Absolute and Relative Time

[hecd2]

Yes, basically the point is this:

Newton: I envision a universe with a world of absolute time and space, separated from the world of relative time and space by measurement. My math is for the absolute world.

Einstein: envision a universe with a world of absolute time and space, separated from the world of relative time and space by measurement. My math is for the relative world.

Everett: I envision a universe with a world of absolute time and space, separated from the world of relative time and space by measurement. My math describes the measurement, and thus both worlds.

Nonsense.

Newton's maths: t' = t
Einstein's maths: t' = 1/(1 - v^2/c^2)^1/2(t - vx/c^2) and t' = t(1-2GM/rc^2)^1/2 for Schwarzschild metric for example
Everett's maths: t' = ?

Furthermore, to ascribe to Einstein a belief in a world of absolute time and space which stands separate from his physics is utterly wrong.

 

[hecd2]

Illuminating.

What? Everett t = ? means that Everett has nothing to say about time in the sense of Newton and Einstein. There is no such thing as Everettian mechanics. If you think you know different give us the maths. t’ = what in Everettian mechanics?

And to say that Einstein envisions a physical world of absolute time and space separate from his physics is to be very mistaken. So enough with the religion already.

 

[Mike Helland]

What? Everett t = ? means that Everett has nothing to say about time in the sense of Newton and Einstein. There is no such thing as Everettian mechanics. If you think you know different give us the maths. t’ = what in Everettian mechanics?

Take a look:

https://mikehelland.github.io/everetts-observer/papers/everett.pdf

Jump to page 10.

And to say that Einstein envisions a physical world of absolute time and space separate from his physics is to be very mistaken.

That comes with the territory of being a Spinozan.

 

[hecd2]

Take a look:

https://mikehelland.github.io/everetts-observer/papers/everett.pdf

Jump to page 10.

Nothing about how time is affected by choice of reference frame there. So according to Everett t’ = ? If you don’t know or on reflection you reach the correct conclusion that he has nothing to say about the matter you’re allowed to admit it.

 

[Mike Helland]

Nothing about how time is affected by choice of reference frame there. So according to Everett t’ = ? If you don’t know or on reflection you reach the correct conclusion that he has nothing to say about the matter you’re allowed to admit it.

Each observer makes their observations from their own frame:

The symbols A, B, · · · , C, which we assume to be ordered time-wise, there-
fore stand for memory configurations which are in correspondence with the
past experience of the observer. These configurations can be regarded as
punches in a paper tape, impressions on a magnetic reel, configurations of a
relay switching circuit, or even configurations of brain cells. We require only
that they be capable of the interpretation “The observer has experienced
the succession of events A, B, · · · , C.” (We sometimes write dots in a mem-
ory sequence, · · · A, B, · · · , C, to indicate the possible presence of previous
memories which are irrelevant to the case being considered.)

The mathematical model seeks to treat the interaction of such observer
systems with other physical systems (observations), within the framework of
Process 2 wave mechanics, and to deduce the resulting memory configura-
tions, which are then to be interpreted as records of the past experiences of
the observers.

 

[hecd2]

Nothing about how time is affected by choice of reference frame there. So according to Everett t’ = ? If you don’t know or on reflection you reach the correct conclusion that he has nothing to say about the matter you’re allowed to admit it.

Each observer makes their observations from their own frame...
deduce the resulting memory configurations, which are then to be interpreted as records of the past experiences ofthe observers.

Nope, still nothing. There is nothing about reference frames there that you haven't put in.

 

[Mike Helland]

Nope, still nothing. There is nothing about reference frames there that you haven't put in.

Physical observers don't need to choose a reference frame.

They are a reference frame by virtue of being an observer.

In relativity, the theory has idealized observers.

In the relative state formulation, the theory has actually functioning observers. They don't "choose" their reference frame any more than a horse chooses is reference frame.

Here's some of DeWitt's comments on Everett's thesis:

http://ucispace.lib.uci.edu/handle/10575/1145

DeWitt sees parallels between the relative state formulation and relativity, in that by explicitly modeling the act of measurement, the reference frame is implicitly the frame of whoever is making said measurement.

