'Time' is a metric of asymmetric change (i.e. physical transformations) ... — 180 Proof

In fact, we have exactly the same idea, but differently worded. Maybe I should look for new ideas... :kiss:

I think thermodynamic time Is constituted the irreversible processes. You can quantify these processes by putting a clock besides them. — EugeneW

:up: The passage from Aristotle that you brought in is very interesting. It's a very long time I have not read Aristotles --since school maybe-- and I enjoyed it!

what Aristotle is basically saying is that time is change — Kuro

This is what I also believe and often mention in discussions. More specifically, that time is our measurement of and reference to change, including movement in space.

So if the universe changes from "no-time" to "time", that in of itself is a temporal process, making it necessary that "no-time" is actually time. So time never begins. — Kuro

Well, this could be a very good point if its description had no some weaknesses:
1) The universe cannot change from "no-time" to "time". but from non-existence to existence.
2) A "process" is a series of actions or steps taken in order to achieve a particular end. So what we are talking here is an event. (Re: Hawking's singularity)
3) For something to change, it must already exist. So, we cannot talk about change, transition or whatever from non-existence to existence.
4) The element of temporariness could well be missing, since it is disputable and not necessary to prove that "time never begins".

So, the main argument for the thesis that time never begun or it is eternal, can put it in this way: "If we assume time's existence from non-existence, i.e. that it has been created from nothing, there should be a point at which this has happened. But this "point" can only refer to time. This creates a " circularity" or impossibility.
A second way is this: Something cannot be created from nothing. There is always a source of creation, a cause that creates something. And that, cannot be "nothing".
There are certainly a lot of ways to prove this thesis.

How can there be any time without the existence of motion? — Kuro

Traffic lights make a nice example of time without motion. Just the regular color changes are enough. And yet time itself is not defined by change, since the air pressure changes with altitude, which is change without time.

But so far as time is concerned we see that all with one exception are in agreement in saying that it is uncreated

I don't see an exception. The process of creation is temporal by definition, so while I have no problem with time being bounded, it seem a contradiction to apply the concept of creation or destruction to time. There are valid solutions to Einstein's field equations with bounded time, such as white and black holes.

I know certain things by acquaintance - a headache, an acrid smell, the colour red, a sweet taste, a screeching noise. I know other things by description - Aristotle, Sherlock Holmes, a unicorn.

I cannot know time by acquaintance, as "We can only experience the moment we are in. We cannot experience at this moment either the moment before this moment or the moment after this moment. Therefore, we can never directly experience either the past or the future."

I can only know time by description.

As Aristotle, as well as everyone else, only knows time by description and not acquaintance, his conclusion that time is eternal and without beginning must remain a hypothesis, interesting, but still an unprovable hypothesis.

Time Never Begins

But it's Saturday 19^th March, 2022.

Take that, Pembroke scholars!

Aristotle used this to forward the conclusion that the universe is eternal. — Kuro

The conclusion is not so simple, because the argument you presented must be taken within the proper context. Notice that the paragraph closes with a conditional statement: "But if this is true of time, it is evident that it must also be true of motion, time being a kind of affection of motion." So he then proceeds to question the idea of eternal motion. He concludes that there must be a first mover which is not itself moved, and this denies the possibility of eternal motion. The unmoved mover implies that there is something outside of motion and time, so "eternal" is given that meaning, outside of time, and infinite motion, as well as infinite time, are rendered as incoherent.

now famous words of butimfeeling2022: "over and over again" — EugeneW

OK player. Nah, you ain't funny yet.

Haha! You read it too?

Aristotle is arguing first that motion in the universe is everlasting and second that the motion we observe in the world must have its primary cause in something that cannot be in motion, a first immaterial "unmoving mover".

He writes at the end of section 5 of Physics Book 8 - "From what has been said, then, it is evident that that which primarily imparts motion is unmoved: for, whether the series is closed at once by that which is in motion but moved by something else deriving its motion directly from the first unmoved, or whether the motion is derived from what is in motion but moves itself and stops its own motion, on both suppositions we have the result that in all cases of things being in motion that which primarily imparts motion is unmoved."

The question is, are his premises sound and his his argument valid ?

As @Metaphysician Undercover pointed out, the paragraph in the OP has been taken out of context.

Aristotle's inference of a spiritual rather than physical explanation for an "unmoving mover" may be brought down to earth.

1) Imagine a rock travelling through space at 10,000 km/hour. In Aristotle's terms, where is the unmoving mover that keeps the rock travelling forwards at a constant speed ? How to explain the Law of Conservation of Energy, whereby the kinetic energy of the rock is maintained ?
However, motion is relative, and we may consider the rock as stationary within a moving environment. In this case, the rock being stationary, no unmoving mover is needed, and the existence of an unmoving mover is not required.

