Thread by @Albertotufaile

On May 3, starting at 2:00 p.m., we will present the seminar at
Department of Atmospheric Sciences - Institute of Astronomy and Geophysics / University of São Paulo:

"From the Parlaseric Circle to the Jumping Laser Dogs"

By: Profa. Dr. Adriana Pedrosa Biscaia Tufaile and Prof. Dr. Alberto Tufaile - Laboratory of Soft Matter - School of Arts Sciences and Humanities of USP.

Basically, we will explain how phenomena of atmospheric optics have inspired us to do some experiments on optics and soft matter.

We've started our studies with light in foams.

With this study, developed the hyperbolic prism.

Thinking about reflection, light traveling in foams presents some properties of dynamical systems, and we've tha the hyperbolic prism acts like kaleidoscope.

(a) Plot of light reflection and refraction in a hyperbolic prism. The experiment in (b), (c) and (d).

We have used a gemetric optics approach, and we concluded this:

We just used part of optics in this study, the geometric optics, because we were using the approach of dynamical systems, we are "Chaos Theory" lovers. We have found others apsect of Chaos during this work, and...

... a short period of analysis (3 years!!!) we published our findings: "Some aspects of image processing using foams" with one of our colleagues, M. V. Freire.

We observed how light travels inside the foam. We proposed the combination of two main processes of the light transport
in foams: a diffusive one related to Gaussian function, and another
one related to a chaotic dynamics, similar to those observed in a
chaotic saddle...

... similar to those observed in a chaotic saddle, in which a ray of light bounces back and forth for a certain time in the scattering region, and leaves it through one of the several exits. This type of problem is common in astronomy and atoms.

Chaotic saddle is related to transient chaos. Yes, like some moments in your life,
the chaos appears in your life, leaving everything upside down and then disappears, like that stupid "crush" you experienced. This is transient chaos, folks. Chaos is everywhere, because...

Using chaos, you can see things better! Strange, isn't it?

Buuut, we started to study wave optics in foams: "Another topic addressed in our study was the presence of caustics obtained from the light scattered in foams,
with typical patterns observed in diffraction of light by transparent thin films".

Maybe you already know, but we have to live in edge of chaos: Even though the idea of the edge of chaos is abstract and unintuitive, it has many applications in such fields as ecology, business management, psychology, political science, and other domains of the social science.

Physicists have shown that adaptation to the edge of chaos occurs in almost all systems with feedback: en.wikipedia.org/wiki/Edge_of_c…

We started to observe wave optics in foams!

... and we have found the Parlaseric Circle and laser dogs when a laser beam travels in foams. Adriana decided to give these names to these patterns. sciencemag.org/news/2015/02/r…

These patterns put us in a state of "cognitive conflict": Cognitive conflict is the discomfort one feels when our beliefs, values or behaviors contradict one another. Why? Because the light was behaving like a wave and a ray at same time, in an experiment of classical physics!

The theory for this case should be "The Geometrical Theory of Diffraction". This theory is commonly used for radar systems, not for light in foams. Nobody used this theory for this case.

In this graph, we show that for a single incident ray, longitudinally, light behaves as a ray (angle of incidence equal to that of the angle of exit), axially the light is behaving like a wave (diffraction).

This parhelic-like circle, or parlaseric circle, will appears when light hits a Plateau border obliquely. Joseph Plateu discover the laws of the architeture of foams, and love optics, he was one of the first people to demonstrate the illusion of a moving image.

And what is a parhelic circle? "A parhelic circle is a halo, an optical phenomenon appearing as a horizontal white line on the same altitude as the sun, or occasionally the Moon. If complete, it stretches all around the sky, but more commonly it only appears in sections."

The parhelic circle is different from a common sun halo (22 degrees halo): 1) The parhelic circle always crosses the sun. 2) The parhelic circle is mainly white. And sometimes, you can see sundogs at parhelic circle

Someone could ask: "why the parhelic circle is different from the 22 degrees halo?" Because they are created by different physical principles, kids. The 22 degrees halo is based in reffraction law, while the parhelic circle is based in diffraction, with multiple interference.

and #sundogs, what is sundog? Well, it seems that this name came from oral tradition of the vikings. Odin is the sun, and he has some dogs. But we cannot verify historicaly this information, the vikings did not write about this.

It is very common to observe colors in sundogs, copies of the sun, with a color separation that looks like a rainbow. These are strong evidences that we are seeing reflection and refraction of light, phenomena of geometric optics.

There are other types of phenomena, like the subsun.

With a laser pointer and soap bubbles, you can make your parlaseric circ with laser dogs!

This is a video about this research

Ok, and jumping sundogs? What are jumping sundogs? slate.com/technology/201…

To create an analog of jumping sundogs, I followed a suggestion of Phil Plait @BadAstronomer

And in our analogy, we have used needles of ferrofluids instead ice crystals needles. In our case, we control the jumps with magnetic fields, instead of electric fields in the case of the clouds scirp.org/journal/PaperI…

Ferrocell and light diffraction.

Using a green laser: In (a) laser dog and laser spot. (b) applying a magnetic field of B = 200 gauss, and in (c) applying 600 gauss.

Let's explain what you have in a cloud: The process of ice crystal formation in (a). In (b) there is a diagram of the multiple light scattering in the ice crystals. In (c) the ice crystal dynamics.

In this image you can see light diffracting multiple times in the tiny ice crystals, this is the reason why the parhelic circle is white, and not colored, like the refraction in ice crystals forming the sun halo.

You can consider some clouds in the sky as complex fluids! researchgate.net/publication/32…

Take a look at this video of a jumping sundogs made by some bykers

Another video of jumping sundogs, this time in Russia

This is a video of a Nasa rocket destroying a sundog! This rocket put in the space a satelite to study the sun, the SDO mission (Sun Dynamical Observatory). You can see the amazing shocking waves.

The oficial page of NASA about the sundog mystery nasa.gov/mission_pages/…

The physics of sundogs is ruled by the geometric optics, while the parhelic circle is related to diffraction.

This is a sundog and parhelic circle that I saw at my home!

Now, lets talking about the Glory Effect

The Glory Effect is an interesting case of atmospheric optics, I saw it two times whe then airplane was taking off.

The Glory effect is related to surface waves and classical light tunneling.

There is an analogy between the Glory effect aand the light scattering in Reuleaux bubbles

another image of a Reuleaux bubble

This name is due to the Reuleaux triangle

The interference of surface waves and the eye o Horus!

Parhelic circle receives the honorable Mention in Photo contest OSA

Rainbows

Red Rainbow

Cusped wave front

Creating rainbows with a glass cylinder and laser.

Cylindrical shell

Light scattering in a cylinder

"So many cartesian rays, so little time, what can I do?": Folding catastrophe, involute and cartesian rays.

Again, we have the ecounter of waves and rays: supernumerary bows.

OMG, another award with the Spiral Bow!

"I'm the sun, I'm the light, I'm the dark, I'm the dawn..." Flèche Love - Umusuna