Geography for Scrubs/The Earth

The Earth The Third Planet of our Solar System. thumb|The World is made up of 197 almost-universally recognized fully recognized sovereign states. The Earth is the third planet of our solar system and the only known planet to harbor life. The Earth has 7 continents (5 or 6 depending on what you define as a continent) and has a varying climate depending on weather, season, location, etc. The Earth is often referred to as "Terra", "World", "Globe", "Gaia" or "Terrus", all of which having different meanings from "Earth". The Earth has 4 Major Geoglogical Sub-Systems, which are the Geosphere, Hydrosphere, Atmosphere, and Biosphere. Just like on other planets, earthquakes occasionally happen on Earth, which are caused by the collision of tectonic plates. Due to this reason, earthquakes commonly happen on places that connect 2 tectonic plates, such as Turkey, Russia, Japan, Indonesia, Mexico, etc. There are currently 8 million known species on Earth, varying in size, behavior, and more. The Earth has a circumference of 40,000 kilometers, and a diameter of 12,742 kilometers. Assuming the average human has a walking speed of 5/kmh, it would take the average human 1 year of non-stop walking to circle the earth once. The Earth is split into the Northern- and Southern Hemisphere by an imaginary line called the eqautor. The Earth was formed 4.5 Billion Years ago, likely due to asteroids colliding with another, forming a huge, rocky planet. The Moon thumb|The Moon The Moon is Earth’s only natural satellite. A natural satellite is a small bodies orbiting a bigger one. The Moon called Luna to distinguish it from other natural satellites, which are commonly just called “moons” as well. The moon has a radius of about 1737.4 km, which is about 0.27 that of Earth. The moon is one of the largest natural satellites in the solar system. While nobody knows exactly how the moon formed, a popular hypothesis is that a smaller planet about the size of Mars struck Earth early in its history and the resulting debris formed the moon. The Moon is tidally locked, which means one side is always facing Earth. How much of that side is lit up by the sun is called a lunar phase. The Moon goes from a new moon (where none of it is lit up) to a full moon (where it is completely lit up) and back again with several phases in between. The Moon is the only astronomical object besides Earth humans have ever set foot on. The Continents A continent is a large area of land. The number and definition of “continent” varies between cultures. The four primary landmasses of Earth: Antarctica, the Americas, Afro-Eurasia, and Australia. The surrounding islands are divided up in different ways. The most common are: Seven continents Africa North America South America Europe Asia Antarctica Australia or Oceania (which includes New Zealand and much of the Pacific) Six continents, variation 1 Africa The Americas Europe Asia Antarctica Australia or Oceania Six continents, variation 2 Africa North America South America Eurasia Antarctica Australia or Oceania Five continents Africa The Americas Eurasia Antarctica Australia or Oceania For organizational purposes this book uses the first variant of the six continent model. Earth's Orbit The Earth travels around the Sun, and completes one orbit every year (about 365 days). The Earth is tilted slightly on its axis, which means some parts are sometimes getting more sunlight than others. This is what results in the seasons for much of the world. Seasons are opposite in the north and south - it’s summer in Australia when it’s winter in America, and vice versa. The middle regions of Earth, near the equator, do not experience seasonal changes due to getting the same amount of sunlight all year round. Climate The International Space Station