Sync / 싱크

Sync: How Order Emerges From Chaos In the Universe, Nature, and Daily Life Steven H. Strogatz

Sometimes order appears from nowhere. When water freezes, it becomes ice suddenly, not step-by-step. Fireflies sometimes fire in order. Crickets chirp in unison. There are many kinds of spontaneous order in nature. This book deals with such order and how and from where the order emerges. Our world is inherently non-linear, that is, complex. That non-linearity causes negative feedbacks from which order emerges. Several interesting effects are by-product of emerged sync, like laser, superconductor, Bose-Einstein condensate or so. 

Sync(order) is beautifully by itself. That's why many cultural forms has sync in them. Spontaneity and Suddenness of Sync is miraculous. When we pour our efforts onto something, some kind of magic might appear. It's a lesson from this book.

올해의 마지막 교양과학서, Sync이다. 

물이 얼어붙어 얼음이 될 때, 물은 천천히 얼음으로 변하는 것이 아니라 어느 순간 갑자기 얼음으로 변화한다. 왜 갑자기 얼음으로 변하는 걸까. 비단 물이 얼음으로 될 때 뿐만이 아니더라도 무질서가 질서로 갑자기 변화하는 순간들이 존재한다. 그것을 아무렇지도 않게 지나치는 것이 보통 사람, 그리고 그것을 보면서 자연의 경이를 느끼는 사람이 과학자이다.

• 반딧불이의 불빛이 서로 박자를 맞추어 깜빡이는 것. 
• 귀뚜라미들이 합창하는 것
• 콘써트에서 박수를 칠 때 그것이 저절로 박자가 맞는 것
• 진자 두 개가 서로 진동수를 맞추도록 조절하는 것
• 달이 지구쪽으로 항상 특정한 면만 보이고 있는 것
• 목성이 소행성asteroid을 태양,지구쪽으로 던져대고 있다는 것, 그리고 아마 그로 인해 공룡이 멸종되었을 것이라는 것
• 다리bridge가 행인들의 소동에 의해 진동하는 것
• 레이저, 초전도현상, 보즈-아인슈타인 응축체Bose-Einstein condesate, 조셉슨Josephson 소자
• Strange attractor: 카오스계에 내재된 질서의 한 예
• 스케일프리scale-free 네트워크 혹은 작은 세계small world 네트워크. 그리고 small world network에서의 진동자들oscillators
• 신경계에서 나타나는 신호 방출firing의 동기화

자연은 비선형계이며 비선형계에서 나타나는 두 가지 종류의 Sync, 즉 음의 피드백에 의한 질서유지와 양의 피드백에 의한 여러 현상 (레이저 등)은 참으로 경이롭지 않는가... 라는 이야기. 

자연이 보여주고 있는 어느 순간 갑자기 생겨나는 질서. 우리네 삶에도 어느 순간 갑자기 무엇인가 찾아 올까? 비선형계가 나에게 이야기하고 있는 것은 자연의 경이뿐만이 아닌 삶을 살아가는 방식에 대한 어떠한 비유인 듯하다. 

