Our Sun is a fairly mediocre star, one of about 100 billion stars in our galaxy, the Milky Way. Then there are about 100 billion galaxies in the Universe. So surely, somewhere amongst all that, there must be some other sentient, intelligent, technologically advanced life forms? Well possibly, and possibly not.

Most people would say that somewhere, in that incredibly vast and multitudinous array of stars there must be inhabited planets. There must be societies with technologies far superior to ours, and aliens of weird, wonderful and even monstrous shapes. So, the imaginations of filmmakers give us little cuties like ET and Yoda, the fearful monsters of Predator and Independence Day, and the multitudinous marvels of Star Wars and Avatar.

Scientists are more circumspect, conscious that the laws of Physics will always dominate. Jabba the Hutt would squash under his own weight, and The Big Friendly Giant would, for the same reason, find his bones shatter as soon as he tried to stand up. The slimy ETs in Independence Day could not carry enough liquid to produce the copious amount of slime, and the slime would short out the electrics of the spacecraft while their talons (fingers), ideal for ripping out a human’s throat, are totally incapable of manipulating tools.

Of course, there are ways to envisage physically possible ETs that bear no resemblance to humans. C S Lewis, writing when scientists seriously considered there were canals carrying water across the Martian dessert, envisaged intelligent Martian physical creatures, and even super-intelligent non-physical beings. And Fred Hoyle, the astronomer, wrote a novel, The Black Cloud, with the idea of a living creature in the form of a massive inter-stellar cloud which almost pushes the Earth into permanent darkness as it comes close to the Sun to feed on its energy. The cloud is astonished to find that there is sentient life on the planet, life that is too primitive to be able to receive communication from the cloud.

However, scientists are divided on the possibility of extra-terrestrial, technological societies.

The view of biologists has been that life was an incredible event, statistically almost impossible, and unlikely to be replicated anywhere. The view of Jacques Monod in 1970 was, “The universe is not pregnant with life nor the biosphere with man…Man at last knows that he is alone in the unfeeling immensity of the Universe, out of which he emerged only by chance.” Others stressed our cosmic unimportance, describing mankind as a late arrival on an obscure clod of rock circling an insignificant star.

In a contrast to this, believing that alien civilisations must be out there among the stars, the SETI (Search for Extra Terrestrial Intelligence) Institute was established in 1984 to listen for radio signals that might have come from intelligent beings from some distant star. They have spent tens of millions of dollars using huge radio telescopes and computers to listen for signals that might have been deliberately produced by aliens. Seth Shostak, speaking to the Australasian Astrobiology Meeting in Auckland, admitted there had been no messages, nor signs of life in almost 40 years of listening, but felt that would all change if only he had massively more money and bigger radio telescopes and computers. Not everyone there was convinced.

I believe the truth lies between these extremes. We now know that the Universe began with about 70% hydrogen and 30% helium, and very little else. Everything else has been produced in stars, and the complex elements at the top end of the Periodic Table could not have been produced before the third generation of stars. The Universe had to be this old, and this big before macroscopic life could exist. Mankind is not late to the party, but right on time.

Equally outdated is the idea that the very first life, producing intricate order out of total chaos, was a contradiction of the Laws of Thermodynamics, and therefore impossible – except that it did happen. The Second Law of Thermodynamics records our observation that everything tends to break down and decay. Drop a cup on the floor, and it breaks. Throw the pieces up into the air and you don’t get a cup to form again. So, the intricate structure of a living cell cannot spontaneously form from the sludge in seaside pool. Right? Well, no. It’s a bit more complicated than that.

The Second Law of Thermodynamics says that, in any closed system, the entropy (the total amount of disorder) must always increase. Our planet, Earth, is not a thermodynamically closed system; there is a constant influx of energy from the sun as well as a constant flow of heat to the surface from the depths of the Earth.

The Universe is a closed system, but within any closed system you can still form a pocket of order (less entropy) by creating disorder (increased entropy) outside of that pocket. Freeze a jug of water, and liquid, devoid of any internal structure, is slowly replaced by highly structured crystals of ice while releasing heat into the wider region beyond the jug. The Universe is running down, order turning into chaos, but interesting things can happen on the way. The formation of planets, or of Life, still requires an overall increase in the amount of disorder, and so will speed the path of the Universe to its final, completely chaotic state. So “where energy gradients exist and conditions permit, life will arise not as a rare, fragile, and contingent accident, but inexorably as a driven phase transition to a lower-energy nonequilibrium steady state (Anne-Marie Grisogono). The creation of Life is thermodynamic imperative and must occur wherever the conditions are right. Life – microbial life – must exist throughout the Universe.

From microbial life to a technologically developed civilization is a different matter. Earth is the only example we have of how this might work. Here, it took almost 4 billion years, and a passage through numerous bottlenecks. But that’s for another blog.