1. To look at the theories of how the Universe began
Big Bang
To look at the theories of how the Universe began

2. Definitions Universe – The complete system of all that exists
Galaxy – A system of stars and stellar dust
Star – a Sun seen as a point of light
Solar system – a star and everything that orbits around that star
Planet – A large rocky or gaseous object that orbits around a star

5. The big bang theory proposes that the universe was once extremely compact, dense, and hot. Some original event, a cosmic explosion called the big bang, occurred about 13.7 billion years ago, and the universe has since been expanding and cooling.