What is your description, understanding or definition of "Time"?
Time fascinates me. I love any films that deal with the topic. Is it linear or cyclical? Discrete or continuous? Does it actually exist outside our conscious awareness of passing events? Are all "nows" the same? When is the end or beginning of an event? Why does it seem to have a direction? What would we be able to know about the world if we had no concept of time? Or if we had no standardised unit of time? What is the relationship between time, energy, rate and change?
Comments (58)
Time is what a clock measures.
This is a path which few may tread. The poetry of science. :chin:
The trouble is, you think you have time - Buddha.
The distinction between the past, present and future is only a stubbornly persistent illusion-Einstein.
Quoting A Seagull
I love how these are both excellent but also completely different answers.
Let's not put the cart before the horse. "Span across phase-space..." - which phase space? The phase space of classical thermodynamics, apparently. You need to start with the framework of thermodynamics, which, as the name suggests, involves time. That is the important bit. That the positive direction of the time is conventionally chosen as the direction in which entropy increases is almost an afterthought. The essence of this definition is that time is implicitly defined by classical thermodynamics. Which is OK as far as it goes, but we need not define time so narrowly and specifically; we can generalize this definition by stating that time is implicitly defined by dynamical laws of nature.
Great. Now define clock and measurement without referring to time.
Great. Now define clock and measurement without referring to time.
I don't need to define 'clock' all I need to do is teach you how to make one.
For 'measurement' read 'observe'.
A phase space, or configuration space, doesn't have to imply anything about time being presumed simply to conceive of that space. It's just a spatial representation of all the different possible states that a system could be in.
A span across such a phase space is thus a pattern of change: the system moving from one state to another through a succession of intermediate states. This is still before we have constructed any notion of time, just a span of possibilities, without any particular directionality to them; we could, so far as we've conceived thus far, scrub back and forth across that pattern of changes willy-nilly.
Time is most generally a measure of changes in the universe, so a span of time is a span of some sort like that, through the phase space of the universe, with every possible point in that phase space representing some possible state of the universe.
But time as we normally conceive of it is directional, so not just any span of the phase space counts as a span of time as we normally conceive of it. A universe at maximal entropy, for instance, may find itself wandering around through a bunch of possible states in no particular pattern, sometimes even repeating the same state, but we wouldn't normally describe that as time running forward and backward in time in such a universe. Rather, time has effectively stopped in such a universe: all those different maximally-entropic states are "the same time", because they're all the same distance along the direction through the phase space in which we reckon time to point: the direction from less entropic states to more entropic states.
The phase space of the universe being more entropic in one direction and less entropic in another is an anisometry: it's not the same in both directions. But the phase space is not globally more entropic in one direction and less entropic in another, so that anisometry is only local. You could look along the less-entropic ("past") direction until you hit a local entropic minimum, and then if you keep looking further in that same direction, you'll see entropy going up again, so locally (in the phase space) that direction is now "the future", even though it's the same direction that elsewhere (in the phase space) it's "the past". That local entropic minimum is "the beginning of time" from the perspective of states on either side of it.
We reckon less-entropic states as "past" and more-entropic states as "future" because memory-formation, like all processes, necessitates an increase in entropy, so the states of the universe that we remember are necessarily less entropic than the current state of the universe, and as we project patterns in those memories beyond the present, we construct an idea of the future.
There are necessarily more high-entropy states than low-entropy states though, so for every point in the phase space, more adjacent points are "immediate possible futures" than are "immediate possible pasts". Because of this asymmetry, possible pasts converge, while possible futures diverge. The further into the past you look, the more determined the universe at that time is. I.e. there are fewer possible states of the universe connected to the present state of the universe through incremental steps through the phase space toward less-entropic states, the more steps you take in that direction. In the limit, there is only one local entropic minimum, one beginning of time. But the further into the future you look, the less determined the universe at that time is. I.e. there are more possible states of the universe connected to the present state of the universe through incremental steps through the phase space toward more-entropic states, the more steps you take in that direction. In the limit that direction, you get the heat death of the universe, the "end of time" even though it's not the end of change, because all change is now inconsequential and directionless, no state of the universe is a possible future, they're all either equally present or else past.
(Oh and as for the "possible worlds" bit, that's because I consider this a form of modal realism, but with possible worlds more like Kripke's than like Lewis'. Lewis' "possible worlds" are more like time-lines in this model, while Kripke's possible worlds are more like possible configurations of the universe, points in the phase space, in this model. "Accessible possible worlds", in Kripke's terminology, are basically synonymous with "futures" in this model; other non-accessible possible worlds are either pasts relative to the actual present, or else counterfactual, "alternate timelines".)
