This Present Moment: Experience and Physics

What is now? What is the present moment? These questions continue to stagger us, for nothing is so simultaneously familiar and alien than the passage of time. Nothing seems more “real” to us that the present, yet it vanishes into nothing at every attempt to capture or quantify it. In this special two-part episode of Stuff to Blow Your Mind, Robert and Joe dive into the experience, physics, philosophy and neuroscience of now.

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Episode Transcript

Speaker 1 (00:03):
Welcome to Stuff to Blow your Mind from how Stuff
Works dot com. Hey you welcome to Stuff to Blow
your Mind. My name is Robert Lamb and I'm Joe
McCormick and Robert. I've got a question. I know you've
got a good answer for. Do you ever do that
thing where you try to catch an awareness of now?

(00:27):
I feel like it's it's sort of the five year
old game, right. I remember I learned to play this
with myself when I was a little kid, where I
would think, no, win is now, No, it's now, it's now?
How soon is now? Exactly? Um? Yeah, it is like
a child's game to a certain extent, you know, as
you begin to become aware of time as an abstraction

(00:49):
and you ask yourself what is now? And then, of course,
one of the things about this question is you probably
keep asking yourself this question throughout your life, like there's
there's no putable answer that ever presents itself. Yeah, I
feel like so we have the sensation that we live
in the present moment, right, there is this idea of
the present. I think it's pretty much there and most

(01:11):
people's minds, because all cultures seem to have this idea
of the present. Maybe not all cultures, but most do
um And you've got this feeling that the past is
behind you and that's already happened, and the future is
in front of you. But in between you have this
present moment that I think is in a lot of
ways comparable to our relationship to the unconscious mind. And

(01:32):
what I mean by that is and you get the
feeling that a lot of your thinking and a lot
of what your brain does is unconscious. But you can
never catch the unconscious part of your mind in action. Right,
every time you try to be aware of how your
mind is working unconsciously, suddenly you're not unconscious anymore. You're

(01:53):
conscious of it. Like the flashlight of metacognition kicks on,
and you you can't be aware of un consciousness. Yeah,
it's the feeling of being strapped to a train. It's
hurtling farward through time and you can't quite turn your
head around to see all the various engine parts and
wheels and what have you that is propelling you. Yeah,

(02:14):
and I think that now, the now is kind of
like this. It's like you suspect that there was just
a now, but that now is no more. You you
can't really turn your attention to it. So you have
this general since you live in the moment of now,
but you've at least for me, I have never really
been able to fully become aware of the present. The
more I try, the more it's sort of becomes the

(02:37):
slippery tadpole where I'm trying to catch it between my
fingers and it's always squirming away. I know that there
are future now is coming, and I'm aware that past
now is have gone by, but I can never really
find the now of now. So that leads me to wonder,
is there a now? Is there even such a thing
as the present? And if there is, what is it?

(03:01):
And if there isn't, what is this sense of now
that we experience and how does it shape our lives? Yeah,
it's a fabulous question, uh, and one that's so easy
to dismiss because we we have all these various metaphors
that will get into to sort of understand time, to
sort of tie time up in a little, neat, little
package and set it on a shelf so we don't

(03:21):
have to really worry about it. Uh. And one of
those metaphors that we end up using, I think time
travel movies, time travel TV shows, I'm I'm watching another
one right now, and uh, and you know, the characters
are always moving around and picking what point in time,
what now they wish to go to, And it makes
you think of your now, your present moment as a

(03:44):
location on some sort of a line or a grid. Now,
for my own part, as far as mindfulness exercises go,
that that attempt to focus in on the present moment
and sort of unshackle yourself from past and future, I
think a lot of it does come down to focusing
on a rhythmic, ongoing process as opposed to trying to

(04:04):
you know, grab that moment, that now, or whatever you
want to call it. And usually the focus is on breathing,
because to focus your awareness upon your own breath is
to focus on the most immediate conscious exercise of the body.
It always reminds me of various adages about how God
is as close to you as your own breath, and
I believe in Islam, uh, they use the jugular or

(04:26):
the veins of the body in the same way, so
like it's as close to you as your own blood
or your own circulation. This flow of blood, the movement
of change through your body and through this pinpoint of experience. Uh.
And and when when I say pinpoint again, if you
try and grab that pinpoint and it it just you
cannot grasp it. And there are so many I mean,

(04:48):
I constantly think of the way literature explores this. I
mean it's a it's a recurring theme and a lot
of our favorite books and stuff about how whenever somebody
has something good or something they want to remember, they
can never have it in the moment, you know, Oh yeah, yeah,
I mean so many books are about life and death.
Corman McCarthy has said that all great works of literature

(05:09):
about life and death. He can't have life and death
without time. He he has a great quote from The
Crossing that I'll read real quick. Snowflake. You catch the snowflake,
but when you look in your hand, you don't have
it no more. Maybe you see this day chatto, but
before you see it, it is gone. If you want
to see it, you have to see it on its
own ground. If you catch it, you lose it. And

(05:31):
where it goes there is no coming back from not
even God can bring it back. Oh that's great. Then
now then now is like the snowflake, Like if you
want to hold it in your fingers, it's gonna immediately melt. Yeah,
it's this, it's this kind of this uh, this concept
that we use to make sense of our experience of time.
But when you try and and study it, when you

(05:52):
level physics, neuroscience, philosophy. We're going to expose a number
of the different tools you might use to try and
cap sure than now, but time after time, that snowflake
just melts away into nothingness. So this will be the
first part of a two part episode, right, that's right.
So I think in the first one we're going to
focus more on like the the experience of time as

(06:13):
it relates to physical reality, and then in the second one,
we're going to try to look a little bit at
the philosophy of time and at neuroscience and psychology and
what they can shed light on the experience of now. Right,
And there's there's gonna be a lot of interconnectedness too.
So this is definitely a two parter to listen to
in order. Now, I would imagine if I was five

