Category Archives: Information

Neutrinos

I’m sure you’ve all heard the news; the OPERA collaboration have taken measurements which seem to suggest that neutrinos emanating from the CERN Super Proton Synchrotron travelled the 455 miles through the Earth’s crust to the Gran Sasso Laboratory at very slightly more than the speed of light in vacuum.

For those not versed in the ways of the physics, a neutrino is a fundamental particle. It’s a lepton, the same family of particles as the electron. Unlike the electron, the neutrino has no electrical charge, and so can only interact via the weak nuclear force. That’s how they can travel hundreds of miles through the earth’s crust; they interact with the matter we’re more familiar with (atoms made of electrons, protons and neutrons) only very, very rarely.

That means to detect them you need huge, super-sensitive detectors, typically built deep underground to screen out the signal you would otherwise get from cosmic rays. One is the Super-Kamiokande detector in Japan, which contains 50,000 tons of water. When one of the rare interactions with a neutrino occurs,  the interaction generates a very small amount of light, which is detected and used to infer the properties of the neutrino interaction which caused it.

The OPERA experiment was designed to measure a phenomenon called neutrino oscillation, or neutrino mixing.

There are three types of neutrino: the electron neutrino, muon neutrino, and tau neutrino. The Sun produces a vast number of electron neutrinos as a by-product of the fusion reaction which powers it. When detectors were used to measure the neutrinos being emitted by the Sun, it was discovered that the number was less than would be expected. This became known as the “Solar Neutrino Problem”.

Despite claims to the contrary in certain elements of society and the media, when new evidence is discovered, the theory has to give way. Either the models of what was going on inside the Sun were wrong, e.g. the fusion yield of the Sun was lower that expected, or some aspect of neutrino physics was not properly understood. Cross-checks with other measurements of the Sun indicated support for the Solar models. So the problem was  with the neutrino physics.

It had been assumed that the mass of the neutrino was zero; all measurements made had indicated that it was, at the least, very close to zero. However, if the neutrino had even a very small amount of mass, it would undergo a very peculiar phenomenon due to a quirk of quantum mechanics, called neutrino mixing. Essentially, in the flight from the Sun to the Earth, some of the neutrinos would change flavour, from electron to muon, or tau neutrinos. The “missing” neutrinos were there all along; they just weren’t in the form of electron neutrinos that the detectors were capable of detecting.

The OPERA experiment is designed to more closely measure this process by generating a neutrino beam on demand in an accelerator, and then measuring the mixing that occurred while the beam was in flight.

In doing this, they have apparently detected, to a good degree of statistical significance, that their neutrinos travelled superluminally from the source to their detector. This is well-known to be forbidden by relativity, so if this is a true result, then it will require brand-new physics to explain, and could mark the start of a new era of post-Standard Model physics. It would be one of those fantastic moments where something amazing is discovered by people looking for something else entirely.

That said, it could also be a mistake in their methodology. Relativity has stood unmolested for a century; every experiment concurs with it.

When a supernova occurs, as well as a blinding flash, there is also an extremely intense neutrino pulse. So intense that the even with the rare interaction of a neutrino with the matter we’re made from, the pulse could give you a fatal radiation dose. Knowing how far away the supernova is, the lag time between the observation of the light pulse and the neutrino pulse, and just a dash of astrophysics, you can work out how fast the neutrinos must have travelled, and it comes out subluminal.

So the OPERA guys have done the sensible thing; checked everything they could, and published. It’s very probable that it will turn out to be a complex effect they hadn’t fully considered or was unknown at the time of designing the experiment which will explain the measurements.

The real trouble with these sorts of things is how to manage the media, and how to stop them getting over-excited at things that may well turn out to be nothing, c.f. the hints of the Higgs that melted away in the late Tevatron data.

