,A ZEPTOSECOND "<SYMBOL ZS"> IS ONE
SEXTILLIONTH OF A SECOND  #AJ_< SECONDS1
A ONE FOLLOWED BY TWENTY-ONE ZEROES
WORTH OF TIME4 ,IT IS THE SHORTEST UNIT
OF TIME THAT PHYSICISTS HAVE EVER
ACTUALLY MEASURED SOMETHING IN3 IN
#BJBJ1 A TEAM IN ,FRANKFURT TIMED A
PHOTON CROSSING A HYDROGEN MOLECULE AT
#BDG ZEPTOSECONDS1 SETTING THE RECORD
FOR THE FASTEST PROCESS EVER OBSERVED4
,BELOW THE ZEPTOSECOND LIES ONLY ONE
SHORTER NAMED ,,SI INTERVAL  THE
YOCTOSECOND "<#AJ_<;T ;S">  AND BEYOND
BOTH1 THE ,PLANCK TIME "<@9#E4D  #AJ_<TT
;S">1 WHERE PHYSICS ITSELF MAY STOP
MAKING SENSE4
,THE LADDER OF SMALL TIME
,TIME GETS SMALL FAST4 ,EACH NAMED STEP
IS A THOUSAND TIMES SHORTER THAN THE
LAST3
NANOSECOND  #AJ_<;Y  ;S  LIGHT TRAVELS
@9#CJ CM "<ONE FOOT">  PICOSECOND  #AJ_<
;S  CHEMICAL BOND VIBRATIONS 
FEMTOSECOND #AJ_<;U ;S  FASTEST CHEMICAL
REACTIONS "<,NOBEL #AIII">  ATTOSECOND 
#AJ_<;X ;S  ELECTRON MOTION "<,NOBEL
#BJBC">  ZEPTOSECOND #AJ_< ;S  PHOTON
CROSSING A MOLECULE2 NUCLEAR PHOTONS 
YOCTOSECOND #AJ_<;T ;S  QUARK-GLUON
PLASMA FLASHES2 HYPOTHETICAL PHYSICS 
,PLANCK TIME #AJ_<TT ;S  BELOW THIS1
8TIME0 MAY NOT EXIST
,TO FEEL THE SCALE3 A ZEPTOSECOND IS TO
ONE SECOND AS ONE SECOND IS TO ABOUT
#CA4G TRILLION YEARS  ROUGHLY #B1CJJ
TIMES THE CURRENT AGE OF THE UNIVERSE4
,LIGHT1 THE FASTEST THING THERE IS1
TRAVELS BARELY A THIRD OF A NANOMETRE 
ABOUT THE WIDTH OF A SMALL VIRUS  IN ONE
ZEPTOSECOND4
,HOW DO YOU EVEN TIME #BDG ZEPTOSECONDS8
,NO CLOCK TICKS THAT FAST  THE
MEASUREMENT IS MADE WITH INTERFERENCE1
NOT A STOPWATCH4 ,IN THE #BJBJ
EXPERIMENT1 ,REINHARD ;,DRNER'S GROUP AT
,GOETHE ,UNIVERSITY ,FRANKFURT FIRED AN
;,X-RAY PHOTON AT A HYDROGEN MOLECULE
AND MEASURED WHICH OF THE TWO ATOMS THE
PHOTON HIT FIRST BY WATCHING THE
INTERFERENCE PATTERN OF THE EJECTED
ELECTRONS4 ,THE DIFFERENCE BETWEEN THE
TWO ARRIVAL READINGS  HOW LONG THE
PHOTON TOOK TO CROSS THE MOLECULE  CAME
OUT TO #BDG ZEPTOSECONDS ON AVERAGE4 ,IT
REMAINS THE SHORTEST TIME INTERVAL EVER
MEASURED4
,THE TECHNIQUE DESCENDS FROM ATTOSECOND
