"Time is not, as it is sometimes believed to be, merely a dimension of the human mind, a necessary delusion of consciousness. And indeed, physics has found evidence of this. Einstein's and Minkowski's space-time continuum is the most modern and precise representation of our physical reality yet presented, and it leaves no doubt that our universe is four-dimensional, although the fourth dimension, time, has properties quite different from those shared by the three spatial dimensions. Above all, it is not as directly accessable by our senses. But we can at least appreciate that four types of measurements are needed to define the location of an event in our world, its spatial coordinates (e.g., logitude, latitude, and elevation) and its point in time."