Now, following painstaking analysis, project scientists have declared that they have recorded a couple of likely looking dark matter events. One such experiment, known as the Cryogenic Dark Matter Search, in Minnesota, has been gathering data for several years. The challenge is to detect such a collision. As a result, there is a small probability that a dark matter particle will bump into an atomic nucleus and send it flying. Because the solar system orbits the galaxy at more than 200km per second, it should be ploughing through an ocean of primordial dark matter. The race to detect and identify these particles started in the 1980s. As a result, the dark particles interact so feebly with ordinary matter that they mostly pass right through it. Nor do they feel the strong nuclear force that traps protons and neutrons in atomic nuclei.

The reason for the appellation 'dark' is because, unlike atomic particles, they have no electric charge, so cannot emit or scatter light. Aided by the gravitating power of the dark component, ordinary matter was pulled into clumps, which later evolved into galaxies that spawned stars, planets and, in one case at least, life.Ī consensus has emerged that dark matter mostly consists of massive particles coughed out of the big bang. After the big bang that created the universe 13.7bn years ago, matter was spread smoothly through space. And its role in shaping the cosmos is crucial. Today, cosmologists can put a precise figure on the amount of dark matter in the universe: about five times the mass of the luminous, common-or-garden variety of matter. So what keeps them intact? The simplest explanation is that some form of dark matter provides the necessary gravitationally binding.

The astronomer Fritz Zwicky noticed that within the clusters, galaxies mill around so fast that the clusters ought to fly apart. The first inkling that the universe is dominated by unseen material came from the observations of clusters of galaxies made in the 1930s.

About Time by Paul C.W. Davies