Space and survival

• 1. Introduction

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  Space and survival is the argument that humanity can only endure over the very long run if it builds a civilization that travels beyond Earth and draws on the resources of outer space. Its boldest claim is stark. Failing to do so might one day lead to human extinction.

  One reason for the argument is simple astronomy. In around one billion years, the gradually brightening Sun will make Earth uninhabitable. The descendants of today's humans will then have to live somewhere else.

  But the case does not rest on the Sun alone. Who first tied rockets to the fate of the species? Which dangers do researchers fear most, and can mere distance protect a civilization from them? And what would leaving Earth cost the people who go?

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• 2. A Warning From 1980

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  The earliest appearance of a link between space exploration and human survival is a 1980 article by Louis J. Halle, Jr. in Foreign Affairs. Halle reasoned that colonizing space would keep humanity safe if global nuclear warfare ever broke out.

  In recent years the idea has drawn more attention. Advancing technology is the reason. Reusable launch vehicles and combination launch systems are making affordable space travel look more feasible.

  A related observation adds urgency. The window of opportunity for building a spacefaring civilization may be limited, because the surplus resources available shrink over time as the population keeps growing.

  Halle's worry was one specific catastrophe. Later writers have tried to list the full range of threats, and their rankings are surprising.

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• 3. Where Danger Comes From

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  The Future of Humanity Institute draws a sharp line between two kinds of threat. Existential risks are those that could end the human species or cause a similarly severe and irreversible outcome. On a timescale of a few centuries, the Institute says, natural hazards look rather small, given humanity's long record of surviving them. Then comes its blunt conclusion: "The great bulk of existential risk in the foreseeable future is anthropogenic; that is, arising from human activity."

  Toby Ord develops the point in his book The Precipice. He names unaligned artificial general intelligence, pandemics, catastrophic climate change and global nuclear warfare. The pandemic danger he singles out is notably bioterrorism.

  Ord views all of these as more likely than natural catastrophes such as supervolcano eruptions or meteor impacts. Even so, he does not remove the natural ones from the picture.

  What can be done about any of these threats depends on how a species puts space between itself and a disaster.

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• 4. Distance as Defense

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  Pandemic control offers the clearest everyday model of the idea. Exposed people are placed in quarantine, and healthy people are evacuated away. The principle behind it is that extinction can be prevented by strengthening the physical barrier between people and the dangerous event, or by increasing the mean distance between them.

  The argument then turns to the human family tree. The genus Homo once included several species living side by side on Earth. Only one remains, because all the others became extinct before the end of the last Ice age.

  Proponents read this as a warning that Homo sapiens is not immune to planetary disaster. If so, human survival may be better assured by colonizing space.

  The question is whether any people are living off the planet yet.

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• 5. Backup Worlds

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  Consider a massive impact event that strikes Earth without warning. Under the argument's logic, the people closest to such an event are the most likely to be killed or injured. Those farthest away are the most likely to survive.

  Spreading humans across more places therefore raises the odds that someone lives through the event. Without any settlement beyond Earth, the species could become extinct, and its art, culture and technology would be lost. If colonies already existed elsewhere, the chances of survival and recovery would be greater.

  True space colonies do not yet exist. Yet people have lived continuously in space since 2000, aboard the International Space Station. The life-support systems that keep them alive there might also help people survive hazardous events.

  Survival in orbit is one thing. Seeing a threat coming before it arrives is another.

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• 6. Watching the Sky

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  Spaceguard is the collective name for some of the efforts to discover and study near-Earth objects. Those objects are asteroids, comets and large meteoroids that come close to Earth or collide with it.

  The logic behind such work is that observing and studying space protects Earth. Hazards can be seen in advance. If they are discovered early enough, people can act against them.

  There is a catch. The source behind this account says the Spaceguard efforts are not sufficiently funded.

  Watching the sky costs money, and so does everything else in this argument. Another price is paid by the traveler's own body.

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• 7. The Radiation Problem

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  Researchers from the University of Rochester Medical Center have studied what deep space does to the human brain. They found that radiation equivalent to that of a mission to Mars can cause serious brain damage. The harm they describe includes cognition problems and Alzheimer's disease.

  On Earth, living things are shielded by the planet's magnetic field and atmosphere. Outer space offers neither. Interstellar radiation is one of the biggest issues for the human body, among the many challenges of travelling there.

  A colony meant to rescue the species would first have to solve a problem that could injure the colonists themselves.

  Some critics raise a different kind of objection, one about motives rather than medicine.

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• 8. The Imperialist Critique

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  More contemporary commentators have examined the reasons given for space as a solution to survival. Some of them identify imperialist reasoning behind the push to explore space.

  Their complaint is that moving people elsewhere only relocates humanity's collective shortcomings. It does not solve them. On this view, a species that carries its flaws to a new world has not escaped the danger that Ord and others describe, because the danger is still human activity.

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