Define time

[entwined]

How do we know that time exists?

 

As far as I know, it has no physical properties, no weight, no width, length or depth, yet we seem to think we can measure it and some even think we can alter it, so how would you define time?

[ecoli]

time is a deminsion of the universe, inseparable with space.

[the tree]

Ditto. It's just another dimension.

[entwined]

Then it should be quite easy to define.

 

So..........

 

 

Exactly what is time?

[ecoli]

Then it should be quite easy to define.

 

What makes you think that? Time is a property of the universe just like 3 demensional space. But is the word "space" any easier to define? What about other demensions like "hypercubes'...that's just as hard to define.

[ffsjoe]

There have been numerous threads on this subject. Ill let you in on a secrect, there is a tool, its known as the search function you should take it for a whirl sometime.

 

Here is a couple you can take a gander at.

 

http://www.scienceforums.net/forums/showthread.php?t=12783&highlight=time

 

http://www.scienceforums.net/forums/showthread.php?t=14589&highlight=time

[entwined]

There have been numerous threads on this subject. Ill let you in on a secrect' date=' there is a tool, its known as the search function you should take it for a whirl sometime.

[/quote']

 

I am sincerely sorry if I caused you any inconvenience.......

[Shadowness]

hehe^^

[GORDON HERMA]

get 2 clocks one the size of a thumbtack and another the size of a planet both ticking at the same speed in relation to themselves. One on a spaceship moveing close to the speed of light and one on a skateboard...easiest way i can see it..hope it helps

[patcalhoun]

How do we know that time exists?

 

The same way we know width, length and depth exist.

[Dr. Zimski]

How do we know that time exists?

 

As far as I know' date=' it has no physical properties, no weight, no width, length or depth, yet we seem to think we can measure it and some even think we can alter it, so how would you define time?[/quote']

Count from 1 to 5. Congatulations! You just measured time! But the answer isn't that simple.

 

Time, like speed, mass, location, and distance, is relative. I'm afraid I can't explain further though, sorry.

[entwined]

So far I have not seen anything in the way of a definition, only evidence that we perceive it to exist.

[gcol]

So far I have not seen anything in the way of a definition, only evidence that we perceive it to exist.

 

You have called their bluff. I dont think a generally accepted one exists, But here's one that suits me:

 

Time is an artificial mathematical construct that is convenient to measure the passage of events.

 

Any dissenters? More suggestions?

 

Many bedrock modern theories make assumptions as to the basic nature of time...... er, did I just suggest some bedrock theories are founded based on the quicksand of unfounded assumption? Oh well, have fun and shoot me down in flames.

[GORDON HERMA]

So far I have not seen anything in the way of a definition, only evidence that we perceive it to exist.

 

 

In my last post i posted

get 2 clocks one the size of a thumbtack and another the size of a planet both ticking at the same speed in relation to themselves. One on a spaceship moveing close to the speed of light and one on a skateboard...easiest way i can see it..hope it helps

I didnt do a very good explanation of why so ill give it a shot.

 

First both clocks are not conscious, they dont perceive anything, nor does an atom,thunderstorm,popcicle,ect. If you want to put your mind around time imagine you are standing next to a clock the size of a planet. With every tick you hear a thunderous boom. Each tick takes like 5 mins because of its "SIZE IN SPACE". Between ticks you look down at your feet and there is a clock ticking 60 times per minute that has the "SIZE IN SPACE" of the tip of you thumb. Now both these clocks are identical and equal in every way except the fact that they are different sizes.

If we put the thumbtack clock into a spaceship and get it moveing faster and faster towards the speed of light then the ticks of that clock become larger with each increase of speed. Eventuall, if you have A fast enough "MOTION IN SPACE" the ticks will match that of the planet size clock, ticking every 5 minutes with a thuderous boom.

These 2 properties are the relationship between TIME and SPACE. They are unseperable. The more space(SIZE) that is used in a clock the slower the relative ticks become. The faster the "MOTION" of a clock in space, the slower the relative ticks become. This has nothing to do with precpetion because if you could set up the experiment and walk away it would still happen.

However in our perception, we do portion these properties into scales so that we can reference "WHERE" and "HOW BIG" all our differnt clocks were previously, are currently, and where they are going in "SPACE/TIME".

In conclusion, both clocks being equal with size not withstanding, the only 2 varients are "SIZE AND MOTION". These are properties of "SPACE" and "TIME" and can only exist together as one.

 

Hope this helps some...

Gordon Herman....

[entwined]

In my last post i posted

I didnt do a very good explanation of why so ill give it a shot.

