The comment section to the previous thread is interesting as one finds a broad spectrum of opinions there. Just to put some of them on the table, e.g. Wolfgang said in the first comment
- I would think that past and future do not exist the same way, otherwise why would you feel the need to distinguish past and future from the present and why would the question even come up?
And right the next comment by Count Iblis said
- The fact that the "now" is real implies that the past and future must also be real in exactly the same sense as the "now".
Somewhat further down, Quantum Ranger explains
- Well there can be no part of the past wherby any change is occuring, the past is not available for change of any kind, thus is not like the present time or future.
Another interesting point of view is Carl Brannen's who argues that the present and the future exists, but not the past because 'if it exists, why is it not alterable?', and CIP states
- The problem with shuffling the present into consciousness and psychology is that it doesn't solve anything. If consciouness can conjure up the present, how does it do it? With physics or some kind of magic psycho juice?
And if it's magic psycho juice, what is the physics of that? We can imagine that the division of time into past, present, and future is an illusion, but don't forget that you can't do any physics or even plan your breakfast without it.
So the following is an attempt to clarify why I am 'shuffling the present into consciousness'. I am not saying this is the only viable point of view, it is just a brief writeup of my thoughts on the matter.
To begin with I want to focus the point of discussion. I believe most of us have the feeling that the present moment is somehow different from the past and from the future. And that moment is constantly changing, thus the impression that time 'flows'. Yet, if you look at some law of nature or a theory describing the evolution of a system, there is no such thing as a present moment there. You can have a time in that description, and to every time you have a configuration. But all of these times are equally there or not there, none of these moments is special. So there is nothing in this description that explains our impression of a 'now' being different from the 'then'.
If you don't find that explanation very illuminating, maybe try the introduction to Lee's first 2008 lecture, min 42.14 - 49.00 (PIRSA 08010033), which also makes some references to psychology that I'll come back to later.
A different question is why the past is different from the future, or where the arrow of time comes from. I don't think this question is unrelated to where the 'now' comes from, but I don't want to discuss the arrow of time here. I will just assume that we have one and that information reaches us from the past, but not from the future for some reason. Another different question is what time actually is. For the following I will just take the point of view that time has proved to be a useful concept in our theories.
Needless to say, my believe that the past, present and future exist in the same sense goes back to time being a coordinate in Minkowski-space and not a parameter. Since some people commented on this in the previous post with mentioning the problem of time in General Relativity, let me emphasize I didn't say it follows that nature can't be a succession of present moments for this reason . I'm just saying that very possibly this is the origin of my personal opinion, and I occasionally wonder how far our education influences the opinions we hold on philosophical questions .
So what actually is the problem with the now? To me the question seems to be how can it be we experience a 'now' that is different from all other moments without that being an ingredient into the fundamental laws of nature. To me, human beings are some rather complicated systems in a four-dimensional spacetime. In the common picture we have worldlines on which the events in our lives happen. The question then becomes how can it be that in every moment we think this moment is special, but the next moment it's a different moment that is special.
I believe the reason for this is that a system as complex as our brain is able to store information gathered on the worldline in its memory. Memory that lies further in the past is different than the more recent one, most importantly it comes with some 'time-stamp' (that can be imprecise for the human brain but this isn't the point here). Since we have an arrow of time, we can't have memories of the future.
In every moment that moment itself is the most recent one, it is the newest piece of information in that memory and is thus special. Yet the next moment, it will be that next moment which is special. If you just draw a trajectory of a particle moving on a world line, say some curve x(t) in a space-time plane, you can't find anything like a 'now' because it doesn't have anything like a memory. For this, you'd need an additional quantity. E.g. for every t you don't only have an x(t) but also some kind of memory belonging to that moment t that stores some information about earlier times t', which one could denote as Mt(t') - the arrow of time would enter in some requirement like Mt(t') =0 for t'>t. One can extend such a concept to a space-time slicing instead of a trajectory, where the moment is the tip of the past lightcone, and the memory can contain everything in that past lightcome.
Unfortunately for drawing something like this you'd then need at least four dimensions which doesn't work well with the blogger software. So I'll try to give you an example. Consider the particle on its trajectory does 'collect' bits of information while propagating. From these bits, it forms a string of 0's and 1's which constantly gets longer, while the relevance of these bits becomes smaller the further this information already lies in the past. So you'd have a string of bits with the most recent piece if information always being the most relevant one.
With some pictures, consider you have this series of events (the 'trajectory')
If you'd add the memory of earlier moments to every picture it would look like this (times runs downwards)
Of course the human brain is more complicated that that. For example, lack of sensory input (like e.g. turning in bed at night) makes it very hard to accurately judge on the passage of time. Thus the impression the night lasts forever, even though the next morning it doesn't seem to occupy much memory (at least that's my experience). But I hope you roughly get the point that every moment can be subjectively special if rated on its quality within the available information in the memory, even though objectively all moments are equally special or non-special.
That is to say, even if the past exists in the same way as the present and the future, we'd still find every moment is unique.
I wouldn't say this explanation falls into the realm of psychology. Rather it's possibly neuroscience or biology. The way our brains store memory is a useful organization of information, that allows us to perform a lot of impressive tasks like e.g. constructing and driving cars, searching for the Theory of Everything, or reading this blog (in this order ;-). I am just skeptic about the argument that because we perceive a 'now' there must be something fundamental about it. Just to make clear, I am also not arguing the opposite has to be the case - in the above I have just explained why I think that human consciousness plays a role for this question.
I certainly don't suggest "some kind of magic psycho juice" as I hope is clear now. I think that it should become possible to examine this scientifically with our increasing knowledge about the way the human brain works.
Which features a system needs to have to perceive such an effect is probably a very tough question. Trees too store memory of the past, but finding out whether they have any experience of a now I guess requires a decent amount of treehugging.
I do not think the fact that we perceive the 'now' as being different from the 'then' is a fundamental property of nature, but rather a consequence of the way our brains store and organize information. We are able to store past experience in a memory, and information is perceived differently depending on how old it is. The present moment plays always an especially important role, but this is a subjective experience. In a nutshell this is why I believe the flow of time is an illusion.
PS: If you think you can change the future, prove it ;-)
 I added this option partly because the question isn't exactly well defined. So I guess some of you find the formulation doesn't express your point of view appropriately. If you want to clarify 'Other', just do so in the comment section.
 In fact I am fairly sure it does not follow. If there's interest, I can elaborate on this in another post.
 I strongly suspect that the outcome of the poll (with the majority favouring the block universe) is not very representative for the opinion of the average person on the street, but that it is dominated by people with an education in physics.
TAGS: TIME, MEMORY, PRESENTISM, BLOCK UNIVERSE, CONSCIOUSNESS, PHILOSOPHY, SCIENCE