This episode is sponsored by Brilliant Keeping track of time is tricky enough nowadays,
it’s a whole different story when your clocks and calendars don’t have 24 hours or 365
days, let alone run slower. But that’s barely the tip of the iceberg
of problems with time facing interstellarcivilizations. So today we’ll be closing out our fifth
season for Science and Futurism with Isaac Arthur, and I am your host, the aforementioned
Isaac Arthur. As we say good bye to 2019 and hello to 2020,
it seemed appropriate to discuss time so we’ll be looking at its impact on Interstellar Civilizations
today and we’ll open 2020 up next week by contemplating Time Travel. Of course Time Travel itself is a fairly ambiguous
term. It assumes time normally runs at a set and
uniform pace and that’s nothing like the case. Time runs slower in gravity wells and when
you’re moving fast, and we happen to live in one such gravity well and need to move
very fast to get to any others out in the galaxy in any sort of sane timeline. And ‘sane timeline’ is probably appropriate
because in many ways it’s not the flow of time itself that really matters, but rather
the effect all the crazy time issues will have on civilizations and trying to keep those
civilizations connected. If you think time zones on Earth are a pain
in the modern era of instant communication, that’s nothing compared to trying to handle
time lag issues on talking to other planets with longer days and years, let alone stars
years away in communication time. Now in science fiction this always gets solved
by FTL, faster than light communications or travel, though in truth that only fixes part
of the problem and makes some of it worse. Time zones on Earth are only a problem because
we have instant and cheap communication, prior to that it didn’t matter that it was midnight
somewhere when it was noon for you, because you couldn’t interact with them in real
time. Even in my youth when long-distance phone
calls were rather pricey, the time zone thing wasn’t as big a deal because you didn’t
casually interact with other time zones much. With free long distance calls, remote offices,
and of course the internet and social media, we now have to deal with time zones all the
time. Right now, it wouldn’t really matter what
the day length or year on some planet around Alpha Centauri was, because we’re not talking
to a colony there real time, but on a four year lag, so it’s like sending someone a
very delayed letter or email. If you had instant FTL communication, then
it matters that they have a really different day and year. Of course we don’t have Instant FTL communication,
and aren’t likely to ever have it, indeed we don’t have instant communication even
here on Earth, it’s just so quick that you don’t notice the lag much. We’re mostly interested in interstellar
civilizations today, but it’s worth considering how colonizing our own solar system will alter
our attitude on time and interplanetary civilizations will influence how the interstellar ones develop. Let’s address the elephant in the room though. Without FTL, it doesn’t seem realistic to
have a galactic empire in the classic Space Opera sense, as we looked at in Interstellar
Empires. The Galaxy is a hundred thousand light years
across, meaning a message from one side to another takes a hundred thousand years. We’ll try to look at some ways for doing
that anyway later on, but for now it’s worth remembering that civilization, especially
in this context, doesn’t mean something centrally-run from some capital planet. Colonization of the galaxy doesn’t rely
on galaxy-wide coordination anymore than colonization of this planet by stone age tribes relied
on them all getting together to plan things out. So we do want to consider ways that might
allow cohesive civilizations like we generally have nowadays but we don’t want to limit
ourselves to thinking of them as a prerequisite for interstellar civilization. A developed solar system is an immense place,
even compared to a planet, and civilization got on just fine on a single planet prior
to the radio and telephone being invented, so we’ve no reason to assume the galaxy
would be a chaotic mess just because it was composed of essentially sovereign solar systems
who only have limited exchanges with neighbors. But let’s talk about the time issues within
solar systems, interplanetary civilizations. No naturally occurring solar system will ever
have two planets with roughly equal year lengths for a starter, as you can’t have stable
orbits occupied by two large bodies, with the exception of double planets, and those
will have quite atypical day lengths compared to Earth, from tidal locking, like our Moon
has. The only planet with an even vaguely close
day length to Earth is Mars, where its 37 minutes longer and you’d lose about a day
a month. That would be awkward for a lot of communication
as teams doing shifts on Earth and Mars, say 3 daily shifts, are going to have things cycle
around, so the morning shift in both places can’t coordinate more than a few days in
a row as the folks on Mars will get up 27 minutes later each day. That’s the easy case too, though in some
ways both the Moon and Venus are easier, the Moon has a day and year a month long, and
is in near-instant communication with Earth anyway, so is probably just going to use Earth’s
