Light energy is certainly quantized; see Einstein, 1905. Monochromatic light is made up of a measurable number of packets, each an indivisible amount of energy. Attenuation and partial reflection don't change the energy or the wavelength of these bundles, so we may as well call them photons. Their *location* is different; one photon is sort of all over the place until it's detected.
Photons are extremely considerate: they are particles when you want them to be, and they are waves when you want them to be. Who can gripe about something so helpful?
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Yeah, but I can clearly tell the difference between noise, or phosphenes, or graininess, or whatever I'd get with low level visibility, and a tiger. That's what brains are for. Brains are excellent pattern matching machines. Easy to tell if it's a false positive, sit and wait and see if the pattern changes over time. Move your head to see if it follows the field of view ("stuck pixels", or more likely with biological sight, dead spots). If you're a concerned prey item, you'll probably be watching intently anyway to see if it moves. And if it moves, one way or another, you're going to be running your ass off. Better to be able to tell if it's anything at all, let alone if it's moving.
Something that may've been forgotten: biology does an edge detect (spacial and temporal derivative) in the eye, then reconstructs the image later. This works well for spotting sharp changes, and it works particularly well for tracking motion. Every time a photon appears, the derivative with respect to time and space results in a magnified blotch of change, which worsens the noise at high frequencies -- in essence, it goes from white noise to blue noise. But again, these components are easily filtered by biological processes (integration) or simply concentrating on them (same idea, higher level).
More pertinent comparisons might include birds. Do any birds ever hunt at night? Birds are renouned for their excellent eyesight, several times sharper than humans', and color is definitely a requirement, but if they also have poor night vision, that would be another part of the story. There are a number of oceanic species with large eyes, the largest being the giant squid's. Size is mainly for receiving any light at all (equivalent to the Super Kamiokande's array of PMTs); I don't know if anyone has studied its resolution.
Certainly, structures like the reflective retinal layer worsen resolution, so there is necessarily some tradeoff in ability. Large eyes also take up more space (the human head shields its moderate sized eyes within orbits of bone, big eyes would require huge caveman brows and cheekbones to maintain cover).
Tim
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As I remember it, edge detection is a product of motion detection, rather than the other way around. Our eyes vibrate slightly so that, combined with motion detection, edges are highlighted.
That's just from old reading about neural nets, so it's not directly from biology texts.
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On a sunny day (Thu, 03 May 2012 15:44:05 -0700) it happened John Larkin wrote in :
No. little EM wave disturbances when an electron changes orbit can best be seen as ripples in a pond where a stone is dropped.
You will notice the ripples move in all (now 2 D) directions. Of course the pressure wave moves in ALL directions. A lower amplitude than is possible when 'light' (EM wave) is generated in a different way. Not even to mention the superposition of all the stuff.
Just an idea, would moving a quark create an EM disturbance? LOL
In short, all effects seen can be explained from the wave perspective, including the photo-electric effect. Not all effects seen can be explained from the particle perspective, you get a crazy picture that way.
This Einstein fella has caused more confusion than he ever solved. And people keep parroting that, thinking it makes them look 'learned'. I prefer the term 'brain dead', voila[1] our education system.
Edge detection in the eye doesn't require motion. Receptors have inhibitory connections on their neighbors ("inhibitory surrounds"). This increases contrast, so the edges stand out.
What you may be thinking of is that if the image on the retina is stationary, it fades away due to adaptation of the receptors and their subsequent neurons... they are essentially "AC coupled".
As far as I know, all sensory systems and most neurons in general respond more strongly to stimulus onset, then adapt to a lower firing level as the stimulus continues, or stop completely. Some neurons also have a burst of offset activity as well.
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PS Our 'wave detector' is very crude. It basically consists of a rubber ball[1] glued to a piece of concrete[2], embedded in the water, where the waves from the stone's entry travel.
When the wave amplitude at the point of the ball is so big that the glue breaks, we catch the ball and cry: "A PHOTON IS DETECTED".
Even to the complete imbeciles it must be clear that the quantization observed this way depends 100% on the detector (glue strength, etc), not on the wave. [1] electron [2] nucleus
I have no quibble with the idea that light *can* be quantized, but I wonder whether it *must* be quantized. All of our common techniques for measuring light, and most of those for emitting it, depend upon exciting electrons, so we can expect the measurements to be quantized simply because electron energy levels are quantized.
But for EM radiation in general, as far as I can tell, all that is needed is accelerating charge. I confess that I'm not smart enough to follow the math of synchrotron radiation, but I imagine that a whirling charge doesn't say to itself "Ooh, time to throw off a blue photon... no, wait, I just did that... better make it green this time".
