Kind of a hard question to ask. In our universe we observe preservation of matter. At time t0 my mug may be at coordinates x1, y1, z1 and at time t1 it may be at x2, y2, z2. At both t0 and t1, the universe contains the same amount of matter even though the mug is at a different place, and we say that matter is conserved. From a 4D perspective though it seems that i may move my mug forward in time a whole century, and even though the current universe will have less matter than it had before my mug time traveled, 100 years later, that will be made up by the universe having more matter (my mug is back in business). Suppose the matter in our 4D universe (time being 4th d) is some amount M and is distributed throughout the time coordinate (as well as the others). Then, even after i move my mug from time coordinate to time coordinate, the universe will still have same amount of mass M, so tomorrow the whole earth might have vanished and it wouldn't necessarily go against preservation of matter (it might show up at some other time t). Of course observations don't seem to imply this, what do you think?