# The butterfly effect **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 24, 2017, 10:30am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543 "2017-08-24T10:30:01Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [August 24, 2017, 7:58pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/21 "2017-08-24T19:58:05Z")
> [@Velocity](#): > > The butterfly effect is best understood backwards, not forwards: Most small things won’t have big repercussions later on. But many big things can be traced back to, or affected by, one small thing. > > The best example might be the famous poem, “For Want of a Horseshoe Nail.” > \* > For want of a horseshoe nail, the horse was lost. > For want of a horse, the rider was lost. > For want of a rider, the message was lost. > For want of a message, the battle was lost. > For want of a battle, the war was lost. > For want of a war, the kingdom was lost. > And all for the want of a horseshoe nail.\* That’s similar to the Black Mirror (Netflix) episode “Nosedive” where Bryce Dallas Howard’s character lives in a society largely driven by social ratings. She’s so close to getting the 4.x/5.0 rating she needs to get the discount that would let her live in some idyllic gated community and her invite to be her long time BFF’s maid of honor is just the push she needs. But due to an unfortunate mishap, one thing leads to another and her rating spirals to oblivion. I think these are more examples of a “cascading failure” than a “butterfly effect”. BE is more about chaos theory and small, seemingly random changes having disproportionately large influences. A CF is more a chain reaction caused by complex interconnected systems with such tight tolerances that a small failure causes one system to collapse, which caused another and so on until catastrophe. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [August 25, 2017, 3:31am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/22 "2017-08-25T03:31:38Z")
> [@silenus](#): > > Yes, yes it is. So think carefully about\*\* every single decision\*\* you make! Make any decision you want, thoughtfully or otherwise. Because one interpretation of Quantum Theory holds that, with _every “decision” made in the universe_ (for some all-expansive definition of “decision”), multiple universes are immediately spawned, one for every possible choice for that decision, in each of which a different choice for that decision having been made. Even dying or not dying (a “decision” under the all-expansive definition of “decision”) spawns at least two universes, one in which you die and one in which you live. This is the well-known Theory of [Quantum Immortality](https://en.wikipedia.org/wiki/Quantum_suicide_and_immortality). Now excuse me while I go skydiving without my parachute and alter the history of all the worlds. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [August 25, 2017, 10:09am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/23 "2017-08-25T10:09:59Z")
I think some here are going by the popular understanding of what (this part of) chaos theory means: that small events can sometimes be the trigger of, or catalyst for, larger events. But if that’s all that we meant by a chaotic system, then it would hardly be new information to humans: we’ve essentially always known that; certainly since the discovery of fire. The problem is with the word “cause” in the butterfly metaphor. Most people take it to mean some sort of 1 to 1 correspondance between the butterfly and the tornado. If we go back to the simulation that inspired the metaphor, we can see what was intended. Basically Lorenz found that _any change at all_, no matter how small, in one of the input variables to his system, would _eventually_ lead to a different result set. Plugging in 10.0 vs 10.00000001 would eventually, after running the simulation for a while, give completely different results. So, in the metaphor, the butterfly is representing “any change at all”, and the tornado is part of the “different result set”. Bearing this in mind we can say: 1. The statement about the butterfly is essentially true about any part of the system. Every butterfly, every movement, will eventually result in a different result set, if the world’s weather runs for long enough. 2. We don’t need to imagine a special “rube goldberg” set of events connecting the butterfly to the tornado. 3. If we’re really going to say the butterfly “caused” the tornado, then to be consistent we’d have to say all weather after that date, for the rest of time was also caused by the butterfly. ---
**Author:** ![pullin](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@pullin](https://boards.straightdope.com/u/pullin)\ **Post date:** [August 25, 2017, 10:12am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/24 "2017-08-25T10:12:44Z")
> [@anomalous1](#): > > :eek: To think of it in that way means you could also have been responsible for people’s death as well, say decided to grab your soda in the car and you look down once the light turns green, that one second delay could turn into the person behind you in traffic just slightly getting through a yellow light through an intersection and getting hit by a truck. If you just didn’t drink your pop, they’d be alive. I spent a lot of time thinking about this 2 Christmases ago. While driving cross-country to visit relatives, I stopped to buy a burger and soda. A few minutes after returning to the highway an 18-wheel tanker truck lost control, rolled over, and swept thru my lane taking out the car behind me. I wondered where I would be had the attendant been slightly slower getting my meal. The difference between myself and the unfortunate car was literally seconds. Even more bizarre, the next Christmas my cousin was killed on the same road\* – in a crash with a tanker truck. \*over 100 miles away, but on the same highway, traveling for the same reasons. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 25, 2017, 12:23pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/25 "2017-08-25T12:23:43Z")
