woodchurch science

you’d probably be surprised to hear that there are loads of science references in numerous episodes of the simpsons, from homer’s time travelling toaster to principal skinner’s riposte on a visit to a private school, ‘hmmpf! due to school board cutbacks OUR periodic chart only has 15 elements….and they’re all lanthanides!” there are plenty more here including my favourite…see if you can spot it.

water is known as a newtonian fluid, because it continues to exemplify fluid properties no matter how fast it is stirred or mixed. i.e. its stress/strain curve is linear and passes through the origin. The constant of proportionality is known as the viscosity.

contrast this with a non-newtonian fluid, in which stirring can leave a “hole” behind, that gradually fills up over time – this behaviour is seen in materials such as rice pudding. non-newtonian fluids can also become thinner, the drop in viscosity causing it to flow more. this behaviour is often referred to as thixotropy. the opposite behaviour (getting thicker the more you shake it) is rarer and is referred to as rheopexy.

two classic examples: a thixotropic (sometimes called a pseudoplastic) liquid like tomato ketchup gets thinner the more you shake it, and a rheopectic (sometimes called a dilatant) liquid, such as non-drip paint, brushes on easily but becomes more viscous when on walls.

another example of a non-newtonian fluid can be made very easily by adding custard powder gradually to a cup of water. the so called “shear thickening” property of this non-newtonian fluid soon becomes apparent. the application of force – for example by stabbing the surface with a finger, or rapidly inverting the container holding it – leads to the fluid behaving like a solid rather than a liquid. More gentle treatment, such as slowly inserting a spoon, will leave it in its liquid state. trying to jerk the spoon back out again, however, will trigger the return of the temporary solid state. a person moving quickly and/or applying sufficient force with his feet can literally walk across such a liquid.

shear thickening fluids of this sort are being researched for bullet resistant body armour, useful for their ability to absorb the energy of a high velocity projectile impact but remain soft and flexible while worn.

a spaceman bakes a cake in his spaceship then launches it out of his spaceship window. how long will it take to cool down?
secondly if he could collect it again say six weeks later would it be safe to eat? any thoughts leave a comment.

above is a picture of a bottle of caproic acid (or hexanoic acid) that has a very distinctive odour. see it’s entry in the merck catalogue alongside: now what exactly is ‘goat-like’? seems you’d have to be overly familiar with barnyard animals to recognise that as a smell.

the website, visions of science has a collection of photographs connected with science. the awards are sponsored by the daily telegraph but this years competition is now closed but you can look at the winners and runners up. categories include: action, close-up, people, concepts, art, einstein year award, art meets science and the young photographer awards. well worth a visit.

the smelly substance in excrement is skatole (3-methylindole), and it is the substance to which the human nose is most sensitive on a per molecule basis. no doubt it is present in faeces because it is a breakdown product from haemoglobin that enters the gut via bile. we have evolved to be repelled by it because excrement transmits disease and we should steer clear. however, skatole doesn’t always trigger the disgust reaction in humans, nor is the reaction shared by the whole animal kingdom. the substance is used in small amounts as flavouring in food, notably in vanilla ice cream. Dung flies are attracted to it, and the phallus-like spadix of the arum lily (zantedeschia aethiopica) synthesises skatole to attract flies that pollinate the flowers. the civet cat also has glands that produce skatole, presumably to mark territory and repel others. this gland is used in perfumery.

in 2005 all uk schools and colleges received a copy of bill bryson’s book ‘a short history of everything’. bill bryson has generously donated his royalties from these sales to establish a schools science communication award. the prize is for science communication in its widest form – entries can be submitted in any format; word doc, powerpoint, web page. all levels of pre-university education are eligible. judging will be in two categories: primary school and secondary school. prizes of up to £1,000 will be awarded to the best entries and the closing date is 31 May 2006.
for more information and an entry form, please click here.