8.2 Red-shift

Question 1

What is Red-shift?

Answer 1

An observed increase in the wavelength of light from distant galaxies.

Question 2

What two things can be said about the motion and wavelength, of light emitted from a galaxy, the further away it is?

Answer 2

• The further away a galaxy is, the faster it is moving
• The further away a galaxy is, the greater effect of red-shift on its observed light

Question 3

What does Red-shift provide evidence for?

Answer 3

• Provides evidence that the universe is expanding
• supports The Big Bang Theory

Question 4

What does The Big Bang Theory suggest?

Answer 4

The entire universe started from a small, hot and dense region in space

Question 5

Compare the observed Red-shift of two galaxies, one further away than the other

Answer 5

• The galaxy that is further away is travelling faster
• The observed Red-shift is greater the further away it is

Question 6

What did scientists observe to provide evidence that the universe is expanding at an ever faster rate?

Answer 6

They observed supernovae, which suggested that galaxies are moving away at an ever faster rate

Question 7

Prior to observations of supernovae, what was believed about the rate of expansion of the universe and why?

Answer 7

• the rate of expansion was expected to occur at an ever slower rate
• it was thought that gravitational forces would cause this slowing down

Question 8

What two ideas could explain the universes ever increasing rate of expansion?

Answer 8

• the existence of energy and mass that we can’t detect, known as dark matter and dark energy
• these ideas are still being developed by scientists and are not yet fully understood