woodchurch science

in a view to a kill james bond is left for dead in a lake by some villains. but instead of floating to the surface he remains underwater breahing air from a car tyre through the valve! is this really possible? what do you think?

is this right? should scientists be doing this? what do you think?

gareth earnden of 10yz has asked how the sugar particles are held together in sugar lumps. suppliers of sugar cubes make them by mixing sugar crystals with sugar syrup. they were invented in 1841 by jakub kryštof rad.

we’ve been talking about luminous and non-luminous objects and james from 7x asked how night vision goggles work. they function in 2 ways: (a) image enhancement - this works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image and (b) thermal imaging - this technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.

thanks for the question james, hope this answers it.

the blue color of the sky is due to rayleigh scattering. as light moves through the atmosphere, most of the longer wavelengths pass straight through. little of the red, orange and yellow light is affected by the air. however, much of the shorter wavelength light is absorbed by gas molecules. the absorbed blue light is then radiated in different directions. it gets scattered all around the sky. whichever direction you look, some of this scattered blue light reaches you. since you see the blue light from everywhere overhead, the sky looks blue.

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.

we’ve been talking about batteries in year 9 today. someone asked how rechargeable batteries worked, so here’s this months prize puzzle. please send ideas, links etc of how rechargeable batteries work to me using the comments button. a prize to the most thorough answer.

francium was discovered in 1939 by marguerite perey. it occurs as a result of actinium’s alpha decay and can be artificially made by bombarding thorium with protons. it is the heaviest alkali metal. even though it occurs in uranium minerals, it has been estimated that there is only 20-30g of the element present in the earth’s crust at any one time. no weighable quantity of the element has been prepared or isolated. it’s the second rarest element in the crust, next to astatine. it is also the most unstable element.

a small number of pictures of francium have been taken, but only of at the most 350,000 atoms at a time. the images were made by trapping the atoms and using a special fluorescent imaging camera. the atoms were produced by a nuclear transformation with a particle accelerator. the nuclei last for typically three minutes, and must be trapped and observed before they decay.

(and no, we haven’t got any in school, and if we did we wouldn’t put it in water, you’ve seen what potassium does, just use your imagination as to what Fr would do!!)

these ancient buildings are made of limestone. why do you think the egyptians needed to build pyramids if they wanted to build high buildings?

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.