calendar. Venus and Mercury both have days months long,
and essentially useless for human-activity based time keeping. That will happen on many Earth-like worlds
around orange or red dwarf stars to, which is most stars in the galaxy, as even if the
day were about the same as Earth’s, the year might be just a few months or even mere
days long. Back around our Sun, early asteroid mining
efforts, which are likely to predate any major colonization of other planets anyway, aren’t
likely to want to use the rotation or orbit of a given asteroid as a reference point. Asteroids typically rotate several times an
Earth-Day and they’re small places among a hoard of other objects with different rotation
periods and orbits. Now you might use some major object like Ceres
or Vesta in the Asteroid Belt as a hub for activity and standardize to its local clock,
but that would probably be more likely for something more classically planet-focused
or concentrated like moons around a gas giant. Also we have to consider how space colonization
is likely to roll out in our solar system, which is to say we’re more likely to build
worlds than terraform them, via rotating habitats, and those can have day lengths of whatever
you want. There’s an assumption that Martian colonists
will start their own calendar up and maybe they would, but nobody else really has any
motivation to do so. Time keeping on Earth has to do with human
biology, adapted to Earth, and biology in general for stuff like growing crops. There’s no fields or fertile river deltas
out there for us to go farm, we’d be doing everything inside domes or artificially lit
and environmentally controlled facilities and we can regulate those to our tastes, presumably
Earth-standard - at least until living under Martian daylight becomes routine - see Springtime
on Mars for more on that. So you’d probably end up with everyone using
Earth-standard for exchange between places, and probably internally for most places too. Though that might alter a bit too. We’re coming up on a leap year in 2020 and
I could easily imagine those being gotten rid of in some standardized system. You also presumably need to pick a time zone
that was the official midnight everyone used. Metric doesn’t work well for time units,
or rather decimal doesn’t, folks often confuse base 10 with metric, which just happens to
use it. Our time measurement for days is still in
base 12, two 12 hour periods divided into 60 minutes, or 5 times 12, and 60 seconds,
again 5 x 12. There’s also the Jiffy, a 60th of a second,
but we usually switch back to base 10 for that and use hundredths or thousandth or billionths
of a second. There’s really no natural system that smoothly
lets you use the same unit for days and years, though, and in an era of computers it’s
not such a big deal, as they can rapidly convert times and dates for folks between time systems. Earth’s got billion of people on it who
will never have a motive to change calendars and by the time you’d have billions of folks
living off Earth, they’d be all over the place on different and awkward local times
anyway. Indeed the place most folks are likely to
live off Earth early on is in Earth Orbit, where the ‘day’ is a couple hours in low
orbit and in the higher orbits it is longer but the Sun is almost always shining with
noon-time brightness, since you spend little time in Earth’s shadow in high orbits. So possibly excepting Mars, nobody really
has a motive to use local timekeeping for regulating human interactions. You’d still have them, folks on Mercury
obviously will care when the Sun is rising or setting and doubtless develop local terms
for it, in their case something more akin to our month, as it takes about 2 months for
a day to pass on Mercury and they have no moon for a local month either. Once you get out far from the Sun though,
it gets less important what the Sun is doing since you really don’t see it, you might
have observation domes to go out and see the stars and look at distant Sol but you’re
doing your living indoors, even if it’s some massive habitat with whole forests and
parks inside it being artificially lit. Now while I’d imagine we’d send out interstellar
colony efforts within a generation or two of when it becomes practical to try it, in
terms of success odds and costs, you’re not likely to see big push for that until
most of our solar system has been utilized, including all the millions of minor planets
inside it. A handful of test colonies around other suns,
delayed in growth by centuries of travel time and without easy access to the industrial
might of our home system to expedite growth, are unlikely to be the ones setting standards
on timekeeping, and the issue is likely to be addressed before they are a major factor
in deciding. So too, while some colony on a world under
an alien sun might adopt some 26 hour day and 362 day year it had locally, we shouldn’t
assume that system would develop using that, because they’re not likely to start colonizing
that system with that planet. As we discussed in the Life in a Space Colony
Series, a colony ship arriving in a new system with an Earth-like planet, for a given value
of Earth-like, does not just go land there. You do your colonizing backwards, starting
