What is Light?

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BDanielMayfield
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Re: What is Light?

Post by BDanielMayfield » Fri Jan 30, 2015 12:28 am

MargaritaMc wrote:By chance, I've just come across this article in a December 2014 issue of a Science Daily
Quantum physics just got less complicated: Wave-particle duality and quantum uncertainty are same thing

It's tangentially related to this discussion. Maybe. Interesting, anyway.

M
No maybe so about it. It was helpful. Thanks Margarita and bystander.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: What is Light?

Post by MargaritaMc » Fri Jan 30, 2015 12:04 pm

BDanielMayfield wrote:
No maybe so about it. It was helpful. Thanks Margarita and bystander.
Glad it was helpful, Bruce. This article in last September's Science News,
New analysis rescues quantum wave-particle duality also interested me - tho I admit to understanding only about one half of it.

This is the paper it refers to:
PNAS, vol. 111 no. 34
A "fair sampling" perspective on an apparent violation of duality
Eliot Bolduc, Jonathan Leach, Filippo M. Miatto, Gerd Leuchs, Robert W. Boyd

http://pnas.org/content/111/34/12337

http://arxiv.org/abs/1402.6487

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Re: What is Light?

Post by Ron-Astro Pharmacist » Fri Jan 30, 2015 8:43 pm

The dimensions we have access to- length, high and width- all are accessible with time being fleeting but sensible actor. The forces and force carriers move amongst those dimensions. I have always being nagged (probably posting it many times before) that size itself could be a dimension. I think if heard an argument that the next dimension would be at a right angle to all of the other three. So if the other forces seem to flow along in a specific direction or vector, would we sense one which flowed along a dimension we cannot fully experience?

Directionality of Forces
Electricity – negative to positive
Magnetic – pole to pole
Strong – Proton to neutron, quark to quark
Weak – Acting on left-handed particles only

A flow from small to large could hypothetically explain the effects of that dimension with its unique force we've yet to grasp (time itself?). As an example, a photon propagating along the" size" dimension might not be directly detectible only leaving a remnant wave telling of its existence. Its constant speed could reflect that flow. Going light-years out on a limb, it would be interesting to speculate the all the known forces move along their own dimension with the small to large imparting direction. Going even further out the limb (I should leave this alone) - our universe is the result of those interactions. As another example – entropy seems to be a force hard to explain in its un-directionality. What causes Brownian motion or triboluminescence anyways?

You all know I like to speculate a lot so please forgive me this particular dalliance. I get baffled by that which is un-explicable by my own means and my making sense of it seems to flow in your direction. This internet place is a dimension of its own.
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Re: What is Light?

Post by BDanielMayfield » Sat Jan 31, 2015 4:49 pm

Ron-Astro Pharmacist wrote:The dimensions we have access to- length, high and width- all are accessible with time being fleeting but sensible actor. The forces and force carriers move amongst those dimensions. I have always being nagged (probably posting it many times before) that size itself could be a dimension. I think if heard an argument that the next dimension would be at a right angle to all of the other three. So if the other forces seem to flow along in a specific direction or vector, would we sense one which flowed along a dimension we cannot fully experience?

Directionality of Forces
Electricity – negative to positive
Magnetic – pole to pole
Strong – Proton to neutron, quark to quark
Weak – Acting on left-handed particles only

A flow from small to large could hypothetically explain the effects of that dimension with its unique force we've yet to grasp (time itself?). As an example, a photon propagating along the" size" dimension might not be directly detectible only leaving a remnant wave telling of its existence. Its constant speed could reflect that flow. Going light-years out on a limb, it would be interesting to speculate the all the known forces move along their own dimension with the small to large imparting direction. Going even further out the limb (I should leave this alone) - our universe is the result of those interactions. As another example – entropy seems to be a force hard to explain in its un-directionality. What causes Brownian motion or triboluminescence anyways?

You all know I like to speculate a lot so please forgive me this particular dalliance. I get baffled by that which is un-explicable by my own means and my making sense of it seems to flow in your direction. This internet place is a dimension of its own.
I think you may be adding to your own confusion by mixing things up a bit Ron. I like your motto, "let there be explicable light", but the ideas you've expressed here just murk things up, IMO.

For example, you wrote, "size itself could be a dimension." I don't want to give ofence, but that makes no sence whatsoever. Size is not a dimension, it is just a means of meassuring/comparing the extent of things along the three spacial dimensions.

