About me

For my professional website, with information about my research, publications and teaching, see www.sites.google.com/site/rmlevans.

Sunday, 19 February 2012

An A-level eye-opener

There is a general perception that A-levels ain't what they used to be. In my young day, when the world was right and the sun shone all summer and the streets were paved with orphans who were grateful for the work, that's when an education was a real education. You couldn't pass a physics exam by drawing a picture called "How I feel about electrons". The youth of today blah blah blah rant foam (to paraphrase the Daily Mail).

For those not conversant with the UK system, A-levels are "Advanced level" exams, usually taken at age 18, and required for entry into university. We university physics lecturers see the results of the school education system and, based on our impressions of each year's freshers, we too make assumptions and guesses about the state of the A-level system.

All the physics lecturers in the house say, "hey!"

I can't hear you! It's always important to have an idea of the audience for whom one is writing and, in my own experience of a normal working day, I've noticed that most adults are university physics lecturers, but I'm willing to entertain the possibility that my experience might not be entirely typical. Well, even if you happen to be one of those non-physics lecturers that I've heard about, the current standards of education are obviously important to you too because (a) you don't want your own hard-won qualifications to be devalued, and (b) today's schoolchildren will soon be building nuclear power stations, fighting world-hunger, and cleaning the dribble from our wrinkled chins.

So, you might be interested to know that, rather than continuing to speculate about A-level standards, last week I went to see for myself, spending a day sitting-in on science lessons at South Cheshire College, at the kind invitation of Head of Physics, Dr Phil Klein. It's a Further Education college teaching A-levels, vocational training and adult HE-access courses to a vast number and variety of learners. My first impression of the college's two-year-old £70M building was that it felt simultaneously light and spacious yet intimate and comfortable, and this was a triumph of design, considering that the institution was way bigger than any school or FE college I had previously visited. If its role-call of 300 doesn't sound huge, that's because it's just the number of teachers.

But there was no hint of the enormity of the place, or of the social deprivation in surrounding catchment area, as I attended the calm, orderly lessons in which the teachers had a friendly rapport with each of the dozen-or-so students. The first lesson, A-level physics, was closest to my heart and the main purpose of my fact-finding mission.

I had arrived with an open mind, but must admit that I expected to be horrified by a superficial syllabus, much diluted since my own sixth-form career in the late nineteen ahem-ties. (Excuse the frog in my throat; it's decrepit.) My smugness was instantly crushed, as I was confronted by a discussion of nuclear decay pathways that had me dredging dim memories of undergraduate lectures. Far from being watered-down, the syllabus has been extended to include serious stuff about subatomic particles and astrophysics. Meanwhile, I was delighted to discover that the vital foundations of the subject have not been abandoned; Newton's laws of motion, force balance and discharging capacitors are still covered in rock-solid fashion.

"It's all very well optimistically writing these topics into the national curriculum," I hear you say, "but do the bright young things actually understand any of it?" The exchanges that I witnessed, between teacher and pupils, convinced me that, within those Cheshire walls at least, there was no shortage of expertise. For instance, having worked though some algebra on the whiteboard, the teacher asked the class, "What's the best way of plotting a graph to demonstrate a power-law formula?" and I was impressed when several of the youngsters simultaneously replied,

"Log-log plot." In case that phrase is not redolent with meaning for you, I should point out that they were right, and that the log-log plot, while being one of the most useful weapons in a scientist's arsenal, is not at all straightforward to understand.

It would be misleading to claim that the future of sixth-form schooling is entirely rose-tinted. There are two blots on the exam boards' copy sheets, of which everyone who has followed their progress over the last twenty years is aware. The first is the well-known and undeniable phenomenon of grade inflation, that was an inevitable result of taking the exams business out of the hands of University boards, and into the mitts of profit-making companies, that tout for trade on the basis of their results.

The second is a subtle change in the nature of physics A-level exam papers that worries those of us who pick up the teachers' baton at university. The questions are still of the same standard and depth as ever and, as I say, of even greater breadth. But the answers, which used to be written on simple A4 lined paper, are now written into a pre-printed booklet, in which the appropriate diagrams, construction lines, and general shape of the answer have already been sketched out. This leaves the student with no opportunity to practise the crucial skill that we physics-types call "problem-solving". That is to say the spark of insight and invention required to take the cryptic description of a problem, choose how to approach it, and convert it into a sketch and subsequent calculation. The young people I met last week undoubtedly had the nous to find their own way to solve complex problems, but need to be given more practise at this skill during their formative years at school. In spite of this fly in the ointment, it filled me with relief and optimism to see such motivated, self-disciplined and well-informed A-levellers.

