Maybe an asteroid hit Earth. Perhaps a nuclear war reduced our cities to radioactive rubble. Whatever the cause, the world as we know it has ended and now the survivors must start again. But how do we set about rebuilding our world from scratch? Once you’ve salvaged what you can from the debris, how do you grow food and make clothes? How do you generate energy and develop medicines? And once you’ve mastered the essentials, how do you smelt metals, make gunpowder, or build a primitive radio set? ‘The Knowledge’ is a journey of discovery, a book which explains everything you need to know about everything.