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  • This is probably one of the most difficult questions you can ever ask a physicist or

  • philosopher... I am not a physicist - yet - nor a philosopher, but here I am, little

  • old me, not only wondering about the nature of time, but also making a first ever Youtube

  • video about it. My aim is to make you think, to create discussion... And of course, I hope

  • you enjoy the video!

  • The answer to what time is may be as simple as "Time is what the ticks of a clock measure"

  • or "Time is what keeps everything from happening all at once". But let's dig a little bit deeper

  • and make this video a bit more fun!

  • Let's start with Newtonian time. Newton's view of reality implied that time was external

  • and absolute. Newton's time is a kind of container, where events take place in a completely deterministic

  • way, linearly and independently of the observer.

  • Then came Einstein. His theory of special relativity, and then general relativity, both

  • led to the conclusion that time is relative to the observer. Time depends on where you

  • are and how you move relative to others. There is no such thing as universal time. Space

  • and time are constrained by c (the velocity of light) in such a way that the "now" of

  • one observer is not the same as the "now" of another observer. Mass, equally, can also

  • distort space and time.

  • Time dilation and length contraction are not just theoretical constructs within an elegant

  • theory. These effects have been tested again and again without failure; at macroscopic

  • scales, Einstein's theory has been shown to be a very good model of reality.

  • Let's talk about time dilation with an example. We have the elementary particles called muons,

  • which have a half-life of around 1.5 microseconds. That means that if we have, say, 100 muons

  • in the lab, after 1.5 microsecond has elapsed, we will have, on average, 50 muons left. The

  • other 50 will have disintegrated. After another 1.5 microsecond, we will have, on average,

  • 25 muons left... And so on.

  • These particles are produced at the edge of our atmosphere due to incoming cosmic rays

  • hitting air molecules. They are constantly produced so there is a constant fall of muons

  • towards the Earth's surface, travelling at nearly the speed of light. What is observed

  • experimentally is that more muons are detected than one would have expected, when we consider

  • their average lifetime.

  • This fact can only be accounted for when we use the model of time and space given by Einstein's

  • special relativity theory, where time and space are constrained by c, the velocity of

  • light, and so times and positions are relative to the observer. In this case, from our point

  • of view, the muon's own time appears dilated. More of them can reach the earth's surface,

  • from our perspective, because a second of their time lasts longer than a second of our

  • time.

  • So we can see that from the very beginning of last century, the concept of absolute time

  • was shattered, and time was understood as being completely dependent on the observer.

  • Newton's absolute time is only a good approximation, when speeds are low and when we can effectively

  • neglect the effects of nearby masses.

  • Now, let's take a look at the concept of time from a philosophical point of view. We have

  • what is called the A theory of time and the B theory of time. These were introduced by

  • the philosopher John McTaggart at the beginning of last century as well.

  • The A theory of time says that the only "real" time is the present; the past is gone and

  • the future exists as just a probability distribution, a potentiality of possible things that can

  • happen. There is no set future - on a kind of imaginary line "laid out there" for us

  • - just waiting to happen. Therefore, the future is not "real".

  • On the other hand, the B theory of time says that past, present and future all co-exist,

  • and are as "real" as each other. The B theory says that the distinction between past, present

  • and future are just an illusion of consciousness.

  • One of the consequences drawn by many orthodox physicists as a result of either Newtonian

  • physics or relativity theory is that determinism is a fact. That the past completely determines

  • the future, and hence, all what has happened since, say, the big bang, was determined by

  • the initial conditions, including you and me and our actions, thoughts and feelings.

  • There is no room for free will, which is seen as just an illusion, when we take this deterministic

  • point of view.

  • Hence, it seems that it is the B theory of time, not A, the model of time that most closely

  • agrees with the classical equations of physics.

  • So... It appears that common sense agrees with A Theory, but classical physics agrees

  • with B Theory. Could it be that time is a bit more complicated than what A or B theories

  • of time suggest? That reality is a mixture of the two ideas? Could it be that a linear

  • model of time is not a good approximation of reality? We will explore this issue in

  • a bit when we talk about Quantum Physics.

  • Now - before going into quantum physics - let's take a little break. How do I personally think

  • of time? What is my own experience of time?

  • On a personal level, I intuitively feel that time is not some mysterious external dimension

  • or construct that flows in the forward direction, that kind of dictates in what order events

  • can happen, but I feel that it is rather a much much more fundamental concept, even more

  • so than space.

  • I see time as a concept that is intricately linked to the individual's perception of change.

  • I think of time as "the perception of duration, of change and the ordering of events" by a

  • living entity or, in fact, you could say, by a conscious entity (here I'm defining consciousness

  • in line with awareness, hence animals and primitive organisms would have their own concept

  • of time, depending on how they perceive change).

  • On the other hand, I do not see time as a strict illusion either, nor as a block of

  • events completely determined beforehand. I see it as a pliable tool which, when used

  • within this particular universe, it enables our experience of 3D space and the perception

  • of the ordering of events.

  • In this way, I often ask myself that, if time can be thought of as the perception of change...

  • what happens when there is no change and no perception? Imagine you are somehow still

  • conscious, but confined in a universe where nothing ever happens and you have no perception

  • of any change whatsoever occurring (this reality would obviously be nothing like our physical

  • universe).

  • What are you left with? The first thing that comes to mind is that time does not make sense

  • in such a universe, it does not exist, unless change can be perceived by some sort of being

  • or beings that populate it so that some order can be assigned as to what goes first, what

  • goes after, etc. Maybe time could be thought of as a perpetual "now" under those conditions.

  • And all these thoughts obviously bring up the idea of universal versus relative or,

  • we could say, individual time. However, here we are talking of ideas beyond Einstein's

  • relativity theory. We are not talking about time and space in our physical universe obeying

  • certain rules, whereby c, the velocity of light, and mass, restrict how space-time behaves...

  • but in addition to this, we are talking about time being something that is meaningless in

  • the absence of an entity / a being (or a consciousness, an awareness) who is able to perceive change,

  • therefore being able to assign a "before" and an "after" to events that occur.

  • The other idea that I often wonder about, and that I feel is very important too is:

  • are space and time fundamental? If so, are they equally fundamental? Could it be that

  • one is more fundamental than the other?

  • I intuitively see time as more fundamental than space. I can sort of picture a reality,

  • a state (let's say a state outside of this universe) where space does not exist but time

  • does, where only patterns of "states" exist and there is a chronological order that can

  • be perceived between them (this is analogous to, say, my thought space, when I meditate

  • for instance... and I reach certain states, where there is no feeling or perception of

  • space, but there is definitely a perception or distinction between different states and

  • a perception of which one preceded which).

  • So time can be thought of as a fundamental structure that allows perception of order

  • between changing states or patterns (that is, order as in before and after).

  • A property can then be added so that there isn't just order between states, but there

  • is also a rule that regulates the basic fundamental tick between events, beyond which change can

  • not be perceived. In our physical universe, this fundamental duration could be the Planck

  • time. I will expand on the concept of the Planck units in other videos.

  • On the other hand, I cannot imagine the perception of a 3D physical space, existing independently,

  • without time. The way we perceive physical space is dependent on the time it takes for

  • light to reach our eyes. Even if we talk about non-visual perception, all other types of

  • physical senses are constrained by the velocity at which information within space can be transferred

  • physically to our senses. So any successful perception of 3D physical space is tied to

  • the existence of time.

  • This is of course, my own interpretation of time. But what does current science have to

  • say about this? Well, recent research carried out by a particular quantum gravity research

  • team, involving quantum universe simulations, seem to indicate that time is fundamental

  • (not emergent), that it existed before space, and not only that, but their theory says that

  • time has no beginning nor has it got an end!

  • (For references, please see the video links at the bottom, in particular, the talks by

  • Renate Loll, a professor of theoretical physics).

  • As computer simulations get better and better with time, it will be fascinating to see what

  • kind of universes can be created and what we can learn about the nature of our reality.

  • All these concepts are inevitably linked to the debate of whether the world exists out

  • there, independently, without needing aware or conscious entities to perceive it. It seems

  • that my particular interpretation of time, as I have discussed so far, does not make

  • sense unless some sort of consciousness is involved (be it a consciousness perceiving

  • our universe from within it or from outside of it).

  • So, is there an objective reality out there when there are no conscious beings to perceive

  • it? This is a fascinating subject that quantum mechanics brought to the surface within the

  • context of science, at the beginning of last century; a subject which was by no means new

  • and which many religions and philosophers had already debated for thousands of years.

  • But the fact that this can now be studied within physics is very very exciting.

  • When it comes to consciousness, unfortunately, many physicists cringe when they hear this

  • word. However, this debate was NOT started as a kind of new-age idea, but rather, it

  • started within the context of experimental science (for example, when discussing the

  • possible interpretations of the double-slit experiment results).

  • It seems to me, that it is partly due to some new-age ideas that flourished later on, which

  • use quantum mechanics as a kind of platform to support their theories about reality, that

  • today many scientists feel uncomfortable when having to consider consciousness as having

  • a fundamental role in the way the physical universe works (let me clarify, this is independently

  • of the validity of these new-age ideas! I personally have no problem with any kind of

  • ideas, as I try not to have any prejudices or pre-conceptions). The important thing to

  • remember is that these ideas were initially brought to the surface by many of the eminent

  • scientists who were at the forefront of quantum mechanics at the time.

  • Einstein, Bohr, Schrodinger, Heisenberg, Wigner, Bohm, Wheeler... The list goes on. These are

  • not new-age quacks (a word that pseudo-skeptics seem to over use these days, in my opinion)

  • but the very brilliant minds who laid the foundations of quantum mechanics.

  • Most of these scientists didn't just shut up and calculate (a very famous quote by Feynman)

  • but they discussed the philosophical, metaphysical and physical interpretations of quantum mechanics.

  • Consciousness (or mind), the existence of objective reality, the illusion of time...

  • These were not new age ideas, but very important ideas about reality that originally came from

  • the bunch of brilliant scientists who created quantum theory.

  • I find it very unfortunate that many mainstream scientists today seem to want to distance

  • themselves from any discussions involving consciousness, because they associate it with

  • new-age, spiritual or religious ideas of the universe. There are too many links with eastern

  • philosophy or religion for their taste...

  • Not to mention the incredible difficulty of introducing something as immaterial as consciousness

  • into a purely materialistic view of the universe. I find this quite sad, because when science

  • finds something that challenges the current paradigm, and there is enough evidence, in

  • my opinion, that maybe we are actually missing a very important part of the equation, we

  • should strive to think outside of the box to explain it, rather than trying to make

  • it fit into our existing (materialistic) view of the universe.

  • Ok, so let's go back to the concept of time, and explore how it can be perceived from the

  • point of view of quantum physics. I will try to be brief here, as I will make plenty more

  • videos on quantum physics in the future, including all its different interpretations.

  • Quantum physics provides a view of the microscopic world which is based on probability distributions.

  • Particles do not seem to be actual physical particles as we think of them, unless they

  • are observed. In the meantime, they seem to exist in some sort of probability realm, in

  • a superposition of states that obeys a particular wave equation, that is, Schrodinger's equation.

  • When a measurement is made - meaning that information is made available and retrieved

  • in the macroscopic reality regarding some property of the particle - then the wavefunction

  • is said to collapse.

  • The otherwise deterministic probability wave, suddenly jumps from a superposition of possible

  • states to just one. It seems that the observer has a very fundamental role in the "now" moment

  • when reality is observed, when a measurement is taken. So reality appears to be a deterministic

  • flow in probability space, until, voila, somebody decides to look, and one particular state

  • is picked from this probability cloud (seemingly randomly), and then reality takes a definite

  • form. Both the "now" moment in time and the observer seem to be crucial in the description

  • of reality.

  • Now, let's talk briefly about the arrow of time, entropy and the deterministic equations

  • of physics. Ok, so it is a fact that, within our physical universe, we observe the arrow

  • of time to point in the direction of increasing entropy - increasing disorder. Causality is

  • preserved, yet it does not seem to appear as a fundamental thing within our equations.

  • The arrow of time is not found within the fundamental equations of classical physics.

  • There is nothing in these equations that says that "now" is different from "two hours ago"

  • or "4 hours into the future", or that past should precede the present, for that matter.

  • On the other hand, the (statistical) 2nd Law of Thermodynamics shows that the arrow of

  • time points in the direction of increasing disorder; and this emerges from the study

  • of macroscopic systems.

  • On the other hand, I find the work of Renate Loll and her team very interesting in this

  • respect. Their work points in the direction of a very fundamental role for the arrow of

  • time in universes like ours, when we look at the problem from the perspective of a microscopic

  • universe, using quantum gravity, studying space-time at the Plank scales (using simulations).

  • But let's rewind a little bit now in order to compare the classical perspective with

  • the probabilistic perspective. The classical equations of physics do not differentiate

  • between "now" and "before / after".

  • There is also no possibility for free will in the deterministic equations of physics.

  • In fact "now" only takes centre stage from the point of view of an observer who can be

  • aware, possibly with free will, that experiences only the "now" moment, who can somehow influence

  • reality by the very act of observing.

  • So I can't help but conclude that no wonder the classical equations of physics cannot

  • explain the importance of the "now" instant of time. The observer and the effect it has

  • on reality have no place at all in classical physics.

  • In fact, even the Schrodinger equation in quantum physics is inherently deterministic,

  • until observation / measurement takes place, precisely at the "now" moment, the present.

  • And it is precisely then, as if by magic, that collapse takes place, and determinism

  • ceases to exist! The collapse of the wave function (the collapse of determinism) takes

  • place at the precise "now" moment when "knowledge" or information about the system is retrieved

  • in this reality in a macroscopic way (an observation takes place).

  • So a way to look at this is to see the deterministic part of quantum mechanics (Schrodinger's equation)

  • as a model that describes what goes on in the background (that is, outside our space-time,

  • in a probabilistic realm) when we are not actively retrieving information from there

  • into our space-time.

  • The "now" moment is also crucial because it is the moment when a conscious observer's

  • free will can actually operate, if we assume consciousness and free will not to be an illusion,

  • but a real entity that is fundamental in the way we describe our reality.

  • It is not the case, in my opinion, that we are forced to go from a deterministic view

  • of the universe to one based on a mixture of determinism and pure randomness, as some

  • physicists and philosophers seem to extrapolate from quantum mechanics. It is true that simple

  • double-slit experiments do not explicitly show conclusive evidence of an interaction

  • between consciousness (including free will) and the quantum realm. They can be interpreted

  • in different ways, for instance, using just explanations which regard information or "knowledge"

  • as the key factor.

  • However, there are numerous other experiments that not only show that things are actually

  • a little bit more complicated than what I have described so far, but that consciousness

  • (and free will) can indeed influence the outcome of a quantum experiment, by having the power

  • to alter the probability distribution that describes the system in between definite physical

  • states.

  • In this way, what would be an otherwise deterministic Schrodinger's equation (which is the probability

  • cloud going on in the background) can be affected by consciousness and intent. There are several

  • experiments that provide evidence of this fact, including those that involve quantum

  • random number generators (for instance, those performed by German physicist Helmut Schmidt).

  • Experiments such as these are the ones that provide conclusive evidence that our world

  • is neither deterministic nor completely random, and that consciousness and free will play

  • a central role. I will talk about these experiments extensively in other future videos.