2) Imagine the same rock in distant space. Movement is not a property of a single body, but is a property that emerges when more than one body are in near location, whether the gravitational force between the moon and the Earth or the magnetic attraction between two magnets. If another body approaches this particular rock, the paths of the bodies will be changed by a gravitational attraction.
In this case, the primary mover is gravity, which may be understood as a curve in space, and in Aristotle's terms, an unmoving mover

In summary, in both cases, it is not necessary to consider a mysterious entity outside the known universe, in that the "mover" can be explained as a physical state of affairs within current time and space.

In summary, in both cases, it is not necessary to consider a mysterious entity outside the known universe, in that the "mover" can be explained as a physical state of affairs within current time and space. — RussellA

But what brought space and time into being?

But what brought space and time into being? — EugeneW

Aristotle in Physics Book 8 claims that motion is everlasting, has no beginning and will have no end.

And yet he discusses the "unmoved mover", where "the first movement is moved but not by anything else, it must be moved by itself"

Although his "unmoved mover" has been identified with a spiritual explanation, Aristotle in Physics Book 8 doesn't explain its nature.

Today, this "unmoved mover" can be explained in more scientific terms, without the need to address what brought space and time into existence.

Today, this "unmoved mover" can be explained in more scientific terms, without the need to address what brought space and time into existence. — RussellA

I think virtual particles on a central singularity are the first unmoved mover, in the scientific sense. They don't move unidirectional in time and resemble the eternal circular motion, which has no direction in time too. They fluctuate up and down in time to be kicked forward and realized by a surrounding giving a sign. When inflated into real, their evolution backfired to the singularity, the virtual source, to bring on a new inflation. But where did this infinite cycle come from?

Time cannot exist without change
— Harry Hindu

But only in space they can change. — EugeneW

Space changes too.

In other words things change relative to each other. The relationship between one change and another is time.
— Harry Hindu

In other words, things can oscillate in time, like virtual particles in the vacuum, or have a timelike direction, like virtual particles turned real. — EugeneW

I don't know what "in time" means. Oscillations are changes. How fast (how much time) does one thing oscillate? You have to compare it to another change to find out. Time is the comparison of change. The direction of some change only manifests itself when comparing the change to another change.

Space changes too. — Harry Hindu

Yes. And both the changing of the metric and real particles moving asymmetrically (thermodynamically, irreversibly) constitute time. Thermodynamic time. The virtual motion of virtual particles on the pre-inflationary era constitutes the non-directional, fluctuating time. A perfect pendulum, an eternal circular motion of which you can't say it's going back or forth. It's going to and fro, waiting for the right circumstances to kickstart it in one direction. Or better, two. The universe and a mirror version. But the wait is timeless in the sense of having no direction yet. The big mystery is why it all doesn't have the opposite direction. And another mystery is who brought this eternal sequence of big bangs, with two ensuing universes, into existence.

don't know what "in time" means. Oscillations are changes. How fast (how much time) does one thing oscillate? You have to compare it to another change to find out. Time is the comparison of change. The direction of some change only manifests itself when comparing the change to another change. — Harry Hindu

The period time is a Planck time. The amplitude a Planck length. That's the maximum length the virtual particles had to oscillate. They don't oscillate in time but constitute time themselves. If you hold a virtual clock beside it though, you would see the hand of that clock go back and forth.

there must be a first mover which is not itself moved — Metaphysician Undercover

Ouroboros? I eat and I eat and I eat and I eat...myself.

Today, this "unmoved mover" can be explained in more scientific terms, without the need to address what brought space and time into existence. — RussellA

If we would consider the omnipresent virtual particle fields residing in the vacuum of nature the eternal unmoved prime mover, we would still be left with the question where that came from.

If we would consider the omnipresent virtual particle fields residing in the vacuum of nature the eternal unmoved prime mover, we would still be left with the question where that came from. — EugeneW

Aristotle
Aristotle's answer would be that the universe is eternal having never come into existence. His is not the God of Genesis who created the world out of nothing.

But the universe is in eternal motion, and for Aristotle the universe needs a cause for its continuing existence and motion, and that cause is a God, outside the world, changeless and immaterial.

Aristotle's theology is set out in books VII and VIII of Physics and book XII of Metaphysics

Such a God is an "unmoved mover", not responsible not for the creation of the universe, as for Aristotle the universe is eternal, but responsible in a non-physical way for the continuing motion within the universe.

Modern interpretation
Aristotle's belief that the universe is eternal seems reasonable. If a thing exists, as it is almost unimaginable that at a later moment in time it could disappear into absolute nothingness, it is also almost unimaginable then at an earlier moment in time it could have appeared from absolute nothingness.

Gravity may also be considered an "unmoved mover", whether considered as a force or curvature in space-time. A "mover" with infinite range where all things are attracted to one another, and "unmoved" in that whether a force or a curvature in space-time can cause motion without being in motion itself.

Yes. And both the changing of the metric and real particles moving asymmetrically (thermodynamically, irreversibly) constitute time. — EugeneW

Right. So change constitutes time. Measuring time involves comparing one change with another, like the change of a virtual particle's state vs the change of a real particle's state. Which change you choose to measure by is arbitrary, just as measuring length and mass.

