Redefining the Second

A new type of clock might require a new definition of what a second is. Is time about to turn upside down?

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Episode Transcript

Speaker 1 (00:00):
Brought to you by Toyota Let's go places. Welcome to
Forward Thinking. Hei there, and welcome to Horrid Thinking, the
podcast that looks at the future and says underneath the
big clock. At the corner of Fifth Avenue and twenty
two Street, I stuta and waited for a girl I

(00:21):
knew at the spot where we agreed to meet. It
was four minutes of two. I'm Jonathan Strickland and I'm
Lauren Folk. Bob and our third co host, Joe McCormick
is not with us today in his place as an
extraordinarily long quote. Yes, I I figured, since we would
save time, would Joe not introducing himself, I would take

(00:42):
that time and repurpose it for an even longer quote
from one of my favorite bands of all time. Fair Enough.
You know, some day we should really put together a
playlist of all of the songs that would have mentioned.
Some of them are not safe for work. Like I
try to, I try to avoid those, but sometimes when
I I get a little, I get a little rambunctious, punch,

(01:06):
a little bungee. At the end of the week, Vim
and Vinegar, and especially when it's like two minutes before
we're supposed to start recording, and I realized, hey, I
don't have a song lyric to go at the front
of the show. I have to admit that every single
time Joe and I are are podcasting alone with without
you and what you will be doing very soon, we
will because you are going on vacations. I will. I'll

(01:26):
be cruising around. That is I believe where Joe is
right now, although he could be following my footsteps to Europa.
Every time that Joe and I are in the studio alone,
like we we always it's like knol hits record, Null
are super producer, and then one or the other of
us goes, we haven't chosen a quote yet? Why did
Jonathan start that? As like a standard way of opening

(01:49):
the show. What I should do is also go back
and find the first episode where I did that and
just start writing down, like how many times has have
you used the same four songs? Right? I know that
I know that there are certain songs I've used more
than once, and in fact, I almost started this one
with a song I'm pretty sure I've used before. But

(02:10):
all of that put aside, we're wasting time and time
is precious. Time is so precious. Every second counts in
every millisecond, every nanosecond counts, and we were learning that
what we think of as a second may not actually
be a second. No, well kind of okay. So so
news broke at the end of May, the year which

(02:32):
we are recording this, in that researchers had created a
new clock so much more precise than existing clocks that
were like maybe going to have to change the definition
of a second. And that got us thinking about the
history and the future of time keeping, right, And this
also means, by the way that we have to redefine
what a second is, by its very nature, we're eventually

(02:54):
gonna have to readefine one, a New York minute really
mass fair enough. It's not that our idea of what
a New York minute or or a second is wrong.
A second is a second. It's the machines that we
used to tell time that are that are wrong or
at the very least imprecise. So okay, you know how

(03:16):
like how like digital clocks that aren't connected to the internet,
like like the clock in your car, or an analog
risk to watcher a wall clock, you know, analog meaning
like has hands and gears, like like it's the kind
of clock where you look at it and then you think,
I remember, I used to know how to tell time
this way. When I was first writing these notes, I

(03:37):
I originally started to type old fashioned and then stopped
myself because where I felt so anxious and where you
could at least say, like when Mickey's big hand is
on the two and his little hand is on the three.
But but so these clocks that aren't connected to the
interwebs slowly go off time, right, And that's because the

(03:57):
mechanisms that drive them aren't white measuring seconds correctly, and
the difference slowly adds up until it's noticeable to even
our very slow brains. Right. And we could be talking
about fractions of a second of an error, but eventually
those fractions of a second add up to a second,
and eventually those seconds add up to a minute. Now,

(04:18):
this takes a lot of time, depending on how precise
that clock happens to be, But even even if you're
talking super small errors, it does add up over time,
oh absolutely. And while it may not be terribly important
to us, there are mechanical applications or digital applications rather,
in which it becomes very very important. Yes, and uh,

(04:40):
clocks these days are are even even old fashioned analog
clocks are really pretty good at doing what they do.
But that has not always been as precise the case. Yeah,
As it turns out, if we want to talk about
the way we are now being able to to find
a second and keep that time as precisely as we

(05:04):
currently know how to do it, behoods us to look
back into our distant past and learn about the history
of time keeping. Ah. Yeah, because the concept of a
second is, like in the Grand scheme of humanity, relatively new. Yeah, yeah,
especially when it comes to time. In fact, the original

(05:25):
version of a second had more to do with geography
than with time passing. So you know, I was gonna
bust out the way Back Machine, but I don't know.
Do you think I could handle a trip all the
way back to ancient Egypt? I mean, we haven't taken
it that far back in a long time. We I
don't think I've ever taken it that far back. Do
you think it's safe to be in the way Back

(05:47):
machine and talk about time that much? Do you think
it's going to get mad at you could get a
little time you want? You know what? You only live
once into the way back machine. You go, okay, all right,
now we just have to here's the problem. The all
the digits are hieroglyphs when you want to go to

(06:09):
ancient Egypt. So it's let's see it's this is ticked
off kitty cat uh uh, snakehead person and block. All right,
I got it right in the first try. Okay, So
here we are back in ancient Egypt. Now, to be fair,

(06:30):
we believe that timekeeping may go back further than the
ancient Egyptians, but it's so uncertain that I don't even
trust the way back machine. Yeah, there are there's a
possibility that the Sumerians had this covered pretty much right,
but we don't have any evidence of the Sumerians actually
building any sort of time keeping device of any sort. Also,

(06:53):
my cuneiform is really rusty. Yeah, I I I'm barely
hanging on with the hieroglyphs as it is. So one
thing that we should mention though about those Sumerians. They
had something that will later on factor in importantly in
the timekeeping discussion. They loved the number sixty a lot,
like a whole bunch. Yeah, the Egyptians loved the number

(07:15):
twelve and the Sumerians loved the number sixty, and sixty
is kind of a cool number. It makes it really
easy to deal with certain fractions because there's so many
numbers that are uh that sixty is divisible by so
one through six all of those are divisible, or sixties
divisible by all those uh ten, twelve, fifteen, twenty, and thirty,
which starts to sound familiar when you start thinking about clocks.

