8.2 Space Physics (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 emitted light 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 the observed increase in wavelength

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 very 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 even faster rate?

Answer 6

they observed supernovae, which suggested that galaxies are moving away at an even 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 even slower rate
• it was thought that gravitational forces would cause this slowing down

Question 8

What is dark energy and dark matter?

Answer 8

energy and matter that we can’t detect

Question 9

What two ideas could explain the universe’s ever increasing rate of expansion?

Answer 9

• the existence of dark matter and dark energy
• these ideas are still being developed by scientists and are not yet fully understood