WELCOME TO THE FRONTIERS OF PHYSICS
LECTURE AT THE UNIVERSITY OF WASHINGTON. MY NAME IS NATALIE PAQUETTE AND I'M THE
ASSISTANT PROFESSOR OF PHYSICS HERE AT UW. THE FRONTIERS OF PHYSICS LECTURE SERIES
BRINGS TO THE UNIVERSITY OF WASHINGTON AND THE SEATTLE COMMUNITY WORLD-CLASS SCIENTISTS
TO EXPLAIN TO YOU THE MOST EXCITING DEVELOPMENTS AND DISCOVERIES IN PHYSICS. THE BI-ANNUAL LECTURE
SERIES STARTED IN 2015 AND HAS SO FAR SHOWCASED 11 OUTSTANDING PRESENTATIONS BY TOP FIGURES
IN THE FIELD INCLUDING FIVE NOBEL LAUREATES. THE TOPICS COVER A WIDE RANGE OF PHENOMENA
FROM THE EARLY UNIVERSE TO THE PRESENT, FROM THE GALACTIC SCALE TO THE
MICROSCOPIC WORLD OF QUANTUM MECHANICS, FROM ABSTRACT THEORETICAL CONCEPTS TO
SUBTLETIES OF OTHERWISE FAMILIAR PHENOMENA. THE LECTURE SERIES IS ONLY POSSIBLE THROUGH
THE WORK OF A DIVERSE COMMITTEE THAT INCLUDES BOTH MEMBERS OF THE FACULTY AND OUR COMMUNITY.
TODAY IT IS MY GREAT PLEASURE TO INTRODUCE THREE DISTINGUISHED PHYSICISTS, ALL THREE FROM THE
UNIVERSITY OF WASHINGTON. THE 2021 LAUREATES OF THE BREAKTHROUGH PRIZE IN FUNDAMENTAL PHYSICS
ERIC ADELBERGER, JENS GUNDLACH, AND BLAYNE HECKEL. "FOR PRECISION FUNDAMENTAL MEASUREMENTS THAT TEST
OUR UNDERSTANDING OF GRAVITY, PROBE THE NATURE OF DARK ENERGY, AND ESTABLISH LIMITS TO COUPLINGS
ON DARK MATTER." I WILL INTRODUCE EACH OF OUR SPEAKERS IN TURN BUT WANT TO SAY FIRST A FEW WORDS
ON THE IMPORT OF THEIR TREMENDOUS ACCOMPLISHMENTS. THIS IS MY FIRST YEAR AS FACULTY AT THE UNIVERSITY
OF WASHINGTON AND ONE OF THE THINGS THAT DREW ME TO THIS UNIVERSITY WAS THE STRENGTH AND VIBRANCE
OF THE EXPERIMENTAL GROUPS HERE INCLUDING AT CENPA THE CENTER FOR EXPERIMENTAL AND NUCLEAR PHYSICS
AND ASTROPHYSICS WHERE OUR LAUREATES WORK. I'M A VERY HEAD-IN-THE-CLOUDS THEORETICAL PHYSICIST
INTERESTED IN QUESTIONS REGARDING FUNDAMENTAL PHYSICS. AND AS SUCH I WANTED TO BE AT A PLACE NOT
ONLY WITH GREAT THEORISTS BUT WHERE GROUNDBREAKING EXPERIMENTAL CONTRIBUTIONS ARE MADE TO KEEP ME
FOCUSED AND GROUNDED, TO BE AT A PLACE WHERE GREAT PHYSICS GETS DONE AND GUIDES OUR THINKING.
THE EXPERIMENTAL CONTRIBUTIONS BY OUR SPEAKERS HAS GIVEN US VALUABLE CONSTRAINTS ON POSSIBLE
SCENARIOS TO EXPLAIN THE DARK ENERGY AND DARK MATTER THAT CONSTITUTE 95% OF THE ENERGY
AND MATTER IN OUR UNIVERSE. THE RESULTS ARE A GUIDING LIGHT FOR US IN A DARK UNIVERSE
KEEPING US FOCUSED AND HELPING US ATTAIN CLARITY AND UNDERSTANDING. WITHOUT FURTHER
ADO, LET ME INTRODUCE OUR THREE LAUREATES.
ERIC ADELBERGER IS A PIONEER IN DEVELOPING
PRECISION INSTRUMENTS FOR FUNDAMENTAL PHYSICS. HE OBTAINED HIS BACHELORS AND PHD FROM
CALTECH RESPECTIVELY IN 1960 AND 1967. HE WAS THEN A POST-DOCTORAL ASSOCIATE AT STANFORD
UNIVERSITY AND AN ASSISTANT PROFESSOR AT PRINCETON UNIVERSITY BEFORE BEING RECRUITED TO THE
UNIVERSITY OF WASHINGTON. HIS HONORS ARE TOO NUMEROUS TO MENTION BUT INCLUDE THE BONNER PRIZE
OF THE AMERICAN PHYSICAL SOCIETY FOR HIS STUDIES OF ISOSPIN AND SYMMETRY BREAKING OF NUCLEI BEFORE
HE TURNED HIS ATTENTION TO GRAVITATIONAL PHYSICS. AS WELL AS MEMBERSHIP IN THE NATIONAL ACADEMY OF
SCIENCES AND THE BREAKTHROUGH PRIZE. JENS GUNDLACH OBTAINED HIS PHD FROM THE UNIVERSITY WASHINGTON IN
1990 AND HAS BEEN AT UW EVER SINCE. HE IS A FELLOW OF THE AMERICAN PHYSICAL SOCIETY AND RECEIVED THE
FRANCIS M. PIPKIN AWARD OF THE AMERICAN PHYSICAL SOCIETY IN ADDITION TO THE BREAKTHROUGH PRIZE. IN
ADDITION TO HIS FOUNDATIONAL WORK IN EXPERIMENTAL GRAVITATIONAL PHYSICS, HE IS AN INSPIRING REMINDER
OF THE UNITY OF SCIENTIFIC APPROACH IN PRACTICE AND HAS A RESEARCH PROGRAM IN BIOPHYSICS ON THE
NANO4 SEQUENCING OF DNA. BLAYNE HECKEL OBTAINED HIS BACHELOR'S AND PHD IN 1981 FROM HARVARD
UNIVERSITY. HE WORKED AS A POSTDOCTORAL AT HARVARD. PROFESSOR HECKEL HAS BEEN AWARDED
THE PRESIDENTIAL YOUNG INVESTIGATOR AWARD, WAS A SLOAN RESEARCH SCHOLAR AND IS A
MEMBER OF THE WASHINGTON ACADEMY OF SCIENCE. FOLLOWING TODAY'S LECTURE, WE WILL HAVE A QUESTION
AND ANSWER WITH ALL THREE HOSTED BY MY COLLEAGUES, PROFESSORS ALVARO CHAVARRIA AND ARMITA . PLEASE
SUBMIT YOUR QUESTIONS AS THEY OCCUR TO YOU IN THE YOUTUBE CHAT BOX OR BY EMAIL TO FPLS@UW.EDU.
YOU CAN FIND QUESTION AND ANSWER INSTRUCTIONS AND INFORMATION ON HOW TO SUPPORT THE UNIVERSITY OF
WASHINGTON'S DEPARTMENT OF PHYSICS IN THE VIDEO DESCRIPTION BELOW. AND FINALLY WITHOUT FURTHER
ADO, IT IS MY GREAT HONOR TO HAVE ALL THREE LAUREATES AS MY NEW COLLEAGUES AND PLEASE JOIN ME
IN WELCOMING THEM THIS EVENING AS WE LOOK FORWARD TO THE WONDERFUL LECTURE BY PROFESSOR
ADELBERGER AND THE PANEL DISCUSSION WITH ALL THREE LAUREATES.
[ APPLAUSE ]
GOOD EVENING. IT IS MY PLEASURE TODAY TO TELL
YOU ABOUT GRAVITY WHICH IS AT THIS POINT, THE BIGGEST OPEN QUESTION IN FUNDAMENTAL PHYSICS. WE
LIVE IN THE BEST OF TIMES AND WORST OF TIMES.
STANDARD MODELS BECAUSE THEY WORK VERY WELL.
THE FIRST STANDARD MODEL IS THE STANDARD MODEL OF PARTICLES. IT SEES THEM . ONE PARTICLE HERE
AFFECTING ANOTHER PARTICLE THERE. IT SHOOTS ACROSS A VIRTUAL PROTON THAT HOOKS ON TO THE CHARGE
OF THIS PARTICLE AND THE CHARGE OF THE OTHER PARTICLE. THAT IS HOW SOMETHING OVER HERE AFFECT
SOMETHING OVER THERE. THIS DIAGRAM IS THE SIMPLEST POSSIBLE ONE. IF YOU DO THE CALCULATION IN THE
REAL WORLD, MANY OF THESE, IT'S A VERY ELABORATE THING. THEY DISCOVERED THAT ALL THE MATTER IN THE
UNIVERSE, THE MATTER WE KNOW ABOUT IN THE UNIVERSE CAN BE UNDERSTOOD IN TERMS OF A COLLECTION OF
12 PARTICLES AND A COLLECTION OF THREE OR FOUR DEPENDING ON HOW YOU LOOK AT IT OF THINGS THAT GO
BACK AND FORTH HERE. THE GOOD NEWS EVEN THOUGH IT IS A COMPLICATED THEORY, YOU CAN CALCULATE
SOMETHING CALLED ELECTRON MAGNETIC MOVEMENT. ONE PART IN 1 TRILLION. IT HAS THE FRAMEWORK FOR
UNIFYING THE DIRECTIONS WHICH SEEMS SO DIFFERENT. IT PREDICTED THE HIGGS BOSON WHICH YOU
PROBABLY HEARD ABOUT. IT TELLS US THE VACUUM IS NOT ACTUALLY EMPTY BUT FILLED WITH
VIRTUAL PARTICLES THAT ARE SWARMING AROUND. THERE IS NO CONVINCING EVIDENCE YET
FOR A BREAKDOWN. I GOT THESE TWO ASTERIX HERE. I WILL COME BACK TO THAT AT THE
END OF THE TALK. IT CANNOT DESCRIBE GRAVITY. IT CANNOT EXPLAIN THE UNIVERSE HAS MUCH MORE MATTER
AND IT THEN ANTIMATTER. WHICH WE KNOW IT DOES. AS YOU JUST HEARD IN THE INTRODUCTION, IT CANNOT
ACCOUNT FOR 95% OF THE CONTENTS OF THE UNIVERSE. THIS IS A TEST. THE ELECTRON BEHAVES LIKE A
LITTLE TINY MAGNET. THESE PEOPLE AT HARVARD HAVE BUILT A TRAP AND TEMPERATURE ONLY A 10th OF A
DEGREE TO ABSOLUTE ZERO WHERE THEY CAN TRAP A SINGLE ELECTRON IN THERE AND HOLD IT FOR MONTHS.
WHILE THEY ARE BUSY MEASURING THE FREQUENCIES OF ELECTRONS COMPLICATED ORBIT IN THIS TRAP.
