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Why are some things darker when wet?

aryankashyap.com

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Re: Why are some things darker when wet?

#111

Post by marcosdumay »

aphextron wrote: post #18

This is a bit hand-wavey in its' description of light reflecting. One of the most mind blowing bits of physics I've ever learned is that photons do not actually "bounce" off of a surface like little balls. They are always absorbed and re-emitted. The actual photons that hit an object are not the same ones that eventually enter your eyes. The atoms in an object are stimulated by photons hitting them to then emit a new…

> The atoms in an object are stimulated by photons hitting them to then emit a new photon via the photo-electric effect, which we perceive as light "bouncing".

That's how electrons and photons interact. It doesn't make sense to say that they are different photons or the same ones, since you can't observe the interaction.

Re: Why are some things darker when wet?

#112

Post by zelphirkalt »

tsbinz wrote: post #91
empath75 wrote: post #72

Earlier quoted context omitted.

> They are not the same photons. How do you define "the same" for two photons?

This is the question that should be higher up in the thread. This whole discussion makes no sense. Photons carry no hidden identity.

Who knows, maybe they actually do, but we do not know it yet. I mean, how do you know they do not?

Re: Why are some things darker when wet?

#113

Post by throwaway_tech »

samatman wrote: post #108
throwaway_tech wrote: post #105

Earlier quoted context omitted.

>In this context, it means visible light. When did "I pretend otherwise"? My comment(s) have nothing to do with the meaning of light. I'm not sure what you get out of pretending otherwise. Either way in the dark when you can't see, the author is wrong, that doesn't mean there is no light...there is light, at minimum the person who can't see is emitting it. Many people don't know that and find it interesting. Its not…

You're doing it again. Humans do not radiate visible light. Also colloquially referred to as light.

Now I see the problem and confusion on your end...you don't think humans emit visible light.

Like I said, most people don't know and are fascinated, that is why I shared it...I don't find many who dispute it, but here are some articles about the studies that confirmed it:

https://www.sciencealert.com/you-can-t-see-it-but-humans-act...

https://www.nationalgeographic.com/science/phenomena/2009/07...

https://journals.plos.org/plosone/article?id=10.1371/journal...

Re: Why are some things darker when wet?

#114

Post by zelphirkalt »

dan-robertson wrote: post #86
aphextron wrote: post #18

This is a bit hand-wavey in its' description of light reflecting. One of the most mind blowing bits of physics I've ever learned is that photons do not actually "bounce" off of a surface like little balls. They are always absorbed and re-emitted. The actual photons that hit an object are not the same ones that eventually enter your eyes. The atoms in an object are stimulated by photons hitting them to then emit a new…

It doesn’t really make sense to talk about “the same” photon because photons don’t really have identity. Even in a vacuum you can send a photon in one end and see one on the other and not really know that the one going in was “the same” as the one going out. It can turn into other particles on its way and then recombine into a photon and there is no way to know this based on the observation that a photon came out of…

That's one of the things, that annoys me with questions about physics, which me might not know well enough yet: When someone asks about whether something "is", people answer with what we can in general know at our current level of understanding and then make it seem as though that is the same, as answering the question, what really "is".

> Even in a vacuum you can send a photon in one end and see one on the other and not really know that the one going in was “the same” as the one going out.

I don't really care, if _I or current physicists_ cannot _distinguish_ them, when I ask, whether they _are_ the same. I would rather have an answer like as follows:

"We do not know this yet. We do not have the means of telling, whether it is really the same photon or not. However, even if they were not the same, it would make no difference (according to our current understanding of physics!), as their effect on the surroundings would still be the same, because ..."

Re: Why are some things darker when wet?

#115

Post by melon_madness »

whatshisface wrote: post #95
samatman wrote: post #93

Earlier quoted context omitted.

Only if the momentum wasn't transferred to the mirror. Which is, in fact, what happens. Solar sails exploit this fact: https://en.wikipedia.org/wiki/Solar_sail

If momentum was transferred to the mirror then the emitted photon would not have the same momentum as the absorbed photon.

Conservation of momentum doesn’t mean that the momentum of the emitted photon has to be equal to that of the absorbed photon. It means the sum of the momentum of the emitted photon and the mirror must equal the momentum of the absorbed photon, assuming the mirror had no momentum to begin with.

Re: Why are some things darker when wet?

#116

Post by rosybox »

zelphirkalt wrote: post #112
tsbinz wrote: post #91

Earlier quoted context omitted.

This is the question that should be higher up in the thread. This whole discussion makes no sense. Photons carry no hidden identity.

Who knows, maybe they actually do, but we do not know it yet. I mean, how do you know they do not?

The absence of evidence doesn't make an idea more plausible, it makes it less plausible.

I can't disprove that a celestial teapot is circling the sun between Earth and Mars, so how do you know it isn't?

https://en.wikipedia.org/wiki/Russell%27s_teapot

Re: Why are some things darker when wet?

#117

Post by kupopuffs »

phaemon wrote: post #104

This is the theme of Bon Jovi's ill-fated concept album "Dark When Wet", the followup to their smash hit "Slippery When Wet". Such commercial success must have gone to their heads to attempt such an audacious second project as a sequel based on Quantum Electrodynamics. It was doomed to failure. Re-interpretations of their classics, such as "Wanted, Dead or Alive - Schrödinger Redux" failed to capture the live animal…

I'm sorry what

Re: Why are some things darker when wet?

#118

Post by zelphirkalt »

rosybox wrote: post #116
zelphirkalt wrote: post #112

Earlier quoted context omitted.

Who knows, maybe they actually do, but we do not know it yet. I mean, how do you know they do not?

The absence of evidence doesn't make an idea more plausible, it makes it less plausible. I can't disprove that a celestial teapot is circling the sun between Earth and Mars, so how do you know it isn't? https://en.wikipedia.org/wiki/Russell%27s_teapot

Less plausible != impossible.

"Knowing" for me means, that there is no way, that we can be wrong about something. Otherwise it's only "believe", not "knowledge".

It would be good to say the following, instead of "it is so": "So far experiments did never show any sign of identity of photons." (Were there any such experiments?) Oh and what about quantum entanglement of photons? Could that not be interpreted as a sign of identity?

Re: Why are some things darker when wet?

#119

Post by ngvrnd »

empath75 wrote: post #72
chemeng wrote: post #59

Earlier quoted context omitted.

They are not the same photons. They are emitted by the electron changing energy states after excitation of the incoming photon. But your intuition that there is some quantum weirdness is correct. Quantum Electrodynamics is the theory you're looking for. It unifies quantum mechanics and special relatively in the context of light/matter interaction. Given you seem to be familiar with Feynman. You're in for a treat! His…

> They are not the same photons. How do you define "the same" for two photons?

it's all the same photon
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