Want to know how to tell whether an egg is fresh? Lower it into a bowl of cold water using a spoon: if it sinks to the bottom it is fresh, if it floats it isn't. If you want to know more, visit the Science on the Shelves website of the University of York which outlines the kinds of science you can discover on supermarket shelves. Produced by the university with support from Sainsbury's and the Engineering and Physical Sciences Research Council, it is aimed at families with six to 11-year-old children but is also useful for primary classrooms. It is part of the DfES's Planet Science project, managed by Nesta.