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Author Topic: Is light stranger than we think?  (Read 2143 times)

Offline jeffreyH

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Is light stranger than we think?
« on: 09/11/2014 16:29:09 »
Consider the earth being at distance x from a particular star. The value x then becomes the radius of a sphere round the star. If we start at any point on the surface of this sphere and move 1 planck length at a time around a great circle on the sphere would we always be able to see the star at any point on the circle? The luminosity should be the same according to Lambert's cosine law and yet this indicates that a number of photons reach us at any point at a constant rate. What does this tell us about the distribution of photons in the field when considering the inverse square nature of the field?


 

Offline chiralSPO

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Re: Is light stranger than we think?
« Reply #1 on: 09/11/2014 17:37:04 »
I don't see any contradictions in here... There are so many photons coming out of the sun that even at a distance of one AU, there is a substantial flux of photons. The cross-section of interaction with a visible photons is much greater than one Planck length, so subdividing the space into these really tiny fragments isn't that meaningful. It's like shooting an animal with a single bullet and wondering which cell got hit, and how the neighboring cell could be hit too.

Lambert's law also is angle specific in a way that you did not describe well. Moving around the circle while looking directly at the Sun doesn't change the angle that the law refers to. The angle refers to how directly one is looking at the luminous object.
« Last Edit: 09/11/2014 17:40:50 by chiralSPO »
 

Offline chiralSPO

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Re: Is light stranger than we think?
« Reply #2 on: 09/11/2014 18:29:16 »
That said, light probably IS stranger than we think!
 

Offline evan_au

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Re: Is light stranger than we think?
« Reply #3 on: 09/11/2014 18:34:16 »
If you are talking about Planck Lengths, then maybe you should be talking about Planck Time, too?

The number of photons striking your camera's detector in one Planck time unit is radically different in different locations (or in the same location, but in different seconds).

On these timescales, the number of photons is mostly 0, and sometimes 1.
 

Offline jeffreyH

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Re: Is light stranger than we think?
« Reply #4 on: 09/11/2014 18:48:38 »
If you are talking about Planck Lengths, then maybe you should be talking about Planck Time, too?

The number of photons striking your camera's detector in one Planck time unit is radically different in different locations (or in the same location, but in different seconds).

On these timescales, the number of photons is mostly 0, and sometimes 1.

Touche Evan! I had not stated timescales so that is a very good point. I had not even thought of it in those terms.
 

Offline jeffreyH

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Re: Is light stranger than we think?
« Reply #5 on: 09/11/2014 18:55:00 »
I don't see any contradictions in here... There are so many photons coming out of the sun that even at a distance of one AU, there is a substantial flux of photons. The cross-section of interaction with a visible photons is much greater than one Planck length, so subdividing the space into these really tiny fragments isn't that meaningful. It's like shooting an animal with a single bullet and wondering which cell got hit, and how the neighboring cell could be hit too.

Lambert's law also is angle specific in a way that you did not describe well. Moving around the circle while looking directly at the Sun doesn't change the angle that the law refers to. The angle refers to how directly one is looking at the luminous object.

some photons will be coming at us from one side of the star while others from the opposite side all around the outer circle described by the stars profile. So there are angles involved. If you plot radial distributions over vast distances the separation between individual photons becomes immense. Shouldn't there occasionally be a blind spot where the star appears to disappear? Or at least get much fainter. It is as if there will always be a precise amount of photons at any point even with an incoherent field.
 

Offline evan_au

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Re: Is light stranger than we think?
« Reply #6 on: 10/11/2014 10:31:59 »
Quote from: jeffreyH
a precise amount of photons
Like all quantum phenomenon, the timing, location and direction of a photon can only be described with a probability distribution.

It only becomes "precise" when you average over many, many photons, and that's because all the statistical fluctuations average out, in the long term.

In the short term, it is totally imprecise, because you cannot tell with certainty if your 1 photon at position X comes from one probability distribution or a different one (but you might be able to guess).
 

Offline JohnDuffield

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Re: Is light stranger than we think?
« Reply #7 on: 10/11/2014 13:25:00 »
I don't think light is stranger than we think. Instead, what I think is strange is that people think of photons as little billiard-ball things, even though they know that E=hc/λ applies. The photon is a wave. Think in terms of a seismic wave and things like "many paths" aren't strange at all.
 

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Re: Is light stranger than we think?
« Reply #7 on: 10/11/2014 13:25:00 »

 

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