The Human Cosmos. Jo Marchant

      PROLOGUE

      Almost 14 billion years ago, everything burst out of nothing. Our universe pricked into being as an unimaginably hot, dense, tiny point, then almost instantaneously exploded outwards, the very fabric of space expanding faster than the speed of light, until all of existence was roughly the size of a grapefruit. After that, the universe continued to expand and cool, and the first matter formed. Within the first second, a dense soup of particles – neutrons, protons, electrons, photons, neutrinos – jostled in a smashing, searing heat that scattered light like fog.

      By the time it was about 380,000 years old, this cosmic bubble had expanded to tens of millions of light years across and cooled to a few thousand degrees, mild enough for atoms to hold together, and for the first time the universe became transparent to light. There was an initial flash of illumination, then darkness fell. It took several hundred million years for the attractive force of gravity to work on subtle density variations, inexorably collapsing clumps of gas to form the first stars and galaxies, and one by one, the celestial lights switched on.

      Most guides to cosmology tell some version of this sequence of events. Mysteries remain: Was this Big Bang really the start of everything, or is our universe just one inflating bubble in a much larger multiverse? What is the epic force that still pushes space apart? Will it keep expanding for ever, or eventually collapse again in a Big Crunch? But the general nature and story of the universe is agreed. Reality has been revealed as a vast and sophisticated machine, composed of physical particles and forces governed by mathematical equations and laws.

      This book tells a different story. The scientific account of the universe is a pinnacle of our modern civilisation, a vision so powerful that its rivals have been all but obliterated. Cosmology – the study of the cosmos – once described the broad philosophical and spiritual endeavour to make sense of existence, to ask who we are, where we are, and why we’re here. It is now a branch of mathematical astronomy. So what happened to those bigger questions? Is there nothing else about the universe we need to know?

      Instead of detailing the latest astronomical developments, this is a guide to the long history of knowledge that people have gleaned from the stars. It’s about what their view of the cosmos told them of the nature of reality and the meaning of life; about the gods and souls, myths and magical beasts, palaces and celestial spheres that we’ve discarded; about how the scientific view came to dominate, and how in turn that journey still shapes who we are today. It’s a tale about people – of priests, goddesses, explorers, revolutionaries and kings – and it starts not with the Big Bang, nor even with the birth of science, but with the very first humans who looked to the stars, and the answers they found in the sky.

       •

      Why bother about the celestial beliefs of the past? Archaeologists and historians often don’t. We know that science was built on attempts to understand the heavens, but this is rarely a focus for scholars tracing human progress more generally. I think this has created a huge blind spot in our understanding of where we came from. In fact, the patterns people see in the sky have always governed how they live on Earth, shaping ideas about time and place; power and truth; life and death.

      We see this in the ancient past: with the eclipse-obsessed Babylonians; the Egyptian pharaohs who built pyramids to guide their souls to the stars; the Roman emperors who fought under the banner of the sun. Ideas about the cosmos have shaped the modern world, too. These influences are still deeply ingrained in our society – even if we’ve forgotten their origins – in our parliaments, churches, galleries, clocks and maps. Beliefs about the sun, moon and stars played a central role in the birth of Christianity, and in Europe’s exploration and domination of the planet. They guided the rebellious lawmakers who founded the principles of democracy and human rights, the economists who developed the frameworks on which capitalism depends, and even the painters who produced the first abstract art.

      Today, as light pollution envelops our planet, the stars are almost gone. Instead of thousands being visible on a dark night, in today’s cities we see only a few dozen – and astronomers fear these will soon be vastly outnumbered by artificial satellites. Most people in the US and Europe can no longer see the Milky Way at all. It is a catastrophic erosion of natural heritage: