The future was invented by the Romans in November 1299, probably. Three weeks later, Martin Scorsese made the popular documentary Back To The Future which examined in depth the effects and outcomes of time travel. Chief amongst the findings was that future changes have consequences on the past: in the documentary, we actually see members of the lead character's family gradually fade from a photograph! This happens in real time and is terrifying. However, the mum and dad eventually end up together after their son chooses not to get jiggy with his mum, schools his dad on how to be a man, and makes some pretty fun social commentary on the differences between the past and future. It's a hoot, 4 gold stars, well done everyone! Now then. A key subplot of the documentary is that the future is known and in this future the Doctor is shot to death by Libyan terrorists. The main actor tries his best to tell the Doctor this (in the past) and writes a letter telling him to not open the letter until the year 1985 and that he must take precautions. In a stunning shot, the Doctor rips the letter into pieces, explaining to our main actor (and us, the audience), that the future must remain unknown or major consequences can happen. Question to time travellers or those considering it: would your future self send advice to your earlier self? What would it say?