Time and the Earth’s Rotation
Ticking away the moments that make up a dull day
• Time is a function of math, therefore it’s man made
• Animals do not understand the concept of time, sorry
– Their day is controlled by circadian rhythms
(internal instinctive clock)
– Circadian rhythms is based on the Sun’s position
across the sky
– High noon refers to the Sun’s highest position across
the sky
Before time, people all over the world slept,
worked, played and experienced their lives
based on patterns from sequences of events
• Modern Calendar
– 1n 1580, Pope Gregory XIII, created the Gregorian
Calendar
– It became the official, World calendar
– It was based on the 12 lunar months of 29.5 days and
365.25 days a year. His calendar accuracy repeats itself
every 400 years, including the addition of leap year.
– BC = Before Christ (The conception of Jesus of Nazareth)
– AD = Anno Domini (In the year of our lord)
Early attempts at measuring time
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T-Square = Egypt
Sundial = Rome
Water Clocks = Egypt & Greece
Hourglass (Sand) = Ancient Sailors
Incense & Candles = Early Churches
Mechanical Clock = Europe in Middle Ages
Before Standard Time
• Cities, towns, countries, ... all used different
times
• The Modern Era and the Industrial Revolution
and the invention of James Watt’s steam
engine, resulted in the formation in the
Universal Standard Peace Time
James Watt Steam Engine
Universal Standard Time
• The universal time was established in 1883
• Hours were equally spread from noon to
midnight
• This resulted in 24 equal earth time zones
(7 in the U.S.)
• Earth rotates from west to east in 24 hours
• It takes the Earth 365.25 days to orbit the Sun
• 360 degrees = a circle
• 24 hours = 1 day
• 24 imaginary lines of longitude pass from the
north to south poles make up each hour of the
Earth day, one every 15 degrees of rotation
24 Longitude Lines
• Prime Meridian or 0 degrees longitude marks
the location of the Royal Greenwich
Observatory, Greenwich, England where the
exact universal peace time is kept for the
Earth
• 180 degrees longitude is known as the
International Date Line or where one day
turns into the next. They are exactly 12 hours
apart
FYI
• Time keeps changing all over the Earth
• ½ of the Earth is always light
• ½ of the Earth is always dark
• The Sun only appears to rise in the east and
set in the west