In this post, I will consider some of the objective and subjective elements of time, including some requirements, and how they relate to temporal experiences. I think that it’s safe to say that time involves both a mental and physical component which is evident when we recognize the lack of consistency between our subjective or mental experience of time relative to an external objective standard (i.e. “clock time”). It is this objective standard that most people call “time”, although there are quite a few people that consider the subjective experience of time to be the only “time” there is. Some believe that time is an illusion, that is, that time itself or the arrow of time that we experience is nothing more than an experience and doesn’t exist outside of consciousness or otherwise. I’d rather simply focus on what we experience and how it appears to relate to the physical universe. For the purposes of this post, we can assume that time exists in some objective way and we are able to experience it in a subjective way.
Time is often thought of as a dimension and I think that it’s reasonable to consider time to be a dimension as long as there is an appropriate relationship between said time and the existing physical spatial dimensions, for without this relationship, I can’t see any foundation to build off of such that we can justify time as being a dimension per se. One theory that demonstrates this type of relationship is well-established within the field of physics, namely Einstein’s Theory of Relativity. I plan to discuss this theory of time and space as well as some of its implications. I find it interesting due in part to the paradoxical temporal phenomena it manifests as well as its unique relationship with 3D-space. I think that this theory also demonstrates that time travel to the future is possible if enough energy is available. I also plan to discuss time travel and what I believe its limitations are in order to satisfy some laws of physics. All of these various elements are relevant to a temporal experience and, needless to say, time in general. I decided to separate this post into three parts:
1) Temporal Experience & Memory
2) Temporal Experience & Space-time
3) Time Travel and its Limitations
Keep in mind that these posts are just some of my recent thoughts on time based on what I’ve read as well as my own two cents on the matter. Anyways, here begins part 1 of this essay.
Requirements for temporal experience
I think that the most important mental requirement for a temporal experience is memory (storage and retrieval). I think that memory provides a mental frame of reference, which seems to be necessary in order to have some concept of the past, present, as well as a concept of the future (albeit through inferences made from the past). In addition to a mental frame of reference, I also think that a physical frame of reference is necessary for a temporal experience since “clock time” or “proper time“, which appears to govern the speed of all processes (including mental processes), is dependent on this reference frame. It is these physical and mental frames of reference that allow time to exist both objectively and subjectively. Together these two frames of reference appear to be what mediates a temporal experience.
Mental frame of reference
If an entity had no memory, I don’t think it could have any experience of time because there would be no way to relate one moment of thought, sensation, perception, etc., to a previous moment, that is, there would be no “mental relativity”. It is memory that serves as a mental frame of reference from each moment of time to the next, thus allowing a sense of causality or change, that is, a sense of time. Can a temporal experience occur with out a sense of change? I don’t think it can, but if I hear a compelling argument that suggests otherwise, I may reconsider. As for how much memory is required, I don’t think that there is any minimum amount of memory needed, so any arbitrary amount should suffice. After all, some insects may only have a 30 second memory span (or less), but I see no reason to believe that even with a memory span as short as this (or shorter) that the insect is incapable of any kind of temporal experience at all. Thus, it seems reasonable to believe that there should be no minimum amount of memory required for this experience, as long as there is at least some memory.
If memory is truly required for a temporal experience, then it should be clear that different temporal experiences can result from storing, retrieving, or processing those memories in various ways as well as increasing the amount (or type) of memory that an entity possesses. For simplicity, I will limit my use of the term “memory” to that which is present in brain-utilizing living organisms (as opposed to that of A.I.).
Memory storage, retrieval, and processing
If memory is stored and/or retrieved differently (e.g. method used, rate, etc.), it may lead to the experience of time passing by or having passed by at different rates. I think that this subjective temporal “rate” is another important feature of the mental frame of reference that memory seems to produce, and I also think that this temporal rate is at least partially a function of change in some kind of a temporal baseline over time. I’ll explain more about this theory in the points that follow.
