As discussed in our recent article Lambda marks the spot — the biggest problem in theoretical physics, dark energy and the cosmological constant remains a controversial area that lies at the very edges of our understanding of the Universe. One of the contributors to that article, Subir Sarkar from the University of Oxford, recently took part in the Big Questions debate series at Imperial College in London, debating the fate of the Universe with Andrew Jaffe from Imperial. Jaffe argued for the existence of dark energy, while Subir argued that it was an artifact of the oversimplified cosmological model used to interpret observations. At the end of the debate, the audience was asked to vote on whether they thought dark energy exists, and Subir told us: "Given that I was attacking the standard cosmological model, it was a pleasant surprise when the audience voted decisively in my favour!"

James Darcy reported on the Big Questions debate in his physicsworld blog, and in a followup post published a clarification from Sarkar on some of the details.

Plus readers, always seeking an informed debate, voted to ask the experts "What is dark energy and dark matter?" in our last IYA09 poll. We'll be recording the answer to that question soon, so stay tuned. And once everyone has had a chance to hear both sides of the argument we'll open the debate on the Plus blog by asking you to vote on whether you think dark energy exists. Will Sarkar win the argument again? We'll have to wait and see..