Across the Harry Potter series, there a few prophecies we see play out, most obviously, the prophecy made by Sybil Trelawney about Lord Voldemort, which essentially leads to the entire series of events.
However, Lord Voldemort was only able to act on the prophecy, and attempt to stop it coming true, because he knew that it existed (although he missed parts of it, which ultimately led to his downfall).
Harry also found out about the prophecy, and was therefore able to use that to his advantage, and make sure it played out correctly.
But, do you think this prophecy, and any others in general, would still eventually come true, regardless of whether or not someone had acted on them? If no one had ever heard a prophecy be made, would the events it spoke of still always happen? Or are some prophecies dependent on others knowing of their existence?