IN THE MATRIX (p5)

Being a cosmologist doesn't make me worry less than anyone else about what happens tomorrow or next week or next year. But it does give a different perspective, because cosmologists are aware of the long-term future. Most educated people are now aware that we as humans are the outcome of billions of years of evolution. Almost four billion years of Darwinian selection, separate us from the very first microorganisms. But most people nonetheless, at least subconsciously, feel that we as humans are a kind of culmination—that evolution led to us and that's that.

But, anyone who's studied astronomy knows that the sun is less than halfway through its life, and the universe may have an infinite future. So the time lying ahead, for evolution, is at least as long as the time elapsed up to now: the post-human phase of evolution could be at least as long as what has led from single-celled organisms to humans, and of course you only have to read science fiction to realize the scenarios whereby life can evolve here on the earth in more elaborate ways, and, more likely, can spread beyond the earth; life from the earth could even 'green' the entire galaxy, if given enough time. And that time does exist.

As a cosmologist I'm more aware of the immensely long-term potential that we'd be foreclosing if we screwed things up here on earth this century. This perspective gives us an extra motive for cherishing this pale blue dot in the cosmos, because of the importance it might for the long-range future of life even beyond the earth.

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I've been in cosmology for 35 years now, and what has been a tremendous boost to my morale is that the pace of discovery has not slowed up at all.  The 1960s seemed an exciting time. That's when the first evidence for the Big Bang appeared. It's also when the first high red shift quasars were discovered, along with the first evidence of black holes, neutron stars, etc. It was good to be a young cosmologist, because when everything's new, the experience of the old guys is at a discount and all had to start afresh.

But what's happened in the last three or four years is just as exciting as in any previous period that I can remember. In cosmology we have not only lots of fascinating ideas about how the universe began, ideas of how complexity developed, the possibility of extra dimensions playing a role, etc. But we also have new evidence which pins down some of the key numbers of the universe. We know we live in a flat universe where the atoms that make up us, the stars, the planets and the galaxies constitute only 4% of the mass and energy. About 25% is in mysterious dark matter, which helps with the gravitational binding of galaxies. And the remainder, 71%, is even more mysterious; some kind of energy latent in empty space itself. To explain dark matter is a challenge to physicists: it's probably some kind of particle left over from the Big Bang.

To explain dark energy is even more daunting: superstring theorists believe it is the biggest challenge to their theory, because it tells us that the empty space we live in, our  "vacuum," is something which isn't just nondescript; it has a well-defined energy, a well-defined tension in it, which affects the overall cosmic dynamics, causing an acceleration of the Hubble expansion.

Another important advance has been in understanding the emergence of structure within the universe. To put this in context, let's imagine how the universe evolved. It started off as a very hot fireball. As it expanded it cooled down; the radiation diluted and its wavelengths stretched. After about half a million years the universe literally entered a dark age, because instead of glowing bright and blue the primordial heat, the heat of the fireball, then shifted into the infrared, and the universe became literally dark. This dark age continued until the first stars formed and lit it up again.

One of my long-standing interests has been trying to understand when and how this happened. We've had some new clues recently from observations using giant ground-based telescopes, from the WMAP satellite, and also from being able to do computer simulations of how the first structures formed. We are trying to combine theories and observations to understand the formative stages of galaxies—how the first stars formed, in units much smaller than galaxies, then they assembled together to make galaxies, and how simple atoms of hydrogen and helium gradually get transmuted in early generations of stars into carbon, oxygen, silicon, and iron, the building blocks of planets and then of life.

We need to understand how long it took to get the first planets, how long it took to get the first potentiality of life, how long to get the first big galaxies from these small precursor substructures. More clues are coming from observations using the most powerful telescopes we now have—the biggest of all is the European very large telescope in Chile, which is really four telescopes, each with 8 meter mirrors, that can be linked together.

These huge mirrors allow us to detect very faint and distant objects. The further out you look in space the further back you look in time. The goal is to look back far enough to actually see galaxies in their formative stages—even perhaps to see pregalactic eras when the first stars were formed.