Interesting aside – “Butterfly effect” seems to derive from two very different and independent origins, both referring to the way that infinitesimal causes can lead to significant (and unpredictable) outcomes. One , which I think is the real origin of the term, is due to mathematician and meteorologist Edward Lorenz, who observed that small changes in the initial conditions in weather calculations lead to large and unpredictable changes in the outcome (the story is told in several place, most notably in James Gleick’s popular book **Chaos** ). Lorenz in 1963 attributed the analogy of small changes in input being like changing the movement of air due to the flapping of a seagull’s wings (although, interestingly, he attributed this statement to another, unnamed meteorologist). Later, according to Wikipedia > [@](#): > > Following suggestions from colleagues, in later speeches and papers Lorenz used the more poetic butterfly. According to Lorenz, when he failed to provide a title for a talk he was to present at the 139th meeting of the American Association for the Advancement of Science in 1972, Philip Merilees concocted Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas? as a title.[13] Although a butterfly flapping its wings has remained constant in the expression of this concept, the location of the butterfly, the consequences, and the location of the consequences have varied widely.[14] > **[Butterfly effect](https://en.wikipedia.org/wiki/Butterfly_effect)** > > In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state. > The term is closely associated with the work of mathematician and meteorologist Edward Norton Lorenz. He noted that the butterfly effect is derived from the metaphorical example of the details of a tornado (the exact time of formation, the exact path taken) being influenced by minor pertu... The other origin is from Ray Bradbury’s 1952 time-travel story **the Sound of Thunder** , in which a time traveler stepping on and killing a butterfly causes some weird changes when he gets back to the present. (Words are spelled differently, and his favored candidate lost, rather than won, an election). I suspect that most people think of the Bradbury story rather than the Lorenz analogy, or even its pithy statement form. Actually, most people probably don’t think about the origin at all. The idea is clear enough, although Boston Globe writer Peter Dizikes claims most people get it wrongh, anyway: > [@](#): > > The journalist Peter Dizikes, writing in The Boston Globe in 2008, notes that popular culture likes the idea of the butterfly effect, but gets it wrong. Whereas Lorenz suggested correctly with his butterfly metaphor that predictability “is inherently limited”, popular culture supposes that each event can be explained by finding the small reasons that caused it. Dizikes explains: “It speaks to our larger expectation that the world should be comprehensible – that everything happens for a reason, and that we can pinpoint all those reasons, however small they may be. But nature itself defies this expectation.”[32] There’s arguably yet another link between butterflies and the effect – plotting a Lorenz Attractor’s trajectories on a computer, the resulting form can look like butterfly’s wings, but this can’t be responsible for the metaphor. The real significance, as pointed out in Gleick’s book, is that tiny change in initial conditions surprisingly eventually result in huge and unpredictable changes in outcome. Lorenz left off a few decimal places in the numbers he fed in to his computer, thinking it wouldn’t make a significant difference. It did, which was a shock. It ultimately doomed the 1950s hopes of man-made weather control. as for Bradbury’s story, it touched a nerve, but it also rubbed people the wrong way. It always bugged me not that the changes Bradbury’s characters observed were unpredictable, but that they were so small and specific to the character’s life. A Lorenz-style change would’ve been more overwhelming, like causing Rome not to be founded, or humans not developing, or even mammals being wiped out. Bradbury’s dinosaur-hunting story bothered hard SF writer L. Sprague de Camp that he wrote his OWN dinosaur-hunting story, _A Gun for Dinosaur_, in which his engineering instincts were better satisfied. Like _A Sound of Thunder_, it’s considered a classic. ---
**Author:** ![GreenWyvern](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/greenwyvern/32/2834_2.png) [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)\ **Post date:** [August 25, 2017, 12:38pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/26 "2017-08-25T12:38:56Z")
See Blackadder Back & Forth Blackadder travels backwards and forwards in time making small changes. 😃 ---
**Author:** ![Gatopescado](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gatopescado/32/5711_2.png) [@Gatopescado](https://boards.straightdope.com/u/Gatopescado)\ **Post date:** [August 25, 2017, 5:17pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/27 "2017-08-25T17:17:54Z")
It’s _ALL YOUR FAULT_, **protoboard**. :mad: Damn you! ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 25, 2017, 6:23pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/28 "2017-08-25T18:23:51Z")
