6 ms·

How do glasses form? What order parameter determines the properties of liquids? Are there an unifying properties determining the structure of atomic liquids? W

How do glasses form? What order parameter determines the properties of liquids? Are there an unifying properties determining the structure of atomic liquids? What determines the network properties of liquids? Here's a more tangible one; Is solid hydrogen stable? I did my PhD in this area and even discovered liquid polymorphism in atomic Cerium. There are tons of unanswered questions like this! It's bonkers how many things we know we don't know, just think of the things we don't know we don't know :p

tsomctl 6y ago
There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know. - Rumsfeld
- sparky_z 6y ago
  I've never understood why people mock him for saying this. It frequently shows up on lists of stupid political quotes/"Bushisms". But not only is it absolutely true and important for planners to understand, it's stated clearly and concisely. Do most people just look at it and see word salad? I don't get it.
  - novaleaf 6y ago
    It's easier to mock someone for the strange sounding words comming out of their mouth, rather then try to understand the meaning.
  - schoen 6y ago
    It might be interesting to see a list of "often-mocked sayings that have a point". Two that I know of involving politicians and the Internet are https://en.wikipedia.org/wiki/Al_Gore_and_information_technology#Urban_legend_that_Gore_claims_to_have_invented_the_Internet https://en.wikipedia.org/wiki/Al_Gore_and_information_techno... https://en.wikipedia.org/wiki/Series_of_tubes https://en.wikipedia.org/wiki/Series_of_tubes I'm sorry to say that I've personally made fun of both of these people for these soundbites in a way that I now regret.
    - tjoff 6y ago
      It seems a bit charitable to say that the series of tubes has a point? I'm sure you can also attach a point to a random set set of words. The context makes it even more damning.
      - asiachick 6y ago
        What's wrong with the analogy? Tubes each have a limited capacity, so do the various ways I connect to the net. That capacity can fill. Tubes connect and their contents routed similar to the contents of internet traffic. If you drew a diagram of water tubes and a diagram of internet connections they'd both resemble each other. I'm still not sure why this is a bad analogy even in context.
        jeffbee 6y ago
        In the context of the speaker's insane quote, in which he blamed streaming video for a 4-day delay of his personal emails, it doesn't make much sense. Also it's a rhetorical fallacy to suggest that because a thing is not another thing, then it must be a third thing. Really, the Internet is neither a truck nor a series of tubes.
        Dylan16807 6y ago
        Right. He's making an analogy about how things wait in line, and he's talking about for significant amounts of time, not fractions of a second. That's not how the internet works at all. Competing data flows slow down a bit but all run simultaneously. We don't even have to get into the silly parts like "the people who are streaming through 10, 12 movies at a time or a whole book at a time"
        ajuc 6y ago
        Internet is a bidirectional graph with constrained bandwith (flow). Series of tubes is a perfectly fine analogy. His thesis (about video streaming) was false, but his analogy was ok, people jumped on it for the wrong reasons (as it often happens in politics).
  - earthboundkid 6y ago
    Because Rumsfeld was constantly getting philosophical in briefings about “what is a war? Clausewitz said…” when his job was to win an actual, concrete war in Iraq, and we had no idea who the hell were setting the IEDs and kidnapping foreigners. He was too far up his own ass to notice he was losing.
    - oh_sigh 6y ago
      Well he is a Princeton man.
    - jacobush 6y ago
      He was winning, the war machine was rolling and fresh contracts signed, in blood.
  - klenwell 6y ago
    I actually like the quote. But there are a couple reasons Rumsfeld deserves to get raked over the coals for it: 1. The Bush Administration lied like war criminals to lead us into the Iraq War. So even though he may have been referring to technical operational complications of winning the peace in Iraq or whatever, it was easy to construe it as more bullshit gibberish to justify a crime against humanity. 2. Related to 1. There were plenty of known knowns with Iraq that the Bush Administration treated as some variety of unknown. It sounded a lot like he was using a clever philosophical aphorism to make excuses for stupid blatant errors of judgment. An NPR recap of the path to war at a time when the full scope of the fraud was still coming to light: https://www.npr.org/templates/story/story.php?storyId=5289399 https://www.npr.org/templates/story/story.php?storyId=528939...
