1. Combined Science (1-9): Astronomy Orbits and Theories of the Universe

2. Objectives:

3. Orbits and Theories of the Universe
Draw a line under last lesson’s work and write today’s title in your book...
Orbits and Theories of the Universe
22/11/2018
c/w

4. FLASHBACK
FLASHBACK: Explain the difference between a scalar and a vector quantity and give two examples of each [4 marks]

5. FLASHBACK- AFL
FLASHBACK: Explain the difference between a scalar and a vector quantity and give two examples of each [4 marks]
A scalar quantity has only a magnitude (size)
A vector quantity has both a magnitude and a direction
Scalar examples: speed, time, energy, work, distance, mass
Vector examples: velocity, displacement, acceleration, force

6. Starter Activity
A planet will orbit a star at a constant speed. Explain why scientists are still correct in saying that the planets are ‘accelerating’?
It’s changing direction. Therefore despite speed staying constant, the velocity (which has a direction) is changing. As such it’s accelerating!

7. Orbits
To ensure a stable orbit, what must an orbiting body (e.g. a planet) do if it were to orbit at a faster speed?
If an orbiting body orbits at a faster speed, it needs to increase its distance from the source of gravity!

8. Discussion!
What is the shape of the universe, and what is happening to it? Write your own hypothesis and include any relevant evidence you may have

9. Explore: Theory Battle Steady State Theory Big Bang Theory
Using the diagrams shown, write a suggestion of what each theory is! You’ve probably heard of one of them already!

10. This then caused the universe to expand ever since
The Big Bang Theory
“Our whole universe was in a hot, dense state / Then nearly fourteen billion years ago expansion started, wait”
The Big Bang (BB) theory states that there was a single point (singularity) as an origin that then exploded and produced the universe.
This then caused the universe to expand ever since

11. What is the only factor that both theories share?
The Steady State Theory
The Steady State (SS) theory, as the name suggests is the theory that the universe has always existed and that it is expanding
The theory goes that this expansion is due to new mass being added. Where this mass comes from is as yet unknown…
That the universe is expanding
What is the only factor that both theories share?

12. In order for us to accept and prefer a certain theory, what is first needed?
Evidence!

13. Evidence 1: Red Shift
Write down what you observe/hear when an ambulance drives past with its sirens on
As you watch this video, make notes on what physics is occurring during this process

14. What happens to the waves when the object is moving?
Sound travels as waves.
What happens to the waves when the object is moving?
Stationary wave source
Moving wave source

15. If object is moving away, then waves seem to be spread out
If object is moving towards you, then waves seem bunched together
= low frequency
= high frequency

16. Context
It’s like the water waves around a speeding boat! All those in front of the boat get compressed, those behind the boat get spread out!

17. The same thing happens with light (the EM spectrum)…
Moving away = lower frequency
Moving towards = higher frequency
Light shifts to red
Light shifts to blue

18. All the light we detect from distant galaxies is appearing RED SHIFTED – this means the waves are spread out suggesting that the galaxies are moving away from us and at speed!..
What does this tell us about the universe if all the galaxies are moving away from us? Therefore which theory/theories does it support?
Close by star
Nearby galaxy
That the universe is expanding
Far away galaxy

19. So which theory or theories does this support?
Evidence 2: CMBR
If an explosion was to occur and release a lot of energy…what part of the EM spectrum would this energy be found as?
What would gradually happen as this wave travelled a long distance…what part of the spectrum might it be now?
The gamma waves lose energy and become microwaves by the time we have observed them. These microwaves are known as cosmic microwave background radiation (CMBR) and is evidence of an explosion
So which theory or theories does this support?

20. So which theory is best supported and therefore preferred?
So…who wins?
Big Bang Theory
Steady State Theory
Red Shift
Red Shift
CMBR
So which theory is best supported and therefore preferred?

21. 6 mark question!
There are two main theories of the universe’s creation. Explain how our detection of the EM spectrum has provided evidence for these theories and state why one theory is preferred [6 marks] .

22. 6 mark question!
There are two main theories of the universe’s creation. Explain how our detection of the EM spectrum has provided evidence for these theories and state why one theory is preferred [6 marks] .
Two theories are the steady state and big bang theory
Steady state has no origin but big bang has exploding origin
Both indicate that the universe is expanding
Red shift is the apparent increase of wavelength (spreading) from the EM waves from a galaxy due to them moving away
Red shift supports both theories
We have detected microwaves from far in space, these must have originated from an explosion (CMBR)
These only support big bang theory
More evidence for BBT than SST so the big bang theory is preferred

23. Objectives: