[HN Gopher] Physics Girl: Super-Kamiokande - Imaging the sun by ...
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Physics Girl: Super-Kamiokande - Imaging the sun by detecting
neutrinos [video]
Author : pcdavid
Score : 382 points
Date : 2026-03-03 14:42 UTC (8 hours ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| JKCalhoun wrote:
| (Typo in the title.)
| xeonmc wrote:
| (should be Psychic Girl)
| AlexeyBelov wrote:
| As in, knows the future?
| pcdavid wrote:
| Fixed
| danscan wrote:
| TIL nobody can spell phyzix
| Brajeshwar wrote:
| Welcome back. One of my staple YouTube Subscriptions.
|
| I'm today years old learning that the light that we actually see
| on earth today came out 100s of thousands of years ago.
| gosub100 wrote:
| 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.
| amluto wrote:
| I haven't tried to look up the history of this claim, but
| here are some guesses:
|
| 1. There's a sort of diffusion process going on. Photons from
| the core have some mean free path as a function of radial
| position (and, obnoxiously, of wavelength as well, so maybe
| we ignore that). You could calculate the mean time for a
| hypothetical object emitted from the core and traveling
| according to those mean free paths to escape.
|
| 2. You could imagine you have marked a photon and watched it
| travel. This is quite problematic. First, photons in thermal
| equilibrium obey Bose-Einstein statistics because they are
| _indistinguishable bosons_ , and anything that could mark
| them would change the statistics to that of distinguishable
| particles. But whatever, the temperature is high and maybe
| this doesn't matter. Also never mind that those core photons
| are mostly _much_ shorter wavelength than the photons we see.
| But you can still imagine. (The answer is probably quite
| similar to #1 since this is sort of the same problem
| depending on how you think about the interactions with matter
| in the sun.)
|
| 3. You could calculate how long it would take to notice
| anything if the core suddenly stopped fusing.
| gus_massa wrote:
| I agree. I read the 5000 years time a few times and I don't
| like it.
|
| When you have a transparent medium like water or glass, the
| photon that enters and the photon that exit share a lot of
| properties, in particular energy/color/frequency. Perhaps
| they have a shift in the phase or a different polarization
| (like in water with sugar or if you want to be fancy a
| quarter wave plate). You can still split a beam before in
| enter and make interference experiments after half of it
| passed though water or glass, and other weird experiments,
| so I think it's fair to call them "the same photon".
|
| But in the Sun, the original photons in the center of the
| Sun have a few very specific values of
| energy/color/frequency, that are totally lost. (But the
| neutrinos have so few interactions that they don't lose
| this information, and it's possible to do neutrino
| spectroscopy!)
|
| Also, the photons emitted by the "surface" of the Sun have
| a wide spectrum of energy/color/frequency that is very
| close to black body radiation at something like
| 5000K-6000K.
|
| So in my opinion it's better to think that the original
| photon in the center is absorbed shortly after it's
| emitted, and transformed into heat. The heat takes 5000
| years to get to the surface. And then the hot surface emits
| a few new photons unrelated to the original one.
|
| I'm not sure what is the main transmission method inside
| the Sun: conduction, convection or radiation.
| amluto wrote:
| belated edit: My comment about "whatever, the temperature
| is high" is silly. The mean photon energy is about 2.7kT,
| which scales in direct proportion the interest bits of the
| Maxwell-Boltzmann and Bose-Einstein distributions (see [0]
| and [1]). At 2.7kT, the curves are pretty close, but you
| don't have to go down that far to get a big difference. So
| tagging all the light would cause a substantial change in
| the sun's color.
|
| [0] https://scholarship.haverford.edu/cgi/viewcontent.cgi?a
| rticl... Eq. 16 [1] Handy plot at https://commons.wikimedia
| .org/wiki/File:Quantum_and_classica...