(06:34):
or six years old and playing this win is Now game.
I wasn't the first person to do this. This has
to go way back in human history. I can imagine
that the ancients were probably probably writing about this mystery
of what is the now? Even though we have a
sense of now, how come it's so hard to catch?
Oh yeah, I mean the great thinkers throughout time have

(06:54):
tackled this, and most of them have seemed rather frustrated
by the nature of and by the elusive nature of now.
For instance, Aristotle wrote about it in the Physics, which
is a fourth century b c. Text. He said, for
what is now is not a part. A part is
a measure of the whole, which must be made up

(07:14):
of parts. Time, on the other hand, is not held
to be made up of nows. And he goes on
again the now, which seems to bound the past and
the future. Does it always remain one and the same?
Or is it always other and other? It is hard
to say. In Aristotle goes on to address the difficulties
of time on both counts. Time is a series of

(07:36):
nows lined up like beads, h you know, back to back,
and the notion that now is a termination point on
a line extending infinitely in either direction. I think this
serves to hint towards a debate that I think most
physicists would come down on one side. Of and the
debate is whether time is composed of continuous or discrete quantities.

(07:59):
Now you can think of all the the objects in
the world is made up of either continuous or discrete qualities.
One example would be that water seems to be a
continuous quantity. It just sort of like flows and there
doesn't seem to be units of it. But in fact,
through chemistry, we know that there are units of water.
There are h two O molecules. If you get down
to the molecular level, you can see that it is

(08:21):
discrete and not continuous, and you sort of have to
wonder if time is the same way. Time feels like
this continuous quantity, that there couldn't be like a single
smallest indivisible unit of time, could there be? Well, well
we will get into that a little but in this episode.
But it is one of those things where you can't say, oh,
how many so you want to meet me at the

(08:43):
coffee shop in three hours? How many times is that?
Can you can you break that down into indisputable um,
you know, micro portions of time. Well, I mean, obviously
you can have units of time, because we do, but
they they don't seem to be set by nature. There
doesn't appear to be a physical bottom limit to dividing
time into pieces. Yeah, there's not a like a lego

(09:05):
brick ification of time. I mean, if there is, it
is a brickification. It's it's the dividing up of time
into blocks that we can make sense off, but not
the the the unearthing of the pieces that make it up.
Though at the same time, this is going to keep happening,
isn't it. Later in this episode we will mention that
for the purposes of science there might be sort of

(09:27):
bottom units of time, but not necessarily for the universe itself. Yes, well,
we'll come back to that because I have more to
say on that as well. But for now, I guess
we should we should back up a little bit and
talk about just the basic experience of of now and
basic experience of time. Yeah, I guess we should look
to uh to physics for some definitions, Like if you

(09:49):
wanted to have a measure of time that wasn't just
you know Einstein's cheeky answer. Einstein would say, what's the
definition of time? It's what you read on a clock.
But you know he's joking, Like, if you're trying to
come up with the best physical universe based approximation of
what we mean by time? What is it? Well, I
mean it's at its most basic level, time is the

(10:10):
rate of change in the universe. The rate of change
in the universe, so the relationship between one point and
the next point in the history of an object. Yeah, though,
doesn't it get It gets tricky when you start bringing
in time based terms than to describe it when you
bring in history, etcetera. Yeah, that's true. It's one of
those things like, uh, you know, the classics and in

(10:33):
the art of motorcycle maintenance question like how can you
define quality without invoking the concept of quality? How do
you define time without invoking the concept of time? Yeah,
I mean basically though, you have to say, all right,
we are creatures that live in a universe where there
is change, and stemming from that, we haven't live in

(10:53):
a universe of causation to where uh, the cause must
precede the effect of something, which certainly becomes important when
you start thinking about time travel and what have you.
We age the planets move around the Sun and things
fall apart, right entropy, Yeah, and this is often linked
to time. Right. Time seems to have something to do

(11:13):
with the direction of entropy in the universe. As as
things tend toward disorder thermodynamically, the time interval goes up. Yes. Now,
early humans quickly took note of the cyclical nature of
sun and stars and moon and the seasons, and they
utilize this information to organize their lives. Natural time mattered,

(11:34):
local time mattered, and for more ancient societies, the understanding
of time was as cyclical as the cosmic movements they observe.
The sun rose and set, people were born, and people died,
all in an endless cycle. We've touched on on this
this version of time many times on the podcast, and
I think it's interesting to look to ancient societies and

(11:55):
see how much these markers of time, passage, and the
cyclical nature of the seasons and stuff really seemed to
matter to them. Like they often invested huge amounts of
resources and energy into projects for like marking celestial events
that would be recurring events. Yeah, why did they do that?

(12:16):
I mean, was that really necessary? I would I would
love to do a future episode where we explore this
more because one of the books that I used in
research here was Dan Falks In Search of Time, The
History of physics and philosophy of time and excellent volume,
and he devotes a lot of time to discussing these
ancient cultures and ancient people's, the Neolithic treatment of time, etcetera. Yeah,

(12:39):
that that would definitely be worth an episode. Like what
were the reasons these cycles were so meaningful in their lives? Yeah?
And it certainly was meaningful because that the repetition of
the cycle made things matter. I think it was really
Audio who said that encyclical time. Uh, any incident in
your life only matters insofar as it repeats uh an

(13:00):
archetypical moment of significance. Yeah. I think we can see
this distinction between the idea of cyclical time and linear
time showing up also in the types of like stories
that people like to consume. Yeah, Like, is is a
story meaningful because it recapitulates a story that's already been
told a million times? Or is it meaningful because it

(13:21):
tells a new story that's never been told before? Exactly? Now,
of course, this human society has became more modern, they
largely discarded cyclical time in favor of linear time, all
with a great deal of help from calendars and clocks. Now,
but before we go the Devil's contracts. Yes, Now, now,
before we go any further, uh, I thought we might

