6.4 and 6.5 The Expanding Universe/The Big Bang

Question 1

What changes does the observer detect when the source of the waves moves away from them?

Answer 1

When the source moves away from the observer, the observed wavelength increases (bigger wavelength) and the frequency decreases (pitch decreases if sound waves)

Question 2

What changes does the observer detect when the source of the waves moves towards them?

Answer 2

When the source moves towards the observer, the observed wavelength decreases (smaller wavelength) and the frequency increases (pitch increases if sound waves)

Question 3

What type of waves can the Doppler effect be demonstrated with?

Answer 3

Sound waves

Question 4

What are galaxies?

Answer 4

Large collections of stars

Question 5

In which direction has the light observed from distant galaxies shifted? What does this mean? What is this known as?

Answer 5

Towards the red end of the spectrum (infrared etc)

This means it’s wavelength is increasing from a shorter visible light wavelength to a longer infrared radiation wavelength. This demonstrates that the galaxy is moving away from us because the Doppler effect states that when the source moves away from the observer, the observed wavelength (in this case, the colour) increases

This is known as red shift

Question 6

What would a blue shift indicate to us?

Answer 6

That a galaxy is moving closer to us

Question 7

How are we able to observe the effects of red shift?

Answer 7

By observing dark lines in the spectra from galaxies compared to the dark lines from a control source of white light

Question 8

What are the dark lines when checking for red shift due to?

Answer 8

Absorption of light in the source

Question 9

Which galaxies are moving the fastest away from us?

Answer 9

The ones furthest away are moving the fastest, in all directions

Question 10

What is the relationship between the distance of the Galaxy from us and the size of the red shift? What does this suggest?

Answer 10

The further away the galaxy, the bigger the red shift

This suggests that distant galaxies are moving away from us and the most distant galaxies are moving the fastest

Question 11

How do we know the whole universe is expanding?

Answer 11

All the distant galaxies are moving away from each other

Question 12

How does red shift show that the universe is expanding?

Answer 12

We can use the Doppler effect to show that when the galaxies shift further to the red side of the spectrum then they are moving away from us

Question 13

What is the Doppler effect?

Answer 13

The change is the observed wavelength and frequency of waves due to the motion of the source of the waves

Question 14

What does red shift give us evidence of?

Answer 14

The universe is expanding outwards in all directions

Question 15

What is the Big Bang theory?

Answer 15

The theory that the universe started with a massive explosion at a very small initial point

Question 16

Why can we assume the Big Bang theory is correct?

Answer 16

The universe is currently expanding outwards so it must have started at an initial point

Question 17

What is the evidence for the Big Bang theory?

Answer 17

The universe is currently moving away from each other, so they must have exploded at some point, releasing high energy gamma rays, that we now see as micro wave low energy radiation due to the Doppler effect

Question 18

What is the name given to the radiation produced by the Big Bang?

Answer 18

Cosmic microwave background radiation

Question 19

What is cosmic microwave background radiation?

Answer 19

The radiation produced by the Big Bang

Question 20

What is the only theory that can explain the existence of CMBR?

Answer 20

The big bang theory

Question 21

What has happened to the CMBR since the Big Bang?

Answer 21

It has been travelling through space since the Big Bang, starting off as gamma radiation, stretching it’s wavelength to microwave radiation

Question 22

How can we map out CMBR?

Answer 22

Using microwave detectors on the ground and satellites