Brownian motion is, as Chris would no doubt say, "perfectly understood". Particles bouncing off each other due to kinetic energy which is supplied by the substance's thermal state. Cool it enough and all such motion will cease. Triboluminescence is defined as "luminescence due to friction". Where's the mystery in either of these phenomena?
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Re: What is Light?

Post by Nitpicker » Sun Feb 01, 2015 5:05 am

Dimensions are defined as they are needed, in order to perceive one's reality to one's satisfaction. I once needed to develop a non-linear interpolation algorithm within a five-dimensional database. None of the dimensions were spatial, but I needed them all, just to determine the change in pressure across different urban stormwater structures in flood.

If your model needs a "size" dimension, then define it. The real test is if the model is judged to be fit for purpose.

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Re: What is Light?

Post by Markus Schwarz » Mon Feb 02, 2015 8:50 am

Ron-Astro Pharmacist wrote:The dimensions we have access to- length, high and width- all are accessible with time being fleeting but sensible actor. The forces and force carriers move amongst those dimensions. I have always being nagged (probably posting it many times before) that size itself could be a dimension. I think if heard an argument that the next dimension would be at a right angle to all of the other three. So if the other forces seem to flow along in a specific direction or vector, would we sense one which flowed along a dimension we cannot fully experience?
[...]
You all know I like to speculate a lot so please forgive me this particular dalliance. I get baffled by that which is un-explicable by my own means and my making sense of it seems to flow in your direction. This internet place is a dimension of its own.
Our universe has three spatial dimensions and one temporal. There are theories that investigate universes with more spatial or temporal dimensions. One idea used to be that gravity could travel through these higher dimensions, while the remaining forces and particles cannot, thus "explaining" the weakness of gravity compared to the other forces. But these theories are highly speculative and lead to hardly any predictions (if any at all).

And as Nitpicker mentioned, dimension is a mathematical term, which roughly means how many numbers you need to uniquely define an event. As a rough example, for an appointment you might need the city (ZIP code), street, house number, floor number, office number and the date. This makes your appointment a 5+1 dimensional object. Since our universe has 3+1 dimension, the minimal information you need to specify your appointment are three spatial coordinates (like longitude, latitude and elevation above sea level) and the time.

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Re: What is Light?

Post by Ron-Astro Pharmacist » Thu Feb 05, 2015 6:33 pm

Thank you for all your comments. Our universe has so many mysteries it's easy to whimsically wish to think outside all known boxes. It's not likely a non-professional is going to foster some idea for a new direction of investigation. I appreciate the forum too much to do this often but when something gets a foothold in one's brain, often it’s the only way to relief the pressure of "wondering if anyone else has ever thought of this before" by asking those who have the background to critic the thought. Thanks again for your time and insight. Believe me – I'm often embarrassed by my own strange thoughts after I decide to hit the "submit" key. Luckily I manage to get over it and, unfortunately, will likely spew out a few more as I attempt to get the best understanding of our universe that I can manage. :) Ron
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Re: What is Light?

Post by jmh » Mon Feb 16, 2015 3:21 pm

Hi gang, just joined to board but for a few years have loved the images APOD has been providing!

J found this thread interesting -- even if mostly over my head in most ways. I have a couple of questions questions about the link (the Uncertainty/Duality equivalence) that I suspect somene here can answer so the uneducated (that would be me :lol2: ) can grasp the basic idea.
"The connection between uncertainty and wave-particle duality comes out very naturally when you consider them as questions about what information you can gain about a system. Our result highlights the power of thinking about physics from the perspective of information," says Wehner
I'm trying to figure out is there's something deeper in that statement that I can make sense of. Is this simply a statement about what information we can extract from oberservations or is it saying something along the lines of looking at the world as if it were pure information?

The other question is about:
Wave-particle duality is the idea that a quantum object can behave like a wave, but that the wave behaviour disappears if you try to locate the object. It's most simply seen in a double slit experiment, where single particles, electrons, say, are fired one by one at a screen containing two narrow slits. The particles pile up behind the slits not in two heaps as classical objects would, but in a stripy pattern like you'd expect for waves interfering. At least this is what happens until you sneak a look at which slit a particle goes through -- do that and the interference pattern vanishes.
I looked at a couple of other pages about the experiment but (we need an icon for "scratching my head") still at a loss on what the exeriment really did. It sounds like there must be at least 2 forms of detection/observation and many 3. Can someone help me better understand how the experiment is performed? What's setup to detect the passagee through the slits? What's setup to detect the wave pattern? Also, just to know, what's the barrier with the slits made from and does it's thickness matter? (Last question is an add-on and I don't think related to the original question but that's how my mind works I think)

TIA

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Re: What is Light?