(13:43):
take a moment to talk about metaphors, because we've already
stepped in a number of them, and we're going to
continue to to use them intentionally and accidentally, as we
discussed now in time, I think it's just worth letting
you know out there that we have already had to
stop and edit out like at least a dozen times
we use the word time, right, So if you get
sick of hearing it a dozen times, then then just

(14:07):
know that we there were like three dozen instances that
were cut out, but it totally pervades all of our
metaphors and our figures of speech, right, Yeah, I mean
that that's the really the damning thing about about time
is that nothing in our lives is as close and
personal and yet at the same time so abstract and
resistant to our understanding. But still we try, right, and

(14:31):
one of the ways that we we try to understand
time is we we roll out metaphors. As with consciousness.
Parts of part of the problem is that we're just
attempting to understand the thing from within it, uh, even
more so than the human mind. We can't step outside
the human experience of time to consider the thing. In
that book I mentioned by by Dan Falk in Search

(14:52):
of Time, The History, Physics and Philosophy of Time, he
points out that we've long turned to the river as
a way to understand the quote unquote flow of time.
And that's great because the river metaphor. He's totally right
that this is one of the most common metaphors used
for how time progresses. But it it is both a
great metaphor because the river is unstoppable and you have
no control over it. But it's also not quite right

(15:15):
because you can stand in a river and let it
flow past you. So for the river metaphor to really work,
you would have to sort of be part of the river,
and you would have to be on a boat, which
means it's essentially just another technology metaphor. Right. But even
in a boat, you can paddle, you can swim against
the current, you know all that, you would have to

(15:36):
essentially be the water itself, with no power whatsoever to
control your position upstream or downstream in the river. You
would just flow and that's all you could do. Yeah,
it's one of those metaphors that breaks down upon close examination.
As Fault points out, a river flows in respect to
the shore. But what are the banks of time? Um?

(15:57):
Another one that comes up a lot, and especially with
with modern for modern minds. Uh. Again, a technological metaphor
is that emotion pictures? Uh, it's it's a there's a
film playing and we are we're watching a portion of it,
and then there is a played portion and an unplayed portion,
and it's physically present in the you know, when you're
looking at a you know, an old school projector. But

(16:20):
also with the film, like you say, the river moves
with respect to the shore, the film plays with respect
to the viewer the projector. It would have to be
that the film just is a thing that plays itself
and that's all there is. Yeah, And in a way,
these examples some of a lot of the problems and
understanding time, especially as we get into the often explored
idea the time is an illusion because it feels real.

(16:42):
It's a central aspect of our conscious experience. It's a
part of the world we and as we see it
and understand it. But yeah, when you when you try
to focus in on it and grab it by the neck,
it just fades away, you know. We can mention this
in a bit. But I think that there are some
physicists who will say that time is an illusion in
that time itself is not necessary to describe the universe.

(17:06):
But I think they're in the minority, right, I mean,
I think the majority of physicists would say, yeah, time
is a real thing. It's just that there's certain aspects
of it that are an illusion. Our our experience of
time is an illusion because it privileges this sense of now,
that time is like happening, and that maybe the future
has the potential to change and could be one way

(17:27):
or another, whereas you know, just looking at the physics,
there's no real reason to suspect that. Now. On on
the heels of this motion picture analogy, I should point
out that Max Tegmark, who will will come back to
again later on Max he likes to point out point
to a film on a DVD as a suitable metaphor.
So in this our life is a movie and space

(17:50):
time is the DVD. So just consider a DVD copy
of Risky Business? Is that his example or yours? Um? Oh?
You know, I can't. I can't remember because I keep
thinking back to this analogy and I always think of
risky business for some hand, for some reason, And I
can't remember if that was my flourish or his. But
the idea here is the DVD doesn't change. So you

(18:12):
can't say Tom Cruise is traveling through the DVD. He's
traveling through the lifespan of the film, and so is
the viewer. Speed it up, slow it down. But the
physical DVD doesn't change. Yeah, the movie just exists, though
you can watch it. Yeah, then again the viewer from
the outside of the way. Yet again, all the metaphors
fall apart. Now, every ancient society developed a calendar system

(18:35):
of some sort, even prehistoric people exposed to the naked
cosmic expanse of her head, they noted the movement of
the heavens. And here's just another cool bit about technology
and our our measurement of time. I was reading James
Burke's The Day of the Universe Changed, Uh, which was
one of his like two classic works on the history

(18:57):
of science and technology, and he made this point about
these of clocks and medievil times. He says that that
without calendars and clocks are written records memorable events marked
the time, such as seasonal activity surrounding the harvest, which
goes in with what we've been saying already. So that way,
it almost be like saying that instead of using a

(19:19):
ruler to measure distances, you'd measure distances by your by
your relationship to landmarks, you know, familiar important landmarks. And
so instead of using some kind of standard measure of time,
you measured them by relationship to festivals and important events. Right,
and here's here's what he had to say. Additionally, quote,

(19:40):
country people were intensely aware of the passage of the year.
But between these seasonal cues, time in the modern sense
did not exist. Even in rich villages, which could afford
a water clock or a sun dial, a watchman would
call out the passing hours, shouting them from the church tower.
The hours would echo through the surrounding countryside, shouted along

(20:00):
by the workers in the field. Units of time smaller
than an hour were rarely used. They would have no
purpose in a world that moved at the pace of nature. Man,
that's fascinating to consider. I mean, we so live in
a world of minutes and seconds. Now, I think could
it be that it's because we're surrounded by all these
digital devices that keep time accurately and of course we're

(20:23):
on top of that, we're constantly bemoaning the relativistic experience
of time, you know, where we look at the clock
and we're like, we say, Jesus, where did that hour go?
I've been working for an hour. It doesn't feel like it.
Or you think, oh, man, I I've only been waiting
here ten minutes. It feels like an hour. So it
is you do wonder to what extent we we have

(20:44):
this this rigid timekeeping system and it ends up backfiring
on us because our bodies and our experience of time,
it still moves at the pace of nature. Do you
think that maybe hyper awareness and hyper acute keeping track
of time actually makes us more like cleared to squander time.
I would say the intuitive thing would be the opposite,
that if we're hyper aware of time, that we you know,

(21:06):
we'd be very careful how we spend our minutes. But
I wonder if there could be kind of some some
backfiring mechanism there, because I often think when I'm sitting
around sort of watching the clock while I wish I
was doing something else, I can really waste a lot
of time on the internet. Yeah, I find that to
be the case too. I mean part of it. Maybe
I just have poor time management skills, but uh, I'll

(21:28):
often find myself in the trap of thinking, oh, I
have I have two more hours before a particular you know,
self imposed deadline, and and then I'll squander fifteen minutes.
And then after fifteen minutes is passed, then I'll then
not Then I will say, oh, my goodness, fifteen minutes
is over, and then I'll feel bad for squanding theft
I can say from my own experience, I honestly think
that I make best use of my time when I'm

(21:51):
not really keeping track of time. Yeah, I think I'm
most productive. I think I use my time in ways
that i'm I'm glad. I'm the most glad about out
after it's done, when I'm not noticing the minutes going by.
All right, So, for the individual experiences of the productivity
may vary, but Falk points out that linear time becomes

(22:12):
a cornerstone of the Western world and may have paved
the way for the scientific and industrial revolutions quote which
in turn triggered an an affinity for reason and a
sense of progress. By the end of the seventeenth century,
Europeans viewed time as an abstract entity, holy, independent of
human activity. Oh, the horror, the de personalized time. That

(22:34):
it's not it's not really your time as a measure
of your experience, but that it's this universal quantity that
you must adhere to. Yeah, we're stuck with clock time
and on the surface of things that it seems like
a rigid and unflinching order. Right, that this thing that
we're we're enslave too. Right, we measure the passage of
time in a dreary procession of seconds, minutes, hours, and years.

(22:56):
But this doesn't mean that time actually flows at a
constant rate. Even the use of of of a sun
dial is the visual observation of the Earth's movements. And
and even this is not a set speed. The speed
of Earth's rotation is slowing because some of our angular
momentum is being transferred via tidal force to the Moon's orbit.
Now granted it's you know, slowing at a it's a

(23:18):
that's occurring at a very slow pace. But still this
is not a constant thing in the universe. Oh yeah,
I mean a couple of billion years ago, the Earth's
today was much shorter. In a couple more billion years,
it will be much longer, and just think how much
you'll be able to get done. And that's not that's
without even getting into the topic of time dilation and
the observable reality the time flows at a different rate

(23:41):
depending on mass and speed. Which will be touching in
on that more as we proceed. And of course we
don't need machines to keep rhythm with the universe. Animals
and plants, uh, you know, all boast internal clocks to
keep them in sync with their environment. And the brain
plays a key role here. I have another quote from
from Fall here that I thought was wonderful. Somehow we

(24:02):
take in a vast array of chaotic sensory data from
our environment and organize it into a meaningful picture of
our surroundings. But it is an ever changing picture. It
is a picture that evolves in time, a picture rooted
in time. Human beings have a remarkably sophisticated ability to form, store,
and recall these mental images. Memory, it seems, is all
about time. Now may just last a flickering moment, but

(24:25):
in our minds it can endure for decades. That's fantastic.
But I wonder about even the lasting of flickering moment
because what is going on in that flickering moment it
is now really being registered. I think we may have
some bones to pick with that. You know. All of
this makes me think of scientist Michael Graziano's attention schema

(24:45):
model of human consciousness. This is where attention and control
of attention play the crucial role in the human experience. Uh.
Coming back to the idea that time is the rate
of change in the universe, and then our brain service
service in navigating this world of change. It would make sense,
wouldn't it that our brains would mirror the movement of causation.

(25:06):
The lion must attack before it kills, the fruit must
ripen before I can eat it, and thus my awareness follows. Yeah,
this draws a connection to something that I've discussed on
some other podcasts before. I think this came up in
old episodes of forward Thinking. But the idea of intelligence
being a function of time, this is something we don't
often think about. But imagine you were able to solve

(25:29):
really really difficult brain teaser type puzzles, but it took
you a thousand years to do it. Would that be intelligence?
I mean, would you call that intelligence? By by that
measure you could take all kinds of natural phenomena that
we don't usually think of as intelligent and call them intelligent,
Like you could call evolution itself intelligent by that measure,

(25:52):
because it solves amazingly complex, difficult problems. It just takes
millions of years to do it. Um. So at that point,
is it even intelligence or is intelligence something about acceleration
through time of solutions? Well, yeah, and that you get
into you into questions about emergent intelligence, the idea that
any sophistic sufficiently sophisticated system is going to essentially have intelligence,

(26:17):
though maybe not in a way that matches up directly
with our our conscious understanding of intelligence. Yeah, I mean
I think I would adhere to a definition of intelligence
that is necessarily rooted in some sense of time. And
this could make sense about why the evolution of intelligent
minds came about. I mean, as animals needed to move
faster to do things like our predation theory from the

(26:40):
Cambrian explosion, you know, as as as the speed of
life went up, was the need for intelligence increased? Well,
this makes me think about the you said, if it
takes a thousand years for you to solve a problem,
is it intelligence. A lot of that would would I think,
be relative to the life span of the creature. Right

(27:00):
and with the human example culture, So for a human being,
if a human being spends a lifetime solving a sufficiently
important problem, then it's considered a success. If if if
if the scientist spends their entire career developing a cure
for a terrible illness and they find it, they crack

(27:21):
that nut, then that's a success. Uh. But if you
look at it for more like a ancient humanoid situation,
then you could say, well, if a problem isn't solved
in you know, a day or two, then are you
really solving the problem because the the challenges are that
much more immediate, right And then if you're not a human,

(27:41):
if you're if you're an aunt, if you're if you're
a cat or a dog, then it seems like everything
would be well, it would be at least as immediate.
I mean, essentially, what I'm building up to here is
that it makes me think that the development of human intelligence,
or not human intelligence specifically animal intelligence, is link to
the fast moving demands of right now, like the fact

(28:04):
that decisions that need to be made quickly will strongly
affect your survival is what powers the development of problem
solving acceleration, which is what intelligence could be. Yeah, and
a lot of this, of course involves not only memory,
remembering what has come before, but being able to extrapolate
possible outcomes to engage in in mental time travel or chronesthesia, uh,

(28:28):
the idea where you can you can think about what
might happen if you do this, what might happen if
you do that? You essentially run through various simulations in
your mind without even necessarily, you know, consciously engaging in
the exercise. You're you're running the simulations, and it is
a remarkable to what extent we can run those simulations,

(28:49):
you know. It's the it's the same sort of energy
that that enables us to envision the far future of humanity,
whether it actually matches up with realistic expectations are not.
This is one of the many things about us that
I think we take for granted and we don't stop
to think how weird and amazing it is that we
can travel through time mentally forward and backward, and that

(29:11):
we can we can construct events that have not yet
happened out of events that happened in the past, and
are not before us right now. I mean, just just
pay attention to your dog, and then you can appreciate
how amazing this skill is because your dog doesn't really
seem to have much of this might have a little
inkling of it, but it's not robust in the way
yours is. And you should be thankful. Yeah, yeah, that

(29:34):
dogs and cats, animals in general, they live in the moment,
and uh, and there's a lot. I think there's a
lot to be learned from them. Someone argue that we
that's one of the greatest gifts that they they bestow
upon us, is that they allow us to connect with
the moment. Yeah. I mean, it's hard to rival the
joy of a dog getting ready to go on a walk.
Like I often think this. It happens every day. I'm

(29:55):
gonna take Charlie out. He's gonna poop in the leaves.
He's gonna smell a bunch of thorns and get stuck
on the face. And I've just never in my life
been as happy about anything as he is about the
fact that he gets to go poop in some leaves.
All right, On that note, we should probably take a
break and when we get back, we'll get more into
the physics of time, and then now all right, we're back.

(30:18):
So we talk about this present moment a lot, but
but what is a moment? A very brief period of
time that's generally that the the definition that you run across. Yeah,
it's hard to think about this once you start getting
picky about the geometry of time. So if you imagine
time as a space that you can map, and the
moment is maybe like a point along a timeline geometrically

(30:40):
a point, you know, it does not have like a length.
It is a point, right, it is it is of
infinite thinness. And time can't really be like that or
it wouldn't have any content, right, it would need to
have some kind of content. So what is the length
of a moment of time? And if there is a
length of it, does it not just become a segment

(31:00):
of time, in which case it's not really a moment
but a memory. Right. So you know, obviously we have seconds,
we have microseconds, and we have many different levels of
division beyond that, which I'm not going to list, but
you can you can look them up. There's some excellent
charts that that break down all the crazy variations of seconds.

(31:21):
Robert take me all the way down. That take me
turtles all the way down to the bottom of time.
Is there is there a smallest indivisible unit. Well, in physics,
we have the plank time. Uh, this is the time
required for light to travel in a vacuum a distance
of one plank length. That's essentially we're talking about five
point thirty nine times ten to the negative forty four

(31:43):
power seconds. That's a very short time. Yeah, it's in fact,
it's too fast for scientific observation, as it is dozens
of orders of magnitude faster than anything we can observe.
So you might ask yourself, well, is that the now
if we can't really break it down any further, that
that has to be there now? Right? Is that the

(32:04):
thing that time is made off? Sometimes I think you
see in like popular science articles that the plank time
gets brought up as like, oh, it is the fundamental
unit of time. It is the smallest indivisible unit. But
that's not really how it is. I mean, I don't
want to try to speak with too much authority. I'm
not a physicist on this level, but my understanding is
that plank time is not a fundamental indivisible unit. Of time,

(32:28):
but that it's the smallest measurement of time that really
makes sense within our dimensions theory, you know, within the
way we conceive of physics in the universe, and that
once you start dealing with smaller units of time you
can't do any meaningful calculations. Doesn't really mean that there
aren't smaller measurements of time, just that smaller measurements of

(32:49):
time would not be meaningful in our physics. Yeah, that
the briefest physically meaningful span of time. It makes me
think of what I like to think of as crumb theory.
With with my son, he's gotten out of this, but
there was a period of time where he would eat
something on his plate there was a little bit crumbly,
and then he would want more of it. But it's
it's almost like he could not see all the crumbs

(33:12):
that could be scooped together to make another, you know, spoonful,
another mouthful or two of the thing he wanted more of.
It's like those the crumbs were just too small to consider.
But you know, you, with a little bit of training,
you could make him see the crumbs within crumbs within crumbs. Yeah,
and I think he's getting there, but for a while,
it's like, I want another brownie. We'll how about all

(33:34):
those crumbs of brownie. I'm sorry, but those are not
significant quantities of brownie for me to think about. So
if you can't find a unit of now, that does
kind of undermine the concept that there is such a
thing as a now in the universe, you know, uh,
if it's all kind of these arbitrary units based on

(33:54):
our our ability to measure things in our physics and
our mathematical concepts the right. Yeah, but there remains this this,
this other question too that let's just say that now
is something that can't be really narrowed down to a
particular piece of time, but but it's there. Well, then
is it there for you and me? Is there? Are

(34:16):
we sharing the same now? It would it would seem
to just in our experience, right, I am in the
same room with you right now. Someone else is in
a room on the other side of the planet, and
we are in the same now, right. It makes sense.
But it certainly does. Because let's say you called the
other side of the planet with the telephone and somebody

(34:36):
answered the phone. You're both talking on the phone right now, right, Yeah,
So there does appear to be some very basic sense
of now that is meaningful. But it's not as simple
as that seems, right. And to break this down, we're
gonna have to to board the train of simultaneity. Oh boy,
So trains come up a lot in considerations of space time.

