Summary
Book made by stephen hawking to explain cosmic physics
Key Concepts
Chapter 1 - Our Picture Of The Universe
Gravity
- Newton realized that according to his theory of gravity, the starts should attract eachother
- So they cannot remain motionless
- But, would they not all coalesce at some point?
- This would happen if there were a finite number of stars over a finite region of space
- This would not happen if there were infinite stars over infinite region of space. Because there would be no central point for them to fall to
- If all stars fall in on eachother, then it is solved
The Problem With Infinity
- In an infinite universe, every point can be regarded as the center, because every point has an infinite number of stars on each side of it
- It is impossible to have an infinite static model of the universe in which gravity is always attractive
Expanding & Contracting VS Constant Existance
Before 2000s:
- Universe is finite
- Existed forever in an unchanging state
- created at a finite time in the past After 2000s:
- The universe is growing and shrinking
- Stars are dying, civilizations are being created
The Problem With A Static Universe
The beginning of a universe cannot exist. Because, the universe can end, and there would mean that if it was not infinite, then it would have a beginning. If it ends, it begins again. Its not a physics concept, its a metaphysical understanding ^ hogwash