Faces in Time by Lewis E. Aleman Page A

versions of herself would exist at the same time. If she wanted, she could watch her past self’s life unfold year after year. This would add the existence of the time traveler to the mass of the universe at that point in time. There would be two of her when there used to be one.
    Just like the dynamite from the future, the time traveler exists independently of her past self. The time traveler’s origin lies in a future that has been erased, not a past that is now altered by the time traveler being there. Her existence makes perfect sense relative to herself or anyone else traveling with her. Since she travels alone, her existence makes no logical sense to the rest of the universe unless someone else is genius enough to deduce from when she has come.
    Chester loves Doc Brown, but Doc was wrong on this one. A photograph brought back to the past would never change regardless of what happens from that point on. And, neither would the time traveler fade away from changes made from that point on. In the instant that one arrives in a new state of time, one becomes part of that existence and not dependent on the time one came from. Theoretically, as soon as that person enters in the past, by being there, the person has already changed the future that he came from, erasing the future that he knew.
    There is no ever coming home again.
    Any point in time—the past, the present, or the future—is  never any more than the sum total of all events leading up to it. What one is today, what one owns, how one feels, where one lives, and what one has accomplished is all a result of the sum total e actions surrounding one’s life—all of the things that one has ever done and the things that people have done that have affected one. One’s sum total at forty years old would obviously be different if one was killed by a neighbor in early childhood, not even being allowed to reach age forty, or conversely if one won the lottery at age twenty.
    But, even smaller events change the sum total that makes up our reality at any point in time. Eating, breathing, interacting, walking, talking to people: all of these things change the current environment, which alters the future—they are all new events to be added to the sum total that we consider the present or the future. From the instant the time traveler exists in the past, her existence must be added to the sum total of events making up a new and changed past. The sum total for the future will never be exactly the same because the time traveler’s existence has been added to its sum total; the precise future that the time traveler has left will never exist again.
    Because of this, one can’t exist in the past for even a moment without erasing the exact future from which one came.
    If a time traveler goes back in time one year, she could show up at her home and visit herself. If she stays with herself for an entire year, spending every day with her, she’ll be back at the same date and time that she left—her original present, her time traveling point of origin, the future that she left. At this point in time, she’ll still be there as will her past self that she has been spending time with every day. No magic force is going to make either body disappear when the year has passed. There will still be two of them.
    Time travel inherently breaks the law of conservation of mass/matter. Whatever goes back in time has an origin that has been erased from existence. Therefore, there is no paradox to worry about. Independent mass has been added to the universe.
    So, a time traveler can never travel back in time and then return to the future that she left and have it remain the same. The most notable difference will be that the time traveler will find her past self there too, grown up and possibly living a very similar life to what the time traveler was living before she went back in time. And if her past self never decides to go back in time, there is also no magic force that will make the time