8 ms·

Depending on what you mean precisely, I'd actually say that most of our light sources other than the sun don't come from matter, in the sense that they don't tu

Depending on what you mean precisely, I'd actually say that most of our light sources other than the sun don't come from matter, in the sense that they don't turn matter into light but rather light is created when the energy level of electrons changes (whether in electric or chemical light sources). Of course indirectly, this energy comes from matter being turned into energy, whether by the sun or by nuclear fission. What I find more interesting is that today, all our energy ultimately can be traced back to stars, even if sometimes extremely indirectly (e.g. in the case of fossil fuels or nuclear fission). But this could actually change -- if nuclear fusion becomes used in practice.

kobeya 9y ago
> they don't turn matter into light but rather light is created when the energy level of electrons changes (whether in electric or chemical light sources). > Of course indirectly, this energy comes from matter being turned into energy, whether by the sun or by nuclear fission. This is incorrect. It directly comes from matter as the rest mass of the low energy state is a minuscule amount less than high energy state. Specifically it is E/c^2 less, where E is the energy of the photon.
- eternauta3k 9y ago
  Parent is talking about different processes that produce photons: classical acceleration of charged particles vs particle-antiparticle annihilation. You brought in a fact from general relativity which has no bearing on which processes are more common in the universe. Of course you can always be pedantic and analyze problems at the wrong level. For example, you can say it's all the same QED vertex in the end.
  - kobeya 9y ago
    They are fundamentally the same mechanism by our current understanding of physics. It is not a pedantic point.
zachrose 9y ago
> What I find more interesting is that today, all our energy ultimately can be traced back to stars, even if sometimes extremely indirectly (e.g. in the case of fossil fuels or nuclear fission). But this could actually change -- if nuclear fusion becomes used in practice. Wow, that's a cool thought. In an attempt to continue, even human-made fusion energy is an extremely indirect output of the sun. Photosynthesis, animals, evolution, human history, and even fossil fuels enable the right conditions for more fusion energy. The system understands itself well enough to recreate its most massive and awesome force in miniature.

kobeya 9y ago

> they don't turn matter into light but rather light is created when the energy level of electrons changes (whether in electric or chemical light sources). > Of course indirectly, this energy comes from matter being turned into energy, whether by the sun or by nuclear fission. This is incorrect. It directly comes from matter as the rest mass of the low energy state is a minuscule amount less than high energy state. Specifically it is E/c^2 less, where E is the energy of the photon.

eternauta3k 9y ago
Parent is talking about different processes that produce photons: classical acceleration of charged particles vs particle-antiparticle annihilation. You brought in a fact from general relativity which has no bearing on which processes are more common in the universe. Of course you can always be pedantic and analyze problems at the wrong level. For example, you can say it's all the same QED vertex in the end.
- kobeya 9y ago
  They are fundamentally the same mechanism by our current understanding of physics. It is not a pedantic point.

zachrose 9y ago

> What I find more interesting is that today, all our energy ultimately can be traced back to stars, even if sometimes extremely indirectly (e.g. in the case of fossil fuels or nuclear fission). But this could actually change -- if nuclear fusion becomes used in practice. Wow, that's a cool thought. In an attempt to continue, even human-made fusion energy is an extremely indirect output of the sun. Photosynthesis, animals, evolution, human history, and even fossil fuels enable the right conditions for more fusion energy. The system understands itself well enough to recreate its most massive and awesome force in miniature.