7 ms·

Where do the photons that hit my retina go when I finish with them? If they have infinite lifetimes then does each one carry a memory of it's creation event? W

Where do the photons that hit my retina go when I finish with them? If they have infinite lifetimes then does each one carry a memory of it's creation event? When I burn a log in my fireplace and a cinder flares and pops creating a spark, does the photon exist after the spark energy flares out and the cinder is no longer illuminated enough to be detected by my eyes? If photons are infinite then harvesting light would be the first step in deciphering the complete history of the universe. All that would be left for us to do would be to derive the algorithms to unravel and categorize each photon into discrete groups based on their historical particle paths. If we wanted to harvest light to test whether photons have infinite lifetimes we would need to design a structure that forms a light trap using materials with different refractive indices so that photons entering are forced onto paths from which they perfectly reflect in a lossless manner. If photons are infinite then mirrors may have a memory if we can trap and monitor the photons that pass through them and force them to unravel their travel paths. Why can't I step in front of the mirror and have it replay every event that the mirror has seen? It would be a better replacement for photo or video mementos of lost loved ones if we could simply take the mirrors from their homes and spin back to watch their happiest moments forever by reconstructing the photon impingement history of the glass and mirror substrate.

adonovan 2y ago
Feynmann is very clear that the photons bouncing off a mirror are not the same ones that hit it. They are absorbed by electric oscillators (free electrons in the material) and destroyed; then new ones are created and emitted. He's also careful enough to point out that electrons don't really have an identity that would allow you to meaningfully define "not the same". :)
- dylan604 2y ago
  Electrons? We were just told that there is only one single electron in yesterday's posts. It's almost like they don't know what an electron is
  - doodlebugging 2y ago
    I believe they're right about there being only one single electron. I tried to start my Pathfinder yesterday and it was dead as a doornail. None of the dash lights lit and there was not even a click from the starter. Someone else must've been using that electron though since I tried again a few minutes later and it cranked right up. I had my turn with it so I'm not mad at all.
    - westmeal 2y ago
      Um maybe check your battery terminals for corrosion :)
      - doodlebugging 2y ago
        I covered all those bases. I'm not 100% sure what happened but when I initially tried to start the vehicle I had it connected to a solar battery maintainer in full sunlight. It should've had bazillions of photons sacrificing part of themselves to be stored electrons but instead I got nothing. After disconnecting that from the battery and testing all the fuses I made another attempt to start it up and it worked fine. It's possible that the voltage output of the panel swamped the voltage expected by the ECU and it refused to energize to save the system from electrical damage by overvoltage. Or maybe that single electron hadn't quite made it to my battery on my first attempt. That's one busy e.
        westmeal 2y ago
        I find pouring electrons into a funnel usually helps by avoiding an electron spill all over your battery. Glad it works tho!
        dylan604 2y ago
        I wonder if that's how they get electrons into the particle accelerators too?
- AgentME 2y ago
  Electrons aren't unique in not having identities. Photons of the same wavelength are similarly fungible if I remember right, though it's a little more defensible to call the reflected light not the same photons since the original photons are transformed to something we don't call photons before photons are produced again.
  - adonovan 2y ago
    Yeah, I meant to say "photon" in my last sentence; but the point is equally true for electrons.
  - doodlebugging 2y ago
    But at a reflection event you aren't producing a new photon, you are only reflecting a portion of the original determined by the refractive indices of the reflection interface. At that interface, part of the original photon is reflected and the rest is transmitted across the interface as a new photon and both have a modified bandwidth relative to the parent photon. So the one you see reflected is the same photon after modification by the medium it traversed and the transmitted components escape your view unless you are monitoring the other side of the medium.
    - wizzwizz4 2y ago
      That would imply a frequency shift, which clearly doesn't happen (mirrors don't redshift the light that hits them).
      - ASalazarMX 2y ago
        I balked at that too, because infinite mirrors and mirror houses also don't show any wavelenght shift no matter how many reflections they do. They do change perceived amplitude, as no mirror is perfectly reflective.
        Jerrrry 2y ago
        Blue, but it's more to do with manufacturing defects and the minerals used for the mirrors.
- doodlebugging 2y ago
