What am I seeing?
July 3, 2014 8:16 AM   Subscribe

Holding a mug close to my face, there is an interesting effect. It's not like other things and I can't duplicate it with other objects.

While pressing a ceramic coffee mug against my face this morning I noticed something interesting. Hold anything close up to your nose, shift your focus, and you get a neat optical effect, but this is different.

It became obvious after a second that the green "on" light of my speakers is being reflected, but depending on the position of my head, the light changes in interesting ways. Its ranges from a short thin line to a bold dot, but is never solid. I can see something like filaments that are still when I am still but seem to move in parallax as I pan left or right.

It doesn't work with a clear bottle or a flat white one. So far just the mug which is tall but otherwise ordinary.

Is it just a really close look at the surface of the mug? Tiny cracks in the glaze? I am really curious. I checked carefully to make sure no hairs or lashes or brows are getting in the way. My vision is great and I don't do drugs. It's hard to say whether I'm focusing close or far away though. The details depend on the focus though, like with Magic Eye if you remember those.

I'm really curious what this is so if you have insights, thanks in advance.
posted by rahnefan to Science & Nature (5 answers total) 1 user marked this as a favorite
Could be an interference pattern arising from the fact that the inner and outer surfaces of the mug's thin transparent glaze are really close together.
posted by flabdablet at 8:31 AM on July 3, 2014 [1 favorite]

The presence of scratches on a surface can produce a cool holographic effect that appears to move around as you move your head. Perhaps cracks or scratches in the glaze are replicating that effect?
posted by firesine at 8:33 AM on July 3, 2014 [1 favorite]

It's more like this http://cdn.phys.org/newman/gfx/news/hires/2012/wigglezconfi.png but the filaments run more or less left to right.
posted by rahnefan at 8:47 AM on July 3, 2014

With LED light, which most often emit a very narrow band of frequencies--for practical purposes a single frequency, aside from the tricks they have to do to get an approximation of white light--diffraction effects are often very pronounced and noticeable. Note for example the images here from slightly out of focus telescopes that are used by telescope users to accurately align the mirrors & lenses of the telescope. Note especially the one labeled 'aberration known as coma'.

My guess is you're seeing a combination of diffraction effects (which is a type of interference pattern as noted by flabablet above), combined with the curve of the mug, combined with maybe some distortion in the pattern because the mug isn't perfectly conical, combined with maybe some effects from regular scratches or ripples in the surface of the mug, combined with the fact that the LED is emitting a single wavelength of light that makes diffraction patterns etc very visible.

FYI if this is the case changing your focus will potentially change the shape & details of the pattern quite markedly.

FWIW I see diffraction patterns all the time nowadays, and most particularly with light sources like LEDS, but also with stars, street lights, etc, whereas before I learned about diffraction patterns in physics class I had no idea such things even existed and never noticed them.
posted by flug at 10:10 AM on July 3, 2014 [1 favorite]

BTW there are various techniques that make it possible to see the network of blood vessels within your eye. The 'filaments' you describe make me think that might be part of what you're seeing. This page shows four different techniques that allow you to do this and it is just possible you have stumbled on something similar by accident.
posted by flug at 10:33 AM on July 3, 2014 [2 favorites]

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