OUTCOME
By the end of the lesson you will recognise that the universe is expanding and be able to apply Doppler shift as proof of the universe's expansion
Doppler shift if a phenomena that occurs when a wave source if moving
Hubble first proposed the universe was expanding when he observed that all galaxies were red shifted relative to Earth
LEARNING TASKS
Explain
1. How big approximately is a light year?
2. Why can't we see the whole universe?
3. Why do we know is the size of the universe so much bigger than the can see?
4. How do we know the expansion rate of the universe?
Why does a light source moving toward the Earth appear blue shifted? Does this mean it will appear blue in the sky?
Challenge
Why don't galaxies expand as well as the distance between galaxy clusters?
Evaluate
Review 5.2