Candle Flame Oscillations as a Clock
15 comments
·August 16, 2025NKosmatos
Mistletoe
I never thought it would be as regular as that graph and thought it was random. The world around us is so fascinating.
JKCalhoun
That is awesome. And I am so sad an individual that my first thought was of a software plug-in that would use this frequency to generate realistic candle-flicker effects.
alnwlsn
To continue this tangent, legend has it that some of those battery powered tea candle lights actually reuse the chip from cheap music playing trinkets. If you replace the yellow LED with a speaker, you might hear beepy christmas music or happy birthday.
I've never found one myself (most of them have a better candle simulation chip than that), but they are apparently out there.
cpldcpu
This was 10-15 years ago.
In between they used dedicated ASICS: https://cpldcpu.com/2013/12/08/hacking-a-candleflicker-led/
And more recently simply microcontrollers: https://cpldcpu.com/2024/01/14/revisiting-candle-flicker-led...
kridsdale1
Related to this, I once read that the reason nearly every car alarm in the 1990-2010 approx era had the same pattern of awful sound patterns was that they all simply used the same off the shelf sound IC which was produced in such quantities as to make any custom option untenable.
The “car alarm sequence” of 10s patterns was just the self-test demo program for the sound chip.
jkingsman
> Todays candles have been optimized for millenia not to flicker.
Where can I learn more about that? My google fu is failing me.
cpldcpu
The self-trimming wick is the trick. Before that was invented, people had to use special scissors to trim the wick and avoid uncontrollable large (and flickering) candle flames.
https://en.wikipedia.org/wiki/History_of_candle_making#Indus...
docsaintly
I have recently become quite fascinated with how much of what we use daily relies on the laws of physics always working the exact same way. This is a wonderful example of that.
efavdb
Very cool. I've always wondered what the shape of a flame is and how one could use physics to derive it. anyone have any leads for this?
kridsdale1
Look up some YouTube videos of candles or lighters used in zero-gravity. It’s a sphere.
The candle shape on earth is caused by the weight of the air.
cpldcpu
The third reference from the article provides some pointers (see also references there).
https://arxiv.org/pdf/1803.10400
But its not trivial at all, its a complex fluid dynamics problem. I stumbled upon all the "coupled candle oscillators" literature when I was looking for a shortcut to a semi-physical candle model. But there is no easy way out...
efavdb
Thank you! And appreciate the TLDR.
nh23423fefe
seems like a very complicated simulation problem. i'd be surprised if you could derive from first principles.
you need to model the atmosphere as environment, heat flow, wicking action, chemical reactions, fluid dynamics under gravity. Then model human perception to turn the spectral radiance into a perceived shape.
I was today years old when I learned that the frequency of a flicker candle flame is ~9.9Hz :-)