"Annenberg Media" "¶" "IN THE EARLY PART OF THIS CENTURY," "IT STARTED TO BECOME CLEAR TO A SMALL NUMBER OF SCIENTISTS" "THAT BOLD NEW IDEAS WOULD BE NECESSARY" "TO SOLVE THE PERPLEXING PROBLEM OF THE STRUCTURE OF THE ATOM." "BUT EVEN BEFORE THAT, THERE BEGAN TO BE CLUES" "THAT THERE WAS SOMETHING WRONG." "THEY CAME FROM THE MOST UNEXPECTED POSSIBLE PLACE." "IN THE BEGINNING, THERE WAS LIGHT." "EVENTUALLY, THERE WAS A LIGHT BULB" "AND THE FACT THAT THE HOTTER ITS FILAMENT," "THE BRIGHTER IT GLOWS." "WHO WOULD HAVE THOUGHT THAT SUCH A COMMON PHENOMENON" "WOULD HAVE SET THE SCIENTIFIC IMAGINATION ON FIRE?" "IN FACT, ALL GLOWING BODIES," "FROM A COAL IN THE FURNACE" "TO AN EMBER IN THE FIRE," "FROM MOLTEN IRON IN A STEEL MILL" "TO THE FILAMENT IN AN INCANDESCENT LIGHT BULB" "THE BEHAVIOR IS REMARKABLY ALIKE." "NO MATTER WHAT IT'S MADE OF," "THE COLOR WITH WHICH A BODY GLOWS" "DEPENDS ONLY ON ITS TEMPERATURE." "IN FACT, IF THEY HAVE THE SAME TEMPERATURE," "ALL THESE BODIES WILL GLOW WITH THE SAME COLOR." "IT'S AN AMAZING FACT," "AND IN GERMANY, DR. MAX PLANCK" "BELIEVED IT DESERVED A GOOD EXPLANATION." ""I HAD ALWAYS REGARDED THE SEARCH FOR THE ABSOLUTE" "AS THE LOFTIEST GOAL OF ALL SCIENTIFIC ACTIVITY,"" "HE WROTE IN HIS AUTOBIOGRAPHY." ""I EAGERLY SET TO WORK," HE ADDED." "NEEDLESS TO SAY, HIS WORK WAS CUT OUT FOR HIM." "PLANCK'S PROBLEM STEMMED FROM APPLYING MAXWELL'S THEORY" "TO PREDICT THE AMOUNT OF LIGHT" "A GLOWING BODY WOULD RADIATE AT EACH FREQUENCY." "OF COURSE, JAMES CLERK MAXWELL'S THEORY" "WAS STILL THE FINAL WORD ON LIGHT" "AND OTHER FORMS OF ELECTROMAGNETIC RADIATION," "AND PROPERLY SO." "BUT IT COULDN'T ACCOUNT FOR THE FACT" "THAT AS SOON AS ANY BODY BECOMES HOT ENOUGH TO GLOW," "IT GLOWS RED." "WHY?" "WHY WASN'T MORE HIGHER FREQUENCY," "BLUER LIGHT RADIATED AS WELL?" "IN ALL GLOWING BODIES," "WHY SHOULD THERE BE LESS LIGHT AT A HIGHER FREQUENCY?" "INTUITION TOLD PLANCK THAT ALL COULD BE EXPLAINED" "IF IT TAKES MORE ENERGY" "TO MAKE LIGHT AT HIGHER FREQUENCIES." "EVEN THOUGH THERE WAS NOTHING IN MAXWELL'S THEORY" "TO SUGGEST THAT THE ENERGY OF LIGHT" "MAY BE RELATED TO ITS FREQUENCY," "PLANCK WROTE AN EQUATION TO SUBSTANTIATE HIS INTUITION." "THE ENERGY OF LIGHT, E," "IS EQUAL TO A CONSTANT, h," "TIMES THE FREQUENCY, f." "PLANCK HADN'T SET OUT TO DEFY THE LAWS OF PHYSICS." "ON THE CONTRARY, HIS INTENTION WAS TO PRESERVE," "NOT DESTROY, THE INTEGRITY OF MAXWELL'S