A soap bubble

Girl blowing bubbles

Several bubbles make a foam

Soap bubbles can easily merge.

A soap bubble is a thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with another object. They are often used for children's enjoyment, but they are also used in artistic performances. Assembling several bubbles results in a foam.

Mathematics[link]

Soap bubbles are physical illustrations of the complex mathematical problem of minimal surface. They will assume the shape of least surface area possible containing a given volume. A true minimal surface is more properly illustrated by a soap film, which has equal pressure on inside as outside, hence is a surface with zero mean curvature. A soap bubble is a closed soap film: due to the difference in outside and inside pressure, it is a surface of constant mean curvature.

While it has been known since 1884 that a spherical soap bubble is the least-area way of enclosing a given volume of air (a theorem of H. A. Schwarz), it was not until 2000 that it was proven that two merged soap bubbles provide the optimum way of enclosing two given volumes of air of different size with the least surface area. This has been dubbed the double bubble theorem.^[1]

Physics[link]

Merging[link]

When two bubbles merge, they adopt a shape which makes the sum of their surface areas as small as possible, compatible with the volume of air each bubble encloses. If the bubbles are of equal size, their common wall is flat. Else, their common wall bulges into the larger bubble, since the smaller one has a higher internal pressure than the larger one, as predicted by the Young–Laplace equation.

At a point where three or more bubbles meet, they sort themselves out so that only three bubble walls meet along a line. Since the surface tension is the same in each of the three surfaces, the three angles between them must be equal to 120°. This is the most efficient choice, again, which is also the reason why the cells of a beehive have the same 120° angle and form hexagons. Only four bubble walls can meet at a point, with the lines where triplets of bubble walls meet separated by cos⁻¹(−1/3) ≈ 109.47°. All these rules, known as Plateau's laws, determine how a foam is built from bubbles.

Stability[link]

The longevity of a soap bubble is limited by the rupture of the very thin layer of water which constitutes its surface, namely a micron-thick soap film. It is thus sensitive to :

• Drainage within the soap film: water falls down due to gravity. This can be slowed down by increasing the water viscosity, for instance by adding glycerol. Still, there is an ultimate height limit, which is the capillary length, very high for soap bubbles: around 4 metres. In principle, there is no limit in the length it can reach.
• Evaporation: this can be slowed down by blowing bubbles in a wet atmosphere, or by adding some sugar to the water.
• Dirt and fat: when the bubble touches the ground, a wall, or our skin, it usually ruptures the soap film. This can be prevented by wetting these surfaces with water (preferably containing some soap).

Bubbles in education[link]

Bubbles can be effectively used to teach and explore a wide variety of concepts to even young children. Flexibility, color formation, reflective or mirrored surfaces, concave and convex surfaces, transparency, a variety of shapes (circle, square, triangle, sphere, cube, tetrahedron, hexagon), elastic properties, comparative sizing... as well as the more esoteric properties of bubbles listed on this page. Bubbles are useful in teaching concepts starting from 2 years old and into college years. A Swiss university professor, Dr. Natalie Hartzell, has theorized that usage of artificial bubbles for entertainment purposes of young children has shown a positive effect in the region of the child's brain that controls motor skills and is responsible for coordination with children exposed to bubbles at a young age showing measurably better motion skills that those who were not.^[2]

Fun[link]

Use in play[link]

Adriaen Hanneman Two Boys Blowing Bubbles (ca. 1630)

Soap bubbles, Jean-Baptiste Siméon Chardin, mid-18th century

17th century Flemish paintings show children blowing bubbles with clay pipes verifying soap bubbles being used as entertainment for at least 400 years. The London based firm of A. & F. Pears created a famous advertisement campaign for its soaps in 1886 using a painting by Millais of a child playing with bubbles. A Chicago company called Chemtoy began selling bubble solution in the 1940s, and they have been popular with children ever since. According to one industry estimate, retailers sell around 200 million bottles annually.^{[citation needed]}

Coloured bubbles[link]

A bubble is made of transparent water enclosing transparent air. However the soap film is as thin as the visible light wavelength, resulting in interferences. This creates iridescence which, together with the bubble spherical shape and fragility, contributes to its magical effect on children and adults alike. However, it has become a challenge to produce artificially coloured bubbles.

Adding coloured dye to bubble mixtures fails to produce coloured bubbles, because the dye attaches to the water molecules as opposed to the surfactant. Therefore, a colourless bubble forms with the dye falling to a point at the base. Dye chemist Dr. Ram Sabnis has developed a lactone dye that sticks to the surfactants, enabling brightly coloured bubbles to be formed. Crystal violet lactone is an example. Another man named Tim Kehoe invented a coloured bubble which loses its colour when exposed to pressure or oxygen, which he is now marketing online as Zubbles, which are non-toxic and non-staining. In 2010, Japanese astronaut Naoko Yamazaki demonstrated that it is possible to create coloured bubbles in microgravity. The reason is that the water molecules are spread evenly around the bubble in the low-gravity environment.

Freezing[link]

Frozen soap bubble on asphalt at -17°C / +1°F

Professional 'bubbleologist' at the 2009 Strawberry Fair in Cambridge, UK.

Soap bubbles blown into air that is below a temperature of −15 °C (5 °F) will freeze when they touch a surface. The air inside will gradually diffuse out, causing the bubble to crumble under its own weight. At temperatures below about −25 °C (−13 °F), bubbles will freeze in the air and may shatter when hitting the ground. When a bubble is blown with warm air, the bubble will freeze to an almost perfect sphere at first, but when the warm air cools, and a reduction in volume occurs, there will be a partial collapse of the bubble. A bubble, created successfully at this low temperature, will always be rather small; it will freeze quickly and will shatter if increased further.^{[citation needed]}

Art[link]

Soap bubble performances combine entertainment with artistic achievement. They require a high degree of skill. Some performers use common commercially available bubble liquids while others compose their own solutions. Some artists create giant bubbles or tubes, often enveloping objects or even humans. Others manage to create bubbles forming cubes, tetrahedra and other shapes and forms. Bubbles are sometimes handled with bare hands. To add to the visual experience, they are sometimes filled with smoke, vapour or helium and combined with laser lights or fire. Soap bubbles can be filled with a flammable gas such as natural gas and then ignited.

See also[link]

• Antibubble
• Bubble pipe
• Foam
• Joseph Plateau
• Stretched grid method
• Weaire-Phelan structure

References[link]

	Book: Soap
Wikipedia books are collections of articles that can be downloaded or ordered in print.

Further reading[link]

• Oprea, John (2000). The Mathematics of Soap Films – Explorations with Maple. American Mathematical Society (1st ed.). ISBN 0-8218-2118-0
• Boys, C. V. (1890) Soap-Bubbles and the Forces that Mould Them; (Dover reprint) ISBN 0-486-20542-8. Classic Victorian exposition, based on a series of lectures originally delivered "before a juvenile audience".
• Isenberg, Cyril (1992) The Science of Soap Films and Soap Bubbles ; (Dover) ISBN 0-486-26960-4.
• Noddy, Tom (1982) "Tom Noddy's Bubble Magic" Pioneer bubble performer's explanations created the modern performance art.
• Stein, David (2005) "How to Make Monstrous, Huge, Unbelievably Big Bubbles"; (Klutz) Formerly "The Unbelievable Bubble Book" (1987) it started the giant bubble sport. ISBN 978-1-57054-257-2

External links[link]

Wikimedia Commons has media related to: Soap bubble

• [1]
• Videos of Bubble and Droplet Interactions
• A more detailed scientific explanation
• Performances with bubbles and giant bubbles
• Soap Bubble Wiki, with recipes

Frank Morgan
from the trailer for Sweethearts (1938)
Born	Francis Phillip Wuppermann (1890-06-01)June 1, 1890 New York City, New York
Died	September 18, 1949(1949-09-18) (aged 59) Beverly Hills, California
Resting place	Green-Wood Cemetery, Brooklyn, New York
Occupation	Actor
Years active	1914-1949
Spouse	Alma Muller (m.1914-1949; his death)

Frank Morgan (June 1, 1890 – September 18, 1949) was an American actor.^[1] He was best known for his portrayal of five characters, including the title character, in The Wizard of Oz (1939).

Early life[link]

Morgan was born Francis Phillip Wuppermann in New York City, the youngest of eleven children (six boys and five girls) born to Josephine Wright (née Hancox) and George Diogracia Wuppermann. His father was born in Venezuela, of German and Spanish descent, and was raised in Hamburg, Germany.^[2][3][4] His mother was born in the U.S. of English descent. The family earned its wealth distributing Angostura bitters, permitting Frank to attend Cornell University where he joined Phi Kappa Psi Fraternity.^[5] He then followed his older brother Ralph Morgan into show business, first on the Broadway stage and then into motion pictures.

