This week on Ask the Naked Scientists we find out why a slipped disc can't slip out, why you forget your dreams and why digital radio is behind the times - by about 4 seconds! Also, why present day physics forbids travel to the past, and how you can carry someone elses DNA without being pregnant. We tackle these questions and more on this weeks podcast. Like this podcast? Please help us by supporting the Naked Scientists Like this podcast? Please help us by supporting the Naked Scientists