Page 11 - BBC Knowledge - October 2017 IN

HOW IS HELIUM TURNED HOW DO HOUSEHOLD
INTO A LIQUID AND CLEANING PRODUCTS
A SUPERFLUID? AFFECT THE ENVIRONMENT?

At -269°C, helium gas condenses to become a liquid. Cool it even Even after passing through water treatment plants, small
further and it becomes a state of matter called a superfluid. In this quantities of chemical compounds from cleaning products
state it has no measurable viscosity and so does some odd things, can find their way into rivers, ponds and lakes and have adverse
such as climbing up the walls of a dish, leaking through apparently effects on aquatic life. Phosphates in laundry and dishwasher
solid materials and staying motionless while its container is spun. detergent have a fertilising effect, triggering the widespread
To create the liquid and superfluid states, you cool down helium growth of algae that saps away the water’s oxygen, reducing
gas to a few degrees above absolute zero. This is achieved by biodiversity. By reducing water tension, surfactants allow other
compressing the gas, and then expelling it through a small nozzle. pollutants in water bodies to be absorbed more easily by plants
As the gas expands, it rapidly cools (you’ll have noticed this effect and animals. Many other compounds can be toxic to wildlife,
if you’ve ever used an aerosol deodorant). The process is repeated or affect growth and reproduction, for instance by mimicking
until the gas that rushes out of the nozzle is cold enough to the effects of hormones in mammals and fish. AFC
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. ML

TH E TH O U G HT E XPERI M ENT

WHAT WOULD HAPPEN IF ALL EARTH’S INSECTS VANISHED?

PHOTOS: GETTY X5 ILLUSTRATIONS: RAJA LOCKEY 1. Food chain collapse 2. No pollination 3. Less Insecticide

Most non-marine food chains depend on
On the plus side, if there were no longer
Of the world’s food crops, 75 per cent are
pollinated by insects. Without insects,
any insects, we wouldn’t need the 430,000
insects. Almost all birds eat insects, and
tonnes of insecticides that are sprayed
we could still grow many foods, but onions,
even those that eat seeds as adults still feed
cabbage, broccoli, chillies, most varieties of
onto crops every year. In the US, pesticide
insects to their young. It takes 200,000
residues cause between 4,000 and 20,000
insects to raise a swallow chick to adulthood.
tomato, coffee, cocoa and most fruits would
cases of cancer each year, according to
be off the menu. So would sunflower and
Insects also break down plant matter and
the National Academy of Sciences. But this
help recycle nutrients into the soil. Without
rapeseed oil. Demand for synthetic fibres
any insects at all, most bird and amphibian
is a small compensation for total ecological
would also surge because bees are needed
collapse and global famine.
species would be extinct in two months.
to pollinate both cotton and flax for linen.
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OCTOBER 2017