what is time ??

[lepton_veecee]

What drives the universe through this thing that is called TIME what exactly is it?? I mean what are we measuring using all these clocks?

[ajb]

This is a metaphysics question and not a physics one.

 

We know how to deal with time in our models and in physics that the important thing.

[herb w.]

Time is process. Events in our universe proceed, such as the spin of the earth on its axis, which marks the day, and time it takes the earth to orbit the sun. And the time it takes Cs atoms to "do their thing" which means a spin change, which is why atomic clocks are so very accurate. Or the watch makers can create a tiny quartz X-tal to vibrate and measure those to keep track of seconds.

 

Time is process. No time is absolute, either. All time is measured relative to a mostly stable, fixed point. Time is related to strength of gravitational fields relative to a greater or lesser field. It's related to velocity relative to a stable, fixed point, too. As an object moves faster relative to the speed of light, time slows down. As gravitational fields get weaker, time speeds up, relatively. A particle in a high gravitational field, would find that time had slowed down, relative to a lower gravitational field. A particle in the high mass density of the nucleus would find itself slowed down, relative to outside the nucleus. Theoretically, if all mass/gravity were removed, time would speed up to instantaneous. That might suggest how the universe was created.

 

On a quantum level, faster than light is not forbidden, which could account for the acausal events of QM. Hawkings stated that is how a black hole evaporates. Photons/particles quantum tunnel out of a Black Hole at FTL. This has not yet been confirmed, but is allowable in QM. Theoretically, if a photon/particle exceeded Cee (light speed), it could go back in time.

 

The interesting thing is, without mass/gravity, there would not be space/time. This might related to cosmology.

[Mordred]

 

On a quantum level, faster than light is not forbidden, which could account for the acausal events of QM. Hawkings stated that is how a black hole evaporates. Photons/particles quantum tunnel out of a Black Hole at FTL. This has not yet been confirmed, but is allowable in QM. Theoretically, if a photon/particle exceeded Cee (light speed), it could go back in time.

 

The interesting thing is, without mass/gravity, there would not be space/time. This might related to cosmology.Hawking radiation occurs outside of the EH, it is not FTL, when hawking radiation is created two entangled particles form, one falls into the BH's event horizon lost forever, one escapes. The negative energy particle that falls into the BH causes a loss of energy and mass.

 

 

This is incorrect Hawking radiation is not FTL. When two entangled particles are created outside the black holes event horizon, the positive particle escapes, the negative energy particle falls into the the BH thus reducing the black holes mass and energy. Hawking radiation occurs outside the event horizon and is part of the accretion disk. For a full technical detail on the accretion disk as well as other forms of radiation that occurs within it. (including the angular momentum effects the accretion disk has on the BH's spin see this lengthy article.

 

http://arxiv.org/abs/1104.5499 :''Black hole Accretion Disk'' -Handy article on accretion disk measurements provides a technical compilation of measurements involving the disk itself.

 

as far as quantum tunneling being faster than the speed of light you might want to read these articles (information does not travel faster than light)

http://arxiv.org/ftp/arxiv/papers/0708/0708.3889.pdf

http://arxiv.org/ftp/quant-ph/papers/0403/0403010.pdf

 

here is a simpler version for those not up on the mathematics

http://sitemaker.umich.edu/herbert.winful/files/nimtz_stahlhofen_faster_than_light_speed.pdf

Edited June 3, 2014 by Mordred

[ajb]

Time is process. Events in our universe proceed, such as the spin of the earth on its axis, which marks the day, and time it takes the earth to orbit the sun. And the time it takes Cs atoms to "do their thing" which means a spin change, which is why atomic clocks are so very accurate. Or the watch makers can create a tiny quartz X-tal to vibrate and measure those to keep track of seconds.

This is how we measure time but it does not tell us what time "is".

 

In the same way I can use a ruler to measure the distance bewteen two points, but that does not tell me what space "is".

Edited June 4, 2014 by ajb

[Kramer]

AJB say:

In the same way I can use a ruler to measure the distance bewteen two points, but that does not tell me what space "is".

------But this is not the same. We don't measure the space with velocity. but with the same kind: ----a peace of space taken arbitrary as unity.
You measure time with what? With repetitive movement take as unity, with "number of vibrations". Both they are not "peace of time. This is an arbitrary concept of time, used to give concept of time magical property.

[studiot]

 

In the same way I can use a ruler to measure the distance bewteen two points, but that does not tell me what space "is".

