Absolute and Relative Time

[Robin]

Metaphysically speaking, it is doubtful that Newton believed in absolute time because he was a Christian and a Christian of the time would almost certainly have believed the Augustinian notion of time being a created part of the universe and that there was no such thing as "before" the creation. He would probably have believed in a Boethius/Aquinas notion of God existing in a context that had no succession and therefore no time.

His remarks on absolute and relative time come in the definitions section and remove any ambiguity between time as it is used in the equations and time as it is measured by an observer.

His model has an absolute time in the sense, as remarked on earlier in this thread, that translations between frames don't change the time. No doubt he believed that the natural universe worked in this way since these equations clearly worked.

 

[Steve001]

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.

It is relative; experiments clearly show it to be so.

 

[Robin]

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.

But this is really just the distinction that Newton is making, and that Einstein also makes. Einstein talks of an observer using a mirror to observe to lightning strikes and seeing them at the same "time" (observer time) and being able to define simultaneity and "time" (as an objective part of the equations) from this.

This is different to the distinction between absolute and relative in the sense that time is relative in the theories of relativity.

 

[hecd2]

In any case, the point is this:

"Is time absolute or relative?" is a false dilemma.

If that’s your point, the entire thesis of this thread is wrong. It’s not a false but a real dilemma. Either time is invariant under change of reference frame or it’s not. How can that be a false dilemma? As it turns out, time is not invariant under boosts or rotations. Nor under acceleration or in different gravitational potentials.

 

[Robin]

We can have "relative" time in the sense that my definition of a day might differ from your definition of a day (which is the example given by Newton) or that the mechanism of my clock might run faster than yours because of differences in the manufacture.

And then there is "relative" time in which twins accelerating away and then towards each other will have different ages.

And there is "absolute" meaning that all translations between frames will preserve duration.

And there is "absolute" meaning that there is an objective way for all observers to agree on duration using the appropriate equations and translations.

So, depending on your meaning, there might be absolute time (in the second sense of absolute) that is also relative time (in the second sense of relative).

 

[Mike Helland]

And there is "absolute" meaning that there is an objective way for all observers to agree on duration using the appropriate equations and translations.

It's easy to fall into the trap of thinking "absolute = objective" and "relative = subjective", but that's a mistake.

You and I can objectively measure the height of a building in meters. Height is a distance, in relative space. Nothing absolute about it.

Objective measurements tell us about relative space and relative time. They are the opposite of absolute.

 

[hecd2]

So what is your point? Is there one?

 

[Robin]

It's easy to fall into the trap of thinking "absolute = objective" and "relative = subjective", but that's a mistake.

You and I can objectively measure the height of a building in meters. Height is a distance, in relative space. Nothing absolute about it..

Objective measurements tell us about relative space and relative time. They are the opposite of absolute.

Only if you are using "absolute" in the first sense I have defined above.

The trap that is easy to fall into is thinking that words have one and only one meaning. That is what I am pointing out

If a.Martian says "half a day" that might be "relative" to the rotation of Mars, but that is different to "relative" as used in relativity.

By his examples Newton appears to be using "relative" in the first sense especially as he seems to use "sensible time" (time as apprehended by the senses) as a synonym, and thus closer to what Einstein called observer time.

As I pointed out earlier it is unlikely in any case that Newton believed in a metaphysical absolute time because he was a Christian and believed that the universe had a beginning and will have an end and probably subscribed to the mainstream Christian view of God as a timeless entity.

 

[Robin]

So what is your point? Is there one?

His point, unless I am mistaken, is that the common view of what Newton believed about time is simplistic and should be updated in line with the more sophisticated view that Newton actually expressed.

That seems a point worth making.

 

[hecd2]

His point, unless I am mistaken, is that the common view of what Newton believed about time is simplistic and should be updated in line with the more sophisticated view that Newton actually expressed.

That seems a point worth making.

What Newton believed about time seems to be perfectly expressed in his physics. I don't think that that is either misunderstood or simplistic. I don't think there is any further sophistication to be wrung out there. The fact that Newton points out that the common person's subjective perception of time differs from what he means by time in his physics is clear and does not appear to be the point Mike is trying to make.

Mike says: "In any case, the point is this: 'Is time relative or absolute is a false dilemma.'" Well it isn't a false dilemma when it comes physics.

You might not remember the long and tedious thread in which he argued endlessly through countless elementary errors of physics and maths for his private theory of redshift, which petered out when he proposed that photons have two clocks running at different rates (or something like that - it's hard to remember the details), but I wouldn't be surprised if that's where we're headed. If it isn't, there seems no point to all of this.

 

[Crossbow]

That's concerning because I don't remember saying that, nor do I hear voices which would prompt me to say that.

Do you have a source?

Or did you just make that up?

