# What does time really mean? (1 Viewer)

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#### Parbat

What does "time" really mean?

What does "time" really mean?
i really don't know that.

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#### ghwellsjr

Gold Member
Re: Time

According to Richard Feynman, Time is what happens when nothing else is happening.

Actually, no one knows how to define time but we all know what it means. So that means you must know what it means. Why do you want to say that you really don't know what time is? You must be referring to some subtle aspect of it, like how can it be going slower for someone moving at a high speed? Is that what you are concerned about?

#### Parbat

Re: Time

i mean,how can we say "time" is a dimension?
& dimension means something that is required to explain any object,is that true?

#### TheAlkemist

Re: Time

Thanks for asking this question Parbat!!

How can time be a dimension? What I was taught in physics:
A dimension is "the least number of COORDINATES required to specify, uniquely, a point in a space."

So is a dimension the same as a coordinate? I thought dimensions were related to ARCHITECTURE, STRUCTURE and ORIENTATION (shape, geometry) and coordinates were used to specify the LOCATION of things.

In 3D space, the dimensions are LENGTH, WIDTH and HEIGHT, pointing outwards from the object. The coordinates are LONGITUDE, LATITUDE and ALTITUDE and they point inwards, towards the object because the specify location. The corresponding VECTORS would be DEPTH, BREADTH and ELEVATION which specify the mutually orthogonal DIRECTIONS the object moves. Dimensions and coordinates are static while vectors are dynamic. The only attributes common to these three concepts are direction and orthogonality which are QUALITATIVE attributes. That's it.

So how does time fit into this? How is time considered a dimension when it's routinely used--by mathematicians, as a NUMBER LINE--to QUANTIFY?

Time is a one-dimensional quantity used to sequence events, to quantify the durations of events and the intervals between them, and (used together with space) to quantify and measure the motions of objects.
http://en.wikipedia.org/wiki/Time

So if time is a QUANTIFIER of a sequence of events, where/how does the QUALITATIVE attribute of directionality orthogonality come in here? Or is this merely an attribute that mathematicians (or Einstein) added to create a model/manifold for doing the math? (Minkowski Space-time?)

I don't get it. In science, don't we have to be objective and consistent with the terms (verbs, nouns, adverbs, adjectives) we use as per their definitions? Is't this required to maintain coherence and eliminate the ambiguity often encountered when metaphors are used? Isn't this what distinguishes science from other subjective forms of inquiry (like religion)?

I appologize for the lengthiness/dimension of this post. :tongue:

#### bcrowell

Staff Emeritus
Gold Member
Re: Time

i mean,how can we say "time" is a dimension?
& dimension means something that is required to explain any object,is that true?
I don't understand what it would mean to explain an object.

In relativity, we have four coordinates that are used in order to specify an event. It doesn't make sense in relativity to treat a time coordinate differently from a spatial coordinate, because when one observer is in motion relative to another observer, each observer's measurements of time and distance are related to the other observer's measurements by equations that don't break apart cleanly into time and space equations.

#### ghwellsjr

Gold Member
Thanks for asking this question Parbat!!

How can time be a dimension? What I was taught in physics:
A dimension is "the least number of COORDINATES required to specify, uniquely, a point in a space."

So is a dimension the same as a coordinate? I thought dimensions were related to ARCHITECTURE, STRUCTURE and ORIENTATION (shape, geometry) and coordinates were used to specify the LOCATION of things.

In 3D space, the dimensions are LENGTH, WIDTH and HEIGHT, pointing outwards from the object. The coordinates are LONGITUDE, LATITUDE and ALTITUDE and they point inwards, towards the object because the specify location. The corresponding VECTORS would be DEPTH, BREADTH and ELEVATION which specify the mutually orthogonal DIRECTIONS the object moves. Dimensions and coordinates are static while vectors are dynamic. The only attributes common to these three concepts are direction and orthogonality which are QUALITATIVE attributes. That's it.

So how does time fit into this? How is time considered a dimension when it's routinely used--by mathematicians, as a NUMBER LINE--to QUANTIFY?

Time is a one-dimensional quantity used to sequence events, to quantify the durations of events and the intervals between them, and (used together with space) to quantify and measure the motions of objects.
http://en.wikipedia.org/wiki/Time

So if time is a QUANTIFIER of a sequence of events, where/how does the QUALITATIVE attribute of directionality orthogonality come in here? Or is this merely an attribute that mathematicians (or Einstein) added to create a model/manifold for doing the math? (Minkowski Space-time?)

