Earth is both the birthplace and the recurring test of human civilization: its resources sustain world-spanning societies, its environments are remade to serve them, and planetary change eventually makes it uninhabitable. Across successive human species, Earth’s history moves between technical achievement and collapse, until the Fifth Men must leave it behind as the Moon’s altered orbit threatens all life on its surface.

A Planet Remade for Civilization

Human societies progressively altered Earth to extend settlement and production across the globe. In one mature world civilization, seasonal agriculture, parks, and wild reserves spread between habitation and industrial districts, while broad freight routes crossed the continents and passenger travel was conducted through the air. The Sahara had become a lake district with holiday resorts; tropical currents warmed Canada’s Arctic islands; and Antarctica’s thawed coasts supported people exploiting the mineral resources of the interior.

This constructed landscape depended on energy drawn from the remains of prehistoric vegetation. Earth’s resources were not merely a backdrop to civilization: the means of obtaining and distributing power shaped transport, industry, settlement, and political order. The long history of attempts to meet those needs would repeatedly expose the limits of both technology and collective foresight.

Energy, Abundance, and Collapse

Antarctica became central to Earth’s energy system. Its coal seams were unusually rich, and the continent’s deep deposits had been preserved where central heat had not transformed them into graphite. After the founding of the First World State, Antarctic fuel was carefully husbanded, but oil supplies ran out in less than three centuries. Aircraft then relied on electricity generated from coal, while windmills, water turbines, volcanic power, and subterranean heat were developed as alternatives. None could replace coal on the necessary scale. The Sacred Order of Scientists prohibited the use of tidal power because its astronomical origin had come to be regarded as sacred.

Earlier, the World Fuel Control Board had imposed cosmopolitan control over existing oil and coal fields and restricted fuel use to purposes for which no other power source would suffice. When profitable exploitation of Antarctic fuel became possible, however, the deposits lay outside the Board’s jurisdiction. The United States sought to use them for its own advancement, while China demanded that the new sources be brought under international control. Their dispute combined resource competition with fear of cultural and political domination, and helped bring war within reach.

The First World State’s own coal supply eventually failed. The deepest borings in Antarctica disclosed no further deposits, despite a widespread belief that the continent’s coal was inexhaustible. Rather than curtail costly ritual flying, which consumed more communal resources than productive industry, the flying aristocracy and religious authorities urged an intensification of ritual devotion. Civilization collapsed amid this refusal to adapt. In the account of Earth’s longer history, repeated civilizations likewise rise and fail: the Third Men at different times built societies powered by wind and falling water, tides, and internal heat, each with distinct consequences for the planet and its inhabitants.

Power and the Changing Human World

Earth’s successive civilizations did not follow a simple path from scarcity to mastery. Patagonian researchers, after roughly five hundred years of intermittent work, discovered how to annihilate the positive and negative electric charges in a particular kind of atom. The process required a huge initial expenditure of energy and promised a readily controlled, effectively inexhaustible source, but it was not foolproof. Its discovery came in a society already divided by an unusually sharp class structure, leaving the new power in the hands of a population whose social conditions offered no guarantee against its foolish or inadvertent use.

By the Fifth Men’s era, artificial atomic disintegration and the annihilation of matter had made immense power available. Machinery performed transport, mining, manufacturing, agriculture, and much of the coordination of economic life. This removed the need for monotonous labor and gave individuals access to powerful mechanisms without giving them economic control over other people. Yet even this advanced civilization remained subject to a planetary limit that its comprehensive sciences could not explain.

The Moon and Earth’s Abandonment

The Fifth Men had long understood that the Moon should eventually draw near Earth after first receding, but expected the change to occur hundreds of millions of years later. Instead, observation showed that its withdrawal had stopped and its approach had begun to accelerate. Repeated measurements confirmed the anomaly, while the cause remained unknown. The prospect transformed a society preoccupied with the past: it now had to organize itself around a danger that lay in its future.

The Fifth Men calculated that, if the acceleration continued, the Moon would enter a critical zone and break apart in less than ten million years. Its fragments would then fall to Earth rather than remain in a stable ring; the heat of their impacts would make the planet’s surface impossible for life. The population therefore turned to the possibility of flight through space and considered Mars and Venus. Mars lacked water and atmosphere. Venus had a dense, moist atmosphere without oxygen, a shallow ocean covering nearly all its surface, and extreme heat even at the poles.

Humanity prepared Venus as a new home, but its limited land and living capacity required a drastic reduction in population: no more than one hundred million people could live there tolerably, about a hundredth of Earth’s former population. When the Moon grew large enough to turn day into night and night into a ghastly day, while its tides and the resulting weather damaged civilization, humanity reluctantly began its departure. The migration took centuries and carried not only the remaining human population but representatives of many other organisms and the most precious treasures of human culture.

Narrative Significance

Earth’s history links human institutions to material conditions without making technological progress a guarantee of survival. Coal abundance encouraged confidence in an inexhaustible supply; international fuel controls restrained waste but could not prevent new political conflict; and access to immense power repeatedly exceeded the capacity of societies to govern its use. The final crisis is different in scale: Earth is not simply depleted or politically divided, but threatened by a celestial process that human science can observe without yet explaining. Its abandonment makes the planet both the foundation of human history and the first home that humanity must relinquish.