Physics Girl: Super-Kamiokande – Imaging the sun by detecting neutrinos [video] • Hacker News Board

Re: Physics Girl: Super-Kamiokande – Imaging the sun by detecting neutrinos [video]

#101

Post by gosub100 » Wed, Mar 04, 2026, 9:48 PM UTC

fsh wrote: post #37

gosub100 wrote: post #32

Earlier quoted context omitted.

It's not the same photon though. The fusion happens in the core, then takes millennia for the energy to escape. During that time photons are emitted and absorbed by the atoms, until the surface emits one that finally travels to the earth in 8 minutes. Anyway that's taking you from the ELI5 to the ELI9 version. I'm sure someone on here can correct it further.

Any interaction between light and matter can be modeled as absorption and re-emission (stimulated or spontaneous) of photons. In this picture, there is not much difference between a photon traveling through the sun or through a piece of glass, and the analog makes physical sense. Since photons are massless elementary particles, they are indistinguishable and their number is not conserved. The notion of "the same phot…

I agree that photons cannot be distinguished, but how do you reconcile the following:

- photons travel at the speed of light in a vacuum

- it takes 90k years (or whatever) for a photon to travel from the sun's core to your retina?

Ok, the core of the sun is not a vacuum, quite the opposite, but the path is fraught with being continuously absorbed and emitted. It's not one photon travelling at a few km/hr is it?

And I don't think photons are reflected in hydrogen, although I have no proof. I just thought reflection was done with things like flat surfaces or mirrors.

This is why I said "not the same photon", but I admit I have only YouTube-spectator level knowledge

Re: Physics Girl: Super-Kamiokande – Imaging the sun by detecting neutrinos [video]

#102

Post by Jblx2 » Wed, Mar 04, 2026, 11:52 PM UTC

gosub100 wrote: post #101

fsh wrote: post #37

Earlier quoted context omitted.

Any interaction between light and matter can be modeled as absorption and re-emission (stimulated or spontaneous) of photons. In this picture, there is not much difference between a photon traveling through the sun or through a piece of glass, and the analog makes physical sense. Since photons are massless elementary particles, they are indistinguishable and their number is not conserved. The notion of "the same phot…

I agree that photons cannot be distinguished, but how do you reconcile the following: - photons travel at the speed of light in a vacuum - it takes 90k years (or whatever) for a photon to travel from the sun's core to your retina? Ok, the core of the sun is not a vacuum, quite the opposite, but the path is fraught with being continuously absorbed and emitted. It's not one photon travelling at a few km/hr is it? And I…

>And I don't think photons are reflected in hydrogen

The hydrogen in the sun isn't regular molecular H2. It is a plasma or maybe even has a liquid metallic phase (depending on temperature and pressure).

https://duckduckgo.com/?t=ffab&q=hydrogen+plasma+phase+diagr...

Re: Physics Girl: Super-Kamiokande – Imaging the sun by detecting neutrinos [video]

#103

Post by PaulKeeble » Thu, Mar 05, 2026, 12:23 AM UTC

Jerrrrrrrry wrote: post #94

PaulKeeble wrote: post #55

Earlier quoted context omitted.

This is the nature of ME/CFS (caused by Covid or otherwise), it does vary somewhat over time although the course is not always to improvement or around the same level but sometimes to death. She received some form of experimental treatments in order to gain the prior recovery which was at least a stellate ganglion block, she has not mentioned what else she may have received. Hopefully she maintains a higher baseline…

>"Otherwise" Would could this possibly be referring to?

Many different viral infections and other immune pressures can kick off ME/CFS. We don't yet know what otherwise actually means really, Epstein Bar Virus and Influenza but there is likely many others and only 70% of patients with the condition say it was initiated with an infection. Its a question well worth good research, there just isn't much in the way of funding for ME/CFS.

Re: Physics Girl: Super-Kamiokande – Imaging the sun by detecting neutrinos [video]

#104

Post by pantulis » Fri, Mar 06, 2026, 12:49 PM UTC

mikkupikku wrote: post #46

pantulis wrote: post #24

Earlier quoted context omitted.

Light from the sun that is reaching us now escaped the surface of the sun 8 minutes ago, yes. But photons are generated in the core through nuclear reactions, where they take their sweet amount of thousands of years bouncing around until they get out.

I think this is right in a certain sense, but not precisely. From what I understand no visible light photons are created in the core from nuclear fusion, it's mostly a bunch of gamma rays that get almost immediately absorbed. The energy, but not the photons from fusion, gets transfered up through the layers of the sun, through radiation and convection, eventually heating the photosphere. It is then the photosphere, w…

Thanks for your answer, I understand you're correct. Also, as another counterargument, if a photon is scattered... is it the same photon or a different one? Your perspective on energy instead of particles is better.