Earth

Image of Earth c.1972 AD

**Earth** is the third planet from Sol and is the only astronomical object known to harbor native life. It is one of many terrestrial bodies known to have water, although Earth is the only one in the Sol system to have liquid surface water. 71% of the planets surface is covered by the oceans, with the remaining 29% being made up of land. Earth has an active tectonic system, which are responsible for its mountain ranges, volcanoes and earthquakes. It also has an active magnetosphere, allowing the planet protection from solar winds.

Earth's atmosphere consists mostly of oxygen and nitrogen. Greenhouse gasses such as carbon dioxide trap a portion of the sun's energy close to the surface. Most energy is received by tropical regions, which is redistributed towards the poles by atmospheric and oceanic circulation. Climate is governed by many factors, such as latitude, elevation and proximity to oceans. In many areas, severe weather such as tropical cyclones, storms and heatwaves occur and dramatically affect life.

Earth, like the remainder of the solar system, formed over 4.5 billion years ago from the protoplanetary disk of the early solar system. During the first billion years of Earth's existence, the oceans formed and life emerged. As life spread, it had profound effects on the atmosphere, creating the modern nitrogen-oxygen atmosphere. Over the course of the next 3 billion years, 5 major mass extinction events took place with several other minor ones. Humans emerged 300,000 years ago, and spread across the planet, the population being approximately 12.5 billion. During the 20th and early 21st century, human activity had profound effects on the planet's environment although restorative actions taking place during the late 21st century and 22nd century have somewhat rectified the damage done.

## History

### Formation

Current theories project that 4.54 billion years ago, the planetesimal that would become Earth formed. By accretion, the primordial Earth grew, in a process that took 100 million years. During this time, Earth faced a cataclysmic impact from another protoplanet - Theia, which eventually formed the moon. Over the next 300 million years, Earth faced a heavy amount of asteroid impacts that would shape both it and the moon's geography

### After Formation

The atmosphere and early oceans were extremely hostile to any evolution of life - intense tectonic activities led to high volcanism, leading to a high CO2 atmosphere, and highly acidic oceans. After the Earth began to cool, stable tectonic plates formed and Earth began to geologically calm. However, the atmosphere was still highly toxic to any life

### Origin of Life & Evolution

Approximately 4 billion years ago, the first living organisms appeared in the deep oceans, likely near geothermal vents. Single celled life dominated the oceans for billions of years, largely anaerobic and reliant on consuming other cells for energy. However, approximately 3.5 billion years ago, the first photosynthetic organisms appeared and the atmosphere of Earth began to shift towards a nitrogen/oxygen one

Unicellular life persisted for over 1.5 billion years, until 2.1 billion years ago when the first multicellular life appeared. However, life remained relatively simple until approximately 535 million years ago, when life had an explosion of diversity and from which all modern clades of species emerged. Since the Cambrian explosion, there have been 5 major mass extinction events and many other minor ones, the latest being the Holocene Extinction taking place between 11700BCE and 2120AD, the official end of the extinction event.

### Human History

#### Prehistory

Human life emerged from other primates in East Africa between 5-13 million years ago, and distinguished itself from other species through its intelligence, ability to use tools and language. During this time, the human species left Africa and spread throughout Eurasia. While humans were becoming increasingly complex, they fundamentally remained as hunter-gatherers across the globe. However, human intelligence facilitated the development of agriculture 12,000 years ago. These developments occurred concurrently in different parts of the world - Mesopotamia, the Indus River Valley, the Yellow-Yangtze Basin and Central America. The surplus of food led to the creation of cities, which in turn led to the creation of trade, manufacturing and politics.

Metalworking emerged 8000 years ago with the creation of copper tools, soon followed by much more advanced bronze tools. True civilization began to emerge, most close to rivers; first in Mesopotamia with the Tigris and Euphrates, followed by the Egyptian civilization along the Nile River, the Indus Valley civilization in Pakistan and northwestern India , and the Chinese civilization along the Yangtze and Yellow Rivers. All featured governments, a complex economy and social structure, systems for keeping records, and distinct cultures and religions. More civilizations began to develop - Crete, Greece, Vedas and the Bantu all developed complex societies and became prominent on the regional stage.