FOR MEASURING THESE COMPLICATED FREQUENCIES, THEY CAN CONCLUDE THIS MOMENT IS THIS NUMBER RIGHT
HERE. THE NUMBER IN PARENTHESES IS THE UNCERTAIN. THIS IS A PHENOMENALLY PRECISE THING. MANY MORE
COMPLICATED VERSIONS OF THE DIAGRAM THAT I SHOWED YOU. IT COMES OUT AND IT IS QUITE A PHENOMENAL
AGREEMENT. WE ARE RIGHT TO BE PROUD. WE REALLY UNDERSTAND THIS. THE STANFORD LAW OF GRAVITY
IS EINSTEIN'S CLASSIC THEORY OF SPACE AND TIME. GRAVITY IS NOT A FORCE LIKE TAUGHT. INSTEAD
FREELY THROUGH FLOWING OBJECTS ARE FOLLOWING THE SHORTEST PATHS. MATTER TELLS SPACE-TIME HOW
TO CURVE. SPACE-TIME TELLS MATTER HOW TO MOVE. THIS IS A DIFFERENT WAY OF LOOKING AT THE WORLD.
IT PREDICTED THE DEFLECTION OF LIGHT BY THE SUN CORRECTLY. IT HAS SOMETHING CALLED EQUIVALENCE
PRINCIPLE. IT'S BAKED INTO IT. IT IS INHERENT. IT PREDICTED THE GRAVITATIONAL SLOWING OF CLOCKS.
IT PREDICTED BLACK HOLES WHICH ARE AMAZING THINGS. IT PREDICTED GRAVITY WAVES. IT PREDICTED
THE SPEED OF GRAVITY IS EQUAL TO THE SPEED OF LIGHT AND THAT HAS RECENTLY BEEN CHECKED.
THEY AGREE TO A PART IN THE 15th. BAD NEWS. IF YOU TRY TO CALCULATE WHAT HAPPENED
AT THE CENTER OF THE BLACK HOLE, YOU RUN INTO PROBLEMS. IT DOESN'T INCORPORATE
THE UNCERTAINTY PRINCIPLE. IT DOESN'T ACCOUNT FOR SOMETHING CALLED INFLATION. IT CAN'T
EXPLAIN WHY VACUUM ENERGY DOESN'T GRAVITATE. WHEN JOHNNY WHEELER SAYS MATTER, HE
REALLY MEANS MATTER/ENERGY PEERS GRAVITY IS DRIVEN BY MATTER AND ENERGY. WHY DOESN'T
THAT ENERGY GRAVITATE? OBVIOUSLY THIS CAN'T FIT INTO A SCHEME WHERE YOU UNIFY ALL THE FORCES
IN A CONSISTENT WAY OF LOOKING AT THE UNIVERSE.? LET ME SHOW YOU A COUPLE PRECISE TEST HERE. A
BEAUTIFUL PRECISE TEST FOR THE WAY MASS CURVES SPACE-TIME. NASA SENT A SATELLITE TO GO AROUND
MARS. THE SATELLITE IS GOING AROUND SATURN. PEOPLE OBSERVED BEFORE THE MISSION AT ONE POINT A PATH
TO THE EARTH AND SATELLITE PASSED VERY CLOSE TO THE SUN. IT PASSED THROUGH THE SUN AND CAME
OUT ON THE OTHER SIDE. THIS GAVE PEOPLE A VERY WONDERFUL WAY TO SEE HOW THE MASS OF THE SUN WAS
BENDING OR SLOWING DOWN THE LIGHT AS IT PASSED BACK AND FORTH. THE RADIO WAITS BETWEEN
THE EARTH AND THE SATELLITE. THIS PICTURE SHOWS WHAT THEY OBSERVED.
AT THIS POINT IN THE CURVE THESE LITTLE DOTS ARE THE THINGS THAT THEY MEASURE
THIS IS WHAT EINSTEIN TOLD YOU IT OUGHT TO BE. THE WAY THAT MATTER CURVES SPACE-TIME LED TO
PARTS IN 100,000. IT'S A BEAUTIFUL EXPERIMENT. I WOULD LIKE TO GIVE YOU SOME PERSONAL
REMARKS. ONE OF THE GOOD REASONS FOR EXPERIMENTAL'S TO FOCUS ON GRAVITY WHEN LOOKING
FOR CRACKS IN THE MODEL? GRAVITY STANDARD MODEL DOESN'T KNOW ABOUT THE PRINCIPAL AND NO ONE HAS
FIGURED OUT HOW TO PUT IT IN. THEY TRIED HARD. THE UNCERTAINTY PRINCIPLE EXPRESSES A
DEEP TRUTH ABOUT REALITY. I AM PERSONALLY CONVINCED EVENTUALLY IT WILL BE INVOLVED
IN OUR UNDERSTANDING OF GRAVITY. A BREAKDOWN CANNOT BE ACCOMMODATED
BY ADDING A NEW FEATURE. THIS HAPPENED WHEN THEY WERE FOUND MASSLESS. IT
COULD BE INCORPORATED INTO IT. GRAVITY STANDARD MODEL IS DIFFERENT. IT IS VERY HARD TO GAUGE IT.
GRAVITY HAS ALREADY SHOWN US SOME BIG SURPRISES. FINALLY IT IS FUN AND CAN BE
DONE BY SMALL UNIVERSITY GROUP. A BRIEF HISTORY OF THE UNIVERSE. THE BIG BANG
AND INFLATION ARE HAPPENING HERE. FOR THE NEXT 400,000 YEARS YOU CAN'T LOOK AT WHAT'S GOING ON
WITH LIGHT OR ANYTHING. THERE IS SUCH A HOTBED OF CHARGES AROUND IN HERE, LIKE CAN'T GET
THROUGH. AFTER 400,000 YEARS, OF THE PLUS CHARGES COMBINED WITH THE MINUS CHARGES.
IF WE LOOK AT THE LIGHT STARTED OUT TODAY, IT HAS BEEN STRETCHED OUT, BROUGHT TO LOWER
FREQUENCIES BY THE EXPANSION OF THE UNIVERSE. NASA HAD PUT UP A SATELLITE AND LATER THE
EUROPEANS. IT COMES FROM ALL DIRECTIONS. IS EXTREMELY UNIFORM. ALMOST PERFECTLY UNIFORM AS
WE WILL SEE. IT TOOK A LONG TIME FOR THINGS LIKE STARS TO FORM. PEOPLE THOUGHT IT WAS GOING TO
SLOW DOWN. GRAVITY THROUGH EVERYTHING TOGETHER. BIG SURPRISE, IT'S NOT TRUE. WHAT'S HAPPENING
NOW IS THAT THE UNIVERSE IS EXPANDING. THAT'S NO EXPLANATION FOR THAT
IN THE STANDARD MODEL RIGHT NOW. THIS IS A PICTURE OF THE UNIVERSE 4000 YEARS
AFTER THE BIG BANG. THIS IS A MAP OF THE TEMPERATURES OF RADIATION AND THE LITTLE DOTS
ARE REPRESENTING THE TEMPERATURES IN THIS REGION. THEY ARE TINY. THESE LITTLE DOTS CORRESPOND
THE UNIVERSE WAS VERY UNIFORM AT THAT POINT. YOU FIND THIS REMARKABLE RESULT WHICH HAS BEEN
HINTED AT SEVERAL TIMES. EVERYTHING WE KNOW ABOUT AND HAVE EXPERIENCED. ALL THE REST OF IT
IS STUFF WE REALLY HAVE NO IDEA WHAT IT IS. WE KNOW IT'S THERE BUT WE DON'T KNOW WHAT IT IS.
WHY DO WE KNOW THERE IS THIS MUCH DARK MATTER? IT'S AN INTERESTING ARGUMENT. IF THERE WERE NOT
THIS DARK MATTER, WE COULDN'T BE HERE TODAY. GRAVITY WASN'T STRONG ENOUGH TO SURVIVE AND
BEGIN TO CONDENSE. THE ONLY WAY THAT WORKED WAS THAT THERE HAD TO BE SOME PARTICLES THAT
WERE DISTURBED BY THIS RADIATION. THAT COULD LATER ON DRAW IN THE ORDINARY MATTER. IT HAS
TO ACCOUNT FOR THE EXPANSION OF THE UNIVERSE. I WHAT ABOUT THE OTHER SUBJECT DEAR TO MY HEART.
IS CALLED THE EQUIVALENCE PRINCIPLE. IT IS EASY TO STATE AND REALLY HARD TO TEST. ALL SUBJECTS, ALL
OBJECTS SUBJECT ONLY TO GRAVITY WILL FALL WITH IDENTICAL ACCELERATIONS. TESTING THE STATEMENT
IS A DIFFERENT STORY. WE HAVE VERY POWERFUL TECHNIQUES WHICH I WILL MENTION LATER. THE HOOKER
HERE IS THE UNIFORM GRAVITATIONAL FIELD. IT IS MUCH HARDER TO MAKE A SUFFICIENT GRAVITATIONAL
FIELD. WE SPENT A LOT OF TIME WORKING ON THAT. LET'S TALK ABOUT WHAT WE MEAN BY NONUNIFORM
GRAVITATIONAL FIELD. OR TITLE FORCES. ALL DIFFERENT WORDS FOR THE SAME THING. SUPPOSE YOU
HAVE A BOX AND HE STUCK IT ON THE SURFACE OF THE EARTH. YOU RELEASE FOR LITTLE SPHERES SHOWN IN
THIS CARTOON HERE. YOU WATCH THEM FALL. YOU WILL FIND OUT THE ACCELERATIONS OF EACH OF THESE FOUR
SPHERES IS DIFFERENT. THE ONE CLOSEST TO THE EARTH HAS THE HIGHEST ACCELERATION
BECAUSE IT IS CLOSEST TO THE EARTH. THIS ONE IS FARTHEST FROM THE EARTH. IT HAS THE
WEAKEST AND LEAST ACCELERATION. THESE TWO HOMICIDE ACTUALLY ARE COMING TOGETHER BECAUSE THEY ARE ALL
FORMING TOWARDS THE CENTER OF THE EARTH. NOW THIS IS THE PICTURE BUT IN THE REAL WORLD WE ARE NOT
ON A SPIRITUAL EARTH. WE ARE LIVING ON EARTH THERE IS WATER AND LAND. IT'S COMPLICATED. THESE
GRADIENTS ARE MUCH BIGGER THAN YOU WOULD DEDUCE FROM THIS. OUR PRECISION IS SO GOOD. A TEST REGION
HERE CAN BE CONSIDERED SUFFICIENTLY UNIFORM. IT HAS TO GET SMALLER AND SMALLER. YOU NEED
TO HAVE A VERY SMALL REGION. IT IS SURPRISING, BUT THE SIZE OF THE SMALL REGION WHERE
YOU KNOW IT IS UNIFORM ENOUGH, IT IS A CUBE . YOU HAVE TO GET REALLY EFFECTIVE AND
SMALL TO HAVE A UNIFORM ENOUGH FIELD.
