NRICH NAVIGATION SEARCH CONTACT SKIP OVER TERMS AND CONDITIONS STUDENTS GUIDE FEATURES TEACHERS EARLY YEARS EARLY YEARS FOUNDATION STAGE KINDERGARTEN PRIMARY KEY STAGE 1 GRADES KEY STAGE 3 GRADE 1 KEY STAGE 2 GRADE STAGES UPPER KEY STAGE 4 GRADE 11 TOPICS STEM ENGINEERING MATHEMATICS EVENTS TRANSLATE BRIEF HISTORY OF TIME ARTICLE LEO EVER REGULAR THE SUN WONDERED THE PASSAGE PREHISTORIC PEOPLE PHASES OF THE MOON YEARS AGO RECORDING HUMANITY THE PROGRESS NATURAL THE COURSE THE YEAR CHANGES SEASONAL WINDS FLOODING THE FLOWERING TREES BREEDING MIGRATION OF ANIMALS DIVISIONS OBSERVATION LOCAL CUSTOMS RECOGNITION OF MEASURING THE MOON AND THE STARS MOVES ACROSS THE SKY SHADOWS CHANGE DIRECTION SIMPLE SUNDIAL MEASURE LENGTH OF A DAY QUICKLY LENGTH THE DAY DIFFERENT TIMES REASONS DIFFERENCE DISCOVERED ASTRONOMERS ACCEPTED FACT THE EARTH TRAVELS ROUND ELLIPTIC ORBIT AXIS VARIATION CIRCULAR ORBIT LEADS THE EQUATION WORK OUT THE DIFFERENCE DISCOVERY SUNDIALS HAD TO LATITUDES ALTITUDE IN THE SKY HIGHER LONGER ARTISTS FIND MODERN ROMAN NUMERALS LOOK ARE YOU FACES DISCOVER WALL PREHISTORIC CARVING SAID TO THE ORION CONSTELLATION IMAGE OF STAR CONSTELLATION OF ORION PIECE MAMMOTH TUSK CONSTELLATION ORION STANDING RIGHT ARM RAISED SWORD BELT SEEN THE WORLD ORION GOD EGYPTIANS PARTS DOGS CHASING BORANA PEOPLE EAST AFRICA SOPHISTICATED CALENDAR OBSERVATIONS OF STAR STARS SOUTHERN WINTER NORTHERN HEMISPHERE SOUTHERN HEMISPHERE THREE STARS THE RED STAR EGYPTIAN STAR MAP SHOWS CONJUNCTION THE PLANETS SATURN IN THE CONSTELLATION OF SOLAR ECLIPSE HEAVENLY DATE REASON ADOPTING ARITHMETIC SYSTEM PROBABLY DECISION DAYS CIRCLE EXISTING CONVENIENCE THE SKY FIXED STARS SYMBOL STRENGTH MYTHOLOGY NEARLY BABYLON INDIA NORTHERN THE ASSYRIAN WINGED BULL SWIFTNESS BIRD HUMAN INTELLIGENCE BABYLONIANS DEVELOP MATHEMATICAL THEORY OF DIVIDED ZODIAC APPEARS 500 BCE YEAR OF MONTHS 30 DAYS FRACTION TODAY MINUTES EASIER FRACTIONS EGYPT CALCULATION TOOL THE 16TH DECIMAL NOTATION TAKE OVER ARCHAEOLOGICAL EVIDENCE OF CHINESE CALENDARS SHOW MONTH TRADITIONAL CHINESE ORIGIN MOVEMENTS THE SUN AND THE MOON PERIOD CHINESE ASTRONOMERS AWARE ACCURATE SECOND CENTURY CE THE CALENDAR PROBLEM PRECESSION THE FOURTH FIFTH CENTURIES FIFTH CENTURY CE THE SCHOLAR COMPREHENSIVE DAYAN COMPILED TANG DYNASTY DEVELOPMENT GRADUAL WITH RESPECT TO THE FIXED STARS SLOW MEANS POSITIONS THE STARS COMPLETE CYCLE CIRCUIT ONCE HIPPARCHUS CALCULATIONS 160 BCE TAKEN THE MIDDLE EAST ALTERED IN 32 THE SPRING EQUINOX EMPEROR CONSTANTINE DATES CHRISTIAN HOLIDAYS EASTER VERNAL EQUINOX THE EQUINOX TEN DAYS POPE GREGORY NEW CALENDAR EXTRA LEAP STILL SMALL ONE DAY SHALL HAVE TO THE EARLY DIVIDE THE NIGHT PERIODS ORDER WORK LENGTHS PLACE TO PLACE FROM ONE CULTURE OIL LAMPS THE CHINESE OIL HEATING LIGHTING RELIGIOUS THE JOURNEY FROM DARKNESS IGNORANCE LIGHT SHAPE LAMP EVOLVED POTTERY STYLE POSSIBLE LEVEL OIL RESERVOIR THE PASSING CANDLE CLOCKS MARKED CANDLES TIME IN CHINA THE SIXTH POPULAR STORY KING ALFRED THE GREAT INVENTED CANDLE CLOCK ENGLAND THE TENTH RATE BURNING SUBJECT TO THE VARIABLE QUALITY USED TO MARK EVENT RATHER TELL TIME OF DAY WATER CLOCKS WATER CLOCK DEVICE STEADY FLOW WATER MEASUREMENTS CONTAINER RECEPTACLE COMPARISON CANDLE OIL LAMP WATER FLOW PRESSURE THE HEAD ASTROLOGICAL CLOCK MAKING DEVELOPED CHINA THE ASTRONOMER SU SUNG ASSOCIATES BUCKET DISPLAYS BRONZE ROTATING CELESTIAL GLOBE MANIKINS RANG SPECIAL TIMES IMPROVEMENTS THE FLOW MAINTAINING CONSTANT HOUR GLASSES TECHNOLOGY TIME LIKE LAMPS CLOCKS CALIBRATE DETERMINE DURATION UNIVERSITY THE DIVISION EVIDENCE EQUAL THE SUNDIAL AT NIGHT TIME WAS PRIESTS DETERMINING EXACT THE DAILY RITUALS RELIGIOUS FESTIVALS MERKHET 600 BCE USES STRING PLUMB LINE TRUE VERTICAL LINE THE OTHER OBJECT PALM STRIPPED SPLIT THIN SLIT PAIR MERKHETS LINING BEHIND POLE STAR VIEWING PLUMB LINES THE SIGHT SURE STRAIGHT LINE MEASUREMENT CERTAIN CROSSED VERTICAL DRAWN WOODEN UPRIGHT NOTCH SIGHT THEORIES HOURS MIGHT BE FACTOR CIVILISATIONS ON THE OTHER HAND FINGERS COUNTING JOINTS CLASSICAL GREEK ROMAN TIMES TWELVE SUNRISE SUMMER DAYS WINTER NIGHTS WINTER DAYS SUMMER THE HOURS 50 BCE THE TOWER THIS WAS THE EIGHT PRINCIPAL WIND KEEPING TIME ATHENS NORTH DEITIES THIS PICTURE FIXED THE GREEKS THEORETICAL 24 HOURS DAYLIGHT OF DARKNESS EQUINOXES ORDINARY PEOPLE SEASONALLY THE ADVENT MECHANICAL EUROPE THE SYSTEM MECHANICAL CLOCK CLOCK ESCAPEMENT MECHANISM IN 12 DRAWING ESCAPEMENT JACOPO DONDI IN 13 APPEAR THE TOWERS RECORD PUBLIC PERIOD OF OSCILLATION MECHANISM DRIVING FORCE WEIGHTS FRICTION MEDIAEVAL TIMES IN PUBLIC ASTRONOMICAL CLOCK THE WEIGHT THE DRUM TOOTHED WHEEL PRAGUE ASTRONOMICAL CLOCK SHOWING THE ZODIAC CIRCLES SURVIVING SPRING DRIVEN THE SCIENCE MUSEUM LONDON HEAVY DRIVE SMALLER PORTABLE CLOCKS AND WATCHES CHRISTIAAN HUYGENS PENDULUM CLOCK REGULATED GALILEO PENDULUM MOTION DESIGN ERROR LESS THAN MINUTE REDUCED ERRORS 10 SECONDS AT SEA JOHN HARRISON CARPENTER INSTRUMENT REFINED TECHNIQUES TEMPERATURE COMPENSATION MARINE CHRONOMETER BALANCE WHEEL KEPT