Shaanan sent me a nice reply about my comments below and gently mentioned that Debye was pursuing Bohrs orbits theory - not yet orbitals which came later. So this was an incorrect term which I used. The difference is something like Orbits - well defined path of electron round the nucleus Orbitals - Region of space where the probability of finding an electron is maximised Quite a key difference really in the context of determinism! Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Colin Nave Sent: 21 April 2013 14:38 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography James's original rather short comment about Debye's key observation in 1915 was clearly casting in to the CCP4BB fish pond to see who would bite. I guess I was that fish. There seems to be some confusion over dates (1914 or 1915) but this is not important. I agree that determining the size of atoms was significant but stating that it ended determinism is pushing it a bit. I don't think Debye, or anyone else at the time, recognised it as ending determinism. In fact, according to a recent book (Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913-1925. Helge Kragh - around page 130) Debye adopted a classical view of atomic orbitals in disagreement with Bohr. It seems that Debye believed up to about 1917 that his failure to observe these orbitals via x-ray scattering was due to inadequacies in his equipment. Max Born is often credited with ending determinism - for example annoying both Schrodinger and Einstein with his interpretation of Schrodinger's wave equation as the probability of finding a particle in a particular position. Debye's Wikipedia entry is short on science and long on controversy. He clearly needs a sympathetic biography written by an admirer with a broad scientific knowledge. When James writes this biography he should address the above. Debye made several important scientific contributions and clearly deserved his Nobel prize (for molecular rather than atomic structure). I will happily buy James' biography of him unless I get a complimentary copy for suggesting he writes it. Quantum Mechanics works. Most practitioners accept this and don't worry too much about the many interpretations - Copenhagen, Bohm, many worlds etc. (see http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics and choose your favourite). However, when considering coherent scattering processes, one is less likely to make a mess of things if one sticks to a classical wave description. This would be my advice - not taken by the person who wrote the article published in the Metro. Colin From: James Holton [mailto:jmhol...@lbl.gov] Sent: 20 April 2013 05:07 To: Nave, Colin (DLSLtd,RAL,DIA) Cc: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography It was the observation that atoms have size. Rutherford's alpha-particle experiment had shown that the nucleus was incredibly small, very much smaller than the distances between atoms, bringing about the solar system idea, which right away came into question because such atoms would produce synchrotron radiation and the electrons would rapidly decay from their orbits. So, every nanosecond that the universe has not tuned itself into powdered neutronium is evidence against electrons in orbit. I think it was Laue who then proposed that the electrons must be bound very close to the nucleus (somehow). Making the atoms very sharp points, and separated from each other by vast distances (relative to their size). However, if the electrons really were confined to very sharp points, then the x-ray diffracted intensities from things like perfect rock salt crystals would not fall off with increasing sin(theta)/lambda. They would be relatively constant (much like the scattering profile of Rutherford's experiment). This was explained away as thermal vibrations blurring the atomic positions, making them look like they have size, and causing the spots to fade with increasing resolution. What Debye showed was that the temperature-dependence of this falloff was insufficient to give the atoms zero size, even when extrapolated to absolute zero (yes, they had liquid air in 1914), and this residual size was still comparable to bond lengths. That meant the electrons really were distributed in a cloud very far from the nucleus, and apparently not falling in. The only explanation is that the electron must be de-localised. And that is a quantum effect. I always thought that the paper Debye (1914) Ann. Phys. 348, 49-92 is perhaps one of the most remarkable in all of science. It is the original reference for the B factor, the Lorentz factor, and also the paper that ended determinism. At least, that is how I understand it. I had to return my English translation of the Debye paper to the library. I'll order my own copy. -James Holton MAD Scientist On Fri
Re: [ccp4bb] popular piece on X-ray crystallography
Following up on the original post, I was recently asked to give a popular account of 100 years of X-ray diffraction in about 6 minutes :) This was broadcast on All India Radio from New Delhi on the 12th April across India, but the conservative estimates suggest that no more than 5 persons heard it live. I have a mp3 of the same (~6 MB). I will post it on my Facebook today. It will also be available on the Facebook of our Centre- National Centre for Cell Science, Pune, hopefully posted on Monday or Tuesday. Shekhar On Sat, Apr 20, 2013 at 9:37 AM, James Holton jmhol...