"Annenberg Media" "¶" "CAPTIONING IS MADE POSSIBLE BY THE ANNENBERG/CPB PROJECT" "WHENA FORCE ISAPPLIEDREPEATEDLY" "ATTHENATURALFREQUENCY OFANYSYSTEM," "LARGEAMPLITUDE OSCILLATIONSRESULT." "THISISTHEPHENOMENON OFRESONANCE." "HAVE YOU EVER SEEN A SINGER" "BREAK A WINEGLASS WITH HIS VOICE?" "I WILL DO THAT TODAY." "IT'S VERY DIFFICULT," "EVEN IF YOU HAVE A MAGNIFICENT VOICE LIKE MINE." "YOU NEED A VERY SPECIAL WINEGLASS." "IT MUST BE THIN AND DELICATE," "AND HAVE A VERY PURE TONE." "IF YOU TAP IT," "IT MUST GO "PING" AND NOT "THUNK."" "THAT CAN BE SUMMED UP IN JUST TWO WORDS" "VERY EXPENSIVE." "SO I ASKED THE PHYSICS DEPARTMENT" "TO BUY ME A VERY EXPENSIVE WINEGLASS." "THEY SAID, "DRINK OUT OF A PAPER CUP."" "I SAID, "NO." "IT'S FOR A DEMONSTRATION."" "THEY APPOINTED A COMMITTEE." "THEN THE COMMITTEE MET AND THOUGHT ABOUT IT." "FINALLY THEY DECIDED TO APPROPRIATE ENOUGH MONEY" "TO BUY ONE EXPENSIVE WINEGLASS TO BREAK FOR YOU," "AND HERE IT IS." "BUT BEFORE I DO IT," "I WILL EXPLAIN WHY IT'S GOING TO HAPPEN." "IT HAS TO DO WITH A PHENOMENON CALLED RESONANCE." "ON THE 1st OF JULY, 1940," "A DELEGATION OF CITIZENS MET IN WASHINGTON STATE." "THE WEATHER WAS BEAUTIFUL," "THE OCCASION HISTORIC," "AND THE SPEECHMAKING AND FANFARE" "ALTOGETHER APPROPRIATE." "THIS WAS THE GRAND OPENING" "OF THE TACOMA NARROWS BRIDGE." "FROM THE BEGINNING, THE BRIDGE," "WHICH SPANNED PUGET SOUND BETWEEN SEATTLE AND TACOMA," "WAS TRAVELED IN STYLE," "AS WELL IT SHOULD HAVE BEEN." "THE TACOMA NARROWS BRIDGE" "WAS ONE OF THE LONGER SUSPENSION BRIDGES ON EARTH." "AND, IF SOMEBODY HADN'T OVERLOOKED SOMETHING," "IT PROBABLY WOULD HAVE REMAINED" "ONE OF THE LONGER SUSPENSION BRIDGES ON EARTH." "THE PROBLEM WASN'T THAT, FROM THE BEGINNING," "PEOPLE DIDN'T PAY ATTENTION TO DETAILS." "THEY DID." "BUT SOMEWHERE ALONG THE LINE," "AND THIS WAS OBVIOUS IN THE END," "IT LOOKS AS IF SOMEONE FORGOT" "THE SIGNIFICANCE..." "OF RESONANCE." "RESONANCE." "JUST AS ITS SOUND LINGERS IN THE AIR," "THE WORD ITSELF REMAINS IN THE LANGUAGE." "RESONANCE, FROM A LATIN NOUN MEANING AN ECHO." "BUT RESONANCE CONJURES UP MORE THAN LINGUISTIC ECHOES." "IN BATTLE, FOR EXAMPLE," "ONE HEARS OF THE RESOUNDING VICTORY." "BUT SETTING CONNOTATIONS ASIDE," "RESONANCE CAN BE SEEN AS A SIMPLE MECHANICAL PRINCIPLE" "OF THE PHYSICAL WORLD." "[PLAYING BEETHOVEN SYMPHONY]" "PLEASANT SOUNDS ARE USUALLY PLEASANT" "PRECISELY BECAUSE OF THE WAY THEY RESONATE." "OF COURSE, ARTISTRY IS A FACTOR." "SO ARE COMPOSITION, SETTING, AND