LET'S GO TO THE TOPIC ABOUT HOW DO YOU MEASURE
TINY ACCELERATION DIFFERENCES? IT IS DONE WITH PENDULUMS. THESE HAVE PLAYED AN IMPORTANT ROLE
IN FUNDAMENTAL PHYSICS THEY ARE MARVELOUSLY TINY DIFFERENCE. YOU HAVE THINGS WITH TWO THINGS ON
THE END AND ANOTHER SPEAR HERE WHERE YOU CAN PUT CHARGES AND BY DOING THE CHARGES YOU CAN PUSH
THEM APART OR PULL THEM TOGETHER DEPENDING IF THE CHARGES ARE LIKE OR UNLIKE. IT IS JUST ABOUT TO
BREAK. YOU HAVE AN EXTREMELY SOFT STRING FOR THIS. A VERY TINY FORCE WILL PRODUCE A MEASURABLE TWIST
IN THAT BAR. CLEARLY THIS IS APPLICATIONS TO STUDY GRAVITY. IT IS SO TERRIBLY WEAK AND YOU NEED
SOMETHING SENSITIVE TO SEE THE LITTLE THINGS. AND HERE'S THE FIRST TIME WE ARE GOING
TO TALK ABOUT ACTUALLY TESTING. THIS IS A FAMOUS EXPERIMENT DONE. HE WAS INTERESTED
IN GRAVITY BUT HE WAS INTERESTED IN IT FOR A PARTICULAR REASON. DEFINE VALUABLE MINERALS IN THE
GROUND WHICH ARE TYPICALLY HEAVIER THAN THE OTHER STUFF. HE WAS LOOKING FOR GRAVITY GRADIENTS. HE
LEFT THIS VERY SOPHISTICATED INSTRUMENT, ACTUALLY. THIS WAS MET TO MEASURE GRAVITY GRADIENTS. HE
WAS SMART ENOUGH AND REALIZED THIS TECHNIQUE WAS SO POWERFUL, THAT HE COULD USE THIS INSTRUMENT
WHICH WASN'T DESIGNED TO DO IT. IT IS OPTIMIZED TO FIND STUFF IN THE GROUND. JUST BY APPLYING THIS
AND BEING CAREFUL, HE WAS ABLE TO SHOW AND MAKE AN INCREASE IN THE PRECISION. ALL MATERIALS HE
TRIED, HE TRIED A WHOLE BUNCH. THEY FELL WITH THE SAME ACCELERATION. AROUND THE 50s OR 60s, BOB
DICKEY AT PRINCETON DECIDED IT WAS TOO IMPORTANT IMPORTANT OF A PRINCIPAL TO RELY ON THE EXPERIMENT
WHICH WAS NOT REALLY OPTIMIZED. HE REALIZED ONE OF THE PROBLEMS OF THIS,
IN ORDER TO SEE AN EFFECT HERE, HE HAS TO LOOK THROUGH A TELESCOPE AND MIRROR AND
TO SEE HOW THAT MIRROR IS POINTED. MANY TURNS THE APPARATUS AROUND 180 DEGREES AND SEES HOW THE
MIRROR IS POINTED. IF THERE IS A CHANGE IN THE ANGLE, THAT IS THE SIGN OF A VIOLATION OF THE
PRINCIPLE OF EQUIVALENCE. TO MAKE USE OF IT, YOU HAVE TO TURN AROUND 180 DEGREES. IT IS
OBVIOUSLY NOT THE BEST WAY TO MEASURE TINY THINGS. HE WAS SITTING HERE LOOKING AT HIS
TELESCOPE. HE WAS A CORPULENT PERSON. HIS OWN GRAVITY GRADIENTS HAD AN EFFECT ON THIS. THE
THING TO DO IS LOOK AT IT FALLING TOWARD THE SUN AND NOT TOWARDS THE EARTH. THE SUN IS GREAT
BECAUSE IT'S VERY FAR AWAY. HIS APPARATUS IS ROTATED FOR FREE AS THE EARTH ROTATES EVERY
24 HOURS. YOU SIT THERE AND WAIT 12 HOURS. HE HAD SOPHISTICATED ELECTRONICS AND EVERYTHING.
HE FOUND THAT ALL THINGS FELL WITH THE SAME ACCELERATION WITH THIS PRECISION. HE WAS 280
TIMES MORE PRECISE. DICKEY WAS SURPRISED ACTUALLY. HE EXPRESSED CONCERNS ABOUT THE EFFECTS OF
TEMPERATURE VARIATIONS ON THE INSTRUMENT. IT WAS BURIED IN THE HOLE ON THE PRINCETON UNIVERSITY
CAMPUS. IT WAS DONE ROUGHLY 10 TIMES BETTER BY AN EXPERIMENT IN MOSCOW. THERE IT SAT. IT REALLY
WORKS AND LET'S LEAVE IT ALONE. THERE ARE BETTER THINGS TO DO. A LONG TIME SINCE HE GOES AND
LOOKS AT THE EXPERIMENT. HE ANALYZES IT IN A WAY. THE VERTICAL AXIS HERE IS DIFFERENT FROM
THE PAIRS OF MATERIALS LISTED. ON THIS AXIS, THEY COULDN'T KNOW ABOUT AND IT WAS THE NUMBER
OF NEUTRONS PLUS PROTONS PER GRAM OF MATERIAL. HE PLOTTED THESE UP AND SEES A NICE STRAIGHT
LINE HERE. I FOUND EVIDENCE FOR A NEW QUANTUM FORCE. THE CHARGE WAS THE NUMBER OF PROTONS
PLUS NEUTRONS. THE FORCE DIDN'T FALL OFF THE WAY GRAVITY IN ELECTROMAGNETISM FALLS OFF. IT
BECAME VERY WEAK FOR SEPARATIONS GREATER THAN A RANGE BETWEEN 30 METERS AND A KILOMETER.
THIS BEHAVIOR COULD OCCUR IF THE EXCHANGE HAD A TINY MASS. IT WASN'T MASSLESS. IF THE
PARTICLE HAD TINY MASS, IT WOULD FALL OFF JUST LIKE THIS. THERE WAS NO ROOM FOR SUCH IN THE
STANDARD MODEL. HE COULD EXPLAIN WHY DICKEY DIDN'T SEE IT. DICKEY WAS LOOKING FOR SOMETHING
THAT DIED OFF LONG BEFORE HE GOT TO HIM. THAT'S HOW WE GOT STARTED. THIS LOOKED
INTERESTING. I WAS VERY SKEPTICAL WHEN IT WAS TRUE. YOU COULDN'T TELL IT WASN'T TRUE. IT DIDN'T
SMELL RIGHT. YOU START THINKING ABOUT TESTING IT. THIS IS A PICTURE, A CARTOON OF THE EARTH. I
GREATLY EXAGGERATED IT'S CENTRIFUGAL FORCE. THE EARTHS SHAPE IS THIS OBJECT WERE EVERY POINT
ON IT, THE SON OF THE GRAVITATIONAL FIELD IN THE CENTRIFUGAL FORCE PUSHING IT OUT ADD UP AND THIS
IS WHERE WATER WOULD BE. SUPPOSE YOU ARE LOOKING FOR A FORCE THAT HAD A RANGE OF A KILOMETER
OR SO. THIS LITTLE SHADED AREA REPRESENTS THE AMOUNT OF MATTER WITHIN THE RANGE OF THE FORCE.
IT PULLS STRAIGHT DOWN ON THE PENDULUM. THEY MEASURE HORIZONTAL FORCES. YOU COULDN'T SEE IT
IN THE MIDDLE OF A FROZEN LAKE OR SOMETHING. THE GRAVITY GRADIENTS ARE RELATIVELY
SMALL HERE. THE PLACE TO MAKE A BIG AFFECT IS TO GO TO THE BOTTOM OF THE CLIFF IN THE
NORTH CASCADES OR SOMETHING. IT HAS A COMPONENT IN THE HORIZONTAL DIRECTION. THIS ALSO HAS
BIG GRADIENTS IN THE GRAVITY FIELD. IT'S LIKE BEING A SCUBA DIVER. YOU ARE TOLD THE SUNKEN
TREASURES ARE IN A PLACE WITH A LOT OF SHARKS. THIS WAS THE HUMBLE BEGINNINGS.
AFTER WE HEARD ABOUT THE FIFTH FORCE, WE DECIDED TO TEST IT AND RECRUITED A BUNCH OF
GRAD STUDENTS TO MAKE IT HIS THESIS PROJECT. WE WERE SOON JOINED BY FIVE OTHERS. WE'VE NEVER DONE
GRAVITATIONAL EXPERIMENTS WHICH WAS A GOOD THING ACTUALLY. WE APPROACHED IT WITH AN OPEN MIND.
AND ONE MONTH, WE INVENTED THE MAIN FEATURES. WE PUT THE BALANCE ON A CONTINUOUSLY ROTATING
TURNTABLE. WE COULD PICK THE PERIOD. THAT IS A TERRIBLE FREQUENCY. THE TEMPERATURE,
ELECTRIC POWER LINE. THE VIBRATIONS, ETC. WE CAN BOOST THIS LESS THAN AN HOUR WHEN THINGS
ARE MUCH QUIETER. THE ONLY THING WORSE THAN ONCE A DAY, IT'S ONCE A YEAR. WE HAD AN IDEA THAT WE WANT
TO MAKE IT AS HARD AS POSSIBLE FOR ANYTHING ELSE TO SEE AND TELL WHICH OF OUR TEST BUDDIES .
HERE IS CHRISTOPHER PUTTING FOR TEST BUDDIES. TWO OF THEM ARE COPPER AND TWO OF THEM ARE
BERYLLIUM. YOU PROBABLY KNOW COPPER IS MUCH DENSER THAN BERYLLIUM. THAT WAS DELIBERATE.
RADIATION PRESSURE DOESN'T ACT DIFFERENTLY. THE COPPER RUINS ARE HOLLOW INSIDE. EVERYTHING IS
GOLD COATED IN THE SYSTEM FOR MEASURING IS A LASER COMING DOWN AND YOU CAN'T SEE THE SUSPENSION. IT
IS BEHIND THE SUPPORT ROD. EVEN THERE YOU COULDN'T SEE IT. IT IS SO FINE. THEN YOU ARE THINKING WHERE
SHOULD WE GO TO DO THIS EXPERIMENT? WE RAPIDLY CONVINCE HERSELF THE BEST THING TO BE IS RIGHT
HERE IN THE NUCLEAR PHYSICS LAB. IT WAS CARVED OUT OF A HILLSIDE. IT HAD A LITTLE BIT OF THE
STRUCTURE THAT YOU WANT. WE HAD A WELL-EQUIPPED LABORATORY. THAT GOVERNED EVERYTHING.
