The amplitude and frequency of such tides is affected by the moon's location as it revolves around the Earth. The gravitational pull of the moon creates a tidal bulge at the location directly beneath its location. Every two weeks or so, the moon aligns with the Earth and sun in a straight line -- the new and full moon phases -- resulting in the maximum gravitational force on our planet's oceans. These periods are referred to as spring tides..
http://d3fzrw9hngh8qa.cloudfront.net/glossary/CORECountries.mp4. According to a way of thinking about economies known as World Systems Theory, CORE countries are strong and wealthy countries that generate lots of wealth, and on which other countries depend. In the 14th century, Mongolia was a CORE country, and Italy was a peripheral country.
There are four core debates which permeate the study of nations and nationalism. First among these is the question of how to define the terms nation and nationalism.. Second, scholars argue about when nations first appeared. Academics have suggested a variety of time frames, including (but not limited to!) the following: 1  Nationalists argue that nations are timeless phenomena. 2  When man climbed out of the primordial slime, he immediately set about creating nations.