------But this is not the same. We don't measure the space with velocity. but with the same kind: ----a peace of space taken arbitrary as unity.

You measure time with what? With repetitive movement take as unity, with "number of vibrations". Both they are not "peace of time. This is an arbitrary concept of time, used to give concept of time magical property.

 

 

Yes, it is true that whatever clock ticks measure it is not time and that a ruler directly compares one length with another.

 

But it is also true that neither tells us what space or time are.

 

In fact we cannot measure time itself, only time difference, and that is what the clock tick measures.

 

There are many quantities in Physics that we can only measure by difference, eg voltage.

 

Again in fact the ruler length is a distance difference not a true measure of space either.

One of the few absolute quantities that we can measure is absolute temperature (at least in theory).

 

One further note is that for quantities that we account in either absolute or difference terms such as voltage, time etc, both the absolute and difference measurements are made in the same units.

 

go well

Edited June 4, 2014 by studiot

[lepton_veecee]

there are known reasons for voltage to exist, what is the reason behind time.the method we use to measure a quantity is not a definition,or is it?

[studiot]

 

there are known reasons for voltage to exist, what is the reason behind time.the method we use to measure a quantity is not a definition,or is it?

 

 

I agree, the method of measurement is not a definition.

 

I don't have a complete definition or description but my idea is that there are many phenomena in our observable world that are best modelled or explained by introducing a mathematical variable we call time.

 

I hesitate to suggest this thread about the same subject because it suffered much misdirection but look at my post#62 on page4

 

http://www.scienceforums.net/topic/82939-explanation-of-time/page-4

 

The introduction of a new variable to ease the mathematics has other precedents, for example the introduction of entropy in thermodynamics to pair with temperature on an indicator diagram.

Of course we do not have the same up close and personal relationship with entropy that we have with time but the maths follows a similar path.

Edited June 5, 2014 by studiot

[Kramer]

 

Studiot say:

Yes, it is true that whatever clock ticks measure it is not time and that a ruler directly compares one length with another.

But it is also true that neither tells us what space or time are.

----- Sorry, but I think isn’t the same. When we measure the distance with a ruler (nevertheless the ruler is metallic, wood or whatever,) we use the length of it (distance in the extremes of ruler) as a unity. They are both ”objective reality of the same kind”.
When we say that measure time with the number of clock tics, or the number of water drops, or the position of sun’s shadow etc.--- what have they to do with concept of time?
They give us the evidence of something that is moving, something that is displaced in space, and, indeed, the amount of displacement. What has to do it with flow of time?
If we compare the number of clock’s ticks, with number of miles we made with our car, or with the amount of gallons of gas we have spent etc. this is an subjective comparison that has nothing to do with concept that modern physic gave for time, as an important actor in nature.

In fact we cannot measure time itself, only time difference, and that is what the clock tick measures.

------- Do you mean frequency? The number of repetitive displacement of something in circles ?

There are many quantities in Physics that we can only measure by difference, eg voltage.
----- I think that voltage is an objective reality, an intrinsic property of particles of mater. This mean a real actor in nature, that has nothing to do with human’s concepts as in case of time.

 

 

Again in fact the ruler length is a distance difference not a true measure of space either.-------Distances, of the ruler taken as unity, or of the segment we want to measure, are the most evident objective reality of the same kind -- I think.

One of the few absolute quantities that we can measure is absolute temperature (at least in theory).
-------I think that temperature is too an evasive concept, of something that we measure with different methods, but i don’t know what it is. For example we measure its quantity with dilation of mercury colon, but what is it, I have not idea. The link of temperature with the frequency of electromagnetic waves --after De Vien interpretation, I think gave a method for relation between thermal and electromagnetic form of energy.

 

One further note is that for quantities that we account in either absolute or difference terms such as voltage, time etc, both the absolute and difference measurements are made in the same units.

 

go well

[swansont]

------But this is not the same. We don't measure the space with velocity. but with the same kind: ----a peace of space taken arbitrary as unity.

 

 

A ruler is not a piece of space. A ruler is a physical object.

Studiot say:

 

----- Sorry, but I think isn’t the same. When we measure the distance with a ruler (nevertheless the ruler is metallic, wood or whatever,) we use the length of it (distance in the extremes of ruler) as a unity. They are both ”objective reality of the same kind”.

When we say that measure time with the number of clock tics, or the number of water drops, or the position of sun’s shadow etc.--- what have they to do with concept of time?