Psycho-pharmacological substance-induced or otherwise caused physiological changes to a brain could very well be associated with a change in this “mental relativity” or “temporal baseline” and thus could produce a far from normal temporal experience. When I use the term “normal” to describe a temporal experience, I am defining it to be the feeling of time passing by at a normal rate, that is, there is not a significant change made to the previously established temporal baseline (which I’ll explain shortly). I want to point out that while someone may feel that time isn’t passing by at the same rate that it once did years ago, I want to distinguish any short-term temporal rate changes from the long-term temporal rate changes. For now I also want to focus on the idea of a temporal baseline and how it relates to short-term, or working, memory.
I believe that we establish this temporal “baseline” (i.e. “mental clock”) over time based on our duration of physiological constancy (and most importantly the memory or record of it), and thus is more easily defined when physiological changes are relatively small for extended periods of time. One could analogize a well defined temporal baseline as a mental clock that has been synchronized such that the temporal experience feels normal. When the physiology of memory and other brain processes are changing less over time, this rate of resynchronization slows down until it approaches a state of synchronicity (a point in time after the absolute-value derivative of physiological change falls below some threshold similar to the “Just Noticeable Difference” or JND). To illustrate this idea, let’s assume that the following graph represents a physiological change over some interval of time.
As you can see in the graph above, a physiological change is shown over a time interval of one second. I omitted labeling the y-axis with any metrics or units since physiological changes can be quantified in numerous ways. If one were so inclined, the concentrations of certain chemicals in the brain or the speed of certain mental faculties could be measured and used as a quantifiable metric. Regardless of the units or metrics used, the idea here is that a physiological change in the brain starts to occur at some rate (which may be seen as the start of a temporal incoherency or baseline shift), gradually increasing to a maximum rate (when t = 0.5 in the graph above) and finally slowing down until the new physiological state is established (coinciding with a temporal baseline re-synchronization). My theory is that as the rate of physiological change starts to decrease, the temporal baseline starts to re-synchronize. Even though the physiological state is not what it used to be, as long as the amount of change is decreasing, the new physiological state will eventually feel “normal” as the previous state did.
So we could say that during the time interval where the absolute-value derivative of the physiological change curve is above some “Just Noticeable Difference” (JND) threshold, we experience an abnormal temporal rate and vice versa. The derivative of this curve, f ‘(x), might look something like what is displayed in the graph below.
We could say that a y-value of zero (on the graph above) defines a perfectly synchronized baseline. Either way, when the absolute-value derivative of the baseline synchronization is some value below the JND threshold, we start to have a feeling of normalcy. Once we have a well defined baseline, we should be able to say that as one minute of time passes by on a clock, that we also feel approximately one minute of time passing by. During a physiological change to memory however (where the absolute-value derivative is above this JND threshold), one minute of time passing by on a clock could feel as long as many minutes or hours. This leads me to believe that memory transcends physical time in at least two ways:
1) A temporal experience provided by memory is not fixed as the physical or objective passage of time is (i.e. “clock time”), that is, an entity’s temporal baseline is always changing (resynchronizing after a physiological change to memory occurs in order to return the temporal experience to a state of “normality”) which means that we don’t experience time elapsing at a constant rate, even if it is a constant rate according to a physical clock.
2) Memory can store certain aspects of an event such that they are accessible in the future whereas physical time passes such that certain aspects of “the present” are eventually and inevitably inaccessible as “the past”.
I think that number one (listed above) seems reasonable based on our experience. If you’ve ever ingested a mind-altering drug (e.g. caffeine, nicotine, alcohol, pharmaceuticals, THC, psilocybin/psilocin, etc.) or felt extremely tired or hungry, you may remember how time did not pass by in a normal fashion. Stimulants have been known to increase our estimation of time intervals (i.e. increase our subjective temporal rate), whereas depressants have the opposite effect. It has even been shown that by simply increasing the temperature of our brain (even unintentionally with a fever), that we tend to over-estimate the rate of time elapse, presumably due to the fact that the speed of all chemical reactions remain proportional to temperature. However, if one was in a particular physiological state for a long enough time, it may start to feel increasingly normal. If one returns to a previous physiological state (e.g. after the drug wore off, after sleeping, after eating, etc.), more than likely time passed by in an abnormal fashion once again until you adjusted to that new physiological state (re-synchronized your temporal baseline).