MOOD." "BUT RESONANCE IS ESSENTIAL." "WITH A VIOLIN OR CELLO, THE STRINGS' VIBRATIONS" "AT HUNDREDS TO THOUSANDS OF CYCLES PER SECOND" "CAUSE THE INSTRUMENT TO VIBRATE AT THE SAME FREQUENCY." "EVERY VIBRATION GIVES THE INSTRUMENT'S SOUND BOX" "A TINY PUSH" "SO THAT THE SOUND BOX VIBRATES RESONANTLY." "IN TURN, THOSE VIBRATIONS EXCITE RESONANT VIBRATIONS" "OF THE AIR INSIDE THE SOUND BOX." "THE QUALITY OF A FINE INSTRUMENT" "LIES PRECISELY IN ITS ABILITY TO RESONATE EQUALLY" "WITH EVERY NOTE THAT'S PLAYED." "WHEN A VIBRATING SYSTEM IS PUSHED OR DRIVEN" "AT THE NATURAL FREQUENCY OF THAT SYSTEM," "RESONANCE OCCURS." "INSIDE A PIANO," "VIBRATING STRINGS MAKE THE SOUND BOARD RESONATE." "THIS RESONANCE IS BEING DRIVEN" "BY THE NATURAL FREQUENCY OF THE STRING," "WHICH IS ABOUT 256 PUSHES PER SECOND AT MIDDLE C." "EACH TIME THE STRING IS STRUCK," "IT MAKES THOUSANDS OF OSCILLATIONS," "EACH ONE ADDING TO THE RESONANT RESPONSE" "OF THE SOUND BOARD." "REPEATEDLY PUSHING AN OSCILLATING SYSTEM," "WITH EVEN A SMALL FORCE EACH TIME," "MAKES SUCCESSIVE OSCILLATIONS GROW BIGGER AND BIGGER." "THE RESULTS ARE VIBRATIONS OF INCREASED AMPLITUDE." "EVEN IF THESE PUSHES ARE QUITE SMALL," "RESONANCE WILL RESULT." "THIS VIBRATING TUNING FORK" "SETS THE SURROUNDING AIR MOLECULES" "INTO HARMONIC MOTION." "BECAUSE AIR WORKS AS AN ELASTIC MEDIUM," "IT'S A GOOD CONDUCTOR" "OF TRAVELING OSCILLATIONS, OR WAVES." "EACH OSCILLATION" "GENTLY AND RHYTHMICALLY PUSHES AGAINST THE AIR," "SENDING OUT WAVES AT THE NATURAL FREQUENCY" "OF THE TUNING FORK." "WHEN THE PITCH OF THE NOTE STRUCK ON THE PIANO" "IS THE SAME AS THAT OF THE TUNING FORK," "EVEN IF THE FORK ISN'T STRUCK," "WAVES FROM THE PIANO CAN DISTURB IT" "AND SET IT INTO MOTION BY MEANS OF RESONANCE." "THE TUNING FORK AND THE PIANO STRING" "ARE EXAMPLES OF NATURALLY OSCILLATING SYSTEMS." "AND THOUGH THEY APPEAR MORE COMPLICATED," "THEY OBEY THE SAME DIFFERENTIAL EQUATION" "AS THE SIMPLE MASS ON A SPRING." "LIKE A MASS ON A SPRING," "THEY HAVE AN INTERNAL FORCE, F," "THAT NATURALLY OPPOSES ANY DISTURBANCE, x." "THAT MEANS A DIFFERENTIAL EQUATION..." "WHOSE SOLUTION" "IS A SINE FUNCTION," "REPRESENTING OSCILLATIONS AT A NATURAL FREQUENCY," "OMEGA NAUGHT," "THAT DEPENDS ON" "THE CHARACTERISTICS" "OF THE SYSTEM." "THEY ARE, IN THIS CASE, k, THE STIFFNESS OF THE SPRING," "AND m, THE MASS OF THE BOBBING OBJECT." "THIS IS ANOTHER OSCILLATING SYSTEM" "WITH A NATURAL FREQUENCY." "IN FACT, THE CHILD AND THE SWING" "ARE A KIND OF