Scientists have discovered that air is heavier that we previously thought, but not by much. The rough composition of air is well known. It is mostly nitrogen (around 78 per cent) and oxygen (21 per cent). The rest is a mixture of carbon dioxide, water vapour and argon. It is the amount of argon that is key here, because the more argon present, the denser the air.

Around a century ago, scientists calculated that the amount of argon in the air was around 0.934 per cent. In 1969, this was revised to around 0.917 per cent. However, a team from the Korea Research Institute of Standards and Science (KRISS) and the International Bureau of Weights and Measures (BIPM) in France, have determined that the actual amount of argon is 0.9332 per cent, plus or minus 0.0006. The results were published in Metrologia.

In separate news, scientists in California have developed the world's strongest acid. Paradoxically, it is also one of the least corrosive. This is down to its incredible chemical stability: at its core it contains a molecule called carborane, possibly the most stable group of atoms in chemistry.

The acidity of a substance is determined by how readily it donates hydrogen ions or protons. This new acid is over 100 trillion times more acidic that swimming pool water, and more acidic than hydrofluoric acid but it won't eat through glass. ®

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