How do you know who is moving?

[iNow]

According to your logic, it appears very much that energy is just a "consideration" as well.

 

You have been answered repeatedly regarding the defintion of time as pertains to empiricism. Are you after something more metaphysical perhaps?

[Eric 5]

Neither. When we measure time we measure oscillations. Do you think the same about distance, that it's either energy or a concept?

 

Those things that you experience, sense, or perceive are either those things that are physical, (the world outside of you) or those things that you think about or imagine, (the "world" inside your mind). There is no neither.

 

Are you saying that time is an oscillation?

 

Distance is a measurement between points whether real or imagined. Distance, like time is just a measurement and not a thing.

 

Distance is a measurement between points. Time is the measurement of the motion of objects between points. Time is a measurement of motion, it is not a thing that exists on its own.

 

I will ask you again. Do you think time is a physical thing, or a concept?

[Reaper]

Reaper! Get off the sidelines and into the game. What do you have to say about all of this? Talk to me. State your opinion. Maybe you and swansont can team up and give a good definition of time that supports the idea of time dilation. Come on reaper, don't be shy, join in the fun. I would welcome another player in all of this.

 

Nah, I'll let you go on entertaining us with your ignorance.

 

I'll nuke you later, when you begin to bore me . Besides, I have another flame war elsewhere that I have to settle....

[Cap'n Refsmmat]

Time is the measurement of the motion of objects between points.

So an object that does not move does not experience time?

 

How do you define the reference frame for this motion? If we apply relativity, surely two objects with constant speed could justly claim that each experiences no time because their reference frame can be defined as the viewpoint of either.

 

Time is a fundamental quantity that we can measure through periodic events.

[swansont]

Yes that looks loke the same book.

 

This is the book Einstein wrote. Any other book not written by him or under his guidance are just an interpretation.

 

This is the book Einstein wrote. It is simple and to the point. Exhaustive text on the subject are just interpretations of what Einstein wrote. Making it more complicated does not make it more true or workable.

 

It would be a mistake to assume that Einstein's works are comprehensive. Scientific knowledge is collaborative.

 

 

Facts speak for themselves.

I am not going to believe in time dilation being an actual physical occurrence, because that is not how science is conducted.

 

Maybe you can tell me the relationship of how this thing called time, is measured by a clock.

 

Why, so you can ignore it again?

 

[math] \omega = \frac{d\theta}{dt}[/math] so [math]\theta = \omega t[/math]

 

If you have an oscillator and count the phase (number of oscillations), it is proportional to time. That's how a clock works. That's what the equation above shows.

 

 

A clock is a physical object, what physical thing is it measuring? Time is either an energy form, (energy that flows, or energy that is condensed, as in matter) Or time is a concept. Which is it?

 

A voltmeter is a physical object. What physical thing is it measuring?

 

Time is temporal.

 

We can measure what this force (gravity) does in the physical universe. We may not know what exactly causes this force (gravity), but we see its effects. The term of gravity was given to this force that is observable.

 

The force of gravity was existing before man existed and before he gave it a name. What was time before man existed and gave it a name? Nobody needs a device to measure gravity to know that it is there. The presence of gravity has an effect on everything in its sphere of influence. Gravity exists without being measured.

 

It does? How do you know this? How do you observe gravity without using something to observe an acceleration?

 

What is time when it is not being measured? Without a clock what is this thing called time? What does a clock measure? How does anyone know this time thing exists without a clock?

 

Tell me what time is. You have two options. Either time is a form of energy, or time is a consideration. Which do you think?

 

False dichotomy. Either you are a rock or you are a plant. Which is it?

[Janus]

Yes that looks loke the same book.

 

This is the book Einstein wrote. Any other book not written by him or under his guidance are just an interpretation.

That's just ridiculous. It's like saying that anything written on evolution that wasn't written by Darwin is just an interpretation.

 

This is the book Einstein wrote. It is simple and to the point. Exhaustive text on the subject are just interpretations of what Einstein wrote. Making it more complicated does not make it more true or workable.

This book was written as an introduction of Relativity to laymen. It does a fair job of that. But it is far from a complete description of the theory.

