Steve Stewart-WilliamsJul 11, 2023
This photo of the sun might not look too impressive... until you realize it was taken at night – not looking up but looking down, through the entire Earth, using neutrinos rather than light. Amazing! https://apod.nasa.gov/apod/ap980605.html
APOD: June 5, 1998 - Neutrinos in the Sun

Show threadJost MigendaJul 12, 2023

@SteveStuWill Not just at night—that photo was taken using over a year of 24/7 “exposure”.

(Though here’s one of my favorite facts I learned while working on this experiment: We do actually see slightly *more* neutrinos at night, when they have to travel through the whole Earth!)

Show threadNoah Cook

@JostMigenda @SteveStuWill Does that imply that passing through more mass has an effect on whether a neutrino will interact with future mass?

I keep starting the next sentence with "I would have thought..." but I realize that of course any approach to anything Standard Model-related that begins with "I would have thought" is probably by definition wrong. I think what I mean to ask is:

How does passing through the Earth affect neutrinos?

Jul 12, 2023 at 4:00amWeb
Show threadBadibulgatorJul 13, 2023

@UncivilServant @JostMigenda @SteveStuWill It affects them very little. On the other hand it completely blocks muons or other particles created by cosmic rays hitting the atmosphere.

Therefore, considering only particles moving upwards improves the signal/noise ratio because it eliminates the latter.

Show threadJost MigendaJul 13, 2023

@badibulgator @UncivilServant @SteveStuWill That’s a real effect & very important when observing high-energy neutrinos! Solar neutrinos on the other hand have ~10000 times less energy than an average cosmic ray muon, so we’re not at risk of mistaking them for each other.

No, the day/night asymmetry I’m talking about is a bit more subtle. I’ll try to write an explainer thread this evening, after work.

Show threadBadibulgatorJul 13, 2023
@JostMigenda @UncivilServant @SteveStuWill I’m looking forward to it! 👍
Show threadJost MigendaJul 14, 2023
@badibulgator @UncivilServant @SteveStuWill Explainer thread is at https://mastodon.social/@JostMigenda/110709406468544035 Enjoy! :)
Show threadNoah CookJul 14, 2023

@JostMigenda @badibulgator @SteveStuWill Wow, I was aware that muon and tau neutrinos existed, but I hadn't even thought about them. I mean, it's not like we worry about microchips using muons instead of electrons...we don't, do we?

Errrm, is this another one of those "thank G_d we have a geomagnetic field" things?

Show threadJost MigendaJul 14, 2023

@UncivilServant We don’t; electrons, muons and taus don’t change into each other like that. That’s a neutrino thing.

(And it’s unrelated to the geomagnetic field; electrons don’t do that in space either.)