I don't get it. In science, don't we have to be objective and consistent with the terms (verbs, nouns, adverbs, adjectives) we use as per their definitions? Is't this required to maintain coherence and eliminate the ambiguity often encountered when metaphors are used? Isn't this what distinguishes science from other subjective forms of inquiry (like religion)?

I appologize for the lengthiness/dimension of this post. :tongue:
Everything you have said is excellent, but you stopped too soon. You should also have said that your choice of co-ordinate system should not make any difference in how you analyze a situation, don't you agree?

Well, that's the problem. When we try to define the distance between to events, widely separated in distance and time, we will get different answers for every co-ordinate system we use and that's no fun.

So to solve this problem we use a new kind of vector that includes both the normal three-component vector for space and the normal scalar for time, and we call it a four-vector. Then we invent (or discover) a way to calculate a new "distance" called "interval" that is always the same, no matter which co-ordinate system we use to describe, characterize, or analyze any situation.

Does that make sense to you?

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#### Time Machine

Re: Time

So if time is a QUANTIFIER of a sequence of events, where/how does the QUALITATIVE attribute of directionality orthogonality come in here? Or is this merely an attribute that mathematicians (or Einstein) added to create a model/manifold for doing the math? (Minkowski Space-time?)

I don't get it. In science, don't we have to be objective and consistent with the terms (verbs, nouns, adverbs, adjectives) we use as per their definitions? Is't this required to maintain coherence and eliminate the ambiguity often encountered when metaphors are used? Isn't this what distinguishes science from other subjective forms of inquiry (like religion)?
I'm not much keen on time as a dimension either. As time dilation is now being proved reactive to gravity, could time be thought of as a force? Perhaps "force" is the wrong termanology but "energy" doesn't quite cut it.

#### TheAlkemist

Re: Time

Everything you have said is excellent, but you stopped to soon. You should also have said that your choice of co-ordinate system should not make any difference in how you analyze a situation, don't you agree?
What do you mean by "analyze a situation"? I'm going to assume that you mean how you describe an event occurring between (at least) two objects?

To analyze = qualify and quantify.

The coordinate system specifies the locations of the objects.
The dimension system specifies the shapes of the objects.
The vector system specifies the motion of the objects.
Coordinates and dimensions and vectors are all concepts used to qualify the situation. At this point, yes, it should make no difference how you analyze the situation if you stay consistent with these systems.

However...in order to quantify the situation we invented another abstract concept called numbers. Specifically number lines. And herein lies the mysterious merger of quantifying and qualifying concepts--numbers (quantifier) and lines (geometric qualifier) respectively. At which point numbers (with magnitude) have now inherited directionality. Vectors inherit magnitude, time inherits directionality.

Well, that's the problem. When we try to define the distance between to events, widely separated in distance and time, we will get different answers for every co-ordinate system we use and that's no fun.
Why? If you don't muddle qualifiers and quantifiers there shouldn't be a problem. You should be able to objectively qualitatively define the distance between 2 objects in space by the relationship between their coordinates AND further define that distance relationship using a quantifying concept. My issue is in the packaging. When you start assigning attributes like directionality to abstract concepts like time. It's like talking about the direction of love, anger, or the color blue. these are all concepts which only have meaning in the context of the relationship between at least two objects. Eg., anger vs sadness, love vs hate, red vs blue, etc

This is not a trivial issue of semantics. When we use words in science, we must use them consistently as an objective criterion.

So to solve this problem we use a new kind of vector that includes both the normal three-component vector for space and the normal scalar for time, and we call it a four-vector. Then we invent (or discover) a way to calculate a new "distance" called "interval" that is always the same, no matter which co-ordinate system we use to describe, characterize, or analyze any situation.

Does that make sense to you?
No. Sound like convenient mathematical magic to me. "Abra-kadabra!"... now a scalar is a vector!
Not saying it's useless, it just makes no real life physical sense.

#### TheAlkemist

Re: Time

another thing. LENGTH and DISTANCE are NOT synonymous. At least not in science.

LENGTH = used to qualify SHAPE of (one) object
DISTANCE = used to qualify the relationship between (two) objects

There's a QUALITATIVE difference.

People often use these terms interchangeably. They talk about the length of time and concepts like 'time dilation'. What does this mean? You can only distort the SHAPE of an OBJECT. So is time an object?

Again, if these are only metaphors then how can this "science" objective? These circular definitions just introduce avenues for all kinds of circular arguments. What good science shouldn't allow.

