It is often said that Einstein's theory of special relativity shows that time and space are parameters of the same ilk and that, physically, spacetime is more fundamental. In fact, if we define a coordinate t*=ict, where i is sqrt(-1), then the set of coordinates (x, y, z, and t*) are invariant under Lorentz Transformations. In other words, the "length" between two points in such a coordinate system is the same regardless of the inertial reference frame of the observer. Note that the common-sense observation that a length sqrt((x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2) is the same for all observers is false.

While special relativity is considered incontrovertible, there is, I think, a very clear difference between space and time, which is one of the greatest unanswered questions in science or philosophy. We cannot help but admit that the "coordinate" time flows forward in our consciousness, and we certainly don't have the freedom to move around in time as we do in space. From a mathematical point of view we can treat particles as functions defined by a few differential equations in 4 variables, and we can consider these 4 variables as equivalent, independent parameters. Particles (or more fundamentally quantum fields) exist over all time and all space. But in our human conscious world, which cannot be denied, the future has not been seen, the past cannot be returned to, and we are carried through time like a leaf in a stream is carried through space. And thus physics is philosophically at odds with everyday experience.