  - jorgesborges 6y ago
    It’s not stated as clearly or precisely as I think it could be. I’ve heard it articulated better without giving each epistemic category its own jargon like “unknown unknowns”. There are things you know, and things you don’t know. Furthermore there are things you know you don’t know. But be aware that there are things you don’t even know you don’t know.
    - sparky_z 6y ago
      Perhaps. I suppose that comes down to matter of taste. But either way, I certainly don't think his formulation sinks to level of mockably bad. Especially since it was spoken off the cuff in response to a question from the press.
  - lordgrenville 6y ago
    No, at the time it was mocked but over time people's attitudes changed. It even has a Wikipedia page. ("While the remarks initially led to some ridicule towards the Bush administration in general and Rumsfeld in particular, the consensus regarding it has shifted over the years, and it now enjoys some level of respect.") https://en.wikipedia.org/wiki/There_are_known_knowns https://en.wikipedia.org/wiki/There_are_known_knowns
  - garmaine 6y ago
    Most people just look at it and see word salad. He is in fact stating, correctly if not clearly for a general audience, a fundamental lesson of project planning. But the whole "known-unknown / unknown-unknown" thing is way above most people's heads.
  - jlarocco 6y ago
    I think the problem is less with the statement itself, and more to do with him using it to help justify the Iraq war, where some of the "known knowns" and "unknown unknowns" were actually speculation, exaggerated, or even made up completely.
- new2628 6y ago
  You should check Slavoj Zizek's take on this quote, where he completes the quadrant with the "unknown knowns", i.e. stuff that we know but we don't know that we know it, as in subconscious biases, ideology, etc.
  - adolph 6y ago
    I think that "tacit knowledge" is close to the idea of "unknown knowns." Another interesting quadrant model is the Johari Window which has to do with what one knows about oneself and what others know about oneself. https://www.communicationtheory.org/the-johari-window-model/ https://www.communicationtheory.org/the-johari-window-model/
- jimmySixDOF 6y ago
  So this is actually official terminology used by Project Management Institute in the PMBOK and refers to special budgets set aside for risk contigency : 6.4.2.6 DATA ANALYSIS Reserve analysis Reserve analysis is used to determine the amount of contingency and management reserve needed for the project. Duration estimates may include contingency reserves, sometimes referred to as schedule reserves, to account for schedule uncertainty. Contingency reserves are the estimated duration within the schedule baseline, which is allocated for identified risks that are accepted. Contingency reserves are associated with the known-unknowns, which may be estimated to account for this unknown amount of rework. The contingency reserve may be a percentage of the estimated activity duration or a fixed number of work periods. Contingency reserves may be separated from the individual activities and aggregated. As more precise information about the project becomes available, the contingency reserve may be used, reduced, or eliminated. Contingency should be clearly identified in the schedule documentation. Estimates may also be produced for the amount of management reserve of schedule for the project. Management reserves are a specified amount of the project budget withheld for management control purposes and are reserved for unforeseen work that is within scope of the project. Management reserves are intended to address the unknown-unknowns that can affect a project. Management reserve is not included in the schedule baseline, but it is part of the overall project duration requirements. Depending on contract terms, use of management reserves may require a change to the schedule baseline.
- dredmorbius 6y ago
  The saying long predates Rumsfeld's 2002 usage: https://en.m.wikipedia.org/wiki/There_are_known_knowns https://en.m.wikipedia.org/wiki/There_are_known_knowns I'd first encountered the idea of "unknown unknowns", or unk-unk, in a 1982 book, Forced Options, p. 10: https://archive.org/details/forcedoptionssoc0000shin_c8x7/page/10/mode/2up?q=unk-unk https://archive.org/details/forcedoptionssoc0000shin_c8x7/pa... The notion dates at least as far back as 1955.
