Since 2017 I have been visiting Maastricht University on a regular basis as part of Studium Generalé. Studium Generalé provides excellent lectures as well as series of lectures that are always given by top professors or professionals.
Last Thursday, March 13, the missing universe was on the agenda by Prof. Dr. Auke-Pieter Colijn. He is a physicist who works as a professor of experimental astrophysics at the univ of Amsterdam and Utrecht. Around 6:30 pm I left for Maastricht and took Helios colleagues Walter and Fernando with me. For Walter it is already the most normal thing in the world, but for Fernando it was his first visit to Studium Generale. This time the lecture took place in the School of Business and Economics and not in the prestigious Minderbroedersberg. We were well on time and easily found a place in the grand auditorium.
The lecture started with an overview of the size of the universe and how empty it actually is. All the matter we can observe makes up only 4% of our universe. The remaining 96% consists of something we don't know and therefore call dark energy and dark matter.
In Gran Sasso, Italy, at 1500m underground, is the Laboratori Nazionali del Gran Sasso (LNGS). Here deep underground they are looking for WIMPs or weakly interacting massive particles. These particles are possible candidates for dark matter. For the sake of completeness, all other candidates were also discussed.
To find the WIMP particles, a tank was built with 8000 kg of liquid Xenon, the so-called XenonNT project see https://xenonexperiment.org/ When a WIMP particle interacts with xenon, electrons and a photon will be released immediately. The electrons are led by an electric field to the top of the tank where they come into contact with gaseous Xenon and release another photon. The sequential release of two photons over a certain time interval is the characteristic of a WIMP. Despite the fact that the experiment has been working for several years, no dark matter was found.
