Which idea was the most interesting to write about?
The chapter on pulsars was fun to write about, because Jocelyn Bell's story of thinking she had discovered alien life as a graduate student is so compelling. Any student can imagine the mix of excitement and dread she must have felt at finding the pulsing radio signal from deep space, wondering whether she had made an embarrassing mistake or was party to some great breakthrough. The whole history of radio astronomy is fascinating too, coming out of post-war physics research.
What's a big misconception about the universe you clear up in this book?
People often ask what's outside the universe - but the universe includes everything. While it's not simple to clear this up - given there are plenty of wild theories of parallel universes and the like that are mind bending even to physicists - I hope I have given a flavour of the ways in which people have thought about the concept of the universe through history. Our horizon has expanded the more we have learned about the universe - it's vast scale was quite unimaginable even a century ago.
How did this book come about?
I wrote a similar book about physics. My background is in astronomy, and the chapters on astronomy in that book were bulging at the seams, so I thought it would be worthwhile to expand on those ideas in a separate book. Astronomy is such a rich subject, with a long history, that it needed a whole book to highlight its scope.
What is the future of the universe?
In short - we don't know. But there are several ingredients that would dictate it. If the universe is dominated by matter, then gravity will one day pull everything together and it may end in a 'big crunch' . Dark energy is a competing force, which would eventually pull everything in the universe apart - stars and planets and galaxies would all be stripped down to a bleak mist of subatomic particles. Or if both these forces - gravity and dark energy - are balanced, then the universe could gently keep expanding for ever. Astronomers are rushing to find out more about the dark energy term especially, as that was only discovered a decade or so ago so we don't know much about its effect.
What aspect of this book will people find most interesting?
Cosmology, the study of the universe as a whole, is fascinating to many people. But I hope that readers will also think about our solar system, and how much we are learning from space missions. The variety of landscapes and the possibility of crude foms of life on moons of Jupiter and Saturn are exciting and are inspiring missions in coming decades, to peer beneath the ice on Europa for example. Planets around other stars are also being discovered at a rapid rate, so astrobiology and exoplanets are areas to watch.