Thank you, I lost my mind, briefly, reading that part.

Light slows down in dielectric materials because as an em wave it interacts with the polarization of molecules. Neutrino has very little interaction with matter, OTOH.

This is also the source of the classic blue glow in water cooled nuclear reactors. Electrons move through the water faster than light and leave behind a kind of 'sonic boom' of photons in its wake.

Correct, they do have a probability of interacting, but it's extremely low, depends of the energy of the neutrino (its momentum) but basically it can go through 1 light year of lead and still have only a 50/50 chance of interacting.

to put things to scale 1 ly is 9,460,730,472,580,800 meters, or 63,241.077 astronomical units, the distance from the Earth to the Sun.

Needless to say, it's pretty weakly interacting as far as interaction goes...

Since neutrinos don’t interact with much of anything, its path doesn’t deviate from its origin. Different origins emit neutrinos with different levels of energy. When a neutrino hits a nucleus, the blue light emitting particle in ice follows closely the same direction. Measuring the direction and the magnitude (lighting energy) of the vector we can classify its origin. Collecting a bunch of the same signature we know there's an object at that direction emitting at that energy level. From the vector and energy we kind of know whether it’s from the solar system or not.

Identifying the origin let us see objects behind dust clouds or other obstacles.

We know this because

- In the beginning, for the first couple of events, only because they have way higher energies than anything in the solar system could produce - By now, with enough data collected, their origin correlates very well with the milky way - we are close to identifying several far away galaxies as well

This is the significance. Contrary to some statements published today, IceCube was not primarily built to study Neutrinos, it was built to study the universe using Neutrinos.

That's why we care where they are coming from, we want to learn about the astrophysical objects that produce them.

H2O is the key, not ice. Ice is nice because it's rigid, so you don't need a boat [1]. They're also working on making detector under the sea [2].

[1] https://www.amusingplanet.com/2015/07/the-surreal-world-of-n...

[2] https://news.cnrs.fr/videos/detecting-neutrinos-at-the-botto...