Wednesday, 30 July 2008

Glass in the New York Times

When people think of physics they tend to think of particle accelerators, string theory, E=mc² and so on, so when I tell them I'm studying glass they always look a little disappointed. Anyway, a couple of weeks ago we got a New York Times article from a guy called Kenneth Chang so we're all quite pleased about it. I had written a long post about it but I ended up just repeating what's in the article, so I've decided to list some main points and provide a few extra links.

He managed to give a good sense as to how much debate there is in the field. One thing everyone agrees on however, and where the article begins, is that cathedral windows do not sag because the glass has flowed.
"Medieval stained glass makers were simply unable to make perfectly flat panes, and the windows were just as unevenly thick when new."
If you want something that does do that then let me point you in the direction of pitch, which drips about once a decade but shatters when hit with a hammer. So what is glass then? Is it a liquid or what?

Glass has the same structure as a liquid. If you take a photo you couldn't really tell the difference. A liquid that's on its way to being a glass, a supercool liquid, is the same as well. If instead of a photo you look at a video you'll see that it's actually really different. Weeks and company have actually done this and you can see regions really close to one another, some with lots of motion, some hardly moving at all. This is the dynamic heterogeneity, mentioned in the article, that goes along with the hugely increasing viscosity. Their website has loads of great stuff, including movies and a link to a freely available version of the Science paper, I recommend taking a look.

The region that I'm roughly poking about in at the moment is to do with vibrations and rigidity. This is touched on in the article a couple of times. Matthieu Wyart and others have spent a lot of time developing the idea of a glass as a marginally rigid solid (the introduction to Wyart's thesis is actually quite readable and freely accessible). It's looking at how the random liquid structure affects things at low temperatures.

Anyway, I'll leave it there. If I've missed any important links just stick them in a comment. Been a bit too busy writing my thesis to do this properly. Dear God let it end soon!

Wednesday, 23 July 2008

Moving adverts

A couple of weeks ago I was in London and passing through Liverpool Street tube station. Something that I've been dreading for years has finally started; they're now projecting moving adverts on to the wall. They've had the LCD screens on the escalators for ages now, they're not great but they only fill a small part of your peripheral vision - they're after the rest.

TFL try and sell this as something great for the commuters
We believe that this technology will enhance passengers' journeys
Really? Are you sure it won't get on their nerves? Would you stop it if it did? The eventual aim is to have every pixel of your periphery flashing and shouting so that your brain is so confused with the unmanageable amount of information that you'll do anything they tell you. Or stumble in front of a train.

It's an inevitability, an arms race. If you cover every square inch in posters then, per square inch, they're all worth less. So to make your milliacre more valuable it must now move. Soon they will all move. Then they'll start shouting at you, then they'll get linked to your oyster card so they'll be calling your name. Worse, linked to your nectar card so they can chase you down the street offering you carefully selected products you might like.

Not everyone agrees with me: this advertising blogger thinks it's great and shows how hi-tech we are. TFL clearly like it. Anyone else? I'd really like to know.

I have the attention span of a pea. It takes nothing for me to lose track of what the hell I was thinking, what someone just said or even why I got on this train in the first place. Please, I'm begging, leave my poor brain alone!

Saturday, 19 July 2008

Plausible theories from experts

This posting, from the rather excellent Mind Hacks, got me all worked up again (this is quite easy to do). It just struck me how easy it is to say something plausible, for example "increasing violence is caused by computer games", and then make no attempt to check whether it's true.

In this case the plausible statement is on the use of facebook, the internet, other such things. It even managed to be press released by the Royal College of Psychiatrists. This starts off
A generation of Internet users who have never known a world where you can't surf on-line may be growing up with a different and potentially dangerous view of the world and their own identity, according to a warning delivered to the Annual Meeting of the Royal College of Psychiatrists.
Could be true. I wouldn't like to say. Things start to smell a little funny when they say
This is the age group involved with the Bridgend suicides and what many of these young people had in common was their use of Internet to communicate.
OK stop there. Now I'm suspicious, don't all young people use the internet? By the way, the Bridgend suicides are also being blamed on mobile phone masts and, for all I know, computer games. In fact it feels like there is a rather sinister trend for untested/untestable claims to be applied to these tragic events, and why? Because it will get press attention. Without a doubt.

It seems that a horrible statistical fluctuation in the all-too-large distribution of teenage suicides is not a satisfying reason for the media or the public. And this leaves the door wide open for "experts" to fill the gap.

It's just too easy to say you think something is true and then press release to an unquestioning media. A classic example is the evolutionary psychology stuff (badscience has lots on this). These are the claims that we will split in to two distinct races or that we will evolve big willies. The papers just say that "Experts say..." washing themselves of responsibility. But who are these experts? Many of the proposals are plausible but that's not enough.

I could spend all day coming up with things that could be true. Unless it is testable then what use is it? Physicists come up with plausible theories all the time, but no one will get the nobel prize until it can be tested. The famous Feynman quote goes
"It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."
I appreciate that physics experiments are much easier (and by that I mean controlled) than social experiments, but that's no excuse for claiming you have the answer when all you have is a plausible explanation. It's a massively important distinction.

To anyone claiming to know the cause of the Bridgend suicides I beg you to think carefully; teenage suicide is a serious problem and they deserve much much better.

Edit: Here's the BBC coverage

Saturday, 5 July 2008


Ok, a bit of proper science to try and establish some balance. This is a bit of a lazy post but I did mention I'm busy writing my thesis. On supercooled liquids...

Supercooled water is just water that is below its freezing point but for one reason or another didn't crystalise. It's a form of metastable equilibrium. If you give it a big enough kick then it can escape and this happens

And you can do it with beer

If you keep cooling it further then you eventually get glass, and that's all glass is. Now my stuff is more interested on the supercooled goes to glass bit rather than freezing beer but you get the idea.