Career and The Wizard of Oz[link]

His first film was The Suspect in 1916. In 1917 he provided support to his friend John Barrymore in Raffles The Amateur Cracksman, an independent film produced in and about New York City. Morgan's career expanded when talkies began, his most stereotypical role being that of a befuddled but good hearted middle-aged man. He was nominated for the Academy Award for Best Actor in 1934's The Affairs of Cellini, where he played the cuckolded Duke of Florence and was nominated for the Academy Award for Best Supporting Actor in 1942's Tortilla Flat, where he played a simple Hispanic man. Other movies of note include Hallelujah, I'm a Bum, The Great Ziegfeld, The Shop Around the Corner, The Human Comedy, The Mortal Storm, The White Cliffs of Dover and his last film, Key to the City. He also recorded a number of children's records, including the popular Gossamer Wump, released in 1949 by Capitol Records. Like most character actors of the studio era, Frank Morgan had numerous roles in many motion pictures. One of his last roles was as a key supporting player in The Stratton Story, a true story about a ballplayer (played by James Stewart) who makes a comeback after losing a leg in a hunting accident.

Morgan's most famous performance was in The Wizard of Oz (1939), in which he played the carnival huckster "Professor Marvel", the gatekeeper of the Emerald City, the driver of the carriage drawn by "The Horse of a Different Color", the armed guard leading to the Wizard's hall, the apparition of the Wizard as a monstrous disembodied Head, and the Wizard himself. Like Margaret Hamilton's Wicked Witch of the West, his characters appear on screen for only a few minutes in total, but they are memorable. He was so popular that MGM gave him a lifetime contract. Morgan was cast for the role on September 22, 1938. W. C. Fields was originally chosen for the role of the Wizard, but the studio ran out of patience after protracted haggling over his fee.

The Wizard's Kansas counterpart, Professor Marvel and the farmhand Zeke (Cowardly Lion's alter ego) are the only men wearing hats when Dorothy wakes up from being unconscious.

Personal life and death[link]

Morgan married Alma Muller in 1914; they had one son. Their marriage ended with his death in 1949. He was widely known to have had a drinking problem, according to several who worked with him, including actress Margaret Hamilton (the Wicked Witch of the West in The Wizard of Oz, 1939) and "Oz" historian Aljean Harmetz. Morgan sometimes carried a black briefcase to work fully equipped with a small mini bar.^[6] Frank Morgan's niece, Claudia Morgan (née Wuppermann) was a stage and film actress, most notable for playing the role of Vera Claythorne in the first Broadway production of Agatha Christie's And Then There Were None. Morgan was also a brother of playwright Carlos Wupperman, who was killed in the Rhineland in 1919 while on duty there with the Army of Occupation. Wupperman had only one play produced on Broadway. The Triumph of X opened at the Comedy Theater in New York City on August 24, 1921,^[7] but ran only 30 performances. The production is notable for several reasons; besides starring Frank Morgan, the play's female lead was Helen Menken (who would marry Humphrey Bogart in 1926), and in his first Broadway outing,^[8] character actor Robert Keith, father of actor Brian Keith and one-time husband of Theater Guild actress Peg Entwistle, who committed suicide by jumping from the Hollywood Sign in 1932. Frank Morgan entered show business on the coattails of his older brother, Ralph Morgan (July 6, 1883 – June 11, 1956), who was a Hollywood film, stage and character actor. Born in New York City as Raphael Kuhner Wuppermann, Ralph Morgan graduated from Columbia University with a law degree. However, he abandoned the world of jurisprudence for the vocation of journeyman actor, having already appeared in Columbia's annual Varsity Show. Morgan became so successful in stock and on Broadway that his younger brother, Frank, was encouraged to give acting a try. Frank's career would eventually overshadow that of his elder brother.

Morgan died of a heart attack on September 18, 1949, while filming Annie Get Your Gun (replaced by Louis Calhern). He was the one major player from The Wizard of Oz who did not live to see the film become both a television fixture and an American institution. He was buried in Green-Wood Cemetery in Brooklyn, whose tombstone carried his real name on the front, while noting his appearance as the Wizard on the back,^{[citation needed]} and has a star on the Hollywood Walk of Fame at 1708 Vine Street.

Filmography[link]

References[link]

External links[link]

Biography portal

Wikimedia Commons has media related to: Frank Morgan

• Frank Morgan at the Internet Movie Database
• Frank Morgan at the Internet Broadway Database
• Frank Morgan at Great Character Actors
• Frank Morgan at Find a Grave