Cosmology and the Big Bang

Doppler Effect: The effect produced when a source of waves (e. g. sound or electromagnetic) is moving with respect to an observer. The observed frequency of the source is decreased if it is moving away from the observer and is increased if it is moving toward the observer.

Redshift: The observed "reddening" of light from objects in the universe which are moving away from the earth due to the Doppler effect.

Edwin Hubble: Astronomer who discovered that the universe is expanding by correlating the redshift of galaxies with their distance. The "Hubble Constant" is a measure of this correlation.

Cepheid Variable: A type of star which has a regular periodic change in brightness. The known relationship between its period and its intrinsic brightness can be used to calculate its distance from the observed brightness. They serve as a type of astronomical mileage post.

By measuring backwards from the present scientists have calculated that the universe began some 10 to 20 billion years ago. See page 146 in the text for a Chronology.

Penzias and Wilson. Scientists who discovered the background micro-wave radiation which is a remnant of the radiation given off from the big bang once the universe became transparent to photons.

Forces of nature.

• Gravitational. Mediated by the hypothetical "graviton", which has not yet been discovered. Holds the planets in orbit and us on the earth.
• Electromagnetic. Mediated by the photon. Holds molecules together, electricity.
• Weak nuclear. Involved in certain radioactive decays. Mediated by the W and Z particles.
• Strong nuclear. Mediated by gluons. Holds atomic nuclei together.

Stellar evolution.

The first stars burned (fused) only hydrogen to get helium in the early part of their life.
Eventually the helium is burned to produce carbon.
As the star ages the carbon is burned into oxygen.
Eventually silicon and other heavier elements are made and burned until iron is made; no further energy can be obtained from iron.


Since the sun (and our earth) is rich in some of these heavier elements, the sun was made from the remnants of old stars which formed these elements and died in a nova or supernova event.
So the sun is at least a second generation star.

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The fact that the Universe had a beginning seem to many to have philosophical and religious implications. Why and from whence are questions for the philosopher and theologian. I feel that it is a question worth contemplating.

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