Public lecture by Dr Clare Burrage as part of the 2014 Edinburgh International Science Festival. Billions of years ago the Big Bang sent everything flying apart. In theory, gravity should stop galaxies from moving apart and matter should eventually re-collapse on itself. Surprisingly, we have learnt that galaxies are actually moving apart with ever-increasing speed. Nothing in our current knowledge of physics can explain this, but theorists are developing a solution: dark energy. Roughly 70% of our universe is comprised of dark energy and yet so little is known about it, but satellite and laboratory experiments are under way. Join Dr Clare Burrage as she reveals the nature of dark energy, how it affects other matter in the universe, and what plans we have for observing this mysterious force. 5:30 pm — 7:00 pm on Friday 18 April 2014 at National Museum of Scotland, Edinburgh. royalsociety.org/events/2014/04/dark-side-of-the-universe/ Video cover image courtesy Nasa/ESA.