In DepthOpinion

A universe of surprises

We may think we understand the nature of the universe, but Lawrence M. Krauss reminds us science always has the potential to surprise.

A collage of Jupiter and the Galilean moons

Galileo's discovery of four of Jupiter's moons revolutionised our understanding of the universe in the 17th century (Source: NASA)

The excitement was palpable when on March 12, 1610, Galileo Galilei announced to the rest of the world that a hidden universe existed just beyond the reach of our eyes.

On the day of publication, the British ambassador to Venice dispatched a copy of Galileo's new book to King James I, promising him: "The strangest piece of news (as I may justly call it) that he hath ever yet received from any part of the world; which is the annexed book (come abroad this very day) of the Mathematical Professor at Padua, who by the help of an optical instrument… hath discovered four new planets rolling about the sphere of Jupiter, besides many other unknown fixed stars."

I think it is hard for anyone living at the beginning of the twenty-first century to truly appreciate how remarkable it must have been to suddenly learn that even our own solar system was not what it seemed to be. Suddenly, four new neighbors of the Earth revealed their existence. Could there be many more? And if the rest of the solar system "rolled about" the Earth, why did these four new interlopers orbit Jupiter?

Even the vast power of the Catholic Church at the time could not stop the revolution that was about to unwind as a result of this simple observation by a mathematician (for there were not yet "physicists") at a small but renowned university in Padua.

To try to understand the impact of this revelation at that time, imagine that evidence is unearthed (or more accurately, "unmarsed") today implying that two billion years ago intelligent life had flourished on Mars, only to die out without leaving a visible trace on the planet's surface today. The shock would be enormous, and the implications of such a discovery would be likely to shake theological foundations at least as much as those of Copernicus or Galileo ever did.

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Life on Mars?

Of course, everything we know about Mars, and everything we know about the evolution of life, argues against such a possibility.

Nevertheless, I once had a debate with a reader of one of my books on the subject of possible past intelligent life on Mars. This individual was no kook. He wasn't claiming, for example, that the afternoon shadows that accidentally produce, from a certain angle, what appears to be a face on the Martian surface was, as others have claimed, evidence of some early lost civilization. Rather, he was arguing just the opposite.

We know that billions of years ago, liquid water flowed on a warmer Martian surface, and the planet may have seemed ripe for life to evolve. His point was that no visible trace of any civilization that may have lived and died over 2 billion years ago would be left, due to the ravages of time. Therefore, how could we dismiss this possibility?

On the surface (if you will forgive the pun), this argument cannot be dismissed out of hand. Two billion years is a very long time. However, Mars has far less geological activity than Earth does, so the crust of the planet is not regularly recycled.

Thus, while obvious evidence from space of ancient cities might be difficult to detect, evidence for past intelligent life on the surface should be possible to uncover even utilizing unmanned probes.

This is not to mention the fact that, on Earth at least, it took more than a few billion years for living systems to evolve to become self-aware.

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Without a trace

Nevertheless, this got me thinking about Earth. If we annihilate ourselves tomorrow, will there be any significant evidence two billion years from now of our ever having populated the planet?

The Earth is, after all, a dynamic planet. Our present continents are newcomers on the scene. Moving at roughly the rate at which fingernails grow, they are drifting apart in a measurable way.

Two hundred million years ago they were joined together in a single supercontinent, now labeled Pangaea, and several hundred million years before that in a previous supercontinent. In the intervening years, the continents pulled apart, then rejoined in different patterns.

The material of the continents is floating on a layer of denser rock, and convection forces in the planet are causing the Earth's crust to be recycled over the course of hundreds of millions of years. Material at the interface of colliding continents is driven down, or subducted, into the mantle below, to be heated and melted by the intense heat and pressure deep down in the Earth, while fresh material is spewing out of volcanic ridges in the middle of the oceans.

Will there thus be any direct trace, on the planet's surface, of New York City, the Pyramids at Giza, or the Great Wall of China two billion years from now? Probably not, although some buried artifacts might survive this turmoil.

This is not to say that a future alien paleobiologist who visited this planet wouldn't be able to deduce that complex living organisms once roamed its surface and perhaps changed its environment over their four-billion-year heyday, even if no artifacts were discovered. But it is nevertheless not so clear that if humanity were to perish soon, our existence would ever be noted in anyone else's galactic history books.

There may be hope, however. We face the same challenge today if we try to look back billions of years to unravel the mysteries of our emerging planet.

But new relic evidence of the early moments of the Earth's history is constantly being uncovered, so that previous large gaps in our understanding are being filled in, and a coherent four-billion-year history is evolving.

Lawrence M. Krauss is a theoretical physicist, lecturer and bestselling author. He is currently in Australia as one of the 2009 National Tour guests for National Science Week. This is an edited extract from his book Atom: A Single Oxygen Atom's Journey from the Big Bang to Life on Earth… and Beyond.

Published 19 August 2009