麻豆传媒

IN OUR everyday lives, time is a precious commodity. We can gain it or lose it. We can save, spend or waste it. If our crimes are revealed, we risk doing time.

But it is, of course, something we can measure. Indeed, clocks have, over the centuries, been the high-tech artefacts of their era 鈥� the water clock, the pendulum clock, Harrison鈥檚 chronometer, all the way up to the incredible precision of atomic clocks.

Before there was a reliable calendar of months and seasons, the past was a fog. But this didn鈥檛 stop efforts to impose fanciful, precise chronologies. According to James Ussher, Archbishop of Armagh in 17th-century Ireland, the world began in 4004 BC. Right up until 1910, bibles published by Oxford University Press displayed his dates alongside the text.

Even in Ussher鈥檚 time, many people were sceptical that the entire history of Earth鈥檚 mountains, rivers, flora and fauna could be squeezed into 6000 years. In the 19th century, Charles Darwin鈥檚 genius was to recognise how natural selection could have transformed primordial life into the amazing variety of creatures that have crawled, swum or flown on Earth. But he guessed that this higgledy-piggledy emergence, proceeding with no guiding hand, needed at least 100 million years; geologists inferred a similar span.

Radioactive dating now tells us that the sun and its planets condensed 4.5 billion years ago from gas in the Milky Way galaxy 鈥� itself part of a vast cosmos that emerged from a fiery 鈥渂eginning鈥� about 13.8 billion years ago.

What happened before the beginning? In the 5th century, Roman Empire philosopher St Augustine sidestepped the issue by conjecturing that time itself was created with the universe. The 鈥済enesis event鈥� is as mysterious to us, as it was to him.

However, our perspective on the future has no such limit. We know that our sun will shine for another 6 billion years before its nuclear fuel runs out. And the expanding universe will continue, perhaps forever, destined to become ever colder, ever emptier.

Maybe we aren鈥檛 even at the halfway stage in the progressive emergence of complexity in the cosmos. Any descendants of life on Earth who witness the sun鈥檚 demise (having long before then gained the ability to live at a safe distance) may be as different from us as we are from slime mould.

But even in the immense timescape that modern cosmology reveals, extending billions of years into the future as well as the past, this century is special. It is the first in the 45 million centuries of Earth鈥檚 history when one species 鈥搊urs 鈥� can determine the entire planet鈥檚 fate. We have entered the Anthropocene. Today鈥檚 decisions on environment and energy, empowered by our scientific knowledge, will resonate through future centuries.

Despite our awareness of the aeons to come, our planning horizons have shrunk because our lives are changing so fast. The political focus is on the urgent and immediate, and the next election. Medieval cathedrals took a century or more to complete. There are few efforts by public or private sectors to plan more than two or three decades ahead 鈥� or to build structures that will, as the cathedrals have done, offer inspiration for a millennium.

Humans may also acquire the capability to redesign themselves via genetic modification, or to deploy 鈥渃yborg鈥� techniques that enable them to implant in their progeny the advantages of electronic computers. This evolution via 鈥渟ecular intelligent design鈥� could operate far faster than Darwinian selection.

Perhaps our remote descendants will have a much-enhanced lifespan; they might even become near-immortal. Would they, like us, 鈥渟pend and save鈥� time as a scarce resource? Or would an overabundance lead to ennui? Only time itself can tell.

Martin Rees is the UK鈥檚 Astronomer Royal. Watch 鈥楳artin Rees interview: From the Big Bang, to a billionaire space race鈥� His latest book is

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