(07:36):
And so this, this this base of six kind of
concept is something that was adopted by a lot of
civilizations from that time and and and location. Right, the Babylonians,
they said, hey, you know, we didn't dig everything you
Sumerians did, but we like this sexygesimal base system. Uh
So we're gonna use that for our astronomy. Astronomical calculations.

(07:59):
We're gonna when we're exploring stuff in the sky and
we're describing how it moves and the relationship of different
stars to one another. This is the bass system we're
gonna use because it makes it very easy to to
divide by all these different numbers. Sharing kind of based
on that. The Greeks also picked it up, yes, and
so that ended up being very important further down the line.
But we'll rejoin that, because that's like medieval Europe, y'all.

(08:21):
When we have to get to the point we're applying
it to time. So if they weren't using it to
describe time, what were they using it for. Well, besides
the astronomical calculations, they were starting to talk about using
it to describe geometric features and also the describing geography itself. Yeah,
not not just space geography, but geography right here on Earth. Yes, yes,

(08:44):
so that you could be able to say things like
where one place is in relation to this other place,
other than just all right, you're gonna go down this
road away for about five minutes, and then you're going
to take a rat turn the yield crisp crane. If
you see a guy playing a banjo, you gone too far,
turn around, come back. Yeah, that's that. I wish that

(09:05):
I knew the ancient Greek for crispy cream, yeah, or
banjo at any rate. Uh. The sexogasmal system was used
to help define these things and arrest knees. Use the
system to divide a circle into sixty parts to create
a geographic system of latitude. Um Hipparchus normalized these lines,
making them parallel because before they were kind of wavy.

(09:27):
The essentially well arrest the knees used them to connect
places that he thought were particularly interesting, which didn't necessarily
mean they went in a straight line. They might lean
a little to the right, like, hey, this place is
kind of cool, you might want to check that out.
D Yeah. So Hipparcus was like, no, we're gonna normalize
this stuff, make it a lot easier. And he also
developed a system of longitude, which had three hundred sixty degrees.

(09:50):
Then you have Claudius Ptolemy, who expanded on this and
subdivided the three sixty degrees of latitude and longitude into
smaller segments. So he divided each degree into sixty parts,
and each of those sixty parts he's subdivided into sixty
smaller parts. Okay, so so so that's where you get
that's where you get minutes and seconds, right. The first

(10:11):
the larger subdivisions were known as the partists minute prima,
or the minutes, and then you had the second ones,
known as the partisan minute secunda or second minute, or
later just second. But it would take more than a
thousand years for that stuff to be actually applied towards timekeeping.
It was really applied toward map making and geography. Okay,

(10:33):
but so I mean around the same time ish stuff
was happening with early forms of clocks, Yes, sort of
the Egyptians. You know, if we look around right here,
you just look a little bit over to the right. Okay,
you notice there's that big tall obelisk over there, all right,
So that obelisk, it's for a real important reason. It's
there to tell you when it's in the early part

(10:55):
of the day versus the later part of the day. Yeah,
in case you're not aware that it's now later than
it was earlier. You can look at the shadow. I've
taken naps where I've gotten up really confused. So actually
that that could be very helpful that moment where you
wake up and you aren't even aware of which pyramids
you're sleeping, like what time of day it is. So yeah,

(11:17):
these are were very basic clocks. They essentially divided the
day up into before noon and afternoon, but they also
would show when the longest or shortest day of the
year happened to be. If it was the longest day
of the year, the shadow would be shorter. It was
the shortest day of the the year, the shadow would be longer,
so you could tell kind of the time of year. Yeah,

(11:38):
so you'd be like, wow, it's really cold out. Also,
shortest day of the year. Interesting. Um, So the sun
dial itself would show up in fred BC. So this
is like two thousand years after those obelisks were the
early stages of timekeeping. Now these this is also courtesy
of the Egyptians. So we're just gonna stay here then

(12:00):
chat about it. The device, the sun dials, had multiple
divisions on it to help divide up the day a
little bit better. Also, once you got to noon, you
had to turn the sun dial a hundred eighty degrees
around so it would continue to keep time properly. So
this is the first instance of having to wind a
clock so that it keeps time. Um. So the Egyptians

(12:22):
divide the daylight hours into twelve segments. They were really
big on that number twelve, remember, which is fortunate since
again sixty is divisible by twelve, so that will come
in hand you later. So they thought, let's divide up
the day into twelve, the daylight hours into twelve segments.
So there became twelve periods or hours of daylight in
a day. But since the amount of daylight changes throughout

(12:44):
the year, then the the length of an hour changed
throughout the year. Okay, So so light time was was
twelve hours to twelve periods, and then nighttime was night.
Nighttime at first was nothing. Nighttime was just not the
day was just go go home. It's just like there's
nothing to do. Go to sleep. You know, there's no

(13:08):
you don't have Netflix, we have only so much oil
to burn. Go to sleep. So yeah, and at first
nighttime was nothing. But then the astronomers in Egypt, they
began to develop tools where they were studying the movement
of stars, and they divided up the night hour nighttime
hours into twelve as well. So you had twelve nighttime

(13:29):
hours twelve daytime hours for a total of twenty four
periods in a day. Right, And they again were not
fixed length, right, It all depended on what time of year.
So literally, in the summer you had longer hours than
you did in the winter. So time did not pass
the same way from a from the perspective of counting
the hours, it passed the same way in a different sense.

(13:51):
If you're not concerned about what quote unquote time is it, uh,
that's trying to think about going about your day like
that is very confounding to me. Well, as it turned out,
most people back then really just need to know is
it early enough for me to do work? Is it
getting to the point where it's going to be too
hot to do work? Is it the time to eat?

