Absolute and Relative Time

[Mike Helland]

We all know the story. Newton said time is absolute. Einstein said time is relative. A tale so ingrained and unquestionable, that bringing it up for any reason other than the setup to a meme might seem pointless.

But I would like to show you that this story is not the whole truth.

Newton

Let’s start with Newton, who has this to say, on page 6 of the Principia:

I do not define time, space, place, and motion, as being well known to all. Only I must observe, that the common people conceive those quantities under no other notions but from the relation they bear to sensible objects.

Newton introduces his physics to the world by saying that the “common people” only understand space and time by how they relate to the senses. In other words, prior to him, people only thought of time and space as relative. Or at least that’s what he’s claiming.

He continues:

And thence arise certain prejudices, for the removing of which it will be convenient to distinguish them into absolute and relative, true and apparent, mathematical and common.

I. Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration: relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.

II. Absolute space, in its own nature, without relation to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies; and which is commonly taken for immovable space

We see here that Newton very explicitly says there are two types of time, one of an absolute nature and one of a relative nature, involving measurements and observations. And he provides similar definitions for absolute space and relative space.

While it can be debated what he meant precisely, it should be clear that simplifying his position to “time is absolute” does not tell the whole story.

I posted parts of the above quote by Newton in a tweet to Ethan Siegel and this was his response:

This is not meant to be a criticism of Dr. Siegel, who is kind enough to reply, just to illustrate how persistent this story is.

We can see that in Newton’s work, right on page 6, he explicitly defines what he means by space and time. There is nothing tacit about it. But these words rang a bell.

Einstein

We find in the book Relativity, by Einstein, page 32, the following:

Now before the advent of the theory of relativity it had always tacitly been assumed in physics that the statement of time had an absolute significance, i.e. that it is independent of the state of motion of the body of reference. But we have just seen that this assumption is incompatible with the most natural definition of simultaneity; if we discard this assumption, then the conflict between the law of the propagation of light in vacuo and the principle of relativity (developed in Section VII) disappears.

There’s the same “tacit assumption”, but with a twist. Einstein had written “it had always tacitly been assumed in physics that the statement of time had an absolute significance”, whereas Siegel modifies the general “in physics”, to be specifically “in Newton’s work”, which I hope I have shown is not the case.

It appears from the quotation by Einstein that he is in fact claiming time to be relative, and only relative. That is a fair impression to get from this quote, and it seems that even Einstein’s contemporaries would have gotten a similar impression.

Here is Heisenberg’s account of a discussion with Einstein:

“But you don't seriously believe," Einstein protested, "that none but observable magnitudes must go into a physical theory?"

"Isn't that precisely what you have done with relativity?" I asked in some surprise. "After all, you did stress the fact that it is impermissible to speak of absolute time, simply because absolute time cannot be observed; that only clock readings, be it in the moving reference system or the system at rest, are relevant to the determination of time."

"Possibly I did use this kind of reasoning," Einstein admitted, "but it is nonsense all the same. Perhaps I could put it more diplomatically by saying that it may be heuristically useful to keep in mind what one has actually observed. But on principle, it is quite wrong to try founding a theory on observable magnitudes alone. In reality, the very opposite happens. It is the theory which decides what we can observe."
(In Physics and Beyond - Encounters and Conversations, Harper Torchbooks, 1972, p. 63.)

It could be interpreted that “it is impermissible to speak of absolute time, simply because absolute time cannot be observed” means that since it is not observed, it doesn’t exist. That would lead to the conclusion that “time is relative”.

The interpretation I lean toward is that Heisenberg and Einstein recognized, just as Newton had, there is both absolute and relative time, not just one or the other. They simply claimed absolute time was unobservable and not relevant to physics. Which would be different than saying it didn’t exist.

The idea that time can be only relative, or only absolute, seems to be a late 20th century invention, used to emphasize how revolutionary Einstein’s relativity was. A consequence of this is that we’re presented with a false dilemma, we have to choose between time being one way or the other.

