At -269°C, helium gas condenses to become a liquid. Cool it even further and it becomes a state of matter called a superfluid. In this state it has no measurable viscosity and so does some odd things, such as climbing up the walls of a dish, leaking through apparently solid materials and staying motionless while its container is spun. To create the liquid and superfluid states, you cool down helium gas to a few degrees above absolute zero. This is achieved by compressing the gas, and then expelling it through a small nozzle. As the gas expands, it rapidly cools (you’ll have noticed this effect if you’ve ever used an aerosol deodorant). The process is repeated until the gas that rushes out of the nozzle is cold enough to condense to a liquid, then if you repeat the cycle a few more times the helium will become cold enough to turn to a superfluid.
TEN SCIENTISTS WHO EXPERIMENTED ON THEMSELVES Max Joseph von Pettenkofer 1818–1901 in 1992, this Bavarian hygienist drank the diarrhoea of a cholera-stricken man in an attempt to demonstrate that the microbes became harmful only after incubating in the ground. He discovered that he was wrong. William J Harrington 1923–92 the American researcher in autoimmune disorders transfused blood from a patient with idiopathic thrombocytopenic purpura into himself, showing that the condition causes the body to destroy blood platelets. Horace Wells 1815–48 An American dentist in connecticut, Wells pioneered the use of nitrous oxide (laughing gas) in dentistry by having one of his own teeth extracted while under anaesthesia. John Paul Stapp 1910–99 the American researcher made a huge contribution to air-crash safety by testing the effects of rapid deceleration on the human body, strapping himself to a rocket sled braking rapidly from up to 1,000km/h. Nicolae Mino...
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