[Serious] Is the Past Real?

[Foxaèr]

It's funny. Most writers use past tense, but most readers experience it as occurring presently.

[possibletarian]

Personally, I ponder the nature of time often and yet I really don't have a firm position. My symathies lie with presentism because I feel the past is truly gone and to the extent it exists it is in presents ghosts. Then as time goes on those ghosts fade while the set of possible paths that could have led to this moment increases. Then I think, certainly there is the way things actually happened so in some sense the past exists in some immutable way...from a god's eye view so to speak...regardless of whether from an objective reality (i.e. there are past objects) or an Akashic record.

Anyways, I was just curious what others thought about time.

Even the present really is the past, I prefer to think of now as my current experience that is determined by the past like looking at stars that may no longer exist, but they do to me at that time.

[emjay]

Is, was, and will be all modify tense.  The language implicitly assumes that each is real, as the modifiers are synonyms for the object in question.

Okay, thanks for the correction. Hopefully it doesn't too much affect the gist of what I was trying to say... the coherency of it?

[Neo-Scholastic]

You don't experience past events, you experience present events.  In the case of the bomb, you experience a flash of radiation and a blast of air.  These present events have a cause in the past, however.

I would disagree with that. The brain takes time to process the information from the senses. In fact, it can take fairly substantial fractions of a second to do so. So, the actual experience is always delayed from even the sensory event, let alone the event being sensed.

In the case of, say, a nuclear event at the site of an individual, it would be likely that no experience would be had at all since the vaporization of the body would happen much faster than the nerve signals and the brain processing. A nuke a kilometer away  would be a different matter, depending on the size and speed of the fireball.

Yes, I do agree that parsing out what constitutes the present subjectively from within the universe has value. I am curious about time at the cosmic level. Does the universe, as a whole have multiple states? If space-time is entirely within the universe, then it would seem it could not have multiple states or change.

[Angrboda]

I would disagree with that. The brain takes time to process the information from the senses. In fact, it can take fairly substantial fractions of a second to do so. So, the actual experience is always delayed from even the sensory event, let alone the event being sensed.

In the case of, say, a nuclear event at the site of an individual, it would be likely that no experience would be had at all since the vaporization of the body would happen much faster than the nerve signals and the brain processing. A nuke a kilometer away  would be a different matter, depending on the size and speed of the fireball.

Yes, I do agree that parsing out what constitutes the present subjectively from within the universe has value.  I am curious about time at the cosmic level. Does the universe, as a whole have multiple states. If space-time is entirely within the universe, then it would seem it could not have multiple states.

This reminds me a lot of questions about whether the physical universe is finite, whether it had a beginning, and so on. What lies beyond the last star? And what lies beyond that? These questions seem to be provoked by intuitions which were built for a problem space that has linear, inductively predictable properties, i.e. the macroscopic world around us. But we realize from both quantum mechanics and general relativity that these intuitions break down when we attempt to generalize these intuitions to other scales or questions. I suspect that questions of time and the geometry of the universe are likewise, that the paradoxes and puzzles are an artifact of our minds being built for answering different questions than these. Kant argues that our thought presupposes three-dimensional space and linear time, that we can't think outside those assumptions because they structure our thoughts. Wittgenstein has said that whereof one cannot speak, thereof one must be silent, but I'm not sure he's entirely correct about such things. If quantum mechanics and relativity are any indication, some of these questions may require a new way of speaking, of thinking things that cannot be thought. Feinman has said that if you think you understand quantum mechanics, you don't understand quantum mechanics. Likewise, the reality and ontology of time may be something that we can't properly understand, but with the aid of mathematics and empirical tools, we can develop models of it which can be reasoned about and tested.

[polymath257]

I would disagree with that. The brain takes time to process the information from the senses. In fact, it can take fairly substantial fractions of a second to do so. So, the actual experience is always delayed from even the sensory event, let alone the event being sensed.

In the case of, say, a nuclear event at the site of an individual, it would be likely that no experience would be had at all since the vaporization of the body would happen much faster than the nerve signals and the brain processing. A nuke a kilometer away  would be a different matter, depending on the size and speed of the fireball.

Yes, I do agree that parsing out what constitutes the present subjectively from within the universe has value.  I am curious about time at the cosmic level. Does the universe, as a whole have multiple states? If space-time is entirely within the universe, then it would seem it could not have multiple states or change.

I don't see why not. First, a probability distribution that is different in different time slices would allow, even require 'change through time'.

The notion of 'time at the cosmic level' is problematic in relativity and particularly so in a curved spacetime. You could define the local time as that experienced by a comoving observer, but there is no guarantee that generalizes globally.

[polymath257]

Yes, I do agree that parsing out what constitutes the present subjectively from within the universe has value.  I am curious about time at the cosmic level. Does the universe, as a whole have multiple states. If space-time is entirely within the universe, then it would seem it could not have multiple states.

