The end of the world: Five to seven billion years from now, the Sun will loom in our sky as a blazing 'red giant'.

Credit: Photolibrary

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WE HAVE SEEN HOW the universe is destined to end in darkness; what, then, is the fate of life? In an open universe, it would seem that every entity, every being, every thought, must come to an end. As philosopher Bertrand Russell once put it: "All the labours of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction … The whole temple of Man's achievement must inevitably be buried beneath the debris of a universe in ruins."

The Roman poet Lucretius must have had a similar vision in mind two millennia earlier when he wrote:

Again, perceivest not,
How stones are also conquered by Time?
Not how lofty towers ruin down,
And boulders crumble? Not how shrines of gods
And idols crack outworn?

In the late 1970s, however, physicist Freeman Dyson from the Institute for Advanced Study in Princeton, New Jersey suggested an alternative. Dyson defines life as any entity that can process information. Because this requires energy and generates heat, it would seem that an expanding universe offers less and less usable energy to keep such a system functioning. But Dyson imagined a way out: he suggested that life could, in effect, 'hibernate' for ever-increasing periods of time. By lengthening the span of the hibernation periods – effectively lowering their 'metabolism', so to speak – life could endure more or less forever, Dyson asserted.

The discovery of dark energy, however, may spoil Dyson's idea. Krauss, together with colleague Glenn Starkman, has argued that in a universe containing dark energy, life is doomed. Life requires energy, and in an ever-expanding universe it becomes more and more difficult to collect and harness that energy. "The cosmic dilution of energy is truly dire," they wrote recently.

As we become isolated in our respective island universes, the resources at our disposal become strictly limited. With finite resources, any living creatures (or equivalent machines) would have a finite memory. Finite information, they argue, implies a finite number of thoughts.

"Eternity would become a prison, rather than an endlessly receding horizon of creativity and exploration," they assert. In the long run, "life, certainly in its physical incarnation, must come to an end."

THIS IS NOT A PARTICULARLY HAPPY outlook for life, the universe and everything. But perhaps we can take away something positive from our speculation. First of all – and I seem to recall the late astronomer and author Carl Sagan saying something like this toward the end of his TV series Cosmos back in the 1980s: all those billions of years that lie ahead offer the opportunity to do a great deal of good. Further, it is quite impressive that with our finite hominid brains we have been able to peer so far ahead, with at least some degree of confidence.

And isn't it intriguing that the fate of the universe – trillions upon trillions of years from now – is clearer to us today than the fate of our own civilisation just a few centuries ahead?

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