Why is there a zeroth law of thermodynamics? What use is such a simple-sounding law? And how can it be used to smash g’’ll have explosive demonstrations, unique animations and even a musical number. Sign up to receive each instalment by email from rigb.org/advent The Ri is on Twitter: http://twitter.com/ri_science and Facebook: http://www.facebook.com/royalinstitution and Tumblr: http://ri-science.tumblr.com/ Our editorial policy: http://www.rigb.org/home/editorial-policy Subscribe for the latest science videos: http://bit.ly/RiNewsletter