@lbl.gov wrote: It was the observation that atoms have size. Rutherford's alpha-particle experiment had shown that the nucleus was incredibly small, very much smaller than the distances between atoms, bringing about the solar system idea, which right away came into question because such atoms would produce synchrotron radiation and the electrons would rapidly decay from their orbits. So, every nanosecond that the universe has not tuned itself into powdered neutronium is evidence against electrons in orbit. I think it was Laue who then proposed that the electrons must be bound very close to the nucleus (somehow). Making the atoms very sharp points, and separated from each other by vast distances (relative to their size). However, if the electrons really were confined to very sharp points, then the x-ray diffracted intensities from things like perfect rock salt crystals would not fall off with increasing sin(theta)/lambda. They would be relatively constant (much like the scattering profile of Rutherford's experiment). This was explained away as thermal vibrations blurring the atomic positions, making them look like they have size, and causing the spots to fade with increasing resolution. What Debye showed was that the temperature-dependence of this falloff was insufficient to give the atoms zero size, even when extrapolated to absolute zero (yes, they had liquid air in 1914), and this residual size was still comparable to bond lengths. That meant the electrons really were distributed in a cloud very far from the nucleus, and apparently not falling in. The only explanation is that the electron must be de-localised. And that is a quantum effect. I always thought that the paper Debye (1914) Ann. Phys. 348, 49-92 is perhaps one of the most remarkable in all of science. It is the original reference for the B factor, the Lorentz factor, and also the paper that ended determinism. At least, that is how I understand it. I had to return my English translation of the Debye paper to the library. I'll order my own copy. -James Holton MAD Scientist On Fri, Apr 19, 2013 at 2:38 PM, colin.n...@diamond.ac.uk wrote: James In 1915, I thought Debye and Scherrer were testing for interference between the electrons in different orbits within atoms. This was in order to test the Bohr model. They got rings but they were powder diffraction rings. The method never did identify planetary type orbitals. However Debye eventually adjusted his aims and the method did become useful despite the requirement for objects to force themselves into ordered arrays Was there some other key observation Debye made in 1915 which you refer to? Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of James Holton Sent: 19 April 2013 18:27 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography Because there is never more than one photon in flight at any given time. Even at 1 photon/s, we still eventually get spots. Atoms also don't emit synchrotron radiation, despite there being charged particles accelerating around their little orbits in there. But yes, in 1913, people were still hoping there was another explanation for these two observations, other than that pesky quantum theory. It was in 1915 that Debye made the key observation that collapsed determinism as we knew it. I don't think he was very happy about that. Neither was Einstein. -James Holton MAD Scientist On 4/19/2013 9:43 AM, Tim Gruene wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular
Re: [ccp4bb] popular piece on X-ray crystallography
Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisible best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND
Re: [ccp4bb] popular piece on X-ray crystallography
Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisible best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND
Re: [ccp4bb] popular piece on X-ray crystallography
Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisible best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ ---
Re: [ccp4bb] popular piece on X-ray crystallography
Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisible best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND
Re: [ccp4bb] popular piece on X-ray crystallography
However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisi ble best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND
Re: [ccp4bb] popular piece on X-ray crystallography
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisi ble best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND - -- - -- Dr Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iD8DBQFRcXQyUxlJ7aRr7hoRAm2MAJ92WHxpnCeuwTDw/kcc6Qdy4ynBpgCgooRr MN2Rm2CU2N95Sz4Epd0lEj8= =Ai1+ -END PGP SIGNATURE-
Re: [ccp4bb] popular piece on X-ray crystallography
Because there is never more than one photon in flight at any given time. Even at 1 photon/s, we still eventually get spots. Atoms also don't emit synchrotron radiation, despite there being charged particles accelerating around their little orbits in there. But yes, in 1913, people were still hoping there was another explanation for these two observations, other than that pesky quantum theory. It was in 1915 that Debye made the key observation that collapsed determinism as we knew it. I don't think he was very happy about that. Neither was Einstein. -James Holton MAD Scientist On 4/19/2013 9:43 AM, Tim Gruene wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invisi ble best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND - -- - -- Dr Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iD8DBQFRcXQyUxlJ7aRr7hoRAm2MAJ92WHxpnCeuwTDw/kcc6Qdy4ynBpgCgooRr MN2Rm2CU2N95Sz4Epd0lEj8= =Ai1+ -END PGP SIGNATURE-
Re: [ccp4bb] popular piece on X-ray crystallography