FWIW, this isn't at all contradictory with "time is what a clock measures". A clock is just a system that undergoes routine, patterned changes, which is excellent for measuring distances across a configuration space, just like a ruler with its routine, patterned markings is excellent for measuring distances in ordinary space.
I'll show you later.
I offer two similar definitions given by Charles Sanders Peirce.
When you ask something like "what is time?" you are asking "how do we use the word 'time'".
Now, any and all of the definitions set out in words here are at the best incomplete, and more likely simply misleading. For example @fhorrest strings together big words, and immediately @SophistiCat puts those words in contention. @A Seagull attempts to set out an example and has this thrown back at him, again by @SophistiCat... Worst, @3017amen seems to think you are mistaken, arguing form authority.
Hence my showing instead of stating.
Point being, you already know what time is, since you are a competent user of English. And indeed, the questions you ask are about time, hence presuposing that knowledge.
You will get better answers to some of your questions from physicist than from philosophers.
My advice would be to try a science forum. Or read a book.
Dream on!
What I'm trying to say is that time is the thing that causes time. It's illusory, but not an illusion. Appearances are always deceiving.
But before you can conceive of a phase space, you have to conceive of a theory that gives rise to that phase space. The phase space is just a slice of the theory; you need to lay out the theory first. And as you do, time will already be there, even if you haven't specifically identified it as such. So first you build the stage and place the backdrop and the decorations, and gather actors and give them their parts, and set the play in motion. And then you can point to one of the actors and say: that is time. The play will not make sense without this central character, but neither will the character make sense outside the context of the play. The character of time emerges from the narrative of a physical theory, which in turn needs this character for its coherence. There is a mutual dependence here that makes straightforward reduction ("A is nothing other than B") impossible.
It's the same with time and clocks (@A Seagull): you can't conceive of a clock without already operating with a notion of time, but neither can you conceive of time without representing it using a clock, a physical process of a certain kind. The two notions are mutually dependent but not reducible to each other.
You (@Pfhorrest) make time specifically a thermodynamic actor, but of course time is present in other physical theories as well. It is just that continuum and statistical thermodynamics happen to be the only theories that we have in which time has a preferred direction. At thermodynamic equilibrium time disappears in the description of the macrostate, but it will still have a part to play at other scales and in other theoretical frameworks. It just won't have an overall preferred direction. ("Join the club!" says space. Space also has preferred directions, but only at some scales in some theoretical frameworks, e.g. in Earth-bound sciences.)
These definitions will fit any parameter in a parametric description: position in space, population density, Mach number, household income, etc.
It is fine to ask for an explanation of something that you already know and have a word for; we do that all the time, whether in physics or in philosophy. But when asked out of context "What is X?" you should reply back: "Why do you ask?" What sort of an answer are you looking for? A reductive definition? In terms of what? A contextual explanation? In what context?
Quoting neonspectraltoast
Is this to say that perception of past events are dictated by current mood, attitude or state of awareness? As in if I were to enjoy something in the past which I later discovered was a lie and now only see this past deception as a waste of my energy or pointless? Because we only store memories in the present. So I would imagine memories of the past are very much influenced by present state
Except the point of my question was not whether this is the ideal place to search for accurate knowledge on "time". My question was about your opinions. Your views. "You" are implicit in my questioning. So in fact this is exactly the right place for me to ask such a thing. And I got my diversity of replies...what i came for. Everyone can read a physics book on time....but i wanted to know... how does a selection of strangers articulate their experience of this phenomenon. Is it like me? Completely different to mine? Can I learns something from them?
And I did. Even a demonstration which I found very amusing.
No. The perception of past events has some component that reaches across time and space and can and does influence past events. The events themselves don't change, but you, in the present, always influenced them in the way that you did.
The future already exists, and the past exists in the future. The present obviously influences the future, but the past has a future as well.
That which at least one apparent intelligence has developed from itself, specifically for the use of itself.
This is exactly what I was refuting in the quoted bit. I suspect maybe the word “phase” is leading you to this conclusion, because a phase implies a temporal process, which is why I also named the synonymous term “configuration space” which has no such connotations. You don’t need any notion of time or any specific theory incorporating time to have a notion of there being multiple possible ways a thing could be. A configuration space is just a map of those possibilities. That has use in theories of dynamics to plot phases of cyclical processes, but you don’t have to think of such a theory before you think of the more general tool of a configuration space.
I know what a phase space is. A phase space describes relationships between free variables in a particular theory. A different theory will give rise to a different phase space with a different basis, depending on its ontology.
One test I use for definitions is: Does the definition point unambiguously to the word being defined?
In your two definitions: "that diversity of existence whereby that which is existentially a subject is enabled to receive contrary determinations in existence" and "a certain general respect relative to different determinations of which states of things otherwise impossible may be realized." fail that test. I don't think that anyone presented with the definitions alone would think that they referred to 'time'.
