Walter J. Sheldon, Your Time is Up
“ If you go into the future—or talk to the future—the future affects the change, through you. In other words, if you can't go back into the past, neither can people from the future. And it's inconceivable that such a thing wouldn't make changes. Maybe only small ones, but they'd multiply in time. 'Thou canst not change a flower, without troubling of a star.' That's Francis Thompson. You step on one spider today, and you affect the evolution of spiders, the ecology of all other things in the distant future. By a simple act like that you could destroy or create a whole species to come. ”
