The Universe

  1. Irregular Galaxy - overall globular shape
  2. Elliptical Galaxy - egg-shaped
  3. Spiral Galaxy - spiral shape; most common form of galaxy; examples are our Milky Way Galaxy and the Andromeda Galaxy

Order of the Universe Diagram

Theories on the Origin of the Universe

  1. Big Bang Theory - This is the more widely accepted theory. It explains that the universe was formed from the gigantic explosion of a central large and dense mass. In the first few minutes after the big bang, many elements such as hydrogen and helium were formed. Other heavier elements were formed later in the nuclear fusion processes of the stars. The universe is expanding, as is shown by the Red Shift of many stars (Red Shift is the spectrum showing longer wavelengths that form when stars are receding away from us).
  2. Steady-State Theory - This theory states that matter is continually being created at the outer parts of the universe, and is condensing into galaxies. It is not generally accepted now.