Science: Technoquest

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Q Why does milk get a skin when it cools down?

The skin is a complex of casein, a milk protein, and calcium. It is the result of evaporation at the surface of the milk, which concentrates the proteins there. Skin formation can be minimised by covering the pan or by whipping up a little foam, both of which slow down the rate of evaporation.

Q Why do your hands go wrinkly in the bath?

Our bodies are covered with hairs, each of which has a gland (the sebaceous gland) at the bottom that pumps out sebum. This oily, waterproof layer stops water getting into our skin and keeps it supple. But the palms of our hands and our feet are hairless, so don't have this protective layer. This means that water can get into the skin of our hands and feet, and make them swell up. The skin swells into ridges because of the way the layers of skin are attached to each other.

Q Do fish hear?

Yes! Carp, particularly goldfish, are considered to be hearing experts. They have three bones, the Weberian ossicles, connected to the swim bladder; vibrations are transported to the brain. Some fishes also sing. In California some people living in houseboats heard a buzzing at certain times of the year. Rumour put it down to aliens but it was eventually found to be the noise a Micharen male fish makes to attract the females.

Q How much dung does an elephant produce?

About 150kg of dung a day - about 24 stone, or one tonne of dung a week!

Q How and why do we sneeze?

We sneeze to clear irritating material from our upper air passages. This can be dust, pollen or snuff, or excess mucus blocking the nose when we have a cold or hay fever. Sneezing is a reflex action that blasts air out at more than 100mph to clear the air passages. Pain receptors in the cells lining the upper respiratory tract are triggered by the dust or mucus and instruct the medulla (the base of your brain) to make you sneeze. The sneeze itself is just a very powerful out-breath. The vocal cords are kept shut till the pressure in the chest has risen, and then the air is suddenly allowed to escape upwards, being directed into the back of the nose by the soft palate. But the 103mph of a sneeze is nothing compared to the 600mph that a cough gets up to.

Q What is Alzheimer's disease?

The disease was first described in 1907 by a German neurologist, Alois Alzheimer, and is a form of dementia (madness) that mainly attacks older people - some 4-5 per cent of those over 65 have symptoms of it but it sometimes strikes those in their forties or fifties. It is the fourth largest cause of death, after heart disease, cancer and stroke, and there are 390,000 people with Alzheimer's in the UK; this number is likely to double by the year 2021 because the average age of the population is increasing.

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The Technoquest website is at http://www.sciencenet.