This reminds me a lot of questions about whether the physical universe is finite, whether it had a beginning, and so on.  What lies beyond the last star?  And what lies beyond that?  These questions seem to be provoked by intuitions which were built for a problem space that has linear, inductively predictable properties, i.e. the macroscopic world around us.  But we realize from both quantum mechanics and general relativity that these intuitions break down when we attempt to generalize these intuitions to other scales or questions.  I suspect that questions of time and the geometry of the universe are likewise, that the paradoxes and puzzles are an artifact of our minds being built for answering different questions than these.  Kant argues that our thought presupposes three-dimensional space and linear time, that we can't think outside those assumptions because they structure our thoughts.  Wittgenstein has said that whereof one cannot speak, thereof one must be silent, but I'm not sure he's entirely correct about such things.  If quantum mechanics and relativity are any indication, some of these questions may require a new way of speaking, of thinking things that cannot be thought.  Feinman has said that if you think you understand quantum mechanics, you don't understand quantum mechanics.  Likewise, the reality and ontology of time may be something that we can't properly understand, but with the aid of mathematics and empirical tools, we can develop models of it which can be reasoned about and tested.

And I would say that the mathematical models *are* our understanding. Too often there is an assumption that we must use classical ideas for our understanding (particles with definite properties at all times, etc). And, if you hold to this requirement, you won't be able to understand QM .

But we can *and do* have models without 3D space or linear time and people *do* understand those models and can use them to predict what happens in the real world. When the old intuitions break down, we formulate new intuitions. And yes, our minds can learn to think outside the old constraints and with the new models.

But let's face it. Feynman understood QM. He was central in the formulation of quantum field theories, after all. These are testable, mathematical models of the universe that agree with actual experimental results. We know how to use this model to predict the results of future experiments and in all cases those predictions have been correct. it is even possible to develop intuitions about what the correct results will be without actually doing the calculations.

What else, precisely, is required for 'understanding'?

[Jehanne]

This reminds me a lot of questions about whether the physical universe is finite, whether it had a beginning, and so on.  What lies beyond the last star?  And what lies beyond that?  These questions seem to be provoked by intuitions which were built for a problem space that has linear, inductively predictable properties, i.e. the macroscopic world around us.  But we realize from both quantum mechanics and general relativity that these intuitions break down when we attempt to generalize these intuitions to other scales or questions.  I suspect that questions of time and the geometry of the universe are likewise, that the paradoxes and puzzles are an artifact of our minds being built for answering different questions than these.  Kant argues that our thought presupposes three-dimensional space and linear time, that we can't think outside those assumptions because they structure our thoughts.  Wittgenstein has said that whereof one cannot speak, thereof one must be silent, but I'm not sure he's entirely correct about such things.  If quantum mechanics and relativity are any indication, some of these questions may require a new way of speaking, of thinking things that cannot be thought.  Feinman has said that if you think you understand quantum mechanics, you don't understand quantum mechanics.  Likewise, the reality and ontology of time may be something that we can't properly understand, but with the aid of mathematics and empirical tools, we can develop models of it which can be reasoned about and tested.

And I would say that the mathematical models *are* our understanding. Too often there is an assumption that we must use classical ideas for our understanding (particles with definite properties at all times, etc). And, if you hold to this requirement, you won't be able to understand QM .

But we can *and do* have models without 3D space or linear time and people *do* understand those models and can use them to predict what happens in the real world. When the old intuitions break down, we formulate new intuitions. And yes, our minds can learn to think outside the old constraints and with the new models.

But let's face it. Feynman understood QM. He was central in the formulation of quantum field theories, after all. These are testable, mathematical models of the universe that agree with actual experimental results. We know how to use this model to predict the results of future experiments and in all cases those predictions have been correct. it is even possible to develop intuitions about what the correct results will be without actually doing the calculations.

What else, precisely, is required for 'understanding'?

Of course, exact, closed-form solutions rarely exist, but, the approximations are good enough, and, keep getting better and better over time. Where one appeals to a God or gods one could equally well appeal to fairies or pixies; to admit one is to admit an infinite.

[John 6IX Breezy]

Would music be possible if the past didn't exist? Something about playing a set of notes requires that it be embedded in the past in order to carry a melody. Not sure if my point makes sense but here are two ways to illustrate it:

1. If the past wasn't real, then playing a note in isolation in the present moment would be indistinguishable from having played it after a sequence of notes. Both examples would be the equivalent of pressing the reset button. And yet, this isn't the case. A note will sound either harmonious or discordant depending on what preceded it. The past transforms it.

2. The notes cannot be simply held simultaneously in memory in the present moment, the way a photograph might hold referents that no longer exist, because if a sequence of notes were to exist simultaneously they would become a chord rather than a sequence.

In other words, the notes of a melody cannot exist at the same time, neither in the world nor in memory, without changing the song. It needs to extend into the past in a real and inteconnected way.

[arewethereyet]

There are things in my past I wish weren't real.