Post by Ron-Astro Pharmacist » Fri Feb 27, 2015 9:04 pm

I just realized what I thought was a fourth dimension of size and its corresponding flow sounds a lot like the Higgs field. I have a lot to learn but I am looking forward to finishing Sean Carroll's course on "The Higgs Boson and Beyond".

http://www.thegreatcourses.com/courses/ ... eyond.html

Maybe it will help me solve my "light" dilemma? 8-)
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Re: What is Light?

Post by geckzilla » Thu Mar 12, 2015 9:00 pm

I was staring at glare reflecting off a white plate under my flower pot, studying the diffraction it pattern presented to my retina when I realized that there were many concentric rings (more than I could reasonably be expected to count individually) and that they were constricting and expanding, presumably along with the constriction and expansion of my iris as I blinked and automatically made small adjustments to this aperture. Is this an Airy pattern?
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Re: What is Light?

Post by Markus Schwarz » Fri Mar 13, 2015 2:06 pm

geckzilla wrote:I was staring at glare reflecting off a white plate under my flower pot, studying the diffraction it pattern presented to my retina when I realized that there were many concentric rings (more than I could reasonably be expected to count individually) and that they were constricting and expanding, presumably along with the constriction and expansion of my iris as I blinked and automatically made small adjustments to this aperture. Is this an Airy pattern?
I am not sure, but for what it's worth: When reading "concentric rings" I also thought of the Airy disk. But the Airy disk is produced by monochromatic wave diffracted by a hole. My guess is, that when you have white light the Airy disks for different wavelengths overlap and the interference pattern gets washed out, resulting in one spot. What could be the hole? Assuming the eye's iris (radius~5mm, green light (500nm), distance lens-retina 1cm) I get an Airy disk radius of ~0.6 micrometer, which I don't think the human eye can resolve.
Also, where the rings of a specific color, or white?

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Re: What is Light?

Post by Ron-Astro Pharmacist » Fri Mar 13, 2015 5:19 pm

geckzilla wrote:I was staring at glare reflecting off a white plate under my flower pot, studying the diffraction it pattern presented to my retina when I realized that there were many concentric rings (more than I could reasonably be expected to count individually) and that they were constricting and expanding, presumably along with the constriction and expansion of my iris as I blinked and automatically made small adjustments to this aperture. Is this an Airy pattern?
This is a crazy guess geck but your discription sounded similar when I looked at today's OPOD.

http://www.atoptics.co.uk/opod.htm
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Re: What is Light?

Post by Chris Peterson » Fri Mar 13, 2015 7:09 pm

Markus Schwarz wrote:
geckzilla wrote:I was staring at glare reflecting off a white plate under my flower pot, studying the diffraction it pattern presented to my retina when I realized that there were many concentric rings (more than I could reasonably be expected to count individually) and that they were constricting and expanding, presumably along with the constriction and expansion of my iris as I blinked and automatically made small adjustments to this aperture. Is this an Airy pattern?
I am not sure, but for what it's worth: When reading "concentric rings" I also thought of the Airy disk. But the Airy disk is produced by monochromatic wave diffracted by a hole. My guess is, that when you have white light the Airy disks for different wavelengths overlap and the interference pattern gets washed out, resulting in one spot. What could be the hole? Assuming the eye's iris (radius~5mm, green light (500nm), distance lens-retina 1cm) I get an Airy disk radius of ~0.6 micrometer, which I don't think the human eye can resolve.
A fully dilated human eye (f/2.1) produces an Airy disc (550 nm) that is 2.8 μm in diameter. A fully constricted eye (f/8.3) produces an Airy disc that is 11 μm in diameter. The foveal cone density results in a cone spacing of 2.6 μm. So the eye can easily resolve the Airy diffraction ring pattern, especially in brighter light.

Airy patterns are clearest with monochromatic light, but are recorded with white light as well, since the smearing created by the positions of the minima changing with wavelength isn't total (anybody who has ever collimated a telescope knows that you do so by observing the Airy disc of a star at high magnification). I can easily see diffraction rings looking at a green laser spot on a wall (with the ring pattern expanding and contracting with pupil size, as described by Geck. I can also see them looking a a specular Sun glint, although they are far less obvious. We should also consider the possibility that the different densities and spectral responses of cone cells may play a role in how we perceive white-light diffraction patterns.
Chris

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Re: What is Light?