  I wonder about the all the photons lost in fiber optic installations. What happens to them in their short lives? There must be a creation and an extinction event. A photon jumps into the glass fiber and travels until it encounters an opto-electric coupler where the photon craps out and is converted to an energized stream of electrons, or maybe it borrows the only real electron in the universe for an instant as it flips across the coupler to the next glass fiber where a new photon is born, only to flare out at the next junction.
  - lolc 2y ago
    My understanding is that photons don't have a life the way we do. They move at the speed of light and thus time does not advance for them. They cannot change between emission and absorption, no matter the distance. Always bends my mind to think about it.
    - rvbissell 2y ago
      > They move at the speed of light and thus time does not advance for them. Isn't it more accurate to say that photons move at the speed of causality, when the medium is a pure vacuum? Because in some other medium like glass, the speed of light is slower than the speed of causality. So my follow-up question is: do slower photons (such as those propagating through a fiber-optic strand, or water) then experience the advancement of time?
      - Kranar 2y ago
        There is no such thing as slow photons, photons always travel at the speed of light. When light enters a medium there are two mostly (but not entirely) equal ways to think about what happens, one is to view light as a purely electromagnetic wave that interacts with atoms and causes the atoms to oscillate. This oscillation produces its own electromagnetic wave that interferes with the original wave. The result of this interference will be an electromagnetic wave with the same frequency, same amplitude, and travelling in the same direction as the incoming light but shifted backwards and it's that shift backwards that gives the appearance of light slowing down. That explanation is pretty good and accounts for almost everything except for the latency of light through a medium. If that's what you want to model, then it's better to think of light as made up of photons instead of being a wave, and then when photons enter a material they no longer exist as independent particles but through a process of absorption and reemission by electrons in the material become particles called polaritons. Polaritons do have mass and hence travel slower than the speed of light. Neither of these explanations are perfect, but the full explanation is ridiculously complicated and there's no suitable metaphor for it. If you are interested in knowing the edge latency of light through a medium, then the polariton explanation is appropriate. If you want to know the "bandwidth" explanation of light through a medium, then the wave explanation is appropriate.
- nullserver 2y ago
  It could be the same electron after all. Although probably not. One electron theory. https://youtu.be/9dqtW9MslFk?si=qdWGUyJnDRCOns9F https://youtu.be/9dqtW9MslFk?si=qdWGUyJnDRCOns9F
- credit_guy 2y ago
  Does Feynman say that? If an electron absorbs a photon, why would it create another one of the same frequency, and with polarization perfectly rotated by 90°?
  - candiodari 2y ago
    Because of the layout of the electron orbitals.
    - credit_guy 2y ago
      Feynman certainly didn’t say anything like that, or only the photons with certain frequencies would reflect, those corresponding to the energy differences between various orbitals.
DennisP 2y ago
If you haven't yet, you should definitely read the famous little scifi story Light of Other Days. Full text: https://www.physics.utoronto.ca/~jharlow/slowglass.htm https://www.physics.utoronto.ca/~jharlow/slowglass.htm
- doodlebugging 2y ago
  Wow. Now that's nice. Someone thought outside our box for that story. Part of the reason that I initially posted on this thread was to ponder the question about a world where mirrors have a memory function. A mirror with a memory would have perfect fidelity though the image would be a mirror image of reality, like looking into a replay from a mirror image universe. I wrote a poem on that subject a couple years ago and the whole question about photons and their potential infinite existence triggered the memory.
_factor 2y ago
What makes you so sure the photon didn’t originate from your eye and finish where you saw them?
- fnordpiglet 2y ago
  I assume you’re referring to Feynmans demonstration that since photons are neutral with no antiparticle in QED a photon going forward in time and backwards in time are the same photon. But from our frame of reference the photon always originates at the origin and hits our eye. From the photons point of reference it’s not meaningful tho to say they go backwards or forwards because time actually doesn’t elapse for them.
fnordpiglet 2y ago
Photons don’t experience time, from their relativistic frame they are created and destroyed instantly. This is because they are massless and therefore always travel at the speed of light. Due to relativity they experience a different simultaneity - in our reference frame we can observe their emission and absorption as energy and existence and measure them etc but, even given they can’t experience anything anyways, time doesn’t pass for them. This is one of the weirdnesses of relativity.
- wholinator2 2y ago
  Right, this would be true if it were possible for a photon to"experience", but at i understand it we currently believe it's not.

