What Is Time? A Linguistic, Physical, and Psychological Discussion

"Time is the most unknown of all unknown things."

- Aristotle, supposedly. 

How else could we start a discussion about a concept as abstract as time, without beginning with a quote from a long-dead Greek?

Table of Contents

So... Time. Time is an abstraction. To the human mind, time isn't a "thing". It's not something that we can touch, slap, wrap up and send in the post, it is only something we 'experience'. As we cannot cease to be humans with human minds, this limited perception will likely not be changing any time soon. Thus, the question, "What is Time?" is probably a misnomer as I don't believe we can truly answer What. What I think we can answer is "How is Time?".

So, let's do what we can do as primitive meat goblins, and examine how we discuss time in three domains:

  • Internal = Neuropsychiatric/Psychological
  • External = Physics
  • Shared/Communicated = Linguistics

Psychological Time

Background reading = Cartesian Dualism: The mind and body (or rather mind and brain), are separate but interacting entities. The brain is the thing, the mind is the non-physical psych and consciousness. Thanks Descartes.

Obviously, the way the brain interacts with time is going to be a complex discussion. To deal with this, when I conceptualise brain-time, I reduce it down to three systems (though in reality they are more one big multi-faceted interacting goo-pile)

  • The Pineal/Circadian System: "It's around 6pm/dinner time."
  • The Striatal/Chronological System: "It's been around ten minutes since we ordered."
  • The Hippocampal/Experiential: "This feels like it's taking FOREVER!"

The Pineal/Circadian System

The circadian system's centre of operations in the pineal gland in the brain. This is where external and internal cues are processed to orchestrate the general cycle and pattern of a day. If you feel hungry around a certain time or find yourself waking up at the same time naturally, you have this system to thank. The circadian system cares about biological functions and life preservation. The sun is up? better hunt and gather. Getting dark? find somewhere safe to sleep. If you find that too much blue-light screen exposure before bed makes falling asleep hard, that's your pineal gland being confused, thinking it's daytime.

The Striatal/Chronological System

The chronological system cares about lengths of linear time. Those people who are weirdly good at predicting when the microwave will be done have a good relationship with the striatum of the brain. These people can tell how long your microwave popcorn has left, because this system has been ticking over and counting seconds since they pushed start. Conversely, in the elderly population (especially those with certain dementias) this system breaks down. On the lesser end, this causes rambling anecdotes that don't seem to know how long they've dragged on for. On the moderate end, a weakened inability to estimate the passage of time. On the severe end, a complete disorientation to time.

The Hippocampal/Experiential

The last, and my favourite, is the experiential system. Ahhh the hippocampus (Latin for seahorse btw). The hippocampus is the site of new memory/learning. It cares what you're paying attention to, and little hippocampal scribes run to write it down. This system perceives time in terms of how many entries the scribes make. If there is lots of new data, it must have been a long time, if there's less, then shorter. This underpins the "Well Travelled Road" effect. This is the cognitive bias in which familiar routes are falsely perceived as shorter than unfamiliar ones. This is because the familiar is boring to the hippocampus. There is no need for the scribes to run frantically because they've seen it all before. So, less data recording, shorter perceived journey. Conversely, the fight-or-flight reflex floods your brain with exciting drama chemicals, telling your hippocampus to record as much as possible. Every little detail. This causes the phenomenon of "time standing still" or going in "slow motion" during dangerous or dramatic events. The hippocampal scribes are writing down so many recordings that the system manager perceives the event as spanning massive amounts of time.

Whilst each of these systems is arguably more evolutionarily advanced than the last, they are all susceptible to chemical interference. Caffeine tricks your circadian system into thinking it has accrued less "I wanna sleep" points than it has. A range of chemicals that alter the firing of the striatum warp time perception as faster or slower. And anything that alters the global activity state of the brain will feed the hippocampal scribes more or less to write about.

If our brains are evolutionarily determined thinking organs, then we can consider time measurement as filling three functions and answering three increasingly complex questions:

  1. Should I be eating/sleeping right now to stay alive?
  2. Should I be timing how long this has taken to increase the chances of success?
  3. Should I be paying attention or is it ok to be bored and just skip this bit?

At the end of the day the brain doesn't care about time, it just cares about results and staying alive. And as someone who is alive, I can't really complain too much about that.

Physical Time

So, external to our perception of it, what is time?

