Photons as bullets at 10 trillion FPS (frames per second)

[EPR]

The following extraordinary experiment from Caltech highlights the 'classical' behaviour of light(photons) traveling through medium. It vindicates the notion that photons(at least from our limiting human perspective) do behave the same way as other quanta(much like ordinary 'matter' - chairs, cars, cups and walls) in the presence of measuring equipment. Nice to see the relationship between theory and practice in a previously unexplored domain(C). Between fields and 'objects'.
And viewing photons as bullets.

 

[phinds]

It vindicates the notion that photons(at least from our limiting human perspective) do behave the same way as other quanta(much like ordinary 'matter' - chairs, cars, cups and walls) in the presence of measuring equipment.

Not too exciting since Einstein showed this in 1905. The thing to keep in mind is that this does NOT mean that they are "particles" in the classical sense of that term. They are quantum objects and will indeed exhibit particle-like behavior if you measure for that. They will also exhibit wave-like behavior if you measure for that.

 

[George Jones]

The following extraordinary experiment from Caltech highlights the 'classical' behaviour of light(photons) traveling through medium. It vindicates the notion that photons(at least from our limiting human perspective) do behave the same way as other quanta(much like ordinary 'matter' - chairs, cars, cups and walls) in the presence of measuring equipment. Nice to see the relationship between theory and practice in a previously unexplored domain(C). Between fields and 'objects'.
And viewing photons as bullets.

Actually, photons are not at all like bullets or other classical objects. Photons are localized quanta in momentum space, not in physical position space.

This means that a quantum of light (a photon) has a sharp value of momentum (and thus energy), not a sharp value of position. A photon is completely delocalized in position space. Roughly, think uncertainty principle.

The right superposition of light quanta (phtotons) can result in light pulses that have some of the properties of classical objects.

 

[hutchphd]

So these are pictures not of "photons" but of "photon torpedoes" ?...

 

[Aidyan]

I don't think one is seeing 'photons' here anyway. Also the pulse bouncing in the cavity is is already a macroscopic wavefront made presumably of trillions of photons, many of which must be scattered by the medium, otherwise one wouldn't see anything. From the physics there isn't much news here, but what I found interesting is how it resembles Finite-Difference-Time-Domain (FDTD) numerical simulations that employ classical Maxwell's equations for light propagation in optical media (no quantum physics involved).

 

[hutchphd]

I find the concept of " not seeing photons" to be problematic. What, in fact, are we "seeing"?

 

[phinds]

I find the concept of " not seeing photons" to be problematic. What, in fact, are we "seeing"?

You are seeing photons, but not the ones traveling through the medium, rather the ones that are reflected off of the medium and directed to the camera.

If you want to get REALLY technical, you are seeing photons created by a computer (or phone) screen which were created from an image of the photons reflected off of the medium through which the laser pulse was traveling.

 

[hutchphd]

Actually it is more remote than that because the camera technique involves tomography using what are essentially streak images as I understand it.
Your point is well said but my problem is more doctrinal.
It just seems to me the statement "you are not seeing photons" is equivalent to saying "I am not eating a cow" while devouring a cheeseburger. It is both true and not true and I grow weary of the polemical.

 

[phinds]

Actually it is more remote than that because the camera technique involves tomography using what are essentially streak images as I understand it.
Your point is well said but my problem is more doctrinal.
It just seems to me the statement "you are not seeing photons" is equivalent to saying "I am not eating a cow" while devouring a cheeseburger. It is both true and not true and I grow weary of the polemical.

ALL "seeing" for humans is the impinging of photons on the retina, so I understand your point but I disagree that it is polemical. The point is that you are not seeing the photons that move through the medium.

 

[hutchphd]

But this is true if I say "I see the baseball". Really by this definition I guess you should say "I see the milky substrate in the phial" (but not for very long!)

 

[Aidyan]

It just seems to me the statement "you are not seeing photons" is equivalent to saying "I am not eating a cow" while devouring a cheeseburger. It is both true and not true and I grow weary of the polemical.

I think the problem is only that of nomenclature and the precise meaning of words. In a certain sense "seeing photons" is an everyday experience. Just look at an object that reflects light, turn on the light, look at the sun, etc., then you are "seeing photons". But, if by the term 'photon' we indicate a light particle, a single corpuscle flying around, then this experiment does not at all show that. You don't "see a photon" here, like one does not see H2O molecules looking at a water wave. We can only say that one sees an electromagnetic perturbation that is propagating throughout an optical medium. But to describe what is seen one does not need any reference to particles, photons or quantum mechanics, it is just good old classical electromagnetism.

 

[timmdeeg]

then you are "seeing photons".

Not really, this reasoning is due to a photochemical reaction in the retina. If you see a thing you get an impression about it but you can't get an impression about a photon itself.

 

[phinds]

Not really, this reasoning is due to a photochemical reaction in the retina. If you see a thing you get an impression about it but you can't get an impression about a photon itself.

That's getting too far down into the weeds.

 

[phinds]

But this is true if I say "I see the baseball". Really by this definition I guess you should say "I see the milky substrate in the phial" (but not for very long!)

But the surface of the baseball is not made of photons so your analogy is false. This thread is talking about photons moving through a medium and whether you can see THEM or not.

 

[hutchphd]

As I said you are "seeing" the medium by the usual definition so I was agreeing with you.
I guess my attempt to be polemical about folks being polemical was not well received...