 

First both clocks are not conscious' date=' they dont perceive anything, nor does an atom,thunderstorm,popcicle,ect. If you want to put your mind around time imagine you are standing next to a clock the size of a planet. With every tick you hear a thunderous boom. Each tick takes like 5 mins because of its "SIZE IN SPACE". Between ticks you look down at your feet and there is a clock ticking 60 times per minute that has the "SIZE IN SPACE" of the tip of you thumb. Now both these clocks are identical and equal in every way except the fact that they are different sizes.

If we put the thumbtack clock into a spaceship and get it moveing faster and faster towards the speed of light then the ticks of that clock become larger with each increase of speed. Eventuall, if you have A fast enough "MOTION IN SPACE" the ticks will match that of the planet size clock, ticking every 5 minutes with a thuderous boom.

These 2 properties are the relationship between TIME and SPACE. They are unseperable. The more space(SIZE) that is used in a clock the slower the relative ticks become. The faster the "MOTION" of a clock in space, the slower the relative ticks become. This has nothing to do with precpetion because if you could set up the experiment and walk away it would still happen.

However in our perception, we do portion these properties into scales so that we can reference "WHERE" and "HOW BIG" all our differnt clocks were previously, are currently, and where they are going in "SPACE/TIME".

In conclusion, both clocks being equal with size not withstanding, the only 2 varients are "SIZE AND MOTION". These are properties of "SPACE" and "TIME" and can only exist together as one.

 

Hope this helps some...

Gordon Herman....[/quote']

 

Well it doesn't.

 

what you have discribed are two devices designed to measure time and the relative difference in their "tick rates" when one is moving faster than the other.

 

What I am looking for is a definition of time.

 

Does it exist everywhere? Did it always exist? Are there any other physical laws that affect it? is it detectable from afar? Is it like space, whereas, I am told, if no matter exists to be separated by space, then no space exists?

 

Just a definition, that's all,

[gcol]

Entwined: "What I am looking for is a definition of time........Just a definition, that's all".

 

A heartfelt plea. After much Googling and dictionary searching, I have found only one that seems to have a specific scientific meaning (as apart from, for example, a legal meaning).

It is this:

 

"The scientific definition of time is that period occupied by a body in passing from one given point in space to another, and therefore, according to this definition, when there is no space, there can be no time....

 

Judge Thomas Troward, Edinburgh Lectures, 1909.

 

Or perhaps in street cred argot: "ain't no happening, ain't no time, tha'sall".

 

It will do for me until something better comes along, and I think it may be proveable. If anyone finds a time-based theory that uses something different, try questioning it using that definition and have fun.

[GORDON HERMA]

a body in passing from one given point in space to another, and therefore, according to this definition, when there is no space, there can be no time....

thats what i was trying to say

In conclusion, both clocks being equal with size not withstanding, the only 2 varients are "SIZE AND MOTION". These are properties of "SPACE" and "TIME" and can only exist together as one.

 

Some people mistake time as a progression that we make up to portion it for our understanding. Time itself is dependent upon space and motion, we make it linear and non linear, we decide what a second is by creating progression, but we can not create the properties of physics associated with motion through space.

Gordon...

[patcalhoun]

So far I have not seen anything in the way of a definition, only evidence that we perceive it to exist.

 

You've seen plenty of definition. Time is a dimension, one parameter among many used to specify locations of events in some sort of spacetime. If you need a deeper explanation, then you've stepped into the domain of philosophy and definitely out of the realm of physics

[zorro]

Time is the measure of the rotation of the earth so that it casts its shadow precisely North at noon when the earth makes exactly one revolution around the Sun. It is thus corrected by the orbit adding one rotation and the kind-of Kepler elliptical orbit of the earth. This becomes one year of 365.25 days which is divided to a day, then a minute, then a second and so on.

The notion that this time stretches, and bends is a theoretical relativity notion.

Edited March 2, 2012 by zorro

[D H]

Time is the measure of the rotation of the earth so that it casts its shadow precisely North at noon when the earth makes exactly one revolution around the Sun. It is thus corrected by the orbit adding one rotation and the kind-of Kepler elliptical orbit of the earth. This becomes one year of 365.25 days which is divided to a day, then a minute, then a second and so on.

 

The notion that this time stretches, and bends is a theoretical relativity notion.

There are a number of things wrong with your post.

 

First off, this thread was dead for more than six years. Let old threads die a graceful death. Don't necromance them back to life!

 

Secondly, there's that silly font and color business. Don't do that. It is almost always best to tust go with the defaults.

 

Thirdly, there's the technical content.

Time is the measure of the rotation of the earth

Not since 1956. any more. See below.

 

so that it casts its shadow precisely North at noon

Not since 1656, when Christiaan Huygens invented the pendulum clock. See below.

 

when the earth makes exactly one revolution around the Sun.

That's called a year, not a day.

