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According to Feynman in this youtube video the photons that are released when a tree burns are sort of those that were trapped during photosynthesis.

Are these the exact same photons produced by the Sun or do photons get destroyed / created somehow?

Phoenix87
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Snowcrash
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    It really depends on what you mean by "the same photons". There are a lot of ways in which photons get destroyed and created. For example when light travels in a medium with some index of refraction, in which the velocity of light is less than $c$, photons are actually continuously destroyed (i.e. absorbed) and re-emitted by the medium. See for example this Phys.SE question about this mechanism. – glS Jan 29 '15 at 16:22
  • Interesting. The "Photon absorption-emission theory" is still just a theory though, right? Or is there proof? – Snowcrash Feb 02 '15 at 16:18
  • It's a well enstablished fact. Modulo of course the complications arising from a less naive quantum mechanical approach to the problem, which are discussed in the linked question. – glS Feb 02 '15 at 17:11

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There are processes where this is ambiguous but certainly not in this case. What Feynman probably means is that the sun-photon's energy is deposited in the chemical bonds in the tree cells (as potential energy of electron orbits, really) and when the tree burns, the electrons release parts of this potential energy and release (new) photons.

So the interesting observation is more about total energy balance and flow of energy and storage.

The photo-synthesis photons' wavelengths are furthermore in the visible spectrum while the photons released in a fire are probably in a wide spectrum including infrared heat.

BjornW
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All matter we meet everyday, from computers to trees are controlled by electromagnetic interactions and gravity. Our senses and bodies work with electromagnetic interactions.

Light/radiation is electromagnetic and interacts with matter. We have discovered that in the same way that matter is composed of atoms and molecules, light is composed of photons, and it is photons that interact with the atoms/molecules of matter and we see ( optical wavelengths), feel heat ( infrared wavelengths) and burn in the sun ( uptraviolet wavelengths). All these are composed of photons.

The light/photons from the sun hits the leaves of the tree and is absorbed, i.e. atoms/molecules go to different energy levels and use the energy given up by the photons to store it in wood and generally in being alive. When wood is burned, the changes in energy levels by the chemical changes of combustion release photons and give up the energy stored in the woold, which energy came from the sun.

So the photons are absorbed and disappear when hitting the leaves of the tree. It is energy that is absorbed and conserved and released as photons when burning.

anna v
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