Please clarify the process of how astrophysical neutrinos originate

Dear intertwit,

As one of the world’s leading cosmologists I’ve been grappling with the issue of how astrophysical neutrinos originate. Needless to say, you’ll be well aware that very high energy neutrinos are thought to result when cosmic rays collide with photons in microwave background radiation (that’s not the thing in your kitchen just to kick you off in the right direction). We’re not sure what sets this process in motion and indeed how cosmic rays are accelerated,. You’ll be well aware that some eminent scientists have hypothesized that it relates to matter falling in to black holes. I think not! After years of grappling with this subject, both myself and my colleagues here at the institute have concluded that the only way we can get to the bottom of this perplexing question is to ask you.

I look forward to your answer which of course could have a very significant impact as it’ll give us a definitive stance on the sources that are accelerating these particles to extremely high energies.


Major Twit Asked on 2016-04-25 in I'm confused.
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Well well Minor Twerp, what a highly interesting question this is. And a subject which you’ll be pleased to know is something we know quite a bit about because, luckily for you, we recently saw an old episode of Star Trek: The Next Generation and they were banging on about neutrinos for the whole 48 minutes!

Unluckily for you, despite being set in the late 24th century, Captain Jean-Luc Picard and his space buddies seemed to know bugger all about neutrinos and just appeared to solve their problem by firing a bunch of photon torpedoes all over the place while the Captain kept on saying “Make it so Number 1”.

So, if these chaps some 350 years in the future don’t know where neutrinos come from what chance do we have in the 21st century?? You’re as likely to find the answer as to what makes a cat sneeze than you are to finding the origin of the electron, muon or tau neutrino.

Neutrinos, as you know, are some of the most abundant yet mysterious particles in our universe. Every second 65 billion neutrinos pass through every square centimetre of our body and the Earth. Neutrinos do not carry electric charge, which means that they are not affected by the electromagnetic forces that act on charged particles such as electrons and protons. They are also extremely tiny because of which they travel mostly undisturbed through matter. This makes neutrinos extremely hard to detect, and the harder a particle is to detect, the more massive and sophisticated the detectors have to be.

Never fear though as some clever blokes in Japan we know have recently made a neutrino detector called the Super-Kamiokande. Built 1km underground in Japan this special device holds 50,000 tons of ultrapure water in a cylindrical stainless steel tank that is 41.4 metres tall and 39.3 metres in diameter. This is surrounded by 11,146 photomultiplier tubes . When a neutrino interacts with the electrons or nuclei of water, it produces a charged particle that moves faster than the speed of light in water (not to be confused with exceeding the speed of light in a vacuum, which is physically impossible). This creates a cone of light known as Cherenkov radiation, which is the optical equivalent to a sonic boom. The Cherenkov light is projected as a ring on the wall of the detector and recorded by the PMTs. The distinct pattern of this flash provides information on the direction and flavor of the incoming neutrino.


So we asked the lads at Super K if we could have a go and find our own conclusions. Of course they said no. The facility cost 10’s of millions of pounds to develop and maintain and they don’t need us coming over and mucking the place up leaving our fizzy pop cans and crisp packets. They actually said that. Charming.

How hard can it be though to build a neutrino detector? As it turns out it was pretty simple and we made one ourselves using a sneezing cat, a bowl of water and a j-cloth.

For reference, the Super Kamiokande neutrino detector in Japan looks like this:


The Interwit neutrino detector looks like this:

NeutronoSneezeClick on the picture to enlarge 

Unless your cat has hayfever you’ll need to induce sneezing in the animal as we did by methods such as feather manipulation. The Neutrinos generated by the sneeze were then caught using j-cloth to soak them up. Those that passed through were kept harmlessly in stasis in the water bowl.

And look at the results when we looked at the j-cloth under x15,000 magnification. Clear evidence of our neutrino buddies.

NeutrinoMagnificationClick on the picture to enlarge

Incidentally, scientists often describe the 3 different types of neutrino as having flavours. We can confirm that they do:

Tau: Mint

Electron: Fish paste

Muon: Egg custard

So in conclusion, Minor Twerp, neutrinos are created by feathers or hayfever. And that’s the same for sneezing cats.

Nobel Science Prizes all round!

Chief Twit Answered on 2016-04-26.
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