adonovan 2y ago

Feynmann is very clear that the photons bouncing off a mirror are not the same ones that hit it. They are absorbed by electric oscillators (free electrons in the material) and destroyed; then new ones are created and emitted. He's also careful enough to point out that electrons don't really have an identity that would allow you to meaningfully define "not the same". :)

dylan604 2y ago
Electrons? We were just told that there is only one single electron in yesterday's posts. It's almost like they don't know what an electron is
- doodlebugging 2y ago
  I believe they're right about there being only one single electron. I tried to start my Pathfinder yesterday and it was dead as a doornail. None of the dash lights lit and there was not even a click from the starter. Someone else must've been using that electron though since I tried again a few minutes later and it cranked right up. I had my turn with it so I'm not mad at all.
  - westmeal 2y ago
    Um maybe check your battery terminals for corrosion :)
    - doodlebugging 2y ago
      I covered all those bases. I'm not 100% sure what happened but when I initially tried to start the vehicle I had it connected to a solar battery maintainer in full sunlight. It should've had bazillions of photons sacrificing part of themselves to be stored electrons but instead I got nothing. After disconnecting that from the battery and testing all the fuses I made another attempt to start it up and it worked fine. It's possible that the voltage output of the panel swamped the voltage expected by the ECU and it refused to energize to save the system from electrical damage by overvoltage. Or maybe that single electron hadn't quite made it to my battery on my first attempt. That's one busy e.
      - westmeal 2y ago
        I find pouring electrons into a funnel usually helps by avoiding an electron spill all over your battery. Glad it works tho!
        dylan604 2y ago
        I wonder if that's how they get electrons into the particle accelerators too?
AgentME 2y ago
Electrons aren't unique in not having identities. Photons of the same wavelength are similarly fungible if I remember right, though it's a little more defensible to call the reflected light not the same photons since the original photons are transformed to something we don't call photons before photons are produced again.
- adonovan 2y ago
  Yeah, I meant to say "photon" in my last sentence; but the point is equally true for electrons.
- doodlebugging 2y ago
  But at a reflection event you aren't producing a new photon, you are only reflecting a portion of the original determined by the refractive indices of the reflection interface. At that interface, part of the original photon is reflected and the rest is transmitted across the interface as a new photon and both have a modified bandwidth relative to the parent photon. So the one you see reflected is the same photon after modification by the medium it traversed and the transmitted components escape your view unless you are monitoring the other side of the medium.
  - wizzwizz4 2y ago
    That would imply a frequency shift, which clearly doesn't happen (mirrors don't redshift the light that hits them).
    - ASalazarMX 2y ago
      I balked at that too, because infinite mirrors and mirror houses also don't show any wavelenght shift no matter how many reflections they do. They do change perceived amplitude, as no mirror is perfectly reflective.
      - Jerrrry 2y ago
        Blue, but it's more to do with manufacturing defects and the minerals used for the mirrors.
doodlebugging 2y ago
I wonder about the all the photons lost in fiber optic installations. What happens to them in their short lives? There must be a creation and an extinction event. A photon jumps into the glass fiber and travels until it encounters an opto-electric coupler where the photon craps out and is converted to an energized stream of electrons, or maybe it borrows the only real electron in the universe for an instant as it flips across the coupler to the next glass fiber where a new photon is born, only to flare out at the next junction.
- lolc 2y ago
  My understanding is that photons don't have a life the way we do. They move at the speed of light and thus time does not advance for them. They cannot change between emission and absorption, no matter the distance. Always bends my mind to think about it.
  - rvbissell 2y ago
    > They move at the speed of light and thus time does not advance for them. Isn't it more accurate to say that photons move at the speed of causality, when the medium is a pure vacuum? Because in some other medium like glass, the speed of light is slower than the speed of causality. So my follow-up question is: do slower photons (such as those propagating through a fiber-optic strand, or water) then experience the advancement of time?
    - Kranar 2y ago
      There is no such thing as slow photons, photons always travel at the speed of light. When light enters a medium there are two mostly (but not entirely) equal ways to think about what happens, one is to view light as a purely electromagnetic wave that interacts with atoms and causes the atoms to oscillate. This oscillation produces its own electromagnetic wave that interferes with the original wave. The result of this interference will be an electromagnetic wave with the same frequency, same amplitude, and travelling in the same direction as the incoming light but shifted backwards and it's that shift backwards that gives the appearance of light slowing down. That explanation is pretty good and accounts for almost everything except for the latency of light through a medium. If that's what you want to model, then it's better to think of light as made up of photons instead of being a wave, and then when photons enter a material they no longer exist as independent particles but through a process of absorption and reemission by electrons in the material become particles called polaritons. Polaritons do have mass and hence travel slower than the speed of light. Neither of these explanations are perfect, but the full explanation is ridiculously complicated and there's no suitable metaphor for it. If you are interested in knowing the edge latency of light through a medium, then the polariton explanation is appropriate. If you want to know the "bandwidth" explanation of light through a medium, then the wave explanation is appropriate.
nullserver 2y ago
It could be the same electron after all. Although probably not. One electron theory. https://youtu.be/9dqtW9MslFk?si=qdWGUyJnDRCOns9F https://youtu.be/9dqtW9MslFk?si=qdWGUyJnDRCOns9F
credit_guy 2y ago
Does Feynman say that? If an electron absorbs a photon, why would it create another one of the same frequency, and with polarization perfectly rotated by 90°?
- candiodari 2y ago
  Because of the layout of the electron orbitals.
  - credit_guy 2y ago
    Feynman certainly didn’t say anything like that, or only the photons with certain frequencies would reflect, those corresponding to the energy differences between various orbitals.

