Space and survival
Space and survival is the idea that the long-term survival of the human species and technological civilization requires the building of a spacefaring civilization that utilizes the resources of outer space, and that not doing this might lead to human extinction. A related observation is that the window of opportunity for doing this may be limited due to the decreasing amount of surplus resources that will be available over time as a result of an ever-growing population.
The earliest appearance of a connection between space exploration and human survival appears in Louis J. Halle, Jr.'s 1980 article in Foreign Affairs, in which he stated colonization of space will keep humanity safe should global nuclear warfare occur. This idea has received more attention in recent years as advancing technology in the form of reusable launch vehicles and combination launch systems make affordable space travel more feasible.
Risk to humanity
Existential risk are risks of human extinction or similarly severe and irreversible outcome. According to the Future of Humanity Institute, "humanity's long track record of surviving natural hazards suggests that, measured on a timescale of a few centuries, the existential risk posed by such hazards is rather small. The great bulk of existential risk in the foreseeable future is anthropogenic; that is, arising from human activity." Toby Ord argues in The Precipice that some such risks include unaligned artificial general intelligence, pandemics, catastrophic climate change, and global nuclear warfare. He views these as more likely than natural existential risks, such as from supervolcano eruptions or meteor impacts.Some such catastrophes would ruin Earth's biosphere as well. Although many have speculated about life and intelligence existing in other parts of space, Earth is the only place in the universe known to harbor life. Eventually the Earth will become uninhabitable, at the latest when the Sun becomes a red giant in about 5 billion years. Humankind, or its intelligent descendants, if they still exist at that point, must leave the Solar System long before that to ensure survival of the human species.
Space settlement
Human extinction can be prevented by strengthening the physical barrier, or increasing the mean distance, between people and the potential extinction event. For example, pandemics are controlled by placing exposed people in quarantine and evacuating healthy people away. The human lineage of genus Homo has reduced from several species co-existing on Earth to just one — all others became extinct before the end of the last Ice age. This illustrates that Homo sapiens is not immune to planetary disaster and that human survival may be better assured through the colonization of space.Although space colonies do not yet exist, humans have had a continuous space presence since 2000 in the form of the International Space Station. Life-support systems that enable people to live in space may also allow them to survive hazardous events.