 

 

In both cases the measuring device is calibrated to a standard. A ruler has a length, and an oscillation has a duration, or period.

[Sensei]

When we measure the distance with a ruler (nevertheless the ruler is metallic, wood or whatever,) we use the length of it (distance in the extremes of ruler) as a unity. They are both ”objective reality of the same kind”.

 

If your ruler is metallic, when we will be measuring distance at -100 C, 0 C, +100 C, +1000 C its length will be different, as metal shrinks and extends depending on temperature of environment. This effect is used in typical Mercury thermometer.

[studiot]

All distance measurement is by difference.

 

If you have done any serious hermodynamics you will have met the thermodynamic absolute temperature scale which is defined independently of any thermometer, unlike distance, for which we have no absolute unit.

[Kramer]

 

Swanson

A ruler is not a piece of space. A ruler is a physical object.
----- We use the “ruler’s length” as a segment of space to measure another segment of space. Because both segments have the same Euklidian property. In this case we disregard other property that they may posses. The space I think was, is and will be the only home of physical objects.

In both cases the measuring device is calibrated to a standard. A ruler has a length, and an oscillation has a duration, or period.
-----The difference between space and time in this debate is that space we treated as something static. We can’t say this for time.
Time is treated as something evasive mysterious that is always in movement, flowing. As this kind, it must have velocity, even acceleration. Why not?
The modern physic treat time as most important actor in everything: it is culprit about the gray hair on old people, it is all mighty factor in the creation of universe.
I think flow of time is only a human’s concept very helpful for them to compare their activity with movement of earth toward its axis, and toward the sun.
As a human concept it is subjective, it has not any objective role.
The prove are unities of time, used for everyday activity of humans: such as sec, hour, day…
What is 1 day?

After you, it is “a period of time when” a point in equator of earth fulfill 1circle.
Why not after me: 1 day is 1 full circle of earth’s spinning, toward its axis?
You say: S = Vo*t Why not (So / to) * t = So*(t /to) = So*n

I may say: S = (2*pi*R(tire of car))*N Here N number of cycles of tire counted by speedometer.
In this examples faded concept of time.

Sensei
If your ruler is metallic, when we will be measuring distance at -100 C, 0 C, +100 C, +1000 C its length will be different, as metal shrinks and extends depending on temperature of environment. This effect is used in typical Mercury thermometer.
---- Sure this is important for humans especially when ruler is used in business.

Studiot

All distance measurement is by difference.

If you have done any serious hermodynamics you will have met the thermodynamic absolute temperature scale which is defined independently of any thermometer, unlike distance, for which we have no absolute unit.
------ Why not Plank length?

[Mordred]

your argument is based on units of measure, time doesn't care how we measure it or what measuring tool or device we choose to allow us to define the rate of change in a process.

 

time is simply a rate of change of any and all processes, doesn't matter how we measure it (or measure of no change, duration)

Edited June 6, 2014 by Mordred

[swansont]

Swanson

 

A ruler is not a piece of space. A ruler is a physical object.

----- We use the “ruler’s length” as a segment of space to measure another segment of space. Because both segments have the same Euklidian property. In this case we disregard other property that they may posses. The space I think was, is and will be the only home of physical objects.

That doesn't make a ruler a piece, or segment, of space. It's a physical object that we use as a basis for comparison, i.e. a standard.

 

 

In both cases the measuring device is calibrated to a standard. A ruler has a length, and an oscillation has a duration, or period.

-----The difference between space and time in this debate is that space we treated as something static. We can’t say this for time.

Time is treated as something evasive mysterious that is always in movement, flowing. As this kind, it must have velocity, even acceleration. Why not?

That we classically treat time as different from space only serves to acknowledge that they are different things. But any of the measurements are comparisons to a standard. If you want to measure a length of time, you need to have a standard length of time.

 

Calling it "evasive mysterious" is argument from incredulity, so that's something that can be safely ignored. And saying it must have velocity and acceleration is an assertion without substantiation.

 

The modern physic treat time as most important actor in everything: it is culprit about the gray hair on old people, it is all mighty factor in the creation of universe.

I think flow of time is only a human’s concept very helpful for them to compare their activity with movement of earth toward its axis, and toward the sun.

As a human concept it is subjective, it has not any objective role.

It's subjective in the sense that relativity is a real thing, but objective in the sense that we can measure it.

 

But causally-related events happen with ordering. That part is objective.

