HISTORY AND DEVELOPMENT

Astronomy and Physics have made many discoveries which proves that the universe had a beginning. Therefore, the big bang theory basically explains what happened at the beginning of the universe.

The theory suggests that the universe began by expanding from a small volume with higher density and temperature.

HISTORY

The Big Bang theory developed from observations of the structure of the universe and from theoretical considerations.

In 1912 Vesto Slipher measured the first Doppler shift of a "spiral nebula" (spiral nebula is the obsolete term for spiral galaxies), and soon discovered that almost all such nebulae were receding from Earth. He did not grasp the cosmological implications of this fact, and indeed at the time it was highly controversial whether or not these nebulae were "island universes" outside our Milky Way

STRUCTURE FORMATION Over a long period of time, the slightly denser regions of the

nearly uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today. The details of this process depend on the amount and type of matter in the universe.

The four possible types of matter are:1. cold dark matter2. warm dark matter3. hot dark matter4. baryonic matter

BIG BANG THEORY - EVIDENCE FOR THE THEORYWHAT ARE THE MAJOR EVIDENCES WHICH SUPPORT THE BIG BANG THEORY?

First of all, we are reasonably certain that the universe had a beginning. Second, galaxies appear to be moving away from us at speeds proportional to

their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.

Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.

Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.

Scientist who contributed to the research of expanding universe include:•Albert Einstein•Alexander Friedmann•Edwin Hubble

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