All of the "photon" discussions seem to fizzle as we get down to radio frequencies. I understand that some folks claim that microwaves are quantized, but as far as I can tell they use resonant cavities in their tests. But lower down, I don't recall ever hearing anybody discuss how a continuous sinusoidal motion of electrons in an antenna can give rise to discrete photons of RF. Where does one end and the next begin? Instead we get hand-waving and mumbling about "wave-particle duality", except I've never heard a "particle" side to RF.
But I'd love to hear the explanation!
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I think it has to be "turtles all the way down". You can't have quantized E&M (photons) at optical wavlengths and then say, "but not at RF".
So here's a system where there are quantized energy states in the RF region. (I'm sure there are others.)
If you look at a magnetic moment (spin of the electron or nucleus) in a magnetic field, you will find that quantum mechanically the projection of the magnetic moment along the magnetic field direction is quantized. It can only have certain values. Furthermore to change from one state to the other (flip the spin for the case of a free electron.) you need 'exactly' the right frequency of magnetic dipole radiation. I will sometimes speak of an RF photon causing the spin to change state. I don't think there is anything fundamentally wrong with this statement. I guess you should always remember that all of science is just a model for how nature works. There's nothing saying that the model is what=92s really going on.
But photons move in one direction. That's why you have a shadow.
A gamma ray looks more like a particle than a wave. But all photons are the same, just different energy levels. It's just more obvious with gammas.
He said a lot of new and radical stuff, and 100% has been right. He regretted proposing the Cosmological Constant, but even that turned out to be right.
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John Larkin Highland Technology, Inc
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Bad analogy. The rest of the water wave is still sloshing around the pond after part of it breaks your glue. Some of it even reflects off your detector. With a photon, once it's detected, all of it is gone, everywhere. Even though its extent was miles (as interferance requires it to be) it collapses instantly, and deposits 100% of its energy, into the detector. Your pond ripples don't do that; they are divisible and not quanta.
Face it: there is no humanly comprehensible explanation of quantum mechanics.
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John Larkin Highland Technology, Inc
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Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
On a sunny day (Fri, 04 May 2012 11:34:11 -0700) it happened John Larkin wrote in :
A 'photon' is just a mathematical construct: p=h.v when h is Planck' constant, and v the frequency.
He tried to replace understanding with a simple formula. Physics has been stuck with it ever since, putting the breaks on any advancement.
Math is just an engineering tool, to get quantities. understanding is possibly a construct in the human neural net that encompasses much more.
The wormhole - , singularity - , and string fruitcakes are products of silly applications (say wrong applications or applications to phantasy) of math, without ANY understanding. For example any idiot knows everything has it limits, but mathematicians playing Einstein's formulas gladly arrive at singularities, and those sell bigtime in the world of phantasy, Hollywood makes lots of money with their crap, just too bad when you ask for the wormhole travel ticket then they shy away, Its the sickness of this time, : math - Einstein - CERN, ITER, LIGO. Shortage of resources will fix that, I am very happy the gravity wave spacecraft was ditched I heard today and replaced by a mission to the Jupiter moons. NASA pulled out (no money) and Europe decided to only go to Jupiter. Now that is interesting looking for life. LIGO (the gravity wave detector) has had updates to improve its sensitivity by orders of magnitudes, and still sees nothing, so much for Einstein's phantasy world. Either that or they cannot even do basic math, as it should have shown a signal years ago WITHOUT the sensitivity updates. HAHAHA Einstein should never have gotten a Nobel for 'photon', and some should not have gotten a Nobel piece price, its all politics, and it destroys or puts the break on any scientific advancement. Why do you think US cannot go to moon anymore, and now mars, but only drive around the block using a Russian taxi? Politics. Peer review? Like in global warming? HAHAHA Imagine a whole lot of Slow Mans with an agenda so thick that the trees cut to make the paper for it heat the earth to the points of stone melting into lava. Harvard (IIRC) just made the announcement that they will no longer subscribe to the 'peer reviewed' journals, because they say 'We do the research and make it available for free, and then need to buy it back from the journals (that do the peer reviews'. Now there is 2012, and it probably will get worse.
I promptly verified your observations with my own. I have not tried to measure frequency of the pulses, but I agree that they are a function light. However, there is a much stronger correlation to the applied reverse voltage. There is a voltage which brings on these pulses even in total darkness. Maybe it is counting cosmic rays that get through.
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