JOHN MEANEY

24.9.11

IT AIN'T OVER

...till the fast neutrino sings (and exits faster than the speed of light - maybe). Taking a look at the CERN paper on the OPERA experiment, it's in the true spirit of discovery and sharing: listing everything they can think of for the world to look at. No bandwagons in sight; more like: "We've only got one explanation for these readings, and it's a nutty one. Anyone got a more mundane explanation?" Occam's Razor is still a handy tool.


From a quick glance, the maths is a little tricky - you don't actually know, when running the experiment, the exact time an individual neutrino starts and ends its journey. In fact, the neutrinos are created en route - the original emitter produces protons that produce pions or kaons (when I was lad, they were called π-mesons and K-mesons), which further decay into a muon (μ-meson) and a neutrino... but you don't know exactly where the neutrino was created. However, you can work out the probability distribution around the most-likely point.

The researchers have detailed the way they timestamp every event using GPS; they've even obtained and reproduced seismic studies showing how the ground might move (the overall distance being greater than 70 km, it's a significant factor).

Interesting stuff, eh?

Next step is to wait for Fermilab and others to reproduce the results - or not. If they do reproduce it, then this may just be some outlying piece of anomalous data that someone will explain in 30 or 50 years time, having noticed other phenomena that we might (or might not) be currently aware of. (Dark matter, anybody? The way galaxies rotate is an 80-year-old mystery.)

Sometimes the implications are only obvious later. For example, Maxwell added a mathematical foundation to Faraday's observations of electromagnetic phenomena (shortly before Faraday died). One of the side-effects of the basic equations is an expression for the propagation speed of an electromagnetic wave that depends only on two measurable properties of space, essentially being the ease of propagating electric and magnetic fields respectively. That's yer special relativity right there, or rather the starting observation that makes the rest inevitable.

Or you might think this is more like the way voltages vary during the photoelectric effect - an unexpected experimental result. In the 19th century, the expected result was that the more light you shine on a photoelectric material, the more electricity you get (the more electrons get kicked out of the material). But the real behaviour depends on the frequency of the light - if the frequency is too low (wrong colour!) then you can shine a massive spotlight on the material, but no electricity will be produced. Hence Einstein's realization that light interacts in a particle-like way, not a wave-like way, in this context. (A photon's energy is proportional to its frequency; if each individual photon has too little energy to create the effect, then it doesn't matter how many photons you have - it still won't happen.)

I just find it interesting that the culprit, of all the types of particle known to exist, turns out to be the neutrino. It's always been hard to pin down - for a long time, it was unclear whether neutrinos even had a rest mass. And now look... I hereby propose that we change its name from neutrino to ninja.