Why should we go into space? What is the justification for spending all that effort and money on getting a few lumps of moon rock? Aren’t there better causes here on Earth?
In a way, the situation was like that in Europe before 1492. People might well have argued that it was a waste of money to send Columbus on a wild goose chase. Yet, the discovery of the new world made a profound difference to the old. Just think, we wouldn’t have had a Big Mac or a KFC.
Spreading out into space will have an even greater effect. It will completely change the future of the human race and maybe determine whether we have any future at all. It won’t solve any of our immediate problems on Planet Earth, but it will give us a new perspective on them and cause us to look outwards and inwards. Hopefully, it would unite us to face a common challenge. This would be a long-term strategy, and by long term, I mean hundreds or even thousands of years. We could have a base on the Moon within 30 years or reach Mars in 50 years and explore the moons of the outer planets in 200 years. By ‘reach’, I mean with man or, should I say, person space flight. We have already driven Rover and landed a probe on Titan, a moon of Saturn. But if one is considering the future of the human race, we have to go there ourselves.
Going into space won’t be cheap, but it will take only a small proportion of world resources. Nasa’s budget has remained roughly constant in real terms since the time of the Apollo landings. But it has decreased from 0.3 per cent of the US’s GDP in 1970 to 0.12 per cent now. Even if we were to increase the international budget 20 times to make a serious effort to go into space, it would only be a small fraction of the world’s GDP. There will be those who argue that it would be better to spend our money solving the problems of this planet, like climate change and pollution, rather than wasting it on a possibly fruitless search for a new planet. I am not denying the importance of fighting climate change and global warming. But we can do that and still spare a quarter of a per cent of the world’s GDP for space. Isn’t our future worth a quarter of a per cent?
We thought space was worth a big effort in the 60s. In 1962, President Kennedy committed the US to landing a man on the Moon by the end of the decade. This was achieved just in time by the Apollo 11 mission in 1969. The space race helped to create a fascination with science and led to great advances in technology, including the first large-scale integrated circuits that are the basis of all modern computers. However, after the last Moon landing in 1972, with no future plans for further manned space flight, public interest in space declined. This went along with a general dissension with science in the West because, although it had brought great benefits, it had not solved the social problems that increasingly occupied public attention.
A new manned space flight programme would do a lot to restore public enthusiasm for space and for science generally. Robotic missions are much cheaper and may provide more scientific information, but they don’t catch the public imagination in the same way, and they don’t spread the human race into space which I am arguing should be our long-term strategy. A goal of a base on the Moon by 2020 and of a man landing on Mars by 2025 would reignite a space programme and give it a sense of purpose in the same way that President Kennedy’s Moon target did in the 1960s. A new interest in space would also increase the public standing of science generally. The low esteem in which science and scientists are held is having serious consequences. We live in a society that is increasingly governed by science and technology, yet fewer and fewer young people long to go into science.
Knock, knock. Who’s there?
What will we find when we go into space? Is there alien life out there, or are we alone in the universe? We believe that life arose spontaneously on the Earth. So it must be possible for life to appear on other suitable planets, of which there seem to be a large number in the galaxy.
But we don’t know how life first appeared. The probability of something as complicated as a DNA molecule being formed by random collisions of atoms in ocean is incredibly small. However, there might have been some simpler macro molecule that can build up the DNA or some other macro molecule capable of reproducing itself. Still, even if the probability of life appearing on a suitable planet is very small, since the universe is infinite, life would have appeared somewhere. If the probability is very low, the distance between two independent occurrences of life would be very large. However, there is a possibility known as panspermia that life could spread from planet to planet or from stellar system to stellar system carried on meteors. We know that Earth has been hit by meteors that came from Mars, and others may have come from further afield. We have no evidence that any meteors carried life, but it remains a possibility. An important feature of life spread by panspermia is that it would have the same basis that would be DNA for life in the neighbourhood of the Earth. On the other hand, an independent occurrence of life would be extremely unlikely to be DNA-based. So watch out if you meet an alien. You could be infected with a disease against which you have no resistance.
One piece of observational evidence on the probability of life appearing is that we have fossils from 3.5 billion years ago. The Earth was formed 4.6 billion years ago and was probably too hot for about the first half billion years. So life appeared on Earth within half-a-billion years of it being possible, which is short compared to the 10 billion-year lifetime of an Earth-like planet. This would suggest either panspermia or that the probability of life appearing independently is reasonably high. If it was very low, one would have expected it to take most of the 10 billion years available. If it is panspermia, any life in the solar system or in nearby stellar systems will also be DNA-based.
While there may be primitive life in another region of the galaxy, there doesn’t seem to be any advanced intelligent beings. We don’t appear to have been visited by aliens. I am discounting reports of UFOs. Why would they appear only to cranks and weirdos? Furthermore, despite an extensive search by the SETI (Search for Extra-Terrestrial Intelligence) project, we haven’t heard any alien TV quiz shows. This probably indicates that there are no alien civilisations at our stage of development within the radius of a few hundred light years. Issuing an insurance policy against abduction by aliens seems a pretty safe bet.
The strong and silent type
Why haven’t we heard from anyone out there? One view is expressed in this Calvin cartoon. The caption reads: “Sometimes I think that the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.” More seriously, there could be three possible explanations of why we haven’t heard from aliens. First, it may be that the probability of primitive life appearing on a suitable planet is very low. Second, the probability of primitive life appearing may be reasonably high, but the probability of that life developing intelligence like ours may be very low. Just because evolution led to intelligence in our case, we shouldn’t assume that intelligence is an inevitable consequence of Darwinian natural selection. It is not clear that intelligence confers a long-term survival advantage. Bacteria and insects will survive quite happily even if our ‘intelligence’ leads us to destroy ourselves.
This is the third possibility. Life appears and in some cases develops into intelligent beings, but when it reaches a stage of sending radio signals, it will also have the technology to make nuclear bombs and other weapons of mass destruction. It will, therefore, be in danger of destroying itself before long. Let’s hope this is not the reason we have not heard from anyone. Personally, I favour the second possibility that primitive life is relatively common, but that intelligent life is very rare. Some would say it has yet to occur on Earth.
Stephen Hawking is a theoretical physicist and is the Lucasian Professor of Mathematics at the University of Cambridge. He is the author of A Brief History of Time. This is an edited extract of the lecture he delivered on April 21 at the George Washington University, Washington DC, as part of the 50th anniversary Nasa lecture series.