Large Hadron Collider can be ‘world’s biggest rain meter’

The LHC ring is 175m below the surface in places

The LHC is not just the world’s most powerful particle accelerator, it could also be its biggest rain meter, scientists say.

They are investigating tiny changes in the length of the collider’s 27km-circumference ring, which occur on a daily and a seasonal basis.

The short cycle is explained by normal tidal forces.

But the winter-summer pattern which affects the huge underground facility is not so obvious.

Except researchers think they can now show that winter rain and snow is gravitationally pulling on the ring.

“My hypothesis is that in winter there’s a lot more water in the ground, and even snow sitting on the ground. So, basically, this mass pulls on the ring. And when that extra mass melts away and evaporates away in summer – the ring stretches a bit,” said Rolf Hut from Delft University of Technology, Netherlands.

If that’s true, you could use the LHC to study precipitation and other aspects of hydrology – not just the secrets of the Universe.

I can make a rain gauge out of anything,” said Dr Hut. He was speaking here at the European Geosciences Union General Assembly.

Space sensors

Changes in the size of the LHC’s ring are known from the behaviour of the beam of particles whizzing around inside it at near-light-speed.

The length of the particles’ orbit is fixed and controlled by the collider’s operators such as to position the beam in the centre of the ring’s vacuum chamber.

An alteration in the circumference will force the particles to move inwards or outwards relative to this centre point.

This movement can be measured with micrometre accuracy and is corrected. The adjustments made by the operators therefore represent a very precise measure of the change in the circumference of the LHC.

This issue was first noticed in the LEP accelerator, which occupied the mighty tunnel under the Franco-Swiss border before the LHC.

The daily changes were quickly attributed to the flexure of the surrounding rock by the Moon’s tides, but the longer seasonal cycle could have a number of explanations.

One of these is the change in temperature between summer and winter months: the rock could simply be flexing as it warms and cools. Except, temperatures ought to be pretty stable at the ring’s depth, which can reach 175m below the surface.

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