In deterministic physics, all processes are time-reversible, meaning that they can proceed backward as well as forward through time
— Joshs

This is not true. In deterministic physics, not all processes are time-reversible. There are no reversible processes in nature. All processes are irreversible processes. The question is why they are moving towards higher entropy and not to lower entropy. — Hillary

Would you agree with this?

“Thermodynamics, then, appears to be one of the only physical processes that is NOT time-symmetric, and so fundamental and ubiquitous is it in our universe that it may be single-handedly responsible for our perception of time as having a direction. Indeed, several of the other arrows of time noted below (arguably) ultimately come back to the asymmetry of thermodynamics. Indeed, so clear is this law that the measurement of entropy has been put forward a way of distinguishing the past from the future, and the thermodynamic arrow of time has even been put forward as the reason we can remember the past but not the future, due to the fact that the entropy or disorder was lower in the past than in the future.”

Also, Hawking seems to have believed that Cosmological time is reversible:

“Dr. Hawking described three ''arrows'' of time: the Psychological Arrow, which he defined as ''the direction of time in which we remember the past but not the future''; the Thermodynamic Arrow, related to entropy and the Cosmological Arrow.
Dr. Hawking argued that the Psychological Arrow was controlled by the Thermodynamic Arrow so that both would always point in the same direction. But the direction of the Cosmological Arrow depends on whether the universe is expanding. If it started to contract, the arrow would change direction.”

Yes, I agree. But... the question is, the fundamental question, is: why does entropy grow? Why doesn't it get smaller, so time moves in the other direction, i.e., the direction of less total, universal, or global entropy? This could have been the case.

Why isn't it happening the other way round though? — EugeneW

Some physicists (e.g. Sean Carroll) have suggested that time may actually be symmetrical, such that there is a mirror universe to our own, with an arrow of time running in the opposite direction.

the question is, the fundamental question, is: why does entropy grow? Why doesn't it get smaller, so time moves in the other direction, i.e., the direction of less total, universal, or global entropy? This could have been the case. — Hillary

Could you describe for me what time moving in the other direction would look like in everyday experience, or would it look just the same as it already looks to us, given that life is a bubble of resistance to entropy?

Husserl, Heidegger, Derrida, Deleuze and Bergson have shown in different ways that a quantifiable, mathematizable nature presupposes the kind of time which consists of self-presences transitioning from future to present to past in sequential movement (existing ‘in' time) — Joshs

Exemplars of the obvious.

Exemplars of the obvious. — jgill

Obvious in the sense of obviously true or obviously problematic?

Obvious in the sense of obviously true or obviously problematic? — Joshs

Former, IMHO. :smile:

Obvious in the sense of obviously true or obviously problematic?
— Joshs

Former, IMHO. :smile: — jgill

Sometimes it takes philosophical probing to bring out hidden dimensions in what was taken to be obvious and common-sensical.

Could you describe for me what time moving in the other direction would look like in everyday experience, or would it look just the same as it already looks to us, given that life is a bubble of resistance to entropy? — Joshs

You would wake from the dead, get younger, thoughts go backwards, hear before spoken, return oxygen to the air, etc. You would feel like an unwinding poppet with a key clockwork, being pulled along, instead of being in control. You'll be pulled along to shoot back in the womb. How it feels? Dunno! It all depends on the initial configuration. Why isn't that the end of the universe but going in the opposite direction? Behold the problem of the direction of time.

Some physicists (e.g. Sean Carroll) have suggested that time may actually be symmetrical, such that there is a mirror universe to our own, with an arrow of time running in the opposite direction — Relativist

That actually happens. You can consider our universe as part of a duo. Both stem from the same source but one moves away on one side of a higher dimensional structure and the other to the other side. There is a difference which shows up as our universe being left handed and with matter, while the other side is right handed with antimatter. But time still goes forward. Still an asymmetry. CPT theorem.

Thank you for remembering me :) These days I have been in the house for working, reading and practice guitar playing etc. So it is now a lot more flexible time thanks to COVID.

I feel the motion of planets around the Sun, and Sun rise and sets are just means to postulate time, but they are not time themselves. Their motions are just intervals - intervals which are regular, hence human perception can rely on it for measuring duration of all other things. But time itself, I feel is an illusion, which does not exist, and it certainly has no direction, therefore no movement at all.

Thank you for remembering me :) These days I have been in the house for working, reading and practice guitar playing etc. So it is now a lot more flexible time thanks to COVID. — Corvus

So COVID had it's good sides as well! :smile:

I'm not sure why you think time doesn't exist so can't move either. Doesn't the Sun shine longer in the summer (in the northern hemisphere) than in winter? Doesn't the clock show, say, 8 hours in winter and 16 in summer (with or without clouds)?