I should note that for number two (listed above), in theory, we may have some access to the past by inferring it based on reversing the deterministic causal chain we are aware of. However, we are only aware of a limited portion of that causal chain and memory provides the possibility to instantly retrieve aspects of the past which are otherwise not easily (if at all) accessible to us. On top of this, the implied randomness that exists within the quantum realm suggests that we can’t predict a reversed causal chain beyond some level of determinism.
Matters become even more complicated when we take into account the fact that our bodies are trying to restore some sense of equilibrium and respond to physiological changes in the brain by taking chemical compensatory measures. The important point here is that if one is in a new physiological state that is not changing much (i.e. minimum compensatory measures taken by the body, intake versus metabolism of a chemical/drug is nearly constant, etc.), we can start to feel normal, even if our new state is not the physiological state that we previously identified as “normal”.
While our temporal experience may vary due to physiological changes, physical and mental (i.e. subjective) elements of time are definitely correlated with one another. If you double the rate of physical time elapsing (i.e. “clock time”), it should also double the subjective duration of the temporal experience, even if that subjective duration (which I believe may be mediated by some temporal baseline) can never be quantified or measured. For example, if a human brain produces a temporal experience that feels like one hour but in actuality only one minute of “clock time” has elapsed (based on the entity’s temporal baseline), then two minutes of elapsed “clock time” should be correlated with a temporal experience that feels like two hours (assuming the baseline hasn’t changed significantly during this time). While this may seem obvious, I think it’s important to note this correlation.
Amount of memory
Increasing the amount of memory an entity possesses, that is, by increasing the range between the earliest accessible memory and the most recent and/or increasing the amount of information stored within that range should also be correlated with a unique temporal experience. If we compare humans that have lived for different lengths of time, we can see how the amount of long term memory acquired suggests that they are having different long term temporal experiences.
The number of long term memories would vary from individual to individual, and it would seem that by living longer, one would also increase the range between the earliest accessible memory and the most recent. I would expect this to be associated with differences in their temporal experiences.
For a 100 year old individual, one year passing by would only be another 1% of the total objective time experienced, where in the case of a 1 year old infant, one year passing by would be another 100%, or an effective doubling, of the total objective time experienced. In other words, as we age, each day that passes by becomes a smaller and smaller percentage of the total number of experiences. This suggests to me that subjective time probably passes by more slowly when there have been a smaller number of memories accrued and vice versa. I’ve heard many times before that as you age, time flies by, and I think that this is at least one factor involved. For those that have doubts about subjective time passing by at different rates as you age, try to think back to when you were a child and you thought that it would take “forever” to turn 18 years old. Once you became an adult however, more than likely your experience of time began to speed up a little.
There are certainly other factors involved with this age-related change in subjective temporal rate. For example, in the case of humans there seems to be a decrease in the amount of day-to-day change as we age due to the routines that we start to follow as well as the decrease in exposure to new information and novel experiences, thus making one day harder to distinguish from another. If this is true then memories may somehow begin to “blend” together or compress into a representative albeit truncated temporal chunk, or it could also be the case that less memories are stored altogether due to the lack of novelty within the redundant experiences. If a novel experience somehow tags an event such that it is remembered better, this may be analogous to looking at our mental clock more frequently (e.g. t = 1, t = 2, t = 3, t = 4, t = 5, etc.). When an experience is redundant, there is little or no tagging involved and this is analogous to infrequently looking at our mental clock (e.g. t = 1, t = 5, etc.). This would mean that over time our attention to time based on memories decreases.
There is also a decrease in the number of age-related goals since an adult is no longer age-restricted from drug and alcohol consumption, driving privileges, watching R-rated movies, etc. In this last example, it seems reasonable to assume (based on our experience) that when we are expecting a positive stimulus at some known time in the future (e.g. an age-related privilege, positive reinforcement, etc.), that the rate of time passing by feels reduced. On the flip side, when we are expecting an unpleasant event to occur at some known time in the future (e.g. an obligation, negative reinforcement, etc.) we may expect to feel an increase in the rate of time passing by. So how we mentally or emotionally tag events appears to affect our temporal experience as well.
Here is the link for Part II: Temporal Experience and Space-time