PENDULUM." "THE FREQUENCY MAY BE A THOUSAND TIMES LOWER" "THAN THE FREQUENCY OF AUDIBLE SOUND," "BUT THE PRINCIPLE'S THE SAME." "A SLIGHTLY LARGER MASS," "THIS ONE WITH LONGER LEGS," "HAS LEARNED TO PROVIDE HER OWN PERIODIC PUSH" "BY SHIFTING HER WEIGHT," "KICKING FORWARD AS FAR AS POSSIBLE," "AND TUCKING HER LEGS UNDER." "CORRECTLY APPLIED AT THE SAME POINT ON EACH CYCLE," "THAT IS, IN PHASE," "THIS YOUNG SWINGER DISPLAYS HER MASTERY" "OF THE PHENOMENON OF RESONANCE." "BUT A TRUE MASTERY OF THE PHENOMENON" "IS BEST ACHIEVED BY STARTING WITH AN OSCILLATING FORCE" "THAT DOESN'T PRODUCE RESONANCE." "WHETHERA SWING" "ORA SPRING," "OSCILLATORSHAVE THEIR NATURAL UPS AND DOWNS," "PRODUCEDBY THEINTERNALFORCE,F." "IFANADDITIONALFORCE, PROPORTIONALTOFNAUGHT" "ISAPPLIEDAT ADIFFERENT FREQUENCYOMEGA," "THERESULTIS  A MORE COMPLICATED MOTION." "ANDA MORECOMPLICATED DIFFERENTIALEQUATION." "BUTTHEMOTIONISREALLY JUSTTWOSIMPLEMOTIONS" "ADDEDTOGETHER..." "WHICHSOLVE" "THE DIFFERENTIAL EQUATION..." "LEAVINGANEQUATIONFOR A," "WHICHISTHESIZE OFTHENEWOSCILLATIONS" "PRODUCEDBY THEADDITIONALFORCE." "THESIZEOF THESEOSCILLATIONS" "DEPENDSONHOWBIG  THEFORCEIS ,aNAUGHT," "ANDONHOWCLOSE ITSFREQUENCY,OMEGA," "IS TO THE NATURAL FREQUENCY, OMEGANAUGHT." "HERE ARE SOME KEY ELEMENTS OF RESONANCE" "A FORCEFUL VOICE," "EXQUISITE CONTROL OF FREQUENCY..." "CAN THE VOICE OF ELLA FITZGERALD" "SHATTER THIS GLASS?" "AND, AN OSCILLATING SYSTEM." "WHETHERIT'SAWINEGLASS ORA SPRING," "THEAMPLITUDE OFFORCEDOSCILLATIONS" "IS SENSITIVE TO THE FREQUENCY." "A FORCE AT LOW FREQUENCY, OMEGA," "DRIVING AN OSCILLATOR" "OF NATURAL FREQUENCY, OMEGA NAUGHT," "CAUSES COMPLICATED, BUT TINY VIBRATIONS." "AT HIGHER FREQUENCY," "THE VIBRATIONS GET A LITTLE BIGGER." "BUTIFOMEGA GETS CLOSE TO OMEGA NAUGHT," "EVEN IF THE FORCE IS VERY SMALL," "SOME PRETTY SPECTACULAR THINGS" "CAN START TO HAPPEN." "ADDED TO THE NATURAL MOTION," "A LOW-FREQUENCY FORCE HAS ITS EFFECT." "AT HIGHER FREQUENCY," "THE EFFECT CAN BE MORE INTERESTING." "BUT IF OMEGA GETS CLOSE TO OMEGA NAUGHT," "THE EFFECT CAN BE POSITIVELY SHATTERING." "¶ DEE DEE DAA DAA DUM ¶" "CAN THE VOICE OF ELLA FITZGERALD" "SHATTER THIS GLASS?" "¶ WEEEE!" "¶" "BELIEVE IT." "ONLY A TINY OSCILLATING FORCE IS APPLIED TO THIS GLASS," "EVEN THOUGH THE POWER BEHIND IT" "IS ELLA FITZGERALD'S MAGNIFICENT VOICE." "BUT IT TAKES AN EQUATION" "TO SHOW WHY A SINGER WITH POWER AND CONTROL" "CAN HAVE SUCH A SHATTERING IMPACT." "OF COURSE, THE DIFFERENTIAL EQUATION" "DOES LEAVE OUT A FEW