(34:59):
For instance, there's the idea that you could have a
clock measurements made by two people, one on the ground
and one on a train nearing the speed of light.
Speed affects the passage of time on each person's wristwatch.
That's an example of one train thought experiment, but another
important one, and this is one that you see highlighted
time and time again. Falk mentions that other writers have

(35:19):
mentioned it because it is it is a central sort
of physics of time, philosophy of time, uh thought experiment,
and this one is used to illustrate the relativity of simultaneity.
So you're probably wondering what can thought experiments about simultaneous
events reveal about the nature of now. Well more than
you might think. In fact, I would just want to

(35:41):
point out for anybody who's like thought experiments, I don't
want to get caught up in that philosophical junk. Thought
experiments have powered some of the greatest revolutions in physics
and the twentieth century. Einstein's breakthrough his relativity was thought
experiments before it was proven experimentally, and now it is
proven experimentally. But so based on relativity, we'll go to

(36:03):
this thought experiment. Imagine you are standing in the middle
of a train car. You're right in the middle, and
you're holding a camera flash. And at each end of
the car, the front of the car and the back
of the car, there is another camera flash that's triggered
by a light sensitive photo diode. And this is a
thing that converts a light into an electric current. So
if light strikes either of these sensors on the front

(36:25):
of the car or the back of the car, the
flashes they're attached to will go off. And if you
were to shine a flashlight at just the front of
the car sensor, that flash would go off, and vice versa.
I remember you were standing in exactly the middle of
the car, the exact halfway point between the front flash
and the back flash, and you're holding this camera flash
of your own. So let's say you set off the flash.

(36:48):
What happens, Well, the sensors at the front and the
back of the car detect that light at exactly the
same time because you're equidistant from both of them, and
they both flash simultaneously. And this is all good, right,
But of course, what happens when you accelerate this train
to close to the speed of light, which you must
do in a in a proper train thought experiment light

(37:10):
speed train. Yeah, so again, we position ourselves in the
exact center of the car. We're traveling at almost the
speed of light on top of this train, and then
we set off our flash, so the photo diodes register
the light and we experience the two resulting flashes as
simultaneous occurrences. They occur now, So it's exactly the same

(37:32):
whether your train car is standing still or moving near
the speed of light. When you're in the car and
you set off the flash in the middle, you experience
the front flash and the back flash going off at
exactly the same time, even if the car is traveling
at you know, of the speed of light, and you
might be thinking like, wait a minute, why is that?
How can how can that be true if the car
is moving so fast. Well, it's because we know from

(37:55):
relativity the speed of light is constant for all observers
the speed of light in a back and this could
be complicated by if you imagine like air and stuff
in the car. But let's just say there's a vacuum
speed of light, and a vacuum is constant for all observers,
so the flashes at the front of the car in
the back of the car would go off at the
exact same time. But here's where it gets really weird.

(38:16):
Imagine an observer on the train platform as your hyperspace
train goes by the speed of light, and there that
that observer is able to watch what's going on in
the car at the same time that you are doing it.
This person would see something completely different than what you're seeing. Yeah,
to their eyes. The flash in our hands at the

(38:38):
middle of the train triggers the rear flash first and
the frontal flash second, So two simultaneous events are no
longer seen is simultaneous from the outside, Two events happening
in the now are in separate. Now's yes, and this
is the weirdness of the world we live in, and

(38:59):
relativety proves it. The speed of light is constant for
all observers, so the person in the light speed train
car experiences both flashes at the same time, the light
has to travel the same distance to each one. Meanwhile,
this outside observer sees the sensor at the back of
the train car essentially chasing the light from the flash
in your hand. The cars moving really fast, and that

(39:20):
back of the car sensor is chasing the flash to
catch up with it. Meanwhile, the censor at the front
of the train car is essentially running away from the
flash at nearly the speed of light, so the light
takes much longer to reach it. And this is not
some trick of perception for the outside observer. The light
at the back of the train car actually does go
off first, even though they still go off simultaneously for

(39:43):
you inside the train car. Yeah, that is That is
crazy to to try and wrap one's head around. Yeah,
but this is the truth of relativity. There is no
now except for maybe your own personal now. There is
no universal now. There's no now that is also now
somewhere far away, and according to Falk, it gets worse. Uh.

(40:05):
This is one final quote from him here, I think
says quote, what do we mean when we say a
particular event is happening now? When we use the word now,
we are really comparing two events, I can snap my
fingers and then ask whether some other event is simultaneous
with my fingers snapping or not. If it is, I
say that the the event is happening now in the
Newtonian universe, I can legitimately ask what events in the

(40:28):
universe are happening right now. The answer would be a
unique set of occurrence is scattered throughout space, but lying
on a single slice of time, I can snap my
fingers and say, at say noon Eastern Standard time in
December first, two thousand nine, and every event everywhere in
the universe either is simultaneous with my finger snapping or
it is not. That was fine for Newton, but not
for Einstein. As we have seen in special relativity, there

(40:51):
is no universal agreement among observers as to whether two
events actually are simultaneous or not, and thus there can
be no universe personal now. So no now, no now
for anybody. And this is not a like a time
zone differential here, well, no hold on. I would say
that this doesn't mean there is no now for anybody.
There's no now for anybody. That's also now for anybody else. Uh,

(41:14):
though in many cases your nows are going to be
close enough together that it's fine for everyday purposes, Like
you're gonna be able to coordinate now is pretty well
with the people around you. But this is not a
feature of the universe. This is just like a close
enough approximation that it doesn't matter, right, But I mean
with enough space, uh, enough distance between people, if we

(41:37):
were to reach such a point, or or indeed, if
there are other intelligent life forms that are perceiving time
in another world, my now could be in their future
or in their past or vice versa. Yeah, and think
about this from this kind of science fiction standpoint. So
we use the concept of now in our politics. For example,
you know, it's very important that everybody has the election

(41:59):
at the same now. Right. You can't have the election
one day for one group and then you know, next
year for another group and still function properly, right, So
you need to be able to coordinate events temporally in
order to get a polity working as it should. But
try to imagine an interstellar civilization doing something like this.