(14:13):
Is it the time to not be awake anymore? Really
was pretty you know, there weren't a whole lot of
evites that people had to respond to with yes, no,
or maybe. They were really kind of simple in that way. Now,
the Greeks were the first to introduce the idea of
fixed length hours, but they did this so that they
could make astronomical calculations. They didn't do it so that

(14:33):
people would keep regular time. In fact, most people didn't
bother with that. They stuck with the more casual variable
our system, and in fact that would hold true until
the Middle Ages. Um, but that's not the only type
of clock that was around at this time. Oh yeah.
Also right here in ancient Egypt, where we absolutely are,

(14:56):
were water clocks that were probably developed here. Again, you know,
like it's basically whatever you dig up is your evidence
for what was developed when and if it didn't survive
then you Yeah, but so one was water clock was
definitely found in a Menhotep, the first tomb, dating from

(15:17):
around five b C. And uh, they water clocks covered
a few of sundials or or astronomy clocks pitfalls because
you could use them when it was cloudy, crazy um,
and you could also use them as stop watches. The
Greeks would later pick up on them too, though not

(15:38):
until around like three b C we think, and they
called them clip sidras, which I love, which basically means
water thieves. And it's interesting they're called water thieves. It's
specifically because of the physical way the clock keeps time, right, yeah, yeah,
So so the idea here is that you've got a
stone bowl with a very small hole near the bottom

(16:01):
through which water would flow hypothetically a kind of sort
of more or less constant rate. You put this, You
put this bowl with a hole in it inside a
larger basin that's filled with water, and the water will
slowly fill the bowl if if, if the inside of
the bowl is then marked with lines, you can tell
the rough passage of hours by watching the water mark. Yeah,

(16:23):
I've seen a similar one where it was again going
back to the Egyptian times, where you had a container
with a very small hole in it, and it would
allow water to flow through one container into a second container.
And the second container have a bobber in it. Oh,
sure that had a water mark that could tell you, Yeah,
you look at the bobber and you'd say, all right, so, uh,
three marks have gone by. We're going to call those hours.

(16:45):
But keep in mind that these devices also weren't precise
time keeping devices. A rough idea. Yeah, and and I'm
sure that I mean, you know, as water war would
change the shape of the whole of the given device,
your your concept of a pure it of time would
would also change. But okay, so, uh supposedly devices very
much like this. We're used to time speeches in courts

(17:08):
of law circa four thirty BC in Athens, so even
and ancient Greece we told our politicians, yo, hey, shut
up for serious, come on, man, sit down, John They
and okay, I think I think we're going to finally
have to leap ahead a little bit. Or do I mean,

(17:28):
I mean, do you want do you want to save
it for medieval times or do you want to you
know what? We we can save it for medieval times.
I'm a little partial to medieval times, Okay, fair enough,
fair enough, so so I'll just mention that that these
water clocks went mechanical after a few hundred years by
by letting water the Grecian water clocks, I should say,

(17:49):
by letting water drip measuredly into a chamber like you
were just talking about, you can you can raise not
just a little bobbin, but like a floating piston, and
therefore do simple work like like pushing a marker or
even a gear to turn a pointer. And so between
like one d b c E and five hundred CE,
Greeks and Romans both we're trying to make the flow

(18:11):
more constant by regulating the water pressure. And as a
result of that, some of the devices that they were
making could like ring a bell or a gong when
the water would hit a certain point, or they would
even like push a mechanism to open little decorative hatches
containing small figurines that would dance around or or move
astronaut astrological models. Yeah. Um, And And meanwhile in China,

(18:34):
mechanical water clocks were also in use from around two
hundred through around thirt hundred CE, including at least one
that used this big old water wheel like story and
a half tall water wheel to power dozens of elaborate
sounds and mechanisms that would dance around and do weird
little stuff. Man, and I thought the uh, the church

(18:57):
near my neighborhood, whenever it's noon or six pm, it
goes pretty much bonkers with its chimes. I imagine it
had to be even more spectacular with something along those lines,
although maybe not necessarily quite as regular, Yeah, I would
imagine not, but still still a party. Yeah. Yeah, So
let's get back in the way back machine. We're gonna

(19:18):
actually jump ahead to medieval Europe and we'll we'll get
out there. So did you bring your nose? Come on,
I worked the Renaissance Festival. I've been to dragon Con.
I can handle medieval Europe. Here we go, Here we go.

(19:43):
Welcome to medieval Europe. Huzzah. Where food is on a stick.
And this doesn't look like the Resaissance festival and all.
This is kind of awful. Yeah, I don't see any
chicken fried bacon. There's actually awful in the street in Soul.
That's the kind of awful this is anyway, So it's

(20:03):
worse than our pus Field trip. Yeah, that was man.
You never thought you'd look back on that with like nostalgia.
But here we are in fourteenth century medieval Europe. This
is about the time where mechanical clocks began to become
a thing. And at those in those early clocks, they

(20:24):
had our markings. Uh, some had minute markings, but none
of them had second markets. And uh. So it would
actually take about a couple hundred years really sixteenth century
medieval Europe where you started seeing minutes as a standard
marking of time. And this is where we take that

(20:45):
concept we talked about with the geography, and it was
converted into a time keeping concept. The idea of well,
we've got these these twelve periods of daylight and twelve
periods of nighttime that the uh, the Egyptians had proposed.
The Greeks had formalized that into actual fixed length hours,

(21:05):
uh for their calculations. We're gonna do that for the
purposes of keeping time. Then we're going to subdivide that.
And because they were working with twelves and twenty fours,
they said, how about we look at sixty. We're looking at,
you know, a division of sixty smaller increments that make
up one full hour, and then eventually you think about

