Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of. These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.
Answer:
Engular velocity: 
Linear velocity: 
The time it takes:

Explanation:
The magnitude of the centripetal acceleration can be related to the angular velocity and radius as:
(1)
Solving for w:
(2)
Replacing a=9,8m/s2 and r=6,375,000m:
(3)
And the angular velocity relates to the linear velocity:

The perimeter of the orbit is:

The time it takes:

There are 6 types of quarks.
Answer: C. 6
A piece of blue paper appears blue because the paper absorbs all colors of light except blue. <em> (b)</em>
So any light that bounces off of the paper and enters your eye must be blue light !
The mode in this case would be 125 because it occurs the most in the sequence of numbers.