From Mars to the Multiverse

Powerful instruments had led to astonishing progress in tracing the emergence of atoms, galaxies, stars and planets from a mysterious ‘beginning’ nearly 14 billion years ago. Unmanned spacecraft have visited the other planets of our Solar System (and some of their moons), beaming back pictures of varied and distinctive worlds. An exciting development in the last two decades has been the realisation that many other stars are orbited by retinues of planets — some resembling our Earth (and capable of harboring life). Looking further afield, observers can probe galaxies and the massive back holes at their centres and can check models of their evolution by detecting objects all the way back to an epoch only a billion years after the ‘big bang’. Indeed we can trace pre-galactic history with some confidence back to a nanosecond after the ‘big bang’. But the key parameters of our expanding universe — the expansion rate, the geometry and the content — were established far earlier still, when the physics is still conjectural but is being constrained, especially by precision measurements of the microwave background. These advances pose new questions: What does the long-range future hold? Should we be surprised that the physical laws permitted the emergence of complexity? Are there other ‘big bangs’?