Born around 1900, just 10 years or so younger than Albert Einstein was a truly remarkable astronomer. The father of Dark Energy, Fritz Zwicky was the son of a Swiss Industrialist who lived in Bulgaria.
Fermi-Lab scientists have spent the last 15 years or so searching for particles of Dark Matter. Using a disk of Gallium metal cooled to nearing zero Kelvin, scientists have not detected the particles. They sought out a particle with mass, traveling at less than the speed of light and unimpeded by other matter.
Fritz Zwicky first referred to Missing Matter or Missing Mass when he observed galaxies at Mount Wilson, and calculated their mass and the speed of rotation. He found that stars near the edge of the galaxy sped around its center too quickly. Based on the gravitational pull of the galaxy, they should have been flung into space.