| mncharity wrote:
| The canonical Q/A pair "Why does the Sun shine?"/"Fusion in
| its core" perhaps contributes confusion here? Where the
| question is silently swapped out for "Why is the Sun
| _still_ shining after 4+ Gyr? ". You're primed for a close
| connection between core and surface photons. Asking "Why is
| there fog over the uncovered corner of the pool?", one
| seems unlikely to appreciate "the fog comes from a small
| aquarium heater somewhere on the bottom!" (IIRC the
| magnitudes). "The Sun is hot, and hot things glow" creates
| less of that association between core and light.
|
| > You could calculate how long it would take to notice
| anything if the core suddenly stopped fusing.
|
| FW(little)IW (very not my field, just AI, quick&sloppy),
| for a Sun magically switched to contraction-dominated
| heating, I'm sloping order 10^6-7 yr for a 1% increase in
| surface temp, with core contraction dynamics being just one
| uncertainty.
| fsh wrote:
| 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
| photon" is questionable in any case.
| Hikikomori wrote:
| Similar to how infrared radiation works in our atmosphere,
| minus the timescale?
| teamonkey wrote:
| Photons are generated in the star's core but the core is
| dense. The photons move around the core, bouncing off other
| particles, a random walk. It takes a vast amount of time for
| that photon to escape the sun and reach the Earth, as per
| monte-carlo simulations of this random walk.
|
| However, as the photon collides with other particles during
| its random walk, some of its energy is transmitted to those
| other particles. Sometimes a collision transfers energy to
| _it_ too.
|
| In a simple model, the energy that originally belonged to the
| photon gets transmitted from particle to particle through
| convection, and can escape the star through radiation long
| before the original photon reaches the surface. I don't think
| that model is supposed to be physically accurate, rather to
| be an illustration about the convention process inside a
| star.
| cleandreams wrote:
| Wonderful to hear. Her long Covid was heartbreaking (saw the
| videos). I hope she gets stronger and stronger! Welcome back!
| hinkley wrote:
| Some of my favorite YouTubers have done guest spots on her
| channel, which made me love them a little bit more.
|
| Her back catalog is good and you still get paid for people
| watching your old videos.
| jwr wrote:
| So happy to see her back! It was a grueling journey and we were
| all crossing our thumbs, waiting and hoping...
| ayhanfuat wrote:
| Such amazing news. She's been bedridden due to long Covid. Got
| better a few times but after a while attacks came back. Both she
| and her husband showed great strength. So happy to see a new
| milestone.
| patcon wrote:
| thanks so much for the context. I'm glad if she's reclaiming
| from her losses <3
|
| i want to be more appreciative every day for my health post-
| covid... not everyone was so lucky, and I can only imagine the
| gut-punch it is to know everyone went through a thing, but you
| got singled out for some perpetual daily punishment :'(
| roelschroeven wrote:
| Dianna got better sometime last year as well, just in time to fly
| home to Hawaii for her father's funeral (yeah ...), but she got a
| lot worse again later. I really hope things will keep going well
| for Dianna now.
|
| Props for her husband who's been incredible of taking care of
| her.
| dataflow wrote:
| Man... I came here hoping to read she was fine now. Had no idea
| things got worse again :( I hope things get better for her.
| Jeremy1026 wrote:
| At the moment, she appears to be progressing up. The user you
| are replying to was talking about a past up-swing followed by
| a down-swing. Hopefully there isn't a down-swing to follow
| this current up-swing.
| PaulKeeble wrote:
| 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 from here on out and
| the production of these videos doesn't produce further Post
| Exertional Mailise that could worsen her condition.
| human_hack3r wrote:
| Happy to see her back to science!
| nickandbro wrote:
| Is this long Covid or depression or Major Depressive Disorder
| (MDD)? Because in her earlier videos she talks about becoming
| bed-bound again due to her emotional state after finding news her
| friend who had a similar condition died.
