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Science is just spiffy. July 22, 2017

Posted by lumps in Art, Ducks, Personal Experiences.

Hubby, after watching video: “I need a sand pendulum.”



1. Jimbro - July 22, 2017

Upscale Spirograph!

2. geoff - July 22, 2017

For those who care, these are Lissajous curves. We had to play with them as undergraduates. Here’s something I wrote in a comment almost 10 years ago, after seeing composmentis’s Simple Harmonic Movement post [kind of NSFW].

The figure eight pattern.

Technically known as a Lissajous pattern, where harmonic motion in one direction is superimposed with harmonic motion in an orthogonal direction. When one frequency is an integer multiple of the other, or especially if they are the same, we observe esthetically pleasing patterns such as that shown in the video data above.

In other words: nice orbits.

3. lauraw - July 22, 2017

Linky no worky, but I think I remember the gif you’re talking about, haha

4. geoff - July 22, 2017

I think I fixed the link.

5. lauraw - July 22, 2017

Everything else at that post disappeared but that one gif was spared? Hilarious.

6. Sobek - July 22, 2017

My son is building a sand pendulum right now.

7. Retired Geezer - July 23, 2017

I’m just guessing that there are 2 points of hanging, otherwise it would just go around in a circle.

8. lauraw - July 23, 2017

Hah, Sobek! Just a coincidence or did he see this and think it was cool too?

9. Sobek - July 23, 2017

Not a coincidence. He liked the video. We watched a few more videos afterwards to get some ideas on how to do it. It was too last night to go to the store for sand, so he tried corn meal. It didn’t work out very well, alas.

10. lauraw - July 23, 2017

Playground sand, or blast media. Masonry sand will clog.

11. Retired Geezer - July 23, 2017

what about sugar or salt?

12. lauraw - July 23, 2017

*slaps forehead*


13. lauraw - July 25, 2017

Another one with a gif of pendulum waves:

In the comments it says the effect is from having the balls on different-length strings.

More niftiness:

14. geoff - July 25, 2017

Here’s one for lw & Sobek:

15. Retired Geezer - July 25, 2017

Fun Factoid: Sobek could bench-press all those weights.

But seriously, how could that drawing machine start out barely moving and then get yuge?

Also, my Hovercraft is full of eels.

16. lauraw - July 25, 2017

I had never seen that one before, Geezer! Much thanks!

Here it is, with helpful Portuguese subtitles.

17. lauraw - July 25, 2017

That drawing machine is unsettling, somehow.

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