Where Does Complexity Come From? (Big Picture Ep. 3/5)


The universe as a whole evolves towards increasing
entropy, or disorder — a tendency physicists call the Second Law of Thermodynamics. This movement toward disorganization might
lead you to think that organized structures – like, say, living beings – would never
spontaneously come into existence. Of course entropy can go down in part of the
universe — you can trade a decrease in entropy in one place (like cooling water so it crystallizes
into ice) for an equal or larger increase in entropy somewhere else (like heating the
back of your fridge). Order increases here, but only at the cost
of decreasing order there. But we can still ask: why do intricate, complex
structures come into being in the universe, if the overall tendency is toward increasing
disorder? The secret is that order and complexity are
very different ideas. Entropy measures how many different ways you
can make an arrangement of small-scale particles that have the same large-scale properties:
like, 37 degrees celsius, brown hair, good at soccer, and so on. [There are lots of different ways!]. Complexity, on the other hand, is a measure
of how hard it is to describe a set of large-scale properties. Simple systems are easy to describe; complex
systems require a lot more information. For example, take a cup filled with half coffee
and half milk. It starts off in a state with relatively low
entropy – you could swap coffee molecules with each other, or milk molecules with each
other, without changing things substantially. But if you swapped coffee molecules with milk
molecules that would be a noticeable change. It’s also a simple setup — milk on top,
coffee on the bottom. Now, as the milk and coffee begin to mix,
entropy goes up – where they are mixed together, swapping some coffee molecules for milk molecules
no longer makes much of a difference. But the system also becomes more complex – to
describe what you see, you would have to specify exactly how all of those tendrils of milk
and coffee intricately swirl into each other. Continuing on, entropy keeps going up, until
the milk and coffee are completely mixed together and swapping any molecules of coffee and milk
with any others doesn’t really make any difference at all. That’s equilibrium, where there are a huge
number of arrangements of the molecules that look essentially the same. But this highly-mixed equilibrium is once
again simple: it’s just a homogenous mixture of coffee and milk; no more complicated fractal
swirly stuff. This general principle is borne out time and
time again: while entropy increases, complexity initially grows, then decays. Complexity can be a natural step along the
path to increasing entropy. The best example is the universe itself. The early universe was very smooth and very
dense: that’s low-entropy, and also extremely simple. The far future will be smooth again, but very
dilute: that’s high-entropy, and again extremely simple. It’s now, in the medium-entropy middle,
that things look complex. Stars and galaxies and veins of minerals in
rock and swirling clouds and amino acids and proteins and human beings and cats – we’re
at the exciting, beautiful stage of the coffee mixing! But just as with the coffee and milk, in the
far distant future complexity will decrease again, and complicated stuff like us will
at last be simplified out of existence. Hey, Henry here, thanks for watching. This is the third video in a series about
time and entropy made in collaboration with physicist Sean Carroll. The series is supported with funding from
Google’s Making and Science initiative, which seeks to encourage more young people
(and people of all ages) to learn about and fall in love with science and the world around
them, and the videos are based off of Sean’s book “The Big Picture: On the Origins of
Life, Meaning, and the Universe Itself,” which you can find online or in bookstores
around the world.

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100 thoughts on “Where Does Complexity Come From? (Big Picture Ep. 3/5)”

  1. theMikeyDogg says:

    well shit

  2. Stephen says:

    "Simplified out of existence." What a phrase!

  3. ganondorfchampin says:

    Finally a video in this series which doesn't abuse the meaning of entropy.

  4. Volbla says:

    There is one thing i don't understand. How did you put the milk and coffee in the glass without mixing them?

  5. jumanous says:

    lol.. comparing the infinite systematized complexity of the micro machines that make up life, to naturally occurring swirls in a coffee mug. Amazing how "science" deals with the obvious problem of living organisms from non living chemicals simply sweeping it under the rug, and pretending the solution is easy and hoping the plebs can't tell the difference. We don't want to get ridiculed by Neil Degrassi Tyson or Richard Dawkins after all… Sad.

  6. Brooks Silber says:

    A good way to remember amino acids… I mean no acids? Maybe you could make a joke about that. In fact I challenge thee to make a joke using said portion of joke!

  7. Jonasz314 says:

    This is why most people don't venture into cosmology. It's just too damn depressing. It seems like the answer is "why bother?"

  8. Req says:

    Great video! Even some smart people gets these terms mixed up, this is very good way of explaining it.

  9. camfunme says:

    In your "coffeemilk" coffee-milk example, how does entropy explain the reverse process, separation over time into density gradients?

