Part 2

_However, those in favor of time-travel have answers ready and waiting. These optimists (?) use the parallel universe theory to meet the first question. Such return, they claim, would immediately cause a forking of the Earthways, leaving our version of the world untrodden by time-traveling feet. As to the clincher, they counter-question with a How do we know we haven't had such visitors? Time-travel, when it comes, will come in a far-distant future. At such a distance the mere six thousand years of recorded human history is a mere fly-speck on the annals of Earth. So why should this tiny dot in the continuum have been favored?_