| nablaxcroissant wrote:
| It was essentially long covid. me/cfs or chronic fatigue
| syndrome induced by covid infection
| nickandbro wrote:
| Wow, did not know that. Thanks
| dirck-norman wrote:
| As someone who suffers from a complex autoimmune disorder which
| has caused dysautonomia and suspected mitochondrial
| dysfunction, stress flares and exacerbates symptoms. This has a
| physiological basis in the complex way the HPA axis/cortisol
| affects us at the cellular level. My primary diagnosis is
| sarcoidosis with small fiber neuropathy, but they don't fully
| understand all the mechanisms of auto-immune fatigue and
| dysregulation.
| nickandbro wrote:
| Sorry to hear. Thanks for explaining.
| KaiserPro wrote:
| Dunno, personally I don't think its that much of my business.
| Sure I'm curious, but that doesn't mean I have a right, or that
| its a nice thing(tm) to publicly speculate
| hinkley wrote:
| She's been pretty open about it. She even touched on it at
| the end of this video.
| ChrisClark wrote:
| I'm quite sure being that terribly sick could cause depression
| yeah, but that's not the reason
| alabhyajindal wrote:
| BOOM! Let's go
| jesse_dot_id wrote:
| Long COVID is a nightmare. I'm glad she's able to fight it off
| enough to do the things she loves again.
| gosub100 wrote:
| I can't remember where I heard of it, but decades ago there was
| another neutrino detection center, also in Japan I think, that
| had those vacuum tube detectors, but care wasn't taken in systems
| design. One of them broke and the implosion caused the neighbors
| to break. Leading to a catastrophic of almost all the sensors! I
| feel bad for them, I'm sure someone here knows the exact name and
| date. But man, what a tough lesson to learn.
|
| Edit: on another note, way to go on your recovery Diana. We've
| been rooting for you.
| 0PingWithJesus wrote:
| That was Super-K, the same detector she's talking about in the
| video. The incident occurred in 2001 and set back the start of
| the data taking for them quite a bit, they were able to begin
| data taking by re-distributing the unaffected photo-detectors
| to cover the gap where the imploded detectors were. Eventually
| (2005/2006) they replaced all the destroyed photo-detectors and
| took data from then on out with a full-suite of sensors.
| Following this incident all Japanese experiments with these
| types of photo-detectors take the risk of implosion seriously
| and have mitigation built in to the design. Super-K has been
| running continously since then with some interruptions for
| upgrades & maintenance, and is still taking data today (as far
| as I'm aware).
|
| Construction is underway on the next version of the experiment
| "Hyper-Kamiokdande" which is similar in design but
| significantly bigger. If I recall correctly Hyper-K will be two
| 200 kilo-tonne detectors, compared to Super-K which is a measly
| 50 kilo-tonne detector.
| tomasphan wrote:
| It was the same detector that imploded. Mark 2 was then
| reinforced so it didn't happen again.
| legitster wrote:
| It's really cool to see her back and making videos again.
|
| After seeing her status updates 2 years ago I was honestly really
| concerned she would be gone for good. It sounds like she had a
| serious case of myalgic encephalomyelitis brought on by Covid.
|
| Part of why we know so little about these types of conditions is
| they are incredibly unfair. Women are 4x as likely to have some
| sort of constant fatigue disorder as men, and you see this
| reflected in literature going back centuries when describing
| women who just flat out disappear from public life.
|
| One of the things about being bedridden for a long period of time
| is that there is a high risk of becoming more or less permanently
| bedridden. Especially if you have a chronic fatigue syndrome, you
| become weaker and any activity can retrigger fatigue. So her
| pushing herself to make new content sustainably is important very
| encouraging.
| dejongh wrote:
| What an amazing storyteller. I will watch many more of her
| videos. I hope she will make many more videos
| ck2 wrote:
| video about her long-covid battle and recovery here:
|
| https://www.youtube.com/watch?v=vqeIeIcDHD0
|
| (caution for those currently sick as it's a rough watch at first)
| hinkley wrote:
| I know someone whose CFS is about 10% of hers and it was still
| a rough watch. She got hit really fucking hard.
