Hmmm... I still don't understand; If someone went back and killed Marx's grandparents, Marx's contemporaries wouldn't suddenly see him "fade into the ether." He just simply would never have existed for them. And we here in the 21st century wouldn't be aware that anything amiss had happened either. In fact, couldn't time travelers be traveling backward in time constantly killing people whose offspring they don't like -- thereby instantly wiping out our memories of those people and anything they might have accomplished during their lifetimes?I just wish they'd get around to Stalin, Mao and Hitler! Just to be fair, they did kill Zarquon, Lifnerd, and Bullawayo -- and they were far worse.