For Newton and Einstein, I do not think this dilemma was present, and both would be comfortable with absolute time and relative time each existing in their own ways.

The disagreement among them would have been that Newton felt his physics described absolute time and space, while Einstein would have asserted that his physics describe the world of relative time and space.

Everett

In the case where the mathematics of a theory only allows for one type of time, then there is a valid reason to choose one. And since relative time is what is actually observed, and it is desirable for theories to describe what is actually observed, then relative time is the best choice.

But what about a physical theory whose mathematics allow for two types of time? Due to our modern intuition to accept the false dilemma between absolute and relative time, it might be difficult to identify such a theory.

Hugh Everett may be best known for the “Many Worlds Interpretation of Quantum Mechanics”, but the real story behind that is over simplified as well.

Everett wrote a very lengthy thesis called “The Universal Wavefunction”. It was far too long to be a PhD thesis, so he wrote a shorter thesis, with many of the same ideas, known as “The Relative State Formulation of Quantum Mechanics”.

The first thesis was later read by Bryce DeWitt, who interpreted the work as suggesting parallel realities, and named it the “Many Worlds Interpretation”.

But it is Everett’s relative state formulation that is the most relevant to a discussion about absolute and relative time. Proposed as both a way to go about solving the problem of quantum gravity, and as a solution to the measurement problem, the ambitious Everett went so far as to name his work a “formulation” rather than an “interpretation” of quantum mechanics.

His solution to the measurement problem is to essentially flip it upside down. Rather than ask “what is the role of measurement in the model”, Everett says it is our task to model a measurement being made. He writes on page 9

We have the task of making deductions about the appearance of phenomena
to observers which are considered as purely physical systems and are treated
within the theory. To accomplish this it is necessary to identify some present
properties of such an observer with features of the past experience of the
observer. Thus, in order to say that an observer 0 has observed the event α,
it is necessary that the state of 0 has become changed from its former state
to a new state which is dependent upon α.

It will suffice for our purposes to consider the observers to possess memo-
ries (i.e., parts of a relatively permanent nature whose states are in correspon-
dence with past experience of the observers). In order to make deductions
about the past experience of an observer it is sufficient to deduce the present
contents of the memory as it appears within the mathematical model.

As models for observers we can, if we wish, consider automatically func-
tioning machines, possessing sensory apparatus and coupled to recording
devices capable of registering past sensory data and machine configurations.
We can further suppose that the machine is so constructed that its present
actions shall be determined not only by its present sensory data, but by
the contents of its memory as well. Such a machine will then be capable
of performing a sequence of observations (measurements), and furthermore
of deciding upon its future experiments on the basis of past results. If we
consider that current sensory data, as well as machine configuration, is im-
mediately recorded in the memory, then the actions of the machine at a given
instant can be regarded as a function of the memory contents only, and all
relavant [sic] experience of the machine is contained in the memory.

For such machines we are justified in using such phrases as “the machine
has perceived A” or “the machine is aware of A” if the occurrence of A is
represented in the memory, since the future behavior of the machine will
be based upon the occurrence of A. In fact, all of the customary language
of subjective experience is quite applicable to such machines, and forms the
most natural and useful mode of expression when dealing with their behavior,
as is well known to individuals who work with complex automata.

What Everett is describing here could use an updated example, using modern technology.

Consider a computer running a physics engine. We’ll call this computer A, and it has its memory, which we’ll call memory A.

The physics engine models subatomic particles, like electrons and quarks, and also photons and other force carriers. With just those basic building blocks, It can model liquids, and solids, and gases. The basic particles can make up elements and molecules, and macroscopic objects like billiard balls and clouds. They should be even to make all the components of another computer, or a smartphone. Let’s call that computer B.

A smartphone fits Everett’s criteria for an observer: automatically functioning machines, possessing sensory apparatus and coupled to recording devices capable of registering past sensory data and machine configurations.