THEORY." "IN HIS EFFORT, PLANCK SAW A SOLUTION" "THAT HAPPENED TO BE REMARKABLY SIMILAR TO THE SOLUTION" "FOR THAT OLD PROBLEM OF INSTANTANEOUS SPEED." "IN THAT CASE, h WAS A QUANTITY THAT WOULD SHRINK TO ZERO" "AT JUST THE RIGHT MOMENT IN THE CALCULATION." "IF THE SAME THING HAPPENED IN PLANCK'S THEORY," "MAXWELL'S EQUATIONS WOULD BE RECONCILED" "WITH EXPERIMENTAL EVIDENCE," "AND THE RADIATION PROBLEM WOULD BE SOLVED." "BUT h WOULDN'T SHRINK TO ZERO." "INSTEAD OF VANISHING AS HE'D HOPED," "IT TURNED OUT TO HAVE A DEFINITE VALUE." "WHEN HE FOUND THAT VALUE, NOW CALLED PLANCK'S CONSTANT," "PLANCK FOUND SOMETHING MORE IMPORTANT" "THAN AN EXPLANATION FOR GLOWING BODIES." "HE FOUND A NEW AND FUNDAMENTAL TRUTH ABOUT NATURE." "WHETHER BY AN ELECTRICAL DEVICE OR THE SUN ITSELF," "LIGHT IS ABSORBED OR RADIATED IN DISCRETE BUNDLES OF ENERGY." "THE IDEA WAS RADICAL AND DISTURBING," "BUT CONFIRMING EVIDENCE WAS ON THE WAY." "THE EVIDENCE CAN STILL BE SEEN TODAY" "IN THE BEHAVIOR OF A GOLD-LEAF ELECTROSCOPE." "WHEN THE ELECTROSCOPE IS CHARGED," "THE LEAF RISES AND STAYS ALOFT" "UNTIL IT'S HIT BY A BEAM OF ULTRAVIOLET LIGHT." "AN ORDINARY PIECE OF GLASS TRANSMITS VISIBLE LIGHT," "BUT IT BLOCKS THE HIGH FREQUENCY ULTRAVIOLET LIGHT." "WHEN IT'S INTERPOSED," "THE ELECTROSCOPE DOESN'T DISCHARGE." "BUT WHEN THE GLASS IS REMOVED," "THE LEAF FALLS AGAIN." "THIS PROVES THAT THE ULTRAVIOLET LIGHT" "DOES THE JOB." "IT'S CALLED THE PHOTOELECTRIC EFFECT." "IT WAS ALBERT EINSTEIN'S EXPLANATION" "OF THE PHOTOELECTRIC EFFECT" "AND NOT HIS THEORY OF RELATIVITY" "THAT WOULD EVENTUALLY WIN HIM THE NOBEL PRIZE IN PHYSICS." "IN MODERN TERMS, HERE'S WHAT HE SAID." "AN ELECTRON IN A METAL LACKS ENOUGH ENERGY TO ESCAPE" "BY AN AMOUNT CALLED THE WORK FUNCTION." "BUT IF AN ELECTRON ABSORBS ULTRAVIOLET LIGHT" "THAT ARRIVES IN A BUNDLE" "HAVING THE ENERGY GIVEN BY PLANCK'S FORMULA," "THEN THE ELECTRON CAN GAIN MORE THAN ENOUGH ENERGY" "TO ESCAPE FROM THE METAL." "IF THAT'S THE CASE," "IT CAN COME OUT WITH KINETIC ENERGY" "EQUAL TO h TIMES f, MINUS THE WORK FUNCTION." "THIS IS CALLED EINSTEIN'S PHOTOELECTRIC EFFECT EQUATION." "IT WAS THE PERFECT SOLUTION, AND PROVED AS SUCH" "BY ROBERT A. MILLIKAN IN HIS CHICAGO LABORATORY." "WHEN HE MEASURED THE ENERGIES OF ELECTRONS" "EJECTED FROM VARIOUS METALS" "BY DIFFERENT FREQUENCIES OF LIGHT," "MILLIKAN VERIFIED THAT WHILE EACH METAL" "HAS A DIFFERENT WORK FUNCTION," "PLANCK'S CONSTANT HAS THE SAME UNIVERSAL VALUE FOR ALL OF THEM." "BUT THIS EXPLANATION OF THE PHOTOELECTRIC EFFECT" "NOT ONLY CONFIRMED PLANCK'S THEORY," "IT SHOWED DIRECTLY THAT BUNDLES OF ENERGY" "ALREADY EXIST IN THE ELECTROMAGNETIC FIELD." "IN OTHER WORDS, LIGHT COMES IN PARTICLES," "PARTICLES WHICH ARE NOW CALLED PHOTONS." "BUT WAIT A MINUTE." "A CENTURY EARLIER, THOMAS YOUNG HAD PROVED" "LIGHT TRAVELS IN WAVES." "WAS IT NOW GOING TO TURN OUT" "THAT LIGHT IS REALLY MADE OF PARTICLES AFTER ALL?" "PERHAPS THIS WHOLE BUSINESS OF PARTICLES AND WAVES" "WAS IN NEED OF AN ENTIRELY FRESH PERSPECTIVE." "LOUIS DE BROGLIE GOT A HISTORY DEGREE" "EN ROUTE TO A CAREER IN FRENCH GOVERNMENT," "A FRESH APPROACH TO PHYSICS IF THERE EVER WAS ONE." "MAYBE THAT'S WHY, IN THE 1920s," "HE WAS THE ONE TO ASK A CRUCIAL QUESTION." "IF LIGHT WAVES CAN BE PARTICLES," "IS IT POSSIBLE THAT PARTICLES SUCH AS ELECTRONS" "CAN ALSO BE WAVES?" "TO BEGIN WITH, PARTICLES HAVE ENERGY AND MOMENTUM," "WHILE WAVES HAVE FREQUENCY AND WAVELENGTH." "OBVIOUSLY, THESE ENTITIES HAVE DIFFERENT KINDS OF PROPERTIES." "DE BROGLIE SUSPECTED THERE WAS SOME SORT OF CONNECTION." "PLANCK'S THEORY HAD GIVEN A CLUE" "TO WHAT IT MIGHT BE." "MAX PLANCK HAD ASSOCIATED THE ENERGY OF A LIGHT PARTICLE" "WITH THE FREQUENCY OF ITS WAVE." "GOING A STEP FURTHER," "DE BROGLIE COMBINED THIS WITH A PARTICLE'S ENERGY" "ACCORDING TO EINSTEIN'S RELATIVITY THEORY," "E=mc-SQUARED." "THIS BOLD MIXTURE" "OF WAVE AND PARTICLE PROPERTIES" "SUGGESTED THE NEXT STEP." "COULD PARTICLES TRAVELING" "AT LESS THAN THE SPEED OF LIGHT" "HAVE THEIR MOMENTUM RELATED" "TO THEIR WAVELENGTH?" "DE BROGLIE BELIEVED SO." "HE THOUGHT THAT" "JUST AS A PARTICLE'S ENERGY" "IS RELATED TO A FREQUENCY," "A PARTICLE'S MOMENTUM" "IS RELATED TO A WAVELENGTH." "IT WAS A RADICAL IDEA." "NOT ONLY CAN LIGHT WAVES BEHAVE LIKE PARTICLES," "BUT PARTICLES CAN BEHAVE LIKE WAVES." "BUT WITHIN A YEAR, EXPERIMENTS HAD VERIFIED" "THAT BEAMS OF ELECTRONS COULD BE DIFFRACTED" "MUCH LIKE BEAMS OF LIGHT." "EVEN BEYOND THAT, DE BROGLIE'S IDEA" "SEEMED TO EXPLAIN A MOST MYSTERIOUS ASPECT" "OF NIELS BOHR'S MODEL OF THE ATOM." "BOHR'S THEORY WAS BUILT ON THE NOTION" "THAT ELECTRONS CAN ONLY EXIST IN CERTAIN-SIZED ORBITS," "ONLY IN THOSE ORBITS AND NOWHERE IN BETWEEN." "BUT IF ELECTRONS ARE VIEWED AS WAVES CIRCLING THE NUCLEUS," "THEY HAVE TO EXIST IN ORBITS THAT INCREASE" "A WHOLE WAVELENGTH AT A TIME." "THAT WAY, EACH ORBIT CONSISTS" "OF ELECTRON WAVES THAT INTERFERE CONSTRUCTIVELY," "AND REINFORCE THEMSELVES ON EVERY ORBIT." "WHEN COMBINED WITH DE BROGLIE'S FORMULAS," "THIS IDEA EXACTLY REPRODUCED" "THE ORBITS OF BOHR'S MODEL OF THE ATOM" "BECAUSE THE ANGULAR MOMENTUM OF EACH ORBIT" "WOULD BE AN INTEGER TIMES h-BAR." "ON BALANCE, LOUIS DE BROGLIE'S IDEA HAD BEEN BRILLIANT." "IT HAD GIVEN AN INSIGHTFUL AND ELEGANT EXPLANATION" "OF NIELS BOHR'S MODEL OF THE ATOM." "IT HAD BEEN SUPPORTED BY SOLID EXPERIMENTAL EVIDENCE." "NOT SURPRISINGLY, IT DROVE OTHER PHYSICISTS" "EVER DEEPER INTO THE NATURE OF MATTER." "IN AUSTRIA, ERWIN SCHRODINGER" "PONDERED THE IMPLICATIONS OF THE FRENCHMAN'S WORK" "AND PRODUCED A THEORY OF HIS OWN" "THAT TOOK OFF FROM DE BROGLIE'S IDEAS." "A WAVE HAS AN AMPLITUDE AND A WAVELENGTH" "BUT NO BEGINNING OR END" "AND NOTHING LIKE THE DEFINITE POSITION OF A PARTICLE." "THAT REMAINS TRUE IF A WAVE OF THE SAME WAVELENGTH IS ADDED" "EITHER IN PHASE OR OUT." "BUT IF WAVES OF DIFFERENT WAVELENGTHS ARE ADDED," "THE RESULTING SHAPE IS ALTERED." "IF THOSE WAVELENGTHS ARE CLOSE TOGETHER," "AND ESPECIALLY IF MORE WAVES OF NEARBY WAVELENGTH ARE ADDED," "THE RESULT CAN BE A KIND OF WAVE" "CONCENTRATED IN A LIMITED REGION OF SPACE." "SO WITH A RANGE OF WAVELENGTHS" "AND THEREFORE A RANGE OF MOMENTUM," "A WAVELIKE OBJECT CAN BE CONSTRUCTED" "IN A FAIRLY DEFINITE PLACE." "BUT BECAUSE IT HAS A RANGE OF MOMENTA," "IT SPREADS OUT AS IT MOVES ALONG." "IT ISN'T REALLY A PARTICLE, AND IT ISN'T REALLY A WAVE." "WHAT IN THE WORLD IS IT?" "IT IS THE CLEAREST POSSIBLE DESCRIPTION" "OF THE NATURE OF PHOTONS AND ELECTRONS," "OF THE MATTER WHICH MAKES UP THE UNIVERSE" "AND EVERYTHING IN IT." "AS AN IDEA IN 1926, IT WAS THE HEART AND SOUL" "OF ERWIN SCHRODINGER'S WAVE MECHANICS." "LIGHT PASSING THROUGH TWO SLITS" "CAUSES AN OBVIOUS WAVE INTERFERENCE," "WHICH CLEARLY REVEALS ITSELF AS A PATTERN" "OF LIGHT AND DARK STRIPES." "THERE IS NO QUESTION ABOUT LIGHT BEING A WAVE." "ONLY WAVES BEHAVE THIS WAY." "SO THE QUESTION IS" "HOW CAN LIGHT BE PARTICLES" "AND STILL INTERFERE LIKE WAVES?" "IF LIGHT IS MADE OF PHOTON PARTICLES," "INDIVIDUAL LITTLE THINGS" "WHICH CAN'T ARRIVE AS A SPREAD-OUT PATTERN," "THEN EACH PARTICLE HAS TO HIT THE SCREEN INDIVIDUALLY" "A SINGLE SPOT OF LIGHT HERE, FOR EXAMPLE," "ANOTHER PHOTON THERE." "IT'S IMPOSSIBLE TO PREDICT PRECISELY" "WHERE ANY SPOT WILL APPEAR," "BUT IT IS POSSIBLE TO SEE" "THAT MORE PHOTONS LAND IN SOME PLACES THAN OTHERS." "IN FACT, THERE'S A HIGHER PROBABILITY" "THAT MORE PHOTONS WILL LAND IN CERTAIN REGIONS," "AND EVENTUALLY," "BECAUSE OF THOSE PROBABILITIES," "THE RESULT WILL BE" "A DEFINITE WAVELIKE DIFFRACTION PATTERN OF PARTICLES." "THIS WAS THE EXPLANATION PROPOSED BY MAX BORN." "PHOTONS MIGHT BE PARTICLES, HE SAID," "BUT THE PATTERNS THEY MAKE" "ARE RULED BY PROBABILITIES THAT INTERFERE AS WAVES." "AND ONE OF BORN'S COLLEAGUES, WERNER HEISENBERG," "TOOK THAT IDEA ONE STEP FURTHER." "BECAUSE PARTICLES ARE ASSOCIATED WITH PROBABILITIES" "THAT INTERFERE LIKE WAVES, HE SAID," "IT'S IMPOSSIBLE TO KNOW" "BOTH THE EXACT MOMENTUM AND THE EXACT POSITION" "OF ANY PARTICLE AT THE SAME TIME." "THE IDEA MAY BE A LITTLE HARD TO GRASP," "BUT THAT WAS JUST THE POINT" "PARTICLES, BEING WAVES AS WELL," "ARE A LITTLE HARD TO GRASP." "THE NATURE OF A REGULAR WAVE" "WITH A DEFINITE WAVELENGTH" "IS TO SPREAD OUT IN SPACE." "IF THIS WAVE REPRESENTS A PARTICLE," "THEN ITS WAVELENGTH" "TRANSLATES INTO A DEFINITE MOMENTUM." "HOWEVER, NOTHING HERE" "ACCOUNTS FOR THE PARTICLE'S LOCATION." "THE PARTICLE'S PLACE CAN BE MADE MORE DEFINITE" "BY ADDING WAVE AFTER WAVE OF DIFFERENT LENGTHS," "BUT EACH NEW WAVELENGTH MEANS A NEW MOMENTUM." "IN OTHER WORDS, THE MORE ONE KNOWS" "ABOUT WHERE A PARTICLE IS," "THE LESS ONE CAN TELL" "ABOUT WHERE AND HOW FAST IT'S GOING." "AS THE POSITION OF THE WAVE" "BECOMES MORE DEFINITE," "THE MOMENTUM OF THE PARTICLE" "BECOMES LESS SO." "THAT RELATIONSHIP," "DELTA-x TIMES DELTA-p IS APPROXIMATELY EQUAL TO h-BAR," "IS CALLED THE HEISENBERG UNCERTAINTY PRINCIPLE." "WERNER HEISENBERG," "SEARCHING FOR DEEPER SCIENTIFIC TRUTH," "HAD RAISED UNCERTAINTY TO THE LEVEL" "OF A FUNDAMENTAL PRINCIPLE OF NATURE," "BUT THE IRONY OF THIS STORY LIES ELSEWHERE." "DRAWN TO SOMETHING UNIVERSAL" "IN THE NATURE OF ALL GLOWING BODIES," "MAX PLANCK DISCOVERED THAT LIGHT IS RADIATED" "IN LITTLE BUNDLES OF ENERGY." "WHEN ALBERT EINSTEIN SOLVED THE PHOTOELECTRIC PROBLEM," "HE CONFIRMED THAT PLANCK'S ENERGY PACKETS" "EXIST AS PARTICLES IN THE ELECTROMAGNETIC FIELD." "COMBINING THE INSIGHTS" "OF PLANCK AND EINSTEIN," "DE BROGLIE SUGGESTED" "THAT NOT ONLY COULD WAVE" "BEHAVE LIKE PARTICLES," "BUT PARTICLES COULD BEHAVE LIKE WAVES." "ERWIN SCHRODINGER UNDERSTOOD" "THAT IF ENOUGH WAVES OF DIFFERENT LENGTHS" "ARE ADDED TOGETHER," "THE RESULT IS A WAVE" "THAT'S CONCENTRATED IN ONE OR ANOTHER PLACE," "LIKE A PARTICLE." "THEN MAX BORN SAW" "THAT WHILE IT'S OBVIOUSLY IMPOSSIBLE" "FOR ONE PARTICLE TO CREATE A VISIBLE WAVE PATTERN," "A CLUSTER OF PARTICLES," "WHOSE BEHAVIOR IS DETERMINED BY PROBABILITIES," "CAN FALL INTO A PATTERN" "THAT LOOKS VERY MUCH LIKE WAVE INTERFERENCE." "AND IN THAT VERY FACT," "WERNER HEISENBERG SAW THE TRADEOFF" "BETWEEN THE PARTICLE QUALITY" "AND THE WAVE QUALITY OF LIGHT." "WHEN THE UNCERTAINTIES OF POSITION AND MOMENTUM" "ARE COMBINED," "THE PRODUCT IS APPROXIMATELY EQUAL TO PLANCK'S CONSTANT." "AND THAT, BEGINNING WITH MAX PLANCK'S CONSTANT" "AND COMING FULL CIRCLE," "IS THE IRONY." "PLANCK'S QUEST FOR TRUTH BECAME A JOURNEY" "THAT LED TO THE HEART OF QUANTUM PHYSICS." "YET, TO THE END," "HE HIMSELF NEVER ACCEPTED" "THE PROFOUND IMPLICATIONS OF HIS OWN WORK," "AND FOR THAT MATTER," "NEITHER DID ALBERT EINSTEIN," "WHO SAID, "IT SEEMS HARD TO LOOK IN GOD'S CARDS," ""BUT I CANNOT FOR A MOMENT" ""BELIEVE THAT HE PLAYS DICE" "AS THE CURRENT QUANTUM THEORY ALLEGES HE DOES."" "IT WOULD TAKE NEW GENERATIONS OF BRIGHT YOUNG SCIENTISTS" "TO ACCEPT FULLY" "THE ASTONISHING IMPLICATIONS OF THE NEW THEORY." "THEY HONOR AND OBEY" "THE LAWS OF CLASSICAL MECHANICS" "BUT EMBRACE QUANTUM THEORY AS WELL." "FOR BY NOW, NO ONE CAN DENY" "THE THEORETICAL PERFECTION OF THE NEW PHYSICS" "NOR THE FACT THAT IT ACTUALLY WORKS." "I HAVE HERE A DEMONSTRATION" "OF HOW THE NEW PHYSICS WORKS," "WHICH IS VERY ELEGANT," "BUT IT'S SO SIMPLE," "YOU CAN EASILY DO IT AT HOME" "WITH SOME POLAROID SUNGLASSES." "BEFORE I SHOW IT TO YOU," "LET ME REMIND YOU OF HOW POLAROID WORKS." "REMEMBER THAT LIGHT IS A WAVE," "BUT IT'S A TRANSVERSE WAVE." "IF LIGHT'S MOVING IN THIS DIRECTION," "THE ELECTRIC FIELD IS ACTUALLY OSCILLATING" "PERPENDICULAR TO THAT DIRECTION," "EITHER UP AND DOWN" "OR SIDEWAYS IN AND OUT OF THE BLACKBOARD" "OR OBLIQUE TO THAT DIRECTION." "IN AN ORDINARY INCANDESCENT LIGHT BULB," "THE LIGHT IS OSCILLATING IN ALL POSSIBLE DIRECTIONS" "PERPENDICULAR TO THE DIRECTION" "THAT THE LIGHT IS GOING IN." "THE DIRECTION IN WHICH THE LIGHT IS OSCILLATING" "IS CALLED ITS POLARIZATION." "AN ORDINARY LIGHT IS UNPOLARIZED." "WHAT POLAROID DOES" "IS TO PERMIT THROUGH THE POLAROID FILTER" "ONLY ONE DIRECTION OF OSCILLATION" "OF THE ELECTROMAGNETIC FIELD." "LET ME TRY TO ILLUSTRATE THE POINT TO YOU." "I HAVE A SOURCE OF LIGHT." "THE LIGHT IS ON THE SCREEN." "THIS IS A PIECE OF POLAROID GLASS." "IF I PUT THE POLAROID GLASS INTO THE BEAM," "THE LIGHT GETS A LITTLE BIT DIMMER." "PART OF THAT IS BECAUSE THE GLASS IS DIRTY." "MOST OF IT'S BECAUSE THE GLASS LETS THROUGH" "ONLY ONE POLARIZATION OF LIGHT." "I CAN TURN THE DIRECTION OF POLARIZATION" "BY TURNING THIS HANDLE, BUT WHEN I DO THAT," "YOU SEE NOTHING HAPPENING ON THE SCREEN" "BECAUSE YOUR EYE IS INSENSITIVE" "TO THE POLARIZATION OF LIGHT." "IN ORDER TO SHOW YOU THAT LIGHT IS POLARIZED," "I MUST USE A SECOND PIECE OF POLAROID IN THE BEAM." "I'LL PUT HERE A SECOND PIECE OF POLAROID." "NOW THE LIGHT BECOMES DIMMER AGAIN," "BUT THIS TIME IT REALLY IS" "ONLY BECAUSE IT'S A DIRTY PIECE OF GLASS." "THIS PIECE OF POLAROID IS ALIGNED" "IN THE SAME DIRECTION AS THE FIRST PIECE." "EVERYTHING THAT GETS THROUGH THE FIRST PIECE" "ALSO GETS THROUGH THE SECOND PIECE." "TO SHOW YOU HOW POLAROID WORKS," "I MUST ROTATE THE DIRECTION OF THE SECOND PIECE." "WHEN I DO IT, THE LIGHT GETS DIMMER" "UNTIL NOTHING GETS THROUGH AT ALL." "ONLY LIGHT THAT'S POLARIZED UP AND DOWN" "IS GETTING THROUGH THE FIRST PIECE." "THE SECOND PIECE OF GLASS" "WILL TRANSMIT ONLY LIGHT THAT'S POLARIZED HORIZONTALLY," "AND THERE ISN'T ANY OF THAT," "SO NOTHING GETS THROUGH, AND THE SCREEN IS BLANK." "IT'S MORE DIFFICULT TO UNDERSTAND" "WHEN THE SECOND ONE IS OBLIQUE," "LIKE THAT." "THEN PART OF A LIGHT GETS THROUGH" "BECAUSE THE LIGHT COMES IN, IT'S WAVING UP AND DOWN." "THIS ONE ALLOWS LIGHT WAVING THIS WAY," "BUT EACH VECTOR HAS A COMPONENT ALONG THAT DIRECTION," "AND THAT PART OF THE WAVE GETS THROUGH." "THAT'S HOW POLAROID WORKS." "IT'S EASY TO UNDERSTAND" "SO LONG AS WE BELIEVE THAT LIGHT IS A WAVE," "BUT LIGHT IS ALSO A PARTICLE," "AND THERE MUST BE A PARTICLE EXPLANATION" "OF HOW THIS OCCURS AS WELL." "THE PROBLEM HERE IS I CAN'T SAY" "THAT PART OF THE LIGHT GETS THROUGH THE SECOND FILTER" "WHEN IT'S OBLIQUE." "A PARTICLE GETS THROUGH, OR IT DOESN'T." "EVERY PHOTON COMES THROUGH OR DOESN'T GET THROUGH." "THE PHOTONS COME ALONG, THE LIGHT PARTICLES," "TO THE FIRST FILTER." "THE FIRST FILTER SAYS," ""EACH OF YOU IS EITHER POLARIZED UP AND DOWN OR SIDEWAYS." ""NOTHING ELSE IS PERMITTED," ""BUT YOU'RE POLARIZED UP AND DOWN OR SIDEWAYS" ""WITH SOME PROBABILITY." ""HALF OF YOU ARE UP AND DOWN," "AND HALF OF YOU ARE SIDEWAYS."" "THEN THE LIGHT GETS THROUGH THE FIRST ONE" "THE