  - no-s 6y ago
    I'm pretty sure Rumsfeld was paraphrasing J.B.S Haldane from a ca. 1927 publication, or Eddington's paraphrase of Haldane's observation: "The Universe is not only queerer than we suppose, but queerer than we can suppose." Rumsfeld never claimed it to be original with him.
cinquemb 6y ago
> How do glasses form? Reminds me of cool paper (i think) from one folks I worked with describes in the abstract[0]: "We describe numerical simulations and analyses of a quasi-one-dimensional (Q1D) model of glassy dynamics. In this model, hard rods undergo Brownian dynamics through a series of narrow channels connected by J intersections. We do not allow the rods to turn at the intersections, and thus there is a single, continuous route through the system. This Q1D model displays caging behavior, collective particle rearrangements, and rapid growth of the structural relaxation time, which are also found in supercooled liquids and glasses. The mean-square displacement Σ(t) for this Q1D model displays several dynamical regimes: 1) short-time diffusion Σ(t)∼t, 2) a plateau in the mean-square displacement caused by caging behavior, 3) single-file diffusion characterized by anomalous scaling Σ(t)∼t0.5 at intermediate times, and 4) a crossover to long-time diffusion Σ(t)∼t for times t that grow with the complexity of the circuit. We develop a general procedure for determining the structural relaxation time tD, beyond which the system undergoes long-time diffusion, as a function of the packing fraction ϕ and system topology. This procedure involves several steps: 1) define a set of distinct microstates in configuration space of the system, 2) construct a directed network of microstates and transitions between them, 3) identify minimal, closed loops in the network that give rise to structural relaxation, 4) determine the frequencies of `bottleneck' microstates that control the slow dynamics and time required to transition out of them, and 5) use the microstate frequencies and lifetimes to deduce tD(ϕ). We find that tD obeys power-law scaling, tD∼(ϕ∗−ϕ)−α, where both ϕ∗ (signaling complete kinetic arrest) and α>0 depend on the system topology. " But yeah, so much amazing things out there, I could read and think about stuff forever lol [0] https://arxiv.org/abs/1401.0960 https://arxiv.org/abs/1401.0960

tsomctl 6y ago

There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know. - Rumsfeld

sparky_z 6y ago
I've never understood why people mock him for saying this. It frequently shows up on lists of stupid political quotes/"Bushisms". But not only is it absolutely true and important for planners to understand, it's stated clearly and concisely. Do most people just look at it and see word salad? I don't get it.
- novaleaf 6y ago
  It's easier to mock someone for the strange sounding words comming out of their mouth, rather then try to understand the meaning.
- schoen 6y ago
  It might be interesting to see a list of "often-mocked sayings that have a point". Two that I know of involving politicians and the Internet are https://en.wikipedia.org/wiki/Al_Gore_and_information_technology#Urban_legend_that_Gore_claims_to_have_invented_the_Internet https://en.wikipedia.org/wiki/Al_Gore_and_information_techno... https://en.wikipedia.org/wiki/Series_of_tubes https://en.wikipedia.org/wiki/Series_of_tubes I'm sorry to say that I've personally made fun of both of these people for these soundbites in a way that I now regret.
  - tjoff 6y ago
    It seems a bit charitable to say that the series of tubes has a point? I'm sure you can also attach a point to a random set set of words. The context makes it even more damning.
    - asiachick 6y ago
      What's wrong with the analogy? Tubes each have a limited capacity, so do the various ways I connect to the net. That capacity can fill. Tubes connect and their contents routed similar to the contents of internet traffic. If you drew a diagram of water tubes and a diagram of internet connections they'd both resemble each other. I'm still not sure why this is a bad analogy even in context.