| shadowgovt wrote:
| One of my favorite bits of astrophysics trivia is that the
| neutrino detection experiments serve as an early-warning system
| for supernovae, to allow astronomers to prioritize telescope time
| and swing the scopes around to see the first visible-light and
| radio signals of the event.
|
| This is because the electromagnetic energy of the supernova can
| take hours to force its way through all the star's mass to the
| surface when the core dies, but the gravitational crush turning
| protons and electrons into neutrons releases a massive burst of
| neutrinos in every direction. And the neutrinos are so weakly-
| interacting with the matter in the star that they get out first.
| Then, a million years later, arrive in our solar system at such a
| high fraction of lightspeed that they _presage the coming
| electromagnetic shock-front_ because the constant difference in
| escape time between neturinos, _which are particles of matter_ ,
| getting out of the star without interacting with anything and the
| electromagnetic waves moving through the star's matter at a
| fraction of lightspeed created a gap that the light never caught
| up to.
|
| The universe is a profoundly wild place.
| flux3125 wrote:
| According to science video thumbnails on YT, nothing should be
| possible
| dylan604 wrote:
| I think Super-K is the place with water so pure that it will
| leach pretty much anything which was discovered when one of the
| tech's hair got wet while leaning over the water. The hair looked
| bleached after it went into the water. My googlfu is not finding
| anything to confirm though
| pbhjpbhj wrote:
| Ha, I had never heard of this effect despite having studied
| Kamiokande (well neutrinos, at least) as part of a mini-
| dissertation for my B.Sc.
|
| However, looking for sources relating to leaching by ultra pure
| water (UPW) not much turned up.
|
| I did however find on Google Scholar a paper "Ultrapure Water:
| friend or foe?"... which lead me to
| https://www.balazs.com/sites/balazs/files/2023-03/pub0039-up...
| . Reading between the lines, Marjorie Balazs appears to have
| made a career out of UPW; she says in that paper:
|
| "The ability for UPW to absorb and dissolve or react with all
| kinds of materials complicates other aspects concerning its use
| in the processing of wafers."
|
| Seems like UPW dissolves anything, so lends credence to the
| anecdote.
|
| Interesting topic, hadn't thought about UPW for wafer
| fabrication before.
| hinkley wrote:
| Isn't that also the one where a sensor imploded and caused a
| chain reaction that destroyed like a third of the other
| sensors?
| magicalhippo wrote:
| Yes, except about half. This[1] article goes into how and
| why, without the fluff.
|
| _The chain reaction escalated uncontrollably, and within ten
| seconds, approximately 6,800 of the 11,129 PMTs were
| destroyed._
|
| [1]: https://physicscommunication.ie/neutrino-detector-in-
| peril-t...
| hi41 wrote:
| Reminds me of the scene in Kung Panda 1 where one feather of
| the goose, Peng, falls into the tunnel which Tai Lung uses to
| unlock his cage and escape.
| olivia-banks wrote:
| This is fantastic news! Long COVID is awful, so I'm glad to see
| that she's recovering, if only incrementally.
| hinkley wrote:
| How much of the mass of the universe is neutrinos?
| dotancohen wrote:
| The video mentions that this image was taken during the night
| time. If the neutrinos do not interact with the entire Earth on
| their way through, then how do they interact with the sensor?
| davidmurdoch wrote:
| Watch the video
| dotancohen wrote:
| Thanks. I watched half the video, but couldn't finish it. Now
| that I've finished it I see that the neutrinos interact with
| water in the tank.
|
| Thirty interactions on average per day, that's crazy -
| earlier in the video the host mentions that the cross section
| of a thumbnail has a billion neutrinos flowing through every
| second!
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