(21:29):
that long enough and you realize, all right, well we
can subdivide that even further. A minute is still a
pretty long amount of time depending on what you need
to do. Right, some things, a minute's no time at all, right,
If if it's something really fun that you love to do.
Maybe you're riding on a horse, jousting your Henry the eighth,
a minute is like no time at all. But maybe

(21:51):
you're being accused of witchcraft, being dunked under the water.
A minute's a really long time. At that point you're
going like, can we break this period up a little bit?
And maybe we and look at like a fifteen second
interval if you're gonna be you know, slowly like drowning me,
like i'd like to can we negotiate this at all?
So they looked at the round face of the clock

(22:11):
that they had designed, and the division of the day
into really twelve segments. You can think of twenty four,
but really most clocks are twelve segments, right, And then
we just amend either a M or p M in
our brains to denote whether it's in the morning or
it's in the evening UH, and they adopted that sexic
asimal system, and each hour was divided by sixty and
two minutes and dividenes again in sixty into seconds. And

(22:34):
this was the first time we really had a definition
of a second in terms of timekeeping. UH and and
all of this, I imagine was also partially driven by
just the mechanical complexity of clocks in the capacity. But
because a mechanical clock, if if you guys aren't familiar
with the inner workings of a of your basic wall
clock or watch or something like that, is based on

(22:54):
a coiled spring that you apply tension to buy either
winding it or exposing into some kind of electricity like
electrical pulses. And and then UH in the case of
these these earlier clocks, the capacity of gears that you
attached to the spring to to react in in regular movements. Yeah,

(23:16):
it's kind of like a transmission, you know. You use
smaller gears and larger gears to dictate exactly how frequently
a gear will turn within a given amount of time,
assuming that in fact the clock is wound, and then
you get the mechanical UH performance where it rotates once
an hour. For that you know, for the uh, the

(23:38):
the little the little mickey arm, yes, and and so so.
As as the spring making and gear making techniques became
more complex, I'm sure that people started going like, surely
we can make this more complicated, let's put some seconds
in there. And in fact, you know, for a lot
of people's seconds weren't really that important, not yet anyway.
As much as I joked about the whole dunking of

(24:00):
people to see if they're witches or not, that was
not really on the forefront of people's minds in that
particular scenario. Yeah, but the second was really um thought
of as important for making those astronomical calculations, and in fact,
we attempted to standardize it with the International System of

(24:21):
Units and the The definition for a very long time
was that a second is a fraction of a mean
solar day in a tropical year. But all of that
changed in nineteen sixty seven. So I think we should
probably just jump the way back machine, go back to
the studio. Okay, Okay, that's that's fair. I don't I

(24:44):
I'm pretty much done with history for the day. Yeah,
I think we can talk a little bit about the
the nineteen sixties, but um, you know, we don't need
to go there. That's not that long ago, all right,
and the smells will be barely exciting. Yeah, okay, we're back, man.

(25:08):
I just realized we've seen the Beatles another time. Yeah, yeah, sure,
sure we can. We can always rev it up again.
Uh okay. Actually, before we talk about the nineteen sixties,
I need to talk for a second about for a
second about the nineteen forties, because there was a physics

(25:31):
professor at Columbia University by the name of Isidor Rabbi.
I think I'm saying that right. Uh. And anyway, he
proposed that a very precise clock could be constructed by
measuring the vibration of atoms, and as far back as
the ninetties had been experimenting with with this discovery that

(25:52):
when some atoms are exposed to some wavelengths of electro
magnetic energy, those atoms vibrate very, very consistently, So you
can measure the oscillations and then use those to build
a standard for the passage of time. And what is
actually happening here is that if you have the right
frequency of energy hitting a particular type of atom, it

(26:15):
excites the electrons in that atom to higher energy bands
and then those electrons will come back down to their
normal energy band. That's the vibration there. But if you're
talking about a resonant frequency, that in that we talked
about resonance before resonance is this idea that you have
found a frequency that resonates with a particular material. In

(26:38):
this case we're talking about atoms, and it makes them
vibrate themselves. So, for example, we see this in the
macro level with the opera singer singing that note that
is resonant with a particular crystal glass, and it causes
the glass to shatter. Uh same sort of thing. Instead
of shattering atoms, you're just making them wiggle on wiggle,
very precisely, and very quickly, very very quickly, as it

(27:00):
turns out. So, based on all of this, in nineteen
sixty seven, the International System of Units wound up changing
their definition of a second to the vibe to a
particular vibration of the ces um atom or a scum
atom a given sazon atom at any given time um
and these suckers vibrate so consistently at when exposed a

(27:21):
certain wavelengths of light, and uh so a second was
defined as nine billion, one ninety two million, six hundred
thirty one thousand, seven hundred and seventy cycles of those vibrations. Well,
there's your problem. I lose track right around four billion.
I just lose interest. But now that's amazing. The thought

(27:42):
of being able to to define a second as something
that is more than nine billion vibrations of a particular atom.
Now you might wonder, how the heck can you turn
that into an atomic clock? Yeah, how do you measure that?
That's pretty weird. So I'm gonna do my best to

(28:04):
describe this. Please keep in mind I was a liberal
arts major. So here we go. First, the thing that
these are the earlier atomic clocks I'm going to talk about.
Now we have a different type of atomic clock will
be chatting about shortly, and then and even more advanced
type of clock to talk about the future of the second.