If computer B has a camera and is loaded with the proper software, it could examine its environment, and record measurements of things around it relative to each other. These measurements could be recorded in computer B’s memory, which is called memory B.

So now we have memory A, which contains the properties of subatomic particles that make a variety of objects, one of which is an observer whose memory B contains results of its measurements of the other objects.

Memory A and memory B both describe the virtual world, but from two different perspectives. Memory A is how it looks from the outside, and memory B is how it looks from the inside.

Considering such a theory, it’s difficult not to think back to Newton’s original definitions of time:

Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration:

relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion

It seems to me you can draw a line between Newton’s definitions of absolute and relative time to Everett’s relative state formulation.

Conclusion

The story that Newton said “absolute!” and Einstein said “relative!” is useful, illustrative, and mostly true, in the context of what the math describes. But in the bigger picture, and with potentially new mathematical models with new abilities, it should be kept in mind that thinking about time as being only absolute or only relative is a false dilemma that Newton and Einstein would have considered as unnecessary as choosing only one side of a coin to exist. For there to be an “up” but not a “down”.

 

[The Great Zaganza]

A Three-way Celebrity Deathmatch would sort this out in one evening.

 

[deaman]

"I" don't "have" time.

 

[hecd2]

If it has no mathematics, it is either philosophy or journalism, but not physics. Your point is?

 

[alfaniner]

I thought it was going to be this.

“Time is an illusion. Lunchtime doubly so.”

― Douglas Adams, The Hitchhiker's Guide to the Galaxy

 

[Mike Helland]

If it has no mathematics, it is either philosophy or journalism, but not physics. Your point is?

I suppose its conceivable that Newton and Einstein could have developed their physics without ever defining time and space and discussing absolute and relative.

But that's not how it seemed to work out.

And since they did discuss it, in their seminal books, I think it's worth taking a look at what they actually wrote, compared to how its presented by secondary sources.

That said, my point is this:

In the case where the mathematics of a theory only allows for one type of time, then there is a valid reason to choose one. And since relative time is what is actually observed, and it is desirable for theories to describe what is actually observed, then relative time is the best choice.

But what about a physical theory whose mathematics allow for two types of time?

To illustrate, consider F=ma.

The a is acceleration of course, m/s/s, which is a distance over a duration over a duration.

Or E=mc², where the c is m/s.

My point is, these equations only allow for one kind of time and space.

But, in Everett's relative state formulation, where the mathematics describes a purely physical observer that produces record measurements in their own simulated memories, then the mathematics allows for both Newton's definitions of time: absolute as the main model, relative as the measurements the model has made of itself from within.

 

[Ziggurat]

Newton introduces his physics to the world by saying that the “common people” only understand space and time by how they relate to the senses.

That is still the case.

In other words, prior to him, people only thought of time and space as relative. Or at least that’s what he’s claiming.

No, he isn't, because he isn't claiming that before him everyone was common. Rather, he's saying most people don't think about time in any abstract sense.

And why should they, really? For most people, there's really no bloody point in thinking deeply about what time means. A "common people" understanding of time works quite well for almost everything anyone ever needs to do.

He continues:

We see here that Newton very explicitly says there are two types of time, one of an absolute nature and one of a relative nature, involving measurements and observations. And he provides similar definitions for absolute space and relative space.

I don't think you have a clue about what he's saying. Relative time, in the sense that Newton means it, indicates that your reference is arbitrary. The year is now 2021. That's 2021 years from an arbitrary starting year. That's relative. But differences in time between events are still invariant.

And that is fundamentally different between Newton and Einstein.

While it can be debated what he meant precisely, it should be clear that simplifying his position to “time is absolute” does not tell the whole story.

Sure, in the sense that there are some ambiguities in any such short phrasing. Nevertheless, it's true that in Newtonian physics, the difference in time between events is invariant, and in Special and General Relativity, it is not. That is enough of the story.

