Wednesday, 30 April 2008

Which science books would you recommend?

A friend of mine just linked to 20 Science Books Every Scifi Fan (and Writer) Should Read. (By the way, I found his link not on his weblog or via an email but from his del.icio.us bookmarks. If you don't know del.icio.us, check it out: it's a great way of sharing web pages and blog posts that strike you as important — social bookmarking.)

Which science books would be on your 'must read' list? Post suggestions here in the comments and also consider cross-posting to the SPS Book Forum.

Monday, 21 April 2008

Exclusivity and Demand

I was talking to a Professor of physics from Imperial College the other day and he mentioned that a few years ago they increased their 'standard offer' of A level grades required to get in from AAB to AAA. The effect on applicants was a marked increase*.

It's an example of the exclusivity effect - you can make something more desirable simply by pricing it higher. I first thought about it when motorcycle touring in America in the 90's. Sitting in a cafe in Sturgis during a huge rally (quarter of a million bikes in the area for the week) I found myself chatting to a typical Harley-Davidson owner. Typical of the time that it - mid 40's, overweight and a gynecologist. In order to buy a new Harley you had to put down the full cost (about $28000 back then) in advance and then wait 18 months for the factory to build your bike. Second hand bikes were more expensive than new! This approach had turned around an ailing company playing out the last chords of a sad threnody and started a whole new movement of a whole new symphony. Harleys were cool, desirable and hard to get hold of.

Obviously it's a dangerous line to tread - annoy your customers by not delivering and you're dead. But it worked there and it has worked for Imperial.

We've seen it again recently with the Ford Mondeo vs the BMW 3 series. Obviously the main objection to the Mondeo is that they are everywhere - everyone drives one. So it'd probably do BMW's sales no good at all if people found out that the BMW 3 series now outsells the Mondeo...

I see something of an analogy here with physics. Make a subject accessible to all and you risk driving away students and teachers who value it for its lack of appeal to all - not a snobbish exclusivity, not a "I'm in the physics club you're not" but a simple pride in being able to solve problems and work in a way which others cannot, and so make a genuine contribution to society and the economy. Do we really want Ford Mondeo physics? Or BMW physics? And is it possible that, if we offer BMW physics, it might actually appeal more widely?

* His claim, which is anecdotal, was that applications doubled.

Thursday, 17 April 2008

Engineering at University

On Wednesaday (16th April) I was at a meeting organised by the Education Group of the Institute of Physics. The purpose was to inform physics teachers about what engineering and materials science courses are like and what the universities are looking for. After all, most physics teachers studied physics, not engineering (with some noteworthy exceptions!) so don't really know what engineers are looking for.

The answer appears to be three things:
  1. Maths
  2. Teamwork
  3. Problem solving
If engineering could be summed up in a nutshell (it can't, nothing can except perhaps the kernels of nuts) it would be that it is about developing adequate models of systems given insufficient information and the possibility that the maths is not solvable. The model has to do the job of being sufficiently applicable to the real world to solve a real problem.

What the lecturer from Oxford pointed out was that engineering is not plumbing, wiring and tinkering with motors. Nor is it repairing TVs or operating lathes. It's a profession. And if there's a problem with A levels at the moment it is that the link between maths and physics has disappeared - and physics has become too hand waving.

Engineers are clearly vital for our future and unemployment amongst them is near enough the square root of diddlysquat but we cannot fulfill the need without teachers knowing what universities are looking for.

In another talk it was pointed out than in Birmingham alone there are 151 different schemes about engineering for school kids. How are you meant to sort, select and know which are useful?

Saturday, 12 April 2008

The Strange Case of the BumbleBee which Flew

This is a piece I wrote about 12 years ago for a science writing competition (it won first prize). I thought about editing it up and correcting some bits but feel it should just stand as it was, for posterity.

