Neutrinos – tough to think about
the standard model – pre-Higgs
I recently told myself that I would focus more on my ‘main topic’, bonobos and human culture, patriarchy and matriarchy and all that stuff, and yet…
I can’t keep to the script. Now I’m thinking about physics, and whether neutrinos have mass. But how can a particle not have mass? Light is described in terms of waves and their lengths, but also in terms of photons, particles that have no mass. But surely that makes no sense, or at least common sense. In order to comprehend this you have to start thinking about the equation of mass with energy, and perhaps stop thinking of a photon as a particle, but instead as an energy package. Quantised energy? Einstein’s famous theory related mass to energy, and light-speed. We can only get to light-speed by converting our mass to ‘pure’ energy. And it’s best to think of these things abstractly, rather than worrying about weight-loss. When we leave Earth’s gravitational field, we float, as if ‘weightless’. Yet we have mass, of course. And then what? What does ‘float’ mean? Would we just stay in the same position, eternally, or would we drift, attracted by the gravity of the nearest large object, or suspended between two gravitational fields? The Moon is spiralling away from the Earth, very very slowly, and is tidally locked to us, and as it spirals away, the Earth’s rotation slows, with an equal and somehow related slowness. Would our bodies finally be drawn to a spinning planet, and be caught in an orbit like the moon? One question leads to another, and I have no answers.
But I’m getting carried away, rather too literally. But thinking of the moon, and our orbiting body – if the moon is spiralling away (and it definitely is), will it one day cease to orbit, and will our Earth’s axial spin grind to a halt? It’s definitely slowing down, and was, according to astrophysicist Madelyn Broome, referenced below, spinning at a rate fast enough to make for a five-hour day when the moon first formed. But we’re talking billions of years here, and the sun will apparently begin to die long before the moon-Earth system becomes problematic for future Earthlings, whatever they may be…
So, where was I?
Massless particles. It was neutrinos that started it all (or was it photons?). They appear to be something of a problem for the standard view of particle physics. A tiny-teeny mass has been attributed to them (or some of them? – there are three different ‘flavours’, I’ve heard, but more of that later). Here’s what the Melbourne Theoretical Particle Physics research group has to say:
A striking fact about the neutrino masses is that while they are nonzero, they are really tiny, at least a million times smaller than the electron mass, which is itself a small quantity. The suspicion is that neutrinos acquire their masses via a quite different mechanism from the other particles. We do not know what that mechanism is.
The famous or infamous Standard Model of particle physics describes or hypothesises three neutrino types/flavours – electron, muon and tau. We know (by which I mean they know) that neutrinos stream out of the Sun in vast numbers as a result or by-product of nuclear fusion. I’m guessing that this huge stream, which hits the Earth, and us, is what inspired physicists to build underground detectors – and yet we/they know, apparently, that gazillions of these neutrinos are passing through our bodies right now, so they must already have detected them, right? Or do they just pass through us theoretically?
The good thing about neutrinos, if you can call it that, is that very very smart people who’ve worked on them for decades are just as mind-boggled by them as I am, or almost – familiarity may be breeding a touch of contempt, who knows? I mean, they know, so they say, that trillions of neutrinos are streaming through my body undetected or felt by me every (name any super-short period of time). They’re ghostly, insubstantial, and yet essential, presumably. They play a fundamental role, an essential role, in the make-up of the universe. Thank dog we discovered them. We’re going to try and use them, they say, to solve the mystery of dark matter…. heaven help us.
References
https://www.livescience.com/space/the-moon/will-earth-ever-lose-its-moon
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