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How many helium balloons would it take to make me float? © Getty Images

How many helium balloons would it take to make me float?

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Up, up and away! Unfortunately, this is not an experiment you would be able to try at home... let alone on your house.

Asked by: Stephen Sykes, Nuneaton

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At standard temperature and pressure, helium weighs about 0.18g/litre, and air 1.29g/litre. The difference is what a litre of helium should lift: 1.11g. So 1000 litres lifts a little over a kilogram, and a 70kg human needs around 70,000 litres: very roughly 10,000 normal balloons, or approximately 300 of those party balloon cylinders at supermarkets. ‘Cluster ballooning’ aficionados use 50-150 balloons, each larger – over a metre wide – than a standard balloon. Not one to try at home though.


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