 

 

"If you can't explain it simply, you don't understand it well enough." Albert Einstein

 

 

The book states that time appears to move slower. Einstein mentions clocks on trains. No specific clocks, just clocks. Einstein did not care to say what kind of clock because that is beside the point. The point is that because the speed of light is the same in all reference frames, moving or stationary, the only factor that can introduce a change in two clocks moving in two different reference frames, is the time it takes light to travel to the observer. The light from the clock near the observer will get to that observer more quickly than the light coming from a clock further away. In all the experiments of time dilation according to Special Relativity, there is supposed to be an observer near one clock and one that is further away that is moving relative to the observer. Just by the fact that there is a greater distance between the two clocks from the observers viewpoint means that the time it takes for light to reach the observer from the distant clock will be different from the time it takes light to reach the observer from the closer clock. When the observer looks at both clocks simultaneously, the light from the further clock will be carrying information that is “old” compared to the clock near by. Any light from the distant clock will be that light that was reflected off the clock and had to travel a distance. While that bit of info from that reflection is traveling it carries info of a past event. “Time” has carried on and things have changed since that light left the distant object. The data that an observer receives from this distant object cannot be considered what is actually occurring at the distant object at the time of receiving the data. Here is an example. Two of the same guns with two of the same type of ammunition. One gun is ten feet away from a target, the other gun is one hundred feet away from the target. Both guns are fired at the same time, the bullet from the closer gun will always reach the target first. Why? Is the further gun slower? Did the further bullet travel slower? No. The distance is greater.

 

Now apply this to observing two clocks. To the observer light from the closer clock will reach him sooner that light from the further clock. If he then assumes that he further clock is slower, he is mistaken. It is not time that went slower, it was that there was a greater distance for the light to travel.

This is just wrong, and a complete mis-interpretation on your part of what the book says.

 

 

Read the book. Look at chapter 8 entitled “on the idea of time in physics” It agrees with what I am saying. It is all relative to the speed of light from an object to an observer.

 

I have read (and re-read) the book. I've owned a copy for 30+ years. And you are again mis-interpretating What the chapter says.

[Norman Albers]

In any frame of reference, defined as multiple observers at an unchanging distance from each other, we define simultaneity by comparing "clocks" after subtracting for the propagation time. A different set of observers may be passing through the same locale, say three spaceships, and they are free to define their own simultaneity also. Whichever set of observers has their clocks "going off" with a light or alarm at the same time, the other set will not think they are at all at the same time. I find it helpful and necessary to hang with and work the actual transform equations: [math]x' = \gamma(x-vt)[/math] and [math]t' = \gamma(t-vx/c^2) [/math]. A good exercise is to multiply both sides of the second statement by c, then square both equations, then subtract them to get a statement for: [math](x')^2 - (ct')^2. [/math] What do you get?

[John Cuthber]

Eric, this question implies an assertion for which there is no evidence.

"John, tell me, time is either a consideration, or a physical form of energy (energy that is flowing or condensed as in matter.) Which is it?"

 

It's like saying "time is either an orange or a table; which is it?".

Why on earth should I think it's either?

Whatever it may be and however you (or anyone else) chooses to define it; time is observably something that dilates in acordance with relativity.

 

Wake up and smell the coffee; time dilation is a genuine scientific observation. Nobody says you have to like it and if you choose not to believe it that's your problem.

However don't try to pretend that your refusal to see the nose on your face is scientific.

[thedarkshade]

Physics has no standard definition of time? Are you going to tell me that measurements in the nanoseconds have no standard definition. Is time a physical thing? Or is time a human mind thing? When physics states that a time dilation occurred what definition of time are they using? A dilation of what exactly. What kind of science is this? Sounds like if there is no good working definition of time, then there can be no absolute measurements that use time as a measurement especially as small as a nanosecond.

We have the definitions according to which we can do all the science, but there is nothing that reveals the true nature of time. Time is not physical, what kind of a question is that? You can touch it, see it, hold or anything that you can do with anything physical (objective).

 

There is a lot of mystery related to time! How do clocks measure this mystery?

That is something that we have created for our practical uses!

 

You tell me that physics does not fully understand time and yet you want me to trust their findings when they say that they measured this thing down to the nanosecond.

There is no full understanding of time, but this does not prevent us doing all the science correct despite the level of understand of time that we have now!

 

Like a nanosecond is some real thing. A nanosecond of what?

You might be right here, but seconds and nanoseconds and whatever else about time are working good so far, so why not keep on with them!

 

You want me to believe what I am told, and ignore what I see.

If you literally mean "see", then you got to know that physical perception and perception in general cannot provide a good understanding of the world!

 

“In philosophy there are several points of view” What about physics? So far you have said that time is:

 

1. A mystery.

2. Could be metaphysical.

3. Beyond our understanding

4. Cannot be fully understood.

5. Very little progress has been done in the field of time.

So you want me to lie? This is what we got so far! You can't really experiment or observe something that belong to subjective, and this makes things complicated!

[Janus]

I going to go a little deeper in to the following quote from Eric 4 and show why it is a mis-interpretation of time dilation as described in the book.