But seriously, an ant would experience time faster relative to us. And a whale slower. As the speed at which time passes is relative to the creature experiencing it. And outside of living experience there is only the speed of light or the movements of the stars to go by. Time can pass faster in one place than another, depending on the gravity, but it seems the same in either location so who cares
Hmmm... let's put this to the test. Have you seen Primer (link: IMDb)?
Yes-ish maybe. It's curved; it can go in various directions, some of which reach ends. Oddly these ends might further extend in some cases indefinitely into other universes. It's quite interesting...
...see e.g. here and here (two blog posts in a series by Dr. Dilts);
...and/or, here (PBS Space Time, Youtube; there are also multiple prior episodes reviewing concept of Penrose diagrams and such).
As for closed time loops, I hear there's a Chronology Protection Agency that works to prevent this.
No idea.
The answers "yes" and "no" are both correct depending on what the question is really asking.
The answers "no" and "mu" are both correct depending on what the question is really asking.
Depends on the event; and depending on the event, there may not be a beginning or end to it.
Because even with instruments postdiction is much easier than prediction. This is the same as the entropy answer others have given with a slight bent towards perspective.
To me this seems too speculative to have an answer.
Either we would use obvious non-standard units or too speculative to have an answer.
There empirically appears to be a symmetry of change regarding fundamental processes; said symmetry allows the notion of "rate of change" to be meaningful as a metric of time. The symmetry is sufficiently strong that processes appear to evolve nearly identically with respect to shifts in time; time translation symmetry per Noether's Theorem allows us to derive a particular kind of value we call "energy" as a conserved quantity.
(BTW disclaimer: I am not a physicist... I just take interest)
From Slaughterhouse 5 by Kurt Vonnegut
You dream of an instrumentalist utopia?
Indeed. Perhaps you are beginning to understand. Of course, "later" is only one aspect.
Time is information, the rate of which at any local point in space can be determined on a thermal spectrum from a state of solid stasis (absolute zero) to pure potential/potency (speed of light).
That still does not point to 'time'.
Quoting neonspectraltoast
This sheds light on Einstein's " all time acts on all other time all of the time ". Thanks
Time is an illusion. It is a man made dimension to locate a point in an ever changing space.
We don't really have time we have change. The change only has one direction - the direction of change.
We say forward in time, but what we experience is really forward in change.
When a glass falls off the table it shatters into a hundred pieces - this change can not be reversed.
And so it is for all change. Yet you state the following:
Quoting neonspectraltoast
I would be interested to know how you arrived at this?
Are you stating that all points in time / change are states of consciousness, and therefore remain malleable to consciousness?
The notion of "rate" requires "time". Circular argument. Sorry.
What makes time discrete? In what sense? As in that it has a beginning and an end? If so how would you prove your reasoning? Especially if energy cannot be created nor destroyed - if that is the case then there is always interactions and exchange of information which requires time.
Or is it discrete in passage - as in the unitary second - because seconds are arbitrary artificial constructs which arent natural to the universe. They are discrete because we chose their length.
Or is it discrete in rate? Because as we know from relativity the rate at which time passes varies depending on the speed of an object. Time dilation and contraction occur so even the second -our discrete unit- changes depending on the strength of gravity or velocities.
Not to voice agreement or disagreement, but one of the difficulties of Planck scale is that it's a precise scale... it's hard to square that against Lorentz transforms. If there's something discrete about time, it seems it should also be related to something discrete about space. (Then, there's also singularity concerns, such as what this scale's meaning is at horizons).
It is TRUELY substantive, if you believe time exists. As, if there exists a planck length of time, then time is a procession of discreet points like the frames of a movie reel. It is not continuous.
This would mean anything that exists over time also exists as a procession of discreet points - including ourselves :)
In what way is it substantive? Are there physical processes that go one way if time is discrete and another way if time is continuous? :chin:
This would mean we pop in and out of existance!
Maths is not my area, please correct me if I'm wrong.
Now replace the ball with an oscillator, such as a hydrogen atom. We could take a single period T of the oscillation as a unit of time. During one period of oscillation, the configuration of the atom changes, but it always returns to the same configuration after T. There is again no sense of change from one period to the next: this universe is a cyclic one, but at least there is some time.
Adding a second oscillator with the same period, or a factor of the first one's period, adds nothing. But what if we add a new oscillator with a period pi * the first oscillator's period? We can now count the tickings of the first oscillator with respect to the configuration of the second, and vice versa. The configuration of each oscillator is still cyclic, but the configuration of the system of the two will never repeat itself.
With such a system, I can make you a clock. Unfortunately, we don't exist, it's just two oscillators, but it's the thought that counts.
Time is one of the four dimensions of spacetime.