 

[hecd2]

Physical observers don't need to choose a reference frame.

You don't? What are you, a tree or a rock?

They are a reference frame by virtue of being an observer.

Observers are not reference frames. Why do you insist on pontificating on subjects you know nothing about.

In relativity, the theory has idealized observers.

And how does that make a practical difference?

In the relative state formulation, the theory has actually functioning observers. They don't "choose" their reference frame any more than a horse chooses is reference frame.

Don't they? Perhaps that's because, so far as Everett's theory goes the reference frame of the observer is irrelevant. You don't understand the first thing about relativity or about Everett's interpretation of QM, which address entirely different problems and have zero, zilch, nothing to say about one another.

The time distinction between Newtonian mechanics and relativity is not a false dilemma as you would have it. It is real and there are consequences in the real world. Either most muons in air showers do not make it down to the Earth's surface before they decay or they do (they do make it). The travelling twin either has the same age as the stay at home twin on return or he hasn't (he hasn't). The lightcurves of Sn1a supernovae are either the same regardless of their speed or they differ (they differ). The speed of light either changes with velocity or it doesn't (it doesn't). We either don't need a correction for the speed of the satellites in GPS or we do (we do). Everett, in the relative state formulation, has nothing to say about these matters. I have invited you to quote Everett's maths that explains how time is to be treated under different circumstances (such as velocities or gravitational potential) and you have failed, and you will continue to fail because there is no such Everettian maths separate from relativity.

Even to suggest that relativity and classical mechanics on the one hand, and the measurement problem on the other hand, are addressing the same issues, is to display a profound ignorance of the lot.

Here's some of DeWitt's comments on Everett's thesis:

Quite irrelevant.

What is the point of this thread again?

 

[Mike Helland]

And how does that make a practical difference?

Let's try an example.

Imagine a physics model with a light source and two observers.

One observer 1 m from the light source, the other is 1 light second away.

The observers are machines. They each have a clock, a light sensor, a receipt printer. The machines are programmed to print the time whenever a pulse of light is detected. The observer's clocks are in sync at the beginning of the simulation, and they never move.

But there is nothing special, in the model, about the observers. They are made of pure physics, like a tree or a rock would be.

Everett tells us to ignore what we as external would see in the model, and instead inspect the observer's measurement records. We need to look at what's printed on the virtual paper in the receipt printer.

We should find that each of the observer's records differ by 1 second.

Agreed?

The time distinction between Newtonian mechanics and relativity is not a false dilemma as you would have it. It is real and there are consequences in the real world. Either most muons in air showers do not make it down to the Earth's surface before they decay or they do (they do make it). ...

Understood.

But that's not exactly the dilemma I'm referring to.

"Is time relative or absolute?"

Well, relative time is relative, and absolute time is absolute. That's tautological.

"Do the mathematics represent relative time or absolute time?"

In relativity, the answer is for sure, relative time. That's not a false dilemma. That is an important distinction to make.

Unless the mathematics can represent both, as the relative state formulation can.

What is the point of this thread again?

Simple. Newton defined relative time as a measurement. Everett implores to examine measurements made internally in the relative state formulation.

 

[Myriad]

Simple. Newton defined relative time as a measurement. Everett implores to examine measurements made internally in the relative state formulation.

"Examining measurements made internally" is a measurement.

 

[Mike Helland]

"Examining measurements made internally" is a measurement.

Eh.

If I asked, what's the force being applied to a mass of 1 kg being accelerated 1 m/s/s, you could say:

F=ma
F=1 kg * 1 m/s/s
F=1 newton

Then you say "1 newton". Is that making a measurement? You're reading off a page.

You could saying you're measuring the information on the page, if you really wanted to I suppose. But you're really just making a prediction from a model.

Likewise, in most physics models on a computer, when we want to make a prediction, we read a value off the screen, a value stored in memory.

What Everett is saying is that's not enough. The values stored in memory make up the particles that form a second type of memory (Everett uses punches in tape and brain cells as examples) and this is where the predictions of the model are stored, as past experiences of the observers.

