Imagine a day, let’s say July 15th 2079, when CERN has resulted in major findings and we have the clockwork of space, time and the universe all figured out to the extent that we can time travel.
Now imagine on this day, we decide that a worldwide experiment is to be held. Since sending someone back to the past can alter the entire future, everyone on the planet is allowed to send a message to their past selves, a 1 minute video in which they can say anything. These videos are then sent back 20 years in time with a messenger and distributed to those who exist at that point in time.
Thought one: What would you say to a past self, knowing that what you say might alter your future course, and would the present self read it?
Thought two: What would happen? How will it unfold?
Some simple theories are;
Everything. As soon as the videos are sent, the person who sent them will no longer exist. The mare act of time travel will alter your choices and the course of the world that made the future you.
Almost Nothing. Assuming that things have a predetermined course, time travel might alter certain details of random events and choices, but since our personalities and our ability for choices are limited, the future you may not experience much change at all, except for minor details not nearly significant enough to alter the course of your life.
Nothing (with a modification). Now let’s assume this theory, or at least a fraction of it. The past self will receive the message but a future self won’t see any change because the act of time travel has created alternative time lines in which the world that has already been will continue, but an alternate world in which the messages have altered the future will also exist.
What more scenarios can you think of?