 

It is thus corrected by the orbit adding one rotation and the kind-of Kepler elliptical orbit of the earth.

This makes no sense.

 

This becomes one year of 365.25 days which is divided to a day, then a minute, then a second and so on.

Not since 1582, when the Julian calendar was replaced by the Gregorian calendar.

 

 

Humans have developed three basic techniques for measuring time: Sundials, the motions of the planets, and mechanical devices. Sundials are the oldest and also the worst of these techniques. Sundials measure what is called apparent solar time. Apparent solar time varies markedly over the course of a year and also varies with latitude. A solar day on February 11 is considerably shorter(half an hour shorter!) than a solar day on November 3, and the length of a apparent solar day today for you probably is not the length of a solar day for me. This discrepancy is called the equation of time. Sundials are a rather lousy timing device.

 

People began moving away from time as measured by a sundial to time as measured by a mechanical device (i.e., a clock) as soon as good clocks were widely available. Although the equation of time was known to the ancients, it was more or less a scientific curiosity until Huygen's invention of the pendulum clock. Those mechanical clocks measure what is called mean solar time. Mean solar time stays in synch with apparent solar time on average, but removes that 30+ minute variation from February 11 to November 3. Even after removing these huge swings, there's yet another problem with time based on the Earth's daily rotation: A day now is about 2 milliseconds longer than a day in 1800. The international standards committee switched from time based on the Earth's daily rotation in the 1950s to time based on the Earth's yearly orbit, and then in the 1960s switched again to using atomic clocks (a quantum mechanical device).

 

The motions of the planets provides yet another way to measure time. Measuring time was the obvious solution to solving the longitude problem. The problem was how to measure time. The issue of clocks versus celestial observations until recently was not fully resolved. A problem with clocks on the Earth is that they vary by a slight amount as the Earth moves from perihelion to aphelion and back again. The best approach is to combine the concepts of clocks and celestial observations, and this is exactly what the various organizations that model the motions of the planets do.

[swansont]

Basically what D H said, in perhaps a little more detail:

 

http://blogs.scienceforums.net/swansont/archives/11054

http://blogs.scienceforums.net/swansont/archives/11058

 

We haven't used the notion that the sun is overhead at noon for quite some time. We went with a standard interval of time instead, trying to make each day nominally the same length, until we stopped using earth rotation as a guide.

[zorro]

There are a number of things wrong with your post.

 

First off, this thread was dead for more than six years. Let old threads die a graceful death. Don't necromance them back to life!

 

Secondly, there's that silly font and color business. Don't do that. It is almost always best to tust go with the defaults.

 

My font is to help you distinguish your stuff from mine. It is very close to black. What is the problem.

 

Thirdly, there's the technical content.

 

I speak to the kinda-eliptical Orbit of the earth. This simple Astrodynamics 101.

 

Not since 1956. any more. See below.

 

???

 

Not since 1656, when Christiaan Huygens invented the pendulum clock. See below.

 

???

 

That's called a year, not a day.

 

Maybe so. I trust yuo to clarify mistake, I can't see it here anyway.

 

This makes no sense.

 

Not since 1582, when the Julian calendar was replaced by the Gregorian calendar.

 

The calendars were off much of the centuries and had to be adjusted at the end of the year.

 

Humans have developed three basic techniques for measuring time: Sundials, the motions of the planets, and mechanical devices. Sundials are the oldest and also the worst of these techniques. Sundials measure what is called apparent solar time. Apparent solar time varies markedly over the course of a year and also varies with latitude. A solar day on February 11 is considerably shorter(half an hour shorter!) than a solar day on November 3, and the length of a apparent solar day today for you probably is not the length of a solar day for me. This discrepancy is called the equation of time. Sundials are a rather lousy timing device.

 

No No. the Harrison chronometer Grandfather clock, telephone, Computer GPS ... and all have to be adjusted as I present above. Sundials are off as the gnomon goes thru it's figure 8. except at beginning of the year.

 

People began moving away from time as measured by a sundial to time as measured by a mechanical device (i.e., a clock) as soon as good clocks were widely available. Although the equation of time was known to the ancients, it was more or less a scientific curiosity until Huygen's invention of the pendulum clock. Those mechanical clocks measure what is called mean solar time. Mean solar time stays in synch with apparent solar time on average, but removes that 30+ minute variation from February 11 to November 3. Even after removing these huge swings, there's yet another problem with time based on the Earth's daily rotation: A day now is about 2 milliseconds longer than a day in 1800. The international standards committee switched from time based on the Earth's daily rotation in the 1950s to time based on the Earth's yearly orbit, and then in the 1960s switched again to using atomic clocks (a quantum mechanical device).

 

Yes, and the must all be adjusted to the earth and not the earth to the time piece.

