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I love how this word “emergent” has become popular by people that want to pretend they have an answer but it’s really just the “…” thing. There is no such thing

I love how this word “emergent” has become popular by people that want to pretend they have an answer but it’s really just the “…” thing. There is no such thing as “emergent”. The motion of an automobile isn’t an “emergent” thing you can claim because you don’t know how engines and transmissions work. Everything we can’t explain recently has people, who I assume don’t know how to say I don’t know, proclaiming “it’s emergent”. As if that’s an answer to anything. Much less a claim to knowledge. Might as well claim “god made it happen”.

lanstin 4y ago
System availability is an emergent property - I can build five nines of availability out of components with just two nines. Retries, algorithmic handling of failure, and the like.
Dylan16807 4y ago
> The motion of an automobile isn’t an “emergent” thing you can claim because you don’t know how engines and transmissions work. That's the opposite of what emergent means, isn't it? Because of force on the transmission, you can say that the motion of the vehicle is emergent rather than needing its own framework or explanation.
CaptainNegative 4y ago
Seems like pretending to know what the word emergent means in physics is an emergent phenomenon on HN. It's not wishy washy, it has a precise meaning that can be both derived and, typically, refuted.
nextaccountic 4y ago
Emergent just means that it's not the basic building block; it's made up of other, more fundamental things. So for example thermodynamics is emergent (even though it is fully studied and relatively well understood) because it arises from interactions of particles. If you say that spacetime is emergent that is a big deal: it means that, while it can be studied on its own, it's actually composed of other, more fundamental things. But you still need to show that a) this other fundamental thing actually exists, and b) we can show mathematically how the spacetime works, in terms of those other fundamental thing (just like you can show how thermodynamics works in terms of statistical mechanics) And that's where your "because you don't know how it works" thing breaks apart: one can't claim to have solved this problem without tacking b).
- nemo44x 4y ago
  > it's made up of other, more fundamental things Then explain those things and prove they exist. Otherwise this just sounds like bullshit. There’s a difference between observing thermodynamics (and not trying to answer why but rather how we observe it - big difference!) and writing equations we can measure and just saying “it’s emergent” to “…” things we are unable to answer “I don’t know to”.
  - doctor_eval 4y ago
    That seems to be exactly what they are trying to do: > Lee Smolin is working on an idea where the building blocks are events where momentum is exchanged.Space, and hence position, is an emergent phenomena. It’s perfectly OK to speculate that perhaps gravity, say, is not fundamental, but instead emerges from interactions or whatever at a lower layer that we haven’t yet identified. What word would you use?
  - Maursault 4y ago
    > Otherwise this just sounds like bullshit? Yet it is very compelling bullshit that stands up to intense scientific scrutiny.[1] [1] https://einstein.stanford.edu/content/relativity/a11332.html https://einstein.stanford.edu/content/relativity/a11332.html
midlightdenight 4y ago
There’s probably some places where it’s used where it shouldn’t be, but there is such a thing as “emergent”. I think it helps to see an easy example first. Take a great body of water (h2o) on earth, such as the ocean. That water has waves and those waves have amplitudes, as well as other properties such as crests. A molecule (or even a few) of water (h2o) doesn’t really have these properties. It doesn’t have crests. You could argue it has amplitudes. Crests are an emergent property of large masses of water molecules within a specific system. There’s no crest to a water molecule. Similarly, for demonstration purposes we could say there’s no waves/crests when gravity is removed. So when I hear emergent, I imagine properties that show up under certain conditions within a system, that were not present in individual components.
- nemo44x 4y ago
  There’s a whole lot of “…” between a water molecule and a wave. There is nothing emergent about it. “Emergent” is a bullshit answer.
  - jcparkyn 4y ago
    You seem to have a different definition of "emergent" to the rest of the world. Just because there _is_ an explanation for waves doesn't stop them from being an emergent behaviour.
magicalhippo 4y ago
In this case there's something more concrete, in the form of equations[1], behind the usage of the word. [1]: https://arxiv.org/abs/1307.6167 https://arxiv.org/abs/1307.6167 (section 2.2)
- raattgift 4y ago
  Your [1] <https://arxiv.org/abs/1307.6167 https://arxiv.org/abs/1307.6167> is a really interesting choice for examining the use of "emergence" in the broad among quantum gravity researchers. I think looking down to the start of §6 of your [1] is even more fruitful than §2.2: "... novel form of dynamics that can be applied to a unique system -- the universe as a whole [--] that is neither quantum mechanics nor general relativity[,] from which quantum physics and space-time emerge as approximate descriptions of systems that may be regarded to a sufficient degree of approximation as isolated subsystems." Or, more succintly and focusing on the gravitational content, "the Einstein Field Equations may be derived for some part(s) of a universe described by our theory", with the additional constraint, "but our theory cannot be derived from General Relativity". Compare with Newton's gravitation and its ability to be derived in the weak field, low speed limit of General Relativity (and that physically interesting generally curved spacetimes have large regions that are effectively flat). Generalizing, a theory of gravity is emergent when its fundamental equation(s) can be derived from a different dynamical theory, and the derivation is a one-way street. However, "emergent" gets used in a different sense only a few paragraphs later in [1]: "Time reversal invariance is amongst the symmetries that must emerge from the coarse graining that neglects the unique identity of each event. From our perspective fundamental physics is time asymmetric and the apparent time symmetry of the laws of nature is approximate and emergent." In this case they are not strictly speaking deriving time symmetry from their dynamical theory, but rather they are claiming that averaging the behaviour of their theory across some region(s) matches observation.
photochemsyn 4y ago