I get many strange reactions from people when I tell them I am a scientist. Frequently I'll be told by my new acquaintance that they were hopeless at science at school, or I'll be asked if I make atom bombs. People, it seems, are frightened of science, so they take every opportunity to belittle it. They'd like to believe that science is all very well in the lab, and for making bombs, but it doesn't apply to "real life". Michael Flanders summed it up beautifully when he said that he cannot understand scientists and they cannot understand anyone else; they must be spoken to in their own language: "H2SO4 Professor! Don't synthesise anything I wouldn't synthesise! And the reciprocal of pi to your good wife!". Like most great humour, painfully close to the truth.
One favourite subject people raise is the old line about scientists having proved that the bumble bee cannot fly, a much-beloved piece of urban folklore. There it is, the humble Bombus Terristris, plainly flying around us all through the summer and those crazy know-all scientists with their noses in their test-tubes say it cannot possibly fly. What utter nonsense! It is obvious to any scientist that the bumble bee can fly as experiment proves it. So what is this business about proving bees cannot fly? And who started it?
First let's look at the physics behind the story. If you are asked about flight the first thing you do is to use the equations which describe how much lift an object has. You compare the lift to the weight of the object. If the lift is greater than weight then the thing can fly. Bumble bees are pretty big, weighing almost a gram, and have a wing area of about a square centimetre. Tot up all the figures and you find that it cannot generate enough lift at its typical flying speed of about one meter per second. But that doesn't prove bees cannot fly. It proves that bees with smooth, rigid wings cannot glide. Experiment has proven this too. With the aid of dead bees and a little lacquer it is easy to show that they really cannot glide.
So how do they fly? Actually that turns out to be a very interesting question and one that reveals a lot of physics. Why do bees flap while jumbo jets have fixed wings? It is a question of size and this is revealed in a figure called the Reynolds Number. Osborne Reynolds was a Victorian engineer who was interested in what happens when you place an object in a stream of liquid or gas. The number named after him is a ratio which tells us, for a particular object, how much lift you get compared to how much drag or resistance you get. A low Reynolds number means little lift for a lot of drag and a large Reynolds number means a lot of lift. The Reynolds Number depends on the size of the wing. Bigger wings give bigger Reynolds numbers. Now if, again, you put in all the numbers you find that bees work at very low Reynolds Numbers (1000 or so for a honeybee, as little as 15 for the aphid-eating chalcid wasp). This means that their flight is very inefficient because as a wing starts to move to create lift the drag holds it back. It is fairly straightforward to show that birds can generate enough lift to fly once they are in motion with air flowing smoothly over their wings, but many of them would have great difficulty taking off. Small insects, according to this model, cannot fly at all. Of course, all this proves is that the model is incomplete.
Some brilliant work by Torkel Weis-Fogh has shown us how small insects do fly and it has led to some rather neat insights into nature's cunning. If you are small and want to fly you have a problem. The Reynolds Number is against you so you cannot glide and flapping is very hard work. A wing is a device which encourages the air to flow over it so that when it leaves the rear wing edge, the air moves downwards. That produces a thrust upwards on the wing. A smoke-filled wind tunnel shows this beautifully with curling eddies of smoke flicking off the wing edges. Unfortunately to make a good eddy takes time. The wing has to move a few times its own length to get things started. This makes it tricky if you are going to flap as the maximum travel of a wing is about its own length and very little lift is generated for most of the stroke. Nature has come up with a number of interesting solutions to this problem of which the "clap-fling" is a good example. When a small bird or insect wants to take off it needs a lot of lift. What it does is bring its wings together above its back so they clap, expelling air from between them. As the wings are separated, air is drawn quickly in to fill the void. The wings are flung apart and lift is generated immediately as the air is already in motion in the correct way. You can hear the clap. The characteristic whirring of a pheasant taking off is caused by its wings clapping. Almost 2000 years ago Virgil recorded in The Aeneid that a rock dove claps its wings as it takes off - a passage he stole from Homer but he added the bit about the clapping.
So in asking how bees fly we find that they are remarkably clever about it. Aircraft can generate enough lift that they do not need such tricks, but they do need long runways. Birds get enough lift to fly but for take-off need a boost. Just the poor old bee and about a million different species of winged insect need some extra trickery to stay aloft. But how did it all start? Where does the story date back to? J.H.Mcmasters states that the story was prevalent in the German technical universities in the 1930's, starting with the students of the aerodynamicist Ludwig Prandtl at Göttingen. The story he tells is that a noted Swiss aerodynamicist, whom he does not name, was talking to a biologist at dinner. The biologist asked about the flight of bees and the Swiss gentleman did a back-of-the-napkin calculation of the kind I described. Assume a rigid, smooth wing and so on. Of course, he found that there was insufficient lift and went away to find out the correct answer. In the meantime the biologist put the word around, presumably to show that nature was greater than engineering, and the media picked it up. The truth, as now, wasn't newsworthy so a correction has never been publicised. The man on the Clapham omnibus, therefore, continues to tell me that science is a load of crock because it once proved that bumble bees cannot fly. And he will not hear otherwise, especially not from a scientist. Perhaps if I became a journalist he might listen?