I actually don’t have much of a point to make about all this, except that the relationship between science, the media, and society, means that there’s really great misunderstanding out there about what’s actually going on. Reading the comments on BBC News, especially the worst-rated ones (thankfully!) does demonstrate the mistrust of science and scientists, and a misplaced belief that science is about arrogance and certainty, when it is really more about doubt, and trusting the weight of the evidence. There’s also a certain group of people who seem to be fully unaware of just how well the world actually is understood these days.

It will certainly be interesting to see what happens if/when these neutrinos are shown to be subluminal!

Then, there’s the wackos, who take any new development as an excuse to just make weird and wacky stuff up. But they’re another story, really.

Gratuitous Equation!

$latex \frac{\partial f_\alpha}{\partial t} + \vec{v} \cdot \nabla f_\alpha + \frac{q_\alpha}{m_\alpha}(\vec{E} + \vec{v} \times \vec{B}) \cdot \nabla_v f_\alpha = \left(\frac{\partial f_\alpha}{\partial t}\right)_{col}$

Apparently you can include $latex \LaTeX$ math support in a WordPress post now by using the Jetpack plugin. Doesn’t seem to align terribly well on my theme, but I approve!

Spotify Post-mortem

For a while now I’ve had a Spotify Premium account, and since I told myself it was an experiment which I would then subsequently review, I really ought to actually do that rather than just letting it roll over and over each month.

I assume most of you are familiar with Spotify; if you’re not, then where the hell have you been the last year? It’s pretty much ubiquitous now.

Anyways, Spotify Premium is £9.99 a month, and that entitles you to higher quality music, offline mode, and use on mobile devices, like the iPhone. A full comparison of the different types of account is available on the Spotify website. The main thing that drew me to paying for premium was the use on mobile devices, like my iPhone, and I have used it pretty extensively.

And, based on that experience, I think I’m going to stop paying for it.

There’s a few reasons for this: the catalogue on Spotify isn’t as extensive I would like, and has a really large number of omissions, the software is occasionally unstable, etc. but the major one is mostly a strictly human limitation. I found myself just listening to the same set of music over and over, or I was undecided about what I actually wanted to listen to on any particular day, and Spotify just isn’t geared up to make it easy to browse to find something you want. The tools available for finding entirely new music on Spotify aren’t really very wonderful, either.

What I could do instead with my £10 is just buy a new album (or two) every month, add it to my collection, and then use tools like Genius playlists on the iPhone to listen to the whole damn lot in nicely selected chunks, which I find a really satisfying way of consuming music. This plan also has the advantage that I get to keep all this music if I every subsequently decide to stop paying monthly.

Anyways, I haven’t made any final decisions yet, so I’d be very interested to see what other people think about this, any tips/tricks or perspectives to share would be great.

(Coming up soon: a series of posts about my holiday to Ireland, and hopefully just more posts in general…)

Yesterday Threw Everything At Me

I had kind of a crazy day yesterday.

It started with an exam in Quantum Field Theory. Painful, but I think it didn’t go too badly. Had a bite to eat, then it was straight into some last minute revision on the Queen’s Lawn for the second exam of the day in Optical Communications Physics, which was actually sort of pleasant, in a slightly strange way. Less like the hideous mental assault which constituted my other exams, anyway.

To celebrate, Rowan, Susan and I took a trip to our customary haunt — Nando’s — and proceded to consume chicken. It was delightful.

After that, I decided to take a trip into central London to grab some comics at Forbidden Planet, and as I was strolling up Monmouth Street I walked past none other than Neil Gaiman, award-winning fantasy writer and graphic novelist. By the time I’d realised it was him he’d already walked past me and gone round the corner. It took me a few more hours to realise that I was in fact carrying in my bag a copy of his “Sandman” graphic novel “Dream Country”, and that asking him to autograph it would have been incredible. I later found out via the wonder of Twitter that he would have signed it if I’d asked. Never mind!

