Eternalism, says Sean Carroll in his lectures on time, is the notion that a scientist, or at least a physicist, has a "view from nowhen" inasmuch as past and future are viewed with a kind of indifference. This indifference consists of the ability to see that, for any particular particle moving in one direction at a certain speed, it can be conceived of as moving in the opposite direction at same speed. Since every change involves an interaction of equal and opposed forces, the same process can be reversed while operating according to the same laws of nature. Consequently, the processes that we witness in our daily life could, in principle, occur in reverse. One would need a closed system for that to happen, so it makes more sense to say that all of the processes in the universe could together go in an order that is the reverse of what we now see happening. And in doing so, they would proceed in a manner consistent with the laws of nature. Of course, t...