Soap Sheets

Here’s a new item for our category of soap bubble pictures.  The movie shows a science-centre-style demo, not of a bubble, but of a soap sheet.  It’s a way of showing patterns like the ones that appear on bubbles, but streaming down a huge sheet.  The quality of the movie is not great, so here’s a still photo that shows the effect.

I think this was originally a Victorian demonstration, but I don’t have chapter and verse for that.  It’s a demo you sometimes see in hands-on Science Centres, but often it’s not set up so that you can really see the colours.  For that there has to be a black background to the sheet, and a translucent screen, at an angle of forty five degrees to the sheet, brightly illuminating it.

I’m fascinated by patterns like these.  Just setting patterns in motion, as in many screen savers, doesn’t seem to me to produce effects that are as beautiful.  I don’t think it’s just the colours.  If we could characterise what makes these patterns special, might we then open up a whole new world of visual expression, using computer animation?  Or would we just end up with a small repertoire of pretty effects?

Fancy trying to set up your own soap sheet?  It’s not so hard.

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Sleights of Mind – illusions and magic

The dome in the left hand picture is an illusion!  It was painted on the ceiling of the Jesuit church in Vienna by Andrea Pozzo a bit over three hundred years ago. Seen from just the viewpoint of the photo on the left, it’s one of the classics of trompe l’oeil painting.  The right hand photo, looking the other way down the nave of the church, shows how Pozzo had to distort his painting of the dome, in order for the perspective illusion to work from a viewpoint near the high altar of the church, as in the left hand photo.   (Copyright might be asserted in these images.  Most of the images on this site are my own or out of copyright, and can freely be used for private, non-commercial purposes, but these are third party photos.  Apologies, I don’t know who took them).

I’m posting about this painting to draw attention to a fascinating recent book in which Pozzo is featured.  The effect of his paintings, especially in this church and in the Church of Sant’Ignazio in Rome, is almost magically illusionistic, and the book is about what conjuring and magic have to teach us about perception and the brain.  It’s by cognitive scientists Stephen Macknik, Susana Martinez-Conde, with science writer Sandra Blakeslee: Sleights of Mind: what the neuroscience of magic reveals about our brains. The connection between illusions and conjuring has intrigued many researchers, but this is a ground-breaking published study.

Macknik and Martinez-Conde (a married couple, each running a separate research lab) also founded the Best Illusion of the Year Competition, now in it’s seventh year.