 

[Ziggurat]

Eh.

If I asked, what's the force being applied to a mass of 1 kg being accelerated 1 m/s/s, you could say:

F=ma
F=1 kg * 1 m/s/s
F=1 newton

Then you say "1 newton". Is that making a measurement? You're reading off a page.

You could saying you're measuring the information on the page, if you really wanted to I suppose. But you're really just making a prediction from a model.

Not really. F=ma isn't really a model, it's really a definition. And yes, actually, the distinction matters. Force is defined as mass times acceleration. Using this definition, if you measure mass as 1 kg and acceleration as 1 m/s², then you aren't predicting the force. The force is defined by the mass and acceleration. Given this definition of what force means, you can only be wrong if you measure the mass or the acceleration (or both) wrong.

A prediction involving force would be something that tells you what the force will be without having to measure mass and acceleration. For example, F=Gm₁m₂/r² is a model for the force of gravity. Measure the masses and the separation distance, and it will predict the force of gravity. The prediction can be wrong if this model of gravity is wrong, even if you measure your masses and separation distance correctly.

 

[Mike Helland]

Not really. F=ma isn't really a model, it's really a definition.

https://physics.stackexchange.com/q...nman-mean-when-he-says-that-f-ma-is-not-exact

"In fact the law, 𝐹=𝑚𝑎 is not exactly true; if it were a definition we should have to say that it is always true; but it is not ... First, because Newton's Second Law is not exact, and second, because in order to understand physical laws, you must understand that they are all some kind of approximations. "

That said, doing calculations isn't really the same as doing a measurement.

The idea is that our models make predictions, and we compare them to actual measurements.

Everett's idea is for the model's predictions to be based on the records of mechanical observers inside the model.

 

[W.D.Clinger]

Elaborating upon hecd2's response...

Physical observers don't need to choose a reference frame.

They are a reference frame by virtue of being an observer.

In relativity, the theory has idealized observers.

No. No. No.

Saying an observer is "a reference frame by virtue of being an observer", as Mike Helland did above, is an easy way to confess profound ignorance of special relativity.

In special relativity, a reference frame is a Minkowskian coordinate system.

Human observers often choose to assume they are at rest, which constrains the reference frame they are choosing to use. That choice is already a choice, but that choice does not fully determine their choice of reference frame, since they must still choose the directions of spatial dimensions and the absolute (as opposed to relative!!!) time of some event they experience.

Human observers are also free to choose reference frames in which they are not at rest. Such choices are especially likely when a human observer sees objects flying past that the observer is accustomed to regarding as fixed in place, such as trees, houses, fire hydrants, et cetera.

In the general theory of relativity, an observer's choice of "reference frame" becomes an even freer choice (for multiple reasons, including the fact that charts covering the distinguished observer at some distinguished time are not constrained to be Minkowskian). Many connotations of "reference frame" no longer hold in general relativity, which is why informed people try to avoid that phrase when discussing general relativity.

 

[theprestige]

Don't we already have a whole-ass thread about Mike's reference frame and observer shenanigans?

 

[Ziggurat]

"In fact the law, 𝐹=𝑚𝑎 is not exactly true; if it were a definition we should have to say that it is always true; but it is not ... First, because Newton's Second Law is not exact, and second, because in order to understand physical laws, you must understand that they are all some kind of approximations. "

If it's a definition, it IS exact. By definition. See how that works?

The Newtonian definition of force has been superseded by a more modern definition of F=dp/dt. But there really isn't any definition of force other than these.

That said, doing calculations isn't really the same as doing a measurement.

Sure.

The idea is that our models make predictions, and we compare them to actual measurements.

OK.

Everett's idea is for the model's predictions to be based on the records of mechanical observers inside the model.

And... that's got what to do with absolute/relative time?

 

[Mike Helland]

Human observers often choose to assume they are at rest, which constrains the reference frame they are choosing to use.

Humans have historically considered the Earth at rest (if they even considered it something movable at all).

Most people that have ever lived have never heard of inertial frames, and seemed to get by just OK.

