Collisions between galaxies: A) are much rarer than collisions ...

[Yi-Chen]

Collisions between galaxies:
 
  A) are much rarer than collisions between stars.
  B) can turn elliptical galaxies into spirals.
  C) cause large numbers of stars to collide and explode.
  D) cause the gas and dust clouds to collide, leading to rapid star formation.
  E) are the best explanation for gamma-ray burst events.

Question 2

Why are summers hotter than winters? Relate this to the Sun's position in the celestial sphere and the length of the days.
 
  What will be an ideal response?

[ttt030911]

Answer to Question 1

D

Answer to Question 2

The Sun is 47 degrees higher in the noon sky for northern hemisphere observers in June than in December, and also gives several extra hours of daylight as well.

[Yi-Chen]

TY

[ttt030911]

You're welcome