(28:24):
But first, you would heat caesium so that atoms would
boil off of the gas typically, and you would pass
that down a tube that's maintained at a high vacuum.
So then you would use magnetic fields to sort through
the caesium atoms and passing the ones with the right
energy state to the next level. So in other words,

(28:45):
you're separating out ions from from regular caesium atoms, and
you want just the specific ones that are going to
react to the microwave radiation you're going to pass through it.
So once you've sorted them and all the ones that
you want are going the right pathway, the atoms will
then pass through a microwave field that has a varying
frequency within an extremely narrow range of frequencies. One of

(29:09):
the frequencies within that range is that magic nine billion, million,
six seven seventy hurts that corresponds with the vibrations of
the caesium atom. So when a caesium atom encounters a
microwave at that frequency, it changes its energy state. It wiggles,
and the atoms continue on, and another magnetic field separates

(29:33):
out those that had their energy state altered by the
microwaves and the ones that did not have their energy
state altered, so the wigglers versus the non wigglers exactly,
and a detector picks up those atoms the wigglers, and
that output is data that is proportional to the number
of caesium atoms striking it. In other words, the output
says how many atoms were wigglers. And then that way

(29:56):
you can actually start to tune your device so it
is closer to the proper frequency, and you'll see that
number go up. That that number goes because you'll hit
more ces um adams with the right frequency. You start
to narrow it down until you get just the right tuning,
and once you're there, you're you stop. You have you
have reached the point where you are creating the pulse

(30:18):
that is a second each time um and then you
So what you would do is you take your frequency
number that you had arrived at and the number of
uh that that really big number we've said a few
times already, and when you divide the two, it should
end up being one. That means one second. Right, So
it's it's a little weird to think about, but yes,

(30:40):
it all comes down to how many of those wigglers
are you picking up? And as you pick up more
and more, you get these pulses that end up being
exactly or at least mostly exactly one second. It turns
out that as we get better at measuring things, our
definition of what exactly is changes. Now. I love that.

(31:01):
So atomic time keeping created a new approach called coordinated
universal time, which, despite the fact that would usually make
the acronym cut cut, it's actually U t C. That's
what's universal time coordinated. I guess. In the United States,
we depend upon the U. S. Naval Observatories, master Clock,
and the National Institutes of Standards and Technology in Boulder,

(31:24):
Colorado to regulate our time. They're the ones telling us
what time it is. In other words, so interesting fact
U t C and astronomical time don't quite match up.
So we've got a second that is very precise. But
when you change it to the real world and the

(31:45):
way that the Earth rotates, it doesn't. The Earth does
not rotate according to our beautiful math. In other words,
so once in a while, I can't trust it for anything.
I know it's I mean, i'd leave, but it's where
I've got all my stuff. So it turns out like
every now and again, we have to throw in a
leap second, leap second, leap second every ten years or so,

(32:08):
You've got about eight minutes out of that entire decade
where you where some of those minutes, those eight minutes
they actually have sixty one seconds as opposed to sixty seconds. Okay,
So is so is this because are these clocks aren't
quite precise enough. Even though we've gotten this precision down
to the vibration of an atom, they're they're just not

(32:30):
as precise as they could be. Well, that's that's definitely
part of the problem, because as time goes on, the
slight imprecision of these clocks becomes more and more noticeable,
and you have to correct for that. And it's really
interesting that such a thing could, even like it's so
hard to imagine something so small we're talking about the

(32:51):
difference of nanoseconds here could actually matter that much. It's
almost like if you were to look at, say, an aunt,
and you've said that little any ant couldn't do anything
to me, and then you saw ten million ants and
you thought, so when there are ten million of them,
they actually do matter. It's sort of the same with
these name seconds. Uh. But let's talk a little bit

(33:12):
about a slightly newer version of atomic clock, the microwave
fountain clock, which does not involve putting one of those
little fountains from like a uh, like a bookstore or
something inside a microwave. Don't do that. That's not how
you're gonna get a microwave fountain clock. That's how you're
gonna get a broken microwave. So they use a slightly

(33:34):
different method, but they still depend upon caesium atoms and microwaves.
So you take caesium gas and you introduce it into
a chamber that has six lasers, all mounted at right
angles to each other. So you've got like up and
down and uh and like some on the on the
actual walls point and inwards. It looks like a James
Bond trap, but instead of saying no misr caes um,

(33:57):
I expect you to die, the lasers are actually slowing
down the movement of those caesium atoms. Okay, so it's
an atom trap, not at James Bond trap exactly. And
we also know that movement and heat are essentially the
same thing. Right as adams move, there are there warm.
When you start to slow them down, they cool down.
So the goal is to cool them down to close

(34:19):
to absolute zero. Once they're at that point, they are
forming into kind of balls of atoms. So you've got
these little caesium gas balls that are suspended because they've
been slowed down so much, and then you use a
couple of lasers to push them up into a microwave chamber.
This is the fountain action. So if you imagine a fountain,

(34:42):
that's that's just shooting straight up, the water shoot straight up.
In this case, lasers are pushing that caesium ball up
into the microwave chamber. And then those particular lasers, the
ones that are pushing the caesium atoms, turn off. Then
you've got microwaves within that chamber. Some of the microwaves
are at the proper frequency to make caesium vibrate, and

(35:03):
when they do encounter the caesium atoms, the atoms will
change energy states. And as those caesium atoms leave the
microwave chamber, they encounter yet another laser. We love our lasers.
Caesium atoms that have been altered by the proper resonant
frequency fluoresce. They light up and a detector makes note

(35:24):
of that, and then the system is dialed in. So
it sounds very similar to the old atomic clock, right.
They dial it in until that maximum fluorescence is achieved,
and that defines the natural resonance frequency of the caesium
atoms and can be used to define a second But
they these also as accurate as they are, they do

(35:46):
not keep time perfectly forever. Yeah, they do lose time
over time. And uh, and we're talking about like a
nanosecond a month, which seems nothing. I mean, I was
going to waste it anyway. I was probably spending that
playing bulled. I was probably playing Overwatch. Okay, uh, but

(36:09):
but but it does but it does that up eventually
and and especially digitally, so nonetheless, Okay, we should say
that the atomic clocks are are really cool for a
number of reasons. I think a number one because they
are what keeps our our geo syncritous orbiting satellites basically

(36:29):
not running into each other. Right. Yeah, when you're talking
about things like satellites, like communication satellites, or you're talking
about GPS satellites, you need to have extremely precise time
keeping in order for those operations to to work properly.
And in fact, this comes with a whole host of
problems and challenges. Um, but you're looking at an accuracy

(36:51):
that needs to be down to billionths of a second.
So when you have like a nanosecond error in there,
that's actually a big deal. So each GPS satellite actually
has four atomic clocks on board, and there are twenty
four GPS satellites in orbit, and uh a GPS receiver
on the ground can determine its location by triangulating broadcast
signals sent from multiple GPS satellites. And then what does

(37:14):
is it looks at the time stamp on each of
those factors in how long would it take the signal
to travel from that time stamp and where you would be.
You actually have two answers to that, but one of
them happens to be inside the Earth, So your GPS
usually ignores that answer. Generally, Yeah, it's like, all right,
obviously can't be that one, so you have to be here.

