Why did Hubble conclude the universe must be expanding? What ...

[casperchen82]

Why did Hubble conclude the universe must be expanding?
 
  What will be an ideal response?

Question 2

When an electron in a hydrogen atom changes its spin from the same to the opposite direction as the proton, it
 
  A) absorbs a visible light photon.
  B) emits an X-ray photon.
  C) emits a radio wave photon.
  D) absorbs a radio wave photon.
  E) neither emits nor absorbs a photon.

[mistyjohnson]

Answer to Question 1

He found the universe was not static, that the most distant galaxies showed us the highest recessional velocities and redshifts. He believed this was most easily understood by having all of spacetime itself expand, taking the galaxies with it.

Answer to Question 2

C