Why can’t we detect Dark Matter, which makes up 85% of the Universe’s mass? Scientists at the University of Southampton in England, and the Max-Planck-Institut für Physik in Germany, have proposed a new fundamental particle which may help explain.
We believe Dark Matter exists because of its gravitational effects on galaxies and stars, its bending of light (gravitational lensing), and through its imprint on the afterglow of the Bing Bang (Cosmic Microwave Background).
Despite abundant indirect evidence and significant experimental effort, not one scientists has so far managed to detect Dark Matter directly.
Scientists say Dark Matter is non-luminous material which is believed to occupy 85% of space. It could take either of two forms: 1. Cold Dark Matter (weakly interacting particles). 2. Hot Dark Matter (high-energy randomly moving particles).
Particle physics gives us some indication to what Dark Matter might be. Most physicists believe that Dark Matter particles have a huge mass for fundamental particles, similar to heavy atoms.
In a new study published in Scientific Reports (citation below), the authors wrote that lighter Dark Matter particles are considered less likely for astrophysical reasons, although exceptions are known. This research outlines a previously unknown window where they might exist and, with very general particle physics arguments, derives some surprising results.
The proposed particle has a mass of 100eV/c^2, which is about 0.02% (one five-hundredth) that of an electron. While not interacting with light, which Dark Matter does, it interacts significantly strongly with normal matter.
Experiments will need to be done in outer space
In stark contrast to other candidates, this proposed particle may not even penetrate Earth’s atmosphere, thus making it much less likely that it could be detected from Earth.
Scientists are planning to incorporate searches into a space experiment planned by the MAQRO (Macroscopic quantum resonators) consortium, with whom they are already involved.
The authors explain that a nanoparticle (a particle between 1 and 100 nanometers in size), suspended in space and exposed directly to the Dark Matter flow, will be pushed downstream while sensitive monitoring of its position will reveal data about the nature of this Dark Matter – if of course, it exists.
Co-author Dr. James Bateman, from Physics and Astronomy at the University of Southampton, said:
“This work brings together some very different areas of physics: theoretical particle physics, observational x-ray astronomy, and experimental quantum optics. Our candidate particle sounds crazy, but currently there seem to be no experiments or observations which could rule it out.”
“Dark Matter is one of the most important unsolved problems in modern physics, and we hope that our suggestion will inspire others to develop detailed particle theory and even experimental tests.”
Co-author, Dr. Alexander Merle, from the Max Planck Institute in Munich, Germany, added:
“At the moment, experiments on Dark Matter do not point into a clear direction and, given that also the Large Hadron Collider at CERN has not found any signs of new physics yet, it may be time that we shift our paradigm towards alternative candidates for Dark Matter.”
“More and more particle physicists seem to think this way, and our proposal seems to be a serious competitor on the market.”
Dr. Bateman said:
“Also from this point of view, the paper comprises a milestone on the history of our department: for the first time there has been a publication involving authors from all three groups in Physics and Astronomy, which shows how valuable it can be to cross boundaries and to look beyond one’s own field.”
Citation: “On the Existence of Low-Mass Dark Matter and its Direct Detection,” James Bateman, Ian McHardy, Alexander Merle, Tim R. Morris & Hendrik Ulbricht. Scientific Reports. January 27, 2015. doi:10.1038/srep08058.