Astrophysics - Cosmology (Paper 2)

Question 1

what is the past evolution of the universe?

Answer 1

scientists believe that about 14 billion years ago all matter in the universe was in one extremely tiny and dense place which suddenly exploded, and has been expanding ever since

Question 2

what evidence supports the big bang theory?

Answer 2

red-shift:
- if we examine the light spectra for distant galaxies we can see that the wavelengths of the light have become longer
- this redshift tells us that the galaxies producing the light are moving away from us.
- the further away a galaxy is, the greater its red-shift, so it is moving even faster, so the universe is expanding
cosmic microwave background radiation:
- microwave radiation can be detected everywhere in the universe
- these are the stretched remains of high-energy gamma radiation that would have been produced in the explosion that created the universe

Question 3

what is the doppler effect?

Answer 3

if something that emits a wave moves whilst it is doing so then the wavelength of the sound will become shorter as it is moving towards you, increasing the frequency, and stretched as it is moving away, decreasing the frequency

Question 4

what is the relationship between change in wavelength, wavelength, velocity of a galaxy and the speed of light?

Answer 4

change in wavelength/reference wavelength = velocity of a galaxy/speed of light

Question 5

what is the redshift in light received from galaxies at different distances away from the Earth?

Answer 5

the further away a galaxy is the greater its redshift and hence the faster it’s moving away from us