Learning about rheoscopic fluids

What is rheoscopic fluid? 

To learn about what rheoscopic fluid is, we need to learn about the word rheoscopic. Many scientific terms have greek or Latin roots, and those roots describe what we see. Here rheo- is the Greek root to talk about currents, streams, or flow. The latter half of rheoscopic, the -scopic, is the Greek root of an instrument for viewing. Thus rheoscopic fluid literally means current viewing, or current showing fluid.

What makes the rheoscopic fluid in my galaxy bottle shimmer? 

​You'll notice three of the four things you need to make your own rheoscopic fluid are pretty boring: water, coloring, and a bottle. The fourth ingredient is what gives rheoscopic fluid all of that shimmer and shine that you oogle at while adoring your pearly swirly calm down bottle: Mica.

Mica powder is a microscopic crystal that looks similar to a frosted flake (although much smoother on the top and bottom). When these tiny crystals are moving in the currents of the water they will naturally align themselves with the turbulence. That is, they will align themselves to look like flying UFOs instead of like flying walls which would have much more resistance. 

Light interacts with the Mica and reflects from its surfaces, although some of those surfaces are large and flat, while others are minuscule and line like. In this way, we see the Mica reflect a lot of light to our eyes in specific patterns as it tumbles from current to current in your galaxy bottle. 

Where can I see rheoscopic fluids in real life? 

Tiny crystal particles are used to make shampoo shimmer, and even some drinks look like galaxies. You'll also see these crystal powders decorating cakes and cookies, although this isn't in fluid form, but does add that extra shimmer!

What other science can I learn with my galaxy bottle?

​We took an in-depth look at what would happen if Earth stopped spinning. You can use your galaxy bottle to show how the mantle and the core would be ripped apart as the core (the rheostatic fluid) kept on spinning while the mantle (the bottle) stayed still.