Why is the cosmic microwave background (CMB) so cold if the early ...

[Pineapplelove6]

Why is the cosmic microwave background (CMB) so cold if the early Universe was so hot?
 
  a. Enough time has passed for matter in the universe to release enough heat to cool down.
  b. The CMB constantly interacts with atoms, which effectively cool down the photons.
  c. The expansion of the Universe has redshifted those photons to an effectively cooler temperature.
  d. Misleading; The big bang was initially hot but the CMB was released from cold material much later on.

Question 2

Explain the major differences between type II supernova and a type I supernova.
 
  What will be an ideal response?

[Sweetkitty24130]

Answer to Question 1

c

Answer to Question 2

Supernovae that do not have hydrogen lines in their spectra are called type I supernovae, and those that do have hydrogen lines are type II supernovae.

[Pineapplelove6]

Gracias!

[aliotak]

Excellent