#### Time Machine

Re: Time

People often use these terms interchangeably. They talk about the length of time and concepts like 'time dilation'. What does this mean? You can only distort the SHAPE of an OBJECT. So is time an object?

Again, if these are only metaphors then how can this "science" objective? These circular definitions just introduce avenues for all kinds of circular arguments. What good science shouldn't allow.
I could be very much mistaken, but you can distort the shape of a force.
Does this mean time is a force?
Please excuse me if I am way off here. I do get your circular arguments comment, but isn't that how new concepts are born?

#### ghwellsjr

Gold Member
Why? If you don't muddle qualifiers and quantifiers there shouldn't be a problem. You should be able to objectively qualitatively define the distance between 2 objects in space by the relationship between their coordinates AND further define that distance relationship using a quantifying concept. My issue is in the packaging. When you start assigning attributes like directionality to abstract concepts like time.
I agree with you, there shouldn't be a problem, but unfortunately, Mother Nature doesn't agree with us and, so, we lose. It does make a difference which co-ordinate system we use and there is no way for us to determine which one is the correct one, so that is why we use the four-vector interval.

Time is placed orthogonal to the three components of space in the "imaginary" direction and it works and that is why we do it. If you don't like it you need to come up with another scheme that works but you can't stick to the one you have because it doesn't work.

#### phyti

Re: Time

The coordinate system specifies the locations of the objects.
The dimension system specifies the shapes of the objects.
The vector system specifies the motion of the objects.
Coordinates and dimensions and vectors are all concepts used to qualify the situation. At this point, yes, it should make no difference how you analyze the situation if you stay consistent with these systems.

However...in order to quantify the situation we invented another abstract concept called numbers. Specifically number lines. And herein lies the mysterious merger of quantifying and qualifying concepts--numbers (quantifier) and lines (geometric qualifier) respectively. At which point numbers (with magnitude) have now inherited directionality. Vectors inherit magnitude, time inherits directionality.
-Your descriptions are confusing and overly complicated.
Numbers were/are used for expressing magnitudes, and have been for all of human history. Distances were/are expressed informally as magnitudes with a direction, and formally as vectors. There is no difference between coordinates and dimensions, they are both spatial intervals. The length of an object is the difference between the coordinates of the ends of the object.
Why? If you don't muddle qualifiers and quantifiers there shouldn't be a problem. You should be able to objectively qualitatively define the distance between 2 objects in space by the relationship between their coordinates AND further define that distance relationship using a quantifying concept. My issue is in the packaging. When you start assigning attributes like directionality to abstract concepts like time. It's like talking about the direction of love, anger, or the color blue. these are all concepts which only have meaning in the context of the relationship between at least two objects. Eg., anger vs sadness, love vs hate, red vs blue, etc
-Time is a scalar (number/magnitude) and thus has no direction. The time variable was mathematically manipulated for the purpose of treating it as another dimension.
This is not a trivial issue of semantics. When we use words in science, we must use them consistently as an objective criterion.

No. Sound like convenient mathematical magic to me. "Abra-kadabra!"... now a scalar is a vector!
Not saying it's useless, it just makes no real life physical sense.
-A vector/tensor/matrix can contain any number of mixed type of values/attributes, as long as the values are manipulated in a consistent manner. Eg. A personal 'vector' (name, height, weight, eye color, etc...), useful in an employee database.
post#9:
People often use these terms interchangeably. They talk about the length of time and concepts like 'time dilation'. What does this mean? You can only distort the SHAPE of an OBJECT. So is time an object?
-Processes, mechanical, chemical, etc. are mediated by light. Light speed is constant in space and independent of its origin. When objects such as clocks move, the associated processes slow down. The clock slices time into longer intervals, therefore the clock readings are relative for the observer moving with the clock.
Again, if these are only metaphors then how can this "science" objective? These circular definitions just introduce avenues for all kinds of circular arguments. What good science shouldn't allow.
-Science can only measure real world processes, create conceptual models that mimic reality, and keep the ones that are successful. The concepts science uses are all ideal metaphors, just as images are not the objects in the image. We experience the world indirectly.
[/QUOTE]

#### TheAlkemist

Re: Time

I could be very much mistaken, but you can distort the shape of a force.
Does this mean time is a force?
Please excuse me if I am way off here. I do get your circular arguments comment, but isn't that how new concepts are born?
How can you distort a force? A force has no shape and isn't physical object. You can only distort physical objects that have shape. If you're talking about distorting the vector (or tensor) that describes a force then that's a figurative statement. Just like the statement; "spreading love".
I'm not saying the concept of force is useless of meaningless because it's not!

