1. The Athropic Principle
Science has discovered many factors that are necessary conditions to sustain life. The chance that all these factors happen “by itself” is extremely unlikely. In fact, they are so unlikely that science coined a new term to describe them: athropic principle.

2. Where are we exactly ?
Earth
Galaxy
Solar System
Universe

3. Is our earth and solar system special ?
There are millions of galaxies
Within one galaxy, there are millions of stars
Surely, there must be billions of planets just like our earth ?
And there must be millions of planets that have life on them !
That was science believed
Recently, science discovered many factors that are necessary to make life possible
Our earth and solar system is in fact, special !

4. Conditions for Life Life is extremely fragile Life need water
Life need sun light (photosynthesis)
Life cannot tolerate high energy radiation (X-rays, Gamma-radiation)
Life cannot tolerate extreme heat (ever seen a fish swim in boiling water ?)
Life cannot tolerate extreme cold (ever seen a fish survive in ice ?)
And so on…

5. Life: Shape of the Galaxy
Galaxies come in 3 shapes:
Spiral galaxy
Elliptical galaxy
Irregular galaxy