The Nature of Time

[Mordred]

6 minutes ago, Markus Hanke said:

Have a look at the following situation: this is a plot of a 3-cube that has evolved in time, but instead of using a time axis, the evolution is all plotted on the same 3D volume to just reflect “movement” (as you suggest), without reference to an external “time” at all. The movement/change here is a combination of rotations (angle not necessarily constant, and rotations not necessarily in the same direction), and a change in colour.

Without being given any information other than points within that the same 3D volume (ie only the above picture), can you tell me what the initial state of this system is, and how it evolves? What in here corresponds to past, present, future? You can’t do this, unless additional information is provided that is not itself an element of this same 3D volume.

I think you can see the issues. And this is an idealised evolution in just three discrete steps - real-world systems, especially classical ones, feature continuous evolutions, with rotations around all three axes. Try to plot that into a single 3D volume, and what you’d get in the continuum limit is a solid ball - you couldn’t even tell the original shape any more.

On the other hand, if you were to plot the evolution of the above system on a clearly labelled time axis with separate 3D plots at t=1,2,3, then there are no ambiguities at all - you can tell exactly what the original state was, and how it evolved in time.

 

I like your example it also does an excellent job of showing degrees of freedom with the rotations etc. +1

Edited January 8, 2023 by Mordred

[Genady]

23 minutes ago, Lorentz Jr said:

In relativity, ... and the flow of time is considered to be an illusion

Where? Reference?

[mistermack]

2 hours ago, Mordred said:

Time we give dimension of length by the interval (ct) the distance light travels in one second.

Yes, but if you spin that around, then one second is the time for light to travel that distance. So your unit of time is produced by a phyical change, in the three dimensions of space. 

 

2 hours ago, Markus Hanke said:

On the other hand, if you were to plot the evolution of the above system on a clearly labelled time axis with separate 3D plots at t=1,2,3, then there are no ambiguities at all - you can tell exactly what the original state was, and how it evolved in time.

Yes, but if you do that, you are assuming a clock, and that clock is essentially no difference to the system you are modelling, ie a physical change in 3 dimensions. So you are plotting one system against another similar one, not introducing an extra dimension. I'm not saying that there's anything wrong in portraying time as a dimension, for the sake of the model. 

[Genady]

Quote

In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it

(Dimension - Wikipedia)

To specify an event, we need 4 coordinates. Thus, a space of events is 4 dimensional. These dimensions are 3 spatial and 1 temporal coordinates. I think it is this straightforward.

[mistermack]

2 hours ago, Genady said:

To specify an event, we need 4 coordinates. Thus, a space of events is 4 dimensional. These dimensions are 3 spatial and 1 temporal coordinates. I think it is this straightforward.

Yes but the fact is that when you specify a past event, you are by definition describing something that no longer exists. You need time to describe a non-existant past situation, and the same applies to predicting an event. 

So what you need time for, is to model the past or future which don't exist. What does exist is an ever  changing present. 

[Genady]

As I see it, past exists in the past, future exists in the future, and whatever exists now exists in the present. If one defines 'exists' as existing necessarily now, then it leads to a contradiction, by definition, but I don't see a justification to this kind of definition.

[mistermack]

42 minutes ago, Genady said:

As I see it, past exists in the past, future exists in the future, and whatever exists now exists in the present. If one defines 'exists' as existing necessarily now, then it leads to a contradiction, by definition, but I don't see a justification to this kind of definition.

I see it as the opposite. The past exists only in the conditions of the present, and the future will only happen as a result of the conditions of the present. Even if you ignore random variation, and claim that every detail of the future is inevitable, it's still stretching it to say that something exists 'in the future'. 

[iNow]

The problem is the present doesn’t even exist. By the time we sense a “now,” it’s already a stale outdated shadowy construction of lots of different past stimuli and variables.  Some of those inputs are 300ms old, others are 700ms old, some others still are from light that was emitted from a star 2 billions years ago… all stitched haphazardly together via a wet meat computer into a narrative we call “reality.”… but it’s not “now.” That happened at least 300-700ms ago. 

