IS OUR UNIVERSE THE ONLY ONE?

Might our universe – as vast as it is – be simply one of many? We look at the growing evidence that there's more than one cosmos out there

- DAVID BODDINGTON

In 1543, Prussian astronomer Nicolaus Copernicus lay dying. His life's work, On the Revolutions of the Heavenly Spheres, had just been sent off to be printed. This book, which explained that Earth rotates around the Sun, and not the other way around as had been believed, would forever change how humanity viewed its place in space. We were no longer the centre of the universe.

Nearly 500 years on, we're facing a similar revolution. The observable universe now stretches 46 billion light years in every direction, but physicists have compelling ideas about what may lie beyond.

It might just be that there are countless other universes, each one slightly different from the rest. Indeed, the results of a recent study of the cosmic microwave background – the thermal radiation left over from the Big Bang - make this seemingly outlandish proposition look increasingly likely.

Our universe began 13.8 billion years ago. A great exploding fireball of matter and radiation produced a hot plasma that quickly cooled, allowing subatomic particles to form within a few seconds. Over the next million years, atoms were created, and some 480 million years later these coalesced to form stars, planets and entire galaxies.

But the Big Bang theory, the theory about how the whole process got started, tells us nothing about the ‘bang’ itself. For that we need to look to another idea, called cosmic inflation. This theory says that in the first tiny fraction of a second after the Big Bang, the universe must have expanded faster than the speed of light.

Cosmic inflation theory was first proposed by American particle physicist Professor Alan Guth. In 1979, while working on equations to describe the early universe, Guth hit upon something astonishing: the false vacuum. This is unlike what we think of as a vacuum in that it's not empty. Rather, it's a material, and a powerful force in its own right – a force great enough to ignite an entire universe.