If we consider the Universe to be a single, unbroken chain of cause and effect, and time is just our perception of that sequence as we move forward along the chain, then there’s no need to worry.
By this interpretation, the past, present and future must all be fixed by the immutable laws of physics.
Even seemingly random events, such as radioactive decay, would be predetermined and must play out in exactly the same way, even though we can’t predict them.
If you travel back in time to meet your younger self, it must follow that this has already happened in your past.
If you don’t remember it, then maybe you were in disguise or you wiped your memory afterwards, but whatever effect this had on the future is already locked in.
Conversely, if you travel forward in time and meet yourself in the future, it follows that you must return to your point of origin and carry on with your life, or else there would be no one there in the future for you to meet.
This means that the version of you that you meet when you travel forward, already remembers the encounter from when they were the time traveller.
Alternatively, if every act of causation creates a parallel universe in an endlessly branching tree of possible timelines, then every version of reality already exists somewhere, and it probably doesn’t matter what you do.
Luckily, time travel is purely theoretical and all of the proposed mechanisms involve exotic matter or negative energy for them to work at a macroscopic scale.
This just explains one impossible idea by invoking another. The only kind of time travel we know of involves moving forward at the rate of one second per second.
This article is an answer to the question (asked by Andrew Robbins, via email) 'If time travel were possible, should you really avoid contacting yourself?'
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