 

The book states that time appears to move slower. Einstein mentions clocks on trains. No specific clocks, just clocks. Einstein did not care to say what kind of clock because that is beside the point. The point is that because the speed of light is the same in all reference frames, moving or stationary, the only factor that can introduce a change in two clocks moving in two different reference frames, is the time it takes light to travel to the observer. The light from the clock near the observer will get to that observer more quickly than the light coming from a clock further away. In all the experiments of time dilation according to Special Relativity, there is supposed to be an observer near one clock and one that is further away that is moving relative to the observer. Just by the fact that there is a greater distance between the two clocks from the observers viewpoint means that the time it takes for light to reach the observer from the distant clock will be different from the time it takes light to reach the observer from the closer clock. When the observer looks at both clocks simultaneously, the light from the further clock will be carrying information that is “old” compared to the clock near by. Any light from the distant clock will be that light that was reflected off the clock and had to travel a distance. While that bit of info from that reflection is traveling it carries info of a past event. “Time” has carried on and things have changed since that light left the distant object. The data that an observer receives from this distant object cannot be considered what is actually occurring at the distant object at the time of receiving the data. Here is an example. Two of the same guns with two of the same type of ammunition. One gun is ten feet away from a target, the other gun is one hundred feet away from the target. Both guns are fired at the same time, the bullet from the closer gun will always reach the target first. Why? Is the further gun slower? Did the further bullet travel slower? No. The distance is greater.

 

The above contends that what Einstein meant by a clock in a moving frame ticking slower was that the light received from a receding clock would take longer and longer times to reach an observer, causing an observed slowing of the receding clock.

 

Example:

Clock B recedes from clock A at 0.1c.

If at the point when clock B was zero distance from clock A both clocks read a time of zero, then after 1 sec clock B will be 1/10 of a light sec from A. The light carrying the image of Clock B reading 1 sec, will then take 0.10 sec to reach clock A. Therefore clock A will read 1.1 sec when an observer next to clock A sees clock B read 1 sec. As B continues to recede, The observer will see Clock A read 2.2 sec when clock B reads 2 sec, clock A read 3.3 sec when clock B read 3 sec, etc. Always a 1.1 to 1 ratio of clock A to B.

Accordingly we can get other ratios for different speeds for clock B such as below.

 

0.25c gives a 1.25:1 ratio

0.5c gives a 1.5:1 ratio

0.75c gives a 1.75:1 ratio

0.99c gives a 1.99:1 ratio

 

So the higher the speed of B, the slower the observer sees it run. But is this the effect Einstein is really writing about in the book? Let's see, why don't we?

 

In the book he gives an equation for time dilation that predicts the ratio between the rates of a "stationary" and moving clock. The equation is as follows:

 

[math]t = \frac{t`}{\sqrt{1-\frac{v^2}{c^2}}}[/math]

 

In our example above t` would be the time reading on clock B and t the reading on clock A as determined by an observer with clock A.

If we plug in the velocities from our previous example into this equation we get:

 

0.1c gives a 1.005:1 ratio

0.25c gives a 1.033:1 ratio

0.5c gives a 1.155:1 ratio

0.75c gives a 1.512:1 ratio

0.99c gives a 7.089:1 ratio

 

These values disagree with the previously values above by several percent, with the last value disagreeing by 150%!

 

So it is obvious that Einstein was not considering the increasing time lag for signals traveling between the clocks as the mechanism behind time dilation, because this mechanism is inconsistent with the equation he uses for time dilation. To claim otherwise is a mis-interpretation of his writings.

[JohnFromAus]

When I started this thread a few days ago I was not expecting it to run quite as it has! Anyway - I've learned a lot both from the thread and other reading ( others apparently haven't) and make the following comments.

 

1 The twins paradox is not a paradox if you understand SR - it is a fact. The point I, and I think others, miss is that the twin who stays put is in an inertial frame and can correctly apply SR - predicting correctly that his/her twin will be younger on return. However the twin who changes his/her velocity to be able to leave and return is NOT in an inertial frame all the time and cannot use SR from his/her frame. SR applies only to inertial frames. The twin in the non inertial frame must apply GR and if he/she does, comes to the same conclusion. I cannot yet apply GR myself so have ordered an introductory text on GR to get me on the way. However I would be very surprised in GR contradicts the results of SR! My ignorance of something does not make it wrong!

 

2 Time dilation is nothing whatsoever (lovely word that) to do with the the fact that on clock is moving AWAY from the other. The factor involved has only v squared in it and thus it does not matter whether the frames are approaching each other or receding from each other - time is dilated.