The 'Second' in Linear Time

Let's consider a microcosm, a Lab.

Note this as being the truest representation of the micro-macrocosm relationship, in which the macrocosm is the κόσμος [ cosmos = whole unified universe ]

In the lab we experience time as linear. Time flows from the before-y bit, through the infinitesimally small eye-of-the-needle we call the 'now', and into the unseen future-y bit. This arrow of time lets us know how long the microwave pizza has been in the microwave, how many years old your niece is, and how long until you go buy another coffee. We experience time as a non-spatial dimension, measuring the distance between events.

We can measure these distances. There are many units you can use, but if you're a good little physicist, you'll use one that the Système international (d'unités) likes. This is to say you will use one derived from the SI-unit, the "second". We could build up a minute from 60 of these seconds and talk in terms of minutes (the Système international should be fairly happy with that). We could group together some minutes and talk in terms of hours (French approved). This can go on ad nauseum grouping seconds into larger (or consequently smaller) groups/divisions. However, one fundamental question arises. How long is a second?

Fun fact: the name "second" comes from the historical division of the base unit of time, which back then was an "hour". A minute comes from the first division of an hour into 60 (60 because... idk blame the Persians). This division of the 'hour' was called the pars minuta prima (first minute part). The second is one of these divided the same way, aka the pars minute secunda. We now define an hour from a second not the other way around.

The historical issue of defining a second has revolved around finding something constant(-ish) and then dividing it into manageable bits. If we have a constant, relatable, unit of time we can use that as our reference. We could use any reference if it was constant enough for our purposes:

  1. "Dinner will be done in twice the time it takes me to do the macarena."
  2. "I've been waiting eight lengths of the song Barbie Girl by Aqua!"
  3. "I am 8.34 University of Auckland Bachelor of Sciences old"

However, as physicists are infamously dull at parties, they chose more boring references:

  1. "Solar Second" = Divisions of a single day-cycle, defined by how long between the sun being in a certain sky-location.
  2. "Ephemeris Second" = Divisions of a solar year (as measured by the predictable number of oscillations of a quartz crystal during that period)
  3. "Atomic Second" = 9,192,631,770 cycles of transition radiation of caesium-133 at 0K (or extrapolated to 0K), which aligned with the past accepted period of the Ephemeris Second.

Why the increasingly specific definitions? Well let's look out our 6 references:

  1. What about when I'm all caffeinated up and I do the steps of the macarena faster than I should?
  2. What about when my old tape player is dying, and it starts playing Barbie girl at 95% of the intended speed?
  3. What if I took longer or shorter than the average amount of time to do a BSc? Whose BSc are we referencing?
  4. What about the summer-winter difference in day length?
  5. What about things that affect quartz oscillation?
  6. Huuh?

We use the atomic second, not because we believe it is a perfect universal unchangeable truth, but because it holds pragmatic value. Measuring time relative to caesium-133 radiation is good enough for our best technology to keep time, and ping data across satellites. No one ever said it was perfect, but they did agree it was good enough. The number "9,192,631,770" was chosen so that the 'second' didn't change as an experienced length from the previously accepted length, even though it was now defined more precisely.

Non-Temporal Measures of Linear Time

What about other ways to measure time? What about using spatial metaphors? We like space. Space is distance. Distance is physically perceivable. We like distance.

Whilst measuring time in meters or feet, sounds ridiculous it is super common and super intuitive to us.

When you're a passenger in the car you will often ask the driver how far away you are from your destination. Funnily enough, most of the time you really don't care about the distance. You're just a passenger, you aren't doing anything that is affected by distance. You're not laying down a string, or a line of paint, and you probably don't care about fuel consumption at this point. You are just sitting in a seat. What you want to know is how long will you be sitting in this seat, but you are asking in terms of spatial distance.

This works because there is an approximately constant relationship between spatial-distance-to-destination and temporal-distance-to-destination (we call this speed/velocity). If you know you'll be averaging around a certain speed, if you know the distance, you can get a feel for the approximate time you have to wait, buckled up in your seat.

This is what is being done with caesium-133 (and the solar-year/day). Our 'distance' is 9,192,631,770 periods of radiation. Our 'approximate speed' is 9,192,631,770 per second.