INTERESTING DETAILS." "ONE OF THE MORE INTERESTING" "IS THAT GLASS ITSELF IS A VISCOUS FLUID," "A VERY, VERY VISCOUS FLUID." "IN FACT, GLASS IS SO VISCOUS," "IT TAKES CENTURIES TO FLOW," "TO FLOW DOWNWARD THROUGH TIME AND SPACE," "WHERE IT SETTLES ALONG THE THICKER BOTTOM OF THE PANE." "GLASS IS SO VISCOUS" "THAT IT SEEMS SOLID INDEED," "AND EVEN RINGS AND RESONATES." "OF COURSE, IT'S THE VISCOSITY OF THE GLASS" "THAT PREVENTS ITS RESONANT OSCILLATIONS" "FROM BECOMING INFINITE." "AND WITHOUT THAT VISCOSITY," "THERE WOULDN'T BE AN UNBROKEN PIECE OF GLASS LEFT" "IN EITHER THE OLD WORLD..." "OR THE NEW," "WHERE THE EFFECTS OF RESONANCE CAN BE SEEN" "AND HEARD, JUST AS WELL." "FOR EXAMPLE, WHILE MUSIC IS GENERALLY" "A PLEASING EXAMPLE OF RESONANCE," "THE SAME CAN'T ALWAYS BE SAID" "FOR THE COMMON RHYTHMS OF CONTEMPORARY SOCIETY." "AS AN ANNOYING EXAMPLE OF RESONANCE," "CONSIDER THE VIBRATING WINDOW." "[JETS ROARING]" "AT THE SAME TIME, HOWEVER," "WHILE THE PANES MAY SHAKE THE LISTENER TO DISTRACTION," "BUILT-IN FRICTION AND VISCOSITY" "USUALLY KEEP THEM FROM SHATTERING." "SOMETIMES," "AS STUDIED INSIDE" "THE CALTECH SEISMIC LABORATORIES IN PASADENA," "THE EFFECTS OF RESONANCE ARE MORE THAN ANNOYING." "THEY CAN BE DEVASTATING" "BECAUSE THEY CAN AMPLIFY" "WHAT IS ALREADY AN ELEMENTAL," "ALMOST IRRESISTIBLE FORCE OF NATURE." "DURING AN EARTHQUAKE," "SEISMIC WAVES ARE SENT OUT FROM THE EPICENTER" "IN A RANGE OF FREQUENCIES." "COMPARED TO AUDIBLE SOUND," "THESE FREQUENCIES ARE GENERALLY VERY LOW." "AT EARTHQUAKE FREQUENCIES," "BUILDINGS BETWEEN 5 AND 40 STORIES TALL" "ARE TYPICALLY RESONANT." "WHEN THESE MODEL BUILDINGS ARE SHAKEN" "AT A GIVEN FREQUENCY IN A SIMULATED EARTHQUAKE," "ONE OR ANOTHER IS SET INTO RESONANT VIBRATION," "DEPENDING ON THE FREQUENCY." "GENERALLY SPEAKING," "A COMPLICATED STRUCTURE LIKE A BUILDING" "WILL SHAKE OR TWIST RESONANTLY" "AT A NUMBER OF NATURAL FREQUENCIES." "ENGINEERS CAN MINIMIZE RESONANT RESPONSES" "BY DESIGNING ISOLATION AND ENERGY ABSORPTION" "INTO THE BUILDING." "AND WITH STRICT ADHERENCE TO EARTHQUAKE ORDINANCES," "A STRUCTURE HAS A WAY TO RESIST BEING RIPPED APART" "AT ITS VERY FOUNDATIONS." "BUILDING CODES ARE LAWS." "WHEN PEOPLE THINK SOME LAWS ARE MADE TO BE BROKEN," "SOME BUILDINGS ARE BOUND TO SUFFER THE CONSEQUENCES." "[HIGH-PITCHED SOUNDS]" "THESE SOUNDS, PRODUCED BY THE WIND ACTING ON THE WIRE," "ARE ANOTHER EFFECT OF RESONANCE." "THESE WIRES SING THEIR SONG" "BY VIBRATING AT THEIR NATURAL FREQUENCY..." "BECAUSE, TO