View of the crescent moon through the top of t...
View of the crescent moon through the top of the earth's atmosphere. Photographed above 21.5°N, 113.3°E. by International Space Station crew Expedition 13 over the South China Sea, just south of Macau (NASA image ID: ISS013-E-54329) - Wikipedia

Earth is the third planet from our sun with orbit between Venus and Mars. The Earth’s diameter is 12,756 km with a distance from the sun of about 150 million km and a circumference of 40,075 km. It’s inner core, the geosphere, is composed of solid, pressurized iron-nickel. This is surrounded by a hot liquid outer core composed of various substances.

The next layer, the mantle, is composed of solid rock which rises, falls and shifts over time due to pressure changes caused by temperature fluctuations. From this, the positioning of the continents is in a constant state of flux. Their slow but inexorable movement is called continental drift.

The next layer, the lithosphere, is composed of different rock forms and lies about 8 to 40 km underneath the visible continents.

The Earth’s atmosphere is mostly composed of oxygen and nitrogen. Theories about the formation and age of the Earth vary, but it’s generally believed that due to gravity a cloud of gas condensed about 4,550 million years ago, forming a ball which eventually took shape as the Earth.

Today the Earth is not a perfect circle. It is flattened at the poles and bulges a little at the equator. The Earth rotates on an axis about 23° off the vertical, this being determined by its orbital path around the sun.

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