However, what happens when your caesium starts doing things it shouldn't? What happens when your car hits traffic on the way to your destination? And what about your friend who is driving from a different place to the same destination in a faster car, on a route with less traffic?

Enter Stage Left Einstein.

Relative Time

If we're talking about time, we naturally must talk about Albert Einstein.

Einstein, you know, crazy hair guy, known for the 1921 Physics Nobel for (among other things) the photoelectric effect, writer of the famous mass-energy equivalence law (E = mc²), and snatcher of Newtonian Mechanics' wig clean off Isaac's dead skull.

What we are referring to is Einsteinian General Relativity, which was important for space-y, black-holey physics, and showed that Classical Newtonian hurr-durr-apple-fall-down physics was insufficient in this macrocosm. Related (and partly included in General Relativity) is the notion of Time Dilation, this is the meat of what we'll talk about when we talk about Relativity.

Time dilation is the phenomenon of two people with identical, perfectly functioning atomic clocks that are in-sync, separating and doing their own thing, coming back together, only to find that their clocks are no longer in-sync with each other.

This phenomenon looks at our lab's microcosmic notion of constant linear time, and roundhouse kicks it in the face.

Back to our out-of-sync clocks. Let's call these people A and B, and after returning from their journey, A's clock has passed more time (reads as later) than B's.

Physics has found two main thing's that cause this:

  • Relative Velocity: if B was moving incredibly fast (near light-speed) while A wasn't.
  • Gravitational Potential Difference: if A was siting far away from a massive body/planet while B was sitting on the surface of said body.

Whilst both of these have been experientially verified, discussing the roles, effects, and proportional impacts, are far beyond A) my knowledge, and B) the point of this article. What we can say is that the Gravitational Potential Difference and the related physics, is a major issue when it comes to satellites (e.g. GPS) and the international space station. In short, clever engineers have to take into account that time bends and stretches in (mostly) a predictable fashion. They have to include time dilation in their formulae when constructing devices.


The current physical explanation of linear and nonlinear time is an intricate mesh of inter-connected concepts that I lack the skills to pick apart. However, an important linear-time-related concept to discuss is entropy.

Entropy, the conceptual bane of my existence in undergrad biochemistry. Entropy is, whilst a massive and complex abstraction, bizarrely intuitive. We have nice metaphors and visual symbols to describe the concept or process of entropy.

Entropy can be considered the concept which defines the direction of the arrow of time. You will also hear that it is intrinsically related to disorder, chaos, and/or distribution.

Think of a single drop of blue dye being dropped into glass of clear water. A first all the dye molecules are clustered together in a blob. Nice. Fairly organised. Together. Over time, they will bleed and diffuse into the water turning it all blue.

Clear water with dark blue drop becomes not so clear water that is uniformly not-as-dark blue.

Now the dye molecules are spread out, randomly intermingling with the water molecules. Whilst we know that the dye molecules will keep meandering around the water molecules (because... physics), we intuitively know that the blue dye-drop won't un-diffuse and reform in the centre of the clear water. Whilst it is, I suppose possible that all of those meandering dye molecules could meander back to the centre of the glass, thus reforming the dark blue blob, they don't.

Left to their own devices, dye-drops bleed out into water, ice cubes in a hot room melt, a fire burns away at a log, and a dropped vase shatters.

If I play you a video of a dropped vase shattering, you would be able to intuitively tell me if it was being played forward or in reverse.

The second law of thermodynamics tells us that the entropy of an isolated closed system can only increase and does so with every reaction. Whilst a small sub-section of that system may have its entropy decrease, for this to happen, the overall system will experience a greater increase in entropy outweighing the local decrease.

Similarly, if I were to play you a short clip of a pendulum oscillating, you would have a hard time telling me if it was being played forward or in reverse. However, if I showed you a massive clip of the pendulum, you would see a hand setting it in motion, and you would see the swing start to die down until the pendulum came to a halt. When viewing a greater portion of the video/cosmos, the linear time/entropy directionality would become evident.

So, entropy and time, where did it come from? where did it go? where did it come from Cotton-Eye Joe?

At this time our best answer is:

  • Where did it come from?
    • The big bang, when entropy was at a minimum
  • Where did it go?
    • ???

What happened before the big bang? Was there even a before the big bang? We don't know, our maths breaks down and we don't yet have the information to tell.

