The 'oops' syndrome
One of the things that always confused me, when thinking about time travel is why would we ever want to send anything to the past that already exists in history. The problem might be that we just confuse the term creating and sending. We cannot not create the prophecies of Nostradamus as they already exist, but we could freely re-send them anywhere we want.
Imagine we find out that we can send messages to the past; we develop a theory and design the technology needed and build a 'rough' prototype broadcasting device so we can start sending. To begin with, we will do a small 'hop' going back no more than 50 years and send the message to Montreal in Canada and lets see what happens...
They speak French over there, so we decide to just re-send all the prophecies of Nostradamus, which should not cause any collateral damage. The idea behind this experiment is that even if any Canadian prophet claims to have received the prophecies from an occult source he will be immediately smacked around the head with the original book. Besides, sending these prophecies, that nobody really understands, would not reveal anything new, avoiding any undesired results.
We do the calculation on how and where to send the message, which might be rather tricky and complicated as the universe, the planets, the sun and the earth do not stand still, everything travels in the space-time continuum and the earth revolves around itself. Therefore the location of the earth 50 years ago is not the same as it is now. Anyway, we solve the problem as good as we can and there we go.... a simple press on a button and.....
The prophecies of Nostradamus are on their way to the past
But 'oops' something seems to have gone wrong:
The calculation was wrong, the message did not go to Canada but to Salon, France and it did not arrive in 1955 but unfortunately it arrived much earlier and well in 1555 to be picked up by a doctor called Michel de Nostradame......
Do I have to say more --- , By re-sending the verses of Nostradamus and by making a simple calculation mistake, a future time travel experiment could actually cause the creation of the original document.
Thinking this way the future could indeed be related to the past, voluntary or involuntary. Of course it will complicate reality, as we know it, as we can't say who initially invented or created the quatrains. Nostradamus might point at the occult source and the future time travel scientists might point at Nostradamus. But in the big picture they both might play an equally important role.