Ancient people also saw that the Moon seems to
change shape in a cycle that lasts 29 days. They
called this time a month.
HOW DID PEOPLE LEARN TO TELL TIME?
Ancient Babylonians in the Middle East may have
been the first people to divide a day into 24 hours.
They invented the sundial around 2000 bc to tell
the passing of the hours during daylight. A sundial
is a disk with a triangle-shaped piece sticking up
in the middle. The triangle casts a shadow that
moves around the sundial’s disk as the Sun moves
across the sky. The Babylonians put markings on
the disk to show where the shadow would be each
hour.
People also used hourglasses to tell time. An
hourglass has two containers with a narrow
connection between them. They watched how long
it took for water or sand to pour from one container
to another.
People learned to divide hours into minutes. There
are 60 minutes in an hour. Eventually, they divided
minutes into seconds. There are 60 seconds in 1
minute.
WHO INVENTED CLOCKS?
The Chinese may have invented the first ticking
clock about 1,000 years ago. Europeans had clocks
about 800 years ago. Over time, the clocks got
better. They kept time more accurately. Clocks also
got smaller. Watches are small clocks you can
wear on your wrist.
After electricity was discovered, inventors learned
how to make electric clocks. They learned how to
make watches that use batteries.
IS TIME THE SAME ALL OVER EARTH?
Hours, minutes, and seconds are the same amount
of time anywhere on Earth. But Earth is divided into
24 time zones. The time zones look like slices on
a beach ball. There is a one-hour difference
between each time zone and the one next to it. In
the time zone east of the one you live in, it is one
hour later. In the time zone to the west, it is one
hour earlier.
The main time zones in the United States are
called the Eastern, Central, Mountain, and Pacific
time zones. The main time zones in Canada are
the Newfoundland, Atlantic, Eastern, Central,
Mountain, and Pacific time zones.
Microsoft ® Encarta ® 2009. © 1993-2008
Microsoft Corporation. All rights reserved.

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