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 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 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
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