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

Objectives:

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

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

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

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!

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!

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

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!

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

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?

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

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

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

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

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!

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

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

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?

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?

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] .

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

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