DennisP 2y ago

If you haven't yet, you should definitely read the famous little scifi story Light of Other Days. Full text: https://www.physics.utoronto.ca/~jharlow/slowglass.htm https://www.physics.utoronto.ca/~jharlow/slowglass.htm

doodlebugging 2y ago
Wow. Now that's nice. Someone thought outside our box for that story. Part of the reason that I initially posted on this thread was to ponder the question about a world where mirrors have a memory function. A mirror with a memory would have perfect fidelity though the image would be a mirror image of reality, like looking into a replay from a mirror image universe. I wrote a poem on that subject a couple years ago and the whole question about photons and their potential infinite existence triggered the memory.

_factor 2y ago

What makes you so sure the photon didn’t originate from your eye and finish where you saw them?

fnordpiglet 2y ago
I assume you’re referring to Feynmans demonstration that since photons are neutral with no antiparticle in QED a photon going forward in time and backwards in time are the same photon. But from our frame of reference the photon always originates at the origin and hits our eye. From the photons point of reference it’s not meaningful tho to say they go backwards or forwards because time actually doesn’t elapse for them.

fnordpiglet 2y ago

Photons don’t experience time, from their relativistic frame they are created and destroyed instantly. This is because they are massless and therefore always travel at the speed of light. Due to relativity they experience a different simultaneity - in our reference frame we can observe their emission and absorption as energy and existence and measure them etc but, even given they can’t experience anything anyways, time doesn’t pass for them. This is one of the weirdnesses of relativity.

wholinator2 2y ago
Right, this would be true if it were possible for a photon to"experience", but at i understand it we currently believe it's not.