As a sci fi fan forever, there is only one question to ask when a character travels into the past. What happens to the present? It would seem that events created by a Hitler or his ilk, if changed, would have devastating effects on the present which sent him or her. In other words, what happens to the people who created time travel? Would that science have developed? What other powers would reign supreme; the Russians or the Japanese could have held supremacy, or an Isolationist America. There are so many pitfalls with time travel in the past that it is about as hard to speculate on as any idea. Remember "The Sound of Thunder" from Ray Bradbury. A man steps on a butterfly and the whole world changes. Anyway, this offering shows how forces at work in the cosmos prevent mere mortals from playing God.