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Wednesday, August 28, 2013

'Fastest man-made spinning object' made by scientists

The red squiggles indicate the polarisation of the light beam, which changes as it goes through the purple sphere

A team of researchers claims to have created the world's fastest spinning man-made object.

They were able to levitate and spin a microscopic sphere at speeds of up to 600 million revolutions per minute.

This spin speed is half a million times faster than a domestic washing machine and more than a thousand times faster than a dental drill.

The work by the University of St Andrews scientists is published in Nature Communications.

Although there is much international research exploring what happens at the boundary between classical physics and quantum physics, most of this experimental work uses atoms or molecules.

Microscopic sphere

The St Andrews team aimed to understand what happened for larger objects containing a million million atoms or more.

To do this they manufactured a microscopic sphere of calcium carbonate only four millionths of a metre in diameter.

The team then used the miniscule forces of laser light to hold the sphere with the radiation pressure of light - rather like levitating a beach ball with a jet of water.

They exploited the property of polarisation of the laser light that changed as the light passed through the levitating sphere, exerting a small twist or torque.

Placing the sphere in vacuum largely removed the drag due to any gas environment, allowing the team to achieve the very high rotation rates.

In addition to the rotation, the team observed a "compression" of the excursions or "wobble" of the particle in all three dimensions, which can be understood as a "cooling" of the motion.

Essentially the particle behaved like the world's smallest gyroscope, stabilising its motion around the axis of rotation.

Dr Yoshihiko Arita of the university's School of Physics and Astronomy said: "This is an exciting, thought-provoking experiment that pushes the boundary of our understanding of rotating bodies.

Quantum friction
"I am intrigued with the prospect of extending this to multiple trapped particles and rotating systems.

"We may even be able to shed light on the area of quantum friction - that is does quantum mechanics put the brakes on the motion or spinning particle even though we are in a near perfect vacuum with no other apparent sources of friction?"

Dr Michael Mazilu, a newly appointed lecturer in the school, added: "This system poses fascinating questions with regard to thermodynamics and is a challenging system to model theoretically.

"The rotation rate is so fast that the angular acceleration at the sphere surface is one billion times that of gravity on the Earth surface. It's amazing that the centrifugal forces do not cause the sphere to disintegrate."

The third member of the team, Professor Kishan Dholakia, said he believed they had "performed a real breakthrough piece of work" that would resonate with the international community.

"In addition to the exciting fundamental physics aspects, this experiment will allow us to probe the nature of friction in very small systems, which has relevance to the next generation of microscopic devices. And it's always good to hold a 'world record' - even if for only a while," he added


The aim of the experiment was to see what would happen if a microscopic sphere was spun as fast as was technically possible.

The team balanced it on a laser beam in a complete vacuum and then spun it using the light itself.

They saw it spin faster and faster until it reached 600 million rpm - and then it seemed to vanish!

The researchers don't know what happened to the sphere - but one possibility is that the object may have reached some theoretical speed limit - after which it changed in some way.

The next step for the researchers is to discover what became of the object and whether they really have discovered a completely new physical phenomenon.


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