(37:37):
But knowing that you have these potentials for errors, you
actually that that translates into a less precise positioning. When
you're getting your read out, it may be accurate to
just a few meters, which is fine if you're traveling
around and you're driving and you know, generally speaking, you're
not gonna have an issue where you're suddenly realizing need

(37:57):
to turn a mile back. Share it, but it does
explain why. For example, if you have your WiFi off,
your GPS may think that you're on the other side
of a bridge that you haven't crossed yet, or something
like that or yeah, or I'll read you the same
instruction off twice because it's just glitching as to where
precisely your your car is. Or if you're using something

(38:19):
like a car service app and you see where you
are and you know where you are based like you
see where you are on the map and you see
where you are in real life, and you realize that
if you pen the point that it shows you on
the map, you're gonna have to walk another block to
get to that car. You're like, no, I want to
be right. Those apps are particularly bad at that. I

(38:42):
don't know what the issue is. I don't know if
it's on the app side or if it's my phone's GPS.
But anyway, So, one of the cool things about space
and satellites in time is that you have to take
into account both special and general relativity. That's always sighting
because it messes with dime. So right, okay, because because

(39:07):
satellites are are are moving relative to a single point
on the ground. Yes, well, and if you're talking about
a geosynchronous satellite, it's moving. It's moving like if you
were looking up you would always see it, right if
you were directly below it, which means it actually has
to travel faster. It's going a further distance in the
same amount of time, so it's traveling faster than the
air's rotation share the same way that a track runner

(39:28):
on the outer side of the track is going to
have to run a little bit faster than the inner
truck crowder to keep up. Exactly. So you start to think,
all right, we're talking about time dilation here, how does that?
How big a problem is that? It's pretty huge. So
we just talked about how a nanosecond a month was
a big deal. First of all, you have to look
at special relativity. That's the one with the time dilation effect.

(39:51):
That's when you're talking about the speed that ends up
about seven micro seconds of difference. That means the clocks
aboard the satellite, due to special relativity, we'll move seven
micro seconds slower than a clock on the ground. Kay,
So that means you have to figure that out factor
that in except you also have to remember about general relativity.

(40:14):
The general relativity tells us that the satellite is orbiting
high above the Earth, where the curvature of space time
is less than what we experience here on the Earth's surface.
Exactly the Earth is a giant mass. For us, it's
a giant mass. For the Sun, it's nothing, but for
us it's for us, it's pretty big. Again, it's where
we keep all our stuff. So there's a pretty big mass. Uh.

(40:34):
And so that it so. So a clock here on
on on the ground, the clock on my on my wrist,
if I had such a thing, would be it would
actually be going faster. It would be going faster because
of the curvature of spacetime, so it would actually be
going your wristwatch clock would be going slower than the
one that's aboard the satellite. So special relativity says that

(40:57):
the clock aboard the satellite is gonna go a little
slower than ours. Right, that's the whole idea that if
you were to travel it near the speed of light
and came back, time would have passed less. Time would
have seemed to have passed to you than to everybody
on Earth. But according to general relativity, it's the clock
and the satellite is going faster exactly, so microseconds, so

(41:18):
you have to, yes, exactly, You've got to take the
seven microseconds where it would have been going slower, and
the forty five microseconds where it would be going faster,
and you come up with thirty eight microseconds distance difference,
and so GPS systems take this into account. I know,
I just had GPS systems and I'm like saying, a
t M machine and pin number, But it doesn't matter.
That's not what I was cringing at. Just the math

(41:40):
caught up with me. Yeah, thirty eight microseconds difference, so
you have to account for that. And we're looking for
an accuracy down to twenty to thirty nanoseconds. So nanoseconds
are much smaller than microseconds. It's a big deal. And
and and real errors would pile up due to these
due to these mistakes exactly. So if we did not
correct for us, on the first day, we'd be thinking, uh,

(42:04):
all right, well this isn't great, but it's you know,
it's it's it's usable. And then as the day goes
on would be thinking, wow, this is this is getting
less cool. And then the next day we'd be thinking
this is completely inaccurate, because the errors would be enough
to account for a ten kilometer error per day. Yeah,

(42:27):
so these little bits of time really make a big difference,
which is why you want to have a really precise
timekeeping device. Um. So, one way that they correct for
this is they actually make sure that the clocks aboard
the satellites tick at a slightly slower rate before putting
them up in orbit, because then general relativity will take

(42:48):
care of the rest and they'll start ticking at the
rate that they should be taking at, which is kind
of like you know that sort of thing where you've
already planned for the thing to go wrong, Like you're
not trying to stop the thing from going wrong. You're
just like, well, yeah, well this is gonna happen, so
here you go. This is what my life is now.
It's just how the that's just how physics work, y'all. Yeah,

(43:08):
uh okay, but that's not even atomic. Clocks are not
even the most precise type of clock that human people
have created. I know where you're going, and I'm already crying.
I know what. I'm sorry you and you got to
the notes faster than I could, so it's your fault. Really. Yeah, alright,
So the clock that inspired us to do this episode