I think 'emergent property' just means it's something that depends on the particular configuration of a set of elements that vanishes if you just look at the elements in isolation. E.g. words are an emergent property of the elements of an alphabet. It is kind of hand-wavy and you often find the phrase 'holistic' in the same paragraph as 'emergent', which reflects that it's a kind of pushback against entirely reductive approaches, but it really just means that if you want to reconstruct a complex entity (like an automobile) you can't just count up the parts, at each stage of reduction you need to save this set of information describing the relationships between elements if you ever want to reconstruct the overall system from the most fundamental components. It's essentially just an abstraction, I think. The justification is that you can wrap up complexity into hierarchies of little black boxes that have predictable behavior. E.g. https://guava.physics.uiuc.edu/~nigel/courses/569/Essays_Spring2018/Files/gupta.pdf https://guava.physics.uiuc.edu/~nigel/courses/569/Essays_Spr... >"The idea of emergence in physics is pervasive especially in condensed matter and cold atom physics. For example, superconductivity and superfluidity are both described by a condensate, which is an emergent state of matter with finite fraction of particles in the ground state and long range order." The suggestion here (further developed in above paper) is that spacetime is also a kind of 'effective description' based on some other underlying microscopic organized structure, which is a theory that's likely hard to test.
- nemo44x 4y ago
  > just means it's something that depends on the particular configuration of a set of elements that vanishes if you just look at the elements in isolation Sort of like how all the parts of an engine, even when connected, do nothing if fuel isn’t being pumped through. We can not proclaim we have knowledge of the engine by simply understanding many of its parts but failing to grasp how fuel moves through it. And instead say when these parts are together motion “emerges” and believe we are profound.
  - tsunagatta 4y ago
    Linear and highly predictable systems like automobile engines are not really comparable to chaotic systems like the weather or the universe: they demand separate modes of analysis. Emergent behavior is one of these lenses of analysis that is useful for chaotic systems, so it is natural that trying to make comparisons to an engine don’t really work with it. For a simple physical system that is chaotic, i.e. does display emergent behavior, good examples I’ve heard are things like triple pendulums, or the currents of water in a river.
CuriouslyC 4y ago
In the case of spacetime, I think emergent just means that spacetime exists as a result of the interaction of energy, and there would be no spacetime without its interaction. It's more a claim about whether spacetime is a thing-in-itself.
dclowd9901 4y ago
You don’t think it’s important to identify “position” as an “emergent phenomenon”? That idea in itself is novel as fuck. Nevermind how someone could actually begin to explain it.
phs318u 4y ago
Here’s an example from your daily life. Wetness. Wetness is an emergent property of a liquid. A single molecule is neither wet nor dry, but when you have many such molecules, they collectively behave in ways that exhibit new properties such as phase transitions. Emergent properties are definitely a thing. The reason you’re hearing more about them is because we’re paying more attention to them in lots of domains, one of the most recent and date I say common around these here parts, being the study of “intelligence”.
DemocracyFTW2 4y ago
As others have pointed out, ocean waves are an emergent property of a body of a sufficiently large number of water molecules in a place with gravity and a dynamic atmosphere. I'd like to add—what is an ocean wave? It does exert measurable forces, it has a measurable weight and speed and height, but when it moves it will be made up of a 100% distinct set of material particles than just a moment ago. It can arise and subside without discernible trace although of course both matter and energy will be preserved. When you think about it a wave is not so different from anything else that exists. Yesterday's rock is tomorrows top-soil, before it becomes part of a plant, after which some of its former constituents will seep back into the ground while others take to the skies. In the future, all of these components might meet again to form a new rock. All of these things are emergent and evanescent. Their properties can hardly be predicted from the sum of their parts. When you think of it, there are many words for concepts—'liberty', 'inflation', 'boredom', 'exaggeration'—that are essential to the human experience and can even be partly made measurable, but that do not have any manner of physical reality.
- what-the-grump 4y ago
  Their properties can hardly be predicted from the sum of their parts. That’s not true. We know when water boils, we know tension laws, we know a ton to predict and define the interactions. We know how to add carbon to iron, we know how make glass withstand huge loads. We know material limits because we rely on those material limits to build our world. We choose to ignore those limits, the outcomes, the effects, climate change, earth is round, smoking is bad for you, etc. If we wanted to know that chemical reaction takes place in your body that makes you feel boredom, I am sure we could, we figured out cocaine and pain killers, there is just no profit in making a boredom pill. The world is not as romantic as poets make it out to be. Sun goes up sun goes down never a miscommunication. Complex, sure.
the-mitr 4y ago
Even if you know a lot many things, you cannot predict for sure how the system will behave on another level. See this classic paper by Anderson titled "More is different" on this topic which considers hard science and its inability to predict emergent phenomena https://cse-robotics.engr.tamu.edu/dshell/cs689/papers/anderson72more_is_different.pdf https://cse-robotics.engr.tamu.edu/dshell/cs689/papers/ander...
myrmidon 4y ago
"Emergent property" is a very fitting, useful and appropriate description for complex behavior that results from simple rules. An example would be the centrifugal force, which "emerges" from basic Newtonian inertia. Or the skin effect in AC electrics which (like pretty much ALL of circuit theory) is just a consequence of a few electrodynamic laws (Maxwell etc.). But just knowing the basic laws does NOT mean that we can grasp all of the emergent behavior that necessarily follows-- physics => chemistry => biology would be the same thing, otherwise :P
- mindslight 4y ago
  In examples from the physical world, I think one could conceivably claim that there are some underlying basic rule(s) that we haven't discovered yet, which would explain the "emergent" behavior. However if you take a look at cellular automata, which are artificial and thus completely defined, it's much clearer that complex "emergent" behavior really can result from nothing but very simple rules.
stevenhuang 4y ago
and that is what happens when one thinks they've developed an understanding of a term solely from reading how the term is used you should probably read over https://en.wikipedia.org/wiki/Emergence https://en.wikipedia.org/wiki/Emergence to convince yourself that emergence as a distinct concept is a useful abstraction to have

