There has been a lot of talk about colonisation of space. Why?
It is claimed that space colonisation is necessary to save the human race from natural catastrophies like a massive asteroid impact, or a super volcano (a caldera), or may be the Earth will become so polluted and overpopulated that life on Earth will become unbearable. Some people say that in a few centuries, climate change might make life on Earth so difficult that space habitation will make much more sense or looking long term - in a few hundred million years or more - the Sun will be so hot and big that the Earth will lose all its water and our scorching planet will become uninhabitable.
I think the reason that we shall start to colonise space sometimes in the near future is really very simple; space is there and technology is making it possible to colonise it. Other rationalisations have to be misguided as they do not stand up to scrutiny. Earth provides a far better survival strategy than any extraterrestrial colony - on a planet or in orbit. In any case, none of the events in the first paragraph will completely annihilate the human race. More people will survive on the Earth after an asteroid collision than we can possibly put in space - at least in the next century or so. Some say that space is vast and can be home to trillions of people; why restrict ourselves to the Earth that can only support 10 billion people at most? I find this rationale the most bizarre. Procreation is fine but why one should plan for unfettered population growth is beyond comprehension. Within the next 50 years, new technologies are predicted to give us machines (the silicon life) which will have intelligence similar to humans and then soon after they will acquire overwhelming superiority over the humans, representing the carbon life. Who, at that stage, will be concerned about the survival of the human race?
One of big unknowns is the effect on astronauts of long-term exposure to galactic cosmic rays, supposed to be remnants of supernova explosions. Cosmic rays consist of high energy charged particles with immense penetrating power and would be impossible to shield against. Thankfully, the Earth is surrounded by a magnetic field and this magnetosphere deflects most of the cosmic rays away from us. In fact, a 2015 study (funded by NASA) has found that mice with long-term exposure to cosmic ray like high energy particles experienced decline in cognition and changes in the structure and integrity of brain nerve cells and the synapses where nerve impulses are sent and received. Extrapolated to humans, this observation will make the idea of space colonization untenable by us - the carbon based life form. Robots will not be affected by cosmic rays and will be ideal for harnessing the wealth available in space. More of it in the following.
One also needs to consider the impact of new technologies. For example, nanotechnology, if one believes the projections, will give us nano-sized robots that will eat away the pollution. Manufacturing will be bottom-up with zero wastage and food will be synthesised in the laboratories. Earth can support much greater populations in a clean environment. Of course, the same nanotechnology developments will make space colonisation so much more efficient. We would not need vast fields in space for agriculture. Currently proposed conceptual designs of acres of agricultural land will be obsolete before they are needed.
My feeling is that space colonisation will happen but more as space tourism where one goes, to a space colony few hundred miles above the Earth to enjoy the wonderful views of the Earth, planets and the stars. Zero gravity recreation will be a novelty to be enjoyed to the full. Space colonies will be places for specialized manufacturing and scientific research. The only thing that still needs developing is a way to launch payloads more cheaply so that the cost of a holiday in space is affordable and commercial enterprise can fluorish. The prospects are looking promising.
Human societies have existed on the Earth for a few thousand years. Complex social behaviours, legal systems, political and religious ideologies have evolved over this period. The process has not been peaceful and there is little hope that homo sapiens will learn to live peacefully as a specie in future. Egocentricism and pursuit of power have dictated lot of what has happened in the past and it will be daydreaming to assume, as many proponents of space colonies populated by trillions of humans appear to think, that once in space everybody will live harmoniously in the best spirit of cooperation exuding peace and happiness. Putting people in space is not enough - how life in space is to be managed must be considered first. I see little point in creating space outposts loyal to individual nations on earth. A demonstrable system of governance must be developed before enormous national resources are spent.
We can also argue that to safeguard the survival of the human race from natural (asteroid or comet impact or a caldera or ice age onset in a few thousand years) or man-made causes (full scale nuclear war, ultra-polluted ecosystem, anthropogenic climate change) can best be ensured on the earth itself. What is needed is some proper planning; suitable colonies will provide far cheaper and better provision for human survival than colonies on Mars or the Moon or in orbits around the Earth. And it can be done in the span of a decade and with certainty with current technology. This is how it will work:
Suppose we wish to ensure survival of 1 million people. Using widely accepted numbers; to launch a payload in space just now costs about £5000 per kg and each person needs about 5 tons of payload. To provide a living place in space will cost £25 million per person. To do that for a million people will cost £25 trillion. This is a lot of money! Technology will help to bring this down somewhat.
Return journey to Mars will take two years and if we take 20 people per trip and if 100 space crafts work continuously, then it will take 100 years to put a million people on Mars. Colonisation of the Moon or an orbital colony will be very much quicker and manageable timewise but the cost will not be much lower.
The planetary colonies will be built underground in pressurised domes. Mars has a gravity of 0.3g and the Moon's gravity is 0.16g - and it is not clear how this will affect the humans. Movements outside the colony will have to be in protective bulky and awkward suits.
On the Earth, provision of a series of colonies, let us say similar to those on Mars or the Moon, will be trivially simple and much cheaper. The Earth has some enormous caves that could provide environment safe from radiation from a nuclear holocaust or dust clouds from a super-volcano or massive astreroid strike. One hundred such caves, each housing 10,000 people will need to be developed. Assuming that 2000 houses are built per cave and each house costs a million pounds then the total cost of the colonies will be £100 billion. An equal amount will be needed for other provisions like energy production (nuclear), ventilation, communication etc. Food supply for five years can be stored as canned food and is easy to organise.
The earth colonies described above assume the most pessimistic scenario. Even after a catastrophic event, life outside is not going to be totally impossible but the colonies provide a fail-safe survival strategy.
The above 'back of the envelope' calculation demonstrates that even without the help of new technologies, earth based colonies provide far better option (in fact the only option) to safeguard, with current technologies, human survival against major catastrophes. In fact, it is advisable that nations of the world embark on the construction of such colonies with urgency. It is possible that in the future, with new robotic technologies, humans can establish space colonies (the Moon appears to be the best candidate for this) that can provide unlimited energy, materials and even fresh water to the Earth. Robots do not require the same life support systems; in fact, most practical difficulties in maintaining humans in space disappear with colonisation by robots.