  • I would like to stress something that I feel is quite important here. This is not a video

  • where I discuss the existence of free will. This is a very old debate which turns out

  • to be mostly based on assumptions related to where consciousness originates from (and

  • this includes our decisions, choices)... It is also usually based on whether consciousness

  • is an illusion or not, on whether consciousness is just a result of purely physical interactions,

  • and often, on the assumption that linear physical causality can provide the answer to all events

  • (including our decisions). The problem sometimes is simply that people don't even agree on

  • the definition of free will!

  • Most consciousness and free will debates these days become a battle of egos, to see who comes

  • up with the cleverest logical argument! Those who deny the existence of free will tend to

  • use quite a few flawed assumptions in my opinion, completely ignore personal subjective experience

  • and common sense, as well as all the relevant experimental evidence that is already out

  • there (and no, the evidence does not come from logic-land nor the belief in purely linear

  • physical causality, and it doesn't come from your typical quantum physics book either nor

  • from the study of neurophysiology!).

  • Going back to the topic of time, I am simply stating that, considering the central role

  • that the observer plays when we look at the universe from the quantum physics perspective,

  • we can conclude that the present, the "now" moment in time is precisely when the universe

  • can arise from the probability realm, as a consequence of our observation, non-deterministically,

  • and equally importantly, it is also the moment when our free will can operate, assuming it

  • exists.

  • From this perspective, the 3-D universe we experience, and the passage of time we experience,

  • are not only relative to the observer but cannot be considered as separate entities,

  • independently of the observer, their consciousness and their free will.

  • The concept of a probability realm computing outside of our space-time, the concepts of

  • entanglement, of non-locality... All these are ideas that make me wonder if this other

  • realm out there also operates within time, and if so, if we would be talking about a

  • time-frame that is a larger subset than ours, while including our own. So in this way, at

  • the Planck scale of time, below which we can't detect any more physical change (not even

  • in principle), we would still have the other realm, where a lot of stuff would still be

  • going on in the background. Whether we call this non-local realm another dimension, reality,

  • universe, or whether we consider it part of our universe is just a semantics issue really.

  • The fact is, this realm is intimately linked to ours.

  • This idea is in fact analogous to that of nested-time. This is the concept of generating

  • nested realities, each new reality having a fundamental time duration (analogous to

  • our Plank time) which is equal or larger than the fundamental time duration belonging to

  • the reality it has been created from. This is a fascinating idea that, along with many

  • others, was introduced to me by Tom Campbell, a physicist and consciousness explorer to

  • whom I will be forever grateful, for opening my mind and helping me get rid of dogmatic

  • believes (and I am not talking about religious believes here, but believes within the context

  • of science!).

  • I would like to finish this video, with another fascinating topic. I will present it with

  • this question. Can the present change the past? Can our choice of what we do now affect

  • the outcome of what we perceive to be in our past line of causal events?

  • Well, it turns out that certain double-slit type experiments in quantum mechanics seem

  • to provide evidence of backwards causality in time; for instance, the delayed choice

  • quantum eraser. While I won't go into the details of the experiment here, the idea is

  • that my choice of how to observe reality "now" appears to change the events in a particular

  • part of the quantum system, events which could only have occurred in the past.

  • I will outline the basic ideas that we are dealing with here and why the way we interpret

  • our reality makes a huge difference when it comes to resolving issues such as that of

  • apparent backwards causality. This in turn will influence how we interpret the nature

  • of time and the arrow of time.

  • It all boils down to this. If we think of reality as a physical objective reality existing

  • out there, independently of us, where events that were not observed in a macroscopic way

  • still did happen, really, physically, in our space-time, then we have to accept backwards

  • causality as a fact. On the other hand, if we think of reality as a construct linked

  • to observation, with a probability realm operating in the background, whereby information is

  • not really physically in our space-time unless we retrieve it in a macroscopic way at the

  • "now" moment in time, then turns out that backwards causality is just an illusion and

  • can easily be explained rationally.

