The one sense in which time is frustratingly different is that I cannot extend equally in
each direction.
I cannot just turn around and go into the past.
And I seem to be always driven forward into the future.
I can stand still in space, but I can't seem to stand still in time.
Welcome to How to Keep Time.
I'm Becca Rashid, co-host and producer of the show.
And I'm Ian Bogost, co-host and contributing writer at The Atlantic.
One time I took a nap and I remember I woke up at sunset, but it looked like dawn.
And I was like, I'm late for work, like, what have I done?
And that's why I avoid naps in general.
It's just I'm so disoriented every time.
Oh yeah.
When you travel, you know, like I travel overseas and I'm jet lagged.
And the time is all messed up and I wake up at the middle of the night and then I can't
go to sleep or you start falling asleep in the middle of the day.
You're so far away.
I'm like, what time is it even?
And you can't control it.
I love how I'm just napping and you're traveling the world.
Yes, but.
I have naps like you described too.
There are all these ways that I experience these weird lags in my space and time, not
just with napping, but sometimes if I'm really tired, like a song sounds slower to me,
like the beat feels like it's delayed in some way.
Oh, right.
Or if I'm really caffeinated, it feels faster.
And same thing with time, like maybe I'm just getting older or it feels like time is
moving faster.
But I hate to tell you this Becca, but I think you may just be getting older because, you
know, time feels like it moves faster for me year to year.
And then sometimes I'll look at myself and the mirror, you know, after looking at a photo
and I'm like, okay, but I heard it used to be that color quite so much, right?
But it doesn't feel like much time has passed, you know?
There's a kind of like fun house mirror effect with time's passage where you think you
look a certain way in time, but it turns out you're all wonky.
Right.
And when I used to go home as a college student and my little brother who's six years younger
than me looked like a different person every year I visited.
And now the way I see my parents aging, it's like I...
You're aging at the same time.
It's not just them.
It's also you.
But you don't have that sense of insight in your own head.
You need some reference from outside of your body to remind you.
Oh yeah.
Time.
Jenna, are you a timely person?
Do you think of yourself as a timely person?
I very often on time.
I really am.
But I can also get lost in time.
I mean, I think if you're going to do theoretical physics and you're going to hunch over a blank
online sheet of paper, which is what I like, with a pencil for 12 hours that you've got
to be able to kind of turn off some of the chatter or some of the internal bio rhythms
that make you so aware of time passing.
So Becca, I spoke with the theoretical physicist, Jan 11, to understand what it means to place
ourselves in the universe in particular as it relates to time.
I'm Jan 11 and I'm a professor of physics and astronomy at Barnard College of Columbia
University.
Even specializes in black holes, actually.
Oh, interesting.
Yeah.
And black holes are weird because time seems to behave totally differently around them.
So what is it about black holes?
What is their role in helping us understand the nature of time?
The nature of time seems to go more and more out of sync as you get closer and closer to
the black hole.
So let's say you're an astronaut orbiting far from black hole and you have this beautiful
clock and it's telling you what time it is and your body is exactly in sync with the clock
and movies run at a normal rate and music plays at a normal rate and your companion, another
astronaut has a perfectly synchronized clock built by the same manufacturer, but they jump
into the black hole.
What you find is that they get closer and closer to the black hole.
The astronaut from far away will literally see the ticks on the clock appear to take longer
to be spaced in a more elongated way so that it says, though time is running more slowly
for the astronaut who's falling towards the black hole.
Now it's not just this clock.
It's also the music they're playing, the movies they're filming, they all are running
slowly compared to the astronaut far away.
Now the one who jumps in thinks their clock is normal, absolutely normal experience.
They just think the astronaut left on this orbit far from the black hole is running very,
very fast, racing through years of their lives.
All the movies are fast, the music is fast and the clocks are all speeding ahead and they
realize that they've come out of sync as they get closer and closer to the black hole.
So it's almost like the black hole is a lens for physicists to ask difficult questions
about time.
You can see it more clearly through the subject of the black hole.
Yeah, the way the black hole distorts slows time down as you approach its horizon relative
to somebody very far away.
It makes the black hole like a magnifying glass in some sense so that you can look on higher
and higher energies and smaller and smaller time scales because it's like this magnifying
glass kind of quality.
The magnifying glass metaphor is really helpful to me, but Jenna, I'm still not sure I understand
what time is.
I kind of have no idea what time is when I stop and think about it, even though I understand
what you're describing and I live in time all the time.
So once you use this magnifying glass of the black hole to shed light on the nature of
time in the universe, what is the answer?
Like what is time anyway?
I'm not sure anyone can give you a fair answer to that question.
Oh, no.
But we would all love to.
I could say, let's go back and say what is space?
Let's start there and see how time is different.
So I can say, well, I know I can move, extend my hand to the left and I can extend my hand
to the right in space.
I have a kind of intuitive notion of that and I can also measure space with rulers and
how far away things are.
Now time can be very similar to spaces what Einstein realized that there is sort of a four-dimensional
space time.
And in some sense, as the person years the black hole, it's as though they're rotating
what the astronaut far away called space into what they're calling time.
It's as though they're rotating away in this four-dimensional space time.
But the one sense in which time is frustratingly different is that I cannot extend equally
in each direction.
I cannot just turn around and go into the past.
And I seem to be always driven forward into the future.
Even if I'm standing still in space, I can't stop the next moment from passing.
I can't stop my body from aging and we can always go forward in this direction.
You know, some of the happiest memories I have from childhood with my brother was operating
under the same schedules in a way, waking up, going to school together, putting our backpacks
on, getting yelled at to put our jackets on and then sort of rushing out the door and
then coming home after three.
Like, eat something, have a snack together.
Yeah, the thing I forget to do, yes.
And you know, now my brother recently moved to Sweden for grad school, fancy fancy, that
feeling that we're kind of on the same rhythm of each day, we're kind of operating under
the same clock and sort of like moving through our days together is completely not there.
And you know, I don't know what time of day he does his work or I don't always know where
he is in space at any given time.
Yeah, I think I see what you mean Becca.
Like, I have two adult kids and they live in a different city from me and I'd much rather
be closer to them more of the time and you know, in part that's just about wanting to
be close, like physically close.
Of course.
But when I do see them in person, then it also feels different, it feels better but in
a different way because we're occupying the same time, not just the same space.
Even if nothing important is happening, it's happening to us together.
I think that's exactly what I miss is like that empty time we would share with each other.
So Becca, there's space and there's time and time is fundamental to existence just like
spaces.
But our relationship with space and time as these human beings are like very different
from one another, right?
Right, right.
Like you could go visit your brother in Sweden.
You could get on a plane and bridge that distance if you wanted to or needed to.
You can move around in space if you're like, you know, stuck in your car driving home,
you know, and I'll fall like I can get home, but you will.
You'll get home eventually and then you'll be there.
But you can't really do that in time.
You can't move around in time.
You can only go in one direction and that's forward.
I want to ask you more about this and I was thinking about it as I tried to prepare for
our conversation.
So I have three kids and two of them are grown up and one of them is a lot younger.
And before my youngest was born, I didn't think about her at all because she didn't exist.
But now the idea that she once didn't exist is kind of impossible for me to imagine.
And there's a name for this, right?
It's called the arrow of time.
So what does that idea mean, the arrow of time?
Just in response to what you just described so beautifully, we all feel this asymmetry
intuitively.
We have a great deal of anxiety about the idea that we might not exist in the future,
but we're completely okay with the idea that we did not exist prior to some point in
the past.
And that asymmetry is just built into us.
We're not distressed to believe that there was a point before which your daughter didn't
exist.
This is just because we all fundamentally feel the asymmetry.
We intuitive is just part of our everyday experience.
Now we don't actually know that it's that firm.
It is conceivable.
Many people have played with this within the context of Einstein's theory of relativity
that you could find a path where you did go backwards in time.
And there are all kinds of solutions that we know exist mathematically, but we think that
reality will forbid these mathematical solutions from ever becoming actualized in the universe.
But we don't know for sure that the asymmetry cannot be violated.
Does that contribute to our cultural obsession with time and the way that it flows forward?
I'm thinking here of time loops and their popularity in science fiction, tenet or Dr.
Strange, or the time dilation affects in a film like Interstellar or even alternate timelines.
These examples and novels and film of playing with time.
What do you make of those as a physicist?
Is this our cultural attempt to wrestle with the arrow of time?
Yeah, I think it's a really good way to challenge your belief system.
