The Universe Is Filled With Invisible Stuff

The universe is overwhelmingly made up of things that cannot be seen. In fact, the stars, planets and galaxies that can be detected make up only 4 percent of the universe, according to astronomers. The other 96 percent is made up of substances that cannot be seen or easily comprehended. These elusive substances, called dark energy and dark matter, have not been detected, but astronomers base their existence on the gravitational influence that both exert on normal matter, the parts of the universe that can be seen.