#### Classical Era

Over the next millennia, smaller civilizations began to grow into larger regional empires - Persia, Greece, China, and India all became major powers. The growth of the Roman Empire in the 3rd century BCE brought much of Europe under its hegemony, including the entire Mediterranean coast, Britain and Mesopotamia. In the 4th century CE, the Empire split in half, and was further divided between groups of invaders. The Western Empire fell to the Visigoths in 476, while the Eastern Empire (known as Byzantium) lasted another 1000 years, before it fell in 1453 to the Ottoman Empire. In the rest of Europe, the Early Middle Ages was characterized by depopulation, deurbanization, and barbarian invasions. Eventually during the 8th century, stability returned somewhat amid the rise of the Frankish Empire and the strengthening of the Catholic Church. During the High Middle Ages, the era was characterized with the solidification of manoralism and feudalism, the Great Schism between the Western and Eastern Churches and the Crusades. The Late Middle Ages however were marked with catastrophe - Mongol invasions, plague and famine devastated the population of Europe, killing half of the population. The bloody end of the Middle ages gave way to the Renaissance, the Reformation and colonialism in the 15th, 16th and 17th centuries

In China, the region was first united by the Qin Dynasty, being followed by the Han. The Han Dynasty pioneered several advances in both technology and economy, building a vast trade network into Persia and Europe known as the Silk Road. Chinese dynasties would follow successive cycles of growth and collapse, which led to the Sui, Tang, Song, Yuan, and Ming dynasties between the 5th and 15th century.

#### Modern Era

The Early Modern Era was marked with rapid European expansion and colonization - the Americas were colonized, and international trade took off, with food, plants and populations being transferred between continents. New crops that came from the Americas via European seafarers, mainly maize and potatoes in the 16th century significantly contributed to world population growth. The Scientific Revolution changed humanity's understanding of the world and was followed by the Industrial Revolution, a major transformation of the world's economies. The Industrial Revolution began in Great Britain and used new modes of production—the factory, mass production, and mechanization—to manufacture a wide array of goods faster and using less labor than previously required. This, however, began massive industrial pollution and environmental damage which would shape the next 3 centuries of human history.

Geopolitically, European Empires lost territory in the Americas as they gained independence, but gained territory elsewhere, especially in Africa and Asia. Britain gained global dominance after the Seven Years War, and created the largest empire in history, colonizing India, Canada, Australia and much of Africa. Other European powers also colonized land - France conquered Indochina, the Sahara, Algeria and Madagascar. The Dutch gained Indonesia, and Russia colonized Siberia. Very few nations remained independent outside of Europe - notable exceptions being China, Japan and America. Within Europe, the "Great Game" began, as the powers of Europe attempted to maintain the balance of power as a whole while maximizing their own influence. Europe entered the 20th century at the height of its power

During the 20th century, the European world order began to collapse - World War One led to the collapse of several nations, including Austria-Hungary, Germany, the Ottomans and Russia. In the aftermath of the war, radical new ideologies gained prominence - communism took power in Russia, leading to the rise of the Soviet Union, while militaristic fascist dictatorships took power in Italy, Germany and Spain, who began the Second World War in 1939. This led to the deaths of at least 60 million people, and saw the deployment of two nuclear weapons. When the war ended in 1945, the United Nations was founded in the hope of preventing future wars. In the aftermath, two countries emerged as superpowers - the United States and the Soviet Union. Each was suspicious of the other, which led to the Cold War, a 45-year stand-off and arms race between the two powers. During this time, European powers decolonized their overseas territories, and European nations gradually formed a political and economic community, the European Union. The Cold War ended peacefully in 1991 after the Soviet Union collapsed, partly due to its inability to compete economically with the United States and Western Europe. The United States likewise began to show signs of slippage in its geopolitical influence during the early 21st century, as both the EU and China gained influence on the world stage.

During the 21st century, the decline of the American hegemony led to an increasingly hostile world. Inter-national conflict began to affect nations in Eastern Europe, Africa and the Middle East, which led the EU to pursue policies increasingly in favor of federation. China too began to expand its influence, building a vast web of economic partners in Asia and Africa. America meanwhile focused on improving its domestic situation and securing its position in the Pacific sphere, building strong relations with Japan, Taiwan, Korea and Australia. In 2051, the Third World War began, which pitted the United States and European Union against the People's Republic of China for global dominance. While the US and EU won the war in 2054, leading to the replacement of the authoritarian government with the democratic Taiwanese one, the conflict caused the collapse of the global diarchy, and gave rise to the current global triarchy between the United European Federation, United States of America and Second Republic of China.