But what about a physical theory whose mathematics allow for two types of time? Due to our modern intuition to accept the false dilemma between absolute and relative time, it might be difficult to identify such a theory.

That's... not the obstacle preventing the discovery of such a theory. Rather, we have not identified any physical phenomena which exhibit dependence on anything other than relative time. Absent that, including absolute time in a theory is simply superfluous.

And it's not like we don't know how that could happen. It's quite simple, really. All you need is a preferred reference frame, and absolute time will pop out naturally. Conversely, defining an absolute time will also identify a preferred reference frame.

So, can you find such a frame? I doubt it.

 

[Mike Helland]

I don't think you have a clue about what he's saying. Relative time, in the sense that Newton means it, indicates that your reference is arbitrary. The year is now 2021. That's 2021 years from an arbitrary starting year. That's relative. But differences in time between events are still invariant.

And that is fundamentally different between Newton and Einstein.

Is it?

Here's what Newton said about relative time:

"relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion"

A little trimming, we get:

"relative time, is some sensible and external measure of duration by the means of motion"

It's by the means of motion that is important.

Yes, we choose an arbitrary starting point. Call it t=0.

How do we measure duration between the starting point and some other point in time?

By change. By motion. The moving hands of a clock, or grains of sand in an hour glass, or heart beats.

Here's what Mach said:

“It is utterly beyond our power to measure the changes of things by time. Quite the contrary, time is an abstraction at which we arrive through the changes of things.”

Seems entirely in the spirit of what Newton said about relative time.

And later Einstein would stress that only clock readings determine time, (aka, relative time).

Nevertheless, it's true that in Newtonian physics, the difference in time between events is invariant, and in Special and General Relativity, it is not. That is enough of the story.

That's really the most important point, yes.

Rather, we have not identified any physical phenomena which exhibit dependence on anything other than relative time.

Doesn't entanglement require an alternative system of causality?

 

[Ziggurat]

Is it?

Yes, it is.

Here's what Newton said about relative time:

"relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion"

Yes. Motion of objects, like a pendulum, or the sun. That's how clocks worked. The motion he's talking about has jack **** to do with different reference frames ala special relativity.

Doesn't entanglement require an alternative system of causality?

It requires nonlocality. It doesn't require any absolute time.

 

[theprestige]

We all know the story. Newton said time is absolute. Einstein said time is relative. A tale so ingrained and unquestionable, that bringing it up for any reason other than the setup to a meme might seem pointless.

<snip>

You're saying that if we ignore their mathematics - the actual physics of their theories - and take a casual approach to English, we can kinda-sorta pretend they were thinking about time differently than how time is actually thought about in the actual math of the actual theory of time they were actually thinking about.

Yes, that does seem extremely pointless. Why bother? You know as well as we do that it's not the English that describes the theory. If you're using English to describe something different from what their math describes, you're not being interesting, you're being wrong.

 

[hecd2]

My point is, these equations only allow for one kind of time and space.

So?

That does not represent the key difference bewteen Newtonian and Einsteinian concepts of time.

The key difference is encapsulated simply in the difference between the Galilean and Lorentz transforms. In classical mechanics, time is independent of velocity, in SR, not so. That's all.

The consequence of that (plus the equivalence principle) is there can be no preferred frame in relativity. Everett's interpretation of QM is completely irrelevant to the distinction.

 

[Mike Helland]

Yes. Motion of objects, like a pendulum, or the sun. That's how clocks worked.

Indeed. Still do.

Here's what I'm getting at:

"Space, Einstein said, is merely what we measure with a ruler; time is what we measure with a clock"
— Louisa Gilder (2008)

http://www.timeone.ca/quotes/space-...a-ruler-time-is-what-we-measure-with-a-clock/

This is not a primary source. The "time is what a clock measures" is often attributed to Einstein. Did he actually say that anywhere? Any find a reference?