New concepts should be born from scientific methodology so that the language used to describe them is as objective as possible. For example the concept, viscosity. Viscosity describes how forces change the dimensions of a fluid using corresponding vectors. You never hear people talking about "distorting" the viscosity of a fluid. You distort the shape of the fluid by changing the dimensions that describe its state.
This makes more sense to me.

I agree with you, there shouldn't be a problem, but unfortunately, Mother Nature doesn't agree with us and, so, we lose. It does make a difference which co-ordinate system we use and there is no way for us to determine which one is the correct one, so that is why we use the four-vector interval.

Time is placed orthogonal to the three components of space in the "imaginary" direction and it works and that is why we do it. If you don't like it you need to come up with another scheme that works but you can't stick to the one you have because it doesn't work.
If it works so good why is gravity a problem? Why aren't the SM and GR compatible? Does this have anything to do with the mathematical formulations of these models? Just asking. Thanks.

#### TheAlkemist

Re: Time

-Your descriptions are confusing and overly complicated.
Numbers were/are used for expressing magnitudes, and have been for all of human history. Distances were/are expressed informally as magnitudes with a direction, and formally as vectors.
Actually they are very simple and objective. I never said that numbers were not used to express magnitudes. They are and very useful at that. But, how can you use an informal definition on the one hand and then incorporate it into a formal definition on the other and hope to maintain consistency when trying to describe things objectively? When you rely on circular definitions and assume synonyms doesn't this confuse things? I thought math was about formal objective descriptions? I know science is supposed to be. Just because this is how people have been doing it since history doesn't make it correct.

Distance and length are NOT synonymous. There is a non-trivial,
qualitative difference between length and distance. Length is used to describe the shape of a continuous object. Distance is used to describe the space between 2 indivisible objects. Look up the definition of distance in any standard English dictionary and that's the definition you'll get; the space between two things.

The length of an object is the difference between the coordinates of the ends of the object.
Do you agree that an object is made up of discrete atoms/particles separated by (a very very considerable amount of) space? I think most of the physics community does. If so, then which coordinates of what particle are you measuring from to determine the length of the object?

There is no difference between coordinates and dimensions, they are both spatial intervals.
I disagree. Coordinates describe location/position. Dimensions describe shape/structure. Above you said that length is the difference between coordinates of the ends. If you're now saying coordinates = dimensions then you're saying length is the difference between the dimensions of the ends. This makes absolutely NO sense. How is a dimension a "spatial interval"?
See what I mean.

-Time is a scalar (number/magnitude) and thus has no direction. The time variable was mathematically manipulated for the purpose of treating it as another dimension.
Could I well it magic then? Because this mathematical manipulation has created a physical thing from concept. A number changes to an object. Only objects have direction. I'm not being facetious.

-A vector/tensor/matrix can contain any number of mixed type of values/attributes, as long as the values are manipulated in a consistent manner. Eg. A personal 'vector' (name, height, weight, eye color, etc...), useful in an employee database.
Fair enough. How consistently and objectively do you think your so-called personality vector can be applied? I have strong doubts that it can. But I have a few computer science buddies working on AI that would be earger to know.

-Processes, mechanical, chemical, etc. are mediated by light. Light speed is constant in space and independent of its origin. When objects such as clocks move, the associated processes slow down. The clock slices time into longer intervals, therefore the clock readings are relative for the observer moving with the clock.
The clock slices time? Since you can only slice through a continuous object, then are you suggesting that time is a continuous? But yoou say time is a dimension and you said above that dimensions are spatial intervals. So are you slicing through the intervals? I'm confused.

-Science can only measure real world processes, create conceptual models that mimic reality, and keep the ones that are successful. The concepts science uses are all ideal metaphors, just as images are not the objects in the image.
Fair enough. I have no issue with metaphors. We can't avoid them as they're pervasive in everyday life. It's the consistency and potential for ambiguity and circular arguments that I have issue with. And by what criteria do you measure success?

I'll leave it here because I don't think this is the appropriate forum for the direction this might be heading.

#### DaveC426913

Gold Member
Re: Time

There are space-like dimensions and time-like dimensions. They are not the same, but they are all part of our 4-dimensional spacetime.