After the war, geopolitics began to stabilize as the new global order reestablished peace. Focus began to shift away from geopolitical dominance towards improving living standards, and space exploration. Lunar colonization had already taken place, and the body had declared itself independent in 2051 amid the outbreak of WW3. This pattern of colonization followed by independence would follow for colonies on Mars and Jovian moons. Despite this, Earth nations maintain a significant presence in space, with the asteroid belt and interplanetary orbits being thoroughly colonized. On Earth, the increasing intensity of the climate crisis led to several nations falling into anarchy, prompting mass migration and war throughout Africa and Asia.

As of the 2150s, humankind has reached a population of 12 billion on Earth, greatly stretching global resources. However, recent breakthroughs in FTL travel have opened up opportunities for humankind to expand its frontiers beyond the Solar System. Concern has been raised, however, that such an expansion of the frontier will lead to another collapse of the relatively-stable global order.

## Geology & Geography

### Surface

The total surface area of Earth is about 510 million km, and is home to many distinct climates and ecological biomes, ranging from tropical rainforests around the equator, to arctic ice sheets at the poles. Most of the surface is made of water, in liquid form or in smaller amounts as ice, 70.8% of the surface consisting of an interconnected ocean, making Earth a lower class of ocean world. At Earth's polar regions, the ocean surface is covered by a seasonally variable amount of sea ice that often connects with polar land, permafrost and ice sheets, forming polar ice caps.

Earth's land is 29.2% of Earth's surface area. Earth's land consists of many islands around the globe, but mainly of four continental landmasses, which are, from largest to smallest: Africa-Eurasia, America, Antarctica, and Australia. The terrain varies greatly and consists of mountains, deserts, plains, plateaus, and other landforms.

### Internal Structure

Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical properties. The outer layer is a solid silicate crust, beneath which is a highly viscous solid mantle. The thickness of the crust varies from about 6 kilometers (3.7 mi) under the oceans to 30–50 km (19–31 mi) for the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, which is divided into independently moving tectonic plates. Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core. The radius of the inner core is about one-fifth of that of Earth. Among the Solar System's planetary-sized objects Earth is the object with the highest density.

### Atmosphere

The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), allowing life and liquid water to exist on the Earth's surface, and reduces temperature extremes between day and night

## Human Geography

### Geopolitics

   The Earth is divided into 189 nations. The majority of nations can be placed into the spheres of three global powers - the United States of America, United European Federation and the Second Republic of China. There are also a number of secondary powers, which wield substantial - albeit limited - influence on the world stage. They include the Russian Federation, the Republic of India, the Republic of Turkey, Saudi Arabia, and the East African Federation.

Many of these nations are unified through military alliances, political unions and economic treaties. Examples include the European Union, NATO, Five Eyes, Asian Economic Union, and the Eurasian Federation. Most of these states together form the United Nations, the leading worldwide intergovernmental organization. The UN is responsible for mediating conflict, responding to crisis' and promoting global unity. In recent years, the UN has taken a more direct role in responding to crisis', directly taking control of territory in Mexico, Central Africa, Somalia and Egypt, in response to conflict in those regions.

### Natural Resources

Earth has resources that have been exploited by humans. Those termed non-renewable resources, such as fossil fuels, are only replenished over geological timescales. Large deposits of fossil fuels are obtained from Earth's crust, consisting of coal, petroleum, and natural gas. These deposits are used by humans both for energy production. Mineral ore bodies have also been formed within the crust through a process of ore genesis, resulting from actions of erosion, and plate tectonics. These metals and other elements are extracted by mining, a process which often brings environmental and health damage.

Earth's biosphere produces many useful biological products for humans, including food, wood, pharmaceuticals, oxygen, and the recycling of organic waste. The land-based ecosystem depends upon topsoil and fresh water, and the oceanic ecosystem depends on dissolved nutrients washed down from the land. In 2019, 34 million km2 of Earth's land surface consisted of forest and woodlands, 11 million km2 was shrub and grassland, 40 million km2 were used for animal feed production and grazing, and 16 million km2 were cultivated as croplands.

### Humans & the Environment

Human activities have impacted Earth's environments. Through activities such as the burning of fossil fuels, humans had been increasing the amount of greenhouse gases in the atmosphere, altering Earth's climate dramatically throughout the 21st and early 22nd centuries. It is estimated that global temperatures in the year 2120 were 2.2 °C warmer than the preindustrial baseline. This increase in temperature, known as global warming, has contributed to the melting of glaciers, rising sea levels, increased risk of drought and wildfires, and conflict in impoverished nations. However, joint action throughout the 22nd century has resulted in climate change slowing dramatically, and in 2139, the UN declared that it was the first carbon negative year in modern history. However, damage caused to Earth's ecosystem and polar ice caps is not expected to recover for centuries.