Board Thread:False Info and Speculative Discussion/@comment-25230571-20150731101948/@comment-26601629-20150817201532

Not when the book already tells you. What does change only things you've already change mean, from what I gather, it means its safe. if it's safe, Time turners would not be considered an extremely dangerous item.

It's quite straightforward in a not-so-straightforward way really. Its like you said, bad things happen if you see your past self, you can for example warn yourself of something, and the present you can avoid that an then you have no reason to go back in time. That is not a loop. This shows that the time-turner isn't a stable time loops thing.

what you mention is akin to the novikov self consistency principle, while J.K rowlings used this, along with generally avoiding past self to avoid time paradoxes, by mentioning how dangerous the time turner is, and even given an example of a witch who was able to meet herself and kill herself, states that this principle is not active. Even on pottermore(which J.K.Rowlings says is canon), a timeturner has been used to cause unbirth of the user., That right there kills the only do what you have done