Earth's temperature is maintained at an average of 15 c because of our atmosphere's thickness the stagnant atmosphere the water cycle greenhouse gases

Because of the water cycle

The cooler part of the earth usually located on the higher ground ( such as mountain)

This cooler part of the earth could maintain water and keep it from evaporating and later on , transferred the water to the lower ground

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years