 

 

The prove are unities of time, used for everyday activity of humans: such as sec, hour, day…

What is 1 day?

After you, it is “a period of time when” a point in equator of earth fulfill 1circle.

Why not after me: 1 day is 1 full circle of earth’s spinning, toward its axis?

You say: S = Vo*t Why not (So / to) * t = So*(t /to) = So*n

I may say: S = (2*pi*R(tire of car))*N Here N number of cycles of tire counted by speedometer.

In this examples faded concept of time.

 

If you can come up with useful definitions or intervals of time, fine. Time is not defined in the specific way it is realized.

[hoola]

I see time having occured within any region that has changed any of the information components within it. Virtual particles give a constant flux that delivers a minimum amount of change, so that determines a base rate minimum of change. A black hole event horizon does not halt this rate, as shown by hawking radiation, so no absolute cessation of time anywhere exterior to the horizon...perhaps the singularity of a BH that is quiescent has has a temporary reduction or suspension of change, as it evaporates and pops at the end of it's lifetime...

Edited June 7, 2014 by hoola

[matterdoc]

I think, time is a functional entity, invented by rational beings to compare interval between two actions with respect to a reference interval (between two actions), which is assumed constant.

Nainan

[Maxila]

What drives the universe through this thing that is called TIME what exactly is it?? I mean what are we measuring using all these clocks?

 

Empirically the answer to that question is as definitive and self-evident as any axiom can be, in the maths of GR and QM the answer is enigmatic. I'll only speak empirically since it is definitive and that may be of some help.

 

In any way it can be directly observed time is a measure of a change of position relative to distance. All clocks including cesium clocks (currently the worlds time standard), use an increment of motion to measure a "period" or "duration" of time. Observation-ally time, and speed or velocity (speed of a vector), are coincident and reciprocal as the measure of a change in position within a distance, i.e. t=x/s as s=x/t, they are two ways to describe the same change within a distance. This may be easiest to see in arguably mans first clock the Earth's rotation. We assign a time value 1 day to a single rotation, that rotation is just an increment of a change in position (one rotation), the same principle used by the most advanced clocks today. When you observe one rotation you see the duration (1 day), with the speed as coincident and reciprocal within the distance changed, at the equator or any latitude. You may also notice the time value (in this case 1 day) is a proportional ratio of x/s where they also equal 1, if you observed two days than the ratio of x/s would be 2/1 at every latitude, etc.

 

I've linked a few references to cesium clocks that might be helpful:

 

 

(Section) 18.2

 

… "Time is kept by observing and counting the frequencies at which electromagnetic energy is emitted or absorbed by the atoms. In essence, the atom serves as a pendulum whose oscillations are counted to mark the passage of time [3]." http://etc.unitbv.ro/~olteanu/Tehnici%20de%20masurare%20in%20tc/18.%20Time%20Measurement.pdf

 

--------------------------------------------------------------------------------

 

"For the ultimate in accuracy, scientists reach for atoms, or more precisely, an exactly known frequency of light emitted by a chosen atom. The 'ticks' are the crests of a light wave,"

http://www.nsf.gov/discoveries/disc_...&preview=false

 

--------------------------------------------------------

 

As with all waves, the radiation has a certain frequency (i.e., it completes a certain number of full waves in a second, similar to the way a pendulum completes a certain number of swings in a minute) and this frequency can be measured

 

The caesium atom defines the SI second. The second is 9 192 631 770 periods of the electromagnetic radiation emitted or absorbed by the ground state hyperfine transition of the caesium atom. This means that a second is the amount of time it takes for the radiation from this transition to complete 9 192 631 770 full waves. http://www.npl.co.uk/educate-explore/what-is-time/how-do-atomic-clocks-work

Edited August 7, 2014 by Maxila

[swansont]

 

Empirically the answer to that question is as definitive and self-evident as any axiom can be, in the maths of GR and QM the answer is enigmatic. I'll only speak empirically since it is definitive and that may be of some help.

 

In any way it can be directly observed time is a measure of a change of position relative to distance. All clocks including cesium clocks (currently the worlds time standard), use an increment of motion to measure a "period" or "duration" of time. Observation-ally time, and speed or velocity (speed of a vector), are coincident and reciprocal as the measure of a change in position within a distance, i.e. t=x/s as s=x/t, they are two ways to describe the same change within a distance. This may be easiest to see in arguably mans first clock the Earth's rotation. We assign a time value 1 day to a single rotation, that rotation is just an increment of a change in position (one rotation), the same principle used by the most advanced clocks today. When you observe one rotation you see the duration (1 day), with the speed as coincident and reciprocal within the distance changed, at the equator or any latitude. You may also notice the time value (in this case 1 day) is a proportional ratio of x/s where they also equal 1, if you observed two days than the ratio of x/s would be 2/1 at every latitude, etc.

