It's difficult enough for most humans to grasp the idea that our planet is just one of countless others in our galaxy -- and a pretty small one, at that. Then, of course, there's the concept that our galaxy is just one of billions of others in the universe -- sure to compound any confusion considerably. It seems safe to say, however, that neither of those notions can compete on the mind-bending scale, so to speak, with an idea that's currently being investigated: The U.S. Department of Energy's Fermilab is working on a device to test the theory that our whole universe is simply a hologram.