  10. AmoebaMan says:

    Another comment: your example of decreasing local entropy at 0:19 seems to have a big hole in it. Yes, but doing so involves a deliberate investment of work/energy (not to mention a highly complex and deliberately engineered thermodynamic mechanism). This sort of entropy exchange could never happen in nature, right?

  11. Adam Edwards says:

    Wow! I feel so lucky to be alive. If entropy is increasing then complexity is rare in the grand scheme of things. There is so much complexity to celebrate in this relatively short amount of time that we have it. Thanks for the video.

  12. ericjane747 says:

    Providing more useful energy does not enter our alleged closed system. And it all might be an illusion since entropy relies on the arrow of time.

  13. Ralph Dratman says:

    But the coffee and milk mixing process, even when viewed during the interesting middle of the process, does create any entities that reproduce themselves or self-perpetuate in an ongoing process with stable or increasing complexity. Part of the reason that does not occur is that the coffee/milk mixing process as discussed here is just a single batch, while living ecosystems on Earth depend on a continuous (on a global scale) influx of light energy.

    To my knowledge, the best we can say about an entropy-increasing region is that, once a continuous pipeline process is established and becomes (globally) steady-state, self-reproducing processes might come into existence. Those that do appear will by their very nature persist as patterns that repeat indefinitely.

  14. Mr Toaster says:

    If all I had to work with was science as this video does ,this stuff would all be true, however since I know a thinking being{God} put me here on this earth and created all things around me including the earth I am on. I know the people on this video are wrong! If God does not exist we are products of chance. If God does exist then we are products of INTENTION and everything we see are products of an intentional creator. If as I believe that one does{A creator exist} then everything that they have told you in this video is 100% wrong! think about it!

  15. Mr Toaster says:

    I do not see that we are products of chance but we are products of an intentional creator!

  16. lightsidemaster says:

    Fuck entropy, we can't allow this shit to cause the death of life and our universe…

  17. Ramon Patalinghug says:

    stop preaching doom and gloom. There is hope in Jesus Christ the Lord of all.

  18. D FizziL says:

    complexity = life? and imo the coffee stirring analogy is flawed in that the spoon (controlled by outside means) is adding energy to the system , the complexity or entropy required something to start it,

  19. Tom Brown says:

    I think there should be an entropy emoji.

  20. afrinbar says:

    actually complexity starts higher than it ends for example when the coffee and milk you have to explain that there is milk on the top and coffee on the bottom and in the end its just milkcoffee everywhere

  21. Stepping On Legos says:

    I can imagine a story of an immortal person who lived a quiet life from the beginning of the universe and slowly as complexity decreases become reduced to a blob.

  22. AdeAde says:

    to all the people that didn't understood this : Ya'll gonna die

  23. stanley neoh says:

    Random thought:
    Is Complexity like the derivative of the entropy – time graph?

  24. Clark Sarge says:

    Great video, but it doesn't answer the question in the title. Maybe a better title would be, "how does complexity change with time in large scale systems"? Not as catchy though.

  25. Rockagold says:

    Isn't it a little presumptuous to assume that we are right in the middle of entropy where everything is most complex? I mean it's a beautiful idea that we are unique, in the most exciting phase of the universe, but on what basis can we assert this? We know little about the complexities of life on other planets or systems.

    Perhaps we are still in an early simple stage where there is much more complexity to come, or perhaps we're in the opposite where we've missed all of the interesting aspects of the universe and life.

  26. Kitsune says:

    but then if our main purpose is just help increase the state of disorder in the universe, then why make the universe exist in a simple "inequilibrial" state? why not make the universe instantly exist into an "equilibrial state? why must the universe make multiple small and complex objects, rather than just one supercomplex object? and if "equilibrial" state is achieved, what now? what happens after? what if equilibrium is just a concept we percieve to explain the unexplainable….

  27. D4v3 the demon says:


  28. Vishal Jangid says:

    why entropy graph is not straight line

  29. Geraldo Sanchez says:

    did he erase the motivational video to vote for hillary clinton? or it was in another physics channel?

  30. UglyNerfHerder says:

    that was mildly terrifying

  31. joseph jackson says:

    what happens to the coffee-milk after it settles? Doesn't it just separate into coffee and milk after enough time?

  32. T.VIGNESH NAYAK says:

    If early universe is simple(low entropy) then why it is so complex to explain?(2:29)

  33. Blaya 58 says:

    how do u know we arent at low etrpy, think it might get even more complicated

  34. tanuj nainiwal nn says:

    so u mean universe is expanding because of increasing entropy

  35. Michael Alfera says:

    Who knew that Minutephysics could give you all the feels? Great job, guys.

