
Mitchell Feigenbaum, physicist who pioneered chaos theory, has died - yeellow
https://www.rockefeller.edu/news/26289-mitchell-feigenbaum-physicist-pioneered-chaos-theory-died/
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hanoz
I dwell on chaos theory. I don't think its significance has been properly
absorbed by the public consciousness yet. There's something simultaneously
liberating and unsettling about it.

For instance I'm often conscious that it's a mathematical near certainty that
if I'd done anything different in my earlier years, absolutely anything at
all, then my children would not exist, and therefore I cannot bring myself to
regret anything I ever did. Conversely it's unnerving to consider how unlikely
my own existence is in the first place.

Also, since appreciating chaos theory, I can no longer enjoy any movie
involving time travel.

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donaq
Correct me if I'm wrong, but chaotic systems are unpredictable because they
are complex and infinitesimally small variations in starting conditions result
in hugely different outcomes. They are not, however, non-deterministic. If the
universe is merely chaotic and not actually stochastic, then the existence of
you and your children are not only not unlikely, it was inevitable.

~~~
dreamcompiler
Exactly right. Unless you believe quantum mechanics throws a monkey wrench
into determinism. Which it certainly does in the realm of the very small.

Chaos theory and QM are completely orthogonal (by which I mean they say
different things about the universe, not that they are in conflict with one
another). And they both screw up the idea of a predictable universe.

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colordrops
Quantum mechanics demonstrating non-determinism in the realm of the very small
necessarily means that the macroscopic realm is also non-deterministic. A non-
zero percentage of events occur in which that one particle appearing in one
place rather than an is just enough to cause the macroscopic object to take a
materially different path. In fact a simple thought experiment shows that a
system could be engineered to demonstrate this. Add a sensor that reads which
way a particle goes in a double slit experiment and based on the direction,
flip a switch that makes a train go east or west based on the sensor read out.

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eridius
Adding a sensor to the double slit experiment to measure which slit the
particle goes through removes the quantum effects from the experiment.

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colordrops
Not sure what you mean. Quantum effects don't "disappear". They are physical
laws. Which slit the particle enters after the wave decoheres is precisely a
non-deterministic element of quantum mechanics.

~~~
bouncycastle
But wouldn't measuring something also alter the outcome? Ie. Observer Effect
[https://en.m.wikipedia.org/wiki/Observer_effect_(physics)](https://en.m.wikipedia.org/wiki/Observer_effect_\(physics\))

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colordrops
It doesn't alter the outcome. It causes it to decohere into a particular
outcome. There is no way to force a particular outcome, hence it being non-
deterministic.

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whyenot
I remember reading about him in _Chaos: Making a New Science_ where James
Gleick portrayed him as a young man. That was in the late 1980s when I was a
high school student. Time flies :(

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taneq
Great book, I read it a bunch of times. It made chaos theory really accessible
even to a highschooler.

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dreamcompiler
I was peripherally involved in chaos theory in the early 80s. I never met
Mitch but I still think of him as a kid not much older than me. I had no idea
he was 74. Age creeps up on one.

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hazeii
As a kid I remember playing with the logistic map (possibly pointed at it by
Dawkins?) following Robert May and Verhulst explanations of population
dynamics. Feigenbaum's constant(s) seemed to point a way through the chaos
(this at a time when plotting the mandelbrot set - slowly - was all the rage).

[0][https://en.wikipedia.org/wiki/Logistic_map](https://en.wikipedia.org/wiki/Logistic_map)

[1]
[https://en.wikipedia.org/wiki/Feigenbaum_constants](https://en.wikipedia.org/wiki/Feigenbaum_constants)

With modern computers and software this stuff should be so much easier.

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phkahler
Has anyone found insight into where those two constants come from after all
this time? That always seemed like an important question to me.

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kkylin
One of Feigenbaum's best known contributions to the subject is a heuristic
theory, based on renormalization group ideas borrowed from statistical
mechanics, that explains the period doubling cascade and lets one calculate
these constants. The first mathematically rigorous computer-assisted proof was
due to Oscar Lanford. I think now there are proofs that are not computer
assisted, though I'm not as familiar with these developments.

The Wikipedia article linked above links to some of this information. The
following article has a slightly more technical summary together with
references to many of the original papers (including Feigenbaum's):

[http://www.scholarpedia.org/article/Period_doubling](http://www.scholarpedia.org/article/Period_doubling)

For those of you with a bit more matheamtical background and access to
technical books, I like the summary of Feigenbaum's renormalization picture in
Guckenheimer & Holmes.

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chicob
I spent some good times exploring deterministic chaos.

Mathematica had sound outputs for the logistic map. I remember one could
distinctly hear the octaves progression, then noise, then a fifth. I remember
making a video overlapping the sound and the cobweb plot to "see" what I was
hearing.

Instead of studying calculus, I fell for the trap of trying neverending,
eardrum busting, iteratibly non-converging functions.

My study method was pretty chaotic.

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misil
If you're interested in Feigenbaum's constant, check out Numberphile's video
about it:
[https://www.youtube.com/watch?v=ETrYE4MdoLQ](https://www.youtube.com/watch?v=ETrYE4MdoLQ).

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eridius
I learned about that function and the resulting output back in high school,
but haven't looked at it since then.

I wish he'd have given at least the beginnings of an explanation as to why you
can't go over 4 for lambda though. What happens?

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matthewfelgate
He would still be alive today if wasn't for that damn butterfly....

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ChrisArchitect
too soooon haha

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tomahunt
The story of Feigenbaum presented in Gleik's Chaos is the reason I chose to do
physics.

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mycall
Chaos Monkey is sad.

