# Time: What We Read On The Clock?

• B
• DanAil
In summary: And if we can do this, then we can similarly design a clock that does not have errors and tells "true" time just as your hypothetical ruler tells "true" distance.In summary, the statement that time is what we read on the clock is a confusing statement. It is possible that clocks measure 'aging', not 'time'. The problem has been resolved by more accurate pendulum clocks.
DanAil
Gold Member
This is a basic question, in the sense that it is simple but could be also considered as fundamental.

It has been stated on this forum, that time is what we read on the clock. It is mentioned that this was also a statement by Einstein himself (Zeit ist das, was man an der Uhr abliest).

This seems to be confusing. After all, clocks are supposed to 'measure' time and declaring that time is what they display is kind of ‘upside down’ - like putting the cart in front of the horse. We are striving to measure things more and more accurately, but no instrument can quantify something with an absolute certainty. Several factors could cause a measurement to have errors - temperature, humidity, movement, etc.

The question: What is the rational behind the statement that Time is what we read on the clock?

The thing that clocks measure is an important quantity since it is a relativistic invariant and since it governs physical processes. Since it is important it should have a name. Why not “time”?

russ_watters
Dale said:
The thing that clocks measure ... should have a name. Why not “time”?
It could make more sense to state that clocks measure 'aging', not 'time'.

DanAil said:
clocks are supposed to 'measure' time and declaring that time is what they display is kind of ‘upside down’
We also say rulers measure distance even though we know rulers have finite error. Would you raise the same objection to that?

DanAil said:
It has been stated on this forum, that time is what we read on the clock
Can you give specific references to posts?

DanAil said:
It could make more sense to state that clocks measure 'aging', not 'time'.
Even things that don’t age are still affected by the thing a clock measures.

If someone asks you “what time is it?”, to answer them you consult a clock. If I wanted you to tell me the reading on your watch I wouldn’t ask “what aging is it?” So it seems reasonable to me to call it “time”.

Why don’t you?

russ_watters
There is an enlightening story:

Clocks in the 18th century were large pendulum clocks. Although a pendulum clock could keep almost perfect time on land, its ability to keep accurate time at sea was greatly diminished due to the fact that sailing ships rock, pitch, roll and sway on the ocean waves. Such aggressive movements threw the pendulum’s swing off-beat, rendering the clock useless. Accurate clocks were necessary to determine the longitude of a ship. A substantial prize was offered to anyone who successfully solves the problem.

A scientist stated that time is what we read on the clocks and came up with an equation that corrects the time of the clocks at sea. This equation was considering the period of the rocking of the ship and the amplitude, but not its direction. With that, the problem has been resolved.

DanAil said:
There is an enlightening story
Of course the above story is not real. The actual solution was that more accurate pendulum clocks have been built by John Harrison - making them in general smaller and thus less receptive to the rocking.

Why is this relevant? Bad clocks don't measure time well, just like bad rulers don't measure lengths well, bad thermometers don't measure temperature well...

russ_watters, malawi_glenn, DanAil and 1 other person
PeterDonis said:
We also say rulers measure distance even though we know rulers have finite error. Would you raise the same objection to that?
Yes - we should not state that 'distance' is what the ruler reads - the measuring instrument could have errors caused by its design and the environment. If for example, the ambient temperature is higher, then the ruler could expand and erroneously display that the distance that we try to measure is shorter than it actually is.

Motore
DanAil said:
it actually is
So how do you know what the distance "actually is"?

@DanAil you are quibbling about the common use of words, none of which usage is going to change just because you don't approve of it. You are doing what in the military is called "pissing up a rope".

malawi_glenn
DanAil said:
we should not state that 'distance' is what the ruler reads
Why not? If someone asks me “what is the distance between those two wall studs?” how else should I answer? Or if I want someone to use a ruler what should I ask?

PeterDonis said:
So how do you know what the distance "actually is"?
By designing for example a ruler that does not expand or shrink with temperature.

Motore
You seem to think that simply because measurements have uncertainty that we should not use any words to refer to the quantities that our devices measure. If that is not your actual position then please clarify.

DanAil said:
By designing for example a ruler that does not expand or shrink with temperature.
And if we can do this, then we can similarly design a clock that does not have errors and tells "true" time just as your hypothetical ruler tells "true" distance. In which case your objections evaporate.

Or, we could ask how we know your hypothetical ruler doesn't expand or shrink with temperature? And we would realize that no actual measuring device has infinite accuracy, so there is no way to actually build your hypothetical ruler (or the corresponding hypothetical clock that measures "true" time with infinite accuracy). And we would realize that there is no point in gerrymandering our use of language because of this, and we would just refer to what a ruler measures as "distance" and what a clock measures as "time" and be aware of the limited accuracy of all actual measurements and go on and do physics.

nasu, Motore and phinds
Why is this relevant?

Very good question!

Could it be, for example, that something, somehow is causing faster moving clocks to slow down?

Could we build clocks that are not susceptive to higher velocity?