But if I choose to identify at rest, or in motion, does my wrist watch run any different?

That choice is already a choice, but that choice does not fully determine their choice of reference frame, since they must still choose the directions of spatial dimensions and the absolute (as opposed to relative!!!) time of some event they experience.

How do they determine the absolute time of some event?

Did you mean proper time, perhaps? Because that's still relative (as opposed to absolute).

 

[Mike Helland]

And... that's got what to do with absolute/relative time?

In the relative state formulation, there are observers that make measurements and store records of them. If those measurements are of time, then they fit Newton's definition of relative time. If they are of distance, they fit Newton's definition of relative space.

By including mechanical observer's that produce record measurements, Everett has made a model that has an absolute state (our view of the model, from the outside) and a relative state (the observer's view from the inside).

Everett's observer's measurement records seem to sound exactly like how Newton defined relative time and space.

 

[hecd2]

And how does that make a practical difference? ("that" is Mike's claim that relativity uses idealised observers)

Let's try an example.

Imagine a physics model with a light source and two observers.

One observer 1 m from the light source, the other is 1 light second away.

The observers are machines. They each have a clock, a light sensor, a receipt printer. The machines are programmed to print the time whenever a pulse of light is detected. The observer's clocks are in sync at the beginning of the simulation, and they never move.

But there is nothing special, in the model, about the observers. They are made of pure physics, like a tree or a rock would be.

Everett tells us to ignore what we as external would see in the model, and instead inspect the observer's measurement records. We need to look at what's printed on the virtual paper in the receipt printer.

We should find that each of the observer's records differ by 1 second.

Agreed?

Of course (ignoring for a moment the non-trivial problem of how the clocks get synchronised in the first place, which is why it's better to ask for the interval according to the observer's clocks between two pulses emitted a fixed interval apart in the reference frame of the source) and would be true whether the observers are mechanical or human beings. In the scenario you set out, and using my suggested observation they both observe the same interval. Einstein tells us the correct answer here, not Everett.

Einstein also tells us what these observers would record if one of them was moving at, say, c/2 with respect to the the other one and the light source. Their records would no longer differ by a second (or if we use intervals, they would no longer observe the same interval). Einstein tells us that, not Everett.

So when you claim that relativity uses idealised observers, you still haven't told us how that makes a practical difference.

Unless the mathematics can represent both, as the relative state formulation can.

You keep saying that, but you never show us what these mathematics that represent both are, and you never will, because no such maths exists. The relative state formulation is not trying to solve the problem you think it is. To understand the problem it is trying to solve, you need to understand QM to at least graduate level. And you don't. It is not saying anything about the physics of time as addresssed by Einstein in relativity. It really, really isn't.

What is the point of this thread again?

Simple. Newton defined relative time as a measurement.

No he didn't. Newton had no concept of relative time in the sense that Einstein has. Newton believed in an absolute time which is universal and flows independent of things and events in the world, the passage of which can be measured imperfectly by clocks, astronomical phenomena and other events. Einstein showed that there is no such universal and absolute time. It is a hard distinction. It has real physical consequences. There is no absolute time.

Everett implores to examine measurements made internally in the relative state formulation.

No, he doesn't. Everett is not "imploring" us to do any such thing. He is trying to find an alternative to the Copenhagen interpretation of measurement of a quantum variable as a collapse of the superposition of states to a single definite state, by considering the change of the quantum state of the measurement mechanism (which could be a person). He has nothing to say about time as it appears in the theory of relativity in his thesis.

You fundamentally misunderstand Newton, Einstein and Everett. In just about every way possible.

 

[hecd2]

In the relative state formulation, there are observers that make measurements and store records of them. If those measurements are of time, then they fit Newton's definition of relative time. If they are of distance, they fit Newton's definition of relative space.

By including mechanical observer's that produce record measurements, Everett has made a model that has an absolute state (our view of the model, from the outside) and a relative state (the observer's view from the inside).

Everett's observer's measurement records seem to sound exactly like how Newton defined relative time and space.

You can make any argument you like to your own satisfaction, if you don't understand the concepts you are discussing and you make up private definitions for key words.