Simply on grounds that even a single photon can get diffracted (remember the photon counting multiwire detectors?). The phenomenon might be best described as something like a annihilation-creation process a la Feynman. Much of this has been discussed on board before. Mini-summary: 'Multiphoton' somehow invokes at least in my mind necessary inter-photon coherence (to maintain phase relations) between multiple scattered photons, which is in general not the case nor necessary. The Bragg equation pictures showing 2 incoming x-rays are very deceiving. They should be seen as a help to understand the phase relation for the electric field vector of the ONE incoming photon resonating multiple atoms' electrons. The new photon then emerges based on a probability function proportional to the structure factors. You just can't predict which one it will be. That 3d (squared) probability distribution - after you have collected many photons - is your diffraction pattern. Chapter 6 introduction... Best, BR -Original Message- From: Tim Gruene [mailto:t...@shelx.uni-ac.gwdg.de] Sent: Friday, April 19, 2013 9:44 AM To: b...@hofkristallamt.org Cc: Bernhard Rupp (Hofkristallrat a.D.); CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invis i ble best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University
Re: [ccp4bb] popular piece on X-ray crystallography
James In 1915, I thought Debye and Scherrer were testing for interference between the electrons in different orbits within atoms. This was in order to test the Bohr model. They got rings but they were powder diffraction rings. The method never did identify planetary type orbitals. However Debye eventually adjusted his aims and the method did become useful despite the requirement for objects to force themselves into ordered arrays Was there some other key observation Debye made in 1915 which you refer to? Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of James Holton Sent: 19 April 2013 18:27 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography Because there is never more than one photon in flight at any given time. Even at 1 photon/s, we still eventually get spots. Atoms also don't emit synchrotron radiation, despite there being charged particles accelerating around their little orbits in there. But yes, in 1913, people were still hoping there was another explanation for these two observations, other than that pesky quantum theory. It was in 1915 that Debye made the key observation that collapsed determinism as we knew it. I don't think he was very happy about that. Neither was Einstein. -James Holton MAD Scientist On 4/19/2013 9:43 AM, Tim Gruene wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave David C. Briggs PhD http://about.me/david_briggs On 19 April 2013 09:44, Peter Artymiuk p.artym...@sheffield.ac.uk wrote: Dear all In Britain there is a free newspaper that you can pick up on buses called the Metro. My colleague Geoff Ford pointed out this short feature on the history X-ray crystallography in last Monday's Metro newspaper. I think it's rather good. http://www.cosmonline.co.uk/blog/2013/04/14/conquering-realm-invi si ble best wishes Pete Prof Peter Artymiuk Krebs Institute Department of Molecular Biology Biotechnology University of Sheffield Sheffield S10 2TN ENGLAND --- Navdeep Sidhu Departments of Structural Chemistry Pediatrics II University of Goettingen Office Address: Institute of Inorganic Chemistry Tammannstrasse 4 37077 Goettingen Germany Email: nsi...@shelx.uni-ac.gwdg.de Phone: +49 551 39 33059 Fax: +49 551 39 22582 Dept. Homepage: http://shelx.uni-ac.gwdg.de/ --- Prof Peter Artymiuk Krebs Institute
Re: [ccp4bb] popular piece on X-ray crystallography
I would like to add/support James comments. Once it used to bother me the fact that diffraction was observed from the crystal even though the beam does not possess a space-time coherence (or even worse in the case of in-house diffractometers). This is because in text books they always illustrated diffraction using two electrons hit by two incident coherent waves of same wavelength. Therefore, since the beam is in reality incoherent, it must be each photon interacting with itself as in the two-slit experiments. At least this is the explanation that I decided to believe since I couldn't come up with anything more logical. If I convinced myself with some false beliefs just to sleep better and some one could actually point me to the right explanation I would be really grateful. D From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: 19 April 2013 22:38 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography James In 1915, I thought Debye and Scherrer were testing for interference between the electrons in different orbits within atoms. This was in order to test the Bohr model. They got rings but they were powder diffraction rings. The method never did identify planetary type orbitals. However Debye eventually adjusted his aims and the method did become useful despite the requirement for objects to force themselves into ordered arrays Was there some other key observation Debye made in 1915 which you refer to? Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of James Holton Sent: 19 April 2013 18:27 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography Because there is never more than one photon in flight at any given time. Even at 1 photon/s, we still eventually get spots. Atoms also don't emit synchrotron radiation, despite there being charged particles accelerating around their little orbits in there. But yes, in 1913, people were still hoping there was another explanation for these two observations, other than that pesky quantum theory. It was in 1915 that Debye made the key observation that collapsed determinism as we knew it. I don't think he was very happy about that. Neither was Einstein. -James Holton MAD Scientist On 4/19/2013 9:43 AM, Tim Gruene wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general applicability as the requirement for objects to force themselves into the disordered arrays of the liquid state is an absurd limitation. (However, I'd support funding it nevertheless.) Best regards, Navdeep --- On Fri, Apr 19, 2013 at 10:14:04AM +0100, Peter Artymiuk wrote: Another of my colleagues, Jeremy Craven, is an NMR spectroscopist and bioinformatician. He is in referee mode at present and comments: From: Jeremy Craven c.j.cra...