What is Time? | General Physics Discussion

[Shooting Star]

So, I could use any clock, for example a sand glass? I don't think that's a good way to answer (infact he knew that was not an answer).

Even I know that's not the answer, taken literally. But if you think about it, since we don't know much about time, this utilitarian approach is the best perhaps.

A sand glass isn't a self-contained clock on its own, but a sand glass combined with a suitable planet to complete the mechanism would work as a clock for that purpose.

Sand glasses or pendulum clocks or anything which works on gravity is inadmissible as a clock in GR.

After many years of research, we have come to the consensus that atomic (or maybe subatomic) vibrations keep the best time. That's why we use those phenomena to measure time; or has it simply become a matter of definition that those keep the right time?

 

[InfinateLoop]

I thought time was successive intervals?
How does that not sum everything up?
Is it because of GR?

I love this topic!

 

[Rade]

... Most philosophers agree that time does exist but they haven't yet been able to determine what it exactly is...

According to Aristotle, Physica, Book VI, he claims the following about time:

...time is (number of motion of a physical thing that is counted) that is intermediate between indivisible moments...​

Suppose three moments, A, B, C and a physical thing {T} in motion in "space" in relation to them. From my understanding of Aristotle, the moments are indivisible and have neither motion nor rest, thus they are outside of time, yet they are the limits of past and future time, such that:

the past ~ ---- time 1 ----> |A|--- time 2 -{T}--> |B| ------- time 3 ---{T}----> |C| ---- ~ the future​

In the above diagram consider the relationship of time 2 & 3 to moment |B|. There exists infinite numbers of motions of the thing {T} in space that can be counted in time #2 leading to |B| (the past) and in time #3 leading away from |B| (the future) and these motions that can be counted are "time". Thus, moment |B| is both a limit of past time (time#2) and future time (time #3), and while it can be said that |B| is in this sense, as a limit, a part of time, there is no time within the moment|B|, since time is always divisible while |B|, because it is a moment, is always indivisible. And see that while time #2 is the past of moment |B|yet also is time#2 within the future of moment |A|.

Thus, as the concepts "odd" and "even" are within number, so the concepts "past" and "present" and "future" (moments) are within any time. So, time will never fail to exist if there is motion of a thing in space that exists, for where there is motion, there is always a beginning to time.

Now, Aristotle also holds "space" = "that which is intermediate between existents". Thus, it is possible to suggest that Aristotle would claim that;

"space-time" = that which is intermediate between moments of existents.​

Applying the above diagram, suppose two existents {E1} and {E2}, and they are in motion at two different moments |A'| and |B'| in space-time:

the past ~ ---- time 1 ----> |A|--- time 2 -{E1|A'|}--> |B| ------- time 3 ---{E2|B'|}----> |C| ---- ~ the future​

So, here we see that "space-time" is that which is intermediate between {E1|A'|} and {E2|B'|} as these two existents relate to the three moments A, B, C and their respective concepts of past and future time.

This is my understanding of what Aristotle may claim about the philosophic question..."what is time" as relates to physical things that exist that follow the laws of nature.

 

[pervect]

OK, given that we are now talking about Aristotle, and given the title of the topic, I think it's time (probably past time) that I move this to the philosophy forum.

 

[Shooting Star]

Thank you, Pervect.

I was about to suggest to a mentor to lock the thread, but you, being the expert, have taken better care of it. A bit rough on Aristotle, who, by the standards of his day and two millennia after, is considered to be one of the greatest minds in recorded history.

 

[Kurdt]

I think in summary then Rade, Aristotle would consider time as the interval between events. Its interesting his use of the term indivisible moments. Does this imply Aristotle thought there was a minimum 'duration' (i.e. interval between events) in which one could not have any smaller duration. In essence a quantum theory of time.

