The Guardian hosts the two scientists and asks: "What problem do you hope scientists will have solved by the end of the century?" David Attenborough: "The production of energy without any deleterious effects. The problem is then we'd be so powerful, there'd be no restraint and we'd continue wrecking everything. Solar energy would be preferable to nuclear. If you could harness it to produce desalination, you could make the Sahara bloom." Richard Dawkins: "I was thinking more academically: the problem of human consciousness."