WE WORKED AND WORKED FOR 11 MONTHS. WE WERE REALLY EXCITED ABOUT THIS. WE SUBMITTED THE PAPER
SHOWING THIS FORCE DIDN'T EXIST. THIS IS WHAT HE DEDUCED FROM THE EXPERIMENT. THIS AXIS IS THE
FRACTIONAL DIFFERENCE IN PARTS PER BILLION AND ACCELERATION OF THINGS. THIS CORRESPONDS TO THAT
QUANTITY. IT DIDN'T EXIST. THERE WAS A POINT HERE. HERE WE REALIZED THIS TECHNIQUE THAT WE HAD
DEVELOPED, WAS ACTUALLY USEFUL FOR ASKING A GIN YOU'LL QUESTION. COULD THERE BE OTHER
THINGS? YOU COULDN'T SAY THERE WEREN'T. IT IS AN AREA NO ONE HAD ACTUALLY LOOKED
CAREFULLY. WE SET OUT TO A PROGRAM WE WOULD TEST BOTH STANDARD MODELS AT THE SAME TIME BY
IMPAIRING DIFFERENT THINGS FALLING WITH THE GREATEST POSSIBLE PRECISION IN THE LAB ON A
ROTATING PALLET. SINCE THESE DAYS, OUR SENSITIVITY HAS IMPROVED BY 5000. THAT'S A BIG AMOUNT. LET ME
JUST TELL YOU A LITTLE BIT ABOUT REALITY. OKAY. YOU START OUT THINKING THE HARDEST PART IS
GETTING SENSITIVE TO THESE TINY DIFFERENCES IN ACCELERATION. IN FACT THAT
IS THE EASIEST PART OF IT. OKAY. THE HARD PART IS UNDERSTANDING THE SYSTEMATIC
EFFECTS THAT CAN GIVE YOU SIGNALS. THAT IS TOUGH. OKAY. WHAT KIND OF THINGS CAN DO IT? WE ALREADY
TALKED ABOUT GRAVITY. OKAY. YOU THOUGHT YOU WERE TESTING THE HUMANS PRINCIPLE. OKAY. THIS IS
SOMETHING YOU CAN HANDLE REGULAR RIGOROUSLY. THESE GRADIENTS ARE VERY CONTROLLING. THIS
TURNTABLE HAS TO BE AWFULLY GOOD. OKAY. THE ORIGINAL TURNTABLE WASN'T THAT GOOD BUT THEY ARE
GETTING BETTER AND BETTER. OKAY. IT HAS TO ROTATE AT A VERY UNIFORM RATE. IF IT SPEEDS UP AND SLOWS
DOWN AND LOOKING AT IT WITH AN OPTICAL SYSTEM, IT'S GOING TO LOOK TO YOU LIKE THE PENDULUM
IS DOING SOMETHING FUNNY. MAGNETIC IMPURITIES, DICKEY POINTED OUT TO HOW TINY IT COULD
HAVE SCREWED THE WHOLE THING UP. OKAY. THESE THERMAL EFFECTS THAT DICKEY TALKED ABOUT
AS WELL, THESE ARE REALLY TRICKY TO UNDERSTAND IN DETAIL. THE ONLY THING TO DO OR CERTAINLY THE
BEST THING TO DO IS HAVE ULTRA STABLE THERMAL ENVIRONMENT. THIS PART OF THE APPARATUS IS THE
SAME TEMPERATURE AS THAT PART. FOR STUDIES YOU HAVE TO KNOW THE EXACT GEOMETRY OF THE INSTRUMENT.
THAT IS A MAJOR ISSUE. I WILL MENTION THAT. HERE'S THE PENDULUM OF OUR LATEST TEST. THIS
IS ABOUT THE SIZE OF MY FIST. THAT IS DESIGNED TO MAKE IT LESS OF A GRADIENT. IT LOOKS VERY
COMPLICATED. IN A CERTAIN SENSE, IT IS ALMOST A SPHERE. YOU CAN'T SEE IT IN THIS PHOTO BECAUSE
IT'S SO SKINNY. IT IS A VERY SYMMETRICAL DESIGN. YOU CAN'T TELL WHICH TEST BODY IS WHICH. OKAY. IT
IS SURROUNDED BY ELECTRICAL MAGNETICS SHIELDING. THIS THING, IF YOU GAVE IT A LITTLE TWIST AND LET
IT GO, IT TAKES AROUND 800 SECONDS TO MAKE ONE COMPLETE OSCILLATION. OKAY. THE FACTOR IS 6000.
IF YOU TOOK THAT LITTLE THING AND TURNED IT BY 10 DEGREES OR SOMETHING AND LET IT GO, YOU COME BY
20 DAYS LATER. EVERYTHING IS MADE VERY PRECISELY. THIS IS THE TURNTABLE. BY NOW, WE'VE UNDERSTOOD
A LOT ABOUT GRAVITY GRADIENTS. IT'S ALSO TRUE THE ROTATION AXIS MUST CORRESPOND DOWN. IT RESTS
ON THREE FEET. THESE ARE THERMAL EXPANSION FEET. IT VARIES DURING THE DAY AND THE WEATHER
AND EVERYTHING. THAT IS A PROBLEM BECAUSE YOU CAN'T KEEP THE ROTATION ALIGNED WITH DOWN
AT THE PENDULUM. OKAY. WHAT THIS HAS TO DO TO TAKE INTO ACCOUNT WHAT THE VARIATION OF THE
FLOOR, IT HAS TO EXPAND OR CONTRACT BY ABOUT 10,000TH OF AN INCH. VERY SMOOTHLY AND GENTLY,
IT ADAPTS. WHAT YOU SEE WHEN YOU MEASURE THE TILT AND IT IS 1/3000 OF A DEGREE. CHANGING WITH
TIME BECAUSE OF FOR TILT IS CHANGING AND THAT IS WHAT MAKES THIS PATTERN CHANGE. WHEN YOU
DO THAT, IT IS BEAUTIFULLY STABLE. WE MEASURE THE GRADIENTS REPLACING OUR NORMAL PENDULUM. BASICALLY
IT IS A WAY OF SUPPORTING SOME LITTLE TINY BALLS. THEY FIT IN WELL AND DETERMINED PLACES. DEPENDING
WHERE YOU PUT THOSE BALLS, YOU PICK OUT A CERTAIN COMPONENT OF THE GRADIENT FIELD. THIS PROVIDES YOU
WITH A SYSTEMATIC WAY OF CANCELING THE GRADIENTS. THIS SHOWS WHAT YOU SEE WHEN YOU ARE MEASURING THE
GRADIENTS. THIS IS A TIME WHICH IS ANGLED FOR THE TURNTABLE. YOU SEE THIS NICE SIGNAL HERE VERY
WELL RESOLVED. ONCE YOU KNOW WHAT THEY ARE, YOU CAN DESIGN SOMETHING THAT CANCELS THE GRADIENTS.
IT'S VERY CAREFULLY SHAPED AND ENGINEERED SO THAT CANCELS THE GRADIENT RIGHT HERE. YOU CANNOT MAKE
GRAVITY GO AWAY BUT YOU CAN CANCEL THE GRADIENT IN A TINY REGION. THIS WHOLE THING IS MOUNTED ON
A BIG TURNTABLE. SHE DID TAKE HER DATA AND LESS TO SEE IF THE GRADIENT CANCELLATION IS STILL WHAT
IT USED TO BE. IT WAS NEARLY WHAT IT SHOULD BE BUT IT KEPT TAKING DATA. IT WAS EARLY NOVEMBER AND
THE RAINS CAME. YOU CAN'T STOP THE WEATHER BUT YOU CAN TUNE AWAY THE PENDULUM SENSITIVITY BY TAKING
THOSE BIG THINGS, ROTATING THEM 180 DEGREES AND THEY DOUBLE IT. MAKE IT BIG. MAKE THE
PENDULUM SO DOESN'T RESPOND TO THAT GRADIENT. YOU CAN CANCEL OUT THE IMPERFECTIONS OF THIS
THING. IT IS SUCH A DELICATE LITTLE ADJUSTMENT. WHAT IS SHOWN HERE IS A FREQUENCY ANALYSIS OF
THE PENDULUM TWIST SIGNAL. ON TOP HERE IS THE FREQUENCY IN TERMS OF THE ROTATION FREQUENCY OF
THE TURNTABLE. IT SIGNAL WOULD BE AT ONE HERE. THESE OTHER ONES ARE SHARP PEAKS HAVE SOMETHING
TO DO AT THE ROTATION FREQUENCY. THAT DOESN'T CHANGE ANYTHING IN THE TURNTABLE. ALL MOVING AS
FAST AS THE MINUTE HAND ON THE END OF A CLOCK. I AM NOT GOING TO CHANGE GEARS ENTIRELY. THERE
IS AN INTERESTING LINK SCALE YOU CAN DEDUCE FROM THE OBSERVED DENSITY OF DARK ENERGY.
YOU CAN TURN THAT INTO A LENGTH. THIS IS AN AMAZING THING THAT REQUIRES SEVEN EXTRA
AND HUNDREDS OF EXTRA NORMALLY MASSLESS PARTICLES. ALL OF THESE COULD SHOW
UP AS VIOLATION OF THE SQUARE LOG. IT SHOWS WITH THESE EXTRA DIMENSIONS ARE. EVERY
POT IN SPACE HAS THESE EXTRA SEVEN DIMENSIONS. HE NOTICED THAT EXTRA DIMENSIONS OF STRING
THEORY WERE LARGE COMPARED TO THIS. IT WOULD EXPLAIN WHY GRAVITY IS SO WEAK. STRING THEORY IS
NOT ONLY A THEORY OF LITTLE STRINGS BUT A THEORY OF SURFACES AND SO ON. THEY ARE ASSOCIATED WITH
EVERYTHING BUT GRAVITY HAVE CHARGES ON THE END THAT STICK THEM TIGHTLY TO THE SURFACE.
THE PARTICLE OF GRAVITY COUPLES EVERYTHING. IT DOESN'T HAVE ANY CHARGE. IT IS FREE TO
TRAVEL EVERYWHERE. WITH THIS ACCESS HERE, THAT IS EXTRA DIMENSIONS. THIS PLANE IS WHERE WE
ARE STUCK. THE EXPLANATION WHY GRAVITY IS SO WEAK, MOST HAVE GONE OFF INTO THIS OTHER PLACE
THAT WE CAN GO. THESE EXTRA DIMENSIONS WOULD HAVE NO EFFECT ON ANYTHING ELSE.
