how does that photon know its walls with out being radiated?

[joshuagolden00]

from scientific american: "An excited atom in a small cavity is precisely such as antenna, albeit a microscopic one. If the cavity is small enough, the atom will be unable to radiate because the wavelength of the oscillating field it would "like" to produce cannot fit within the boundaries. As long as the atom cannot emit a photon, it must remain in the same energy level; the excited state acquires an infinite lifetime."

if its unradiated, how does it know it wont fit? - it hasn't touched or seen the walls.. and why does it 'fitting' really matter, why not just radiate and get all messed up, why does it care at all?

[Strange]

This seems to be the article: http://www.scientificamerican.com/article/cavity-quantum-electrodynamics/

[swansont]

Don't anthropomorphize nature. She hates that.

[Endy0816]

This talks a bit about it:

 

https://en.wikipedia.org/wiki/Cavity_quantum_electrodynamics

[Strange]

You have to consider the whole system. Quantum effects are not localised. The article explains this further on:

 

How can the photon "know," even before being emitted, whether the cavity is the right or wrong size?

Part of the answer lies in yet another odd result of quantum mechanics. A cavity with no photon is in its lowest-energy state, the so-called ground state, but it is not really empty. The Heisenberg uncertainty principle sets a lower limit on the product of the electric and magnetic fields inside the cavity (or anywhere else for that matter) and thus prevents them from simultaneously vanishing. This so-called vacuum field exhibits intrinsic fluctuations at all frequencies, from long radio waves down to visible, ultraviolet and gamma radiation, and is a crucial concept in theoretical physics. Indeed, spontaneous emission of a photon by an excited atom is in a sense induced by vacuum fluctuations.

The no-photon interference effect arises because the fluctuations of the vacuum field, like the oscillations of more actual electromagnetic waves, are constrained by the cavity walls. In a small box, boundary conditions forbid long wavelengths--there can be no vacuum fluctuations at low frequencies. An excited atom that would ordinarily emit a low-frequency photon cannot do so, because there are no vacuum fluctuations to stimulate its emission by oscillating in phase with it.

[bimbo36]

are photons somehow related to fusion ??

[Strange]

are photons somehow related to fusion ??

 

 

Photons are often released during fusion reactions. For example, when hydrogen is fused to helium, gamma ray photons are released.

https://en.wikipedia.org/wiki/CNO_cycle

 

But this is completely different thing to the subject of this thread.

[bimbo36]

thanks for the reply

 

[Enthalpy]

The effect works in the other direction too. If the atom is in a resonant cavity that favours the emission, the photon is emitted more quickly. Such lasers with one atom have been built too.

[swansont]

The thing is, this in not the only phenomenon where something like this happens. Light takes the path of least time. How does it "know" to do that? (or, as the old joke goes, a thermos keeps hot things hot and cold things cold. How does it know?)

 

But it's the wrong question. That's how nature behaves. There's nothing that says our models reveal the "true nature" of nature. They tell how things behave, not why they behave that way.

[joshuagolden00]

^indeed.. yeah oddly i know quite a bit about vacuum dynamics.. i admit i didnt read the whole thing, think it was a late night.. but one thing thats always bothered me was how the photons that were coming into being in the middle region of the gap, knew not to be, even tho they had not blossomed into a full unit? so really excluding direct wall contact, we still have a problem. right?
but whats this is really getting down to is that as much as people hate to admit it, the vacuum carries an immense amount of info and energy about everything to everything allll the time.. likely mostly thru entanglement.. helping to explain spontaneous entanglement, and entanglement resurrection. iv even read of some people thinking it might be ez to send a signal to a receiver, where the receiver pays for the 'pick up' and the sender only turns a DETECTOR on and off.. same logic really.. so it must be possible

[Carrock]

why does it 'fitting' really matter, why not just radiate and get all messed up, why does it care at all?

Another way to look at it is that the photon is its own antiparticle and an observer's choice of its direction of travel is arbitrary.

It can't exist unless each of its 'origins' is physically valid.

Among other things, you need 'spooky action at a distance' to reconcile that with actual observations of photons.

[swansont]

^indeed.. yeah oddly i know quite a bit about vacuum dynamics.. i admit i didnt read the whole thing, think it was a late night.. but one thing thats always bothered me was how the photons that were coming into being in the middle region of the gap

 

 

The middle region? The photon is not a point particle. The photon would be "coming into being" in the whole region.