Nit: I think that the light from the sun is about 100k years old. Wild.

Nit of a nit; the energy might take that long, but the photons that reach us on Earth are not directly created by the nuclear fusion reactions in the sun's core. Fusion creates high-velocity nucliei and other particles, but not visible light. The resulting heat creates photons which are rapidly destroyed by absorption. Only photon emission from the outer most layers of the sun reach Earth.

	▲	greenbit 4 days ago \| parent \| next [-]
		I.e., that bit they refer to as the photosphere, effectively the radiating 'surface' of the sun, is the source of the solar photons that strike us here. That trip takes about 8 minutes.
	▲	HardCodedBias 4 days ago \| parent \| prev [-]
		You are totally right! I knew HN would nit my nit, well done!

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aplummer 4 days ago | parent | prev [-]

How can that make sense, the photons are emitted and fly straight at us

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siavosh 4 days ago | parent | next [-]

The photons were created a long time ago in the core. It takes thousand of years for it to reach the surface, and THEN it takes 8 minutes to get to us.

	▲	greenbit 4 days ago \| parent [-]
		The photons created in the core are some seriously energetic gama rays. Sure, gama rays are very penetrating, but the solar core is dense, and it's about half a million miles to the surface, so these mostly get absorbed right there in the core, making stupendous amounts of heat. At any given depth that means that matter is going to re-emit photons, but never any more energetic than the original ones that are absorbed, but that radiation will be reabsorbed as well. That process of emission and reabsorption means that energy travels to the surface a lot slower than light in a vacuum, and sure, it takes a long time for that energy to reach the surface, but the photons that reach the earth are only the ones created close enough to the 'surface' to escape into space.

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stevenwoo 4 days ago | parent | prev [-]

Photons are not created on the surface but in the core where the environment has the higher pressure needed for the physical creation of the photon and the photon takes about that long to work its way out.

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Rover222 4 days ago | parent | next [-]

Is this in any sense hydrogen being converted to photons? Photons are massless, but… the mass of the elements in the star are converted to pure energy?

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Ekaros 4 days ago | parent | prev [-]

What is the ratio between those and well heat due to nuclear reactions and well pressure. Hot stuff generates visible photons. Say like incandescent light bulb.

So there must be a range in age. As some closer to still hot surface don't need to travel through parts of the sun.

	▲	stevenwoo a day ago \| parent [-]
		So I am not an expert and recalling what I have read in several books and articles, but the conditions of fusion necessary to create photons only exists in the core of the sun. It was a mystery to us and we did not know until scientists were able to use quantum mechanics was able to explain the mechanism, it requires enough temperature and gravitational pressure to force subatomic particles close enough to overcome the forces that ordinarily keep them apart, and this only happens to a small percentage of meeting nuclei with quantum tunneling explaining how they overcome the forces that want to keep the nuclei apart - there's just so many particles squeezed close together that a small percentage that meet (possibly easier to visualize as the quantum wave function describing the position) fuse. This is also why we cannot use this method of fusion on earth - it's impossible to do on earth barring some sci fi artificial gravity invention. If this were not true and fusion could take place anywhere on the sun, the sun could rapidly use up all of the fuel of hydrogen. I am simply repeating what I have read - each photon has to make its way to the surface of the sun after many collisions, since the direction is random and not always outwards, it is theorized they just ping pong back and forth for x years where x can be hundreds of thousands of years. Here's the clearest explanation I found though they only use one slide on the photon's drunken walk https://svs.gsfc.nasa.gov/11084