WE ARE ALL STUCK TO THIS VERY TIGHTLY. HERE IS WHAT WAS KNOWN. THAT'S WHERE THEY SAID
WE SHOULD GO TO SEE THE TRUE STRENGTH OF GRAVITY. THAT'S A REALLY EXCITING PICTURE. THIS SHOWS THE
COMPARISON OF A PREVIOUS WELL-KNOWN EXPERIMENT FOR TESTING. NOTICE HOW MUCH MORE SYMMETRICAL
AND NOTICE HERE WE HAVE A CONTINUOUSLY ROTATING TRACTOR UNDERNEATH THE PENDULUM. THERE
ARE A WHOLE BUNCH OF HOLES IN THEIR. IF THERE HADN'T BEEN ANY HOLES IN THE
PENDULUM AND ANY IN THE ROTATING TRACTOR, IT ROTATED AND WILL KEEP ON PULLING DOWN
SAME AS ALWAYS. BECAUSE OF THESE HOLES, GRAVITY HAS A CHANCE TO PULL IT SIDEWAYS. GRAVITY
AS YOU TURN THIS THING VERY CAREFULLY AND SLOWLY, TWO RINGS OF 21 HOLES. YOU WOULD EXPECT GRAVITY
TO TUG IT ONE WAY OR THE OTHER. THAT IS A REALLY SWEET IDEA. THE FORCE IS VERY WEAK. TO SEE THINGS
HAPPENING, YOU HAVE TO USE LITTLE OBJECTS. WE HAVE TWO CENTIMETERS ICE OBJECTS HANGING FROM AND
YOU TRY TO LIGHT THINGS UP. IT HAS TO BE RIGID. THERE'S THIS THING YOU DON'T KNOW ABOUT AND IT IS CALLED THE PATCH EFFECT. LITTLE
CRYSTALS THAT MAKE IT MICRO ORIENTED, IT VARIES DEPENDING ON WHAT YOU'RE LOOKING
AT. I NEVER LEARNED ABOUT THIS IN GRAD SCHOOL. ONE LITTLE SPECK OF DUST GETTING
BETWEEN HIS PLATES, IT'S OVER. THIS SHOWS A PICTURE OF THE APPARATUS. IT'S A
BEAUTIFUL THING. YOU CAN RECOGNIZE THAT. OUR LAST EXPERIMENT IS AN ULTIMATE VERSION SO TO SPEAK
AND THE PATTERN IS 50% TRANSPARENT AND METAL. IT HAS 120 SPOKES ON THE INSIDE AND 18 ON THE
OUTSIDE. THIS GEOMETRY HAS AN ANALYTIC SOLUTION. IT IS ANALYTIC. THE FASTER THE GRAVITATIONAL
FORCE DIES OFF AS YOU SEPARATE. WE ARE DOING TWO EXPERIMENTS. TESTING HOW IT FALLS OFF WHICH
IS MORE SLOW THAN SOMETHING WITH 120 HOLES. THIS HAS A NICE FEATURE FOR SOMETHING
NEW HAPPENING. THIS SHOWS IT PICTURE. IT WAS DONE TWICE BY TED COOK AND THEN BY JOHN
LEE. WE HAVE THE THREE LITTLE SPHERES HERE. THE ATTRACTOR SITS UNDERNEATH. IT SPEEDED UP BY A
FACTOR OF 1000. IT HAS TO DO WITH THE COMBINATION OF THE SLOW VARIATION. THE RATIO OF THE SLOW
GIVES YOU THE REAL KEY INFORMATION THAT YOU NEED. HE DIDN'T HAVE THIS THING TWISTING BACK
AND FORTH BECAUSE HE'S HONEST. IT'S TINY. THE ANGLES WE ARE MEASURING OUR EQUIVALENT
TO PUTTING A METER STICK ON THE MOVE AND HOW BIG DOES THAT METER STICK LOOK TO YOU?
THAT IS THE KIND OF ANGLE WE ARE TALKING ABOUT. THE DATE OF THE INDEPENDENTLY TOOK, THE SIGNAL
THAT VARIES 120 TIMES FOR THE PENDULUM. IT IS THE THIRD HARMONIC OF THE SIGNAL. SUPPOSE YOU
COULD CUT A DOLLAR BILL INTO 1 TRILLION EQUAL SIZED PIECES. IT'S IMPOSSIBLE. YOU COULD WEIGH
ONE OF THOSE PIECES WHICH IS EVEN MORE IMPOSSIBLE. IT CORRESPONDS TO A TWISTING FORCE
AND IT IS PHENOMENALLY SENSITIVE. THIS SHOWS WHAT WE CAN SAY HAPPENS AT SHORT
DISTANCES. IT VARIES BETWEEN A MILLIMETER AND 20 MICRONS. HERE IS SOMETHING THAT IS
GRAVITATIONAL STRENGTH AND SOMETHING THAT IS 1000. WE HAVE A WHOLE GRAVEYARD OF PROPOSALS.
WE CAN TELL YOU SOME OF THESE PARTICLES THEY ARE INHERENT. WE CAN SAY THE LARGEST
MODEST HAVE A COUPLE OF RADIUS OF 30 MICRONS. THIS PLOT HERE SUMMARIZES EVERYTHING WE DONE.
THIS IS A HUGE REGION WE'VE EXPLORED. THIS IS 1 BILLION TIMES WEAKER THAN THE STRENGTH OF GRAVITY.
THIS IS A THIRD THE DIAMETER OF YOUR HAIR. THE DISTANCE TO YOUR SON. WE'VE COVERED A HUGE
REGION AND THERE'S NOTHING IN THE STANDARD MODEL OF GRAVITY WE CAN DETECT. THERE IS NEW PHYSICS
FROM OTHER EXPERIMENT THAT IS ASSOCIATED. IT IS BASICALLY MEASURING THE SAME KIND OF THING.
INSTEAD OF THE ELECTRON, IT IS 200 TIMES HEAVIER CALLED THE NEW TOWN. HERE IS THE THEORY. NOW THERE
IS NOT THIS BEAUTIFUL AGREEMENT. IT IS PROBABLY A HINT OF SOMETHING NEW. THEY WOULD EXPLAIN A
LONG- STANDING PUZZLE CALLED THE DATA PERIMETER. IS ALSO THE LEADING CANDIDATE FOR DARK
MATTER. THIS LOOKS FOR THE AXION'S CONVERTING IN A VERY BIG MAGNETIC FIELD. A CELL PHONE ON
MARS COULD PICK UP FOUR BARS OF SERVICE FROM HERE. OUR COLLEAGUES ARGUE THE THEORY OF THE
ELECTRON COULD REVEAL THE EFFECT OF THE QUANTUM MECHANICAL PART THAT CARRIES THE GRAVITY
FOR US. PEOPLE ARE PROPOSING TO COOL A PAIR OF TINY PARTICLES TO LOOK FOR THE EFFECTS OF THE
GRAVITATIONAL PARTICLES. A FAMOUS EUROPEAN THEORISTS ONCE COMPARED DEAREST.
[ APPLAUSE ] STRUCK THANK YOU , ERIC, FOR A WONDERFUL LECTURE.
WE WILL GO TO THE DISCUSSION THAT PEOPLE ARE SUBMITTING ON THE YOUTUBE CHAT BOX.
THE FIRST QUESTION IS ACTUALLY FROM ME. WE HEARD FROM THE PROFESSOR ABOUT MANY
MEASUREMENTS OF ZERO. WE LOOK FOR EFFECTS BEYOND GRAVITATIONAL., AND WE SEE NOTHING.
WE ARE ACTUALLY MEASURING IT.
WE ARE MEASURING BIG G .
YOU CAN CORRECT ME BECAUSE I AM GOING TO
THE QUESTION ABOUT BIG G. YOU DO HAVE MET A MEASUREMENT SINCE THE YEAR 2000. THERE HAS
ONLY BEEN --IS HAS BEEN MATCHED RECENTLY, THE MEASUREMENT OF BIG G. I WOULD LIKE TO
KNOW THE HISTORY OF THAT MEASUREMENT.
OKAY. I WAS INVOLVED IN THE EXPERIMENT
IN HIGH SCHOOL. THAT'S REALLY FUNNY. THE BIG G EXPERIMENTS , AS YOU MAY HAVE SEEN ITS IN
CLASSROOMS HERE OR ELSEWHERE, THE THING THAT SITS IN THE CORNER . WE HAD ONE OF THOSE IN OUR HIGH
SCHOOL WE ASKED OUR TEACHER, CAN WE MEASURE BIG G? WE DID IT AND GOT ROUGHLY 6.67 TIMES 10 MINUS 10
CUBED DIVIDED BY KILOGRAMS OF THE SECOND SQUARE. ONE THING WAS WRONG . THE EXPONENT. IT IS 10 MINUS
11. HE WAS REALLY HAPPY WE GOT ROUGHLY THE 6.67. THE EXPONENT WAS WRONG. IT TELLS YOU HOW HARD
THESE THINGS ARE. HOW MANY EFFECTS THERE ARE THAT CAN FOOL THIS MEASUREMENT. AROUND THE YEAR 2000
OR LITTLE BEFORE THAT, THERE WAS A BIG CONTROVERSY ABOUT BIG G BECAUSE THERE WERE A WHOLE BUNCH
OF MEASUREMENTS THAT WERE ALL OVER THE PLACE. UP TO ALMOST A PERCENT AWAY FROM THE ACCEPTED
VALUE. THIS LOOKS LIKE A SITUATION , A GREAT TENSION. YOUR PEOPLE POSTULATING ALL KINDS OF
THEORIES THAT YOU COULD HAVE IN ORDER TO EXPLAIN THAT. AT THE SAME TIME, I WAS WORKING ON THE
EQUIVALENCE SENSIBLE TEST. ERIC JUST MENTIONED, WE MEASURED THE GRADIENTS VERY CAREFULLY. IN
THE GRADIENT MEASUREMENT, THERE IS FROM A, I REALIZED THE THING, THE BIGGEST
UNCERTAINTY IN PREVIOUS MEASUREMENTS HAD BEEN WITH HOW YOU MEASURE THE MASS DISTRIBUTION
OF THE SMALL PENDULUM THAT SITS INSIDE THE BIG G EXPERIMENTS , THE CAVENDISH EXPERIMENT
THAT SITS IN THE CORNER OF THESE CLASSROOMS. WHAT I REALIZED WAS THAT THERE IS A BEAUTIFUL
CANCELLATION THAT EVERYONE CAN EXPLOIT WHERE THE MOMENT OF INERTIA CANCELS EXACTLY
AGAINST A GRAVITATIONAL MOMENTS THAT WE HAVE UNDERSTOOD VERY WELL IN OUR
GRAVITY GRADIENT MEASUREMENTS. IT TOTALLY ELIMINATED THAT UNCERTAINTY. THEREFORE
SHOULD MAKE MEASUREMENTS MUCH MORE BETTER. WHEN I FIRST MENTIONED THIS TO A VERY
SENIOR PERSON, HE SAID , THIS CAN'T BE RIGHT BECAUSE IN THE YEARS OF GRAVITY ,
PEOPLE WOULD HAVE USED THIS CONCEPT . SO NICE AND BEAUTIFUL AND OBVIOUS. IT WAS OBVIOUS
IN HINDSIGHT, OF COURSE, LIKE ANY INVENTION IS. SO TWO WEEKS LATER , THE PERSON CAME BACK AND
SAID , YOU MIGHT HAVE A POINT. WE TRIED THIS THING OUT . FIRST A LITTLE TEST APPARATUS. THEN
IN A DEDICATED EXPERIMENTS . I GOT A PRECISION MEASUREMENT TREND FROM THE NATIONAL INSTITUTE OF
STANDARDS, AND WE BUILT A REALLY SOPHISTICATED INSTRUMENT , AGAIN BUILT ON TURNTABLES .