in space and building up your industrial might and colonial support before going down and
terraforming some planet, a process of centuries at a minimum, and they will have spent decades
if not centuries traveling inside a spaceship that is much the same as any habitat or space
station they’d build there. Indeed even once that planet is terraformed,
they will likely have had their off planet population grow so much during that time that
they never had most of their population on that planet, so why use it’s natural calendar? Even if they left Earth planning to focus
on terraforming the destination planet, those folks will have lived in an artificial habitat
for generations and the eventual colonists might not find a planet all that attractive,
compared to just building O’Neill Cylinders or similar, a far faster and easier process
anyway. Such being the case, why change time keeping
methods? Now if they wanted to, they might slowly change
the ship from emulating Earth to Planet X while en route, they are likely to know a
lot about the destination, especially how long that planet orbits and rotates and what
its gravity is, so if they’re going to a planet with 90% of Earth’s gravity that
rotates every 26.7 hours while orbiting a dimmer orange dwarf star every 165 of those
26.7 hours days then they might gradually shift the ship’s internal environment to
match those, especially since it will help things besides humans adapt, like all the
flora and fauna you plan to transplant there. Which is also another reason to keep your
various habitats to Earth-normal times, our ecology is adapted to it and it’s probably
easier to mimic it than alter things to different setups. Still, all these various interstellar colonies
might alter to a local time setup simply to acknowledge that it might happen eventually
and they really are going to be rather isolated there anyway. They might all keep using the Earth Year for
official dating for communicating to other systems but they could also just as easily
do that in something metric like mega-seconds, about 12 days, or gigaseconds, about 30 years,
and just have some official Day 0, or Second 0 everyone used. If you’re curious, we’d be in the 64th
gigasecond of the AD calendar, megasecond 746 when the video came out. Of course the problem is that if they start
their clock before they leave Earth, when they arrive it’s going to be running slow. Which take us into the other big problem with
interstellar civilizations and time, which is relativity and how long such trips take
even when moving at relativistic speeds. The closer you get to light speed the more
time slows down, though in truth we’re not likely to ever have ships where it slows down
to such a significant factor that folks living on them feel like they were fast forwarding
through time. The same applies to general relativity, the
slowing of time from being in gravity wells or on an accelerating ship. Time runs a bit slower at your feet than at
your head, and a good bit faster on Mars, which has weaker gravity and is also further
from the Sun’s gravity. Time runs fastest in the intergalactic void,
particular the Cosmic Voids, the big empty spaces relatively devoid of galaxies, and
slowest near the center of galaxies, or of course, near black holes, which are at the
center of most big galaxies too. This difference is minimal though, even in
extreme cases, but starts mattering when dealing with really long time scales. But it is calculable so it just means folks
have to adjust their clocks or timestamps on interstellar correspondence. Thing is, what date do you actually use? A ship leaving Earth in the year 2020 and
arriving at a destination in our year 2200, having traveled at 20% of light speed, looking
at their own clock, might see that arrival as being in the year 2196, having experienced
about a 2% slow down in time during the voyage. They will also have traveled 36 light years,
meaning the signals they’re getting from Earth when they arrive don’t say 2200 AD
anyway, they say 2164. One might argue, especially if everyone wants
to keep to some standard time-keeping system based off humanity’s homeworld, that maybe
they should say that it is now the year 2164 on their arrival, rather than 2200. Of course to everyone who was awake for that
trip, quite possibly all the way from Earth if life extension technology has improved,
has still only experience 176.4 years of travel, not 180. Needless to say this only gets exacerbated
by longer flight times and higher speeds, but it also gets worse if we start contemplating
subjective time experienced. If you’re born in the year 2000, and got
on that ship, you’d be 196 when you arrived, so how old do you say you are and when do
you celebrate your birthday if you do decide your clock is the one that matters? Time was running 2% slower on your ship, so
if you were born on January 1st 2000, your 21st birthday, in personal time which is what
you age at and experience, was not on January 21st of 2021, it was on January 7th, but if
you checked the clock back on Earth, based on signals to your ship, it’s going to say
it’s January 1st on March 14th, because you’re 73 light days out from Earth somewhere
in our Oort Cloud, though your own clock on the ship would say it was March 5th, since
you’ve lost about 9 days to Einstein at that point. This is all assuming your ship instantly accelerated
