How Large is the Universe?

Check out this 1080P update of the Cosmic Journeys episode.

The universe has long captivated us with its immense scales of distance and time. How far does it stretch? Where does it end, and what lies beyond its star fields and streams of galaxies extending as far as telescopes can see?


These questions are beginning to yield to a series of extraordinary new lines of investigation and technologies that are letting us to peer into the most distant realms of the cosmos.


But also at the behavior of matter and energy on the smallest of scales. Remarkably, our growing understanding of this kingdom of the ultra-tiny, inside the nuclei of atoms, permits us to glimpse the largest vistas of space and time. In ancient times, most observers saw the stars as a sphere surrounding the earth, often the home of deities. The Greeks were the first to see celestial events as phenomena, subject to human investigation rather than the fickle whims of the Gods.


One sky-watcher, for example, suggested that meteors are made of materials found on Earth... and might have even come from the Earth. Those early astronomers built the foundations of modern science. But they would be shocked to see the discoveries made by their counterparts today. The stars and planets that once harbored the gods are now seen as infinitesimal parts of a vast scaffolding of matter and energy extending far out into space.


Just how far began to emerge in the 1920s. Working at the huge new 100-inch Hooker Telescope on California's Mt. Wilson, astronomer Edwin Hubble, along with his assistant named Milt Humason, analyzed the light of fuzzy patches of sky... known then as nebulae.


They showed that these were actually distant galaxies far beyond our own. Hubble and Humason discovered that most of them are moving away from us. The farther out they looked, the faster they were receding. This fact, now known as Hubble's law, suggests that there must have been a time when the matter in all these galaxies was tog

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