(43:30):
is a type of optical clock. Optical clocks, and I
looking at the clock on my wrist, hypothetically, if I
had such a using optics right now. Uh, these use
these depend very heavily on lasers, and again with the lasers.
So we had in our notes how they work. And
I almost just put a frowny face sticks to it

(43:53):
because I started reading how this works, and it's so
complicated that, first of all, I gotta be upfront, I
do not understand it. All right, that's just me being
I'm being straight with you guy. Yeah, yeah, neither of
us are laser physicists. Yeah, I'm not a laser scientist. Okay,
I'm not a second scientist either. But they're very, very complicated,

(44:16):
and as I was reading it, I just realized that
it would take me probably weeks of study to really
get a basic understanding what's going on here. But uh,
they work with lasers and adams and specific frequencies. And
here's the problem. It's so technical. Uh there are phrases
like optical frequency standards, forbidden transitions. I didn't know there

(44:38):
were such things Doppler broadening and optical clockwork. And I'm
pretty sure I don't understand any of it. Oh yeah,
forbidden transition sounds like something out of Welcome to night
Vale more than exactly so okay, but but can you
can you give us like the very very very basic yes.
So optical clocks they don't necessarily rely on Just let

(45:04):
me put it this way. There are different types of
optical clocks, and they work on different types of particles. Right, So,
with atomic clocks, were typically talking about either caesium or rubidium. Uh, yeah,
I think it's rubidium. But at any rate, we're only
talking about those. The optical clocks there are a lot
more options, so you can talk about certain atoms or

(45:25):
ions or even molecules depending upon the type of optical
clock you've got set up. And the optical clocks can
correct for caesium clock drift, which is good. So they
are more precise. They can divide time up into ever
smaller amounts um, and they are really I mean that's
really important because the more precise you get, the more

(45:46):
accurate your timekeeping is. But what they're essentially doing is
slowing these atoms and ions and molecules down to microwave
frequency standards, which is similar to what the caesium atomic
clock us. Uh So the idea being that light frequencies
are way too fast. Uh, they're much faster than the

(46:06):
micro Even with that nine billion number, that's slow compared
to what the light frequencies are. UM, so it's it's
important to use it to slow it down to these
microwave amounts. But it means that you can actually create
what's kind of called like an optical comb frequency, and
you are able to subdivide those frequencies further and further

(46:29):
and further, which is what allows us to look at
smaller and smaller fractions of a second and make more
and more precise clocks. And we have literally reached the
limit of my understanding. Okay, okay, but part of my
understanding of them is more top level than that. You
just went way deeper than I did. Um but uh

(46:49):
but but I'm but I'm aware of the idea that
they're not considered as dependable as atomic clocks, and that's
why they have not been been used to switch over
the definition of a second as of yet. Yeah, they're
incredibly complicated machines and there are a lot of potential
points of failure, so if something goes wrong, the whole

(47:09):
system doesn't work right, and things go wrong. Technology doesn't
always work, especially young technology where you're you know, this
is still relatively young technology where you're trying to develop something.
And because it's a delicate system and it's very complicated,
and downtime is a factor. Uh. That means you have
to actually account for time required to fix the clock,

(47:30):
which means that like like like like hours or even days. Yeah.
And so while it's offline, you you aren't you don't
have time, yeah, unless unless you pair to this type
of system with another type of system, which is what
essentially is up with this new clock that we mentioned
at the very top of the podcast years and years ago.

(47:52):
It seems like it seems like another lifetime Lauren. Yeah.
So this, uh, the story came from a research team
out of the National a Trology Institute of Germany and
metrology that's a science of measurement and and and while
there are branches of this institute all around the world,
I think there's something so fitting was the Germans, especially

(48:14):
for time. It's just again it's stereotypical, but you just think,
like you know, piseyah. So the specific type of clock
that they were working with is a strontium optical lattice clock.
By the way, there are research institutes in the United
States that also are working on this same technology, and

(48:38):
that's the actual optical clock. The optical lattice is pretty
much what sounds like. It's an arrangement of lasers that
are meant to manipulate those atoms of strontium. So again
back to the James Bond slash mission impossible kind of trap. Uh.
They use a second device to help account for time
whenever the lattice clock goes off line, and that is

(49:01):
a maser. Yeah, it sounds like it, but in fact,
maser's predate lasers, mazers were Masers were discovered or created
in the lab before lasers were. They're similar to a laser.
It is a microwave amplification by stimulated emission of radiation.
So it used to be an acronym. Now it's just

(49:22):
a word, just like laser. Uh. Masers operate at microwave frequencies,
which again are not as high as laser frequencies and
little light frequencies, which means that because their frequencies are
are are lower. I keep saying slower, but I really
should just say lower. I know all the physicists out there,
I've been cringing. I apologize to you guys, but it

(49:43):
means that because you have a lower frequency, you have
a lower level of precision. It's kind of like, you
know again, Like the way I would think of it is,
imagine that you have um a measuring cup, and uh
and I you have a measuring cup, I've got a bucket,
and we each have to say how much water is
in a pool. And so it's gonna take us a

(50:03):
long time to figure this out. But you're gonna be
a lot more precise with your answer than I will,
although you'll get to your answer quicker than I will, relatively.
So I didn't say how big the pool was. If
it's a big enough pool, then both of us have
just wasted our lives at any rate. The same idea
with the mazer. With the lower frequency, it can take
less precise measurements. So what the team did was they

(50:24):
used the maser to cover for the downtime when the
optical clock was offline. And the way they did this
was they then they applied an optical frequency comb to
divide the maser's measurements into smaller units, similar to that
to the optical clocks. So while the optical clock was
still working, they tuned the mazer's frequency so that the
output most closely resembled that of the optical clock once

(50:46):
fed through this comb. Yeah. So they're like, well, the mazer,
while we know it cannot take as precise measurements as
the optical clock, if we apply this optical comb to it,
we can kind of fake it, sort of. And as
long as we have attuned the two together, then we
can at least depend on this until we can get