 

[ripcurl1016]

Time is not the changing of events but the change between events to one another. An event itself cannot change, an event is definite. Now if an event is definite it has certain characteristics about it that cannot change either. An event cannot be past, present, and future at the same time. Event A starts out as a future event, it then becomes present, and goes on to past. This is how we know time, from future to past. So A "has been" future, "is" present, and "will be" past. "Has been" only being distinguished from "is" by being existent in the past, and "will be" is only distinguished by being existent in the future. So if the future is the presents past, and the past is the presents future, how much sense does time being real make?

 

[epenguin]

I say that time is what clocks measure, and that is all it is. In other words time is measured by events. There is no room in physics or philosophy for anything else. There is no time thing which 'flows' and oh you can measure it with clocks.

Classically all proper clocks would be thought of as agreeing regardless of time, space and movement, in relativity that is changed in an understood way, but different true clocks traveling together have to agree.

 

[DaveC426913]

...different true clocks traveling together have to agree.

Well, they agree because they're calibrated to agree.

 

[epenguin]

The best ones we call standard have to agree with each other surely? To within a certain amount then we say our best clocks have measure time that accurately. With those we callibrate other less satisfactory ones. It is not that any clock is as good as any other. Once the rotation of the Earth was our clock, so it would then have made no sense to say the Earth was slowing, for that we must have a clock we know is better, it is not arbitrary.

 

[lightarrow]

I say that time is what clocks measure, and that is all it is. In other words time is measured by events. There is no room in physics or philosophy for anything else.

Very good. Now you have to define the word "clock".

 

[Shooting Star]

I say that time is what clocks measure, and that is all it is.

Very good. Now you have to define the word "clock".

He has already defined it in his above post...

 

[D H]

So if we take the famous thought experiment of a man on a train traveling near the speed of light and a man on the waiting bay for the train to pass. The man on the bay (lets call him B) saw that the man on the train (lets call him man A)'s time slowed down, i.e. B saw A's time slow down, but also, A saw B's time slow down.
1) Whose right, they both can't be right?

They are both right.

2) Is there some field surrounding the train where time is allowed to slow down or what?

There is no field. That each of the two men see the other man's clock running slower than his own is purely a function of the non-zero relative velocity between the two men.

 

[lightarrow]

He has already defined it in his above post...

Please?

 

[Shooting Star]

I say that time is what clocks measure, and that is all it is.

Very good. Now you have to define the word "clock".

He has already defined it in his above post...

Please?

In effect, he has already defined clock as that which measures time.

This is a circular definition. However, irrespective of how many links you introduce in the chain, ultimately it will be just a big circle. Isn't that why we are still discussing this, on record, approximately over two and a half millennia?

 

[Greddy]

Hi, I am kinda new here. Me and some other dude had a discussion about if Time did really exist.

Instead of making a new thread about time, I though crashing/hijacking this thread instead.

Edit by Evo: Let's keep this thread to the discussion going on here.

 

[Shooting Star]

A tremendous effort, but could you please reduce the length of your essay the next time? Something happens to me after a minute...:zzz:

(Seriously, it's too big, with all those links.)

 

[Greddy]

Hehe, I didn't realized that I was making an long "essay", so I apologize
I made the short resumè of the discussion we had, so you could skip those links.
but then again, It wouldn't have made sense if I leaved out those links.
(Links are there so you wouldn't have to search for relevant post among the troll posts)

 

[epenguin]

In effect, he has already defined clock as that which measures time.

This is a circular definition. However, irrespective of how many links you introduce in the chain, ultimately it will be just a big circle. Isn't that why we are still discussing this, on record, approximately over two and a half millennia?

I don't think it is, at least it is trying not to be. I think we can accept without further analysis that there are observed regularities in nature, and of events, and then of events 'happening together', resisting the temptation to say 'at the same time.' We can count. We can say 'every 365 days' - idea of duration not needed but only of events like a shadow passing a mark - 'the stars go back to the same position'. We do not need the events to be repetitive, in fact the best clock for thinking about it is the Tait clock, which is successive relative positions of some stars which are in free (not being accelearated by attractions) motion. Work it out, that is not circular. What we need is:
more than one such clock and to find that they agree;
a reason to believe that they are simple and understood. For the Tait clock the reason would be that each star is very far from the influence of other bodies.

