I went out for a curry with some fine gents this evening, and I was asked a question on whether I believe in the possibility of time travel. Normally, the go-to response would be that rules around a paradox would prevent it - anything that is changed in the past would have an effect on the present, which could have an effect on circumstances leading up to the decision to go back in time to do the very thing that has been done. To put more simply, imagine building a time machine with the sole intention to kill Hitler. Said machine is built, and you go back in time, and you complete the task.
In this new timeline however, Hitler did not achieve the objectives that led to the determination to travel back in time and assassinate him, and because of that inaction, the changes that were previously made are undone, but at that very point there is a situation where time is in both states - effectively a deadlock - with our understanding of spacetime, we cannot surmise a way that it would resolve successfully. Hence, if going back in time was possible, it would be like rewinding a video - completely immutable. After all, our perception of events are purely a reaction from our senses, and to relive a time specifically would mean we would need to move a distance faster than the energy source which contains the information that our brains perceive. So, in reality, time travel would only be possible if the traveller were to travel a distance of a light year for every year they want to observe, and once they have achieved that distance, they would need to have a sufficiently powerful device with enough resolution (and zoom) to be able to observe for a distance; however even then, they would not get the same kind of resolution that they would be wanting to achieve as they do on TV shows. To make matters more complicated, one would have to travel in all directions outward from the earth to be able to maximise the collection of all information coming from the earth. This would in theory create a sphere around the earth with a radius of 2.32737852e+18 miles for the ability to view 100 years ago.
So, what about the possibility of seeing the future? That too could be answered off the above, however from the other side - the events have not happened, and as such there is nothing to observe. However, there are a few things to take into consideration:
- Time is a construct we have developed to measure fundamental progress (At it’s basic level, atomic decay)
- Quantum theory and entanglement may be seen as a possibility that everything has already been predetermined, happened and not happened at the same time
- Quantum Observer Effect would not guarantee that if possible to see the future, that it would be the future that will happen
So the second and third point may seem to contradict each other, and, just like theory itself, it both does and doesn’t. If you were able to observe something from a quantum level that was not it’s predetermined time, then that would alter the current environment. To put it another way, if you were to observe an energy state that was not due at the present time, then the observation of the energy would alter it, be it draw-down the energy state to a lower level, or the observation of the energy state, say, in the form of a pattern, at the wrong time would mean that the pattern would be different at the time that it was supposed to be observed.
It’s a complicated subject, and is very much like a rabbit-hole. You can keep going deeper, and find yourself going around in circles.