NESTED TURNTABLES. VERY PRECISELY MACHINE MASSES SO THE MACHINE SHOP IS VERY IMPORTANT
IN MAKING SUCH AN EXPERIMENT POSSIBLE. WE MEASURED THE GRAVITATIONAL CONSTANT. IT
WAS ONE OF THE MORE STRESSFUL MEASUREMENTS BECAUSE HERE, YOU JUST DIDN'T KNOW WHAT THE
ACTUAL VALUE IS THAT WAS EASY TO DEFEND. WHEN YOU MAKE A ZERO MEASUREMENT WHERE YOU
BASICALLY DISCOVER THE EFFECT ISN'T THERE, YOU KNOW, IT'S MORE --IT'S SIMPLER TO DIGEST
THEN WHEN YOU MAKE AN EXPERIMENT FOR YOU HAVE TO NAIL DOWN A VALUE IN THE END TO MANY DIGITS AND
REALLY COMMIT YOUR CAREER BASICALLY ON IT THAT IT IS RIGHT. SO IT WAS VERY STRESSFUL. THE NICE
THING WAS THAT THE APPARATUS REALLY HAD SO MANY THINGS WHERE UNCERTAINTIES THAT PEOPLE HAD
PREVIOUSLY EXPERIENCED IN THE MEASUREMENT REALLY TOTALLY DROPPED OUT. AND SO ARE MEASUREMENTS
HAD A VERY SMALL UNCERTAINTY AND IS TO THIS DATE BASICALLY THE TEXTBOOK VALUE THAT YOU NOWADAYS
THE IN TEXTBOOKS , EXCEPT THE VALUE IS MOSTLY DETERMINED FROM OUR EXPERIMENTS .
THE VALUE THAT THIS DETERMINES TO BE THE VALUE THAT YOU ARE SUPPOSED TO USE
IN YOUR CALCULATIONS . AND OUR VALUE WAS A LITTLE BIT HIGHER THAN THE PREVIOUS ACCEPTED
VALUES. BUT IT TURNS OUT THAT ALL EXPERIMENTS THAT FOLLOWED , FOLLOWED ARE TRENDS AND ALSO THE VALUE
. RECENTLY , A TEAM IN CHINA ACTUALLY REPEATED OUR EXPERIMENTS VERY BEAUTIFULLY . THEY GOT EXACTLY
THE SAME VALUE. ONE INTERESTING FACTOID THAT WHEN YOU KNOW THE GRAVITATIONAL CONSTANT VERY
WELL, YOU OUGHT TO KNOW THE MASS OF THE EARTH VERY WELL. WE ALSO PUT THE MASS OF THE EARTH
IN THEIR. THAT MADE IT ALL OVER THE BOULEVARD. THE EARTH HAD CHANGED MASS APPARENTLY
. IT HADN'T CHANGED MASS.
THANKS A LOT FOR THAT ANSWER. THAT SOUNDS
PRETTY AMAZING. IT LOOKS LIKE THE AUDIENCE WANTS TO QUIZ YOU . THEY ASKED YOU ,
THIS IS A QUESTION FROM JAMES RAYMOND. LET ME ASK THIS QUESTION TO BLAME.
CAN YOU MAKE AN APPROXIMATION USING ISA GRAVITY EQUATION THAT COLLAPSES
INTO NEUTRONS IN [ INDISCERNIBLE ] LAW. >> THE INVERSE IS A NATURAL CONSEQUENCE.
SO THE ANSWER IS YES. FOLLOWING QUESTION. IF YOU PUT A CLOCK IN THE CENTRIFUGE
SO THE EXPERIENCE IS 50,000 G , WILL THE CLOCK SLOW DOWN AS IF IT
WERE SITTING ON A SUPERMASSIVE PLANET?
THAT'S A GOOD QUESTION. THE CLOCK
CAN'T TELL THE DIFFERENCE BETWEEN GRAVITY AND ACCELERATION. THAT
IS AN EQUIVALENCE ISSUE.
BUT THE CLOCK EXPERIENCES
THE DOPPLER SHIFT ALSO.
THAT'S A QUESTION I DO THINK ABOUT. I
WOULD THINK INITIALLY YES . THERE SHOULD BE --THERE SHOULD BE A CLOCK CHANGE. BUT
-- THAT IS AN EXCELLENT QUESTION.
SO NOW I QUESTION FOR ERIC. IS
A PERFECT VACUUM POSSIBLE WHERE NO MATTER , ANTIMATTER, OR STRINGS EXIST?
AS FAR AS WE KNOW, IT'S IMPOSSIBLE TO GET RID OF WHAT'S GOING ON IN THE VACUUM . THIS BACK
IN ENERGY. IT'S IMPOSSIBLE TO GET RID OF IT. IT HAS TO BE THERE. YOU CAN THINK OF KIND OF
AN ANALOGY. AND THAT IS, IF YOU HAVE A HYDROGEN ATOM , IT IS A GROUND STATE. BACKGROUND STATE IS
DETERMINED BASICALLY BY THE PRINCIPLE THAT SAYS IF YOU TRIED TO MAKE THE ENERGY LOWER , OKAY,
YOU WOULD HAVE TO SPEED UP THE MOTION . AND SO THE OPTIMIZED , MINIMUM ENERGY YOU CAN GET IS
WHAT IS THE GROUND STATE OF THE HYDROGEN ATOM. THERE IS ENERGY. IT DOESN'T HAVE ZERO ENERGY. YOU
CAN'T USE IT FOR ANYTHING. YOU CAN'T GET ANY MORE ENERGY OUT OF IT. IT'S NOT USEFUL. YOU ARE NOT
GOING TO GET RICH FROM IT. BUT IT IS THERE. WHY DOESN'T THAT ENERGY THAT MICHAEL AND WE ARE
TALKING ABOUT THE ELECTRODE MAGNETIC FIELD, RIGHT IS AND THAT ENERGY --THERE IS A LOT OF
IT. THE WORST PREDICTION OF PARTICLE PHYSICS. MAINLY IF YOU TAKE THE ENERGY AT ALL LOADS OF
THE ELECTRIC FIELD AND AT THE VACUUM ENERGIES UP FOR THIS WAVELENGTH AND THAT WAVELENGTH COME
ALL THE WAY UP , ALL THAT OUGHT TO GRAVITATE, OKAY? JUST BY FOLLOWING THE RULES OF MECHANICS.
THAT GIVES YOU A NUMBER WHICH IS 120 POWERS OF 10 TOO BIG COMPARED TO WHAT WE OBSERVED. HERE IS
A REAL MYSTERY THAT NOBODY UNDERSTANDS.
MIGHT I JUST ADD, YOU CAN CHANGE THE
VACUUM ENERGY. FOR EXAMPLE, IF YOU PUT TWO CONDUCTING PLATES CLOSE TOGETHER, THAT EXCLUDES
CERTAIN MOLDS THAT OTHERWISE HAVE CONTRIBUTED TO THE VACUUM ENERGY, REDUCING IT. THAT GIVES
RISE TO WHAT'S CALLED THE CASIMIR FORCE. CONDUCTING PLATES.
OKAY.
YOU WON'T GET RICH FROM IT.
THERE IS A YOUTUBE QUESTION FROM SOMEONE WHO WAS A BIT CONCERNED ABOUT THEIR TAX DOLLARS.
WHY IS EVERYTHING IN YOUR LAB GOLD COATED?
THAT'S EASY TO ANSWER.
THAT QUESTION IS FOR BLAYNE.
BECAUSE THE ELECTROMAGNETIC BACKGROUND IS SO MUCH LARGER THAN GRAVITATIONAL FORCES TRYING TO
MEASURE. YOU NEED TO REDUCE THE ELECTROMAGNETIC SYSTEMATIC ERRORS AS MUCH AS YOU CAN. GOLD
COATING MAKES IT EQUAL POTENTIAL SURFACE BETTER , ALMOST I WOULDN'T SAY IT'S THE BEST ,
BUT IT IS THE BEST WE CAN ACTUALLY DO IN OUR LAB TO MAKE A SERVICE EQUAL POTENTIAL AND SHIELD
OUT THE ELECTROSTATIC INTERACTION.
THERE'S ANOTHER QUESTION FOR
JENS. YOUR INSTRUMENTS DON'T LOOK VERY TECHNOLOGICALLY ADVANCED.
WHY DIDN'T SOMEONE DO THIS BEFORE?
THEY ARE ACTUALLY PRETTY TECHNOLOGICALLY
ADVANCED. THEY MIGHT NOT LOOK LIKE IT. IF I WERE TO SHOW YOU A PICTURE OF IT, IT IS
ACTUALLY PRETTY SOPHISTICATED . THE REASON WHY PEOPLE HAVE SHIED AWAY FROM IT IS SIMPLY THAT
THESE EXPERIMENTS ARE EXTREMELY HARD. THEY ARE NOT EASY TO DO. GRAVITY IS SO INCREDIBLY WEEK. IF
YOU WANT TO MEASURE GRAVITY TO HEIGHT PRECISION AND SOME OTHER AFFECT THAT IT HAS STRENGTHS THAT
ARE SIMILAR THAT WOULD VERY MUCH AFFECT YOUR MEASUREMENT . WE GO THROUGH HOOPS TO AVOID
ALL KINDS OF OTHER AFFECT ONTO THESE BALANCES THE REASON WHY PEOPLE HAVEN'T
DONE THIS IS THESE EXPERIMENTS ARE EXTREMELY , EXTREMELY DIFFICULT. THEY TAKE A
LOT OF TIME TO GET RIGHT . THEY ARE NOT EASY.
THANK YOU. THERE'S A QUESTION FOR
ERIC. YOU LISTED SORT OF A SYSTEMATIC ERROR IN THE EXPERIMENTS . IN YOUR SURVEY, WHICH
ONES HAVE THE LARGEST IMPACT ON THE ACCURACY?
WELL, IT DEPENDS ON WHAT EXPERIMENT YOU
ARE TALKING ABOUT. IF YOU ARE TALKING ABOUT THE [ INDISCERNIBLE ] PRINCIPAL, THE MAIN DEPARTURE OF FLATNESS , UNIFORMITY OF THE
GRAVITATIONAL FIELD WAS A VERY IMPORTANT ONE. ANOTHER VERY IMPORTANT ONE IS THE TEMPERATURE
JUST BECAUSE IT IS SO HARD TO UNDERSTAND. IF YOU DELIBERATELY CHANGE THE TEMPERATURE
OF THE INSTRUMENT, LOOK WHAT HAPPENS. IT'S REALLY COMPLICATED. OKAY? WHAT WE CAN DO IS WE CAN
DELIBERATELY APPLY A TEMPERATURE AND SEE HOW BIG AN EFFECT IT HAS. IT HAS A BIG EFFECT, OKAY? THEN
YOU SAY, HOW WILL DO WE KNOW THERE WASN'T SOME OF THAT ? THAT IS LIMITED BY HOW WILL YOU CAN
ACTUALLY MEASURE TINY TEMPERATURE DIFFERENCES. IN FACT, INTERESTINGLY, THAT IS WHAT THE
SATELLITE EXPERIMENTS I TOLD YOU ABOUT. THEIR BIGGEST PROBLEM WAS TEMPERATURES.
