Alex's (very) occasional blog

New version. Old one still kicking around somewhere. (Views personal, etc.)

Posts Tagged ‘physics

The Wheatstone Bridge.

leave a comment »

Q corridor

One thing I missed when noting the passing of my dear old research group was the disappearance of something with a bit more history : with the retirement of the doyen of diamond science Alan Collins, went the last vestiges of the venerable Wheatstone Physics Laboratory.

Named for, as you might suspect, Charles Wheatstone, it was the home of Rosalind Franklin and Ray Gosling, also of Maurice Wilkins’s co-authors on his coincidental paper. It was the home address of an awful lot of academics for at least 60 years.

To be honest, I don’t know very much about it, other than that it was also my academic address. I assume that it used to be a physical place, rather than just a slightly fancy name. Most of my colleagues used the more prosaic ‘Department of Physics’.

It may well have come into being when they rebuilt after the war. It might have been what ended up as the old teaching lab. Or they might have just re-used the door signs.

That’s gone now too, a lovely old wooden lab replaced by a gleaming white plastic one.


Written by alexconnor

September 2, 2011 at 20:52


leave a comment »

1st generation caesium fountain atomic clock
(A caesium fountain atomic clock, from NPL’s flickr. I would bet money that they don’t need all of those mirrors on days when the photographer isn’t there.)

Simple, elegant things. Yet somehow very hard to explain. (Also prone to wonderfully spurious precision — less than a second in 138 million years !?) Getting from frequency to time is not necessarily an intuitive thing (also, frequency is a Bad Word). Many years ago, after writing the thing in the first link above, I spent an hour trying to explain it to someone. Working from analogy, getting time from distance travelled a car, was the best I could manage. Pretty sure it didn’t work.

Written by alexconnor

August 27, 2011 at 21:31

Posted in Physics, Pie, Science

Tagged with , ,

Diamonds bounce.

with one comment

It’s perhaps a little known fact, and one hard to arrive at from first principles, but is something that any young experimentalist learns within a couple of hours:  if dropped on a hard floor, diamonds bounce.  And they bounce well. Like a golf ball on a country road.

This is an occupational hazard when working with diamonds. It was not uncommon to walk into my old lab and see a professor’s backside in the air as he crawled round the room searching the for the unique sample he has been studying for the past six months. I say ‘was’, because my old group has now gone the way that all research groups ultimately do — a quick check of the dept. website shows that following the retirements of a couple of key members, it is no more.

Research groups don’t tend to be mourned, or even have their passing marked, so I’m not going to write an obituary here. Well, not really.

A diamond
Diamonds – notoriously difficult to photograph

Much of the work of the group was on understanding the properties of defects in diamond  (“blue-skies research on atomic-scale defects in the perfect covalent crystal”, as the grant application put it). This covered both the standard electrical semiconductor things, but also the optical properties :  how to change the colours of gem diamonds, and how to tell if a flawless diamond you buy from a jewellers came out of the ground looking that good.

So, kind-of esoteric, but also kind-of commercial. But legacy is more than that: the work by members of the group on the properties of the negatively-charged nitrogen-vacancy centre in diamond is being exploited in the development of single-photon sources for quantum cryptography; they are, I think, using diamond detectors in ATLAS as beam profile analysers.  I keep getting citation alerts (yes, vanity…) from the American Mineralogist.  I can’t read the papers, but choose to assume that it is seminal work they are publishing.

As for the people, amongst the usual smattering of academics, quants and investments bankers, the ‘alumni’ of the group include a science teacher and a clinical scientist(?). Also the world’s most helpful post-doc Karl Johnston appears to be heading up the solid state physics at ISOLDE at CERN.

Laboratory glamour
Lab glamour.  (I don’t seem to have a picture of the diamond lab I used – this was Shu’s one next door.)

Objectively (ish), a middle-ranking group has reached the end of its natural life – science rumbles on, and the younger researchers have found new homes (and it was perhaps enough of a slap in the face to find that, in later years, we were increasingly chasing funding from the “applied materials science” stream). Still, I do wonder what they are going to do with all those leaky, lightless rooms under the car park.

Written by alexconnor

May 1, 2011 at 21:10

Posted in Physics

Tagged with , ,

Sticks and balls.

with 3 comments


It’s not strictly accurate, but then it’s not meant to be. And in a country now ten months without a government, what better place for celebrating the approximations of bonds. It wobbles in the wind. It wasn’t designed to. Crystals aren’t meant to sway.

Before it was made, the designs were amended to include some lone pairs extending from three of the atoms to act as extra legs. If they help, they don’t help much.

Atomium was built as a symbol of unity, and progress, but it is really a spectacularly public celebration of science. Not oblique, Holbeinian science. This is Proper science. From school.

As such things always do, the last remnant of the 1958 EXPO lives in an area that was once meant to benefit from its presence; it sits on land given to the city by the ever-paternalistic Belgian monarchy. Atomium overlooks a miniature Europe theme park; by night it is the roundabout of choice for the local boy-racers.

Who knows whether it has made a difference? It is an enticing idea that the schools in the area have produced an above average number of crystallographers. Maybe they just grew up with a morbid fear of high winds.


If specifics are needed, it is nine steel spheres — one in the centre surrounded symmetrically by eight others. A body-centred cubic. 2 atoms per unit cell, 2 net lattice points (1 +1/8 . 8); a packing factor of 0.6802. It is taller than Big Ben. The spheres used to be clad in aluminium, now stainless steel.

Notable elements that have BCC structure : iron (mostly). But not aluminium (FCC).


It was refurbished recently, but it doesn’t really show. It would look rusty if it weren’t whitewashed with stainless steel. If it didn’t have the weird unphysical legs, it would’ve fallen down years ago.

I’m not sure it ever really had any glory days. The museum is dull (it’s not got much to work with: Atomium was built by un-harnessed Belgians who smoked roll-ups while sauntering across girders in the snow; it has a lift that ascends at a spine-shortening five metres per second). Sitting in the restaurant feels as though you and it are sealed within an air-tight metal ball, which you are. Most of the windows are too dirty to see out of and the escalators are frankly terrifying.

But none of this is important.

Even if it had blown down as soon as it was finished, it would still have been the only major public monument built to science. Even if visitors could do no more than sit at picnic tables at its base, it would it still be worth the trip. It is a monument to science and what it promises. But more than that, it is a monument to understanding, to what it means to understand. To what it means to be proud of understanding.

Ah, come on, just look at it.


Written by alexconnor

April 3, 2011 at 20:20

%d bloggers like this: