Page 34 - Geography for Secondary Schools Student’s Book Form One

Geography for Secondary Schools
Student’s Book Form One

Solstice and equinox
The tilting nature of the earth’s axis causes Activity 3.5
parts of its surface to receive different (a) Design a globe by using locally
amount of sunlight at different times of available materials to represent the
the year. This situation leads to solstice
and equinox. Solstice comes from the Latin Earth. Use flashlight to represent
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word solstitium, which contains two words: the Sun, then place the globe at an
sol the term that means Sun and sistere that angle to represent the Earth’s tilt;
means stand still. The solstice, therefore, (b) Turn on the flashlight and shine it
literally means “sun-stand still”. Solstice directly at the centre of the globe,
is a phenomenon that occurs when the simulating the Sun’s rays;
earth’s poles are mostly inclined towards or
away from the sun, causing the earth’s pole (c) Observe the way light hits the globe
which is inclined towards the Sun to receive and write notes on what you have
maximum sunlight. This makes the most observed in relation to the equinox.
inclined pole towards the sun to experience
the longest day in the year. During this
time, the Sun is vertically overhead in (iii) Varying lengths of day and night at
respective tropic on specific dates. The different times of the year.
southern hemisphere gets the maximum The lengths of day and night are not the
intensity of the sun’s rays on December same across the world because the earth’s
22 which is the Summer Solstice in the axis is inclined to its plane at an angle of
nd
tropic of Capricorn. At the same time, it is
the Winter Solstice at the tropic of Cancer. 66½°. Had the earth’s axis been vertical to
The northern hemisphere solstice occurs on its orbital plane, all the parts of the earth
June 21 commonly known as the Summer would have the same duration of days and
st
Solstice at the tropic of Cancer. At the same nights throughout the year. Places along the
time, it is winter solstice at the tropic of equator experience nearly equal day and
Capricorn. night throughout the year, but northwards
The equinox simply refers to equal lengths or southwards towards the poles, the lengths
of day and night. Due to the tilting of the of day and night vary with latitude. For
earth’s axis, there are only two times of instance, when the overhead sun is in the
the year when the sun is directly overhead Northern Hemisphere, the days are longer
at noon at the equator. This results into
equal distribution of sun rays between than the nights in that hemisphere. At the
the Southern and Northern Hemispheres. North Pole (90°N), daylight is experienced
The equinoxes occur on March 21 and for six months without sunset. While at the
st
September 23 every year. The March South Pole (90°S), darkness is experienced
rd
equinox is referred to as vernal equinox for six months In contrast, when the
in the Northern Hemisphere and autumnal overhead sun is in the Southern Hemisphere,
equinox in the Southern Hemisphere. In the days are longer than the nights in the
addition, the September equinox is known Southern Hemisphere. Thus, at the South
as autumnal equinox in the Northern Pole (90°S), daylight is experienced for six
Hemisphere and vernal equinox in the
Southern Hemisphere. months without sunset.
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