Sorry about that!

That was my mistake. I got you confused with another poster here on the Forum.

I do apologize for and retract my very incorrect comments.

 

[Ziggurat]

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

That isn't what makes time "relative" in the sense that makes special relativity difference from Newtonian physics.

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

Oh, but he is, even if not in that sentence. What you reference is basically an admission that clocks of the day weren't that good.

It's quite common for people to not understand relativity. But it's rather unusual to come across someone who does not understand Newtonian physics.

 

[Mike Helland]

His point, unless I am mistaken, is that the common view of what Newton believed about time is simplistic and should be updated in line with the more sophisticated view that Newton actually expressed.

That seems a point worth making.

Thank you!

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.

Common people: there is only one world, the one we observe. And we have a measurement problem.

hecd2 is mistaken that this has anything to do with cosmology.

 

[theprestige]

Common people don't have a measurement problem, though. Common people aren't even really thinking that hard about whatever Newton was actually getting at. Or even aware of it. There's no record to correct, since the actual record of Newton's work is already correctly described, and readily accessible to anyone who cares to dig into it.

Also the question of an absolute frame of reference for time has everything to do with cosmology.

 

[Mike Helland]

That isn't what makes time "relative" in the sense that makes special relativity difference from Newtonian physics.

Einstein didn't invent the word "relative", or even give it a new meaning.

It means, and always has, through relation to other things, not standalone (absolute), and has a very long history:

"Absolute and Relational Space and Motion: Classical Theories"

https://plato.stanford.edu/entries/spacetime-theories-classical/

What you reference is basically an admission that clocks of the day weren't that good.

That's part of it, of course.

The idea that his perfect, true, mathematical time corresponding to 17th century time pieces was probably laughable to him.

 

[Robin]

What Newton believed about time seems to be perfectly expressed in his physics. I don't think that that is either misunderstood or simplistic.

If you think the discussion in the Scholium amounts to "Newton points out that the common person's subjective perception of time differs from what he means by time in his physics" then I think you have absolutely missed the point of it.

 

[Mike Helland]

If you think the discussion in the Scholium amounts to "Newton points out that the common person's subjective perception of time differs from what he means by time in his physics" then I think you have absolutely missed the point of it.

It should be noted that even at the time, Leibniz was like "no, no, amigo, your equations are about relative motion."

(Not a disagreement, just more context.)

 

[Mike Helland]

That isn't what makes time "relative" in the sense that makes special relativity difference from Newtonian physics.

May I offer this as a resolution:

"Time is relative" and "time is relativistic" mean two different things.

Relative meaning by relation to something else, and relativistic by invoking Einstein's theory of relativity.

Consider if Einstein named his theory something else, like the theory of spacetime invariance. I think Minkowski coined "spacetime" after the theory of relativity became known, so I know that's not likely.

But say Einstein named his theory in honor of Lorentz, and called it the theory of Lorentzitivity.

Then, when people heard "time is relative" and "time is lorentzitive", they wouldn't be inclined to confuse the two.

Also, I offer that because "relative" and "relativity" go so hand and hand these days, that the de facto meaning of "relative" is to refer to the theory of relativity, then I acknowledge I am going against the grain and being somewhat pedantic.

 

[hecd2]

If you think the discussion in the Scholium amounts to "Newton points out that the common person's subjective perception of time differs from what he means by time in his physics" then I think you have absolutely missed the point of it.

His point is perfectly described by the fact that there is an absolute time independent of the vagaries of physical clocks for which t' = t under all transformations. That's all that I and V of the Scholium have to say about the matter. So yes, that is exactly what the discussion in the Scholium amounts to.

 

[Ziggurat]

May I offer this as a resolution:

"Time is relative" and "time is relativistic" mean two different things.

Relative meaning by relation to something else, and relativistic by invoking Einstein's theory of relativity.

Consider if Einstein named his theory something else, like the theory of spacetime invariance. I think Minkowski coined "spacetime" after the theory of relativity became known, so I know that's not likely.

But say Einstein named his theory in honor of Lorentz, and called it the theory of Lorentzitivity.

Then, when people heard "time is relative" and "time is lorentzitive", they wouldn't be inclined to confuse the two.

Also, I offer that because "relative" and "relativity" go so hand and hand these days, that the de facto meaning of "relative" is to refer to the theory of relativity, then I acknowledge I am going against the grain and being somewhat pedantic.

You are being pedantic, but you aren’t even doing a good job at it. So let’s do a better job at it.

In Newtonian physics, coordinate time is relative to your choice of a zero. It is not relative to your choice of inertial reference frames. Times between events are absolute.

In special relativity, coordinate time is relative to both your inertial reference frame and your choice of a zero. Times between events are also relative to your choice of coordinate frame, but not to your choice of a zero.