(51:06):
the other one working. Sure. Yeah, and then when the
optical clock comes back online, then you re a tune everything,
make sure it's all flowing together and kind of cut
the difference. Yeah. Yeah, and then you might call people.
I'm like, hey, I'm going to need that six nanoseconds back. Sorry, sorry, sorry, David,
We're gonna have to docu six nano seconds for it.
You took too long for your lunch now. But so so,

(51:28):
in in this experiment that this team published about recently,
they ran a test of the system for twenty five days,
and the optical clock did indeed experience downtime up to
two days at a go. But at the end of
the trial their system was just under zero point to
nanoseconds off. And there's a kind of flashy number that

(51:51):
the press has latched onto and and it's an extrapolation
of that, which is that. Okay, So assuming that the
system wouldn't like degrade over a longer lane of time,
and assuming that we could have somehow started running it
at the beginning of the universe as we know it
a k a. Like fourteen billion years ago, when time
became a thing. Yes, um it, this clock would have

(52:14):
lost only about a hundred seconds over those fourteen billions years. So,
so less than two minutes billion billion, pretty precise. Yeah.
And and and at tom the clocks are pretty good
at that thing too, like relatively but but they but
but it beats him out by a factor of like
a hundred. Yeah. So ultimately, does this mean about the

(52:39):
future of time keeping, the future of seconds themselves? Well, well, okay,
the definition of the SI unit isn't just going to
change overnight. Yeah. In fact, the researchers on this project
said that it would be at least a decade out
for that to change, partially because the technology, right, it's
so young. And we talked about all the fact that

(52:59):
they're all these different style of optical clocks. They don't
all use strontium. They may use something else, and we
haven't figured out yet which one is quote unquote the
best one to go with, as in, the most reliable,
the most precise, that has yet to be decided. This
is still a very early form of research, so it
may turn out that it will take a decade for

(53:20):
that to shake out and for us to say, all right,
this is the optical clock that is best to use
that we're going with, and this is what a second
is now. And okay, so so when we do accomplish that,
we'll we'll have more accurate clocks. Yeah, but practically what
will that do for us? Lots of stuff. Well, first

(53:40):
of all, we hear it forward thinking. We always stress
that pure research ultimately benefits us in ways that we
cannot anticipate. Oh absolutely, I mean, and you know, like
like hurrah for the spirit of scientific inquiry and in
the advancement of physics and all that rad stuff. But
but okay, like like really, technically, we're not doing all

(54:00):
of us, all of this for us, right, human beings
don't miss the nanoseconds that the current you know, gold
standard atomic clocks are accidentally shaving off. That means that yes,
in the spirit of Joe being and not being here,
but in his spirit we're doing this for a robotic overlords. Yeah. Yeah,
So it turns out like the besides the satellite systems

(54:22):
that we depend upon, we have a lot of systems
here on Earth that are really important to coordinate with timekeeping,
including things like our electric grid. But obviously, if we're
going to have more and more technology interacting with one another,
talking to one another, uh, causing things to happen within
our world, timekeeping becomes incredibly important. Obviously, Like if I

(54:44):
if I am walking into a room and I want
a specific outcome to happen through my technology, I want
that to happen while I'm walking into the room, not
five minutes after I walked into the room, or five
minutes after I walked out of the room. Sure, if
you if you have a GPS system that's controlling your
autonomous vehicle and another person's autonomous vehicle, you want those

(55:07):
GPS satellites to be able to hone in on you
well enough to to to not crash them together. Right,
If you have a system that is and like an
external system that's controlling a lot of vehicles, you could
in theory, reduce traffic to nothing, right, because you could
you could have the cars moving impossibly close to one
another incredibly safely. But if your timekeepings off, that suddenly

(55:29):
becomes a lot of bumping and rubbing on the road.
Time and distance are still linked and uh or or
for another example. So back in February, we did an
episode about how machines run the stock market. Computers are
very precisely running the stock market these days, making these
trades at fractions of fractions of a second. The episode

(55:51):
is called show me the zero zero one zero zero
one zero zero if you'd like to go look for it.
I believe that code actually stands for the dollar sign.
That's adorable. Yeah, I think I actually looked that up.
That's how much of a dork I am. But but
so obviously this kind of precision and timekeeping will will
totally matter to to these computers and to to others
like them. You know, just think, Jonathan, how many interactions

(56:14):
and transactions you could complete in a few extra nano
seconds every day? Man, my Amazon wish list is gonna
be sick. Yeah, so we're we've been joking around a
lot and talking kind of about this. This somewhat odd
idea of a second secon time is such a weird
thing right to talk about in a objective, definitive way

(56:36):
when we also are aware that it is relative. It
makes it really kind of mind bindy to to go
on about this. And uh, ultimately, if we get to
a future where people are zooming around the galaxy at
ridiculous speeds, this kind of precise timekeeping will also be
important so that we can have any form of communication

(56:57):
that might be possible as long as they're still you know,
with reachable distances, um and Yeah, if they're going to
be the speed of light, then you're you're never going
to catch up to them, Like the message will always
be behind them until they stop. And then what will
happen is they'll travel at the speed of light and
they'll be like twenty seven light years away and then

(57:17):
they'll stop and then they'll say you forgot your underwear.
I'm like, dude, no, I'm just thinking of how have
that bump in your inbox when you finally right down
and then all of a sudden it's like, oh my gosh,
and it's all adds. So this was fun to talk
about something like this, and we really look forward to

(57:39):
tackling other interesting topics like this in the future. If
you guys have any suggestions for future topics, maybe there's
something you've always wondered. How is that going to be? What?
What will that be like in the future? Let us know.
Send us an email. The address is FW thinking at
how Stuff Works dot com, or you can drop us
a line on social media. On Twitter, we are FW thinking.

(58:01):
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