Where does time go? We used to like the idea of the expansion of the universe slowing and reversing its direction until an anti-big-bang, a big-crunch. This idea of cyclical time, moving forward, then reversing, then the universe crunching down to a singularity, then exploding out in another big bang: Fabulous. Symmetrical. Poetically satisfying. However, it turns out evidence suggests the rate of universal expansion is speeding up rather than decreasing. So... Who knows what’s going on? Not us.

Currently as per our understanding.

  • Time moves forward.
  • It's perceived as constant and linear for an observer but is seen to vary between different observers.
  • There was a point which functions as a time-start when entropy was either zero or at an official minimum.

That's about it. And even some of that we're not 100% sold on.

Linguistic Time


When it comes to language, the verb is the temporal super star. Verbs are actions manifested in language. Actions are temporally dynamic and can be:

  • Active states - e.g. being Mongolian
  • Transitive activities - e.g. eating a sandwich
  • Active events - e.g. completing something

If we wanna be really spicy, we can even encode information about when one of these activities happened.

Tense and Aspect

Let's talk about TENSE.

In English, especially as a native speaker, this is the main thing we think of as time.

We consider tense to be a division of all time into three regions:

  • The Past Tense, the 'before the now', that which has happened.
  • The Present Tense, 'the now', that which is happening.
  • The Future Tense, the 'after the now', that which has not yet happened but will.

You will note that tense revolves around this idea of the now.

Let's consider ASPECT.

Though some aspects are differentiated in English, we tend to consider this a bit more grown up in terms of grammar. I like to think of aspects as flavours. These flavours can be:

  • The Perfective Aspect, the singular, self-contained and completed flavour. Started, completed, done and dusted.
  • The Imperfective Aspect, the non-contained flavour. This can be subdivided.
    • The Ongoing Aspect, the singular activity non-self-contained flavour.
      • The Continuous Aspect, the singular mid-action flavour. A single snippet of the larger action.
      • The Progressive Aspect, the singular incomplete, ongoing, started but not finished flavour.
    • The Repetitive/Habitual Aspect, a non-singular event flavour. A series of discrete events.

We can also discuss a Neutral/Gnomic aspect, being considered an absence of aspect 'flavour'.

Aspect describes, as opposed to a location in time (tense), a flow and relationship with time.

In English we pair a tense with an aspect when conjugating verbs:

  • "I drank a cup of coffee"
    • Past Tense (before)
    • Neutral Aspect (no reference to any other activity)
  • "I had drunk a cup of coffee"
    • Past Tense (before)
    • Perfective Aspect (isolated)
  • "I am drinking a cup of coffee"
    • Present Tense (now)
    • Continuous Aspect
  • "I will have been drinking a cup of coffee"
    • Future Tense (after)
    • Progressive + Continuous Aspects (started, ongoing, not completed)


Grammatical Mood/Mode/Modality

In discussing time, we should also briefly mention the idea of grammatical mood. If aspect is the flavour of a verb, then grammatical mood is its colour. Mood can also be considered the why of a verb.

Why are you telling me this?

Is it a statement? An instruction? A question? Has/will it actually happen or is this just conjecture?

Much like the types of aspects, we can group the different moods. Below is a list of some (but by no means all) of the grammatical moods:

  • Realis Moods (statements presented as true observations/facts)
    • Indicative Mood:"The hat is blue." (The statement presents itself as a fact)
  • Irrealis Moods (statements which make no claim to be objective observations)
    • Deontic Moods (should's)
      • Commissive Mood (promises or threats): "I'll help you move" (not claiming 100% fact but commits to it)
      • Imperative Mood (commands/instructions):"Go away!"
    • Epistemic Moods (could's)
      • Interrogative Mood (questions)
      • Subjunctive Mood (expresses personal attitude/stance/and other stuff)
        • Note that this is a hard one to describe and is minimally used in English/isn't differentiated from the indicative.
        • "[I feel that] it's important that you drink enough water."
    • Dependent Moods (would's)
      • Conditional Mood (English subdivides this)
        • Factual Conditional Mood (if A then B): "When I'm hungry, I eat."
        • Predictive Conditional Mood (if A, then WILL B): "If you give me your laundry, I will clean it."
        • Counterfactual Conditional Mood (if A [known to be false], then WOULD B): "If I had the money, I would have bought it."

Note that there are many potential moods that can be discussed, but that is an activity for a later date.

