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Natural Science - Year II

Unit 64: The Origins of the Universe

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Unit 64: Cosmology

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Lecture:

Cosmology

The term "cosmology" is actually relatively recent, but the concept of an all-embracing explanation of everything in the universe from its beginning to its end has been a goal of spiritual leaders, philosophers, and scientists.

The Judeo-Christian beginnings

Part of the fascination with such an explanation is the hope that it would explain our own position in the world. We humans define and locate ourselves partly by our physical surroundings, and we estimate our importance and worth to some extent by our "place in the universe".

In Psalm 8, David writes

The Hebrew Bible assumed that something must pre-exist creation, and that the existence of the universe was the result of the action of a Being outside the limits of that universe, constrained neither by space or time as the physical universe (and the humans in it) was.

Aristotle

In contrast, Aristotle assumed that the universe was itself eternal, but that it required a Mover to initiate all motion within it. And while the universe might be uncreated and last forever, it could not extend forever, or a point on the rotating perimeter would travel with infinite speed — a situation Aristotle considered impossible.

The four kinds of terrestrial matter were limited to movement toward and away from the center of the earth; celestial matter was constrained to move in perfect circles about this center, trapped in spheres that filled all space. A vacuum was impossible.

Medieval Cosmology

Medieval cosmology tried to blend the concepts of Aristotle with the predictive capability of Ptolemy.

Take a look at the pretty diagrams that illustrate the medieval world view at the Luminarium: Encyclopedia Project. Note the circles of earth, water, air and fire below the moon, and the circles for the visible planets above the moon. What lies beyond Saturn? Why were these extra spheres necessary?

Newtonian Cosmology

With Newton, the scientific revolution that Copernicus had started found a basis in cause-and-effect forces, and a mathematical rigor that was completely different from what had come before. The theory of gravity clearly allowed for the radical proposal of Thomas Digges for a random distribution of stars and matter continuing out to infinity.

Modern Cosmology

Our modern view of cosmology is influenced by Einstein's relativity and Hubbles measures of the size of the universe, and by the curiously irritating presence of "noise" in the Dicke radiometer that Arno Penzias and Robert Woodrow Wilson at the Bell Telephone Laboratories built to use for radio astronomy observations. No matter what direction they pointed their antennae, they got a 3.5K excess temperature. When they called Robert Dicke at Princeton to share the news, Dicke acknowledged their discovery rather ironically -- he'd predicted the existence of the 3.5K background noise based on theories George Gamow and Ralph Alpher had proposed in 1948. The radiation was interpreted as the fading "glow" of an enormous initial explosion that began the universe.

Read some (all if you can) of the PBS history site on Cosmology. This is a long site, and introduces many different views on the issues facing us as a result of our current cosmological theories, or attempts to explain everything in a coherent framework.

Study/Discussion Questions:

  • What are some of the issues and controversies raised by the Big Bang theory, genetics, and social concerns for how science influences ethical decisions?

Further Study/On Your Own