Imagine you send a warning to your past self about an upcoming issue. Your past self gets the message, avoids the problem, and all is well. But here’s the tricky part: if the problem was avoided because of the warning, then your future self wouldn’t have needed to send the warning in the first place. It’s a loop that doesn’t seem to make sense.
The way some explain this is through the idea of multiple universes, or the “Many-Worlds” theory. According to this, every decision we make creates a new universe. When you send the warning, you might be sending it to a version of yourself in a different universe, not the “you” in this universe.
If the warning only reaches “you” in another universe, then did “you” in this universe really change anything, or benefit from that exchange? In this scenario, you’re essentially helping an alternate version of yourself avoid the problem, but the “you” in the universe where the problem occurred still has to deal with it.