Red-shift and the Big Bang - Teacher Slides.pptx

AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Red-shift and the Big Bang

Space physics

Lesson 4 of 4

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Warm-up

Space physics

Lesson 4 of 4

Answer each one, then check.

1

What is light?

2

What is wavelength?

3

What colour has the longest wavelength in visible light?

4

What is a galaxy?

5

What is an ambulance siren's pitch change called?

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Warm-up - Answers

Space physics

Lesson 4 of 4

1

What is light?

An electromagnetic wave

2

What is wavelength?

Distance between corresponding points on adjacent waves

3

What colour has the longest wavelength in visible light?

Red

4

What is a galaxy?

A huge group of stars

5

What is an ambulance siren's pitch change called?

The Doppler effect

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Learning Objectives

Space physics

Lesson 4 of 4

1

Explain the observed red-shift of light from distant galaxies.

2

Explain why red-shift is evidence that the universe is expanding.

3

Describe the Big Bang theory.

4

Explain why the red-shift is greater for more distant galaxies.

5

Describe dark matter and dark energy.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Space physics

Lesson 4 of 4

RED-SHIFT

The light from most distant galaxies is shifted towards the red end of the spectrum: its wavelength is increased. This is red-shift. It shows the galaxies are moving away from us, and that the universe is expanding.

The more distant the galaxy, the greater the red-shift, so the faster it is moving away.

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Red-shift

Space physics

Lesson 4 of 4

Longer wavelength means redder.

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The Big Bang Theory

Space physics

Lesson 4 of 4

Follow the steps.

1

Start

All the matter and energy in the universe was in a very small, hot, dense point.

2

Explosion

It expanded violently about 13.8 billion years ago.

3

Expansion

Space itself has been expanding ever since.

4

Evidence

Red-shift of galaxies and cosmic microwave background radiation (CMBR).

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Evidence for the Big Bang

Space physics

Lesson 4 of 4

Learn the two main pieces.

Evidence

What it shows

Red-shift

Galaxies are moving away and the universe is expanding; further galaxies move faster

CMBR

Leftover microwave radiation from the early universe, in all directions

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Red-shift and Distance

Space physics

Lesson 4 of 4

Galaxy A has a greater red-shift than galaxy B. What can you conclude?

1

Red-shift

Greater for A

2

Speed

A is moving away faster than B

3

Distance

A is further away than B

ANSWER

A is moving away faster and is further away than B.

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Dark Matter and Dark Energy

Space physics

Lesson 4 of 4

What we don't know.

Dark matter

Matter we cannot see that explains how galaxies rotate; it interacts gravitationally.

Dark energy

A form of energy thought to cause the universe's expansion to accelerate.

Open questions

Their nature is not yet understood.

Theories change

Scientists keep testing theories with new evidence.

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Key Terms

Space physics

Lesson 4 of 4

Red-shift

The increase in the observed wavelength of light from distant galaxies because they are moving away.

Big Bang theory

The theory that the universe began from a very small, hot, dense region and has been expanding ever since.

CMBR

Cosmic microwave background radiation; leftover microwaves from the early universe.

Dark matter

Matter that does not emit light but has gravitational effects.

Dark energy

An unknown energy thought to be driving the accelerating expansion of the universe.

Expanding universe

The idea that space is getting larger over time.

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Space physics

Lesson 4 of 4

YOUR TASK

Red-shift Talk

10 minutes

Explain to a partner why red-shift shows that the universe is expanding. Then explain why a galaxy twice as far away seems to move away twice as fast.

1

All galaxies are moving away.

WHAT A GOOD ANSWER SHOWS

The wavelengths are lengthened because the galaxies move away; this happens in all directions, so the universe is expanding. Further galaxies show a greater shift, so they move faster.

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Can I...?

Space physics

Lesson 4 of 4

Define red-shift.

Explain the expansion.

Describe the Big Bang.

Name the evidence.

Explain distance and red-shift.

Define CMBR.

Define dark matter.

Define dark energy.

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Summary & Exam Focus

Light from distant galaxies is shifted to longer wavelengths.

The universe is expanding.

Big Bang: small, hot, dense start about 13.8 billion years ago.

Evidence: red-shift and CMBR.

EXAM FOCUS

State what red-shift shows about the universe. (1 mark)

It is expanding.

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Exam Practice: Red-shift and the Big Bang

Space physics

Lesson 4 of 4

Answer all questions. Use the mark allocation as a guide to how much to write. · 16 minutes

Question 1 · 2 marks · State

Describe what is meant by red-shift.

Question 2 · 3 marks · Explain

Explain why red-shift is evidence that the universe is expanding.

Question 3 · 3 marks · Describe

Describe the Big Bang theory of the origin of the universe.

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Exam Practice: Red-shift and the Big Bang (cont.)

Space physics

Lesson 4 of 4

Question 4 · 3 marks · Explain

Two galaxies are observed. Galaxy P has a greater red-shift than galaxy Q. Explain what this shows about P and Q.

Question 5 · 4 marks · Explain

Explain why the discovery of cosmic microwave background radiation (CMBR) supports the Big Bang theory, and state what is still not…

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Question 1 · 2 marks · State

Space physics

Lesson 4 of 4

“

Describe what is meant by red-shift.

HOW TO ANSWER IT

Command word: State. Worth 2 marks, so plan before writing.

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Question 1 · mark scheme

Space physics

Lesson 4 of 4

2 marks available. Award a mark for each point made.

Wavelength increases

1 mark

Shift towards the red end

1 mark

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Question 2 · 3 marks · Explain

Space physics

Lesson 4 of 4

“

Explain why red-shift is evidence that the universe is expanding.

HOW TO ANSWER IT

Command word: Explain. Worth 3 marks, so plan before writing.

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Question 2 · mark scheme

Space physics

Lesson 4 of 4

3 marks available. Award a mark for each point made.

Red-shift means the galaxies are moving away

1 mark

All directions

1 mark

Further galaxies move faster

1 mark

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Question 3 · 3 marks · Describe

Space physics

Lesson 4 of 4

“

Describe the Big Bang theory of the origin of the universe.

HOW TO ANSWER IT

Command word: Describe. Worth 3 marks, so plan before writing.

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Question 3 · mark scheme

Space physics

Lesson 4 of 4

3 marks available. Award a mark for each point made.

Small, hot, dense region

1 mark

Explosive expansion

1 mark

Still expanding

1 mark

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Question 4 · 3 marks · Explain

Space physics

Lesson 4 of 4

“

Two galaxies are observed. Galaxy P has a greater red-shift than galaxy Q. Explain what this shows about P and Q.

HOW TO ANSWER IT

Command word: Explain. Worth 3 marks, so plan before writing.

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Question 4 · mark scheme

Space physics

Lesson 4 of 4

3 marks available. Award a mark for each point made.

P moving away faster

1 mark

Greater red-shift means faster recession

1 mark

P is further away

1 mark

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Question 5 · 4 marks · Explain

Space physics

Lesson 4 of 4

“

Explain why the discovery of cosmic microwave background radiation (CMBR) supports the Big Bang theory, and state what is still not understood about the universe.

HOW TO ANSWER IT

Command word: Explain. Worth 4 marks, so plan before writing.

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Question 5 · mark scheme

Space physics

Lesson 4 of 4

4 marks available. Award a mark for each point made.

CMBR is leftover radiation from the early universe

1 mark

Observed in all directions

1 mark

Dark matter not understood

1 mark

Dark energy not understood

1 mark

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