Introducing "Smellyvision": this week, we talk about new tech that transmits smells alongside sounds and pictures, and ask whether smell is our most underrated sense. Also, are Bill Gates' fears that AI will erode our intellect well-founded, and why do some worry it might lead to better biological weapons? Meanwhile, how has Jonathan the giant tortoise lived to almost 200, and how long could a human theoretically survive? And why do scientists seem to say one thing one minute, and then change their minds a week later? Dr Chris Smith and Clarence Ford have the answers. Like this podcast? Please help us by supporting the Naked Scientists