A Neutrino Walks Into a Bar…

and orders a scotch. When the drink arrives, he takes one sip and collapses in a drunken stupor.

The neutron looks down on the neutrino, disdainfully, and says, “Lightweight!”


I thought I’d break the ice with a joke. Because I apparently think we need icebreakers… You know what? I loathe icebreakers. They never work right. They are either super awkward or just lame as hell.

Remember those icebreaker activities that were always required of new groups of people? Fuck that shit. I would always get super nervous as my turn approached… but why? I know my name and hometown and favorite color. I don’t have to think of anything particularly clever to say, I just have to regurgitate two or three basic facts about myself and then be quiet. HOW IS THAT DIFFICULT, BRAIN?!

*ahem* I’m getting off topic a bit here.

That icebreaker joke (whether effective or not) was my oh-so-clever way of introducing to you the topic of today’s post:


We’ll get to the why part of this in a minute. First, I think we need one of my trademark science primers. Aren’t you excited? BE EXCITED, DAMMIT.

So, what are neutrinos, exactly? Neutrinos are leptons, a subset of elementary particles in the Standard Model. Yep, the Standard Model is back in our talks today, because… well, because it’s important.

I guess we need to backtrack for a second here. See, I mention the Standard Model every now and again when chattering about particle physics, but many people don’t actually know what it is.

Behold the Standard Model:

Isn’t it beautiful? *sniff*

See, that’s really all the Standard Model is- a description of the elementary particles and how they interact. And while that seems pretty basic, remember that these are the building blocks of everything in the universe.

So the Standard Model is pretty goddamn important.

In green there are the leptons. And the top three are our neutrinos.

Neutrinos are incredibly difficult to detect, because they travel at nearly the speed of light but have an incredibly small, non-zero mass. They pass through matter almost undisturbed (in fact, 50 trillion solar neutrinos pass through your body every second), and they are electrically neutral.

Those little devils.

But, unlike the Higgs boson, these ghostly particles have been detected. And we’ve discovered that they come in a variety of types or “flavors.” Like a delicious ice cream buffet:

Only more like this, because there are only three flavors of neutrinos:

But that is just so much less impressive-looking… Oh well.

So, we have three flavors of neutrinos: electron-neutrinos, muon-neutrinos, and tau-neutrinos. These little particles don’t appear in ordinary matter. They arise out of certain types of radioactive decay and nuclear reactions (like those that take place within stars or nuclear reactors).

But there’s an even more interesting idea surrounding neutrinos. We all know that a mere 5% of the universe’s heft comes from normal matter, with a projected 25% coming from dark matter and 70% coming from dark energy. Which is all fine and dandy, except that we don’t really know what this dark stuff is made of. We know it’s most likely not comprised of familiar particles like protons and neutrons.

So… what is it?

Well, there are a number of proposals. But one important fact about dark matter is the likelihood that billions of dark matter particles are zipping through your body every second.

Sound familiar?

That’s a big reason why neutrinos are a candidate for the building blocks of dark matter- they are able to pass through matter without leaving a significant trace. There’s only one problem with neutrinos- they aren’t quite massive enough to be dark matter… in fact, they fall short of the mark by more than a factor of a hundred.

Now, let’s get to the why of this post.

Recently, the Gran Sasso laboratory in central Italy announced that they had observed a neutrino changing flavors- a muon-neutrino changed to a tau-neutrino. This is the first time scientists have actually observed the flavor-changing, though there’s been a great deal of speculation about chameleon-like properties among neutrinos (originally posited by two Moscow scientists in the late 1960s). See, the neutrinos that hit Earth actually arrive in far smaller numbers than the Standard Model says they should. By proving that neutrinos can switch identities, we open the door back up to the possibility that other flavors of neutrinos could exist but currently escape detection.


Because of this, neutrinos are back in the running as possibilities for dark matter constituents, as we simply might not have yet discovered the dark matter flavored neutrino.

Mmm, dark matter tastes like black licorice and pop rocks (pretend that’s a flavor and not a sensation).

However, this also proves to be another blow to ye olde Standard Model, who’s been the standard of physics for nigh 80 years. But then, dark matter/energy has always been a problem for the Standard Model.

It’s becoming more and more obvious that, if the LHC lives up to its promise and starts helping us fill in some of the gaps in our theories, we’ll have to substantially overhaul the Standard Model to create a new working explanation of particle physics.

Also, I now want ice cream real bad. Instead, I shall sit here and listen to Goo Goo Dolls albums on shuffle, because it’s been too long since we hung out and I missed the crap out of them.

One response to “A Neutrino Walks Into a Bar…

  1. Hi, I’m Tom Lima and I’d like to translate this post to protuguease if you allow.


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