In deterministic physics, all processes are time-reversible — Joshs

Non-sequitur. A simple counterexample of different physics is Conway's game of life which is entirely deterministic yet not reversible. There's no way to determine the prior state from a given one.

With our physics, classic physics is time reversible, but our universe is not fundamentally classic.
Determinism at the quantum level is interpretation dependent and some of the deterministic interpretations (including all the ones typically discussed) are not time symmetric. The reversible ones have the causes of any given event as likely to be in its future as in its past, and need to abandon both locality and counterfactuals to do it.

Dr. Hawking argued that the Psychological Arrow was controlled by the Thermodynamic Arrow — Joshs

That kind of makes them different manifestations of the same arrow, not two different arrows.

But the direction of the Cosmological Arrow depends on whether the universe is expanding.

Interesting. If the mass density of the universe was high enough, this would eventually be the case. Once the maximum expansion had been reached, the arrow would reverse. How is this suddenly a certain kind of time going the other way just because distant galaxies are now getting closer?

Could you describe for me what time moving in the other direction would look like in everyday experience, or would it look just the same as it already looks to us, given that life is a bubble of resistance to entropy? — Joshs

This seems to be a question for Hillary, but meanwhile, it seem to be a 4th arrow of time being referenced which is none of the three (memory, entropy, and expansion) Hawking listed. It is strictly a philosophical arrow of time with no empirical tests, which is probably why Hawking didn't bother to list it. That said, an opposing position was given, as expected:

You would feel like an unwinding poppet with a key clockwork, being pulled along, instead of being in control. — Hillary

Interesting response. It seems to suggest dualism coupled with some kind of growing block interpretation, where the free-willed mind/spotlight is suddenly reft of its undetermined future and is instead forced into the determined part (by way of already existing) of the (now shrinking) block. Memory is part of the immaterial mind, not the physics of the situation.

You would wake from the dead, get younger, thoughts go backwards, hear before spoken, return oxygen to the air, etc. You would feel like an unwinding poppet with a key clockwork, being pulled along, instead of being in control. You'll be pulled along to shoot back in the womb. How it feels? Dunno! It all depends on the initial configuration. Why isn't that the end of the universe but going in the opposite direction? Behold the problem of the direction of time. — Hillary

This isn’t authentic time you’re describing, it’s a game being played within the bounds of a pre-given schematics masquerading as time. Authentic time is qualitative transformation , not the frames in a movie moving forward or backward. Time moves
neither forward nor backward but otherwise.

So COVID had it's good sides as well! :smile:

I'm not sure why you think time doesn't exist so can't move either. Doesn't the Sun shine longer in the summer (in the northern hemisphere) than in winter? Doesn't the clock show, say, 8 hours in winter and 16 in summer (with or without clouds)? — Hillary

Yeah, every cloud has sliver lining as they say. :)

The Sun shines longer in the summer than in winter, because of the the angle of the Earth changing on its rotation to the Sun. That is not time itself. That is just a phenomenon resulted from the physical structure of the planet Earth's motion and the Sun light.

Human perception notices it, and postulated time from the phenomenon. They even contracted lets say 1 year is the Earth's rotation around the Sun to the exact spot, and they went on diving a year into 12 months, and month to 28 - 31 days, and a day to 24 hours etc. Time is a human invention. It is just a contract on durations and intervals.

This isn’t authentic time you’re describing, it’s a game being played within the bounds of a pre-given schematics masquerading as time. — Joshs

It's reversed time. But why isn't this actually happening? It could have been like that. Just reverse all motion. Why was it set in motion like it has been set?

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Yes. The clock to capture time with, is a human invention. But time itself, the irreversible natural processes flow from less to more global entropy (with local reduction as on Earth). Aint processes flowing? The question is though, why not from future to past?

Yeah, every cloud has sliver lining as they say. — Corvus

How's the guitar play? :smile:

Measurement presupposes a concept of measurement, — Joshs

There's no concept of "measurment". Measutement is an action. (Look up both words, "measurment" and "concept".)

Time understood according to certain long-standing assumptions shared by philosophy and science is just a dimension. — Joshs

Right. I have said that already.

But to philosophers like Bergson and the phenomenologists it is the structure of reality itself. — Joshs

Well, I respect their opinion. For me this doesn't make any sense at all.

If time as dimension is a human invention, what features of the world can you point to that are not human inventions? — Joshs

I'm not sure what you are asking here. Anyway, for one thing, the universe is not a human invention. Or, if you are talking about words/language, these are human inventions. But this is too obvious ...