(42:21):
And this is one of the questions that I think
sort of gets overlooked, and a lot of science fiction
imaginings of interstellar civilization spread out across vast distances of
the universe. Is the way that the ability of these
uh you know, top down administrative controls would really be
utterly crippled by the time differences that essentially by the

(42:43):
lack of a consensus now between all of the people
within their control. Yeah. This this is something that came
up in our the episode We Christian and I did
a while back about Interplanetary War that there have been
people who have commented that you could not have an
inter interstellar empire like you see in Dune or Star Wars,

(43:05):
or or Star Trek if you want to call those,
I guess they're empires in some cases because you could
not maintain order over such vast distances. I wouldn't say
necessarily that you couldn't maintain order, but that it would
be extremely difficult to maintain organization. Yes, I would say instead,
what you could maybe do is maintain order in a
very brutal way. And maybe this actually explains the brutality

(43:28):
of the empire in Star Wars, because this is the
galactic empire, right, It's spanning hundreds of thousands of light years. Uh,
you essentially have to just be able to whip everybody
in line the moment you show up, because you can't
keep them on schedule of normal political uh obedience. It

(43:49):
does make me think of of actual terrestrial models of
empire though, like particularly when you look at at at
the history of China, Like what was one of the
factors that enabled such such such excellent um unification of
of different people's And one of them is measurements. It's
it's making sure everybody's using the same measurements than the

(44:12):
same currency. Right, And if you write, if you've got
like a coin that's supposed to have the same value
at different sides of the empire, but they've got different
amounts of gold in them, that might be a problem. Right,
it's also worth noting, um this would you'd have to
I think we'd have to do more studied early pieces apart.
But if you go to China, all one time zone.
There is one time zone in China, uh, no matter

(44:33):
which end of the country you are on. All right,
So we're gonna take one more break and when we
come back, we will jump back into the physics of now. Alright,
we're back. So I wanted to mention just a couple
more interesting ideas from physicists physicists about the way in
which time is conceived for the individual and about the

(44:54):
experience of now. So there's a book by the Dartmouth
physicists Marcello Glyzer called The Island of Knowledge, The Limits
of Science and the Search for Meaning. And I think
Glyzer makes a kind of interesting point about our concept
of the present. Of course, as we've established so far,
the present is not a description of anything that exists

(45:15):
in reality. It's merely an impression created by our brains.
But one of the things he highlights is that the
our impression of the present, at least the thing that
feels like the present to us, even if there is
no universal simultaneity, even that thing has clear physical limits.
And he ends up describing this concept known as the

(45:35):
sphere of now. So here's an example. What are you
looking at right now, not a few seconds ago, but
right this minute? You know, if you're if you're like
many of our listeners, I would bet it's either a
car in front of you in traffic, a person sitting
across from you on the train, or some people ahead
of you on the next row of treadmills. Okay, so

(45:57):
I'm wondering whether this is going are we basically getting
the idea that now is related to proximity? Yeah, exactly.
Uh so here's my real example, And just imagine instead
of all that you're looking at a VHS copy of
Highlander to the quickening I wish. Yeah, you're holding it
a few feet from your eyes, and uh, whatever this
thing is, you have to realize in a technical sense

(46:19):
that you're not really seeing the object as it is now. Now,
this the time difference here probably doesn't matter enough to
really make a difference in your life. But the light
that reflects off the object or emits from it is
traveling at a speed of about three million meters per second,
and the light of the light gets absorbed by your

(46:39):
retina after it bounces off the object, a tiny, tiny
fraction of a second after the time it leaves the object.
So if the object you're looking at is within a
few feet, it's too fast to make much of a
difference in your behavior or anything like that. But it's
worth remembering this, and this really does matter over longer distances.
So imagine you're looking at an object on the moon.

(47:02):
Once an object is on the moon, even though the
moon is regularly visible to us, the difference is noticeable.
So if you say that there are armies of urukai
standing on the surface of the Moon mooning us, we
wouldn't see that for about one seconds roughly, because light
travels at about three thousand kilometers per second, the Moon

(47:24):
is on average about three eight kilometers away, so it's
about a second and a quarter delay between the Earth
and the Moon. And no ordinary matter, energy or information
can travel faster than the speed of light, And so
in a sense you can think about the speed of
light not only is the speed of the photons, but
really as the speed of causality. I don't know if

(47:46):
you've heard about this concept before, but that the speed
of light is sometimes interpreted in the universe is the
maximum speed at which things can happen, at which a
thing can affect another thing, meaning that information is in
some sense traded. Yeah. I think that's that's really good, because,
especially in sci fi scenarios, we we tend to just

(48:09):
think of it's easy to just fall into the travel
of just thinking about speed and travel and movement from
point A to point B, and not think about breaking
that down into the simple rate of change and things happening. Yeah,
and so so think about it. What could happen on
the Moon to affect the Earth faster than the speed
of light? I mean, nothing, nothing, and unless you might

(48:31):
want to invoke some kind of quantum weirdness, but you know,
nothing on the macro scale. The only thing that comes
to mind is like cosmic expansion, and I you know,
I'd kind of have to twist myself in a not
to come up with a reason for that to occur
at the Moon, Like it would have to involve like
galactics showing up or something I don't know. Wouldn't that
be a great way for the Earth to end? Though?

