The larger the mirror of an astronomical telescope, the greater will be the telescope's ability to collect light. The primary mirror of the Subaru telescope, built by Japan's National Astronomical Observatory, has a diameter of 8.2 m, making Subaru the world's largest optical telescope, and one that boasts very high resolution, with a diffraction limit of only 0.23 arc seconds. This is good enough resolution to be able to make out a small coin placed on the tip of Mt. Fuji from as far away as Tokyo. Moreover, the Subaru telescope is about 600 million times more sensitive to light than the human eye. Even the largest telescopes until Subaru were unable to observe stars more than about one billion light years away, but Subaru can pick up light from galaxies lying 15 billion light years away. Light from 15 billion light years away and beyond is, in fact, thought to be light produced by the "big bang" that supposedly gave birth to the universe.