A self sustaining reaction where some of the products are able to produce more reactions of the same kind is called a ________________.

The cosmic microwave background radiation is the ___________________.

Uranium-238 through a series of decay processes will eventually become _____.

Which of the following planets has no moons?

The temperature on the surface of Venus is hot enough to melt lead because _______.

The sun belongs to this class of stars.

The 180 degree meridian is arbitrarily called the __________________, an imaginary line established to compenste for the cumulative time zone changes.

The distance from the Earth to the sun in known as a(n) __________.

We always see the same side of the Moon because ______.

Jupiter’s Great Red Spot is presently believed to be ________.