PhysicsChapter 9: Cosmology
The Big Bang Theory
The Big Bang model
Definition
The Big Bang model describes the universe as having evolved from an extremely hot, dense early state and subsequently expanding and cooling.
Important Clarification
According to the standard cosmological picture: 1. The early universe was extremely hot and dense. 2. The universe expanded. 3. Expansion caused cooling. 4. Conditions changed enough for particles and nuclei to form. 5. Later, atoms formed. 6. Gravity eventually helped matter form stars and galaxies. 7. Cosmic expansion continues today. The Big Bang model explains the **evolution of the observable universe from an early hot, dense state**. The model should not casually be described as matter exploding from a central location into pre-existing empty space.
Formula / Key Relation
A key observational relation is: **v=H₀d Expansion is represented by: H=ȧ/a**
Exam preparation
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Review the key facts, formulas and checks before you move on.The Big Bang Theory
Sticky Notes · Quick Revision
BIG BANG
- Hot early universe
- Dense
- Expansion
- Cooling
- Atoms
- Stars
- Galaxies
60-second revision
- The Big Bang model explains an expanding universe that evolved from a hot, dense early state.
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