Edited January 8, 2023 by iNow

[Genady]

Exactly: 'now' is ill-defined and a notion of 'exists' that is attached to 'now' is thus ill-defined.

Inevitable or not, there is only one factual future. That's why I think it is meaningful to say about an event that it exists or doesn't exist in the future.

[studiot]

48 minutes ago, iNow said:

but it’s not “now.” That happened at least 300-700ms ago. 

Not so far as the light we are seeing is concerned it didn't.

[Mordred]

1 hour ago, iNow said:

all stitched haphazardly together via a wet meat computer 

Lmao now there's an expression to deflate one's ego lmao

[Lorentz Jr]

1 hour ago, iNow said:

The problem is the present doesn’t even exist. By the time we sense a “now,” it’s already a stale outdated shadowy construction of lots of different past stimuli and variables.

You're confusing physics with biology. Regardless of how long it takes us to perceive things, and regardless of how inaccurate those perceptions may be, we can still reasonably infer that something existed some time ago to cause those perceptions, and from our memory of past perceptions, we can reasonably infer that the past state(s) of the world around us probably led to a current state that exists now and will probably lead to more perceptions for us at some time(s) in the future.

Edited January 8, 2023 by Lorentz Jr

[iNow]

2 hours ago, studiot said:

Not so far as the light we are seeing is concerned it didn't.

Please elaborate. 

1 hour ago, Lorentz Jr said:

You're confusing physics with biology.

Promise you I’m not. 

1 hour ago, Lorentz Jr said:

we can still reasonably infer that something existed some time ago to cause those perceptions, and from our memory of past perceptions, we can reasonably infer that the past state(s) of the world around us probably led to a current state that exists now and will probably lead to more perceptions for us at some time(s) in the future.

This misunderstanding seems to have been yours since this isn’t relevant to what I said 

[Lorentz Jr]

2 hours ago, Lorentz Jr said:

we can still reasonably infer that something existed some time ago to cause those perceptions, and from our memory of past perceptions, we can reasonably infer that the past state(s) of the world around us probably led to a current state that exists now and will probably lead to more perceptions for us at some time(s) in the future.

56 minutes ago, iNow said:

This misunderstanding seems to have been yours since this isn’t relevant to what I said 

You said "the present doesn’t even exist" based on the idea that it takes "300-700ms" for "a wet meat computer" to "sense" it.

The misunderstanding seems to have been yours since your comment isn't relevant to the topic.*

 

* (or, more precisely, the premise of the comment isn't relevant to the conclusion.)

Edited January 9, 2023 by Lorentz Jr

[geordief]

Are there any instances in the history  of science where  a   change in appreciation  of the nature of time has given rise to a significant  advance in the realm of practical  technological achievement?

 

If there is might that indicate that the  new appreciation of the phenomenon of time  was superior to the old (if only in terms of probability)?

 

Would the instance that stands out be  the Minkowski  spacetime model?

 

I don't include the greater and greater precision in timekeeping that has occured down the ages**  as an example .I mean  a change in appreciation of the concept.

 

**the latest interpretation of the animals in cave drawings as applied to the "hunting seasons" and  very recently   published is fascinating. 

https://www.livescience.com/ice-age-cave-art-proto-writing-claim

 

Edited January 9, 2023 by geordief

[Genady]

I am not sure what

17 minutes ago, geordief said:

a   change in appreciation  of the nature of time

means, but I know of only one instance in the history of science pertaining to a change in understanding of time. I.e., from Newtonian time to SR time. Or, more specifically, from Newtonian simultaneity to simultaneity in SR.

[geordief]

@Genady (can't get the quote function to work) ,I used "appreciate" as "understand" sounded too final ,too presumptuous.

Otherwise ,you can only think of that one instance?Me too.

 

If its practical impact was so strong then that seems to me that we have a kind of  Sigma 5 discovery   on our hands and ,to date that is probably  where our correct understanding of the nature of time lies.

 

Not that we will ever stop asking this question ,I suspect and presumably we should expect further enlightenment if and when we make progress on quantum gravity.