  36. Benjamin Márkus says:

    wow, this was new! love sean carroll

  37. Max Bui says:

    Really deep

  38. Vega_Omega says:

    But what about when gravity acts on the coffee milk over time to cause them to seperate due to variations in density? how is that not decreasing entropy?

  39. Scott B says:

    I have a question. Can you increase the amount of complexity in the universe by blowing things up?

  40. Introverted Person says:

    life = complexity


    ola incrver no meu canal vem ca

  42. carrvo says:

    In other words Complexity is the result of the transition from low Entropy to high Entropy?

  43. Luis Carlos Rico says:


  44. Saeed Baig says:

    My mother always said life was like a cup of coffee.
    You never know when you're going to be drunk out of existence.

  45. Perry says:

    Its crazy to think that life doesn't have to exist. That there could literally be nothing. Its incomprehensible

  46. Ali Khan says:

    I am really loving this short series on "The Big Picture".

  47. Shane Mendez says:

    Way better explanation of entropy than moriarty

  48. Dirt Noodle says:

    this one made me feel existential

  49. Sam Ezeh says:

    1:15 I think I may have seen that cup of coffee a few times before…

  50. Walker Cline says:

    I'm no scientist, but why can the second law of thermodynamics be applied to the universe? As mentioned many times before, many perceptions we have (Like cause and effect) are quite different or don't have any pull at the microscopic level. If that isn't proof that rules and theories don't carry through between scientific environments, then I don't know what is. Relating to another comment, another situation where entropy decreases, such as oil and water, can just as easily be imagined.

  51. joseph jackson says:

    So what happens when the coffee settles and the milk and coffee separate again?

  52. Kacee says:

    It would be even better if it was just coffee, without milk.

  53. J says:

    so we're accidentally made while breaking things down

  54. Tony says:

    that is not even a coffe, that's just not entirely white milk…

  55. John Love says:

    Interesting insight by Carroll. However, he still does not explain how complexity arises. The 3:34 min video is severely deficient and misrepresentative.

  56. Ben Bostic says:

    You hear that? More basic bitches on the rise

  57. corbiac says:

    If Universe is a coffee with milk then who is the spoon

  58. David Bunner says:

    Elegant and Depressing

  59. brightfuture09 says:

    Now I understand why crunchy peanut butter is better than smooth.

  60. Mickelodian Surname says:

    Get used to this idea folks its the primary process in machine learning. Not that anyone doesn't understand a simple thing like heat always flows spontaneously from hotter to colder bodies, and never the reverse, unless obviously external work is performed on the system.

    {displaystyle dS={frac {delta Q}{T}}}

  61. Chouci Vang says:

    The Simple-Complex-Simple chart, for me, has applied for everything in my life. Mind-blowing concept.

  62. Abdul Mohammad says:

    i don't understand it properly. am i dumb?

  63. Aryan says:

    A very beautiful explanation.

  64. Aiden Strasser says:

    How… did they get milk on top of coffee…?

  65. thewiseturtle says:

    Um… Living things are higher entropy things, NOT lower. Humans are more messy/complex/unpredictable/chaotic than inanimate stuff. Also, equilibrium only last for a brief moment! As soon as you stop stirring the milk and coffee, it starts separating again. Usually in a new way.

  66. Archronis says:

    This video makes me want jelly beans.

  67. Craig Blanton says:

    Great. Now it's 8 pm and I want a coffee

  68. Ryan Chung says:

    Cats and human. Why cat?

  69. manifold says:

    look at stupid religious people down voting this video because it makes them feel bad. They're going to need an extra dose of church this week to wash out this truth bomb and re-enter the world of delusions and make belief.

  70. osmmanipadmehum says:

    If cold water would increase order then heat death would increase it.

  71. Agustin Castro says:

    then even if we live forever we will just be too simple to exist, brain explodes

  72. Bohan Xu says:

    I'm a physics and math undergrad…I really want such videos to make clear how entropy of a closed system can decrease. It's just extremely "improbable". If you take an system ergodic with respect to a certain set in phase space, and wait long enough, the system will travel in the set and eventually become back (arbitrarily close)….Formally, long time average of entropy (t to inf) will stay at maximum, because it stay at maximum value most of the times (overwhelmingly)…however, it can fluctuate and decrease at sometime…..I really hope pop science video can make it clearer saying "entropy will increase with overwhelming propability"

  73. Jonathan Frakes says:

    If Entropy increasing in one place causes a decrease in another place anywhere in the universe, on a big scale: if humans were to all increase entropy by mixing 2 cups of coffee each so app. 14 Billion coffees…. would we cause the universe to decrease somewhere else and essentially cause an event by that? and if yes, is this decrease/increase here/there a scientific rule or could one argue that destiny led humanity so someday think about this, try it out and so on at the exact same moment somewhere else the other happend? now getting philosophical: is there even something as free will if this would be true?