 

The motions of the planets provides yet another way to measure time. Measuring time was the obvious solution to solving the longitude problem. The problem was how to measure time. The issue of clocks versus celestial observations until recently was not fully resolved. A problem with clocks on the Earth is that they vary by a slight amount as the Earth moves from perihelion to aphelion and back again. The best approach is to combine the concepts of clocks and celestial observations, and this is exactly what the various organizations that model the motions of the planets do.

 

Yes because Harrison's chronometer's time had to be corrected because the earth goes at different speeds in its kinda- elliptic orbit.

 

I don't see it to be closed. but if it is, it is dead as is this conversation.

 

Basically what D H said, in perhaps a little more detail:

 

http://blogs.science.../archives/11054

http://blogs.science.../archives/11058

 

We haven't used the notion that the sun is overhead at noon for quite some time. We went with a standard interval of time instead, trying to make each day nominally the same length, until we stopped using earth rotation as a guide.

 

 

 

Is this thread closed ?????

 

zorro

Edited March 2, 2012 by Cap'n Refsmmat
fix formatting

[D H]

My font is to help you distinguish your stuff from mine. It is very close to black. What is the problem.

 

The problem is that

- You put words in my mouth. Some of what that which is attributed to me in post #22 are not my words.

- You make it nigh impossible to respond to what you wrote.

 

Do not embed your responses inside the quote tags!

 

 

Update

I speak to the kinda-eliptical Orbit of the earth. This simple Astrodynamics 101.

 

No No. the Harrison chronometer Grandfather clock, telephone, Computer GPS ... and all have to be adjusted as I present above.

You were right with the double negative. The Harrison chronometer, grandfather clock, telephone, Computer GPS -- none of them are adjusted as you "described above." (And other than an allusion to "simple Astrodynamics 101", you didn't describe anything.)

 

So, Modern Timekeeping 101.

 

The standard reference for all other times is International Atomic Time (TAI, for Temps Atomique International). This is an average of the time as measured by several atomic clocks around the world. The individual clocks are adjusted for their calculated tick rate and then averaged. The adjustment for the local tick rate is a relativistic correction, but it is largely an altitude correction. There are also tidal effects in this correction, mostly from the Earth tides (which cause slight changes in elevation). There are also tidal effects in that a clock ticks a tiny, tiny bit faster at midnight than it does at noon. Lunar effects are twice as big as are those from the Sun. Note well: There is no correction in TAI for the distance between the Earth and the Sun. The corrections are made only to get all of the clocks marching to the same beat.

 

A whole bunch of time standards are offset from TAI by a fixed amount. These include Loran time, Terrestrial Time (TT), and GPS time. Our civilian time, UTC, is also a fixed offset from TAI, but that fixed offset is incremented or decremented by one second on occasion. This offset plus the occasional leap second keeps UTC to within one second of UT1, which is essentially mean solar time. Once again, there is no correction for the distance between the Earth and the Sun for these time scales. It would in fact be erroneous to make such a correction.

 

It is only when one looks outside the Earth-Moon system and does so from a fully relativistic perspective that one needs a time standard that does account for the varying distance between the Earth and the Sun. JPL, for example, uses a home-brewed time standard, T_eph. JPL's T_eph on average ticks at the same rate as do our Earthbound clocks, but the exact rate varies ever so slightly as the Earth goes from perihelion to aphelion and back again. The difference between JPL's T_eph and TT is never more than a few microseconds.

Edited March 2, 2012 by D H

[Cap'n Refsmmat]

zorro, when you quote someone's post, all the words between the quote tags will show up as written by them. For example, this:

 

Some words D H said.

 

shows up as this:

 

Some words D H said.

 

If you want to add a reply in the middle, just replicate the quote tags:

 

Some words

Those aren't words!

 

D H said.

See?

 

That comes out like so, meaning you don't need colors or Comic Sans:

 

Some words

Those aren't words!

 

D H said.

[JustinW]

Has no one used the definition I have heard alot on this forum before: Time is that which a clock measures. Measures is the key word in that definition. It is the measurement of movement of an object from one point in space to another relative to a constant. The constant we use is the speed of light. Time is not a physical property, so a "measurement" is about as close as you're going to get to any inlightenment on the definition of time.

 

The best and simplest explanation for why space and time are connected I actually heard on a t.v. show. They said if I asked you to meet me at 2 o'clock, you would have to ask where. And if I asked you to meet me at a certain place, you would have to ask when. This is why we use the term spacetime. This is why you can't have one without the other. And isn't it ironic how neither are physical properties, but instead measurements. Well there is some debate of space being a physical property, but I think that might be better in another thread.

 

 

 

Just figured I would ramble some of bordome out.

Edited March 2, 2012 by JustinW