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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
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
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
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
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!
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What Is Time? (better audio) Determinism, Quantum Physics, Consciousness, Free Will, Causality...

2511 Folder Collection
劉家豪 published on July 15, 2015
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