lanstin 4y ago

System availability is an emergent property - I can build five nines of availability out of components with just two nines. Retries, algorithmic handling of failure, and the like.

Dylan16807 4y ago

> The motion of an automobile isn’t an “emergent” thing you can claim because you don’t know how engines and transmissions work. That's the opposite of what emergent means, isn't it? Because of force on the transmission, you can say that the motion of the vehicle is emergent rather than needing its own framework or explanation.

CaptainNegative 4y ago

Seems like pretending to know what the word emergent means in physics is an emergent phenomenon on HN. It's not wishy washy, it has a precise meaning that can be both derived and, typically, refuted.

nextaccountic 4y ago

Emergent just means that it's not the basic building block; it's made up of other, more fundamental things. So for example thermodynamics is emergent (even though it is fully studied and relatively well understood) because it arises from interactions of particles. If you say that spacetime is emergent that is a big deal: it means that, while it can be studied on its own, it's actually composed of other, more fundamental things. But you still need to show that a) this other fundamental thing actually exists, and b) we can show mathematically how the spacetime works, in terms of those other fundamental thing (just like you can show how thermodynamics works in terms of statistical mechanics) And that's where your "because you don't know how it works" thing breaks apart: one can't claim to have solved this problem without tacking b).

nemo44x 4y ago
> it's made up of other, more fundamental things Then explain those things and prove they exist. Otherwise this just sounds like bullshit. There’s a difference between observing thermodynamics (and not trying to answer why but rather how we observe it - big difference!) and writing equations we can measure and just saying “it’s emergent” to “…” things we are unable to answer “I don’t know to”.
- doctor_eval 4y ago
  That seems to be exactly what they are trying to do: > Lee Smolin is working on an idea where the building blocks are events where momentum is exchanged.Space, and hence position, is an emergent phenomena. It’s perfectly OK to speculate that perhaps gravity, say, is not fundamental, but instead emerges from interactions or whatever at a lower layer that we haven’t yet identified. What word would you use?
- Maursault 4y ago
  > Otherwise this just sounds like bullshit? Yet it is very compelling bullshit that stands up to intense scientific scrutiny.[1] [1] https://einstein.stanford.edu/content/relativity/a11332.html https://einstein.stanford.edu/content/relativity/a11332.html

