Fritz Zwicky discovered a discrepancy between visible matter in clusters of galaxies and their motions, suggesting the presence of invisible matter, or "dark matter," interacting gravitationally with the visible matter. This led to the discovery of dark matter, which now accounts for about 27% of the Universe. Modern calculations suggest dark matter makes up about 68% of the Universe, leaving only 5% visible to us. The expansion of the Universe is accelerating, a surprising discovery due to the gravitational attraction between galaxies and clusters. Dark energy, the unseen repellant force, makes up about 68% of the Universe.

Fritz Zwicky discovered a discrepancy between visible matter in clusters of galaxies and their motions, suggesting the presence of invisible matter, or "dark matter," interacting gravitationally with the visible matter. This led to the discovery of dark matter, which now accounts for about 27% of the Universe. Modern calculations suggest dark matter makes up about 68% of the Universe, leaving only 5% visible to us. The expansion of the Universe is accelerating, a surprising discovery due to the gravitational attraction between galaxies and clusters. Dark energy, the unseen repellant force, makes up about 68% of the Universe.