(48:51):
I mean, I'm not saying I want the Earth's end.
I love the Earth. I think the Earth should just
keep on going. But if it has to end, wouldn't
it be great if it ends by sudden on expected
rapid cosmic expansion. We'd never be able to realize it, though, right, Yeah,
everything just kind of flies apart. It might as well,
I mean, everybody's life ends, and you might just as
well assume that that's what occurs. But of course, in

(49:13):
your moment of now, would you be able to realize that? Yeah?
I guess. I guess we'll get more into that in
the next episode. Um, but yeah, I mean we've already
talked a little bit about the the effects of time dilation,
of course due to Einstein special and general theories of relativity,
but those really made it possible for us to understand
that both speed and gravity cause time to change. Time

(49:35):
speeds upper slows down relative to outside observers. So you know,
if you synchronize two watches on earth surface and then
you take one far out into space, like you take
it to the Moon, the watch on Earth will run
slightly slower than the watch on the Moon. And this
isn't theoretical, this is experimentally proven, not on the Moon,
but with the surface of Earth and higher altitudes. If

(49:56):
you doubt that, look up the half Ela keating experiments
where these a synchronize some precise atomic clocks. Then put
some in high altitude vehicles or in you know, basically airplanes.
I don't know why I call them my altitude vehicles.
Let's just be needlessly confusing. Put them in airplanes flying
around far from Earth's surface to show that time really

(50:17):
does pass differently depending on how far you are from
Earth's large center of gravity. But anyway, Glazer uses all
this to to talk about this concept he refers to
as the sphere of now, and he ends up saying
that the present exists quote because our brain blurs reality.
That our sense of the present, really, I think for

(50:39):
him is some kind of like illusion created by the
brain putting together some elements from different moments of time
that are within the causality of our sphere of now. Okay,
I like this. I like this idea of that the
sphere of now. It's a nice sort of physical, visible

(51:00):
metaphor that we can employ. One more thing about moments
in time I wanted to mention was an article from
October for Nautilus, again with the physicist Max teg Mark
Mad Max, who is great for exploring all kinds of
weird corners of physics, uh and strange hypothetical Some would
say nonsense, others would say ambitious, ambitious trains of thought. Um.

(51:22):
But he comes up with trying a picture. Essentially, he's
trying to create a model for what space time looks like.
And I think he's not the first person to imagine
things like this. Stephen Hawking sort of tried to imagine
things like this, but essentially he said, try to picture
the three dimensions of space that we live in collapse
down to the form of a two dimensional snapshot, like
a you know, a photograph. And let's say you've got

(51:45):
a little square polaroid of the Earth in the Moon
taken from a point in space above the North Pole.
And you take one photo, and you see the Earth
is in the center and the Moon is at one
spot in its orbit. And then you take another photo
and the Moon is a little bit further along in
its orbit. And no, imagine you just keep taking these
polaroids continuously as fast as you could possibly take them,

(52:06):
and then you stack them on top of each other
sequentially to form a tower. Now the height of the
tower of polaroids here has become the dimension of time.
Now imagine all these photos not as individual photos, but
integrated together into a three D image. And what you
would sort of get out of this when you imagine
the Earth and the Moon images stacked sequentially, is you

(52:28):
would get a cylinder of the Earth passing through the
middle of this box, and then a spiraling corkscrew of
the Moon going all all the way around it, over
and over again. And this is a way he comes
up with of of picturing for d spacetime. Now, this
is the interesting thing, he says. Try to imagine all
the elementary particles in your body this way, like they

(52:51):
begin to accumulate in this box, Like all these strands
start coming together around the time of your conception. And
as the elementary particles in your body move around, as
blood cells ring around your circulatory system, as your nervous
system passes around sodium and calcium and potassium ions, all
of these complex interactions make the shape of this immensely

(53:14):
complex braid in your time tower. And every time you eat,
and every time you breathe, every time you eliminate waste,
new strands and little hairs get pulled into this braid
or go out from it. And at the end of
your life, of course, the braid unravels and the strands
all go their own way. I've never really heard it

(53:35):
put this way before that he's not the first to
imagine a sort of block of space time like this,
but he's the first I've ever heard describe it as
a braid of particles through time. And I think that's
just beautiful. Yeah, it does seem far more in keeping
with it just the complexity of of time, as as
we are discussing it here when we start drawing in
these these physical understandings of what's occurring. But of course

(53:58):
if you look at this image, you have to say, okay,
what then is the moment? Is their room for now
in this image? If there is, there's only a metaphorical
one that's been created here in this h this image
we've come up with, it's not really analogous exactly to reality.
But what you'd have to picture is sort of a
not right that the now has become just this tangle

(54:22):
that can't really be understood. It's a cross section that
can't be understood without all of the braid before it
and after it. Isn't that perfect though, This thing that
is so easy to dismiss as this, this single point, this,
this smallest common denominator, is actually this enormous tangle of complexity. Yeah,
and tech Mark even says quote some people find it

(54:44):
emotionally displeasing to think of themselves as a collection of particles.
I got a good laugh back in my twenties when
my friend Amile addressed my friend Matt's as an atom
hoge Swedish for adam heap Uh in an attempt to
insult him. However, if someone says I can't believe I'm
just a heap of atoms, I object to the use
of the word. Just The elaborate spacetime braid that corresponds

(55:07):
to their mind is hands down the most beautifully complex
type of pattern we've ever encountered in our universe. The
world's fastest computer, the Grand Canyon, or even the Sun,
their spacetime patterns are all simple in comparison. In other words,
there's no braid like life. So I guess that's probably
gonna wrap it up for today's episode, but we will
come back next time because I feel like we haven't

(55:28):
gotten to the bottom of this question that we've sort
of discussed. How there is no external or objective now.
There's no now from the perspective of the universe that
really makes any sense to talk about, and yet there
very much is a sense of now that feels like
it makes sense in our lives. So what is that now?
What's going on in our brains when we conceive of

(55:50):
the now? And I think that's what we will explore
next time. Yeah, join us as we we look at
the philosophy of now, as well as the psychology and
Neuroscience of the now M. In the meantime, be sure
to check out all our other episodes. That's Stuff to
Blow your Mind dot com. That's where you'll find again
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(56:14):
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(56:34):
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