midlightdenight 4y ago

There’s probably some places where it’s used where it shouldn’t be, but there is such a thing as “emergent”. I think it helps to see an easy example first. Take a great body of water (h2o) on earth, such as the ocean. That water has waves and those waves have amplitudes, as well as other properties such as crests. A molecule (or even a few) of water (h2o) doesn’t really have these properties. It doesn’t have crests. You could argue it has amplitudes. Crests are an emergent property of large masses of water molecules within a specific system. There’s no crest to a water molecule. Similarly, for demonstration purposes we could say there’s no waves/crests when gravity is removed. So when I hear emergent, I imagine properties that show up under certain conditions within a system, that were not present in individual components.

nemo44x 4y ago
There’s a whole lot of “…” between a water molecule and a wave. There is nothing emergent about it. “Emergent” is a bullshit answer.
- jcparkyn 4y ago
  You seem to have a different definition of "emergent" to the rest of the world. Just because there _is_ an explanation for waves doesn't stop them from being an emergent behaviour.

magicalhippo 4y ago

In this case there's something more concrete, in the form of equations[1], behind the usage of the word. [1]: https://arxiv.org/abs/1307.6167 https://arxiv.org/abs/1307.6167 (section 2.2)

raattgift 4y ago
Your [1] <https://arxiv.org/abs/1307.6167 https://arxiv.org/abs/1307.6167> is a really interesting choice for examining the use of "emergence" in the broad among quantum gravity researchers. I think looking down to the start of §6 of your [1] is even more fruitful than §2.2: "... novel form of dynamics that can be applied to a unique system -- the universe as a whole [--] that is neither quantum mechanics nor general relativity[,] from which quantum physics and space-time emerge as approximate descriptions of systems that may be regarded to a sufficient degree of approximation as isolated subsystems." Or, more succintly and focusing on the gravitational content, "the Einstein Field Equations may be derived for some part(s) of a universe described by our theory", with the additional constraint, "but our theory cannot be derived from General Relativity". Compare with Newton's gravitation and its ability to be derived in the weak field, low speed limit of General Relativity (and that physically interesting generally curved spacetimes have large regions that are effectively flat). Generalizing, a theory of gravity is emergent when its fundamental equation(s) can be derived from a different dynamical theory, and the derivation is a one-way street. However, "emergent" gets used in a different sense only a few paragraphs later in [1]: "Time reversal invariance is amongst the symmetries that must emerge from the coarse graining that neglects the unique identity of each event. From our perspective fundamental physics is time asymmetric and the apparent time symmetry of the laws of nature is approximate and emergent." In this case they are not strictly speaking deriving time symmetry from their dynamical theory, but rather they are claiming that averaging the behaviour of their theory across some region(s) matches observation.

photochemsyn 4y ago

I think 'emergent property' just means it's something that depends on the particular configuration of a set of elements that vanishes if you just look at the elements in isolation. E.g. words are an emergent property of the elements of an alphabet. It is kind of hand-wavy and you often find the phrase 'holistic' in the same paragraph as 'emergent', which reflects that it's a kind of pushback against entirely reductive approaches, but it really just means that if you want to reconstruct a complex entity (like an automobile) you can't just count up the parts, at each stage of reduction you need to save this set of information describing the relationships between elements if you ever want to reconstruct the overall system from the most fundamental components. It's essentially just an abstraction, I think. The justification is that you can wrap up complexity into hierarchies of little black boxes that have predictable behavior. E.g. https://guava.physics.uiuc.edu/~nigel/courses/569/Essays_Spring2018/Files/gupta.pdf https://guava.physics.uiuc.edu/~nigel/courses/569/Essays_Spr... >"The idea of emergence in physics is pervasive especially in condensed matter and cold atom physics. For example, superconductivity and superfluidity are both described by a condensate, which is an emergent state of matter with finite fraction of particles in the ground state and long range order." The suggestion here (further developed in above paper) is that spacetime is also a kind of 'effective description' based on some other underlying microscopic organized structure, which is a theory that's likely hard to test.

nemo44x 4y ago
> just means it's something that depends on the particular configuration of a set of elements that vanishes if you just look at the elements in isolation Sort of like how all the parts of an engine, even when connected, do nothing if fuel isn’t being pumped through. We can not proclaim we have knowledge of the engine by simply understanding many of its parts but failing to grasp how fuel moves through it. And instead say when these parts are together motion “emerges” and believe we are profound.
- tsunagatta 4y ago
  Linear and highly predictable systems like automobile engines are not really comparable to chaotic systems like the weather or the universe: they demand separate modes of analysis. Emergent behavior is one of these lenses of analysis that is useful for chaotic systems, so it is natural that trying to make comparisons to an engine don’t really work with it. For a simple physical system that is chaotic, i.e. does display emergent behavior, good examples I’ve heard are things like triple pendulums, or the currents of water in a river.