PeroK, Motore and weirdoguy
DanAil said:
What is the rational behind the statement that Time is what we read on the clock?
The classic GR textbook, Misner, Thorne, and Wheeler, discusses this issue in section 1.5.

malawi_glenn
DanAil said:
Could it be, for example, that something, somehow is causing faster moving clocks to slow down?

Could we build clocks that are not susceptive to higher velocity?
How would we know it was not "susceptive to higher velocity"?

You can keep going on and on around this merry go round forever, or you can adopt the position I argued for in post #16.

DanAil said:
Could it be, for example, that something, somehow is causing faster moving clocks to slow down?

Could we build clocks that are not susceptive to higher velocity?
If that were to happen some time in the future then relativity would be proven wrong. If that were to happen then we might revisit our terminology.

In the meantime, that unlikely future possibility doesn’t change the fact that measurements are important and so they should have words for them. And the words are already in common use for the purpose of referring to the measured quantities.

russ_watters and DanAil
Dale said:
If that were to happen some time in the future then relativity would be proven wrong. If that were to happen then we might revisit our terminology.

John Harrison solved the longitude problem by designing the clocks smaller.

What if we make the moving clocks not only small, but also 'heavier' - or (to use just one parameter) denser. So dense, that their own gravitational field creates a gravitational well. Of course such a clock might slow down a little because of gravity, but will it be 'susceptive' to very high velocity comparing it with a clock which mass can be almost ignored?

That's not how relativity works. I'd say some reading is called for.

russ_watters
DanAil said:
will it be 'susceptive' to very high velocity comparing it with a clock which mass can be almost ignored?
Yes.

russ_watters
DanAil said:
Of course such a clock might slow down a little because of gravity, but will it be 'susceptive' to very high velocity comparing it with a clock which mass can be almost ignored?
If relativity is correct, the construction of the clock is irrelevant to the relativistic effects.
(Of course relativity might be incorrect, but with an ever-growing mountain of evidence that agrees with relativity and the complete absence of any evidence that disagrees with relativity that’s not a serious possibility).

Be aware also that the way you are thinking of time dilation is mistaken - as @DaveC426913 says above, “that’s not how relativity works”. Yes, moving clocks run slow compared to stationary clocks, but also we may consider either clock to be the faster stationary one. Think about this for a moment and you will see that your hypothetical clock unaffected by time dilation leads to unfixable logical contradictions.

DanAil and russ_watters
DanAil said:
John Harrison solved the longitude problem by designing the clocks smaller.

What if we make the moving clocks not only small, but also 'heavier' - or (to use just one parameter) denser. So dense, that their own gravitational field creates a gravitational well. Of course such a clock might slow down a little because of gravity, but will it be 'susceptive' to very high velocity comparing it with a clock which mass can be almost ignored?

We do not use pendulums for accurate clocks anymore. You have some new inventions to read about and buy

DaveC426913, russ_watters and phinds
Dale said:
You seem to think that simply because measurements have uncertainty that we should not use any words to refer to the quantities that our devices measure. If that is not your actual position then please clarify.
@DanAil since you did not clarify, I assume that you felt this was a sufficiently correct understanding of your position.

I can only say that I heartily disagree. Even with uncertainty, measurements are still the primary tool we have for checking our models against reality. Measurements are therefore at least equally as important as theory and thus equally deserving of having words assigned.

Given that, it seems natural to use the words that are already being commonly used to refer to the things being measured.

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weirdoguy, DanAil, malawi_glenn and 1 other person
DanAil said:
John Harrison solved the longitude problem by designing the clocks smaller.

What if we make the moving clocks...
John Harrison did not feel the need to invent a word to replace "time" or "clock" when he invented a better one. He understood he was simply correcting measurement error. And it was a well known error at the time.

This entire initial line of discussion has been a wrong/pointless attempt to soften the blow of your real purpose here: to argue our current clocks - and therefore understanding of time - are erroneous, and present your personal theory on the subject.

[Unpublished] personal theories are forbidden on PF and you need to learn/understand the current ones before looking for flaws. Thread locked.

PeroK, Motore, vanhees71 and 2 others

## 1. What is time and how is it measured?

Time is a concept that describes the duration of events and the intervals between them. It is measured using various units such as seconds, minutes, hours, days, and years.

## 2. Is time a physical or a man-made concept?

Time is both a physical and a man-made concept. The physical aspect of time is related to the movement of objects in space, while the man-made aspect refers to the way we measure and perceive time.

## 3. Why do we have different time zones?

Time zones were created to standardize time across different regions and make it easier to coordinate activities and travel. They are based on the rotation of the Earth and the position of the sun.

## 4. Can time be manipulated or controlled?

Time cannot be manipulated or controlled in the traditional sense. However, it can be affected by factors such as gravity and speed, as described by Einstein's theory of relativity.

## 5. How accurate are our methods of measuring time?

Our methods of measuring time have become increasingly accurate over the years. Currently, the most accurate atomic clocks can measure time to within one second in 100 million years.

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