Pendulum Waves (2010) (opens in new tab)

(sciencedemonstrations.fas.harvard.edu)

119 pointskp257y ago24 comments

24 comments

madelinw7y ago

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

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

abecedarius7y 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.

ubershmekel7y ago

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

murkle7y ago

2D View from above (in GeoGebra)

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

aethr7y 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!

mrob7y 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".

hrayr7y ago

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

1 more reply

avip7y 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.

jkqwzsoo7y 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).

agumonkey7y ago

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

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

1 more reply

agumonkey7y ago

jazz is variable actuators/pendulums

aardvark2917y 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/

kaycebasques7y 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.

todd87y 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.

inutard7y 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

ms0137y 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...

kaycebasques7y 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?

dest7y ago

Now what happens when you couple the oscillators?

kaffeemitsahne7y ago

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

Something like this?

dest7y ago

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

the_cat_kittles7y ago

it looks like rotating helixes to my eye

j / k navigate · click thread line to collapse

24 comments

madelinw7y ago

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

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

abecedarius7y 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.

ubershmekel7y ago

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

murkle7y ago

2D View from above (in GeoGebra)

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

aethr7y ago

Quite mesmerizing, and mathematically satisfying at the same time!

mrob7y ago

hrayr7y ago

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

1 more reply

avip7y 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.

jkqwzsoo7y ago

agumonkey7y ago

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

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

1 more reply

agumonkey7y ago

jazz is variable actuators/pendulums

aardvark2917y 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/

kaycebasques7y ago

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

todd87y ago

inutard7y 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

ms0137y 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...

kaycebasques7y ago

dest7y ago

Now what happens when you couple the oscillators?

kaffeemitsahne7y ago

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

Something like this?

dest7y ago

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

the_cat_kittles7y ago

it looks like rotating helixes to my eye

j / k navigate · click thread line to collapse