SCIENCE1 THE FIELD THAT WON THE #BJBC
,NOBEL ,PRIZE IN ,PHYSICS  ,ANNE
,L',HUILLIER1 ,PIERRE ,AGOSTINI AND
,FERENC ,KRAUSZ SHOWED HOW TO GENERATE
AND USE LIGHT PULSES LASTING ATTOSECONDS
"<#AJ_<;X ;S"> TO PHOTOGRAPH ELECTRONS
IN MOTION4 ,ZEPTOSECOND MEASUREMENTS
PUSH THE SAME IDEA THREE ORDERS OF
MAGNITUDE FURTHER4
,WHERE ZEPTOSECONDS LIVE IN NATURE
"9 ,LIGHT CROSSING A SMALL MOLECULE 
@9#AJJ#EJJ ZS "9 ,FLUORESCENCE OF A
PHOTON INSIDE A NUCLEUS  NUCLEAR GAMMA
EMISSION TIMES CAN REACH THE
ATTOSECOND-TO-ZEPTOSECOND RANGE "9
,QUARK-GLUON PLASMA  THE 8SOUP0 OF FREE
QUARKS PRODUCED IN HEAVY-ION COLLISIONS
LIVES AND DIES ON TIMESCALES OF
@9#AJ_<#AJ_<;T ;S  DEEP YOCTOSECOND
TERRITORY  ,THE ZEPTOVERSE  THE NEWLY
OPENED REALM OF PHYSICS AT #AJ_<
METRES"93 A PHOTON CROSSES A ZEPTOMETRE
IN ABOUT THREE BILLIONTHS OF A
ZEPTOSECOND1 AND THE RARE DECAYS THAT
PROBE THAT REALM UNFOLD OVER
FEMTOSECOND-TO-PICOSECOND
BEAUTY-PARTICLE LIFETIMES
,UNITS SMALLER THAN THIS
,ONLY THE YOCTOSECOND "<#AJ_<;T ;S"> IS
SMALLER AMONG NAMED ,,SI UNITS  INVOKED
FOR THE FLEETING LIFETIME OF QUARK-GLUON
PLASMA STATES4 ,BELOW NAMED UNITS
ENTIRELY SITS THE ,PLANCK TIME1 @9#E4D 
#AJ_<TT ;S  THE TIME LIGHT TAKES TO
CROSS ONE ,PLANCK LENGTH  WHICH MANY
PHYSICISTS SUSPECT IS NOT A SMALL
QUANTITY SO MUCH AS A BOUNDARY3 THE
POINT WHERE 8BEFORE0 AND 8AFTER0 MAY
STOP BEING MEANINGFUL CONCEPTS4 ,NOTHING
SHORTER THAN A ,PLANCK TIME IS
MEASURABLE EVEN IN PRINCIPLE UNDER
CURRENT PHYSICS4
,SEE ALSO
"9 ZEPTOVERSE  THE REALM AT #AJ_< METRES
"9 SMALLEST THINGS EVER MEASURED  THE
FULL GALLERY OF TINY RECORDS "9
SCIENTIFIC NOTATION "9 HISTORY OF
PHYSICS
,REFERENCES
- ,GRUNDMANN1 ,SENFTLEBEN ET AL4 
8,ZEPTOSECOND BIRTH TIME DELAY IN
MOLECULAR PHOTOIONIZATION10 ,SCIENCE
#CGJ3#CCI "<#AF ,OCTOBER #BJBJ"> -
,NOBEL ,PRIZE IN ,PHYSICS #BJBC 
ATTOSECOND LIGHT PULSES "<,L',HUILLIER1
,AGOSTINI1 ,KRAUSZ"> - ,,BIPM  ,,SI
,BROCHURE1 DECIMAL PREFIXES "<ZEPTO- AND
YOCTO- ADOPTED #AIIA"> - ,,ALICE
COLLABORATION  QUARK-GLUON PLASMA
LIFETIME MEASUREMENTS1 ,,CERN