These things are observable. Time is not a thing, but just what you invent to relate these observations; you could just relate them to each other. You invent 'seconds' as a convenience. It is like you might live buying and selling real things, to do this you can have dollars $ or other currency units in a bank which you never see. Currency units do not need to be real. You are so used to talking about them you may think of them as real. You might prefer the most stable currency, the one with most constant relation with the most important simple desirables. In fact ideally you would make such a desirable your unit of currency.

Then in physics you observe things which are not as regular as your clock, and you then say they are complex and need theories to be invented to explain why and exactly how they are not regular. Equations in tems of t which you think of as real like you think of $ as real, but you are just relating phenomena to your clocks which you think are simple.

 

[Rade]

I think in summary then Rade, Aristotle would consider time as the interval between events.

No, this is not my understanding. Time is an interval between "moments" for Aristotle. An "event" is not a moment, an event is what occurs within the interval called time--a coming to be or a doing away with.

Its interesting his use of the term indivisible moments. Does this imply Aristotle thought there was a minimum 'duration' (i.e. interval between events) in which one could not have any smaller duration. In essence a quantum theory of time.

The term" indivisible moment" is my term, Aristotle defined time as being intermediate between moments, then defined moments as being indivisible, so he should have no problem with the term "indivisible moment" since the opposite for him would be a logical contradiction.

Your second question is interesting--here is what I found.

In quantum theory, there is no time smaller than Planck Time, so what would Aristotle say about this ? I think we find the answer in Physica, Book III, Chapter 6. Recall that for Aristotle time is not a magnitude, but "time is a kind of number" (Book IV, Chapter 11), it is "what is counted" between moments, and in Chapter 12 he states "since time is number". So, it it safe to claim that Aristotle holds that time is number, a kind of number related to what is counted about motion between moments.

Now, in Book III, Chapter 6 Aristotle discusses the infinite. And here he claims this..."it is natural too to suppose that in "number" (quote added) there is a limit in the direction of the minimum". Thus, since time is number for Aristotle, I suggest that he would hold that time also has a limit in the direction of the minimum, and that this concept of the limit of time in the direction of the minimum is what we today call Planck Time. Furthermore, Aristotle makes this claim..."hence number must stop at the indivisible". So, here we see that Aristotle would claim also that "time" must stop at the indivisible, and recall that the indivisibles between time are the moments. Thus I conclude that Aristotle would agree that there exists a smallest time duration between any two moments--what we call today Planck Time--it would appear that Aristotle is the great..great grandfather of quantum theory as relates to time as a number of what is counted in relation to motion.

 

[Drachir]

What Time Is

In his book Time, Matter, and Gravity (copyright 2004), Morris G. Anderson points out that the word ‘time’ has two different meanings. For clarity he refers to one meaning as ‘TIME’ (uppercase), and the other meaning as ‘time or Time’ (lower case). ‘What TIME is it?’ and “How much time will it take to get there?’ illustrate those two different meanings. The first meaning or usage is existential, the second quantitative.

Anderson defines TIME as where something is, was, or will be: e.g., where the hands are on a clock, where the sun is in the sky, and where the Earth is in its solar orbit. He identifies time as a change of TIME (a change of where something is): e.g., from four o’clock to six o’clock, from sunup to sundown, from winter solstice to summer solstice.

Using Andersons nomenclature then, TIME is an abstraction we make from the positions of things, while time is an abstraction we make from the motions of things. Since time is defined in terms of things, TIME or time without things can have no meaning for us; neither can have existence independent of things. Therefore the notions of TIME itself or time itself are meaningless.

 

[moving finger]

In his book Time, Matter, and Gravity (copyright 2004), Morris G. Anderson points out that the word ‘time’ has two different meanings. For clarity he refers to one meaning as ‘TIME’ (uppercase), and the other meaning as ‘time or Time’ (lower case). ‘What TIME is it?’ and “How much time will it take to get there?’ illustrate those two different meanings. The first meaning or usage is existential, the second quantitative.