THANK YOU. SO NEXT QUESTION , AND THIS
ONE IS FROM BEN TO JENS. DOES THE ROTATION CREATE AN ELECTROMAGNETIC FIELD
DESPITE IT TURNING SLOWLY?
NO . I MEAN , THE AUTOMATIC FIELD IS
ONLY CREATED IF THERE ARE CHARGES THAT ARE BEING MOVED. IN OUR EXPERIMENTS WHEN THERE
ARE TURNTABLES AND SO ON, WE GO THROUGH HOOPS TO AVOID CHARGES. THERE'S NO ELECTROMAGNETIC EFFECT
THAT WE ARE GENERATING WITH OUR INSTRUMENT. THERE IS ONE THING THAT WE ARE WORRIED ABOUT, AND
THAT IS, FOR EXAMPLE, THE MOTOR THAT DRIVES THE TURNTABLE AROUND. IT IS AN ELECTRIC MOTOR. IT HAS
ELECTRIC FIELDS IN THERE. WE WENT THROUGH HOOPS AGAIN TO MAKE THOSE ELECTROMAGNETIC FIELDS SO THAT
THEY DON'T AFFECT THE PENDULUM. THERE ARE SHIELDS. THE ELECTRIC MOTOR IS NOT A REGULAR ELECTRIC MOTOR
WHERE IT GOES CLOCK, CLOCK , CLUNK. IT IS A COPPER DRAG CUP . IT DRAGS THE TURNTABLE AROUND. THE
ROTATION ITSELF BY PHYSICS DOESN'T INDUCE A MAGNETIC FIELD BECAUSE THERE'S NO CHARGES. BUT
THEN ALSO TECHNICAL ELECTRO MAGNETIC FIELDS ARE VERY, VERY CAREFUL WITH HAVING
IT AT VERY DIFFERENT FREQUENCIES TO MINIMIZE AS MUCH AS POSSIBLE.
THAT IS A GOOD QUESTION.
THANKS. ANOTHER QUESTION FROM ALAN FOR
BLAYNE. IS THERE A POINT AT WHICH THE CASIMIR EFFECT BECOMES A LIMITATION ON THE
EXPERIMENTAL SPATIAL RANGE OF THESE PENDULUMS?
I WISH WE COULD GET CLOSE ENOUGH TO ACTUALLY HAVE
A PROOF THAT IT DOES, BUT THE ANSWER IS YES. YOU GET WITHIN THIS SORT OF RANGE, THE CASIMIR , THE
SURFACES ARE TOO CLOSE TO THE SPECIAL FOIL TO TRY TO SHIELD. YOU WOULD DEFINITELY HAVE THE CASIMIR
FORCE CONTRIBUTING , WHETHER YOU COULD DISTINGUISH THAT FROM GRAVITY, THAT WOULD DEPEND ON GEOMETRY
. IF YOU KNEW YOU WERE GOING TO ENCOUNTER IT, YOU MIGHT BE ABLE TO THINK OF WAYS TO DISTINGUISH THAT
FORCE FROM GRAVITY. THAT FORCE WOULD BE ATTRACTIVE BETWEEN THE PLATES. YOU COULD MAKE YOUR GRAVITY
BE A TWISTING FORCE, WHICH IS WHAT WE DO . WITH YES, THE CASIMIR FORCE, THERE IS NO WAY
TO SHIELD IT AT THOSE DISTANCES.
HERE IS ANOTHER QUESTION FROM MICHAEL. TO
ERIC. IN CLASSIC ELECTROMAGNETISM , THE ELECTRICAL FIELD EMERGES FROM
THE INVERSE [ INDISCERNIBLE ]. IS THERE A GRAVITATIONAL ANALOG OF THE MAGNETIC
FIELD AT [ INDISCERNIBLE ] VELOCITIES?
THE ANSWER IS YES. IT IS CALLED GRAFFITO
MAGNETISM. A VERY CLOSE ANALOGY . IT HAS TO DO WITH INCIDENT ELECTRICAL CURRENTS, YOU
HAVE MASS CURRENTS. IT IS INDEED , AS YOU SAID, YOU CAN GET THE MAGNETIC FIELD JUST FROM THE
TRANSFORMATION OF THE COOL ON-FIELD FOR THE SAME REASONS YOU GET GRAFFITO MAGNETISM .
THANK YOU. A QUESTION TO JENS. THIS QUESTION IS BASICALLY TO LEARN
HOW TO BECOME EXPERIMENTALISTS. HOW DO YOU LEARN TO BUILD IT AS SENSITIVE
AS YOU NEED? THAT ALMOST SEEMS HARDER THAN THE EXPERIMENT ITSELF, AND IT IS
ALSO OUTSIDE OF OUR SCHOOLING.
GOOD QUESTION. I THINK I WAS ALWAYS
INTERESTED IN MECHANICAL THINGS. AS A KID, I REPAIRED TVs . I ACTUALLY WORKED IN A TV REPAIR
SHOP , AND I REPAIRED CARS. I LOVE MECHANICAL THINGS. BUT THEN THE SKILLS FOR THESE EXPERIMENTS
, WE SORT OF STARTED TEACHING THEM OURSELVES. THERE WAS NOT AN INSTANT PROCESS BY WHICH WE
LEARNED EVERYTHING. I MEAN, WE HAD TO LEARN THAT INCREDIBLE MACHINING TOLERANCES WERE REALLY
IMPORTANT FOR THESE EXPERIMENTS. AND, YEAH . SO IT'S A SLOW THING . YOU JUST HAVE TO
STICK WITH IT AND STAY WITH IT. REMAIN FOCUSED ON THIS GOAL AND FIGURE ONE THING AFTER THE
OTHER OUT TO BECOME AN EXPERIMENTALIST.
ELECTRONICS. PHYSICS 334 , NEXT QUARTER.
JUST DOING IT INSTEAD OF SITTING AROUND AND WORRYING . TRY IT OUT , AND YOU WILL
LEARN SOMETHING. THAT'S A VERY IMPORTANT PART OF THE SKILLS OF AN EXPERIMENTALIST.
INCIDENTS SITTING AROUND AND BEING A PURIST, GO TO THE LAB. >> NATURE IS VERY KIND
BECAUSE OF YOU ASK THE RIGHT QUESTION, NATURE , RIGHT ON. IN OF THE PHYSICS IS WHAT
YOU ARE TESTING IS ACTUALLY CORRECT.
THANK YOU. QUESTION FOR ERIC. IS THERE ANY POINT
IN MAKING THESE MEASUREMENTS OF ELECTRONIC CHARGE TO MEASURE DEVIATIONS OF [ INDISCERNIBLE ].
THERE USED TO BE POINT, CLEARLY. BUT NOW, WE CAN TEST THE QUANTUM MECHANICAL VERSION OF
COULOMB'S LAW. IT TURNS INTO A VIRTUAL PROTON. THAT RELIES ON THE THEORY THAT YOU WOULD USE FOR
COULOMB'S LAW . YOU CAN GET VERY TINY DISTANCES THAT WAY. YOU CAN NEVER GET THERE DIRECTLY.
IT HAS BEEN TESTED BECAUSE THE THEORY WORKS. IN OTHER WORDS, IF YOU MEASURE THE PROBABILITY
THAT THE ELECTRON AND POSITRON TURN INTO A [ INDISCERNIBLE ] THAT ENERGY CORRESPONDS
TO AN EXTREMELY TINY DIFFERENCE. MY TASTE IS IT'S UNLIKELY YOU'RE GOING TO LEARN
ANYTHING FROM ACTUALLY TRYING TO MEASURE IT WITH [ INDISCERNIBLE ] OBJECTS BECAUSE IT WORKS
SO WELL IN THESE ACCELERATOR EXPERIMENTS.
WE HAVE ANOTHER QUESTION FROM BRIAN TO BLAYNE.
WHAT DID THESE RESULTS -- WOULD THESE RESULTS [ INDISCERNIBLE ] DARK MATTER .
COULD YOU REPEAT IT? MIC'D WITH THESE RESULTS PUT ANY BOUNDS ON DARK
MATTER AND DARK ENERGY FORCES?
IT CERTAINLY PUTS LIMITS ON DARK MATTER. WE
COMPARED THE ACCELERATION OF DIFFERENT OBJECTS TOWARDS THE CENTER OF THE GALAXY
BETWEEN US AND THE CENTER OF THE GALAXY, OUR ACCELERATION WAS 30% LARGER THAN
NORMAL MATTER. 30% OF THE ACCELERATION TOWARDS THE CENTER OF THE GALAXY IS DUE TO DARK
MATTER. BY COMPARING THE RATE AT WHICH DIFFERENT OBJECTS FALL TOWARD THE CENTER OF THE GALAXY, WE
ARE SEEING, IS THERE A DARK COMPONENT TO GRAVITY? DOES DARK MATTER --DIFFERENTLY TO DIFFERENT
MATERIALS? 10 TO THE FIFTH IS OUR SENSITIVITY. WE SHOWED THAT DARK MATTER GRAVITATES JUST LIKE
ORDINARY MATTER. THERE IS NO ADDITIONAL DARK FORCE IN ADDITION TO THE GRAVITATIONAL INTERACTION
OF DARK MATTER. DARK ENERGY? I DON'T THINK WE ACTUALLY SAY ANYTHING DEFINITE .
IT'S VERY HARD TO THINK OF A LABORATORY EXPERIMENT THAT CAN TELL YOU ANYTHING ABOUT DARK ENERGY . I
HAVE THOUGHT ABOUT IT A LOT. CHRISTOPHER STUBBS THOUGHT ABOUT IT A LOT. IT WOULD BE GREAT IF YOU
COULD DO IT, BUT NO ONE HAS COME UP WITH A WAY OF TESTING IT. IT'S TOO BAD. IF YOU
CAN THINK OF A WAY , TRY IT.
SO A QUESTION FROM HORIZON TO ERIC. CAN YOU
SPEAK ABOUT MATTER- ANTIMATTER EQUIVALENTS PRINCIPAL?
YES. IF MATTER AND ANTIMATTER FALL DIFFERENTLY , OKAY?
THAT WOULD MEAN THERE IS SOMETHING THAT COUPLES TO BARYONS FOR EXAMPLE. WE WOULD SEE THAT
IN OUR EXPERIMENTS BECAUSE LET'S CONSIDER A HYDROGEN ATOM FALLING AND AN ANTI-HYDROGEN ATOM
FALLING. THE DIFFERENCE IN THE CHARGE OF THOSE IS A FACTOR OF TWO , LET'S SAY. THE MATERIALS WE USE
IN OUR PENDULUMS, THE DIFFERENCE IN THE SAME THING IS A VIEW PARTS IN 10 TO THE 3rd . WE CAN
COMPARE , FOR INSTANCE, WHEN WE COMPARE BERYLLIUM AND ALUMINUM , WE THINK OF BOTH WILLIAM AND
ALUMINUM CAN BE MADE UP OF A CERTAIN NUMBER OF HYDROGEN ATOMS PLUS A CERTAIN NUMBER OF NEUTRONS.
