It would take you 38 minutes to fall through the centre of the Earth

A Canadian physicist has calculated exactly how long it would take to fall through an imaginary tunnel from one side of the Earth to the other.

The concept of a "gravity tunnel" has puzzled undergraduate students for years, with most physicists estimating that it would take precisely 42 minutes and 12 seconds.

However, publishing a new paper in the American Journal of Physics, Alexander Klotz of McGill University has shaved four minutes off that time.

This was a bit of a surprise to me. Basically, the way the Earth is structured, the gravity increases slightly as you go deeper towards the dense core, to about 110 per cent of its surface value, before getting weaker as you move through the core, reaching zero at the centre.

• Alexander Klotz

By taking into account the different densities of the Earth's geological layers, he calculates that the subterranean traveller would reach speeds of up to 8km per second - 23 times faster than the speed of sound.

Intriguingly, the journey between the British Isles and New Zealand (approx. 8,000 miles) would be quicker than travelling between the British Isles and somewhere like Morocco (1,300 miles).

Klotz, who described this finding as "one of the most counter-intuitive results in classical physics", explains the theory by likening the "gravity tunnel" to a water slide.

Connecting two very distant points, the traveller would slide quickly at a steeper angle, whereas with the much nearer points they would slide slowly at a comparatively shallower angle.

HT: The Times (£)

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