This week we've been against the clock to get the answer to this question from David "What measurement of time would you use in travelling through space as a day, week, month or a year would become meaningless, and how would this affect the body clock?" Eva Higginbotham spoke to space sleep expert Cassie Hilditch, and also former NASA astronaut Steve Swanson, to find out the answer... Like this podcast? Please help us by supporting the Naked Scientists