'You and I are made out of exploded stars,' Dr John Mather, joint winner of last year's Nobel Prize for Physics, tells Ronan McGreevy

Astrophysicists are not by reputation prone to demonstrative displays of emotion, but the standing ovation given to Dr John Mather at the American Astronomical Society in 1990 remains an event as unique as it is celebrated.

For 25 years, scientists had known that microwave background radiation from the Big Bang was everywhere in the universe, but proving it definitively was another matter.

Dr Mather persuaded Nasa to launch the Cosmic Background Explorer (Cobe) satellite in 1989 - and just nine minutes of data from Cobe was enough to prove what the scientific community had been guessing for decades. Their projections as to the brightness of the radiation and its temperature (2.72 degrees Kelvin or -275.72 degrees Celsius) were close enough to the data results as to be an exact match.

Last year, Dr Mather and his scientific partner, Prof George Smoot were belatedly awarded the Nobel Prize for Physics with a citation that their discovery had made cosmology a "precision science".

It went further than verifying the Big Bang theory. In the universe, where everything seems to be impossibly huge or impossibly tiny, the Cobe team detected fluctuations of 1,000th of a degree Kelvin in the cosmic background radiation.

It wasn't much, but it was enough. If the energy and radiation emanating from the Big Bang had been uniform, the universe would not have materialised as it did. The fluctuations allowed matter to form.

Without it, there would be no galaxies, no stars, no planets, no us, no nothing except atomic particles careering aimlessly into infinity. It was this part of the experiment which caused Stephen Hawkings to remark that Cobe was "the most important discovery of the century, if not of all time".

Sixteen years on and Dr Mather, a career Nasa scientist based at the Goddard Space Flight Centre near Washington DC, smiles as he recalls the graph that caused such excitement.

"It's a perfect curve. All the measurements fall on the predicted curve," he says. "It's simultaneously a beautiful experiment and a tremendous relief for all of the people that were worried that the whole story of the universe was wrong."

He points out repeatedly that all this is not a subject of arcane, academic interest, but goes to the heart of fundamental questions about us. What are we? Where do we come from? How did we get here? "You and I are made out of exploded stars. We're beginning to understand something about the forces of nature in the most extreme conditions in the earliest times. Before this was measured, we really had no idea what caused ourselves to exist," he said.

The process of understanding how the universe came into being will be enhanced when the James Webb Telescope (JWT) is launched in 2013. The JWT is a joint venture between Nasa, the European Space Agency (ESA) (which has Irish involvement) and the Canadian Space Agency.

As the chief project scientist, Dr Mather was in Dublin last week for a meeting of participants in the project at the Royal Hospital in Kilmainham. An impressive scale model, standing two storeys tall outside the hospital, shows the extent of the ambition involved.

The real thing will see almost as far as it is possible to see. Currently the Hubble Telescope, which JWT will replace, can see galaxies that are approximately 13 billion light years away. JWT will be able to see further than that and with greater clarity.

Because light takes so long to travel from the outer reaches of space, it is hoped to observe the birth of the first stars in the universe.

"It (Hubble) can see within a billion years of the Big Bang, we can see within 200 million years," he says. "The difference in the conditions of the universe between those two times is tremendous."

It is hoped the JWT will help solve a central mystery about the formation of the universe. The cosmic radiation dates from 380,000 years after the Big Bang when the first atoms started to form, but the first stars did not light up for hundreds of millions of years after that. It's known in cosmological circles as the "dark ages".

JWT will operate in the infrared spectrum, making it possible to study the formation of stars and planets in huge clouds of dust.

Another part of the JWT mission will be the study of exoplanets - planets outside our solar system that have brought the tantalising prospect of life in other parts of the universe closer than ever. Currently they are detected by the way their orbits dim the light of their stars. It is hoped that JWT will be able to see them directly.

"We don't know if there is any life outside ours, but we are getting much more able to look, though it might take another generation of even better telescopes," Dr Mather says.

"FOR MANY CENTURIES, people imagined that the Earth is very unusual, rare and precious and it is to us, but it is not so unusual that there be life elsewhere. I think we will find that there is life on other planets."

Dr Mather is sure the JWT will find things it is looking for, things it wasn't looking for and things we didn't know even existed. "I'm always overwhelmed. The more we keep looking, the more mysterious it really is. Every detail we find leads to more questions."

But, first the telescope has to work and with a price tag of €3.4 billion it had better work, though he points out: "It's way more powerful than Hubble, but it doesn't cost any more."

Hubble has needed the space shuttle to carry out repairs. There will be no such opportunity for JWT, which will be carried on board an ESA Ariane rocket and positioned a million miles from earth.

"We're not going to repair this one. We're planning to get it right the first one. We've been testing it like crazy."

Dr Mather has been a regular visitor to Ireland in the past and his presence at a lecture, sponsored by The Irish Times, in Dublin last week caused a buzz in the scientific community here.

Tall, angular and with glasses that could pass for the lens on the Hubble telescope, he projects an unworldly air and looks like the personification of a "world-class scientist" as he was described by Nasa Administrator Michael Griffin.

He also displayed a keen sense of self-deprecation and the timing of a stand-up comedian.

At the end, he invited "big questions" - apart from the banned list of ones he can't answer. What is time? What is space? What is our fate in the universe? What's at the centre of a black hole? Another on the banned list is what happened before the Big Bang? "This is way beyond me," he said to laughter, "I don't do this kind of stuff."

Neither does he "do God", as Alastair Campbell once said in another context, though his colleague Prof Smoot said the Cobe results were "like looking at God".

"I mostly say, let's figure that out privately and personally as best we can. It seems to me that there is plenty of mystery to go around in science," Dr Mather says.

"We don't know if there was a creator. The scientific evidence doesn't tell us one way or the other.

"We don't tackle the question of ethics, morality, survival after death - those kind of things are way outside the physical, chemical and biological sciences."

View the model of the James Webb telescope at the Royal Hospital Kilmainham, Dublin, 10am-5pm (Sunday 12-5pm)

The universe in numbers

Age:13.7 billion years

Size:Unknown, but possible infinite

Number of galaxies:125 billion

Number of stars:70,000 million million million

Number of planets:250 discovered, probably trillions

Number of intelligent civilisations:1,000 according to the Search for Extraterrestrial Intelligence Institute