Sunday, 6 April 2008

Computing Post

So we all know Physics is cool, and lots of nice photos demonstrating interesting phenomena always makes for good blog reading, but I thought I'd throw in my hand as a proponent of the interesting world of Computing with a link to this article from Neatorama, basically outlining some of the history of early computers, dating right back to about 33000BC!
So it may not be as pretty as a green sunset, but I still reckon it's pretty interesting.
Check out the link if you want to find out more.

Oh and just to keep it colourful, here's a photo of the Antikythera Mechanism. Made in around 100BC it is thought to be part of a system for calculating the motion of the sun and the moon.

Wednesday, 2 April 2008

A physicist on holiday

Well, a typical physicist on holiday - a week in the Maldives scuba diving and what do I take photos of (apart from fish, turtles, rays, sharks and coral)?


A glory, a rising red moon, the green flash and vertically-pointing satellite dishes. The first image is of a glory or anthelion. This one was taken from a seaplane, looking down onto the clouds. In the centre you can see the shadow of the plane and surrounding it are coloured rings. These arise from the sunlight being scattered back from the water droplets and, like in a rainbow, the refraction of the light through the water splits it into colours.

The second image is of the setting sun. Actually the sun set a moment before. Alright, about eight and a half minutes before if you're being fussy. As the sun drops below the horizon you occasionally see a green flash of light. Here I was lucky enough to catch it on ccd. (Damn that doesn't sound right, but it wasn't captured on film so what doyou say?). The atmosphere scatters the blue end of the spectrum (which is why the setting sun looks redder) but the red light is refracted least. After the sun is actually below the horizon you can still see it because the atmosphere acts like a lens, curving the light of the sun towards us. Red is curved less than blue so the red sun disappears before the blue. But blue is scattered more than red so blue is blocked by the atmosphere. That leaves green as the last light you see. It's meant to mean good luck if seen from Ireland or Scotland - either Celtic legend or wry acceptance of the chances of clear weather and a calm, flat sea...


Here the rising moon appears quite red. No I didn't photoshop it! It has only just cleared the horizon and, as it is fairly full (waning gibbous) it rose not long after sunset. The first reflected light to hit it is the red light of the sun - red because of the path back and forth through our atmosphere scatters so much of the bluer light. As it gets higher, it gets whiter. I've never seen this before - not been around on a clear enough moon rise I guess, sufficiently far from light pollution.












This last picture is of the various satellite dishes on the island. Being just a few degrees north of the equator, the two dishes pointing to geostationary satellites are, of course, nearly vertical. If you walk down pretty much any street you'll see arrays of satellite dishes for TV, all pointing the same way. In the UK it'll be pretty close to south because of the position of the relevant satellite. Here you can tell your latitude by the angle of the dish. I thought it was worth recording, but perhaps I'm easily amused...
If you want to know more about glories, sunrises and a huge range of optical phenomena then you couldn't do better than Marcel Minnaert's "Light and Colour in the Outdoors".

KPZ