Since the 1960s, scientists have theorized that the Universe is filled with a mysterious, invisible mass. Known as “dark matter“, this mass is estimated to make up roughly 85% of the matter in the Universe and a quarter of its energy density. While this mass has been indirectly observed and studied, all attempts at determining its true nature have so far failed.
Shortly after the big bang, the universe was an energetic mixture of particles with strong mutual interaction. The first particles that managed to free themselves from this dense primordial soup were the neutrinos, the lightest and weakest interacting particles from the standard model of elementary particles. These neutrinos are still all around us today, but are very difficult to observe immediately because their interaction is so weak. An international team of cosmologists, including Daniel Baumann and Benjamin Wallisch from the University of Amsterdam, has now succeeded in measuring the influence that this 'cosmic neutrino background' has had on the way galaxy clusters formed during the evolution of the universe. The research was published in Nature Physics.
In the world of quantum, infinitesimally small particles, weird and often logic-defying behaviors abound. Perhaps the strangest of these is the idea of superposition, in which objects can exist simultaneously in two or more seemingly counterintuitive states. For example, according to the laws of quantum mechanics, electrons may spin both clockwise and counter-clockwise, or be both at rest and excited, at the same time.