Anderson defines TIME as where something is, was, or will be: e.g., where the hands are on a clock, where the sun is in the sky, and where the Earth is in its solar orbit. He identifies time as a change of TIME (a change of where something is): e.g., from four o’clock to six o’clock, from sunup to sundown, from winter solstice to summer solstice.

Using Andersons nomenclature then, TIME is an abstraction we make from the positions of things, while time is an abstraction we make from the motions of things. Since time is defined in terms of things, TIME or time without things can have no meaning for us; neither can have existence independent of things. Therefore the notions of TIME itself or time itself are meaningless.

a simpler way of saying this is:
Time is the way that we measure change. If there is no change, then there is no time (ie it makes no sense to talk of time in absence of change). Time "exists" only because there are changes in the world about us - it is the way that we measure such changes. In this sense, time is indeed an abstraction.

 

[Rade]

In his book Time, Matter, and Gravity (copyright 2004), Morris G. Anderson points out that the word ‘time’ has two different meanings.

Well then, if true, then the claim of Anderson is false because there are not two meanings of "time", only one. Time is that which is intermediate between moments (Aristotle, Physica). For a "thing" to be in "time" between moments means that BOTH the (1) essence of the thing, and the (2) motion of the thing ARE MEASURED BY TIME SIMULTANEOUSLY between the moments. Where Anderson is confused is that it is not "time" that has two meanings, but the concept of a thing being "in time" between moments that has two meanings--(1) as when we say that a thing exists when time exists, and (2) as when we say that a thing exists as a number which is a measure of motion of the thing between the two moments. Thus, things that are in time are contained by time in the same way that things in place are contained by place, and as "place" has meaning, so too "time"

We see also that this claim of Anderson is false...:

... Using Anderson's nomenclature then, TIME is an abstraction we make from the positions of things, while time is an abstraction we make from the motions of things. Since time is defined in terms of things, TIME or time without things can have no meaning for us; neither can have existence independent of things. Therefore the notions of TIME itself or time itself are meaningless.

...for, as stated above, time is that which is intermediate between moments (NOT THINGS). Time is not defined in terms of things, but in terms of moments, but the essence AND motion of things are measured simultaneously by time in relation to moments (= the present, the now). Where Anderson errors is that he fails to understand that it is the concept of "thing" that is meaningless to us without time, for it is only via time that we can measure if a thing has its existence in motion or in rest. If time does not contain a thing, then the concept of thing neither "was" nor "is" nor "can be", but then do we say that the concept of things is meaningless ? --of course not--things and time both derive meaning from their dialectic relationship.

 

[Drachir]

Aristotle's definition

Rade, in #54 you wrote:

Well then, if true, then the claim of Anderson is false because there are not two meanings of “time”. Only one.

Do you mean that in the statements “The time is ten o’clock.” and “One hour is not a long time to wait.” ‘time’ has the same meaning?

You also wrote:

Time is that which is intermediate between moments (Aristotle, Physica).

My dictionary defines the word ‘moment’ as an indefinitely short period of time. Substituting that meaning of ‘moment’ into Aristotle’s statement yields – Time is that which is intermediate between indefinitely short periods of time – a failed definition since a word cannot be defined in terms of itself. Does ‘moment’ have a definition, in the present context, where ‘time’ does not appear? Without such a definition of 'moment' Aristotle’s definition of ‘time’ is meaningless.

 

[moving finger]

My dictionary defines the word ‘moment’ as an indefinitely short period of time. Substituting that meaning of ‘moment’ into Aristotle’s statement yields – Time is that which is intermediate between indefinitely short periods of time – a failed definition since a word cannot be defined in terms of itself.

in simplistic terms, yes this is true - but in reality the fundamental meaning of all words is grounded in other words... if one looks hard enough, one is bound to find circular definitions because there is no ultimate definition of any word except in other words...

