Why can I see patterns in the water?
Normally, you can't see how the water is moving
inside a full jar of water. Water that's moving in one direction
looks the same as water that's moving in another direction. But
glycol stearate, the chemical that gives some liquid hand soaps
a pearly look, lets you see patterns flow in water.
What kinds of patterns can I see in my jar?
Who cares about these patterns?
When you turn the bottle slowly, you'll probably
see smooth streaks in the water. When layers of water are moving
slowly and smoothly past each other, you get this pattern, which
scientists call laminar flow.
When you suddenly stop turning the bottle, or
when you turn it very fast, you may see lots of swirls and wavy
patterns. When one layer of water moves rapidly past another layer
of water, it causes turbulence, which you see as swirly patterns.
When people design airplanes, cars, boats, golf
balls, and other things that move through air or water, they study
the patterns blowing air or flowing water makes as the object
moves through it. Differences in the flow of air or water can
affect how well an airplane flies, how much mileage a car gets
per gallon, how fast a boat can go, or how far a golf ball will
fly when you smack it with a club.