I don't follow you on the part about them being unlabeled. If there are multiple photons, why would you not be able to follow and label them, at least from a theoretical and not real life point of view?

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CrustalTrudger comes through, as usual.

I would add only that I had the opportunity to participate in several seafloor mapping projects using side-scan sonar, and we mapped out some of these plate boundaries on the East Pacific Rise, Gorda Ridge, and Juan da Fuca Ridge. Actually "flying" the instrument through these canyons and mountains really brought them to life, and in great detail.

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At subduction zones, can the effect of the (presumably) lower temperature and so higher density of the subducted plate on seismic waves be used to map the boundary?

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Can fungible particles be discerned through quantum entanglement?

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I think it’s typically better to understand what’s happening at the classical level before the quantum level for questions like this.

Classically, when an electromagnetic wave enters a material, the material itself responds to the electromagnetic wave because it’s composed of charged particles. The collective oscillation of this macroscopic number of charged particles itself creates an electromagnetic field. The field that you can physically observe and measure is the total electromagnetic field. Through the superposition principle, the new total field will be moving slower, and you can analyze the properties of this total field.

The reason I point this out is that intuition about quantum physics breaks down. For instance, it doesn’t necessarily makes sense to label a photon a specific ID number; photon number is not conserved. Moreover, you cannot distinguish photons of the same energy from each other: to ask if it’s the “same” photon is thus not a meaningful question to ask. Not to mention that photons don’t have classical trajectories in the usual sense, and so on.

In particular, what we conceive as a “photon” is a freely propagating quantum of light in a vacuum, without undergoing interactions. But in a medium, light is clearly very strongly with the material. Indeed, the light in the medium is physically the result of the original light wave interacting with the material. So whatever quantum particle (which is really an excitation of a quantum field) you want to use to describe what’s happening won’t behave like “ordinary” photons.

Some people will even say that you shouldn’t of think of photons like physical objects you can touch and manipulate, but rather the footprint of a quantum mechanical interaction between the electromagnetic field and whatever it is you’re talking about.

Which is all to say: photons don’t act like classical billiard balls of light, and unlike electrons are purely relativistic, so ordinary non-relativistic quantum mechanics won’t work either.

If it was absorbed and re-emitted, then surely the direction of the outgoing photon would be different. Or am I missing something?

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Photons are bosons. They have no exchange interaction. Only exists for fermions.

Photons fall under the category of bosons. They have a spin of 1.

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Which section of the mechanical ventilation system? The only places I could even conceive of legionella growing is in cooling towers that are not properly maintained, and immediately downtream of cooling coils where the condensation pans are plugged and there is standing water.

Condensation occurs where air meets a surface that is below the dewpoint temperature. This is mainly in winter or in warmer weather on cooling coils when mechanical cooling is needed.

Humidification is mainly used in hospitals and when the outdoor air contains very little moisture. (Winter or Desert). Hospitals have high ventilation rates, sick people and immune compromised people. Without humidification, the humidity in the occupied space can drop far below the optimum for health and comfort of around 50%

Thank you!

Soot is generally caused by incomplete combustion. It is hard find soot on a natural gas burner with a clean blue flame. All carbon is oxidized. With wood the chains of carbon is very long and the combustion is slower cooler and longer many newer wood burning stoves have a reburn where super heated fresh air is introduced to oxidize and ignite some of the gasified wood that would be soot. Imagine soot as tiny particles of charcoal. Also remember combustible means it’s flash point is above 100c.