A plan has been dreamed up to send a probe to the centre of the Earth. It would travel down through a crack in the ground inside an immense lump of molten iron, pulled through the crack by the force of gravity.
The grapefruit-sized probe would reach the Earth’s core after about a week and send back data on temperature, pressure and chemical composition via high-frequency seismic waves (Nature, vol 423, p 239). David Stevenson at Caltech in Pasadena admits that his suggestion is “slightly tongue-in-cheek” and faces massive engineering and funding challenges. But he points out that while space probes have sent…