> [@CalMeacham](#): > > Interesting aside – “Butterfly effect” seems to derive from two very different and independent origins, both referring to the way that infinitesimal causes can lead to significant (and unpredictable) outcomes. > > One , which I think is the real origin of the term, is due to mathematician and meteorologist Edward Lorenz, who observed that small changes in the initial conditions in weather calculations lead to large and unpredictable changes in the outcome (the story is told in several place, most notably in James Gleick’s popular book **Chaos** ). Lorenz in 1963 attributed the analogy of small changes in input being like changing the movement of air due to the flapping of a seagull’s wings (although, interestingly, he attributed this statement to another, unnamed meteorologist). Later, according to Wikipedia > > [Butterfly effect - Wikipedia](https://en.wikipedia.org/wiki/Butterfly_effect) > > The other origin is from Ray Bradbury’s 1952 time-travel story **the Sound of Thunder** , in which a time traveler stepping on and killing a butterfly causes some weird changes when he gets back to the present. (Words are spelled differently, and his favored candidate lost, rather than won, an election). I suspect that most people think of the Bradbury story rather than the Lorenz analogy, or even its pithy statement form. > > Actually, most people probably don’t think about the origin at all. The idea is clear enough, although Boston Globe writer Peter Dizikes claims most people get it wrongh, anyway: > > There’s arguably yet another link between butterflies and the effect – plotting a Lorenz Attractor’s trajectories on a computer, the resulting form can look like butterfly’s wings, but this can’t be responsible for the metaphor. > The real significance, as pointed out in Gleick’s book, is that tiny change in initial conditions surprisingly eventually result in huge and unpredictable changes in outcome. Lorenz left off a few decimal places in the numbers he fed in to his computer, thinking it wouldn’t make a significant difference. It did, which was a shock. It ultimately doomed the 1950s hopes of man-made weather control. > > as for Bradbury’s story, it touched a nerve, but it also rubbed people the wrong way. It always bugged me not that the changes Bradbury’s characters observed were unpredictable, but that they were so small and specific to the character’s life. A Lorenz-style change would’ve been more overwhelming, like causing Rome not to be founded, or humans not developing, or even mammals being wiped out. Bradbury’s dinosaur-hunting story bothered hard SF writer L. Sprague de Camp that he wrote his OWN dinosaur-hunting story, _A Gun for Dinosaur_, in which his engineering instincts were better satisfied. Like _A Sound of Thunder_, it’s considered a classic. No, I just think of Ashton Kutcher. (kidding) ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 25, 2017, 7:45pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/29 "2017-08-25T19:45:09Z")
> [@cmyk](#): > > No, I just think of Ashton Kutcher. > > (kidding) I try not to. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [August 25, 2017, 11:13pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/30 "2017-08-25T23:13:04Z")
> [@protoboard](#): > > Is it likely that my mundane actions, such as buying cigarettes or going to the mall is drastically changing the course of history? Just think what could have happened to you if your mother had asked your father, at an inopportune time, if he had remembered to wind the clock. ---
**Author:** ![GreenWyvern](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/greenwyvern/32/2834_2.png) [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)\ **Post date:** [August 26, 2017, 5:46am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/31 "2017-08-26T05:46:24Z")
> [@Yllaria](#): > > Just think what could have happened to you if your mother had asked your father, at an inopportune time, if he had remembered to wind the clock. I’m also a fan of Tristram Shandy! 🙂 ---
**Author:** ![Gretchion](https://avatars.discourse-cdn.com/v4/letter/g/8edcca/32.png) [@Gretchion](https://boards.straightdope.com/u/Gretchion)\ **Post date:** [August 27, 2017, 3:14am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/32 "2017-08-27T03:14:01Z")
> [@clairobscur](#): > > Think of the sperm. We’re the result of a specific spermatozoid amongst millions entering an egg. I assume that the slighest change (say, a different step while walking) in the day or probably even week of your father (and probably mother too) would have resulted in someone else (or nobody at all) being born. And this very slight change can be result, direct, secondary or tertiary, etc… of another slight change in someone else behaviour. > > You go to the mall, slightly affect the movements of a large number (hundreds? thousands?) of shoppers and drivers. If any of these hundreds or thousands of people beget a child during the following week, it will be a different child from the one who would be born if you had decided not to go to the mall. > > So, you removed someone from the gene pool and added someone else. And even if these people don’t reproduce in turn, their mere existence will change the life, in important or in small ways, of a very large number of people. For the next 80 years or so. Again, even if they’re extraordinarily discreet and don’t reproduce, by just being there, they too will change who gets to be born. > > And that’s