Hello @funnytale, this text has been found in a couple places around the web, and because you have no attributed it to anyone you're plagiarizing it.

http://abyss.uoregon.edu/~js/glossary/grandfather_paradox.html
http://www.thehelper.net/threads/time-travel-paradox.80486/

Because a previous post of yours is also plagiarism, and you've been around long enough to know better, any further plagiarism will earn a place on cheetah which will automatically downvote future posts. Please take this warning.