@sheffield.ac.uk Date: 19 April 2013 10:05:18 GMT+01:00 To: Peter Artymiuk p.artym...@sheffield.ac.uk Subject: Re: Fwd: popular piece on X-ray crystallography I suspect this technique will have little general applicability as the requirement for objects to force themselves into ordered arrays is an absurd limitation. I would not support funding it. Jeremy I fear he may be right best wishes Pet On 19 Apr 2013, at 09:53, David Briggs wrote: Following on from that - readers may be interested in Stephen Curry's post in the Guardian, regarding the Crystallography exhibit at the London Science Museum. http://www.guardian.co.uk/science/occams-corner/2013/apr/19/1 regards, Dave
Re: [ccp4bb] popular piece on X-ray crystallography
It was the observation that atoms have size. Rutherford's alpha-particle experiment had shown that the nucleus was incredibly small, very much smaller than the distances between atoms, bringing about the solar system idea, which right away came into question because such atoms would produce synchrotron radiation and the electrons would rapidly decay from their orbits. So, every nanosecond that the universe has not tuned itself into powdered neutronium is evidence against electrons in orbit. I think it was Laue who then proposed that the electrons must be bound very close to the nucleus (somehow). Making the atoms very sharp points, and separated from each other by vast distances (relative to their size). However, if the electrons really were confined to very sharp points, then the x-ray diffracted intensities from things like perfect rock salt crystals would not fall off with increasing sin(theta)/lambda. They would be relatively constant (much like the scattering profile of Rutherford's experiment). This was explained away as thermal vibrations blurring the atomic positions, making them look like they have size, and causing the spots to fade with increasing resolution. What Debye showed was that the temperature-dependence of this falloff was insufficient to give the atoms zero size, even when extrapolated to absolute zero (yes, they had liquid air in 1914), and this residual size was still comparable to bond lengths. That meant the electrons really were distributed in a cloud very far from the nucleus, and apparently not falling in. The only explanation is that the electron must be de-localised. And that is a quantum effect. I always thought that the paper Debye (1914) Ann. Phys. 348, 49-92 is perhaps one of the most remarkable in all of science. It is the original reference for the B factor, the Lorentz factor, and also the paper that ended determinism. At least, that is how I understand it. I had to return my English translation of the Debye paper to the library. I'll order my own copy. -James Holton MAD Scientist On Fri, Apr 19, 2013 at 2:38 PM, colin.n...@diamond.ac.uk wrote: James In 1915, I thought Debye and Scherrer were testing for interference between the electrons in different orbits within atoms. This was in order to test the Bohr model. They got rings but they were powder diffraction rings. The method never did identify planetary type orbitals. However Debye eventually adjusted his aims and the method did become useful despite the requirement for objects to force themselves into ordered arrays Was there some other key observation Debye made in 1915 which you refer to? Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of James Holton Sent: 19 April 2013 18:27 To: ccp4bb Subject: Re: [ccp4bb] popular piece on X-ray crystallography Because there is never more than one photon in flight at any given time. Even at 1 photon/s, we still eventually get spots. Atoms also don't emit synchrotron radiation, despite there being charged particles accelerating around their little orbits in there. But yes, in 1913, people were still hoping there was another explanation for these two observations, other than that pesky quantum theory. It was in 1915 that Debye made the key observation that collapsed determinism as we knew it. I don't think he was very happy about that. Neither was Einstein. -James Holton MAD Scientist On 4/19/2013 9:43 AM, Tim Gruene wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hello Bernhard, could you explain this? A photon is the exchange particle of the electromagnetic force, i.e. as soon as you have more than two charged particles interacting there is more than one photon - why is it incorrect to use the term multi-photon process in the context of X-ray diffraction? Cheers, Tim On 04/19/2013 06:19 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: However, a reviewer could reject the method on theoretical grounds - the explanation of X-ray diffraction as a multi-photon process is not correct BR -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Peter Artymiuk Sent: Friday, April 19, 2013 7:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] popular piece on X-ray crystallography Just to clarify, Jeremy was not being serious, but imagining what an awkward / obnoxious grant reviewer might have said in 1913. But your points would be valuable in rebutting such a view Pete On 19 Apr 2013, at 11:28, Navdeep Sidhu wrote: Dear Pet, On the contrary, far as I know, nature seems to require most solids we see around us to be crystalline. And much of the rest is either gaseous or plasma. Hence, by the reasoning proposed, we are led to suspect a different conclusion: that it's studies dealing with the remaining state that have little general