 

[octelcogopod]

in simplistic terms, yes this is true - but in reality the fundamental meaning of all words is grounded in other words... if one looks hard enough, one is bound to find circular definitions because there is no ultimate definition of any word except in other words...

The reason for this is because we can never explain anything physical in reality without using other words that explain the individual parts of what we're explaining.
Everyone knows what an apple is, but an apple is also a lot of other things combined, of which there are words for as well (green, round, hard etc), if there were no words for the individual parts then we would have to find out what it is.

I find that an interesting thought concept.

 

[Drachir]

The meanings of words

moving finger, if your claim that

there is no ultimate definition of any word except in terms of other words

were true, there could be no languages since it would be impossible to learn the meaning of one’s first word. When a toddler points to the moon and a parent says “moon”, the toddler knows the meaning of that word without reference to other words. The fundamental meanings of all words are grounded in the words representing things outside the mind. Sunrise, the sun at its zenith, sunset, sunrise to sunset, and a series of heartbeats -- good enough for timing swinging candelabras – are some of the real world bases for our subsequent notions of time.

My position regarding circular definitions is that the circle can usually be opened with some etymological analysis. Some circular definitions arise from use of metaphors that fail to carry over sufficient meaning.

I think that Anderson’s position definition of time, and his attention to the two distinctly different uses we have for the word ‘time’ (particular time, and time duration) are noteworthy clarifications. His definitions of time enabled him to develop a theory uniting gravity and the wave behavior of objects that gives accurate predictions of phenomena including the bending of starlight by the sun, the advances of the precessions of the planetary orbits, the velocity dependency of the periods of clocks, and the gravitational redshift of light. These remarkable results affirm the correctness and utility of his definitions of time. The Anderson theory also avoids the singularities that mar GR.

 

[Rade]

... Does ‘moment’ have a definition, in the present context, where ‘time’ does not appear? Without such a definition of 'moment' Aristotle’s definition of ‘time’ is meaningless...

Yes, Aristotle defines the "moment" as being outside of time--for the obvious reason you raise--so his concept of time holds within the constraints of his definitions. Of course he logically argues why moments are outside of time, a good read.

Do you mean that in the statements “The time is ten o’clock.” and “One hour is not a long time to wait.” ‘time’ has the same meaning?

Yes, of course they do. When you state that the time is ten o'clock, you claim that which is intermediate between 9 o'clock and 11 o'clock where the latter at two moments. When you claim one hour is a long time, the 1 is intermediate between say 1/2 and 2, thus you claim a length of time that is intermediate in magnitude between two magnitudes. Now, you raise a point addressed by Aristotle, that time can be "described" as being "continuous" (long vs short) and as "number" (many vs few)--but it only has one meaning (one definition), as I previously posted.

 

[Rade]

...These remarkable results affirm the correctness and utility of his definitions of time. The Anderson theory also avoids the singularities that mar GR.

But now I am confused, because I responded to this statement you claimed to be from Anderson:

Therefore the notions of TIME itself or time itself are meaningless

So, how can he claim that he uses a meaningless concept to derive remarkable results ? Also, as I posted above, Anderson can make no claim of some new understanding of time, what he claims (continuous vs number aspect of time) has been around for > 2000 years. But, perhaps Anderson has used Aristotles definition of time for new understanding of physics--this would not surprise me at all--only confirms that Aristotle was a pretty smart fellow indeed.

 

[moving finger]

moving finger, if your claim that were true, there could be no languages since it would be impossible to learn the meaning of one’s first word. When a toddler points to the moon and a parent says “moon”, the toddler knows the meaning of that word without reference to other words.

And if the poor toddler is born blind? This argument leads to the conclusion that a blind person could never understand the meaning of the word "moon"

Sunrise, the sun at its zenith, sunset, sunrise to sunset, and a series of heartbeats -- good enough for timing swinging candelabras – are some of the real world bases for our subsequent notions of time.

And each of these can be defined in terms of other words (this is just what a dictionary does). I do not need to be able to see a sunset in order to understand what a sunset is.