The Illusion of Time
Is there really a distinction between the past, present, and future or could it all be in the mind.
The ideas discussed here may challenge your intuition at face value but bear with me and suspend your disbelief for the duration of the article to experience full immersion.
As an undergraduate, one of the most compelling classes I took was called Einstein, Space and Time. This seminar-style class exposed me to some of the most counter-intuitive concepts of modern physics. Perhaps, the idea that challenged my understanding the most was this notion that the flow of time may be an illusion. I almost cringed when I saw a quote by Einstein endorsing, what seemed to me at the time, the most bizarre implication from the block-universe.
When you hear of time, you often think of this intangible concept advancing single-fold into the future. The notion that time keeps passing outside of our control is almost self-evident with the circular motion of the moon around the earth, and the earth around the sun.
The tools with which we measure time has become so sophisticated and duration is now recorded with such precision that one can hardly doubt the reality that time is constantly advancing. Yet beyond our universe, the concept of time doesn’t exist since time is inextricably linked to space and none can exist without the other.
Time is not a Fundamental Feature of Reality
But is time really this arrow we have come to associate causation with or is it all a subjective process in the mind? The arguments in support of a non-fundamental concept of time also maintains the position that causation itself is a subjective perspective inherent in our temporal agency.
What if I told you that the differentiation between past, present, and future is simply our minds playing tricks on us or perhaps our mind trying to impose its limitations on time. The concept of time flowing from past to future simply doesn’t exist according to the block-universe.
For the currently accepted concept of time flow to exist, space and time would have to be independent fundamental structures. In this case, events can be pinpointed in various locations in space and we could say those things happened over time. But according to the special theory of relativity, this idea of independent space and time is abandoned for a much more cohesive interdependent spacetime.
One of the major consequences from this seemingly counter-intuitive 4-dimensional structure is that nothing changes over time since the past, present, and future are already accounted for in the block-universe. This four dimensional conception of reality highlights all events across spacetime with the same import. In this system, the past is no more important than the present is from the future.
This insight renders time effectively as one of the required coordinates to specify an object’s location in spacetime. From this new framework, an event in spacetime is already comprised of both time and place — and the whole fabric of spacetime can be understood as a collection of infinite number of events. Simply put, both the past and the future are all coexisting within spacetime. Another alternative idea that has often been entertained is that, perhaps, spacetime is not fundamental and thus emerges from some lower structure. Of course, such an idea would have to overlook the implications of the block-universe.
Time does not flow — just as space does not flow— time simply is. Imagine traveling from California to Florida, you do not say that Florida doesn’t exist because you are not there yet. You know that Florida is a location in spacetime whether you are there or not. The same idea can be applied to time where the past and future are also there whether you have access to them or not. So the future is not going to happened, it is already there.
In physics, this concept can be understood using the Minkowski spacetime diagram. Physicists employ worldlines to represent a point in space using a line in spacetime. This idea takes advantage of cones to simplify the visualization. A present event on this spacetime is shown as the base of a cone which resulted from the contraction (at the speed of light) of the radius of a circle (or sphere in a 3-D space). The entire history of this particular worldline in spacetime can be translated into an expanding and contracting cross-sectional 3-D spheres in space resulting in a 4-D light cone. These events are viewed as the intersection of light with spatial planes. The figure below shows light cones in 2-D space coupled with time.
Einstein, himself, in a letter to the family of his longtime friend Michelle Besso, expressed his doubt about the distinction between past, present, and future:
Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.
Mind you, time itself, is not what is in question here but rather the passage or flow of time. Einstein’s curiosity about simultaneity and his quest to resolve inconsistencies between Maxwell’s constancy of the speed of light and Newton’s absolute space and time, to a great extent, compelled the theory of relativity.
Einstein’s conception of the universe, however, is somewhat lacking a clear definition of duration as Julian Barbour brings up in his What is Time interview with the prolific writer and producer Robert Lawrence Kuhn on Youtube. Einstein, however, was able to make the distinction between time used to record historical data and time used in keeping track of duration.
He even exploited and figured out exactly how the two are related to each other as Prof. Sean Carroll of Caltech alludes to in an interview with Robert Lawrence entitled, Is Time Real?. The takeaway here is that, the block-universe representation, which Herman Minkowski so masterfully constructed using the framework of Relativity, renders the distinction superfluous. Namely, we do not need the flow of time to make sense of reality.
One of the current subtle misconceptions is that change is a manifestation of time but if you really think about it, is it not just as logical to infer that time may be our conception of change. If this is the case, then change is a tangible occurrence of reality rather than time. But how could there be change without the passage of time, you may ask? This would be a relevant concern. We are able to recognize changes because of the information recorded in our memory about the past which give rise to the idea that time passes.
Everything we have considered up to this point has been at a Relativistic scale. What do you suppose is the nature of time when we shrink to the sub-atomic scale?
Quantum Mechanical View of Time
One can make the case that the quantization of certain aspects of the universe would imply discrete time at the quantum level. Yet not every facet of the universe is quantized as various experimental undertakings, using pulsating laser beams, have shown. Consequently, any hope of a continuous time lies either at the scale of Planck time (10^-43 seconds) or in the convergence of quantum mechanics and general relativity in a theory entitled quantum gravity.
For all we know, there could also be parallel multiverse with deterministic wave functions that can be evolved backwards and forward giving way to an arrow of time. Nonetheless, since there is no convincing way to obtain definitive proof about the existence of these multiverse, this explanation remains in the foreground.
Prof. Carroll makes some interesting conclusions at the end of his interview with Robert — that our most accurate model of reality namely quantum mechanics includes a notion of time so therefore it is not an illusion or a figment of our imagination. It becomes abundantly clear though that our conception of the past and future is incomplete — that is to say we do not yet have a complete understanding of time.
One of the main reasons for this incongruence between the arrow of time resulting from quantum mechanics and the lack thereof in the block-universe of relativity could very well be due to the second law of thermodynamics. The total entropy of the universe tends to increase and this disorder may be responsible for the apparent puzzling nature of time.
The laws of physics, as Prof. Carroll emphasizes, do not see the differences between the past and future. At the moment, we can embrace the fine-tuning assurance that, the configuration of this particular universe makes way for an arrow of time. It highly probable that when we finally resolve current problems within our understanding of the universe, it is likely that time will be one of the remaining components required to understand reality.
If in any case time is done away with, we can still rejoice in knowing that our collective understanding of physics and the universe as a whole will be more refined — so in either case, humanity wins.
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