Higher Dimensions

What are dimensions, and why does the universe appear to have just three of them? Are there higher dimensions, and if so, how many? Is there a mathematical description of higher dimensions that does not involve physics? Is time a dimension, and if so, how is it different from the three spatial dimensions? Join us for what is sure to be a fascinating and mind-boggling discussion of this important topic. I will lead us off with a brief introduction (15 minutes or so), which will be followed up by a free-for-all discussion. Please be respectful of others and try not to dominate the discussion. Bombers will be booted and reported.