Point is, that's how Newton defined relative space and time. That gets overlooked. So I'm drawing attention to it.

The motion he's talking about has jack **** to do with different reference frames ala special relativity.

With regards to time dilation and length contraction? Yeah, there's no evidence Newton had worked out Lorentz transformations. I didn't mean to imply that he did.

----

*edit* I found this:

https://qig.itp.uni-hannover.de/~giulini/papers/ZeitUndUhr.pdf

It's in German, but I think that's the language of the original quote, if there really is one.

"Zeit ist das, was man an der Uhr abliest"

Interestingly it brings up the same quotes from Newton's Scholium and the one from Mach. (Guessing on the last one, my German ist nichst so gut.)

 

[hecd2]

Point is, that's how Newton defined relative space and time. That gets overlooked. So I'm drawing attention to it.

No. I still don't see the point of this thread. Newton's and Einstein's concepts of time and space are encapsulated in the relevant transforms from one frame to another. I don't see what else there is to say that is not sophomore, gratuitous metaphysics.

 

[Mike Helland]

No. I still don't see the point of this thread. Newton's and Einstein's concepts of time and space are encapsulated in the relevant transforms from one frame to another. I don't see what else there is to say that is not sophomore, gratuitous metaphysics.

It's too bad you weren't around in 1687, and you could have told Newton to stop wasting his time and ours by providing definitions at the beginning at the Principia.

 

[Ziggurat]

Here's what I'm getting at:

"Space, Einstein said, is merely what we measure with a ruler; time is what we measure with a clock"
— Louisa Gilder (2008)

[snip]

Point is, that's how Newton defined relative space and time. That gets overlooked. So I'm drawing attention to it.

Ok.

And?

 

[Mike Helland]

Ok.

And?

When I point out that Newton defined relative time and space as measurements, people respond "No, Newton believed time and space were absolute. Einstein said space and time were measurements."

I would assume that you're probably not fond of misinformation about physics floating around.

So I collected some primary sources, and my thoughts, and presented them here for your consideration.

 

[Steve001]

A little yet extremely sensitive experiment has clearly shown that there ain't no such a thing as absolute time. In this experiment researchers measured gravity induced time dilation over an extremely short distance of 1 millimeter. As typical Mike you have once again greatly missed the mark.

After correcting for non-gravitational effects that could shift the frequency, the clock’s frequency changed by about a hundredth of a quadrillionth of a percent over a millimeter, just the amount expected according to general relativity.

https://www.sciencenews.org/article/atomic-clock-general-relativity-time-warp-millimeter-physics

An older measurement.https://www.nist.gov/news-events/news/2010/09/nist-clock-experiment-demonstrates-your-head-older-your-feet

 

[hecd2]

I would assume that you're probably not fond of misinformation about physics floating around.

So I collected some primary sources, and my thoughts, and presented them here for your consideration.

There hasn’t been any physics in anything you’ve said. The physics is in the transforms.

 

[Ziggurat]

When I point out that Newton defined relative time and space as measurements, people respond "No, Newton believed time and space were absolute. Einstein said space and time were measurements."

The problem is that Newton DIDN'T think that time was relative in the sense that we mean it when discussing special and general relativity.

I would assume that you're probably not fond of misinformation about physics floating around.

You're not actually helping.

 

[Mike Helland]

The problem is that Newton DIDN'T think that time was relative in the sense that we mean it when discussing special and general relativity.

In relativity, the only thing that determines time, is a clock reading.

That's what Newton said relative time was, and he includes this: (whether accurate or unequable).

So I don't think he's claiming that relative time is the same for all observers.

I'm not claiming he worked out the relativity of simultaneity either (although he considered light to be tiny masses).

In any case, the point is this:

"Is time absolute or relative?" is a false dilemma. Everett's relative state formulation is an example of a theory where it helps to have multiple notions of time, including a type of time that exists as measurement records made by interal observers of the model.