MAKE SOME RATHER SIMPLE MUSIC," "THE AIRFLOW AROUND A TAUT WIRE" "CREATES SOME RATHER COMPLEX PATTERNS." "PERHAPS TELEPHONE WIRES ONLY REALLY SING IN MYSTERY STORIES," "IN FICTION, WHERE THEIR EERIE LYRIC" "HARMONIZES WITH THE HOWLING WIND." "BUT SHOULD TELEPHONE WIRES EVER SING IN FACT," "THEIR SONG WILL BE A COMPOSITION" "OF THE PHENOMENON OF RESONANCE AND THE EVER-PRESENT WIND." "IN HIGH WINDS," "THE NORMALLY STABLE AIRFLOW AROUND A CYLINDER" "THIS WIRE, FOR EXAMPLE" "BECOMES UNSTABLE." "AS THE WIND TRIES TO CLOSE UP THE GAP" "ON THE DOWNWIND SIDE OF THE WIRE," "TO PREVENT A VACUUM," "EDDIES START TO FORM." "SOON, THE EDDIES START PEELING OFF," "RUNNING IN THE DOWNSTREAM WAKE," "CREATING A PREDICTABLE FLOW PATTERN." "EVERY TIME A VORTEX PEELS OFF," "IT GIVES THE WIRE A LITTLE PUSH." "AT A CERTAIN WIND SPEED," "THE VORTICES START PEELING OFF" "AT A RESONANT FREQUENCY OF THE WIRE," "SETTING IT INTO MOTION." "THIS EFFECT IS CALLED AN AEOLIAN HARP." "THE SKILL IT WOULD TAKE TO TUNE THESE STRINGS" "WAS HANDED DOWN FROM THE AEOLIANS," "THE ANCIENT GREEK TRIBES" "WHICH SETTLED ON THE COAST OF ASIA MINOR." "BUT THE SKILL IT TAKES TO PLAY THE AEOLIAN HARP" "COMES FROM THE MAGIC FINGERS OF THE WIND," "WHEN AIR BLOWS ACROSS THE STRINGS." "THE PRINCIPLE OF THE AEOLIAN HARP" "THE PHENOMENON CALLED RESONANCE" "EXPLAINS THE DRAMATIC SONG OF WIRES IN THE WIND." "PERHAPS, AMONG OTHER THINGS," "THE TACOMA NARROWS BRIDGE" "WAS THE MOST SPECTACULAR AEOLIAN HARP IN HISTORY." "UNFORTUNATELY, ITS FIRST PERFORMANCE" "WAS DESTINED TO RUN ONLY ABOUT FOUR MONTHS." "IN THE MEANTIME, SHE WAS A BEAUTIFUL BRIDGE." "BEAUTIFUL, BUT A LITTLE STRANGE." "EVEN BEFORE CONSTRUCTION WAS COMPLETED," "PEOPLE OBSERVED ITS PECULIAR BEHAVIOR." "THAT WAS BECAUSE, EVEN IN A LIGHT BREEZE," "RIPPLES RAN ALONG THE BRIDGE." "AFTER A WHILE," "ONE OF THE LOCAL HUMORISTS CALLED HER "GALLOPING GERTIE."" "FOR FAIRLY OBVIOUS REASONS, THE NAME STUCK," "AT LEAST UNTIL THE 7th OF NOVEMBER, 1940." "THEN, AS NOW," "SEATTLE AND TACOMA WERE SPORTS-MINDED CITIES." "FOR FOUR MONTHS," "A REGIONAL SPORT WAS CROSSING THE BRIDGE" "ON A WINDY DAY." "WHILE SOME CLAIMED IT WAS LIKE RIDING A ROLLER COASTER," "OTHERS FOUND IT DISCONCERTING" "TO SEE THE CAR IN FRONT DISAPPEAR." "HOW POPULAR THIS BRIDGE SPORT WAS," "OR HOW FAR IT MIGHT HAVE SPREAD ACROSS THE COUNTRY," "IS ANYBODY'S GUESS." "ON NOVEMBER 7, 1940," "THE WINDS WERE RELATIVELY MODERATE" "ABOUT 40 MILES PER HOUR." "A NEW MODE APPEARED." "RATHER THAN