Bubble, Bubble Gas trapped in liquid can lessen toil and trouble
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Bubble, Bubble
Gas trapped in liquid can lessen toil and trouble
The bubble is the Clark Kent of the natural world: mild-mannered and a bit of a wimp-until
it strips for action. A preview of the awesome power of the seemingly innocent orb came in
1017 when English physicist Lord Rayleigh revealed how bubbles in ocean water cause the
mysterious erosion of the metal in ship propellers. Today the bubble is being harnessed of
industrial and medical uses. Someday it may even help save our life. Oil refiners employ
bubbles in the removal of sulfur from crude. Bubbles force inks through the microscopic
nozzles of ink-jet printers. Plastic surgeons use ultrasound to create bubbles that liquefy
fat they wish to remove through liposuctions. In the future, bubbles may sterilize surgical
instruments and break up kidney stones. And some physicists speculate that the heat of
bubbles targeted by sound waves is theoretically sufficient to trigger fusion, a Holy Grail
of renewable energy. None of this detracts from the bubble's charm-so natural that its
essential message is easily missed. A spherical shape enclosing a maximum volume of
gas for a given area, is a perfect demonstration of the law of conservation of energy. In
two dimensions, bubble walls trace the shortest possible distance between a series of
points. Bubbles minimize their own area by setting into a mosaic of hexagons-a pattern
accepted for the past century as using the least energy, but definitively proven only last
spring. Mathematician Thomas Hales of the University of Michigan in Ann Arbor cracked
the hexagonal problem but remains mystified by another enduring bubble puzzle: Which
bubble shapes most efficiently fill a room? "I'm working on it, but the solution won't be
found in my lifetime, " Hales says. Transparent and ephemeral, bubbles still guard their
secrets.
E p h e m e r a l A r r a y
“Scientific truth and natural phenomena as good subjects
for art as man and his emotion,” wrote Berenice Abbott,
an acclaimed American photographer who turned her
documentary skills to the illustration of mathematical
principles governing the physical world. Her photographs
of soap bubbles were shot in 1940, when she was the
picture editor of Science Illustrated. The bubbles shimmer
with intensity as they huddle, minimizing the total area of
their exposure to the nonbubble world.
A q u a t i c A r c
Bubble shows were once staples of traveling
carnivals. Science museums, notably the
Exploratorium in San Francisco, continue
to spin bubble enchantments. But none Earth's
creatures seem more fascintated with bubbles
than dolphins, which have been observed
creating ring-shaped bubbles and occasionally
swimming through them. Once a researcher at
a Hawai aquarium playfully blew bubbles at the
window of a dolphin tank- and was answered
with a perfect bubble ring inside the tank.
S p e c t r a l C h a o s
Two soap films separated by a thin layer of water
create a psychedelic bubble wall. Because some
rays of light bounce off the inner layer of film and
some of the outer, waves in the color spectrum fall
out of sync and cancel one another. With thick walls,
red disappears, leaving only blue. Magenta swirls
occur when walls thin and green vanishes. When
black appears, the wall is so delicate it's about to
pop.
T a r g e t e d T r a n s i e n c e
Shock Waves, like the yellow arc created by
a .22-caliber bullet passing through a helium-
filled soap bubble, can produce mysterious
effects. In a process called sonoluminescence,
sound waves cause an air bubble in water to
pulsate 20,000 times a second. Each collapse
can create a miniature pressure front inside
the bubble, which emits a tiny white glow
believed to be much hotter than the surface
of the sun. Such temperatures could theoretically
be harnessed to produce fusion.
C o n t a i n e d C o l l a p s e
Cavitation-bubble implosion- can make
pieces of steel look as if they've been
pummeled by artillery. An increase in
internal pressure or a drop in the pressure
of the surrounding fluid bloats a bubble to
a hundred times its original size and creates
an almost perfect vacuum inside. When
normal pressure returns, the bubble
collapses violently; if it's on a surface,
this launches a minuscule dagger of
water through its center (like the bubble
in the right, magnified 45 times). A
cavitating bubble on a ship propeller,
for instance, sends its water jet smashing
into the metal at up to 560 miles per hour.
Although the bubbles involved are at most
100 microns high and the entire cycle lasts
only 50-millionth of a second, the continuous
pounding can ruin a new propeller in a matter
of days. But the fury of cavitation may be put
to positive use someday soon. Ultrasound
directed at specific sites in the body, such as
kidney stones or tumors, can form tiny
bubbles that become micron-size jackhammers
capable of destroying their targets.
A s c e n d i n g O r d e r A queue of rising bubbles in water soon becomes disorderly. A series of time-lapse photographs, just 35- thousandths of a second from start to finfish, shows the slipstream of the flatter leading bubble accelerating the progress of its follower. A few instants later, the two merge. E l e g a n t E d d i e s When studying vortices- the turban like swirls that shear away at the edges of a moving fluid physicists can rely on bubbles to help them visualize the eddies. An electrically charged wire (bottom center, three times actual size) produces tiny hydrogen bubbles that act like bread crumbs marking the spiraling pathways of a jet of water. Eddies behave the same way in air currents, so such bubble-generated models are used in the design of airplane wings. Overly massive vortices impede ascension, causing a plane to plummet.
U p w a r d M o b i l i t y
Air bubbles follow unpredictable twisting paths as they rise in moving
water. Using long exposures, Australian physicist Richard Manasseh
hopes one day to foretell the patterns bubbles follow and the amount
of time they need to reach the surface. This could help climatologists
anticipate the pace of global warming. Whitecaps, waves, and rain drive
air bubbles containing greenhouse gases nearly 30 feet into the ocean.
Then as the bubbles ascend, the gases dissolve into the water. How
much greenhouse gas is removed from the atmosphere depends on
how long the bubbles remain submerged.
A s t u t e A n g e l s
Hidden beneath the gaudy exterior of a bubble
hive is an entire Principia of cluster geometry,
lessons extending far from the bathtub or kitchen
sink. For example, a city planner wanting to
determine the roadway connections between
three towns would do well to check out the
merger of three bubbles, which invariable
meet one another at the angles of 120 degrees,
demonstrating the shortest possible distance
between three points. Bubbles may be able to
entertain with wonder and wow, but they are
a l s o l o a d e d w i t h w i s d o m .
C l o a k e d I n t r u d e r
Bubbles would prefer to be droplets much less area to
keep intact and therefore much more energy efficient.
One pinhole in its surface is all the excuse a bubble
needs to collapse. But a pencil coated with soapy water
(you can try this at home) will fool a bubble into thinking
that the intruder belongs. Makes a good handler for
b u b b l e t r a n s p o r t .
All Photos used in this article are copyright protected by law and were taken by:
- Berenice Abbott/Commerce Graphics LTD, INC.
- Lawrence Crum/Applied Physics Lab
- Harold E. Edgerton and Kim Vandiver © The Harold E. Edgerton 1992 Trust
- Louis Pearl/Tangent Toys
- Csiro Advanced Fluid Dynamics Laboratory
- George Mattingly/Princeton/NSF
- Csiro and the Album of Visualization
- Earthtrust Project Delphis
- © The Exploratorium/ Photo by S. Schwartzenberg
- Jeremy Burgess/SPL/Photo Researchers
Reported by Fenella Saunders
Design and Layout by ©PhilDaPoohBear 2000
Courtesy of ©Discover a Member of ©Disney Publishing WorldwideYou can also read
