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.
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
CRANN is one of Trinity College Dublin’s largest institutes and Ireland’s flagship nanoscience institute. It has significant infrastructure, and brings together over 300 researchers from across Trinity’s Schools of Physics, Chemistry, Engineering, Medicine and Pharmacology. CRANN is focused on delivering world leading research and innovation – through extensive proactive collaborations with industry, the commercialisation of intellectual property and the education of next generation researchers. The Institute is host to AMBER (advanced-materials/” title=”View all articles about Advanced Materials here”>Advanced Materials and BioEngineering Research), the Science Foundation Ireland funded centre, which provides a partnership between leading researchers in materials science and industry to develop new materials and devices for a range of sectors, particularly the ICT, medical devices and industrial technology sectors. www.crann.tcd.ie