Magical bubbles and soap films

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Magical Bubbles & Soap Films – March 20, 2010

Frank KühnemannPhysics Department

German University in Cairo

Magical bubbles andsoap films

Magical Bubbles & Soap Films – June 8, 2011

Water Droplets – Walking over Water

Films and Bubbles

Minimal Surfaces: Physics, Mathematics and Architecture

Films and Bubbles in Space

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Water drops


What gives the droplet its spherical shape?

Water molecules attract each other(surface tension)� surface like a flexible membrane, trying to reach a minimum size

� A „minimum problem“: For a fixed amount (volume) of water, what will be the shape with thesmallest surface?

� Calculation and experiments:

The Sphere

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„Walking on water“


Adding soap to the water

likes water(hydrophil)

dislikes water(hydrophob)

Tensid molecules have two different ends

Smaller force between the detergent molecules – reduced surface tension

Soap layer at the surface

Micelle in water

molecules

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Soap bubbles

A bubble

water molecule Soap particle

Repulsion between the soapparticles breaks the film

Gravity pulls down thewater molecules


How to make really large films?

Martin RutgersOhio State University

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How to make really large bubbles?

http://www.worldrecordsacademy.org/games/img/free-floating-bubble-90306.jpg


Colourful soap bubbles

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Waves on the water


Wavelength = distancebetween two crests of the wave

Light waves


λ = 0.0004 mm λ = 0.0007 mm

Different colors of light have different wavelengths λ. They are smaller than 1/1000 of a mm (0.001 mm)!(One sheet of printer paper: about 0.1 mm)

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Light waves and soap films


Light hits the film � partial reflection at the front and the back



For very thin films, the two reflected waves interact= „Interference“ between the reflected waves.

� The thickness of the film controls which colorscan be seen in the reflected light.

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The wall of the soap bubble is only some 1/1000 mm thick!


What to learn from soap bubbles? Geometry

Surface for one enclosed volume? � Sphere

Surface for two enclosed volumes? � Two spheres in contact

Contact area is not plane: bent towards the larger sphere

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How to build the perfect honeycomb?

How to enclose the largest volume with the minimum wall material, one cell next to the other?

honeycomb Soap bubbles enclosed betweentwo plates


What is the smallest area for a given frame?

Moebius Clover leaf

Which form yields a minimal surface for a given frame?Plateau problem(J.A.F. Plateau)

Calculation iscomplex� make a soapfilm model!

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Architecture: Light-weight, stable structures

Sebastian Demuth

For the minimum surface all forces are balanced � only a light-weight frame is requiredSoap films replace(d) computers!


Frei Otto: Minimal surface principles

Soap films

Wire models

Multihalle Mannheim

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Munich Olympic Stadium


Sharm El Sheikh Airport, new terminal

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Prophet‘s Mosque, Medina, Saudi Arabia


Saturday Morning Science - Water in space

What happens when gravity becomes negligible?

Astronaut Don Pettit, Ph.D., „Saturday Morning Science“Experiments aboard the International Space Station, February 2003

http://spaceflightsystems.grc.nasa.gov/WaterBalloon/#ISS

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Air bubble in a water droplet, resting on a plantlet leaf



What happens when gravity becomes negligible?

Water drops

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Back on Earth

What happens when a raindrop hits a soap bubble?

… or other intruders?

A summary

http://www.scenicreflections.com/download/208409/Earth_in_Soap_BUBBLE_Wallpaper/

„Physics?

That‘s just an advanced form of playing…“

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The new place:

Freiburg

Freiburg

Fraunhofer Institutefor PhysicalMeasurement TechniquesFreiburg

Thank you!

http://www.scenicreflections.com/download/208409/Earth_in_Soap_BUBBLE_Wallpaper/

See you soon!

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Magical bubbles and soap films