Here’s another aeroplane blog entry. I noted at Gatwick Airport in London that a well-known budget airline was proudly saying that there was no weight limit on cabin baggage – all it had to do was be less than a certain size – "If it fits in the box – it goes on the plane", or words to that effect. The allowed size I estimate to be about 50 cm x 40 cm x 30 cm, a reasonable-sized cabin bag. So my immediate thought as a physicist is just how much weight could I stuff into it.
That’s a volume of about 60 litres. So the first step would be to fill it with water. A bit more than 100 millilitres, so highly illegal, but let’s pretend we can get it through security. Water has a density of 1 kg per litre (depends slightly on temperature) so that gives us 60 kg – a small adult. A fair start, but I reckon I can do rather better. Lead has a density of about 11 kg a litre, which makes our cabin bag a cool 660 kg. Try lifting that one.
But lead is a bit of a feeble filling really. Substitute if for gold, at 19 kg a litre, and we’ve broken the 1000 kg mark. The trouble is, 1140 kg of gold (about 36 000 troy ounces at about 900 US dollars a troy ounce) will set me back around 30 million US dollars – if I had that kind of money I wouldn’t be travelling with our budget airline.
Gold is up there with the densist of elements, but to really test our airline’s claims I’d purchase 1357 kilograms of Osmium to take with me.
(Before anyone tries it, you should note that the airline’s promise comes with a little asterisk, leading to a footnote that says "within reason". Shame.)