 

I've linked a few references to cesium clocks that might be helpful:

 

 

(Section) 18.2

 

… "Time is kept by observing and counting the frequencies at which electromagnetic energy is emitted or absorbed by the atoms. In essence, the atom serves as a pendulum whose oscillations are counted to mark the passage of time [3]." http://etc.unitbv.ro/~olteanu/Tehnici%20de%20masurare%20in%20tc/18.%20Time%20Measurement.pdf

 

--------------------------------------------------------------------------------

 

"For the ultimate in accuracy, scientists reach for atoms, or more precisely, an exactly known frequency of light emitted by a chosen atom. The 'ticks' are the crests of a light wave,"

http://www.nsf.gov/discoveries/disc_...&preview=false

 

--------------------------------------------------------

 

As with all waves, the radiation has a certain frequency (i.e., it completes a certain number of full waves in a second, similar to the way a pendulum completes a certain number of swings in a minute) and this frequency can be measured

 

The caesium atom defines the SI second. The second is 9 192 631 770 periods of the electromagnetic radiation emitted or absorbed by the ground state hyperfine transition of the caesium atom. This means that a second is the amount of time it takes for the radiation from this transition to complete 9 192 631 770 full waves. http://www.npl.co.uk/educate-explore/what-is-time/how-do-atomic-clocks-work

 

There is no increment of motion here. "Pendulum" is used metaphorically; it's a spin-flip of the electron, as it changes levels in the ground hyperfine states. This is QM — a change in state. There is no classical motion involved.

[Maxila]

 

There is no increment of motion here. "Pendulum" is used metaphorically; it's a spin-flip of the electron, as it changes levels in the ground hyperfine states. This is QM — a change in state. There is no classical motion involved.

 

The hyperfine transition is used to tune a frequency to the exact frequency of the photon emitted by the electron when it goes back to its lower energy state. It is the frequency (wavelength over speed) that is used to measure time. The first paper linked by Michael Lombardi is a NIST document, in it he reaffirms all clocks use motion to measure time.

[swansont]

 

The hyperfine transition is used to tune a frequency to the exact frequency of the photon emitted by the electron when it goes back to its lower energy state. It is the frequency (wavelength over speed) that is used to measure time. The first paper linked by Michael Lombardi is a NIST document, in it he reaffirms all clocks use motion to measure time.

 

No, actually, he doesn't. Works written for a general audience aren't going to include the proper technical detail, and will include colloquial expressions that can't be taken literally.

 

What is being measured is change in a QM state, where there is no classical trajectory.

[studiot]

 

Maxila

all clocks use motion to measure time.

 

 

This is an imprecise statement, so would you please clarify the ambiguity in what you actually mean.

 

By comparison take the measurement of length by a ruler.

 

The actual length being measured and the lengths marked on the ruler are static and require no motion in order for these lengths to exist or to offer side by side comparison.

 

So in this sense no motion is required to measure length.

In particular length does not depend upon motion.

 

However in order to place the ruler alongside the measureand, motion of the ruler is required.

 

In order to view the comparison, motion of the observation photons is required.

 

In order to write down the reading on the scale, motion is required of the pen over the paper.

 

In order for a living measurer to make this measurement, she must breath, requiring motion.

 

So please explain at what level you are making this statement with regard to the measurement of time.

 

This should save a great deal of 'He said - She said' argument.

Edited August 10, 2014 by studiot

[harshgoel1975]

my point of view .. we can measure the time duration only as we can measure the length using scale.. the accuracy of measurement depends upon the calibration of measuring instrument... so measurement of time can be perfectly analogous to measurement of length...we have starting point and ending point.. and we measure the difference only....

 

Basic question here is "what is Time".. it puzzled me a lot...it is definitely a dimension and science has still to come-up a long way to full or partial definition for it.

[Strange]

Basic question here is "what is Time".. it puzzled me a lot...it is definitely a dimension and science has still to come-up a long way to full or partial definition for it.

 

You have just defined it.

 

What further definition are you looking for?

Edited August 10, 2014 by Strange