ONES THAT ARE UP AND DOWN." "THE SIDEWAYS PHOTONS GET STOPPED." "BETWEEN THE TWO, I'VE ONLY GOT PHOTONS POLARIZED UP AND DOWN." "THIS ONE, IN THIS SIDEWAYS DIRECTION, SAYS," ""YOU GUYS ARE ALL UP AND DOWN." "I ONLY PERMIT SIDEWAYS PHOTONS."" "SO NOTHING GETS THROUGH." "IF I TURN IT UP, IT SAYS," ""I PERMIT UP AND DOWN PHOTONS."" "THEY GET THROUGH, AND YOU SEE THE LIGHT." "WHEN I TURN IT IN THE OBLIQUE DIRECTION," "THIS SAYS, "YOU THOUGHT YOU WERE ALL UP AND DOWN," ""BUT THAT'S NOT TRUE." ""EVERYBODY'S GOT TO BE" ""OBLIQUE THIS WAY OR THAT WAY" ""WITH SOME PROBABILITY." ""YOU THOUGHT YOU WERE UP AND DOWN" "BECAUSE HALF OF YOU ARE THIS WAY AND HALF THAT WAY."" "HE LETS THROUGH THOSE POLARIZED THIS WAY." "THAT'S THE PARTICLE EXPLANATION OF POLAROID." "I'D LIKE TO TRY ONE MORE EXPERIMENT WITH YOU." "I'LL TURN THIS POLAROID SO NOTHING GETS THROUGH." "THEN I'LL TAKE THIS POLAROID, A THIRD PIECE," "AND PUT IT AT AN OBLIQUE ANGLE" "TO THE OTHER TWO." "THIS ONE IS UP AND DOWN." "THIS ONE IS HORIZONTAL." "THIS ONE IS OBLIQUE." "I'LL PUT THE OBLIQUE POLAROID BETWEEN THE OTHER TWO." "ONLY UP AND DOWN PHOTONS GET THROUGH THE FIRST." "THEY GET TO THE OBLIQUE ONE," "HE SAYS, "YOU HAVE A 50% PROBABILITY" ""OF BEING OBLIQUE THIS WAY AND GETTING THROU," ""50% PROBABILITY OF BEING THAT WAY" "AND NOT GETTING THROUGH."" "THE ONES THAT ARE THIS WAY GET THROUGH," "AND THEY GET TO THIS GUY." "HE SAYS, "YOU THINK YOU'RE OBLIQUE, BUT YOU AREN'T." ""EACH HAS A 50% PROBABILITY OF BEING HORIZONTAL" "AND A 50% PROBABILITY OF BEING VERTICAL."" "THE HORIZONTAL ONES GET THROUGH." "THAT MEANS THE LIGHT REAPPEARS ON THE SCREEN." "YOU REALLY BELIEVE THAT WILL HAPPEN?" "A SCIENTIST HAS TO BE PREPARED TO MAKE PREDICTIONS." "LET'S SEE WHAT YOUR PREDICTIONS ARE." "HOW MANY THINK THE LIGHT WILL REAPPEAR?" "RAISE YOUR HANDS." "LET ME SEE." "HOW MANY THINK IT WON'T REAPPEAR?" "I'VE GOT ALL YOUR NAMES WRITTEN DOWN." "LET'S TRY THE EXPERIMENT." "I'LL PUT THIS INTO THE BEAM." "I CLAIM THE LIGHT WILL REAPPEAR." "AND THERE IT IS," "AND THAT IS THE ESSENCE" "OF THE WAY THE NEW PHYSICS WORKS." "WE'LL GO ON WHEN WE MEET NEXT TIME." "CAPTIONING IS MADE POSSIBLE BY THE ANNENBERG/CPB PROJECT" "CAPTIONING PERFORMED BY THE NATIONAL CAPTIONING INSTITUTE, INC." "CAPTIONS COPYRIGHT 1987 CALIFORNIA INSTITUTE OF TECHNOLOGY," "THE CORPORATION FOR COMMUNITY COLLEGE TELEVISION, 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"