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 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 the big bang theory suggest?

Answer 3

the entire universe started from a very small, hot and dense region in space.

Question 3

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

Answer 3

they observed supernovae, which suggested that galaxies are moving away at an even faster rate.

Question 3

why does red-shift provide evidence for?

Answer 3

• provides evidence that the universe is expanding
• supports the big band theory

Question 4

compare the observed red-shift of two galaxies, one further away than the other.

Answer 4

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

Question 5

prior to observations of supernovae, what was belived about the rate of expansion of the universe and why?

Answer 5

• 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 6

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

Answer 6

• 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