too, which it won’t have, but it makes the already confusing math a bit easier. And of course that’s when you’re getting
all your mail from home, and it’s rather unlikely you’ve stopped corresponding with
friends and family entirely, or watching the news entirely. You’re still waiting for your favorite book
or show or film to come out, and you have to go by Earth date’s for all that. So you basically have 4 clocks you watch,
the atomic clock marking how much time has actually passed on that ship, the radio clock
from home telling you what the date was when that signal left Earth, the computer one telling
you what the calculated time on Earth is right now, which is a rather debatable concept,
and the one telling you what the date would be back on Earth when a message you sent right
now actually arrived, if you plan on sending a happy birthday message or gift you bought
online to friends or family back home that you wanted to arrive on time. Now if you plan to stay on that ship after
it colonizes that planet and starts running trips back and forth to Earth, you’ve got
to add in some more clocks telling you what the date on that colony planet is. Folks running some circuit of destinations
on interstellar trade routes might go rather nuts trying to track such things, if we didn’t
have computers they could set reminders on and rely on the computers to inform them. You also definitely need to track shipboard
time too since you’re likely to have all sorts of parts and software that have time-sensitive
maintenance and replacement requirements. Plus you’ll want an onboard atomic clock
to compare to clock signals from various systems to calculate your position and trajectory
with high precision, same as we do with GPS location systems. Speaking of computers, there’s more than
one way subjective time can get messed up besides Einstein. Needless to say, you might lose a lot of personal
time by opting for some sort of deep freeze or suspension technology, and that would shut
off your biological aging presumably or slow it, see Sleeper Ships for details. You might do this even if you have effective
immortality from radical life extension technology simply because you don’t particularly feel
like experiencing your decades long journeys. Now in discussing life extension I generally
dismiss the idea of being bored, I’d need a few lifetimes just to get through all the
books on my pending reading list, during which I imagine that list would expand faster than
I could read it, but at the same time there’s probably a realistic limit on how much life
you can experience in a mostly human form before you fill up your brain, and even with
memory enhancing or compression alterations to that brain, I’d tend to doubt anyone
who had actually experienced tens of thousands let alone millions of years of time would
really qualify as human anymore, simply by the weight of all that time and experience. I would doubt you could maintain sanity all
that time, at least in the sense of human-normal behavior. But that brings up mental augmentation and
realistically we’ll probably have a lot of that available long before interstellar
travel is more than a novelty a very rare few have experienced, indeed likely before
anyone has. There’s a lot more options to mind augmentation
than simply raising your IQ, but when we’re talking about super-intelligence we generally
classify it in 3 major types. One is Quality superintelligence, which is
a bit abstract but essentially why one human is smarter than 10 chimpanzees, even though
they’ve got more total brains. Another is networked intelligence, which would
basically be making those chimps smarter by wiring their brains together, though more
likely by creating a new distinct 10-chimp single mind, hive minds being one example
of networked superintelligence. The third though is Speed Superintelligence,
where you haven’t actually made someone smarter, just sped up the rate they think
at. You might do that by replacing their synapses
or neurons with transmitters that were identical except for transmitting at light speed, rather
than at roughly the speed of sound or slower as ours do currently. If you made such a switch, you’d be experiencing
time around a million times faster, in terms of your thinking, as you currently do. Now one might argue someone who sleeps 8 hours
a day and is awake for 16 is experiencing less life everyday than someone who sleeps
for 7 and is awake for 17, they are awake one hour or 6.25% longer each day and experience
23 more days every year. Whereas someone who sleeps 9 hours a day and
is awake 15 experiences 93.75% as much time, and if we’re only counting conscious time
that would match someone traveling at a third of light speed, in terms of time dilation. That’s obviously a pretty debatable point
as sleep is not the same as shutting someone’s brain off and since its part of what keeps
you healthy, you’re not likely to get a longer lifespan, even subjectively, by cutting
down on your sleep. Of course we might be able to rewire people
so that they did not need sleep to be healthy and mentally agile, and it would get hard
to argue that someone who was conscious and not groggy 24 hours a day, 365 days a year,
had not experienced 50% more life than folks spending a third of their time asleep, 548