RIPPLE, THE BRIDGE BEGAN TO TWIST." "A WIND OF 40 MILES PER HOUR IS NOT TOO STRONG." "BUT IT WAS STRONG ENOUGH" "TO START THE BRIDGE TWISTING VIOLENTLY." "AND, AT 11 A.M.," "IT FELL." "INVESTIGATORS WERE MYSTIFIED." "A BRIDGE CONSTRUCTED" "ACCORDING TO THE BEST ENGINEERING STANDARDS OF THE DAY," "PERHAPS THE BEST BRIDGE IN THE WORLD," "WAS NOT SUPPOSED TO COLLAPSE." "WHAT IN THE WORLD HAD HAPPENED?" "THEODORE VON KARMAN, A CALTECH PROFESSOR," "AND A PIONEER IN MODERN AERODYNAMICS," "PROVIDED THE ANSWER." "VON KARMAN'S EXPLANATION OF VORTEX SHEDDING" "AND RESONANT OSCILLATIONS," "WAS NOT UNIVERSALLY POPULAR AMONG CONSTRUCTION ENGINEERS." "HOWEVER, AS VERIFIED BY WIND TUNNEL TESTS AT CALTECH" "AND AT THE UNIVERSITY OF WASHINGTON," "VON KARMAN'S EXPLANTION WAS CORRECT." "AND EVER SINCE, NO MAJOR BRIDGE IS COMPLETED" "WITHOUT FIRST PASSING THE TEST OF THE WIND TUNNEL." "THE TIME HAS COME TO BREAK THE WINEGLASS." "I WON'T DO IT WITH MY VOICE." "MY CONTRACT WITH THE MET WON'T PERMIT THAT." "AND THERE'S ANOTHER PROBLEM." "THIS TAKES PRACTICE," "AND I ONLY HAVE ONE WINEGLASS." "SO I'LL TRY IT FIRST USING THIS ORDINARY BEAKER." "HERE'S HOW IT'S GOING TO WORK." "THIS STUFF WILL SUBSTITUTE FOR ME" "AND MAKE A PURE TONE." "THAT WILL MAKE THE BEAKER VIBRATE." "THIS MICROPHONE IS LISTENING TO WHAT THE BEAKER DOES." "THE MICROPHONE'S OUTPUT IS ON THIS OSCILLOSCOPE." "YOU'LL SEE WHAT THE BEAKER DOES." "[PING]" "YOU SEE THAT?" "[PING]" "OK." "WHAT I HAVE TO DO IS TURN UP THE VOLUME," "AND THAT MAKES THE BEAKER VIBRATE." "THE BEAKER IS VIBRATING, BUT NOT VERY MUCH" "BECAUSE IT'S NOT EXACTLY AT THE RIGHT FREQUENCY." "IT MUST BE AT THE BEAKER'S RESONANT FREQUENCY" "IN ORDER TO VIBRATE ENOUGH TO MAKE IT BREAK." "I'LL TUNE THIS TO THE RIGHT FREQUENCY." "THERE IT IS RIGHT THERE." "THAT'S IT." "ALL RIGHT." "ALL I HAVE TO DO IS TURN UP THE VOLUME," "AND IT WILL BREAK THE BEAKER." "YOUR EARS WILL BLEED A LITTLE." "HERE WE GO!" "SO WE MANAGED TO DO IT" "WITHOUT EVER BREAKING THIS EXQUISITE WINEGLASS." "THEY KNEW I'D NEVER BREAK IT." "THAT'S IT FOR TODAY." "CAPTIONING PERFORMED BY THE NATIONAL CAPTIONING INSTITUTE, INC." "CAPTIONS COPYRIGHT 1985 CALIFORNIA INSTITUTE OF TECHNOLOGY" "THE CORPORATION FOR COMMUNITY COLLEGE TELEVISION AND THE ANNENBERG/CPB PROJECT" "PUBLIC PERFORMANCE OF CAPTIONS PROHIBITED WITHOUT PERMISSION OF NATIONAL CAPTIONING INSTITUTE" "Annenberg Media" "¶" "For information about this and other Annenberg Media programs call 1-800-LEARNER and visit us at"