CuriouslyC 4y ago

In the case of spacetime, I think emergent just means that spacetime exists as a result of the interaction of energy, and there would be no spacetime without its interaction. It's more a claim about whether spacetime is a thing-in-itself.

dclowd9901 4y ago

You don’t think it’s important to identify “position” as an “emergent phenomenon”? That idea in itself is novel as fuck. Nevermind how someone could actually begin to explain it.

phs318u 4y ago

Here’s an example from your daily life. Wetness. Wetness is an emergent property of a liquid. A single molecule is neither wet nor dry, but when you have many such molecules, they collectively behave in ways that exhibit new properties such as phase transitions. Emergent properties are definitely a thing. The reason you’re hearing more about them is because we’re paying more attention to them in lots of domains, one of the most recent and date I say common around these here parts, being the study of “intelligence”.

DemocracyFTW2 4y ago

As others have pointed out, ocean waves are an emergent property of a body of a sufficiently large number of water molecules in a place with gravity and a dynamic atmosphere. I'd like to add—what is an ocean wave? It does exert measurable forces, it has a measurable weight and speed and height, but when it moves it will be made up of a 100% distinct set of material particles than just a moment ago. It can arise and subside without discernible trace although of course both matter and energy will be preserved. When you think about it a wave is not so different from anything else that exists. Yesterday's rock is tomorrows top-soil, before it becomes part of a plant, after which some of its former constituents will seep back into the ground while others take to the skies. In the future, all of these components might meet again to form a new rock. All of these things are emergent and evanescent. Their properties can hardly be predicted from the sum of their parts. When you think of it, there are many words for concepts—'liberty', 'inflation', 'boredom', 'exaggeration'—that are essential to the human experience and can even be partly made measurable, but that do not have any manner of physical reality.

what-the-grump 4y ago
Their properties can hardly be predicted from the sum of their parts. That’s not true. We know when water boils, we know tension laws, we know a ton to predict and define the interactions. We know how to add carbon to iron, we know how make glass withstand huge loads. We know material limits because we rely on those material limits to build our world. We choose to ignore those limits, the outcomes, the effects, climate change, earth is round, smoking is bad for you, etc. If we wanted to know that chemical reaction takes place in your body that makes you feel boredom, I am sure we could, we figured out cocaine and pain killers, there is just no profit in making a boredom pill. The world is not as romantic as poets make it out to be. Sun goes up sun goes down never a miscommunication. Complex, sure.

the-mitr 4y ago

Even if you know a lot many things, you cannot predict for sure how the system will behave on another level. See this classic paper by Anderson titled "More is different" on this topic which considers hard science and its inability to predict emergent phenomena https://cse-robotics.engr.tamu.edu/dshell/cs689/papers/anderson72more_is_different.pdf https://cse-robotics.engr.tamu.edu/dshell/cs689/papers/ander...

myrmidon 4y ago

"Emergent property" is a very fitting, useful and appropriate description for complex behavior that results from simple rules. An example would be the centrifugal force, which "emerges" from basic Newtonian inertia. Or the skin effect in AC electrics which (like pretty much ALL of circuit theory) is just a consequence of a few electrodynamic laws (Maxwell etc.). But just knowing the basic laws does NOT mean that we can grasp all of the emergent behavior that necessarily follows-- physics => chemistry => biology would be the same thing, otherwise :P

mindslight 4y ago
In examples from the physical world, I think one could conceivably claim that there are some underlying basic rule(s) that we haven't discovered yet, which would explain the "emergent" behavior. However if you take a look at cellular automata, which are artificial and thus completely defined, it's much clearer that complex "emergent" behavior really can result from nothing but very simple rules.

stevenhuang 4y ago

and that is what happens when one thinks they've developed an understanding of a term solely from reading how the term is used you should probably read over https://en.wikipedia.org/wiki/Emergence https://en.wikipedia.org/wiki/Emergence to convince yourself that emergence as a distinct concept is a useful abstraction to have