Back to time. When placing a verb in a temporal situation we must ask ourselves three questions:

  • Do I want to encode this as Realis or Irrealis? Is this a description of (apparent) fact?
  • Do I want to encode where this event falls relative to The Now?
  • Do I want to encode or flavour information about the context/temporal relationships of this activity relative to a reference?

While not all languages employ all three of these (Mood, Tense, Aspect), or employ these with unique morphemes (e.g. "will" suggesting either the future or an outcome of a condition), it seems that all humans have an innate understanding of them. This is seen in Bohnemeyer et al's 1998 TEMPEST study, comparing the speakers of a tenseless (aspect dependent) language (Yucatec Mayan) with a tense-and-aspect one (German). Bohnemeyer found no difference in comprehension or rate of success of communication of complex temporal relationships.

Perhaps we might consider tense, not as distinct from aspect. Whilst aspect flavours elements of a time-relationship, tense is purely a set time-relationship to the now.

However, you slice it, amongst all three of our discussions one question has been sitting in the corner, watching. The ever-moving, yet ever-stationary spectre that haunts time. This question is just as philosophically abstract as it physically and biologically grounded: What is The Now?

The "Now"

Psychologically we might consider the 'now' to be two simultaneous, external and internal, images.

  1. What is happening around me? What am I seeing? What am I hearing? What am I feeling? Where in space is my arm. Am I hungry? Does my knee hurt. Do I need to pee?
  2. What am I thinking? Am I feeling an emotion? Am I subvocalising a sentence in my head or just observing and processing data?

With regards to the external image: Our perception of time measurement is subject to near-countless biases, distortions, and illusions. These are simply a function of the imperfect, squishy, biological nature of our being. Our event-time perception for different types of stimuli are distorted. Some signals from some sensory organs take longer to process and make into a meaningful image than others. Some types of pain signals travel up the nerves to the brain faster than others.

The external image of the now cannot, by definition, be perfectly in sync with the actual external world. You can't be "seeing" something happen, "as it happens", because your eyes and brain need a fraction of time to actually "see" it. But more annoyingly, there isn't even a universal delay across sensory modalities. Your brain just forms the parts of the external image when it receives the parts.

The timing of the internal image is harder, if not impossible to measure or discuss given that it is not bound directly by external temporally relevant stimuli.

Physically, discussing the present is a bizarre undertaking for two reasons. The first is a bit of a quantum physics deep dive, the Heisenberg Uncertainty Principle.

In short, this states that even in purely theoretical situations, one cannot measure or know both the exact position and velocity of an object.

This idea manifests itself in our idea of the now. Knowing exactly where something is, and where it is going is impossible, dearest Werner Heisenberg made that abundantly clear.

As a poetic and rather metaphoric parallel to this, neither can we know where we are AND where we're going exactly. We know the general direction, forward. In time we are moving forward, thanks to old friend entropy. But for now, that's all we can know.

The second and more direct issue physics gives us when defining the now is that it is self-referential by nature. The now is the transition point between the real past and the unreal future. The past and the future are temporal spaces which we can only define relative to the now. Much as the physical and cosmological giant of Relativity screws us over when discussing collinearity of time, so too does it when defining the location of anything. If we can only define location relative to something, how do we define a temporal location that only exists in that it exists.

This harrowing thought leads us to a question. Is the present even a temporal location? Does it even exist?

In terms of linear time, "the past" is what has been recorded, "the future" is what hasn't. All data that is recorded or encoded in marks on a board, or electromagnetic waves, or particle locations, are manifestations of the past. In this sense, the past doesn't just shape the present, but rather forms it. For each datum, there is a stimulus, a recording, and the resulting record. Chalk hits a black-board, powdered chalk clings to the board, a white line remains as record of the encounter. If the present is to be discussed as existent, it is not a temporal location, but rather a process. The present isn't the act of being or doing, but rather recording.

We record via memories, via the changes we make to our surroundings, pushing in a chair, wiggling an eyebrow, activating a nerve cell whose metabolism ever so slightly increases the entropy of the universe. No matter the size, our existence, internal and external, is recorded. We might think that we live in the present, experiencing it as a place or thing, but when we break down the physical reality of it, we aren't in the present, we DO the present, and we ARE the past. 

Banner image edited from European Southern Observatory's 360 panoramic of the Milky Way Galaxy.

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