Pendulum Waves (2010)

madelinw 7 years ago |

I recreated this in CSS/JS a few years ago, inspired by this video.

https://codepen.io/madelinw/details/ocnCl

abecedarius 7 years ago | |

Same principle, though not a physical simulation: http://wry.me/hacking/moire-eel.html

By moving the mouse you can amuse yourself with various Moiré effects.

ubershmekel 7 years ago | |

I made it with webgl: http://toplessproductions.com/pendulum/

murkle 7 years ago | |

2D View from above (in GeoGebra)

https://www.geogebra.org/m/yCe42MAX

aethr 7 years ago |

Without analyzing it too much this seems to be a perfect visualization of the mathematics of music theory. The lengths of string become quite a direct metaphor for the wavelengths of notes on the music scale, and seeing them move together in progressively different "groups" of notes I imagine closely matches traditional chord structures in different keys.

Quite mesmerizing, and mathematically satisfying at the same time!

mrob 7 years ago | |

It's a closer analogy to the "beat frequencies" you get with constructive and destructive interference of waves of similar frequency. The envelope of the total amplitude of the pendulums oscillates with lower frequency than the amplitude of any individual pendulum.

I used Audacity to mix sine waves of the frequencies of the pendulums (51/60Hz, 52/60Hz, ..., 65/60Hz), multiplied by 440 to get them to audio frequency, and it sounds a lot like the UFO sound effect from the 1970s TV series "UFO".

hrayr 7 years ago | | |

I'm very curious how that sounds, would you mind posting it somwhere?

mrob 7 years ago | | |

Posting on first Google result for "share short sound clip". I can put it somewhere else if you have a better suggestion.

https://clyp.it/rfu2x1kb

avip 7 years ago | |

For this analogy to hold you'd need the 8th ball thread x4 longer than the first, which is very far from the actual ratios used.

jkqwzsoo 7 years ago | |

Less the notes and scales themselves, and more polyrhythms and phasing. This reminded me of Steve Reich's Clapping Music, and similar phasing-heavy works (Piano Phase, Drumming, Music for Pieces of Wood, 6 Pianos/Marimbas, and Pendulum Music).

agumonkey 7 years ago | | |

amazing, I need to read that book, any other suggestions ?

also https://news.ycombinator.com/item?id=18696782

jkqwzsoo 7 years ago | | |

Read that book??

agumonkey 7 years ago | | |

The book you listed seems super interesting.

agumonkey 7 years ago | |

jazz is variable actuators/pendulums

aardvark291 7 years ago |

If you enjoy demos like this and live in or visit San Francisco, check out the Exploratorium, which is full of amazing physical demos like this.

https://www.exploratorium.edu/

kaycebasques 7 years ago | |

They have “adult swim” on Thursday nights. I.e. adults only, and alcohol for sale. Classic first date spot. But to really make the most of it you’ve got to go by yourself and spend a day there, taking the time to appreciate and think about each exhibit.

I have fond memories of field trips to the Exploratorium back when it was at the Palace of Fine Arts.

todd8 7 years ago |

I’ve seen this demonstration at least a couple of times, once as an undergrad around 1971. I always remembered it and a few years later I was working with a minicomputer with limited I/O so I decided to blink the row of front panel lights just to show that the program was running. I blinked each on and off with a slightly different frequency and got a similar, interesting effect.

inutard 7 years ago |

Great to see this come up again! Here's a simulator I wrote for it a looooong (almost 8 years!) ago: https://cs.stanford.edu/people/paulliu/webapps/pendulum.html

ms013 7 years ago |

Interesting to see this come up again. Here’s a small model for this system written in Haskell from a few years back:

http://syntacticsalt.com/blog/2011-08-27-harmonic-motion.htm...

kaycebasques 7 years ago |

It seems like the pendulums fall into a few repeating patterns. E.g. for a second it looks like a snake, for another second it looks like a double helix, and so on. The whole set cycles through each pattern and then begins again. How many patterns are there?

dest 7 years ago |

Now what happens when you couple the oscillators?

kaffeemitsahne 7 years ago | |

https://www.youtube.com/watch?v=5v5eBf2KwF8

Something like this?

dest 7 years ago | | |

yes, but I am looking for coupling between oscillators of different fundamental frequencies.

the_cat_kittles 7 years ago |

it looks like rotating helixes to my eye