A look back to the dawn


A look back to the dawn

Interview with Simon White, a cosmologist who will give a public talk in Dublin on how the entire universe emerged from an initial fog of matter, writes DICK AHLSTROM

TELESCOPES are like time machines. The deeper they can see into the night sky, the further back in time they allow us to travel.

Prof Simon White plans to take us back some considerable distance, more than 13 billion years to when the universe was just 400,000 years old.

At that point it would have looked as if it were nothing much more than a dense fog, no stars, no points of light, says White, a director at the Max Planck Institute for Astrophysics and one of the world’s leading cosmologists. “It is like looking up at the clouds on a cloudy day.”

If you have doubts about our capacity to achieve such an accomplishment, returning to within just a few hundred thousand years of the Big Bang that created the universe, White will convince you otherwise.

On Monday, October 12th, he will deliver the Dublin Institute for Advanced Studies’ statutory public lecture 2009 at University College Dublin. His talk is entitled: All from nothing: the structuring of our universe .

One of his key points is we don’t have to theorise about the evolution of the universe, we can actually see it. It is based on detecting the very weak, very difficult to see, leftover energy from the Big Bang, the cosmic microwave background radiation spread across the sky.

“We are seeing a direct image of what the universe looked like when it was 400,000 years old,” Prof White says.

Evidence of the microwave background radiation has been available since the 1960s and has been studied by several satellites. Early data from the Cobe satellite provided a very “smooth” microwave image, but the more recent and highly successful WMAP satellite (http://map.gsfc.nasa.gov/) had a sharper view and showed that the microwave background was anything but smooth.

Images provided by WMAP show the clumpy, inconsistent spread of what matter then existed, nothing more than broken up hydrogen and helium atoms and a still mysterious substance known to cosmologists as “dark matter”.

“As the universe expanded, it started cooling down and started to coagulate into lumps. That started when the universe was less than one billion years old,” White says.

Those lumps in turn became stars and galaxies, and still later, planets and moons. But studies of the microwave background also provided other details, he continued.

WMAP, and soon its successor, Europe’s Planck satellite, told us more about the make-up of the total universe. Just 4.6 per cent is made of the stuff we can see, baryonic matter including stars. The greater preponderance is invisible to us, with more than 25 per cent of the matter/energy mix made up of dark matter and an impressive 72 per cent made up of dark energy.

All three were there at the start, but dark energy’s role was apparently minimal. “The dark energy wasn’t doing anything at that stage but the dark matter was already having an effect,” he says.

We know that dark matter is important, given calculations which show that the visible matter in a galaxy isn’t enough to hold the whole thing together. Dark matter is there giving a “gravitational boost” to keep the galaxy from flying apart.

What this stuff is remains a mystery however. “We think it is a new kind of elementary particle, but that is a guess,” White says. But while this “dark matter problem” is difficult, still greater questions remain over dark energy.

“What has happened in more recent times is the universe has started expanding and that is the dark energy. We haven’t a clue what it is, it doesn’t seem to fit in with the rest of physics. It drives the cosmic expansion but it doesn’t interact with anything else.”

Not in doubt, however, is the contribution being made by dark energy to the rapid expansion of the universe. There won’t be any more matter, but there will be more space and so neighbouring galaxies will seem to disappear over the horizon leaving us very much on our own in the universe. “It looks as though it is heading towards becoming a really cold place.”


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