WS MoreOrLess: How do we calculate the distance to the sun?

Two young listeners emailed the programme to ask how we calculate the distance to the sun. We decided to invite them and their parents to More or Less towers where Andrew Pontzen, an astrophysicist at University College London was on hand to explain the answer. A BBC nature documentary stated that there are 14,000 ants to every person on earth, and that were we to weigh all of these ants they would weigh the same as all the people. Can this be true? Tim Harford and Hannah Moore investigate with the help of Francis Ratnieks, professor of apiculture at the University of Sussex.