      - jeffbee 6y ago
        In the context of the speaker's insane quote, in which he blamed streaming video for a 4-day delay of his personal emails, it doesn't make much sense. Also it's a rhetorical fallacy to suggest that because a thing is not another thing, then it must be a third thing. Really, the Internet is neither a truck nor a series of tubes.
        Dylan16807 6y ago
        Right. He's making an analogy about how things wait in line, and he's talking about for significant amounts of time, not fractions of a second. That's not how the internet works at all. Competing data flows slow down a bit but all run simultaneously. We don't even have to get into the silly parts like "the people who are streaming through 10, 12 movies at a time or a whole book at a time"
        ajuc 6y ago
        Internet is a bidirectional graph with constrained bandwith (flow). Series of tubes is a perfectly fine analogy. His thesis (about video streaming) was false, but his analogy was ok, people jumped on it for the wrong reasons (as it often happens in politics).
- earthboundkid 6y ago
  Because Rumsfeld was constantly getting philosophical in briefings about “what is a war? Clausewitz said…” when his job was to win an actual, concrete war in Iraq, and we had no idea who the hell were setting the IEDs and kidnapping foreigners. He was too far up his own ass to notice he was losing.
  - oh_sigh 6y ago
    Well he is a Princeton man.
  - jacobush 6y ago
    He was winning, the war machine was rolling and fresh contracts signed, in blood.
- klenwell 6y ago
  I actually like the quote. But there are a couple reasons Rumsfeld deserves to get raked over the coals for it: 1. The Bush Administration lied like war criminals to lead us into the Iraq War. So even though he may have been referring to technical operational complications of winning the peace in Iraq or whatever, it was easy to construe it as more bullshit gibberish to justify a crime against humanity. 2. Related to 1. There were plenty of known knowns with Iraq that the Bush Administration treated as some variety of unknown. It sounded a lot like he was using a clever philosophical aphorism to make excuses for stupid blatant errors of judgment. An NPR recap of the path to war at a time when the full scope of the fraud was still coming to light: https://www.npr.org/templates/story/story.php?storyId=5289399 https://www.npr.org/templates/story/story.php?storyId=528939...
- jorgesborges 6y ago
  It’s not stated as clearly or precisely as I think it could be. I’ve heard it articulated better without giving each epistemic category its own jargon like “unknown unknowns”. There are things you know, and things you don’t know. Furthermore there are things you know you don’t know. But be aware that there are things you don’t even know you don’t know.
  - sparky_z 6y ago
    Perhaps. I suppose that comes down to matter of taste. But either way, I certainly don't think his formulation sinks to level of mockably bad. Especially since it was spoken off the cuff in response to a question from the press.
- lordgrenville 6y ago
  No, at the time it was mocked but over time people's attitudes changed. It even has a Wikipedia page. ("While the remarks initially led to some ridicule towards the Bush administration in general and Rumsfeld in particular, the consensus regarding it has shifted over the years, and it now enjoys some level of respect.") https://en.wikipedia.org/wiki/There_are_known_knowns https://en.wikipedia.org/wiki/There_are_known_knowns
- garmaine 6y ago
  Most people just look at it and see word salad. He is in fact stating, correctly if not clearly for a general audience, a fundamental lesson of project planning. But the whole "known-unknown / unknown-unknown" thing is way above most people's heads.
- jlarocco 6y ago
  I think the problem is less with the statement itself, and more to do with him using it to help justify the Iraq war, where some of the "known knowns" and "unknown unknowns" were actually speculation, exaggerated, or even made up completely.
new2628 6y ago
You should check Slavoj Zizek's take on this quote, where he completes the quadrant with the "unknown knowns", i.e. stuff that we know but we don't know that we know it, as in subconscious biases, ideology, etc.
