Scientists want to build a billion tiny pendulums to find dark matter

Stars and the Milky Way are seen on the Navajo Nation in Hidden Springs, Arizona (REUTERS)

Scientists have suggested building a network of a billion pendulums that could together finally find dark matter.

Despite the fact that dark matters makes up some 27 per cent of the universe – far more than the 5 per cent comprised of the ordinary matter that we can see – it remains almost entirely mysterious. Scientists know that it must exist because of its effects on the universe, but it can only be examined indirectly, and is invisible.

But the new research would aim to look for dark matter by looking at the way that its gravity interacts with normal matter. Rather than examining that on the grand scale of the cosmos, they hope to do so by looking for dark matter particles with the mass of a grain of salt.

Previous attempts to look for evidence of dark matter on Earth have focused on a particular kind of dark matter known as WIMP, or weakly interacting massive particles. The search has focused on detectors that watch for those particles through collisions with chemicals, which would emit light or electric charge – but no definitive evidence has yet arrived.

Now researchers at the US National Institute of Standards and Technology, or NIST, have proposed a new way of seeing them more directly, using the large array of tiny pendulums.

"Our proposal relies purely on the gravitational coupling, the only coupling we know for sure that exists between dark matter and ordinary luminous matter," said study co-author Daniel Carney in a statement.

The nature of the research means that if someone were to build the experiment, it would give a reasonably decisive answer to the question of whether dark matter exists as it is speculated. It will either be discovered or not – and if it is not then scientists will be able to “rule out all dark matter candidates over a wide range of possible masses”, said Carney.

If researchers were able to. wild a sensor that included a billion tiny mechanical sensors, spread out over a cubic metre, it would be sensitive enough to tell a dark matter particle from an ordinary one or other noise that might be detected in the system. Real dark matter would fly through the array, moving every detector; ordinary particles would just touch one and then stop, and noise would move randomly through the machine.

To achieve a similar effect, researchers could also try holding spheres in the air and levitating them using lasers. The lasers would then be switched off, letting the objects fall – passing dark matter particles would have enough gravity to disturb the objects slightly as they dropped down.

Similar techniques have already been used successfully to detect gravitational waves. In that case, scientists suspend large mirrors that work like pendulums, moving less than the length of an atom when a gravitational wave passes by.