cumulative. I suspect that after these 80 years, you would have a significant part of your country population who will be different people from those who would have lived if you have chosen not to go to the mall. From there, the history of the world has changed (and the changes will become larger and larger with time) because you went to the mall. > [@clairobscur](#): > > All of us are the result of a single sperm cell amongst millions entering an egg. The slighest change (like, say, making a different step while walking) in the life of your father (and probably even mother) during the week before you were conceived (and possibly even earlier than a week) would have resulted in someone else being born rather than you. > > You go the mall, affect on your way the moves and actions of presumably hundreds if not thousands of drivers and shoppers, which might in turn change slightly the behavior and moves of multiple other people. If any of these numerous people soon become a parent, his child will be a different person. > > Even assuming that this person is very quiet and doesn’t reproduce, over the course of his life, he will affect in very small or very large ways the life of countless people. Which will affect the life of even more people. Including wrt this sperm thing and having people born who wouldn’t otherwise be born. And they in turn…When he will die after, say, 80 years, a non trivial part of your country population will be people who wouldn’t have been born if you hadn’t decided to go to the mall. A couple more generation, and I suspect that the whole world population will owe its life to your visit to the mall. Is this an example of two similar but slightly diverging timelines? ---
**Author:** ![igor\_frankensteen](https://avatars.discourse-cdn.com/v4/letter/i/839c29/32.png) [@igor\_frankensteen](https://boards.straightdope.com/u/igor_frankensteen)\ **Post date:** [August 27, 2017, 3:44pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/33 "2017-08-27T15:44:16Z")
> [@protoboard](#): > > Is it likely that my mundane actions, such as buying cigarettes or going to the mall is drastically changing the course of history? NO. Nothing that you do is changing the course of history at all, ever (unless you are one of those people who popularizes lies about the past). It MIGHT be altering the probabilities of the future, however. I know you are using the slang phrase “altering history” to MEAN affecting the future in a way that is out of proportion to the act itself. I think there are two main things to recognize in this overall consideration/discussion subject: 1. Yes, the actions of one butterfly in The Philippines can be the trigger for much larger events down the timeline. But there is more than one butterfly in The Philippines. So figuring out which exact one to pin the eventual tornado on is a bit tricky. 2. Recognizing that small acts can have larger results is important, however, turning that recognition into an actionable life plan, or decision engine, is, shall we say, rather a dicey trick. After all, if you do get caught up in considerations of causality, you might suddenly find yourself pausing, rather than waving away the awful smell that just came out of your own tukas. After all, if a butterfly can cause a tornado, your waving might be triggering a typhoon. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 27, 2017, 4:33pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/34 "2017-08-27T16:33:42Z")
> [@Darren\_Garrison](#): > > Mundane actions _can_ have large effects, but that isn’t to say that mundane actions _always_ have large effects. Probably the vast majority of the time, mundane actions have mundane effects. This! The loss of most horseshoes results in no great historical change at all. However, the loss of a horseshoe could result in the loss of the kingdom. We have absolutely no way of knowing in advance which case is going to apply. (So…don’t skimp on horseshoes.) ---
**Author:** ![Lamia](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lamia](https://boards.straightdope.com/u/Lamia)\ **Post date:** [August 27, 2017, 4:35pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/35 "2017-08-27T16:35:55Z")
> [@CalMeacham](#): > > The other origin is from Ray Bradbury’s 1952 time-travel story **the Sound of Thunder** , in which a time traveler stepping on and killing a butterfly causes some weird changes when he gets back to the present. (Words are spelled differently, and his favored candidate lost, rather than won, an election). I suspect that most people think of the Bradbury story rather than the Lorenz analogy, or even its pithy statement form. > > […] > > as for Bradbury’s story, it touched a nerve, but it also rubbed people the wrong way. It always bugged me not that the changes Bradbury’s characters observed were unpredictable, but that they were so small and specific to the character’s life. A Lorenz-style change would’ve been more overwhelming, like causing Rome not to be founded, or humans not developing, or even mammals being wiped out. It’s been years since I read “A Sound of Thunder”, but it’s my recollection that the changes were not as trivial as you’re making them out to be. While they were nowhere near as drastic as mammals being wiped out, the guy who got elected in the altered timeline was basically the next Hitler. I remember having the impression that in this altered timeline humanity in general was more brutish, although I can’t recall if there was something other than the changed spelling (which would be a pretty trivial difference) that made me think this. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 28, 2017, 3:23am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/36 "2017-08-28T03:23:38Z")
Okay. Whichever butterfly flapped its wings and caused hurricane Harvey is in BIG trouble… ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [August 28, 2017, 9:17am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/37 "2017-08-28T09:17:01Z")
> [@igor\_frankensteen](#): > > 1. Yes, the actions of one butterfly in The Philippines can be the trigger for much larger events down the timeline. But there is more than one butterfly in The Philippines. So figuring out which exact one to pin the eventual tornado on is a bit tricky. I think you are making the fundamental misunderstanding of chaos theory that I was talking about upthread. While it may be true that removing that butterfly from the system would have meant no tornado, there is no one-to-one correspondence between the butterfly and the tornado. The butterfly is not solely resposible for the tornado; the whole system is. > [@](#): > > 1. Recognizing that small acts can have larger results is important, however, turning that recognition into an actionable life plan, or decision engine, is, shall we say, rather a dicey trick. Absolutely. There is no way you could predict perfectly the long-term chaotic effect of some minute change to a system. > [@Trinopus](#): > > This! The loss of most horseshoes results in no great historical change at all. However, the loss of a horseshoe could result in the loss of the kingdom. Again, this is the popular understanding of chaos theory – that small changes _might_ result in a big change somewhere down the line. But that’s not actually what this part of chaos theory is saying at all (and, if that’s all it were saying, would hardly be news for mankind: we’ve always known that). It’s saying that some systems are super-sensitive to initial conditions, such that _any_ change, no matter how small, will eventually result in large-scale changes. “Eventually” is completely unbounded though, so in a sense the second part of your sentence is right for the wrong reason: Maybe only one horseshoe will result in this kingdom being lost. However it’s false to say all the rest will not cause great changes. Or at least not consistent with our current understanding of chaotic systems. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 28, 2017, 11:49am UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/38 "2017-08-28T11:49:40Z")
> [@Lamia](#): > > It’s been years since I read “A Sound of Thunder”, but it’s my recollection that the changes were not as trivial as you’re making them out to be. While they were nowhere near as drastic as mammals being wiped out, the guy who got elected in the altered timeline was basically the next Hitler. I remember having the impression that in this altered timeline humanity in general was more brutish, although I can’t recall if there was something other than the changed spelling (which would be a pretty trivial difference) that made me think this. Considering what could have been the case, one guy rather than another winning an election (even if he turns out to be a monster) , along with some spelling changes, still counts as pretty damned trivial in my book. ---
**Author:** ![Annie-Xmas](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)\ **Post date:** [August 28, 2017, 1:38pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/39 "2017-08-28T13:38:18Z")
I read a book adaption of Back to the Future where Marty asks Doc Brown is his spending fifty cents to see a movie could alter the future Doc explains: Say that 50 cents put the years gross from $990.75 to $1,000.25. The four figure gross has the movie theater owner deciding to keep it open instead of closing the theater. Two years later a boy who would be President goes to see a movie there, and is killed in a fire in the theater. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 28, 2017, 11:35pm UTC](https://boards.straightdope.com/t/the-butterfly-effect/794543/40 "2017-08-28T23:35:24Z")
> [@Mijin](#): > > . . . this is the popular understanding of chaos theory – that small changes _might_ result in a big change somewhere down the line. But that’s not actually what this part of chaos theory is saying at all (and, if that’s all it were saying, would hardly be news for mankind: we’ve always known that). > It’s saying that some systems are super-sensitive to initial conditions, such that _any_ change, no matter how small, will eventually result in large-scale changes. . . . ??? I’m not seeing the difference. The “might” applies to whether or not a given environment has the property of super-sensitivity. The horseshoe analogy only works if the entire situation is on a cusp (a bunch of 'em!) Without that environment in place, the loss of a horseshoe isn’t going to make much difference, and there isn’t any way that it “might.” The battle has to be a close thing, by itself, for a small difference to tilt it. I may be mistaken, but has anyone actually claimed that every butterfly wing-flap causes vast changes in the weather? Or, perhaps conversely, is anyone claiming that every big weather event was caused by some tiny disturbance? If they are, I certainly don’t agree with them. If that were the case, wouldn’t perceived reality be more…chaotic? Wouldn’t it be much harder to discern ordinary cause and effect? [Previous page](https://boards.straightdope.com/t/the-butterfly-effect/794543.md?page=1) [Next page](https://boards.straightdope.com/t/the-butterfly-effect/794543.md?page=3)