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

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

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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