#### Passionflower

Re: Time

What does "time" really mean?
i really don't know that.
In special and general relativity time for an observer is simply the length between two events that cross his worldline, this length is physically measured by a clock. O more generally it is the calculated length between two events with a timelike distance between them over an arbitrary path

#### phyti

Re: Time

Actually they are very simple and objective. I never said that numbers were not used to express magnitudes. They are and very useful at that. But, how can you use an informal definition on the one hand and then incorporate it into a formal definition on the other and hope to maintain consistency when trying to describe things objectively? When you rely on circular definitions and assume synonyms doesn't this confuse things? I thought math was about formal objective descriptions? I know science is supposed to be. Just because this is how people have been doing it since history doesn't make it correct.
-The reference to informal use is to emphasize that a rigid definition is not needed for practical applications. Travel directions can be very general, eg., 10 miles down route 7 just past Wal-Mart. Scientific study obviously requires more rigid definitions with minimum ambiguity. My reply to the op's question about the meaning of time... it depends on the context. So it goes with definitions, it depends on the purpose.
Here's part of a paper on knowledge which mentions your concern about circular reasoning.

To form knowledge the mind;
--perceives reality,
--forms concepts to model reality,
--predicts reality from these concepts,
--keeps the concepts as knowledge when prediction matches reality.
--modifies the concepts after more perception

knowledge is a set of concepts used as a reference for understanding
By definition knowledge is always incomplete because all reality is never perceived.
For simplicity, a concept is defined within a context that excludes other concepts.
--Other concepts may not be relevant to the purpose.
--There may be relevant concepts that have not been created.
--An approximate definition may be sufficient for the purpose.
Definition is a relative referencing process.
--A definition is expressed in terms of other definitions.
--This process can be circular or incomplete.
Forming knowledge is a continuous process of refinement.
Knowledge is only as good as its definition.

#### phyti

Re: Time

Distance and length are NOT synonymous. There is a non-trivial,
qualitative difference between length and distance. Length is used to describe the shape of a continuous object. Distance is used to describe the space between 2 indivisible objects. Look up the definition of distance in any standard English dictionary and that's the definition you'll get; the space between two things.

Do you agree that an object is made up of discrete atoms/particles separated by (a very very considerable amount of) space? I think most of the physics community does. If so, then which coordinates of what particle are you measuring from to determine the length of the object?

I disagree. Coordinates describe location/position. Dimensions describe shape/structure. Above you said that length is the difference between coordinates of the ends. If you're now saying coordinates = dimensions then you're saying length is the difference between the dimensions of the ends. This makes absolutely NO sense. How is a dimension a "spatial interval"?
See what I mean.
Chemistry and quantum theory demonstrate that matter is discrete, 2 yeses.

Coordinates are measured from a common origin (by definition).
Three dimensions are sufficient for simple rectangular solids.
1. Place a ruler with the 'o' mark at one end and read the value 10 where the other end contacts the ruler. The length is 10-0=10.
2. Place the ruler with the '4' mark at one end and read the value 14 where the other end contacts the ruler. The length is 14-4=10.
The only difference is where you designate the origin. You are still measuring space.
If 3 4" widgets are end to end, we have 12" of widgets. If the middle one is removed, there is still 4" of space between the other 2, whether it's occupied or not!

#### TheAlkemist

Re: Time

-The reference to informal use is to emphasize that a rigid definition is not needed for practical applications. Travel directions can be very general, eg., 10 miles down route 7 just past Wal-Mart. Scientific study obviously requires more rigid definitions with minimum ambiguity. My reply to the op's question about the meaning of time... it depends on the context. So it goes with definitions, it depends on the purpose.
Here's part of a paper on knowledge which mentions your concern about circular reasoning.

To form knowledge the mind;
--perceives reality,
--forms concepts to model reality,
--predicts reality from these concepts,
--keeps the concepts as knowledge when prediction matches reality.
--modifies the concepts after more perception

knowledge is a set of concepts used as a reference for understanding
By definition knowledge is always incomplete because all reality is never perceived.
For simplicity, a concept is defined within a context that excludes other concepts.
--Other concepts may not be relevant to the purpose.
--There may be relevant concepts that have not been created.
--An approximate definition may be sufficient for the purpose.
Definition is a relative referencing process.
--A definition is expressed in terms of other definitions.
--This process can be circular or incomplete.
Forming knowledge is a continuous process of refinement.
Knowledge is only as good as its definition.
I agree with the general gist of what you've said, except the red highlighted. In science, I think it's even more important to be as objective as possible in practical situations.

For example, how does one consistently communicate the concept of a 'time-line' when people have different definitions of what a line is. Is a line, by one definition, a series of points? Or is it, by another definition, the empty space between 2 points? Or a continuous extended rectangle? Do you see how either one of these definitions has a very significant and non-trivial consequence on the meaning of a 'time-line'?

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