• We interpret persistent sync as a sign of intelligence, planning, and choreography.사람은 SYNC된 동작을 보는 것을 좋아하고 그래서 군무가 유행하는지도. 바보들도 연습하면 동작은 맞출수 있으니까.
• The same mathematical structure cropped up in models of other interacting systems, ranging from forest fires to mass extinctions. In each case, an individual element is subjected to increasing pressure, builds up toward a threshold, then suddenly relieves its stress and spreads it to others, potentially triggering a domino effect. 나쁜 일이든 좋은 일이든 떼로 몰려 일어난다.
• Nobert Wiener's analysis of Brownian motion, the erratic jiggling of molecules in solution, went far beyond Albert Einstein's intuitive approach to the same problem, and his methods laid the foundation for Richard Feynman's work in quantum electrodynamics. Cybernetics의 Nobert Wiener가 이런 사람이었다니, 놀랐다. 18세에 Harvard에서 박사를 받았다기도.
• Whenever the whole is different from the sum of the parts -- whenever there's cooperation or competition going on -- the governing equations must be nonlinear. 협동이나 경쟁이 들어가면 논리니어, 즉 실생활, 사회현상의 대부분은 논리니어.
• How can a system of millions of particles spontaneously organize itself?
• How long a subject stayed asleep did not depend on how long he had been awake beforehand; it depended on when he fell asleep in relation to his cycle of body temperature: Long sleeps always began at high temperature and short sleeps at low temperature. 즉 호르몬 분비로 인한 생체 리듬이 형성되어 있어서, 짧은 낮잠이 아닌다음에야 일어나는 시간이 일정해진다는것. 몸이 따뜻해지면 잠이 깨고, 추우면 잠을 자라? ^_^. 4-6AM은 가장 낮은 체온. 체르노빌을 포함한 대참사는 다 이 시기에 일어났다. 이 시기에는 차조심해야한다.
• The intriguing suggestion is that we become sleepy in the mid-afternoon, not because we have eaten a big lunch, or because it is hot outside, but because our circadian pacemaker demands it..
• Although the role of serendipiry is familiar, what's not so well appreciated is how different serendipiry is from luck. Serendipity is not just an apparent aptitude for making fortunate discoveries accidentally as my dictionary defines it. Serendipitous discoveries are always made by people in a particular frame of mind, people who are focused and alert because they're searching for something. They just happen to find something else.
• miraculous consonance of two pendulums: 두 개의 진자가 엇갈리게 교차되도록 해 놓았을 때 두개의 진자주기가 공명하는 현상. Hyugens가 발견. 그러고 보면 예전 어린이회관에 설치되어 있었던 커다란 진자 생각이 난다. 원리가 무엇인지도 몰라도 그냥 구경에 시간가는 줄 몰랐던 그 시절.
• At a critical temperature, the clouds broaden so much that they srarr to overlap, and the bosons srarr ro mingle. As soon as rhar happens, said Einstein, a large proportion of them should spontaneously collapse into the same quantum state, the state of lowest possible energy. 초전도현상. 초전도 현상을 들은건 30년전. 그 기반이치를 듣게된 것은 지금에 와서야. *한숨*
• Then suddenly, once the coupling exceeds a certain threshold (because there are enough people on the bridge to shake it sufficiently), synchrony breaks out cooperatively
• The most important result of the simulations was that over a broad intermediate range of rewiring, the model nenvorks were very clustered and very small at the same time. That peculiar combination was new to mathematics. In traditional networks, size and clustering go hand in hand. Random neworks are small and poorly clustered; regular ones are big and highly clustered. The rewired networks managed to be both small and highly clustered simultaneously.
• The main result is that the model displays two distinct phase transitions, popularly known as tipping points. If the nework is too sparsely connected, it fragments into tiny islands and cascades can't spread beyond any of them. At a higher, critical level of connectivity-the first tipping point-the islands abruptly link together into a giant mesh and global cascades become possible. An initial seed can now trigger an epidemic of change that ultimately infects much of the population. With further increases in connectivity, the cascades at first become even larger and more likely, as one might expec, but then-paradoxically-they become larger yet rarer, suddenly vanishing when the newrork exceeds a critical density of connections. This second tipping point arises because of a dilution effect: When a node has too many neighbors, each of them has too little influence to trigger a toppling on its own.
• spontaneous slowdown in highway/slowing down of individual applause rate: complex network에는 모두 phase transition이 일어나나? 사회라는 네트워크에서 그에 해당 되는 것은 무엇일까?
• Naturally, each subject remembered some words and forgot others, but what was fascinating is that their neurons behaved differently in the two cases, at rhe moment the words were first viewed. A quarter of a second after viewing words that they'd later remember, their brains showed a rush of synchrony between rhe hippocampus and rhinal cortex, but there was no synchrony when they first viewed words that they'd later forget. To exaggerate a bit, this means that by watching the electrical pattern in someone's brain when he or she tries to memorize a word, you can predict whether he or she will succeed. You can see if the brain is dropping the ball. 기억, 인지에서도 신경의 sync가 관찰된다.
• "consciousness involves synchronized firing of neurons ar the millisecond level, whereas uncorrelated firing can infuence behavior without generating that special buzz in the head."
• At its strangest, that special buzz can trigger an indescribably odd sensation. If you have not felt it yourself, it will sound ridiculous, but if you have, you'll know exactly what I mean, and it's a chilling feeling. It happens to me maybe once or twice a year, and it comes without warning. I'll be standing in front of the mirror, brushing my teeth, and I look at myself and suddenly think: Who's in there? Or, Who's that?