Yes. The clock to capture time with, is a human invention. But time itself, the irreversible natural processes flow from less to more global entropy (with local reduction as on Earth). Aint processes flowing? The question is though, why not from future to past? — Hillary

Why not from future to past? Because it doesn't exist. Time is just illusion. All there is, is just human memory. If every human died today, then tomorrow there would be no time. Just silence and nothing. I
think it is what Kant said too - about time.

Space and time is nothing but a form of human intuition according to Kant. I think he is correct.

How's the guitar play? :smile: — Hillary

It is good fun. I like practicing it because it is a discipline that I can absorb my mind into it, and aim to improve. I like the tone of the guitars - guitars can have all sort of different voices depending on what genre of music you like to play to, and there is a universe in guitar finger boards - countless combination of melodies, riffs and chords that make up tunes in the little board with the frets.

I will try to put some of my guitar practice video links in the lounge forum. :)

Why not from future to past? Because it doesn't exist. Time is just illusion. All there is, is just human memory. If every human died today, then tomorrow there would be no time. Just silence and nothing. I
think it is what Kant said too - about time.

Space and time is nothing but a form of human intuition according to Kant. I think he is correct. — Corvus

Sounds reasonable! I wished I could see it like that. Indeed, when all life has gone, time and space are gone. Only black silence... And then... what's that sound...? Is it a guitar...? What lovely sounds! Aaahh! It Corvus, on the eternal guitar! Great thing not, the guitar! Timeless! :smile:

I wanna buy an electric one. It looks so easy, playing on them. With a headset for the neighbors and going fully fledged in the weekend. On Sunday morning...

Smolin argues ... Prigogine contends ... for Bergson it is ,,, — Joshs

It is good that you know about these guys and their opinions. I also know of a lot of guys who have or had an opinion about time. If cite them, and then other TPF members cite from their own guys, would that be called a "discussion"?

I believe that we are here to express our opinion, however it is formed. If, for example, I ask you, "What do you think about death?", would you answer "Well, Kierkegaard in his Philosophical Fragments said that ...". I don't care about what Kierkegaard said. I asked what do you think.

I also know about what a lot of guys who have or had an opinion about time If cite them, and then other TPF members cite from their own guys, would that be a discussion? — Alkis Piskas

Ha! Good one!

I believe that we are here to express our opinion, however it is formed. If, for example, I ask you, "What do you think about death?", would you answer "Well, Kierkegaard in his Philosophical Fragments said that ...". I don't care about what Kierkegaard said. I asked what do you think — Alkis Piskas

Better one even! :grin:

What if time is static, without the possibility to move? — Hillary

In Physics, "static" refers to bodies at rest or forces in equilibrium. That is, it refers to physical things. Time is not one of them. But even then, something static has the possibility to change state, like something "stationary" that I mentioned earlier.

In Physics, "static" refers to bodies at rest or forces in equilibrium. That is, it refers to physical things. Time is not one of them. But even then, something static has the possibility to change state, like something "stationary" that I mentioned earlier. — Alkis Piskas

The clock can't be stopped. There is no configuration of objects that stays the same forever. The global arrangement of matter always moves in one direction.

Glad you agree! :smile:

It is good that you know about these guys and their opinions. I also know about what a lot of guys who have or had an opinion about time If cite them, and then other TPF members cite from their own guys, would that be called a "discussion"?

I believe that we are here to express our opinion, however it is formed. If, for example, I ask you, "What do you think about death?", would you answer "Well, Kierkegaard in his Philosophical Fragments said that ...". I don't care about what Kierkegaard said. I asked what do you think. — Alkis Piskas

It would be called a discussion among continental philosophers, who use close readings of texts to buttress their arguments. Not so much on this site, though.

You asked my opinion. I quoted those people because I agree with their views and they make a good starting point for discussion, given that the quotes I included articulated a physics-based view of time as fundamentally unidirectional. So if you don’t care what Bergson, Prigogine or Smolen think about this issue then you don’t care what I think. I dont march in lock-step with their views but relative to your position I’m much closer to what they offer. Never discourage the use of quotes when they can deepen the substance of a discussion. If you have questions concerning the relation of my position to the quotes just ask me. The whole point of the quotes is that I can begin from them and then elaborate my thinking in relation to what has been quoted.

I would love it if you used quotes to clarify your position. It would give me a resource to gain further information from.

I believe that we are here to express our opinion, however it is formed. If, for example, I ask you, "What do you think about death?", would you answer "Well, Kierkegaard in his Philosophical Fragments said that ...". I don't care about what Kierkegaard said. I asked what do you think
— Alkis Piskas


Better one even! :grin: — Hillary

You like his basking in his anti-intellectualism? Right, let’s dumb down all discussions by shutting off reference to those who have articulated the issues most throughly.