[General Battuta]

One of the biggest mysteries left to man.

What is it?

Physics should be time symmetric. Relativity implies all of the universe should exist as one enormous block, past present and future already fixed and complete.

Why do we experience it as moving down a path with a 'now'? Why is there an arrow to causality?

For a while I pondered the possibility that there's simply a 'now', a stage, no past or future to reach - just one instant in which the universe exists, coupled to the past and future only inasmuch as the laws of physics dictate how the layout of the stage will change. But relativity requires time to be accessible in a cross-sliced fashion.

This question is critical because it ties into the mystery of consciousness. We do not yet understand why we experience experience the way we do, moment to moment. If we were able to resolve the arrow of time and understand why the now is the now, we might have a better idea. If the mind is a physical system, and the mind experiences time, there must be a physical reason for time.

Ideas?

[Snail]

We don't exist, existence is an aberration.

[watsisname]

I liked the "universe born within the event horizon of a black hole in another universe" idea that was discussed a while back, though that simply places the burden of explanation further back by having to explain why that parent universe has such an arrow of time as well.

So uh, I really don't know why we only see time flowing in one direction.  It's a very strange concept to think about.

[Veers]

Western Culture is based on a linear timeline (Christianity, Islam, Judahism, Athiesm, Evolutionist, etc.). Essentially Creation (by God, Big Bang etc) and it follows a single line until the end (Rapture, universal doom or whatever). We make decisions which can change the course of this linear timeline, we can alter our own 'world' and such.

India for example, has followed a circular timeline, everything is the same and always will be. If we try to make changes, we are fighting how reality is and in the end we are forced to conform to the circle again.

(Been learning about this in regards to Post-Colonial Literature. Not easy for me to try and comment on.)

[General Battuta]

Western Culture is based on a linear timeline (Christianity, Islam, Judahism, Athiesm, Evolutionist, etc.). Essentially Creation (by God, Big Bang etc) and it follows a single line until the end (Rapture, universal doom or whatever). We make decisions which can change the course of this linear timeline, we can alter our own 'world' and such.

India for example, has followed a circular timeline, everything is the same and always will be. If we try to make changes, we are fighting how reality is and in the end we are forced to conform to the circle again.

(Been learning about this in regards to Post-Colonial Literature. Not easy for me to try and comment on.)

This is an interesting point, but the question is more profound than 'mere' culture - there is a clear, intuitive, physical perception of linear local time shared by all humans, even those with perfect episodic memory.

I've updated the first post with a bit more meat.

[watsisname]

Just an aside, doesn't relativity also state that there also no real such thing as "now"?  (Relativity of simultaneity)

Case in point, what time is it on Mars right now?
Answer:  At time of writing, Mars is about 19 light-minutes from earth, so the current time on Mars actually has a +/- ~19 minute window relative to earth.  In other words, there is a roughly 38 minute time interval during which an event on Mars could be seen to be simultaneous to an event on Earth, depending on the velocity of an observer passing through the vicinity.

[General Battuta]

Yes, I made that point in the original (and current) version of the first post. It is the primary objection to the 'stage of the now' conception of time.

[bobbtmann]

I like time.

[Snail]

I like time.

me too, we have so much in common wanna get married

[bobbtmann]

I like time.

me too, we have so much in common wanna get married

Until the END of TIME!?

[redsniper]

Well, I mean... you've got irreversible processes in physics. And you're always going to have that net entropy increase going on. So that might have something to do with it, or maybe I'm thinking about it backwards. Are you saying that those kinds of things are just symptoms of this ARROW OF TIME?

[Snail]

Well thanks to the ARROW OF TIME it is now 4am and im not happy

[ssmit132]

I like time.

me too, we have so much in common wanna get married

Until the END of TIME!?

"Till death do us part".

[General Battuta]

Well, I mean... you've got irreversible processes in physics. And you're always going to have that net entropy increase going on. So that might have something to do with it, or maybe I'm thinking about it backwards. Are you saying that those kinds of things are just symptoms of this ARROW OF TIME?

The thing is that all processes in physics should be totally time-symmetric. You could turn the clock back and the universe would neatly run in reverse. So what establishes the direction of causality? Why do we go only one way?

[Unknown Target]

Western Culture is based on a linear timeline (Christianity, Islam, Judahism, Athiesm, Evolutionist, etc.). Essentially Creation (by God, Big Bang etc) and it follows a single line until the end (Rapture, universal doom or whatever). We make decisions which can change the course of this linear timeline, we can alter our own 'world' and such.

India for example, has followed a circular timeline, everything is the same and always will be. If we try to make changes, we are fighting how reality is and in the end we are forced to conform to the circle again.

(Been learning about this in regards to Post-Colonial Literature. Not easy for me to try and comment on.)

This is an interesting point, but the question is more profound than 'mere' culture - there is a clear, intuitive, physical perception of linear local time shared by all humans, even those with perfect episodic memory.

I've updated the first post with a bit more meat.

Perhaps the progression of time is fundamentally related to our perception of time. If there was nothing alive to comprehend the passage of time, then how would we know time passes? What is "time"? Perhaps it is a construct only of living consciousnesses - Iron or Helium has no concept of time, for instance. It seems as if the mortal progression of our lives unto an idea (an end, visa vi death), gives the universe it's forward pattern.

What is time measured in to a fly? Is a fly's "seconds" the same as ours? What fundamentally different concepts would that fly understand the world through, compared to ours, if it's seconds were different than ours?

[redsniper]

The thing is that all processes in physics should be totally time-symmetric. You could turn the clock back and the universe would neatly run in reverse. So what establishes the direction of causality? Why do we go only one way?

But WHY should they be time symmetric? Some stuff just only happens one way. You saying there just shouldn't be a "way" in the first place? Hmmm...

Well, one thing I liked from the black hole thread, was the notion that we have this infinite loop of universes containing black holes, that then contain more universes, etc. and so then the irreversibility of time and other stuff arises from the irreversibility of stuff falling into black holes.

[watsisname]

Yes, but that only pushes the question back further by requiring an arrow of time to exist in the parent universe.

[redsniper]

Well, I was kind of operating under the assumption that we had a loop of universes instead of an infinite chain. That is, the "bottom" universe might have a black hole in it that contains the "top" universe. So then information and entropy are endlessly funneled from universe to universe. Which I suppose gives rise to the question "why is there gravity?"

EDIT:

Wait, ****. That doesn't help at all does it? Because even in that case, stuff falls into black holes irreversibly because the gravity of the black hole causes stuff to accelerate towards it. That is, the velocity of nearby stuff increases towards the black hole over time. FUUUUUUUUUUUUU- WHY IS THERE TIME?

[watsisname]

Hmmm, can the anthropic principle be called upon here?  Is it possible for life to exist in a universe where time flows backwards or has no preferential direction at all?

...is it even possible for such a universe to exist?!

¯\(°_o)/¯

[redsniper]

Yeah, I don't know. I think for the time being all we can really say is "that's the way it is." To me, it kind of seems like asking why we have EM radiation, or why it propagates at c. What if c were some other value? Would the universe still work? Does it matter?