Alan Davies yes.Clinton Huxley wrote:Was this the one with the mop-topped comedian presenting?
This is my prob. I don't want some comedian presenting my science. I want someone who knows what he is talking about.leo-rcc wrote:Alan Davies yes.Clinton Huxley wrote:Was this the one with the mop-topped comedian presenting?
This is (seriously) a profound post. I reached similar conclusions in my early 20s as a result of using LSD. Probably coming at the same issue from a different perspective.FBM wrote:Nothing that erodes the certainty...including mathematical...that reality is a certain way? That if we just find the right formula, the right expression, we'll know reality for sure? Am I wrong in thinking that we all, practically speaking, behave as if there were something certain underlying our reasons for doing what we do? For me, that program added fuel to something I've been thinking about for a while now: that no one has yet found a solid foundation upon which to base our everyday assumptions that what we experience is in any way ultimately real. Representational realism is dead to me. I can't find anything other than convention based on history, tradition and unfounded assumptions. Reality is becoming more and more nebulous the more I investigate it, and that program only gave me more reason to doubt that certainty is even possible. Gödel, for instance.
A brief history of time would be a good starting point.Xamonas Chegwé wrote:I was extremely interested in the quantum mechanics as it applied to photosynthesis that was mentioned in the program. I want to know more about that. In fact, I want to know more about QM in general. Can anyone recommend a good book on the subject - aimed at a beginner with a pretty decent grounding in science - ie. a little above the pop-sci level?
Gawd wrote:»
And those Zumwalts are already useless, they can be taken out with an ICBM.
In some aspects, I'm rediscovering what I 'saw' in my 20s (Yes, LSD and some other things were sometimes involved, but mostly it was investigation into science and philosophy). In other aspects, I'm finding fresher and more profound discoveries and admissions in science that, fundamentally, we don't really know much, if anything, about anything with any certainty. I think Pyrrho was spot on in his approach to the problem.Rumertron wrote:This is (seriously) a profound post. I reached similar conclusions in my early 20s as a result of using LSD. Probably coming at the same issue from a different perspective.
'Reality' is even less than relative I suspect. It is profoundly subjective and arises from a billion consciousnesses reaching out to a world which does not exist in any meaningful objective way and trying to deal with it. The world is a rendered phantasm and it is a wonder it works as it does for most of us. It is truly a profound mystery.
Read it. I was looking for something quite a bit meatier. As I said, not pop-sci. And something specifically concentrating on QM as opposed to physics and cosmology in general.DP wrote:A brief history of time would be a good starting point.Xamonas Chegwé wrote:I was extremely interested in the quantum mechanics as it applied to photosynthesis that was mentioned in the program. I want to know more about that. In fact, I want to know more about QM in general. Can anyone recommend a good book on the subject - aimed at a beginner with a pretty decent grounding in science - ie. a little above the pop-sci level?
Books? We don' need no stinkin' books! We've got teh interweebs! See if you can wrap your head around this jewel, I can't:Xamonas Chegwé wrote:Read it. I was looking for something quite a bit meatier. As I said, not pop-sci. And something specifically concentrating on QM as opposed to physics and cosmology in general.
What I was hoping for was more the kind of book that someone studying a degree course in physics would be recommended for their first year QM primer. I have a knowledge of physics to A level standard and maths to undergraduate level, so I don't need the sums glossing over!
Any suggestions? Perhaps I should ask at RD.
Deepening the quantum mysteries
The "central mystery" of quantum physics just got more mysterious. Experimenters from the United States and Austria have got together to provide a new demonstration of how light going through a "double slit" experiment seems to know before it sets out in its journey exactly what kind of traps have been set for it along the way.
This is a variation on the Young's slit experiment, familiar from school laboratory demonstrations of the wave nature of light. When a beam of monochromatic light is shone through two narrow holes in a screen, the light spreading out from the two holes interferes, just like ripples interfering on the surface of a pond, to produce a characteristic pattern on a second screen.
The mystery is that light can also be described as a stream of particles, called photons. The light source in a Young's slit experiment can be turned down to the point where it consists of individual photons going through the experiment, one after the other. If the spots of light made by individual photons arriving at the second screen (actually a photoelectric detector) are added together, they still form an interference pattern, as if each photon goes through both holes and interferes with itself on the way through the experiment. It was Richard Feynman who described this as "the central mystery" of quantum theory, and then corrected himself, saying that in fact it is "the only mystery". If you understood this, you would understand quantum physics -- but as Feynman also said, "nobody understands quantum mechanics" (The Character of Physical Law, BBC Publications, 1965).
The new demonstration of how incomprehensible the quantum world is has been made by Raymond Chiao, of the University of California, Berkeley, Paul Kwiat, of the University of Innsbruck, and Aephraim Steinberg, of the US National Institute of Standards and Technology, in Maryland. Their results were presented at a meeting in Nathiagali, Pakistan.
In fact, the team has carried out several tests of the stranger predictions of quantum theory, but the most dramatic is what they call the "quantum eraser". In this variation on the Young's slit theme, the experiment is first set up in the usual way, and run to produce interference. Quantum theory says that the reason why interference can occur, even if light is a stream of photons, is that there is no way to find out, even in principle, which photon went through which slit. The "indeterminacy" allows fringes to appear.
