MULT10011 Lecture Notes - Lecture 24: Big Bang, Cosmic Microwave Background, Baryon

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15 Jun 2018

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L.E.U – Lecture 24

Big bang and evolution of the universe

Big bang model

Our model for formation of the universe (inappropriate). There are 3 key features:

1. homogenous

2. expanding

3. very hot and dense at early times

Homogenous

• homogenous mixture – all water in a cup is the same

• homogenous in cosmology – there are no special places

• if we teleport anywhere in universe, it will look the same statistically

o on average (over an enormous volume of radius – 300 mill light years)

o homogenous in space, not time – universe evolves/changes with time

Expanding universe – implications

• there is a beginning

• either ere at the eter, or everything is moving apart

Cosmological redshift (z) in an expanding universe

• as universe expands, distances between objects become larger, light from distant

galaxies becomes redder as it

travels to observer – redder =

cooler temperatures

• high-z redshifted sources –

photons redshift as they travel

through expanding universe

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