subjective days per year. More so if they’re on some spaceship far
from Earth’s clocks and calendars - or love coffee, the original life extension technology. But with all that mental augmentation in play,
they might be able to slow or speed up their personal time quite a lot. Indeed they might slightly speed their consciousness
to exactly counter-match whatever the relativistic time dilation on their ship was. Time running 10% slower from moving at 42%
of light speed? Boost your subjective time up by 10%. Normally we think of slowing subjective time
on spaceships so you don’t experience it, but you might go the other way too. Indeed you might do this on planets with shorter
days, just make up that missing hour in a 23 hour day by accelerating everyone’s thinking
speed by a few percent. Now on the civilization side of things, all
this weird time raises issues. Let’s consider something mundane like paying
people’s salaries or calculating what grade a kid is in or what your wedding anniversary
is or when your interstellar mining corporation celebrates its 1000th anniversary with a big
marketing campaign and discount. With all the complexities we saw for space
traveler’s it’s easy to imagine folks who traveled a lot between stars would just
shrug and say “I’m pretty old” but it’s a whole different story if they’re contemplating
their paycheck, how many years they’ve got on their pension, what sort of compound interest
they’re getting on investments, and how much taxes they should be paying. We wouldn’t tax someone more or less income
tax because they were asleep, more or less, but what about someone in hibernation for
a trip? Or not for a trip, just on Earth. And before you say no, let me point out the
obvious tax dodge of owning stock in a company for a decade while spending 9 of it on ice,
paying only a year’s worth of taxes, incurring no expenses besides your freezer bill, and
emerging with a decade of earnings. Or alternatively, going on a five-century
voyage on ice for all but a year of it, getting home and being offered a year’s salary,
and paid in 500-year old values, with nothing for inflation or adjustment for any standard
of living increase during that time. You might say you deserve all 500 years of
that pay, or maybe the 400 that passed on that ship as it flew around at relativistic
speeds, but also keep in mind that someone else might be accelerating their subjective
time and demanding ten thousand years of pay as they experienced 10,000 years of consciousness. And it might be a fair demand too, if they
had to do it to perform their duties. Now we could handwave that off as not relevant
in some future utopia of immense prosperity, but there’s bound to be parallel examples,
we’re just using modern concepts, and mostly to highlight that there’s not any clear
and obvious approach. So different places might use different standards. You get on board some ship to serve as a crewmember
on a thousand year voyage to a different pocket of space and that ship’s captain says he
pays on ship-time, annual salary, but at your destination they expect you to pay income
taxes on the voyage if you plan to trade there, for all the local time you spent inside their
territory, while your home system is still taxing your assets using their own method,
and the interstellar trading guild you’re with expects you to pay them their dues based
on your ship’s clock but let’s you treat time in hibernation at a discount, say one
tenth of the ice-time counts, whereas your last guild charged none for hibernation but
expected you to have a tamper-proof chip in your head that measured your subjective time,
if you boost your thinking up to 10x normal speed, they charged you 10 times as much. Makes one wonder what overtime at work might
mean in such situations too. Now FTL makes this even more confusing, since
it opens the door on causality violating events, but in the long term all these time tracking
issues get worse. How historians would track the timelines on
some ten-thousand year long war operating over a thousand light years and a million
worlds is going to be beyond confusing, especially as battles might be continuing centuries after
a cease fire. Very stable and long-lived societies might
be able to form non-FTL empires stretching light centuries, just because they don’t
really need to write home for directions much as their society isn’t changing on a generational
basis and differently on each planet. But they also might have figured out some
perfect and stable society, there may actually be such a thing in some objective and mathematically
provable sense and regardless they might feel like they have it or close approximation. They may also get around light lag coordination
issues by having set protocols for how everyone acts in a given scenario, like emergency fleets
scramble to a preset coordinate to rendezvous with other fleets from other systems if a
given event occurs. Those might get rather complicated since the
ideal rendezvous point for given fleet elements would be time-sensitive and dependent on where
an enemy or disaster occurred, which they would all observe at different times and have
different travel times to react too. Trying to have a senate or parliament on an