THEY ARE BOUND TOGETHER WITH FINDING ENERGY. WE CAN THINK ABOUT WHAT WE'RE DOING, WE
ARE CHECKING , DING THE NEUTRONS FALL THE SAME AS HYDROGEN, FOR EXAMPLE? WE COULD ALSO
--SO WE CAN SAY THAT IT'S EXTREMELY UNLIKELY THAT ANTIMATTER FALLS UP. THAT IS
GENERALLY THE THING THAT PEOPLE TALK ABOUT. SUPPOSE ANTIMATTER FELL UP. I CAN TELL YOU THAT IS
RIDICULOUS. THINK OF THE PHOTON . OKAY? THE PHOTON IS EQUAL AMOUNTS OF MATTER AND ANTIMATTER . IT HAS
NO MATTER IN IT. IF ANTIMATTER FELL UP, THE PHOTON SHOULD NOT FALL. I SHOWED YOU THAT EXPERIMENT WITH
THE SCENE AND SATURN. THE PHOTONS WERE FALLING. EVEN MORE OBVIOUS , WE KNOW IN OUR MODERN STANDARD
MODEL THAT THE MASS OF A PROTON AND NEUTRON IS , YOU KNOW, 99% IN THE BLUE ONE FEELS . NOT
IN QUARKS MASSES . THOSE FIELDS ARE EQUAL AMOUNTS OF MATTER AND ANTIMATTER. THE NEUTRON OUGHT
TO FALL MORE SLOWLY THAN AN ELECTRON. OKAY? THESE ARE JUST NOT CREDIBLE IDEAS. YOU CANNOT
BE INTELLECTUAL CONSISTENT INSIGHT INTO MATTER OUGHT TO FOLLOW UP AND SAY THAT THE STANDARD
METAL WORKS. THE STANDARD MATTER WORKS.
OKAY. WE HAVE A QUESTION ALSO ABOUT
SPECULATIONS TO JENS. AS THE FUTURE GENERATION OF THESE EXPERIMENTS GET MORE FIVE,
YOU MIGHT POTENTIALLY FIND DEVIATIONS . ONE OF THE MOST LIKELY SOURCES OF POSSIBLE DEVIATIONS?
AND WHICH ONES YOU WOULD PERSONALLY FIND MOST INTRIGUING AND INTERESTING .
AGAIN, A REALLY GOOD QUESTION. CERTAINLY IF THERE ARE NEW FIELDS THAT DIRECTLY
--OR CAN BE MOLDED INTO A SCENARIO THAT CONNECTS GRAVITY WITH A STANDARD MODEL , THOSE
WOULD CERTAINLY BE THE MOST INTERESTING ONES. THERE ARE CERTAIN CANDIDATES . STRING
THEORY HAS CERTAIN PARTICLES THAT ARE THERE THAT WOULD MEDIATE AN EQUIVALENT BY
LETTING ACTION. FINDING THOSE WOULD BE REALLY INTERESTING. REALLY INTERESTING
CANDIDATES TO LOOK FOR.
OKAY. SOUNDS INTERESTING. QUESTION FROM REED
THOMPSON TO BLAYNE. CAN YOU CALCULATE THE TOLERANCES FOR THE MACHINING -- COULD YOU QUANTIFY
THE TOLERANCES NEEDED FOR MACHINING PARTS FOR THE EXPERIMENT? WAS IT PAST THE POINT WHERE MACHINING
SUCH SMALL TOLERANCES COST MORE THAN THE GOLD COATING? THE ELECTRICAL COATING?
A PRACTICAL MINDED PERSON.
IT DEPENDS ON THE COMPONENT, WHAT TOLERANCE YOU
NEED. THE HIGHEST TOLERANCE IS REQUIRED ON THE PENDULUM ITSELF. YOU CAN'T SPECIFY ONE 10th
OF A MILL . THAT IS TYPICAL OF ANY MACHINE. WE CERTAINLY TELLER MACHINES TO DO AS WELL AS WE
CAN . AND THEN SYMMETRY , LITTLE TWEAKING SCREWS ALLOW US TO COMPENSATE FOR ANY IMPERFECTIONS THAT
MAY HAVE ARISEN FROM IMPERFECT MACHINING.
THAT MAKES SENSE. STAN CURTIS ASKS
ERIC. ANY OF YOUR CONCERNS ABOUT WHEN THEY STARTED BUILDING THE LIGHT RAIL . WERE
YOU CONCERNED ABOUT YOUR EXPERIMENTS?
YES. THE LIGHT RAIL COMES
PRETTY CLOSE TO THE CAMPUS. I MENTIONED THAT WE ARE VERY, VERY
SENSITIVE TO VIBRATIONS . YES, INDEED. IN FACT, WE MAY HAVE TO
Guest: IF WE WANT SUBSTANTIAL IMPROVEMENTS, IT IS POSSIBLE WE MIGHT HAVE TO GO
SOMEPLACE ELSE THAT IS QUARTER.
BUT DID IT IMPACT THE EXPERIMENTS?
YES. WHAT IT DOES , IN PARTICULAR , IT'S THESE
INVERSE SHORT DISTANCES. THEY SHAKE THINGS AROUND. YOU HAVE THINGS VERY CLOSE AND SOMETHING SHAKES
, SOMETIMES THEY TOUCH. SO IT HAS --IT'S REALLY A REAL LIMITATION ON THE TEST OF THE INVERSE . IF
WE DIDN'T HAVE THEM, WE CAN DO A LOT BETTER.
SO YOU MIGHT END UP MOVING TO THE CASCADES?
>> WE HAVE A QUESTION FROM THE COMMUNITY CLUB. THEY ASK BLAYNE ABOUT THE CLOCK AGAIN. THE CLOCK
IN THE CENTRIFUGE, IS A SUBATOMIC PARTICLE [ INDISCERNIBLE ] -- IS A SUBATOMIC PARTICLE AND A [
INDISCERNIBLE ] BASICALLY A CLOCK IN A CENTRIFUGE? PHYSICS QUESTION.
I CAN TELL YOU IT IS. FOR INSTANCE, WE KNOW
NEW ONES ARE CIRCLING AROUND . THEIR LIFETIME IS LENGTHENED BY THE FACT THEY ARE
IN THE STOCK CENTRIFUGAL FORCE. MANY EXAMPLES. ARTICLES CAN LIVE 1000 TIMES
LONGER IF THEY ARE IN AN ACCELERATOR.
WE HAVE A QUESTION FROM NOAH. IS THERE A THEORETICAL RATIONALE FOR
USING 18 AND 120 FOLD SYMMETRY ? IS THERE A PRACTICAL LIMITATION? PLEASE GIVE MY
LOVE TO THE FOLKS IN THE MANAFORT GROUP.
INTERESTING. CAN YOU REPEAT THE QUESTION?
IS THERE A THEORETICAL RATIONALE FOR USING 18 AND
124 SYMMETRIES ON THE ROTATING ATTRACTORS?
IT'S NOT A DIRECT RATIONALE OTHER THAN YOU
WANT TO PRODUCE A SIGNAL THAT IS AT A VERY DIFFERENT FREQUENCY. SO THE 120 TIMES REVOLUTION
SIGNAL IS AT A MUCH HIGHER FREQUENCY THAN THE 18 PER REVOLUTION SIGNAL. AND SO YOU CAN TELL THESE
THINGS APART WHERE THEY OCCUR IN FREQUENCY VERY PRECISELY . YOU CONFORM THESE RATIOS. BUT
OTHERWISE, YOU KNOW , IDEALLY , YOU WANT TO GO TO EVEN LARGER NUMBERS BECAUSE THAT
ALLOWS YOU TO TEST EVEN SHORTER RANGES. BUT THE ONLY THEORETICAL REASON TO GO TO
120, FOR EXAMPLE, IS THAT YOU WANT TO HAVE A LOT OF SMALL SECTORS THAT
INTERACT GRAVITATIONALLY.
IN A HARMONIC OF ONE , IT WILL AFFECT THE OTHER.
WE PICK THINGS THAT ARE NOT DIVISIBLE .
OUR FIRST TEST , THE INVERSE , WE HAD 10 I THINK.
A REPORTER ASKED ME, DOES THAT HAVE ANYTHING TO DO WITH THE 10 IN STRING THEORY. I SAID NO. IT IS
REALLY 2 5. 5 IS SOMETHING THAT YOU DON'T FIND IN THINGS BESIDES WHEELS. YOU DON'T HAVE 2 BECAUSE
WE WOULD PUT TWO LITTLE SPHERES IN OPPOSITE HOLES. THE NEXT EXAMPLE, WE HAD 21 IN TWO RANKS. 42.
42 YOU KNOW IS THE ANSWER TO THE QUESTION, WHAT'S THE MEANING OF LIFE. THAT HAVE NOTHING TO
DO WITH IT. 21 WAS 3 7. OKAY. THEN WE HAVE 120 IN THE LAST VERSION. THAT'S 11 POWERS OF 10 BY WHICH
THE VACUUM ENERGY DOESN'T GRAVITATE. THESE ARE ALL ACCIDENTS. THEY ARE DECIDED BY CONSIDERATIONS
THAT JENS AND BLAYNE WERE TALKING ABOUT.
THIS IS THE LAST QUESTION . A VISIONARY QUESTION. EACH OF YOU COULD ANSWER THIS ONE BY ONE.
WHAT'S NEXT FOR THE GROUP ? JENS MAYBE?
ONE THING WE HAVE ALREADY DONE AT OUR
GROUP IS , WE UNDERSTAND VERY SMALL EFFECTS INCREDIBLY WELL. [ INDISCERNIBLE ] IS
AFFECTED BY A LOT OF THESE TINY, TINY EFFECTS. WE HAVE DONE LOT OF CONTRIBUTIONS WHERE WE GO
ABOUT AND UNDERSTAND VERY SUBTLE EFFECTS FOR THEM TO IMPROVE GRAVITATIONAL WAVE DETECTION. ANOTHER
DIRECTION IS , WE HAVE AN EXPERIMENT IN WHICH --IT'S A COMPLICATED SCENARIO TO EXPLAIN
--WHERE A TORQUE AND BALANCE CAN'T POSSIBLY DETECT DARK MATTER DIRECTLY . A
CERTAIN TYPE OF SCENARIO OF DARK MATTER, BUT THAT'S ONE OF THE EXPERIMENTS WE
ARE HEAVY ON AT THE MOMENT ALSO.
ERIC? ANYTHING TO ADD? >> WHAT JENS SAID.
OTHER FRONTIERS IN PHYSICS LECTURES. WE WOULD LIKE TO THANK OUR GUESTS . PROFESSOR
ERIC ADELBERGER, BLAYNE HECKEL, AND JENS GUNDLACH. LAST BUT NOT LEAST, WE
THANK THE COLLEGE OF ITS ARTS AND SCIENCES AT THE UNIVERSITY OF WASHINGTON AND THE VIDEO CREW
WHO FACILITATED THIS LECTURE AND HELPED US ALONG THE WAY. HAVE A NICE EVENING , AND HOPE TO SEE
YOU ALL IN THE NEXT FRONTIERS IN PHYSICS LECTURE IN ME THE 2022. THANK YOU.
[ APPLAUSE ]