One of the things we have to do in theoretical physics is get over our intuitions that are
based on a very limited experience of being a certain size, evolving under the sun and
having certain eyes as a result of that and living a certain duration and moving relatively
slowly so we don't really notice relativity as an experience.
So it's beautiful actually to do these thought experiments and really challenge your biases
and try to break them and see maybe we could go backward in time.
Maybe I shouldn't presume that just because it's never happened to me and that it couldn't
happen and that there wouldn't be a physical, mathematically realizable way to do that.
And so we play those games all the time.
I wonder in your job, which is to think about cosmic things, how does that impact your daily
life?
When you're commuting, we're going to the groceries for what is your knowledge or understanding
of the nature of the universe?
How does it contribute to your day-to-day life?
Well, there's a lot of scientists who will say that whether or not they're comfortable
using the word spiritual, that thinking about these things gives them a profound sense
of meaning and a connectedness to something much faster than their ordinary lives.
And I often, especially, you know, we're at a time of great pain and strife and trouble
in the world.
And I often will meditate on this bird's eye, even beyond the bird's eye, to really
imagine the earth under this star and the star that's been burning for billions of years.
And then panning away from this star and imagining this entire solar system, all of us silly
little people warring together, orbiting together around a supermassive black hole, 26,000 light
years away.
And that is where we are.
That is how we got here.
And so do I think about that?
If I get cut off on my bike, I'm my way over to the studio to talk to you.
I don't.
You know, I'm shaking my fist in the air and I'm frustrated, but I do believe that in
a deep sense, it really has altered my sense of who we are.
And you know, people make like a five-year plan or like a ten-year plan.
And I've never, ever been that kind of planner because that's just not my experience of
life or time has ever been.
But I realize that people can have this impulse to control their time because you're one person
in the universe with very little control and all you can do is map out, you know, maybe
your weeks, maybe your years in a way that feels like it's under your control.
And hopefully at the end of the day, feels like you've made the most of whatever chunk
you're giving.
And you know, as Jan is explaining, that feeling comes from the fact that we can go forward
and backward and sideways in space, but we can't do the same thing in time.
And when it comes down to it, that's sort of just the fundamental puzzle and problem
with time.
It is as normal sized objects, beings in the universe, we cannot go backward.
And so that feeling is also weird, you know.
But with black holes, those are interesting to physicists because they're exceptions,
or at least potentially exceptions to the normal rules of physics.
And so therefore they offer these kind of lenses through which scientists can look at
time and understand it better.
You know, that's great for theoretical physicists, but not so great for the rest of us.
Like I don't have a black hole nearby that I can sort of ask questions about time.
Really, yes.
But I wonder, like, are there other lenses that ordinary people can use to make sense of
time?
Right.
I feel like we humans need a few ways to understand ourselves better.
And even though it's not directly related to physics, Ian, this theory called the social
clock, which Bernie Snuegarten, a social psychologist, came up with in the 1960s, can help explain
that pressure that we can feel that we should be hitting certain social markers at different
stages of our life at different ages, specifically.
Okay.
Obviously, the big things, like marriage, having children.
But I was thinking about how those are norms dictated by society, right?
But let's say you're someone who was raised with two cultures, then the social clock can
have sort of different terms depending on which society or which cultural norms you're
trying to fit into.
Yeah.
So like keeping track of different time zones, you have to keep track of different social
clocks.
If you think about the social clock, not as a set of hard and fast rules or even cultural
rules, but as something more like that lens, like the way that Janet thinks about black
holes, like you're going to look at time through the lens of the black hole, you can look
at your own personal time through the lens of a particular social clock.
And that could be an American one or it could be a different one.
You know, there's less pressure, perhaps.
I can start to make the social clock feel as chaotic as time itself from like one line
moving chronologically through all these different life changes and events into this sort
of wave of unpredictability.
Maybe that leaves more room for the unexpected and for serendipity too.
So Janet, how much time do we have, like is time infinite?
It's a really difficult question.
I don't know if space is infinite either.
We know it has a finite past.
We can't think of time as outside of the universe anymore.
We can only think of time as a quality of the universe or it could be that the universe
just expands and expands and expands until essentially each particle is so far away from
every other that there's really no meaning to the passage of time anymore.
How would you even know time has passed?
To know time has passed, I have to experience some change.
It could be a change just in my thoughts.
It could be an accumulation of heartbeats or it could be a tick on a clock.
But all of those things require more than a single particle floating alone in the universe.
And in fact, if I were to show you this as a movie, if I were to show you a movie of
a single particle, you would have no idea how long if the movie was running faster
slow, if it was true to time, whatever that could possibly mean, you would not have any
scientific way of measuring the passage of time.
Jenny, you mentioned change. Is that all time really is just change?
We do, yes, measure time through change.
If I were to a classic example, take this glass of water I have here and smash it to the
floor and film this for you, you would absolutely believe the movie had run forward in time
because you know that individual pieces of glass everywhere and water splashed everywhere,
that that's the logical way things unfold. They don't, if I were to show you the movie
running backwards, reassemble into a seamless glass with water inside it naturally.
That's not something we see. What we do see is we see change in the direction of greater
disorder. We do not see change in the direction of increased order. That's also part of the
era of time conversation. If I were to show you movies, you're always going to be able
to guess that one's running forward in time if you see things going towards greater disorder,
like smashing apart, more disordered. You're always going to know they're going to
running backwards if you see things perfectly reassembling. We do seem to measure the
passage of time as tightly correlated with the increase in disorder.
This is making me feel a little more at peace with the chaos in my own life, I think.
It reminds me of the fact that time feels different at different times. A long flight
can feel really slow, but then the vacation that you're flying to goes by really quickly.
Is there a physical reason why time feels different or is that a psychological thing?
I think one of the explanations could be this one of disorder. A lot of people will cite
this that when there is a lot of change relative to your overall experience psychologically,
you will consider that to be time moving more quickly. If you're a child and you're
having an experience, your overall body of experience is so small that actually psychologically
your perception of time is kind of slower. As you get older, that same experience you
might share with a child seems to you that time is passing faster because your overall
body of experience is larger relative to the amount of change you're perceiving.
Do you find yourself using your knowledge of the physics of change in your day-to-day
life? Does it make you feel better during a busy week? There's just a lot of change
happening right now. It can, but it can also remind me not to have such
fractured attention because I think it can feel like life just flies by.
And more considered attention, I do think it elongates at least for me that experience
of a stillness or being in the moment or a slower passage of life. But I have to say
I'm an incredibly busy person. I have a real problem with that. I don't want to pretend
I'm the Buddha here. And I do find I'm always thinking about the future and just the proverbial
say not to do, be in the moment.
Becca, sorry to get morbid here for a second, but the idea of living in the moment, it
makes me think about the moment when all your moments end. And if you read about the things
that people say on their deathbeds at the end of their lives, a lot of those sentiments
have to do with regret, with things that those people are happy that they did or things
they wish they'd done. A few years ago in a story for the Atlantic, the writer Michael
Arrard explained how the dying often use these metaphors of travel to talk about their
impending death. Just trying to make sense of what's happening to them.
Like, wow. Yeah, oh, the sentiment, like if I could just find the map, I'd know where
to go next. Like the way I understand that that sentiment is that like even at the end
of life, when you know there's no more moments left and there's no choice but to face
the forward flow of time into oblivion. People still haven't, they still haven't fully
come to terms of it. They're still yearning to go back to make changes or take comfort
in the fact that they can't go back and make changes, but they recognize that pull or
that tension, you know? My own sort of fascination with the social
clock stuff, I think came from a similar yearning to turn back the clock and make the changes
to my life that would, you know, put me in line with what I should have done and that's
the scary time thing, right? And like we're all coping with that fact in different ways,
realizing that no action, no sort of doing anything can turn back the clock. Almost everything
else we do involves going back to some capacity as well, editing an email before we send it,
revising, like a text, you know, we can kind of do everything forwards and backwards to
elicit like a different result. Time is just this sort of train I feel like I'm on, that's
moving along, you know, without my consent and I just have to be okay with that.
Yeah, that's what Jan is saying, you're on the train, you're on the train Becca. It's like the
constant tragedy of time that you from 10 years ago will never return, neither will you from
yesterday, but it's also like the great comfort of time. Time allows change to happen, it allows you
to change.
I very much feel part of a vast ecosystem going back to the Big Bang. I really remember learning that,
and I remember being floored at the idea that there are atoms in my body that are primordial.