Saturday, 4 February 2012

Black holes and the history game

When we’ve exhausted “I Spy” and “Twenty Questions”, my six-year-old son and I sometimes play a game that we invented. It’s a kind of quiz that exercises both our brains. I realise I’m in danger of coming across as one of those pushy, neurotic parents who forcibly over-educate their offspring to prove their superiority and give them a head start in the rat-race. But, cross my heart, we play purely for the fun of it.

Here’s how the game works (and, if you have sprogs of your own, you’re welcome). You, the grown-up, play the role of question-master. Think of three events, inventions or discoveries. Say them in a random order and, if necessary, explain what each one is. Then your diminutive descendant just has to put them into chronological order. Not convinced? Believe me, it’s a lot more fun than it sounds.

Let’s have a go. (Follow the links for clues to the answers.)

- This one won’t tax an adult, but it makes an interesting conversation point. Whether the apple of your eye gets it right or wrong, you’ll probably end up discussing dragons and castles until one of you falls asleep, and forget the rest of the game.

- Yes, they all still exist, but which was invented first? Again, this one’s not exactly challenging, but it might surprise your playmate, especially to learn how very long the first one was invented before the other two.

- Starting to work the grey-cells now?

(4) The wheel; the plough; fire.

- This one will almost certainly surprise the younger player, for whom all three inventions belong to ancient history.

Did you get them all? Congratulations. Now, here comes the tricky one.

(6) Stars; galaxies; black-holes.

Until recently, physicists thought we knew the answer to this one. In the early universe, gravity made hydrogen clump together into big dense regions (proto-galaxies) where stars formed, fusing hydrogen nuclei into helium, and releasing energy. Once those stars had exhausted their hydrogen fuel, they collapsed and, if they were huge enough, kept on collapsing right down to zero size, forming a black hole, where gravity is so intense, it breaks space and swallows light.

That's how we thought it worked, but it was all just conjecture. In fact, we weren't even confident that black holes existed at all. A black hole was a possible solution to the “field equations” of General Relativity, Einstein’s theory of gravity, but there was no evidence of them until the discovery of active galaxies in the 1950s. It became clear that something at the heart of many distant galaxies was firing out incredibly energetic jets of matter and radiation and, because the intensity of the jets was observed to vary quite rapidly, the source had to be something tiny compared with the galaxy. A swirling vortex of gas around a black hole seemed like the only possible culprit. Still, this evidence wasn’t completely compelling. Finally, at the end of the twentieth century, detailed observations of the rapid orbits of stars at the centre of our own Milky Way galaxy settled the debate. Just watch the time-lapse movie of the observations collected between 1992 and 2005 to be convinced that an incredibly massive body is tugging those stars with huge gravitation force. Their motion tells us that the invisible object has a mass 3.7 million times that of the sun, but is much smaller than the orbit of the Earth.

More recently still, astronomers have discovered that most if not all galaxies possess such a super-massive black hole at their centre, and that these black holes could not have formed by the unpredictable chance collisions of stars within the galaxies, because there is a perfect correlation between the size of the galaxy and the size of the black hole. In other words, if you measure the size of the black hole, you can predict exactly the size of the galaxy surrounding it. This suggests the possibility that the black holes were there first, and actually caused the galaxies to form around them, by their gravitational pull.

To add to the mystery, data collected by the Hubble Space Telescope in 2011, to appear in Astrophysical Journal, reveal that supermassive black holes existed in dwarf galaxies in the early universe (as seen by observing very distant galaxies, in order to look back in time). So, perhaps supermassive black holes have always been there. They may be older than any galaxy and, if so, may well have been created at the dawn of time, in the big bang.

It seems such a straightforward question whether black holes, stars or galaxies came first, but the more we learn about the universe, the more it surprises us. The new evidence by no means settles the matter; it only proves that we have not yet understood how or when black holes and galaxies formed.

In case you’re wondering, my six-year-old’s answer was: stars then galaxies then black holes. At the moment, it’s as good a guess as any.