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Team of Physicists in CRANN in major breakthrough on properties of empty space

14 Mar 2016

Theoretical physicists have long believed that empty space is not a formless void. It is seething with ‘zero-point’ energy, the quantum reside of all electromagnetic waves. Nobody has ever managed to find a way to harvest this limitless store of energy, and the direct evidence for its existence relies on a few very delicate landmark experiments.

Now, a team of scientists working in Trinity College Dublin’s Centre for Research on Advanced Nanostructures and Nanodevices (CRANN) have discovered a new and unexpected manifestation of this elusive energy. In a study of cerium dioxide nanoparticles – mostly used in catalytic converters that control toxic exhaust emissions from automobiles – Professor Michael Coey, his former PhD student Karl Ackland and Dr Munuswamy Venkatesan came across a strange magnetic effect.

In a paper published on-line in Nature Physics*, the team that included Professor Siddhartha Sen, a quantum field theorist, originally from Trinity’s Mathematics Department, explained: “Electrons in the clumps of tiny particles were responding in unison to the vacuum electromagnetic field. Stranger still, the magnetism only appeared when the particles were clumped together. Separating them into smaller clumps by diluting with nonmagnetic nanoparticles destroyed the magnetism. We were astonished by our findings.”

Professor Coey, a Principal Investigator in CRANN and the School of Physics, Trinity College Dublin, said: “As with any fundamental discovery in science, it is difficult to predict where this could lead. Others will want to test the results. The theory shows that effects can only be expected when there is a huge surface to volume ratio, as in the thin layers of interfacial water attached to biomolecules. The zero point energy may never power our cars, but it might be shaping our lives.”

Sen and Coey had recently predicted that such collective behaviour might be possible in systems with an enormous surface area – a milligram speck of the cerium dioxide nanoparticles has as much surface area as an entire sheet of newspaper. Furthermore they predicted that when the particle clumps were broken up into smaller ones, smaller than the wavelength of the light associated with them, the effect would vanish. This is exactly what was observed. In addition, quite unlike the behaviour of normal magnets like iron, the effect does not vary at all with temperature.

To date, the best direct evidence of this zero-point electromagnetic radiation in empty space has been a tiny shift of a few parts per billion in an energy level of hydrogen, discovered 70 years ago by Willis Lamb in the USA, and a minute force between metal plates when they are only a few nanometers apart in vacuum predicted around the same time by Dutchman Hendrik Casimir; and measured much later.

*Collective magnetic response of CeO2 nanoparticles, Michael Coey, Karl Ackland, Munuswamy Venkatesan and Siddhartha Sen, Nature Physics (2016) doi.10.1038/nphys3676