  74. NGC 7635 says:

    I know some 37 degrees Celsius girls, and I know some 39 degrees Celsius girls. Those are the girls that will melt your socks off

  75. geistreiches says:

    wow this was cool

  76. Sage Savage says:

    What is entropy?

  77. AshnSilvercorp says:

    This still doesn't say how it happened… it's all assumptions based on guessed mathematical models…

  78. Aponia & Ataraxia says:

    I would like to offer an alternative analogy to 'coffee & milk' …The Cosmos is like a slab of meat, that when left out in the desert, develops microorganisms over time (as it rots), before withering to dust. The Cosmos isn't simply winding down from the big bang… it's rotting, and Homo sapiens are the microorganisms

  79. DragoFlamez YT says:

    0:03 are those bean boozled beans?

  80. Premananda Laishram says:

    I like the way how he say simplified out of existence so happily ….

  81. Gábor Králik says:

    milk + coffee = milfee

  82. 30G says:

    Plot twist: complexity could cause simplicity, since a circle could be called a curved line, you could also say a circle has infinite sides.

  83. Marco Villalobos says:

    Why does the early universe have low entropy? I thought it was really homogeneous

  84. Franga Vita says:

    Fluid theory (Reproduction/Alimentation/Rationality)

  85. Creative Nothing says:

    I love the happy little strum in the music right after he says "Simplified out of existence"

  86. Trey Lehman says:

    “And we will be simplified out of existence”
    “Wow this is hitting me really hard.” ponders deeply while I question everythi-

  87. Shreeya Mittal says:

    Until 2:45, I thought this was going to be their one video where they actually manage not to mention cats at all.


  88. Trevor Mozingo says:

    I'm not sure I follow the complexity argument — if complexity is defined as 'amount of information required to describe something', complexity would continue to rise with disorder I don't think it would ever drop. You can think of password complexity for example. A really long password with randomized characters cannot be compressed (described) in a simple way (this goes along with your coffee mixing analogy). But the longer and more random the password (the more you mix / disorder the coffee), the amount of information required to describe the exact state of all molecules in the coffee continues to go up. I don't see why the complexity would go down.

  89. Ornithocowian King says:

    So basically, the entire universe is one huge algebra problem.
    Starts simple, gets complex, everything's simplified out of existence.

  90. cosmilite says:

    If there are multiple universes like m-theory states, couldn't we just suck excess energy out of another universe and dump our entropy in to it like the refrigerator example? Furthermore, if other universes can interact with ours, then it should be possible for them to have an unpredictable effect on our entropy at some point right? I mean is there proof that our physical universe is a completely closed and bound system?

  91. Hus 9 says:

    Nebulas are the engines of Complexity and Black holes are the engines of Entropy…

  92. Vaul, Dog Warrior says:

    Ermergerd! This life is all I all have. I need to make the most of then. No more excuses. No more victimhood mentality.

  93. Dyuti Mangal says:

    Thanks for triggering my existential crisis :')

  94. Free MGTOW says:

    This explained nothing. And the Explanation of Entropy is missing the Information Exchange and the Impact of consciousness that we know from the Quantum mechanics. This Video is typical materialistic pseudo science that wants to see the world like 100 years ago. Pathetic…

  95. Wu Li says:

    The mathematics of Relativity have turned out to be identical to those for thermodynamics, while Relativity contains the glaring Simultaneity Paradox, indicating entropy only has demonstrable meaning in specific contexts. You can call quanta entropic all you want, and nobody can ever prove you wrong, implying they are syntropic.

  96. Soviet Plays Games says:

    So if you built solar panels which only stored energy in batteries, would that decrease entropy?

  97. konroh2 says:

    So the 2nd law of themodynamics does point to the need for an intelligent designer. Good to know.

  98. Champignon Van de Graaff says:

    It’s good to know that we will one day be simplified out of existence

  99. musaire says:

    This is not correct! It assumes the big bang and the universe expansion – those are scientists' imaginations when Einstein's formulas can't calculate everything (because we have not measured everything in space yet – there is lots of plasma and electricity in space – making premature assumptions is childish).

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