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This is a free online course offered by the Saylor Foundation.

'You will be introduced to our current understanding of the universe and how we have come to this understanding.  We will start with the ancient Greeks and their belief that the universe was an orderly place capable of being understood.  We will continue through history, as we acquired more information on the nature of the universe and our models of the universe changed to reflect this.  This will take us through several different worldviews.

As noted above, we will begin with the Greek worldview, which was characterized by the belief that the earth was the immovable center of the universe; this was known as the “geocentric” model.  Although this worldview is wrong in many of its details, it was a very important first step.  It explained the universe well enough that it lasted almost two thousand years.  By 1600, this belief was beginning to be challenged by such people as Copernicus, Kepler, and Galileo; finally, it was completely done away with by the physics of Newton.  By 1700, the heliocentric model, with the sun at the center and the earth and other planets in orbit around it, had replaced the geocentric one.  The model of the universe based on the physics of Newton lasted into the twentieth century.  It has since been replaced by our contemporary model.

The most essential feature of our contemporary model is that the universe is evolving.  It had a beginning in time, some 13.7 billion years ago, in an unimaginably hot and dense state, and evolved, as a result of the expansion of space, to develop structures: first hydrogen and helium atoms, then stars and galaxies.  The stars evolved to produce the heavier elements, casting them out into space through their explosive deaths.  From leftover hydrogen and helium, together with the new heavier elements, later generations of stars formed, some, such as our own sun, with planets around them.  On our earth, geological processes transformed the environment to allow for the development of life and eventually us.'

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