 

3 I go back to my earlier post where I pointed out what is meant by an observer. The book I have of course defined an observer but I had not really thought about what that meant. From some of the posts I think others could do with spending some time pondering just what an observer is and what the consequences of that are. Most importantly an observer is not a single clock at a particular point which several of the posts seem to imply.

 

4 As to those who imply time isn't there if no one is measuring it I say wait till your 65 and the effects of time will be only too apparent whether you were watching the clock or not!

 

John

[Eric 5]

Interestingly our definition of length is based on time, so if we can't measure time, we also can't measure length... *hits random people with a ruler*

 

 

Go to your dictionary and read the all definitions of length, and time. Then see if that is what you meant to say.

[Cap'n Refsmmat]

Sayonara's signature used to contain a counterargument to that, but since it doesn't:

 

"Dictionary.com is not a technical resource."

 

Dictionaries record the common meanings of terms, not the precise definitions given to them by science.

[Eric 5]

What do you mean by "a consideration"? It seems to me time has the same qualities as the other dimensions and can be measured with appropriate instruments. What's the difference between measuring a length with a ruler and a time with a clock? Length is not an energy but I assume you are not denying that length can be measured.So I am assuming you believe length to be a "consideration" which can be measured. So what's the big problem about time? Are you also denying the fact that there will be a difference in the length of an object measured in its rest frame to that measured in a frame in relative motion?

 

 

 

You know john, all of my long explanations that I have done on this thread stating that I do not see how time dilation is physically possible according to how time is defined in standard reference books, could have been simplified by asking people to go to a standard dictionary and define the term time. So my only answer to you is to define the term time and then re-read your reference on time dilation. Thank you.

 

Sayonara's signature used to contain a counterargument to that, but since it doesn't:

 

"Dictionary.com is not a technical resource."

 

Dictionaries record the common meanings of terms, not the precise definitions given to them by science.

 

 

 

If you do not like “dictionary.com” then use a different source. Please feel free to use a dictionary that you are comfortable with. Just define the term. Thank You.

 

Nah, I'll let you go on entertaining us with your ignorance.

 

I'll nuke you later, when you begin to bore me . Besides, I have another flame war elsewhere that I have to settle....

 

 

 

I do not see that you have presented any definition of time from a standard dictionary. Please define the term time and then we can talk. Thank you.

 

 

P.S. Good luck with that flame war.

 

According to your logic, it appears very much that energy is just a "consideration" as well.

 

You have been answered repeatedly regarding the defintion of time as pertains to empiricism. Are you after something more metaphysical perhaps?

 

 

I have not seen anyone post, or quote a standard reference of the term time according to a standard dictionary. If you would like, you can do so. Thank You.

 

3 I go back to my earlier post where I pointed out what is meant by an observer. The book I have of course defined an observer but I had not really thought about what that meant. From some of the posts I think others could do with spending some time pondering just what an observer is and what the consequences of that are. Most importantly an observer is not a single clock at a particular point which several of the posts seem to imply.

John

 

If you really want to know what an observer is, look up the word observer in a dictionary. Simple as that.

[Cap'n Refsmmat]

Perhaps you missed my point.

 

Stop relying on the dictionary. It defines the common meaning of terms, the meaning used day-to-day by ordinary people. We are concerning ourselves with physics. What the dictionary says is irrelevant. What matters is the commonly accepted definition of these things in physics.

 

And if you're wondering about the definition of time, read up.

[swansont]

And if you're wondering about the definition of time, read up.

 

A little more informally, time is what is measured by a clock.

 

An observer is anything that can make a measurement.

[Klaynos]

If you do not like “dictionary.com” then use a different source. Please feel free to use a dictionary that you are comfortable with. Just define the term. Thank You.

 

 

Sure thing. Let's use the National Physical Laboratory...

 

The National Physical Laboratory (NPL) is the UK’s National Measurement Institute and is a world-leading centre of excellence in developing and applying the most accurate measurement standards, science and technology.

 

They're quite well known... and one of the leaders in the field of defining thing....

 

Lets see what they say about distance/length, so the metre is a nice standard measure...

 

http://www.npl.co.uk/server.php?show=ConWebDoc.1560

 

The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

 

OH NOES! Seems that it's defined by time...

 

Of course we could also discuss the closeness of time and space by discussing the 4-vector but I doubt you'd like that either, it's rather mathematical, which is something your 'arguments' are missing...

[JohnFromAus]

This thread is going nowhere. Perhaps its time to close it down.

 

It has helped me get a better grip on SR and I thank all those who responded to the questions I asked and confirmed some of my thinking.

 

I have enjoyed reading all the posts - some with a smile - some with puzzlement and some with - Ah hah!

 

Thanks

John

[Cap'n Refsmmat]

Fine with me. There's another thread along similar lines anyway.