interstellar scale might be beyond tricky too, considering a representative elected
and sent to the capitol might take several centuries to arrive, presumably begin their
term of say a decade, while getting orders from back home from political parties now
in control who didn’t even exist when they left, and arrive back centuries later to be
lynched. Time lag being what it is, you could easily
have all sorts of legal necessities too such as trials in absentia or hearings to decide
what to do with someone’s property who was originally only going to be gone a couple
decades for a quick jaunt to their nearest neighbor system but due to some unforeseen
event or change of heart got detoured and now you have to figure out what to do with
their property and its back taxes, with each system having different rules and those changing
every century or so. Some folks have suggested you might just have
civilizations freeze themselves most of the time to allow a net experience of time that
was slowed down, thus allowing a potentially larger civilization, but I don’t see that
working outside a special case we’ll get to in a moment. Another notion is that your interstellar civilization
might really just be the trade ships and their proxies or representatives in various systems,
as they’re the only ones who really need to care about what’s going on between star
systems much and would experience that slowed down time anyway and thus might be a stabilizing
or conservative factor, something along these lines is discussed in Alastair Reynolds’
novel “House of Suns” one of my favorite novels and one that deals with light-speed
limited civilizations trying to deal with millions of years of time passing, or the
people who travel between those civilizations and never visiting the same one twice since
they’re always gone by the time they return there on their galaxy-spanning voyages. Amusingly in the truly long term some of these
problems go away, presumably in part because they’ve just had a ton of time to figure
out what works best, but as we discussed in civilizations at the end of time, post-stellar
civilizations might camp around black holes, where time runs slower, and take advantage
of ultra-cold computing to run hyper-efficient but slow computation or thinking. For such civilizations the light lag issue
isn’t such a big deal because time is subjectively running at a miniscule fraction of the rate
it used to while every galaxy has either merged together or flown over the cosmological event
horizon. If you’re running at a billionth your normal
thinking speed, and so is everyone else, a hundred thousand light years, and a hundred
thousand years of message delay, only feels like an hour. And while life moves at a snail’s pace,
it’s still way longer subjectively too, those civilizations we discussed as existing
in post-stellar time could potentially exist for billions of billions of billions of billions
of years, so even at that’s snail’s pace of subjective time they still experience timelines
that make the current age of the Universe seem like an eyeblink. Of course time and entropy still take their
toll eventually, even if you can make such ultra-cold and slow civilizations work, and
you might start thinking about wanting to move to new Universes if they exist, or if
you’ve figured out time travel, go colonize or invade your own past, and we’ll look
at how a time travel capable civilization would work next week, if time travel was possible,
and if any sort of coherent civilization might be able to exist if it did. As we wrap up the Holiday season, let me give
you a hand knocking something off your holiday to-do lists. Gifts! If you’re watching this show, you probably
tend to feel like I do that knowledge is one of the best gifts you can give someone. If you know someone who likes to solve puzzles
or find out how things work, I’ve got a Brilliant gift suggestion for you… Brilliant. Brilliant is an online learning community
with over 60 interactive courses and many quizzes and puzzles, plus Daily Challenges
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their online community gives you places to discuss the material or ask questions, and
their mobile apps offline feature lets you take courses even when you’re not getting
a good signal while traveling for the holiday season. This year get the gift of knowledge for your
loved ones by gifting them Brilliant, it’s such a fun way to nurture curiosity, build
confidence, and develop problem solving skills crucial to school, job interviews, or their
career. Go to Brilliant.org/IsaacArthur and grab a
gift subscription to help your loved ones finish their day a little smarter. So while we do have a livestream Q&A this
Sunday, today wraps up our episodes for the year, and I wanted to thank everyone for joining
me for yet another year of Science & Futurism. If you’d like to help support more episodes,
I’d be very glad to have your support on patreon, or through any of our other donations
methods you can find on our website, IsaacArthur.net And of course we do have more episodes coming,
starting 2020 off on January 2nd with a look at Time Travel, then the week after that we’ll
explore Alien Conspiracies, and the sorts of aliens that might be conspiring and why,
in Conspiratorial Aliens. Until then, thanks for watching,
and we’ll see you next year!
