The Book of Universes

The most interesting consequence of inflation is that the period of faster accelerated expansion enables the whole of the visible part of the universe today (extending more than 14 billion light years across) to have expanded from a far smaller primordial fluctuation of mass and energy than was previously imagined to be possible – a fluctuation small enough to be kept smooth by light rays moving from one side to another.¹⁸ The high level of smoothness we observe in our universe is therefore just a reflection of the fact that in an inflationary universe the whole visible universe is the expanded image of a tiny fluctuation that is kept smooth and isotropic by photons of light moving excess energy from the hotter parts to the cooler parts.

Cosmologists have long appreciated that there is a surprisingly close link between the large-scale properties of the universe and the existence of life within it. At first sight this might appear odd. The universe is big. There are countless stars and galaxies extending billions of light years in every direction. How could any of that have a connection with us, here and now, orbiting an average star in an unremarkable galaxy?

The unexpected connection arises because the expansion of the universe links time and space. Chemical elements like carbon, oxygen and silicon that produce the complex structures on which ‘life’ is based do not appear ready-made in the universe when it starts expanding. Nor are they made during the primordial nucleosynthesis of deuterium, helium and lithium during the first three minutes of the universe’s history. Rather, they are made in the stars over billions of years through a sequence of nuclear reactions that first combine two helium nuclei to make beryllium, then add another to make carbon, then another to make oxygen, and so on. These processes take place as stars die and the elements they produce are spread around the universe when the dying stars explode as supernovae. Eventually, they find their way into dust and rubble that condenses into planets, and then find their way into molecules and people.

The production of carbon and steady hydrogen-burning stars like our Sun that sustain life-supporting environments needs billions of years of stellar alchemy to take place. This is why we should not be surprised to find that our universe is so old. It takes lots of time to produce the chemical building blocks needed for any type of complexity. And because the universe is expanding, if it is old, it must also be big – billions of light years in extent. If the universe were just the size of the Milky Way galaxy, with its 100 billion stars offering potential homes for planetary systems, it might seem room enough for lots of life. But such an economy-sized universe would be little more than a month old. No time for stars to evolve or for the building blocks of biochemical complexity to be formed.

Given the problems of environmental degradation created by advanced technological species, and the exhaustion of natural resources, we might expect that very advanced civilisations would have to move towards becoming technologically miniaturised. The state of advancement of a civilisation would be better gauged by its ability to engineer at smaller and smaller scales, rather than on larger and larger ones. Accordingly, one can classify civilisations according to their ability to manipulate molecules, atoms, elementary particles and space-time structure.⁵⁶ This means that the more advanced they become, the less visible are their technological activities because they use less energy and create smaller and smaller amounts of waste heat. Even their space probes might be no larger than clusters of atoms or molecules. We would not even notice them.