IN 240 BC, it took all of Eratosthenes’s ingenuity to estimate the circumference of the Earth within 10 per cent of the correct value. But students today can achieve a comparable level of accuracy using the Internet, a globe and a piece of string.
Key to the trick are the optical fibres along the seabed between major Internet nodes such as Seattle and Hawaii. Signals travel along these fibres at roughly two-thirds the speed of light, so if you know the time taken, you can deduce the distance travelled. If you then take a globe and stretch a piece of…