So yeh, went to Forbidden Planet, grabbed a new Buffy comic and a Penny Arcade book, and went and sat down on a wall just up Shaftesbury Avenue and read my purchases for a while, and watched the world go by. I don’t spend nearly enough time in central London, which is a shame because I love it dearly; it’s so full of life and bustle and remarkable buildings and architecture and it goes on and on in all directions.

Rather than go home, I decided to take a bit of a walkabout. I set off east towards Holborn, passing whichever way took my fancy.

The first thing I discovered was what looked to be the entrance to an underground tramway.

A disused and gated tramway under the streets of London

I wonder how long it’s been since it was used, and where the other end of it surfaces, if it still has another end.

I wandered over to where a section of street had been blocked off by Crossrail signs. This old building, a sign on which read “The Ivy House” was abandoned, encircled by signs exhorting me to visit the site office. The building across the street bore the likeness of, and a dedication to, John Bunyan. It too looked decayed and abandoned; I turned the corner into a desolate alley, and leaned to look through some railings; through them smelt of damp and decay.

The building was apparently called “Kingsgate House”, and despite appearing to be derelict, somebody still seems to be in habitation, judging by the light and the open window.

It appears that I’m not the only one to find this building interesting.

Places like this fill me with wonder, make me think about their history, why they were built, and how they fell on hard times. I wonder if Crossrail is doing any good to this little microcosm of Holborn at the moment; I must confess that apart from the Astoria, I’d never really considered the impact the building of Crossrail would have.

I turned north, and found that Warner Brothers keeps replicas of the Hogwarts house insignia in the Foyer of their offices.

From there I wandered into a residential district, near Great Ormond Street hospital. Houses draped with the flag of St. George, people in bars, drinking and chatting, the beautiful chattering sound of people enjoying themselves wafting over the streets. I walked down an alleyway that passed through a building, joining the street through a crack in the facade of a shop. Behind this was tucked a little house, sounds of a party coming from inside.

It was getting late, so I headed in the direction of Russell Square tube station, marvelling at water fountains, and a house draped in lights for some unfathomable reason. I came across a park called Coram’s Fields. The sign above the gate read “No Unaccompanied Adults”. I thought this was marvellous.

Post-Election: A More Expert View

This article from the UK Polling Report is actually a much better guide to what might happen next than I could ever do, seeing as how it contains actual facts.

I think this bit is interesting:

The second issue is the Liberal Democrat party’s rules. Formally Cameron and Brown have a free hand in negotiations, Clegg does not. The Southport Resolution in the Lib Dem rules requires him to get the support of 75% of the Parliamentary Liberal Democrat party, and 75% of the party’s Federal executive (and failing that the support of two-thirds of the wider party) in order to enter into any agreement that “could affect the party’s independence of political action” – taken as meaning a coalition agreement. While all the leaders would in practice need to take their parties with them, only Clegg would have such a formal process to deal with somehow.

For Once, Not Politics or Philosophical Essayism

Whenever I’m not feeling OK, I have a tendency to hit the philosophy. There’s something about contemplating the essential questions of existence that makes your everyday shit seem to be much less of a concern, and more like weird background noise. I’ve finished reading Nausea, my copy of Catcher in the Rye is back on the shelf, and hopefully things will go back to something approximating normal.

I hope I’ve learned something. It was probably something I’d hoped I’d learned before, and no doubt through my own infinite stupidity will need to learn again at some point in the future, but I hope that I’ve learned it for real this time.

Sometimes things end. It’s sad, and sometimes you just can’t understand why, or make sense of what happened, but you can’t howl into the wind and try to change the past with the power of your fury; you’ll just consume yourself in hatred and bitterness and nihilism. Some things just aren’t worth the time, effort or pain trying to fight.

Time to learn to let things end.

In other news, there’s a Fairtrade Cheese & Wine party on Friday night, which I will certainly be going to, and there two events on Thursday I would like to attend but they’re mutually exclusive and I may not have time anyway: Fairtrade tea party, and ICU Election Hustings.

Act accordingly.

Andy out.