And if they do - what would they look like? Where would they live? Would they be conscious beings? And what would happen if they found us? These are the biggest questions we've ever asked - and here, Professor Jim Al-Khalili, theoretical physicist and host of BBC Radio Four's The Life Scientific, blasts off in search of answers. Coming with him are Martin Rees, Ian Stewart, Louisa Preston, Monica Grady, Sara Seager, Paul Davies and a crack team of scientists and experts who've made it their life's work to discover the truth. So get ready to visit the ice boulders and hydrocarbon lakes of Saturn's moon Titan, meet the tiny eight-legged critters that could survive in space, and learn about the neuroscience behind belief in alien abductions. Along the way, you'll enter the mind of an octopus, work out the probability of us finding an alien civilisation and discover whether quantum computing might hold the secret to life itself. Lively, curious and filled with scientific insights fresh from the cutting edge of the Galaxy, Aliens is the perfect book for anyone who has ever looked up into the starry sky and wondered: are we alone?