I just thought about it yesterday, and although is has been discussed here earlier, i'd like to raise the issue again. Can there really be more than one time dimension? so for instance, we could "circle around", come back, and pass through a moment we have already been through... it's quiet difficult for me to visualise the idea in practice, but it was mentioned that some forms of string theory incorporate just that... i wasn't able to find similar string solutions, so i could use some reference :) Also, is is possible that there is one time dimension for every space dimension? Oh, and one more thing :) as i've heard, there has been some progress (again, in String theory), whereby strings have gone through an ordeal in finite energies... does anyone know any articles, or papers, pointing to the decay of the vibrations? Thanks guys!