But then Chiao and his colleagues ran the same experiment with polarising filters in front of each of the two slits. Any photon going one way would become "labelled" with left-handed circular polarization, while any photon going through the other slit is labelled with right-handed circular polarization. In this version of the experiment, it is possible in principle to tell which slit any particular photon arriving at the second screen went through. Sure enough, the interference pattern vanishes -- even though nobody ever actually looks to see which photon went through which slit.
Now comes the new trick -- the eraser. A third polarising filter is placed between the two slits and the second screen, to scramble up (or erase) the information about which photon went through which hole. Now, once again, it is impossible to tell which path any particular photon arriving at the second screen took through the experiment. And, sure enough, the interference pattern reappears!
The strange thing is that interference depends on "single photons" going through both slits "at once", but undetected. So how does a single photon arriving at the first screen know how it ought to behave in order to match the presence or absence of the erasing filter on the other side of the slits?
All of these experiments were carried out using beams of individual photons, and there is no way in which the results can be explained by using classical physics. They lay bare the mysteriousness of quantum mechanics in all its glory, and in particular demonstrate its "non local" nature -- the way in which a photon starting out on its journey behaves in a different way for each experimental setup, as if it knew in advance what kind of experiment it was about to go through.
Don't worry if you don't understand this. Richard Feynman didn't, and he warned "do not keep saying to yourself, if you can possibly avoid it, 'But how can it be like that?' because you will go 'down the drain' into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that."
Yes. This is the sort of thing I love about QM! The complete bizzarity of it all. particles that are also waves and know what they have to do to get through any obstacles before they are in place! What i want to read is a book that explains the current theorising behind these insane experiments.FBM wrote:Books? We don' need no stinkin' books! We've got teh interweebs! See if you can wrap your head around this jewel, I can't:Xamonas Chegwé wrote:Read it. I was looking for something quite a bit meatier. As I said, not pop-sci. And something specifically concentrating on QM as opposed to physics and cosmology in general.
What I was hoping for was more the kind of book that someone studying a degree course in physics would be recommended for their first year QM primer. I have a knowledge of physics to A level standard and maths to undergraduate level, so I don't need the sums glossing over!
Any suggestions? Perhaps I should ask at RD.
From: http://www.lifesci.sussex.ac.uk/home/Jo ... uantum.htm
Deepening the quantum mysteries
The "central mystery" of quantum physics just got more mysterious. Experimenters from the United States and Austria have got together to provide a new demonstration of how light going through a "double slit" experiment seems to know before it sets out in its journey exactly what kind of traps have been set for it along the way.
This is a variation on the Young's slit experiment, familiar from school laboratory demonstrations of the wave nature of light. When a beam of monochromatic light is shone through two narrow holes in a screen, the light spreading out from the two holes interferes, just like ripples interfering on the surface of a pond, to produce a characteristic pattern on a second screen.
The mystery is that light can also be described as a stream of particles, called photons. The light source in a Young's slit experiment can be turned down to the point where it consists of individual photons going through the experiment, one after the other. If the spots of light made by individual photons arriving at the second screen (actually a photoelectric detector) are added together, they still form an interference pattern, as if each photon goes through both holes and interferes with itself on the way through the experiment. It was Richard Feynman who described this as "the central mystery" of quantum theory, and then corrected himself, saying that in fact it is "the only mystery". If you understood this, you would understand quantum physics -- but as Feynman also said, "nobody understands quantum mechanics" (The Character of Physical Law, BBC Publications, 1965).
The new demonstration of how incomprehensible the quantum world is has been made by Raymond Chiao, of the University of California, Berkeley, Paul Kwiat, of the University of Innsbruck, and Aephraim Steinberg, of the US National Institute of Standards and Technology, in Maryland. Their results were presented at a meeting in Nathiagali, Pakistan.
In fact, the team has carried out several tests of the stranger predictions of quantum theory, but the most dramatic is what they call the "quantum eraser". In this variation on the Young's slit theme, the experiment is first set up in the usual way, and run to produce interference. Quantum theory says that the reason why interference can occur, even if light is a stream of photons, is that there is no way to find out, even in principle, which photon went through which slit. The "indeterminacy" allows fringes to appear.
But then Chiao and his colleagues ran the same experiment with polarising filters in front of each of the two slits. Any photon going one way would become "labelled" with left-handed circular polarization, while any photon going through the other slit is labelled with right-handed circular polarization. In this version of the experiment, it is possible in principle to tell which slit any particular photon arriving at the second screen went through. Sure enough, the interference pattern vanishes -- even though nobody ever actually looks to see which photon went through which slit.
Now comes the new trick -- the eraser. A third polarising filter is placed between the two slits and the second screen, to scramble up (or erase) the information about which photon went through which hole. Now, once again, it is impossible to tell which path any particular photon arriving at the second screen took through the experiment. And, sure enough, the interference pattern reappears!
The strange thing is that interference depends on "single photons" going through both slits "at once", but undetected. So how does a single photon arriving at the first screen know how it ought to behave in order to match the presence or absence of the erasing filter on the other side of the slits?
All of these experiments were carried out using beams of individual photons, and there is no way in which the results can be explained by using classical physics. They lay bare the mysteriousness of quantum mechanics in all its glory, and in particular demonstrate its "non local" nature -- the way in which a photon starting out on its journey behaves in a different way for each experimental setup, as if it knew in advance what kind of experiment it was about to go through.
Don't worry if you don't understand this. Richard Feynman didn't, and he warned "do not keep saying to yourself, if you can possibly avoid it, 'But how can it be like that?' because you will go 'down the drain' into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that."
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