At the very end of Christopher Nolan’s “Interstellar”, it is suggested that the reason why Cooper is able to survive falling into a black hole is because “humans from a different time” enabled Cooper to reach the tasseract and thus change his timeline. I remember being in the theatre when the movie came out and the audience’s brains being fried by the concept. The reaction is caused primarly by the fact that the human brain for millenia processed time as a propelling force that only moves in one direction, but modern physics has taught us how time is a dimension, just like depth, height and so on.

The movie however posits an interesting though experiment because we as the audience get to experience the timeline of the story from a fourth dimensional perspective. Even though the future humans (IE the humans from Anne Hathaway’s planet in the timeline in which the gravity equation wasn’t solved and all of earth’s died) were able to eventually change time by saving Cooper from the black hole and enabling him to communicate his discoveries to his daughter, we as the audience get to see both timelines before they converge and the universe rearranges.

Essentially, if time were to change, the universe would as well, leaving no trace that a change ever happened (this is all theoretical of course). In a similar way, if we had a cube, and we chopped off it’s top smoothly, we would have a tetrahedron. Looking at the tetrahedron however, we would have no way of knowing whether it used to be a cube or it was always a tetrahedron. That’s why altering our timeline would just rewrite everything and yet we would not even notice. However, what happens if the rearrangement is not smooth.

Stephen Hawkins posits time travel to be theoretically impossible because of “the grandfather paradox” which essentialy argues that it’s impossible to resolve a scenario in which one would travel back in time and kills their own grandfather because that would prevent them from being born and thus from ever becoming the killer. On the other hand, Interstellar argues that in the distant future we may be able to discover ways of carefully traveling back in time without causing paradoxes.

I will examine how the existence of paradoxes implies time’s existence not just as a dimension, but also in the more traditional “narrative flow of existence” way.

In Interstellar, the implication of Cooper’s success at saving Earth’s humanity is that the future people that saved him in the first place will be joined by Earth’s people eventually. Essentially they avoided the paradox because they are literally a wormhole away, so saving Earth’s humanity will not impact their timeline until humanity can travel interstellarly, and the hope is that interstellar travel will only be achieved by Earth’s humanity AFTER humanity’s on Anne Hathaway’s planet accomplishes the time altering task. But what if a paradox were arose instead? What would have happened to Cooper?

Some argue that the universe would implode because it’s not able to move forward in time. Essentially the paradox “freezes” the universe. Even that scenario though, Cooper’s mind would at the very least remember what the timeline looked like before the time travel, at least from his perspective. The audience however, has a fourth dimensional perspective, where we get to simultaneously observe reality from both timelines because our memory traces the universe changing from one timeline to another. If we were the observer’s of the paradox, regardless of whether it gets resolved or not, we would still know that a change happened because we are separate from the universe.

Going back to the cube and tetrahedron example, any point inside the geometric shape is no able to notice the change because their coordinates relative to the space they exist in change, and with that change their identity changes as well. But a point separate from the shape on the graph, would remain essentially unaltered by the transformation, and thus could retain the knowledge of the cubic form of the shape before it turned into a tetrahedron. This kind of 4th dimensional perspective I am going to call the “God” perspective, because theologically speaking any notion of the deity across cultures and understandings as always lied beyond the empirical universe.

In a way, timeline manipulation is just a modern version of the eternal phylosophical question of “if a tree falls and no one is there to hear it, did it make a sound?”. After all, if no one is there to notice that the universe’s timeline was altered, how can we even argue it was changed at all? Indeed paradoxes of this kind are weird: very weird. In the context of Interstellar however, whether humanity is able to remember or not, it did happen!

This is where Michio Kaku’s “bubble theory” comes in handy. He essentially argues that there are multiple universes where the fundamental constants in physics & math (such as the speed of light, the value of pi) are different. He posits that it’s possible for the universes, which are constantly expanding, to bump into each other at times. This implies that theoretically there is a “container” of these multiples universes, thus if a sentitent being was in the container but not into any one universe, such being could observe the universes changing as a result of a timeline manipulation. For such being, time would simultanously be a dimension it can observe in the universes, but also “narrative flow of existence” that remains unaltered by a timeline manipulation.

Time as we understand may be totally incorrect in terms of physics, but it may hint at the possiblity of time’s dual nature. After all, if light can simulatnously behave as a particle and as a wave, couldn’t time simultanously behave as a eternal force and as a minipulatible dimension?