It may seem like a simple question, but the reality is anything but clear-cut.
Ben Miller's quest takes him to the frontiers of current science as he meets researchers working on the hottest and coldest temperatures in the universe, and to a lab where he experiences some of the strangest effects of quantum physics - a place where super-cooled liquids simply pass through solid glass. Plus, Ben installs his very own Met office weather station at home.
Ben's investigations in the personal and passionate film What Is One Degree? highlight the importance of measurement and accuracy in the 21st century.