4 ms·
I was about to post the same question. I'm guessing the author meant something not-obviously-wrong here, but I can't guess what. But he also writes this: > S
by CoastalCoder 2y ago
I was about to post the same question. I'm guessing the author meant something not-obviously-wrong here, but I can't guess what.
But he also writes this:
> Since the Sun’s light was made at the height of the last Ice Age, for all we know its nuclear fires could have gone out 29,000 years ago.
Which makes me even more confused.
- QuadmasterXLII 2y agoDiffusion is slow, the sun is large.
- CoastalCoder 2y agoCould you elaborate? I don't think I have the background to understand your point.
- r2_pilot 2y agoLight emitted from the core of the sun is re-absorbed by the stellar plasma/matter many, many times before the energy finally, as the result of a random walk, is expressed close enough to the surface that its mean free path is on the order of the distance to Earth. However, since neutrinos are not affected by the charged matter, they are free to leave far more easily and thus, rather than a random walk lasting thousands of years, they simply "flit" right through the intervening material until they hit our detectors (extremely rarely).
- RIMR 2y agoThe issue a lot of people have with this is that they think of the Sun as a big ball of fire, where the activity is happening on the surface of a big flammable mass. They Might Be Giants has two songs about this exact misunderstanding. In the first song, "Why Does The Sun Shine?" they sing (incorrectly): >The Sun is a Mass of Incandescent Gas >A gigantic nuclear furnace. In their next song, "Why Does The Sun Really Shine?", they sing: >The sun is a miasma >Of incandescent plasma >The sun's not simply made out of gas >No, no, no >The sun is a quagmire >It's not made of fire >Forget what you've been told in the past Most of the photos that create sunlight are born at the core of the Sun. The Sun is one gigantic nuclear reaction. The activity isn't at the surface, there's hot energetic plasma (and other exotic states of matter) all the way down to the core. Photons from the core have to make their way through a unfathomably massive sea of matter and energy before they can escape into space. From core to surface, a photon takes about 30,000 years to make it's way through all of that. What's crazy is that our Sun is an orange dwarf star which is quite small compared to some of the other stars in our Galaxy. A photon born in a hypergiant star with much greater mass and core density could take millions of years to escape.
- vlovich123 2y agoBut a single photon isn’t making its way ever from the core to the surface is it? Wouldn’t all the photons in the core be absorbed by all the charged particles and reemitted as new photons and thus the photons you see are photons being emitted from the surface?
- bookofjoe 2y agoQuantum theory makes it extremely [understated!] unlikely that a photon emitted from the surface of the sun originated in the core. Photons blink into/out of existence for all practical purposes instantaneously. Otherwise Josephson junctions, quantum tunneling and modern electronics would be DOA.
- vlovich123 2y agoInstantaneously? https://physics.stackexchange.com/questions/613005/how-long-does-it-take-an-electron-to-emit-or-absorb-a-photon https://physics.stackexchange.com/questions/613005/how-long-... says it takes time for a photon to be absorbed and then reemitted
- bookofjoe 2y ago"for all practical purposes instantaneously"