Post by geckzilla » Sat Mar 14, 2015 2:04 am

Ron-Astro Pharmacist wrote:
geckzilla wrote:I was staring at glare reflecting off a white plate under my flower pot, studying the diffraction it pattern presented to my retina when I realized that there were many concentric rings (more than I could reasonably be expected to count individually) and that they were constricting and expanding, presumably along with the constriction and expansion of my iris as I blinked and automatically made small adjustments to this aperture. Is this an Airy pattern?
This is a crazy guess geck but your discription sounded similar when I looked at today's OPOD.

http://www.atoptics.co.uk/opod.htm
Yes, I can see larger circles like that if my eyelashes happen to be drooping a bit in front of my pupil. These were much smaller, though, and the changes which went along with changes in my pupil made me realize it was probably the Airy pattern. It's just cool to finally understand why it happens. Double plus: Because it was white light the airy pattern was a whole bunch of "rainbows" all in a row.
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Re: What is Light?

Post by geckzilla » Sat Mar 14, 2015 4:00 am

Chris Peterson wrote:
Markus Schwarz wrote:I am not sure, but for what it's worth: When reading "concentric rings" I also thought of the Airy disk. But the Airy disk is produced by monochromatic wave diffracted by a hole. My guess is, that when you have white light the Airy disks for different wavelengths overlap and the interference pattern gets washed out, resulting in one spot. What could be the hole? Assuming the eye's iris (radius~5mm, green light (500nm), distance lens-retina 1cm) I get an Airy disk radius of ~0.6 micrometer, which I don't think the human eye can resolve.
A fully dilated human eye (f/2.1) produces an Airy disc (550 nm) that is 2.8 μm in diameter. A fully constricted eye (f/8.3) produces an Airy disc that is 11 μm in diameter. The foveal cone density results in a cone spacing of 2.6 μm. So the eye can easily resolve the Airy diffraction ring pattern, especially in brighter light.

Airy patterns are clearest with monochromatic light, but are recorded with white light as well, since the smearing created by the positions of the minima changing with wavelength isn't total (anybody who has ever collimated a telescope knows that you do so by observing the Airy disc of a star at high magnification). I can easily see diffraction rings looking at a green laser spot on a wall (with the ring pattern expanding and contracting with pupil size, as described by Geck. I can also see them looking a a specular Sun glint, although they are far less obvious. We should also consider the possibility that the different densities and spectral responses of cone cells may play a role in how we perceive white-light diffraction patterns.
It ends up looking something like this to me, but the darker portion may be a little emphasized (in real life you might not have a nice, uniform and dark background) and I am showing only the rings and not the spiky parts.
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Re: What is Light?

Post by Chardonay » Fri May 22, 2015 12:19 am

Chris Peterson wrote:
THX1138 wrote:This is probably not the wisest of questions but i really and genuinely would like to know
Light / One single photon
Once this single photon comes in to existence it will by it's own nature start traveling at C in one direction or another
SO if one were close enough to see this single photon's light it would have to be traveling towards you? It couldn't be seen from two different directions like
What does "see this single photon's light" mean? A photon doesn't emit light. If the photon strikes a detector of some kind (such as your retina), it's energy will be observed. If it doesn't strike a detector, you have no way of knowing it even exists.
Can we not know it 'existed' by the radiation it gives off in the form of heat when it strikes a surface that is not a detector? Or am I wrong in thinking photons can be transformed to heat?

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Re: What is Light?

Post by Chris Peterson » Fri May 22, 2015 12:24 am

Chardonay wrote:Can we not know it 'existed' by the radiation it gives off in the form of heat when it strikes a surface that is not a detector? Or am I wrong in thinking photons can be transformed to heat?
What is "heat"? If you're talking radiation, the surface absorbs a photon of some energy and re-emits one of lower energy (typically IR if you're using the word "heat"). In that case, that surface essentially is the primary detector.
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Re: What is Light?

Post by geckzilla » Thu Nov 26, 2015 11:30 pm

I thought this was a nice example of Mie scattering. One might mistake the cloud as being sooty and brown, but it is just the nature of light scattering, much like a sunset.
Image
Full Moon Crossing by John Entwistle, on Flickr
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Re: What is Light?

Post by Ron-Astro Pharmacist » Tue Dec 01, 2015 3:54 pm

geckzilla wrote:I thought this was a nice example of Mie scattering. One might mistake the cloud as being sooty and brown, but it is just the nature of light scattering, much like a sunset.
Image
Full Moon Crossing by John Entwistle, on Flickr
Cool pic Geck and nice catch. Each generation has its own unique way of learning physics.
Click to play embedded YouTube video.
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