What information do scientists use to estimate the total mass of ...

[daltonest1984]

What information do scientists use to estimate the total mass of the Milky Way Galaxy?
 a. The size of the galaxy from end to end.
  b. The number of stars and planets thought to be in the galaxy.
  c. The mass of Earth.
  d. The diameter of the galaxy.
  e. The fact that all the stars in the galaxy rotate about a common point.

Question 2

Which is the BEST description of what causes tides?
 a. Tides are caused by the Moon's gravitational pull on the Earth.
  b. Tides are caused by earthquakes.
  c. Tides are caused by the rotation of the Earth.
  d. Tides are caused by the gravitational pull of the Earth-Moon system.
  e. Tides are caused by the Earth's gravitational pull on the Moon.

[Chelseyj.hasty]

Answer to Question 1

e

Answer to Question 2

d

[daltonest1984]

Thank you!

[Chelseyj.hasty]

Always glad to help...