What is Time? | General Physics Discussion

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In summary, the concept of time comes from our awareness of change and is measured by counting cycles of cyclical change. Traveling forward in time is possible due to our understanding of change as a forward progression, but traveling backwards raises questions about the nature of change. The concept of time is also influenced by the development of Thermodynamics and how we view time culturally.
  • #36
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.
 
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  • #37
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?
 
  • #38
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.
 
  • #39
epenguin said:
...different true clocks traveling together have to agree.
Well, they agree because they're calibrated to agree.
 
  • #40
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.
 
  • #41
Here is what gets me;

Time slows down due to relativity, 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.

First of all,

1) Whose right, they both can't be right?
2) Is there some field surrounding the train where time is allowed to slow down or what?
3) WTF times infinity
 
  • #42
epenguin said:
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".
 
  • #43
epenguin said:
I say that time is what clocks measure, and that is all it is.

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

He has already defined it in his above post...
 
  • #44
kurt.physics said:
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.
 
  • #45
Shooting star said:
He has already defined it in his above post...
Please?
 
  • #46
epenguin said:
I say that time is what clocks measure, and that is all it is.

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

Shooting star said:
He has already defined it in his above post...

lightarrow said:
Please?

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

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?
 
  • #47
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.
 
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  • #48
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.)
 
  • #49
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)
 
  • #50
Shooting star said:
In effect, he has already defined clock as that which measures time.:wink:

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.
 
  • #51
Kurdt said:
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.
Kurdt said:
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.
 
  • #52
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.
 
  • #53
Drachir said:
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.
 
  • #54
Drachir said:
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...:

Drachir said:
... 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.
 
  • #55
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.
 
  • #56
Drachir said:
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...
 
  • #57
moving finger said:
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.
 
  • #58
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.
 
  • #59
Drachir said:
... 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.

Drachir said:
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.
 
  • #60
Drachir said:
...These remarkable results affirm the correctness and utility of his definitions of time. The Anderson theory also avoids the singularities that mar GR.
:confused: But now I am confused, because I responded to this statement you claimed to be from Anderson:
Drachir said:
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.
 
  • #61
Drachir said:
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"

Drachir said:
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.
 
  • #62
moving finger, your last sentence above
I do not need to be able to see a sunset in order to understand what a sunset is.
contradicts your second sentence above
This argument leads to the conclusion that a blind person could never understand the meaning of the word "moon"
All of our words ultimately lead back to things that we can sense. Langauge begins when we recognize the correlation of a symbol (spoken word, printed word, or language sign) with something that we can sense.

Your understanding of an unseen sunset is only possible because we define things we cannot sense in terms of what we can sense.

We cannot sense time. Anderson has defined it in terms of the positions and the changes of positions of things that we can sense.
 
  • #63
Drachir said:
moving finger, your last sentence above contradicts your second sentence above.

That's because the second sentence is not supposed to agree with the first sentence - rather it follows logically from the argument in YOUR earlier post, which argument I believe is false (hence my second sentence would also be false - therefore no reason why it should agree with my first sentence).

Drachir said:
All of our words ultimately lead back to things that we can sense. Langauge begins when we recognize the correlation of a symbol (spoken word, printed word, or language sign) with something that we can sense.
I agree that humans develop their language in conjunction with sensory input (sensory input is how we normally learn a language in practice), but I do not agree that sensory input is a necessary pre-requisite for the in-principle acquisition of knowledge of a language.
 
  • #64
moving finger, I referred to your second and last sentence.
 
  • #65
I can give you what I think time is exactly, it is only one dimension that is smooth, curved, has a intrinsic motion of dilation, and is always measured as a constant locally. Planck named it the smallest common denominator of reality, and I think we measure it relative to ourselves, starting at one Planck’s time after the big bang.
 
  • #66
Time is what you read of a clock.
 
  • #67
I say that time is what clocks measure, and that is all it is.
Time is what you read of a clock.

A atomic clock measures the intrinsic motion of a cesium 133-isotope, a light clock measures the intrinsic motion of a photon between mirrors, so if time is what a clock measures or what you read of a clock, does it mean that time is intrinsic motion? Can I think of a cesium 133-isotope as a little bundle of time? Can I think of a photon as a little bundle of time? If I think like this doesn’t it seem to make time the anther, with everything that exists with intrinsic motion being the motion of time?
 
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  • #68
with everything that exists with intrinsic motion being the motion of time
Time is not motion--time is the MEASURE of motion and of being moved, time is the "number of motion". Time is a type of number. Time is what is counted, not that which with we count [Aristotle, Physica, Book IV]
 
  • #69
Drachir said:
moving finger, I referred to your second and last sentence.
sorry, my typo. What I should have said was:

That's because the second sentence is not supposed to agree with the last sentence - rather the second sentence follows logically from the argument in YOUR earlier post, which argument I believe is false (hence my second sentence would also be false - therefore no reason why it should agree with my last sentence).
 
  • #70
Moridin said:
Time is what you read of a clock.

Does this sound familiar to anybody who has read the full thread? The clock hand has turned a full circle...:wink:
 
<h2>1. What is time?</h2><p>Time is a fundamental concept in physics that measures the duration and sequence of events. It is often described as the fourth dimension, alongside length, width, and height.</p><h2>2. Is time a physical quantity?</h2><p>Yes, time is considered a physical quantity that can be measured and compared. It is often measured in seconds using a clock or other time-keeping devices.</p><h2>3. Can time be manipulated or controlled?</h2><p>While humans have developed ways to measure and track time, it is not possible to manipulate or control time itself. Time is a constant and universal concept that cannot be altered.</p><h2>4. Does time flow at the same rate for everyone?</h2><p>According to Einstein's theory of relativity, time can appear to pass at different rates for different observers depending on their relative speeds and gravitational fields. However, for a specific observer, time always appears to flow at a constant rate.</p><h2>5. What is the relationship between time and space?</h2><p>In physics, time and space are often considered together as a single concept called spacetime. This is because they are closely intertwined and influence each other, such as how gravity can affect the passage of time.</p>

1. What is time?

Time is a fundamental concept in physics that measures the duration and sequence of events. It is often described as the fourth dimension, alongside length, width, and height.

2. Is time a physical quantity?

Yes, time is considered a physical quantity that can be measured and compared. It is often measured in seconds using a clock or other time-keeping devices.

3. Can time be manipulated or controlled?

While humans have developed ways to measure and track time, it is not possible to manipulate or control time itself. Time is a constant and universal concept that cannot be altered.

4. Does time flow at the same rate for everyone?

According to Einstein's theory of relativity, time can appear to pass at different rates for different observers depending on their relative speeds and gravitational fields. However, for a specific observer, time always appears to flow at a constant rate.

5. What is the relationship between time and space?

In physics, time and space are often considered together as a single concept called spacetime. This is because they are closely intertwined and influence each other, such as how gravity can affect the passage of time.

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