- adolph 6y ago
  I think that "tacit knowledge" is close to the idea of "unknown knowns." Another interesting quadrant model is the Johari Window which has to do with what one knows about oneself and what others know about oneself. https://www.communicationtheory.org/the-johari-window-model/ https://www.communicationtheory.org/the-johari-window-model/
jimmySixDOF 6y ago
So this is actually official terminology used by Project Management Institute in the PMBOK and refers to special budgets set aside for risk contigency : 6.4.2.6 DATA ANALYSIS Reserve analysis Reserve analysis is used to determine the amount of contingency and management reserve needed for the project. Duration estimates may include contingency reserves, sometimes referred to as schedule reserves, to account for schedule uncertainty. Contingency reserves are the estimated duration within the schedule baseline, which is allocated for identified risks that are accepted. Contingency reserves are associated with the known-unknowns, which may be estimated to account for this unknown amount of rework. The contingency reserve may be a percentage of the estimated activity duration or a fixed number of work periods. Contingency reserves may be separated from the individual activities and aggregated. As more precise information about the project becomes available, the contingency reserve may be used, reduced, or eliminated. Contingency should be clearly identified in the schedule documentation. Estimates may also be produced for the amount of management reserve of schedule for the project. Management reserves are a specified amount of the project budget withheld for management control purposes and are reserved for unforeseen work that is within scope of the project. Management reserves are intended to address the unknown-unknowns that can affect a project. Management reserve is not included in the schedule baseline, but it is part of the overall project duration requirements. Depending on contract terms, use of management reserves may require a change to the schedule baseline.
dredmorbius 6y ago
The saying long predates Rumsfeld's 2002 usage: https://en.m.wikipedia.org/wiki/There_are_known_knowns https://en.m.wikipedia.org/wiki/There_are_known_knowns I'd first encountered the idea of "unknown unknowns", or unk-unk, in a 1982 book, Forced Options, p. 10: https://archive.org/details/forcedoptionssoc0000shin_c8x7/page/10/mode/2up?q=unk-unk https://archive.org/details/forcedoptionssoc0000shin_c8x7/pa... The notion dates at least as far back as 1955.
- no-s 6y ago
  I'm pretty sure Rumsfeld was paraphrasing J.B.S Haldane from a ca. 1927 publication, or Eddington's paraphrase of Haldane's observation: "The Universe is not only queerer than we suppose, but queerer than we can suppose." Rumsfeld never claimed it to be original with him.

cinquemb 6y ago

> How do glasses form? Reminds me of cool paper (i think) from one folks I worked with describes in the abstract[0]: "We describe numerical simulations and analyses of a quasi-one-dimensional (Q1D) model of glassy dynamics. In this model, hard rods undergo Brownian dynamics through a series of narrow channels connected by J intersections. We do not allow the rods to turn at the intersections, and thus there is a single, continuous route through the system. This Q1D model displays caging behavior, collective particle rearrangements, and rapid growth of the structural relaxation time, which are also found in supercooled liquids and glasses. The mean-square displacement Σ(t) for this Q1D model displays several dynamical regimes: 1) short-time diffusion Σ(t)∼t, 2) a plateau in the mean-square displacement caused by caging behavior, 3) single-file diffusion characterized by anomalous scaling Σ(t)∼t0.5 at intermediate times, and 4) a crossover to long-time diffusion Σ(t)∼t for times t that grow with the complexity of the circuit. We develop a general procedure for determining the structural relaxation time tD, beyond which the system undergoes long-time diffusion, as a function of the packing fraction ϕ and system topology. This procedure involves several steps: 1) define a set of distinct microstates in configuration space of the system, 2) construct a directed network of microstates and transitions between them, 3) identify minimal, closed loops in the network that give rise to structural relaxation, 4) determine the frequencies of `bottleneck' microstates that control the slow dynamics and time required to transition out of them, and 5) use the microstate frequencies and lifetimes to deduce tD(ϕ). We find that tD obeys power-law scaling, tD∼(ϕ∗−ϕ)−α, where both ϕ∗ (signaling complete kinetic arrest) and α>0 depend on the system topology. " But yeah, so much amazing things out there, I could read and think about stuff forever lol [0] https://arxiv.org/abs/1401.0960 https://arxiv.org/abs/1401.0960