  • In other words, if reality is not objective, events that we consider to be in the past

  • timeline corresponding to a certain part of a quantum system whose information has never

  • actually been retrieved in this reality, that remains in probability space (that is, nothing

  • really happened in a past objective physical reality, which was consequently changed at

  • a posterior moment, whereby the present changed the past, violating causality in time).

  • When nobody has ever retrieved the information, or when we erase any possible existing information

  • which would otherwise have enabled an actual observation within our own space-time, then

  • things remain in the probability realm; nothing physical ever happened in our past (it all

  • remained in probability space outside of our space-time).

  • So what we eventually observe, when we finally decide to retrieve information in a macroscopic

  • way, cannot be causally associated with another assumed event that we have, erroneously, tracked

  • back linearly in time, as if it had occurred within our space-time earlier on (when in

  • fact it didn't, it remained a probability cloud, because it was never observed in the

  • first place).

  • I know this may sound very confusing now, but I will make other videos in the future

  • were I discuss this in more detail as well as other quantum mechanics issues, including

  • non-locality and entanglement. The important thing to remember here is that a linear arrow

  • of time, viewed from the deterministic point of view of an objective reality, does not

  • make much sense, particularly when we deal with quantum systems.

  • However, this does not imply that causality within our physical space-time is violated.

  • On the contrary, when we do observe both the cause and the effect AT THE TIME they happen

  • (by observing I mean we retrieve information macroscopically), then causality is always

  • preserved. When parts of a system remain unobserved at certain times (as it would be the case

  • in the context of a quantum system), then the illusion of retro-causality or, in more

  • general terms, the illusion of a violation of linear physical causality arises.

  • Summarising, what we think of as time in our physical universe is, the way I see it, defined

  • by the perception of the "now" moment (the present) by a conscious, free-willed entity,

  • who actualises probability space, it brings information into their own space-time reality,

  • by the act of observation.

  • In addition, the concept of the existence of an information flow between our reality

  • and the probability realm lying behind it is what can help us expand the idea of causality

  • and the idea of the arrow of time, by understanding that unactualised events (that is, hypothesized

  • unobserved events) within our reality cannot be fit into a linear description of a causal

  • chain of events.

  • As Tom Campbell describes it, past and future can be thought to exist simultaneously, but

  • not within the context of a deterministic physical reality, a linear space-time, but

  • as multiple branching timelines of events existing within probability space, in a sort

  • of database, constantly being actualised, outside our space time.

  • The past database is made of the information describing all actualised events (what did

  • happen, that is, what was observed, experienced) as well as all the information related to

  • events that did not happen (and their corresponding probabilities that they could have happened).

  • Similarly, the future database includes all the events that can happen and the probabilities

  • that they might happen. The main ingredient that makes this a non-deterministic reality

  • is the presence of conscious entities, aware entities (in an shapes and forms), which can

  • navigate this branching probability maze, by using their free will (the ability to choose

  • among a set of perceived options) at the present moment in time.

  • I find this way of describing reality absolutely fascinating - and we are not talking just

  • about quantum systems here, but about the whole of our reality being probabilistic in

  • nature, with consciousness or information being fundamental in its description.

  • Let's not forget that physics was originally a very clear subset of metaphysics and philosophy,

  • until materialism took over. If it is indeed the case that our space-time is constantly

  • trading information with a dimension or realm which is outside of it, we will need to re-consider

  • our scientific method, how we define science and what its limitations are.

  • Well, we have reached the end of this video. I hope that you have enjoyed it. Don't forget

  • to give it the thumbs up, comment and share, if you have liked it! If you disagree with

  • any or all what has been said, please post as well and let's discuss!

  • Please be always respectful to others; I do not appreciate rude, angry, disrespectful

  • or non-constructive comments. Have a lovely day and see you in the next video!

This is probably one of the most difficult questions you can ever ask a physicist or

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時間是什麼?(更好的音頻)決定論,量子物理學,意識,自由意志,因果關係......。 (What Is Time? (better audio) Determinism, Quantum Physics, Consciousness, Free Will, Causality...)

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    劉家豪 發佈於 2021 年 01 月 14 日
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