They don't oscillate in time but constitute time themselves. If you hold a virtual clock beside it though, you would see the hand of that clock go back and forth. — EugeneW

Again, we're simply talking about comparing one change with another when measuring time. But you're not measuring time. You're measuring change. Just as length is a comparison of two objects in one dimension, time is the comparison of change in two objects (in another dimension).

The clock measuring time has itself no direction in time. Virtual particles are the incarnation of the ideal clock. They go back and forth in time. In a Feynman diagram they are represented by a circle without legs, a vacuum bubble. This virtual clock is eternally present in spacetime.

Yes his argument is valid. But in logic, a valid argument has nothing to do with the truth. :smile:

But I would certainly agree with Aristotle that either time always existed or there is some supernatural explanation for it's becoming.

Time does not exist; it is used for human convenience and, Tom, you are correct. Time defined: what clocks measure; the measurement of motion. Time, therefore, is a measurement. I'm doing the measuring so I must be creating time or the clock is creating time. There is no past or future--only the present. The past exists in our minds and the present continues to what is called the future. Is time, then, a real immaterial existent? If I wanted to argue for time, I would maintain that.

If there's no causal link between events before a time t₀ (the big bang, 13.8 billion years ago) and events after, we could say time began (for us) 13.8 billion years ago. There's a causal gap that would mean even if time existed, it would have no (causal) import for us.

Here's how I understand the argument.

You can conceive of a moment as a boundary between the past relative to that moment, and the future relative to that moment. Geometrically, this would be like picking a point on a line -- let's make it the usual line from school and call that point "0" -- and using that point to define a ray $(-\infty,\ \ 0]$, and a ray $[0,\ \ \infty)$.

So that's a moment, "a beginning of future time and an end of past time."

*** Edit ***

Except of course we're not entitled to put it quite like this, and Aristotle doesn't.

All we need for Aristotle's version is for there to be no first or last moment, that is, all of time just has to be unbounded: $(first,\ \ 0]$, and a ray $[0,\ \ last)$.

There's still infinities all over the place, but we don't get arbitrary points in time like 100 trillion years ago.

******

Aristotle also says that the moment is our only "point of contact" with time, that time is unthinkable "apart from the moment." So any point in time we can imagine must be a moment. That is, he's arguing for something like the uniformity of time: every moment is like this, a boundary between past and future, and conceiving of time is, for us, conceiving of such moments.

Well then it's perfectly clear that time can't have a beginning or an end. If it had a beginning, there would be a moment that was unlike every other moment, that was only the beginning of a future and not the end of a past. Likewise for the end of time. And a moment unlike every other moment is not a moment at all, and cannot be part of our conception of time.

So far as it goes, the argument seems clearly right. (I didn't quite get it until I thought of "our only point of contact" in a sort of Flatland way -- imagine that all you know of the line is what you know as a point on it, take its point of view, and to be such a point is to see a neverending expanse of line to either side of you.) Indeed, no matter what cosmology tells us, we cannot help thinking it makes sense to ask what happened before the big bang, or what would happen after the big crunch. Time seems to us to go on uniformly from an infinitely distant past to an infinitely distant future.

In modern terms, it's a bit like taking the tripartite structure of the A-series, and arranging such moments as a B-series. Aristotle doesn't speak here directly of a moment changing from future to present to past, but he insists that a moment is a boundary between a past and a future. You can line up such boundaries in B-series fashion, but that doesn't change them into simple points that have only (tenseless) relations of before and after to other points; they each define two infinite sets of other points, all of which also define two infinite sets of other points, and each and every such point is a boundary between two such sets, between a past and a future.

*** Edit***

And then this is interestingly wrong, because we can mistake being unbounded for being infinite in magnitude. It's still true there's no first moment of time, and infinitely many before any given moment, but that doesn't mean they add up to an infinite amount of past time.

You can conceive of a moment as a boundary between the past relative to that moment, and the future relative to that moment. Geometrically, this would be like picking a point on a line -- let's make it the usual line from school and call that point "0" -- and using that point to define a ray , and a ray . — Srap Tasmaner

:up: Correctamundo!

Look forwards and time kinda needs to have a beginning.
Look backwards and time with a beginning is ridiculous.

What I’m saying—what is our life? Our life is looking forward, or it’s looking back—that’s it. That’s our life. Where’s the moment? — Ricky Roma

didn't quite get it until I thought of "our only point of contact" in a sort of Flatland way -- imagine that all you know of the line is what you know as a point on it, take its point of view, and to be such a point is to see a neverending expanse of line to either side of you — Srap Tasmaner

Similarly, philosophers in Flatland will conclude that there can be no third dimension. Every point in their experience has only a left and right, forward and back. A point with additional directions would be outside of their experience, and so not a point at all.

Events & Objects have beginnings. The marathon began at 6:00 AM, the baby was born at 7:25 PM.

Time began at _____. :chin:

As you can see a beginning presupposes time i.e. if you wanna say time began, time must already exist. 180 Proof said the same thing.