Red-shift

Question 1

What is red-shift?

Answer 1

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

Question 2

What 2 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 2 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 2 ideas could explain the universe’s 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.