Define the celestial sphere. What will be an ideal response? ...

[TVarnum]

Define the celestial sphere.
 
  What will be an ideal response?

Question 2

The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar
 
  system.)
  A) Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
  B) Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
  C) Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
  D) Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

[vboyd24]

Answer to Question 1

An imaginary hollow sphere, with Earth at its center, on which all the stars (and other celestial bodies) are fixed. As the sphere rotates around the Earth, the stars move across our sky.

Answer to Question 2

C

[TVarnum]

Gracias!

[aliotak]

Excellent