Edited January 9, 2023 by geordief

[iNow]

59 minutes ago, geordief said:

Are there any instances in the history  of science where  a   change in appreciation  of the nature of time has given rise to a significant  advance in the realm of practical  technological achievement?

GPS

1 hour ago, Lorentz Jr said:

You said "the present doesn’t even exist" based on the idea that it takes "300-700ms" for "a wet meat computer" to "sense" it.

I see. Please tell me where exactly in our universe we can measure “now.”

[Lorentz Jr]

  

23 minutes ago, iNow said:

Please tell me where exactly in our universe we can measure “now.”

There's no such thing as "measuring now", any more than measuring "yesterday" or measuring "tomorrow". You can measure anything that can be measured, and you can measure it anywhere in the universe you can get to. If you measure it "now", you'll perceive it "300-700ms" later, and whatever you're perceiving "now" happened "300-700ms" ago.

If you measure something that was caused by some other event that occurred more than one light-day ago, you may even be measuring evidence of something that happened a day earlier, but you're still measuring properties that physical systems have at the time you measure them, not "measuring now" or "measuring yesterday".

The biology of human perception has no direct connection with the physics of time.

Edited January 9, 2023 by Lorentz Jr

[swansont]

9 minutes ago, Lorentz Jr said:

There's no such thing as "measuring now". You can measure anything that can be measured, and you can measure it anywhere in the universe you can get to. If you measure it "now", you'll perceive it "300-700ms" later, and whatever you're perceiving "now" happened "300-700ms" ago. The biology of human perception has nothing to do with the physics of time.

Except for the timing delays that you acknowledge. You account for them in physics experiments when relevant, e.g. coincidence measurements or delay lines. The fact that they are biological instead of copper or fiber optic doesn’t mean that physics isn’t involved. Signal delay is signal delay.

 

[iNow]

13 minutes ago, Lorentz Jr said:

The biology of human perception has no direct connection with the physics of time.

My point remains valid even when human perception is subtracted. 

Edited January 9, 2023 by iNow
Pyto

[Lorentz Jr]

2 minutes ago, swansont said:

The fact that they are biological instead of copper or fiber optic doesn’t mean that physics isn’t involved. Signal delay is signal delay.

That's true, but the technicalities of signal propagation still don't prove that the word "now" has no meaning, regardless of whether they're organic or inorganic. Even in relativity, any given observer can construct a model of their surroundings at t=0. For example, if we determine that some nearby star was at a point in its life cycle where it was about to go nova when it emitted the light that we just received recently, we may conclude that the nova has occurred by now and we can expect to detect it fairly soon. And this is the Speculations area, so we're not even limited to the relativistic model.

13 minutes ago, iNow said:

My point remains valid even when human perception is subtracted. 

Your point remains ambiguous, because you haven't backed it up with a single word of supporting logic or evidence.

[swansont]

1 minute ago, Lorentz Jr said:

That's true, but the technicalities of signal propagation still don't prove that the word "now" has no meaning, regardless of whether they're organic or inorganic. Even in relativity, any given observer can construct a model of their surroundings at t=0. For example, if we determine that some nearby star was at a point in its life cycle where it was about to go nova when it emitted the light that we just received recently, we may conclude that the nova has occurred by now and we can expect to detect it fairly soon.

There’s a reason why we use “t=0” rather than “now”

 

1 minute ago, Lorentz Jr said:

And this is the Speculations area, so we're not even limited to the relativistic model.

You appear to have a fundamental misunderstanding of the rules of speculations

[iNow]

6 minutes ago, Lorentz Jr said:

Even in relativity, any given observer can construct a model of their surroundings at t=0.

Which is just moving the goalposts. 

[iNow]

7 minutes ago, Lorentz Jr said:

you haven't backed it up with a single word of supporting logic or evidence.

We seem to have different definitions of “a single word or supporting logic.”

1 minute ago, Lorentz Jr said:

At the point in time when I set a clock to zero, t=0 corresponds to "now".

“Now” you’re just making stuff up.