Tacit dimension of knowledge is the what we have learned from experience and from our interactions with all the circumstances in life. It can be said that this dimension is referred to as common knowledge, what we assume others know, or the unsaid. The major paradigm shift today is that we interact with the world to learn. In the book, "A New Culture of Learning: Cultivating the Imagination for a World of Constant Change" (by Douglas Thomas and John Seely Brown), the authors describe this new environment.
We have moved from the seeking task as limited or discrete (I ask a question and then I find the answer) to a continuous learning process where I seek answers and continually discover. The twenty-first century has shifted to the tacit dimension of knowledge where we learn by doing, watching, and experiencing. Try the book - its a insightful view of the sea changes we live in, especially in the educational arena.