And of course, many people say, you know, we're made of star dust and some of that primordial
material went through stars and had to be cast back out in the universe and are in my body
right now from a star. And I know that that's something lots of people know now and talk about,
but there are times where yes, I can suspend the feeling of that being just an intellectual fact
and actually feel a real sense of comfort that there will be a future where we will all be part
of that larger ecosystem again. Okay, well, speaking of being part of that larger ecosystem,
I mean, it's almost like a euphemism for a difficult topic that we nevertheless have to talk
about, which is that if time is change, you know, part of the change that we experience as human
beings is death. Like we're going to die someday or even before that, you know, my kids will grow
up and leave the house and they won't be around anymore. Do physicists have something to say about
that? About how humankind can grapple with our minor role in the universe? And you're kind of
touching on that with your own personal experience, but is there something in physics that gives us
clues about how to live without checking out or without falling into existential despair?
That's a very difficult question, but I have already left behind a part of myself that will never
exist again. There will never be seven-year-old me again. There might be some deep sense in which
that does exist seven-year-old me. It's just not one of the movie frames I can make my way back to.
There are all these deaths along the way. I have children and they'll never be babies again.
I will never hold my little babies. And I think that when we kind of see it that way and we begin
to ask, what does it mean to be me? I left so much of that behind them. Am I still the same person?
I mean, these are philosophical questions. I think you're wondering what does a physicist have to say
about that? I think it's really going to sound quite difficult, but the physicist is likely to go
as far as to say. There really is no self. You are a collection of quantum particles and interactions.
And they change. And we see this all the time. I certainly could take a chemical that would
completely change my chemistry and completely change my personality in what sense am I still me?
I could have an injury to my brain and the tissue is reoriented and reconfigured. And what sense is
that still me? And in what sense was it ever me? We are just a collection of particles. And one day
we will go back into the galaxy. So what then is the purpose or value of your and my time on Earth in
that context? Well, this is back to taking that astronomical view of the Earth and why people are so
stirred by things like the International Space Station, taking a photograph of the Earth rising,
Earth rise. I believe it helps us to understand that so much that we take so seriously is completely
devoid of any meaning. And most of all, this kind of notion of our differences, I think, has been
kind of historically catastrophic. To think of all of us in this way can be transcendent and it can
be quite unifying. And I think it's okay to still say, I really love the color green. Even if I
believe it's only in my mind, I can live with that. I can sit with that.
Then I have one last question for you. In a sentence, how do you define time?
One last question that people have been ringing their hands over four centuries in will
and will for centuries to come. If forced, I would say to the best of my present understanding,
time is a measure of change. And I'm very unsatisfied with that answer. I almost should be more
rebellious and say, I can't do that and I don't want to do that because if I were to do that,
I'd be saying something so tricky. So for instance, it would be very easy for me to argue with
that statement and say, well, what do you mean change? Change happens over time. We're caught
in a little loop. I could say something like time is a dimension, but it's a dimension that has an
arrow where you're forced to always move in a particular direction. So it's a dimension just like
North South East West up and down, spatial dimension, but it has this weird restriction
that I can only move in one direction in that dimension. Why does it have the arrow of time? Well,
that is a hotly debated topic that will continue to go on, but some scientists, some cosmologists
feel a lot more comfortable now saying things like, oh, that's just because in the early universe,
things were in a very ordered state. And so the only place it can go is become more and more
disordered and so time passes. That if the universe began in a maximally disordered state, just a
blender of everything was maximally randomized, that there would be no passage of time.
There also wouldn't be galaxies or people or radio shows or thoughts. So some people feel very
confident that it's a cosmological question. The question is, why did the universe begin in such an
ordered state? That's the big mystery. That's all for this episode of How to Keep Time. This episode
was hosted by Ian Bogost and me Becker Rashid. I also produced the show. Our editors are Claudine
Abade and Jocelyn Frank, fact checked by Anna Alvarado. Our engineer is Rob Smersiak. Rob also
composed some of our music. The executive producer of audio is Claudine Abade and the managing editor
of audio is Andrea Valdes. Becker, I was going to tell you a joke about time travel, but you didn't like it.
What? No, I didn't. I don't. I'm overly fond of the joke. Oh, I get it. I get it. I get it.
