Page 148 - Innovator's Science-8

Position
Earth's orbit favourable for
around Sun eclipses Lunar eclipse at
Moon's slightly this position No eclipses
titled orbit
around Earth on these full
and new
Moon days
Solar eclipse
at these
No eclipses positions
Science on these full
Bytes
and new
Moon days
Position
Testimony favourable for
• The word eclipse comes eclipses Lunar eclipse at
this position
from the Greek word
ekleipsis which means
‘being abandoned’. quitedifferent from the regular phases.
• There are 3 types of
solar Eclipse: Par al, A solar eclipse occurs when the Moon comes between the Sun and Earth
Annual and Total. and blocks sunlight from reaching us.
However, such eclipses do not occur every month because the Moon's orbit

is slightly tilted compared to Earth's orbit around the Sun. Only when the Sun,
Earth, and Moon are perfectly aligned do these special events take place.

HOW DID CALENDARS COME INTO EXISTENCE?

When we look from Earth, it seems like the Sun rises in the east, moves
across the sky, and sets in the west every day, and then does the same again

the next day. This happens because the Earth is spinning around its own
axis. This spinning causes day and night and is the reason we measure a day
as a unit of time. It takes the Sun roughly 24 hours to return to the same
highest point in the sky. This average time, called a mean solar day , became
the standard way to define one complete rotation of Earth. We can tell

when the Sun is at its highest by looking at the shadows objects make—the
shadow is shortest when the Sun is at the highest point.

Measuring a Day

• Choose a small, flat area that receives Sunlight throughout the day. Fix a
1 m stick vertically into the ground as shown in the given figure.

• Begin your observation at 11:00 a.m. Every
minute, mark a dot on the ground at the tip of
the stick's shadow. Continue marking dots
until about 1:10 p.m.

• Identify when the shadow was shortest and
find out its time by counting the number of
Length of the shadow at
dots. Record this time in the given table. different times during the day.
Repeat this exercise for the next few days.

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