The document discusses the motions and major divisions of the Earth. It describes how the Earth rotates on its axis once every 24 hours, causing the cycle of day and night. It also revolves around the sun once every 365 days. The document outlines the Equator and important latitudes and longitude lines that divide the Earth, such as the Tropic of Cancer and Prime Meridian. It explains phenomena related to day and night, such as varying day length depending on location and season, as well as different timekeeping systems used worldwide.

1. Republic of the Philippines
PangasinanState University - Bayambang Campus
COLLEGE OF TEACHER EDUCATION
Social Sciences Department
Bayambang, Pangasinan
WRITTEN REPORT IN SOCIAL STUDIES 101
Name: Julie Ann Acosta Sison Year and Section: BSE I-3
Topic: Major Division of the Earth Date:
Day and Night Phenomena: Standard Time
The Motions of the Earth: Rotation and Revolution
Introduction
Earth is our home planet. Scientists think Earth formed billions of years ago.
Four planets in the solar system are bigger than Earth. Three planets are smaller.
It is the third-closest planet to the sun. Only Mercury and Venus are closer.
Earth has been called the "Goldilocks planet." In the story "Goldilocks and
the Three Bears," a little girl named Goldilocks liked everything just right. Her
porridge couldn't be too hot or too cold. And her bed couldn't be too hard or too
soft. On Earth, everything is just right for living things. It's warm, but not too warm.
And it has water, but not too much water.
Body
The earth is one of the nine planets that make up our solar system. Though
it isn't one of the largest planets, it still has a circumference of 25,000 miles or
40,000 kilometers. It is also constantly in motion. In fact, the Earth orbits the sun
at an incredible 66,500 rate of miles an hour. Yet, it still takes the earth 365 days,
or one year, to complete a full rotation around the sun. Moreover, as the Earth
orbits the sun, it spins on its axis in a counter-clock wise motion. It too rotates at a
fast pace of 1042 miles per hour. On its axis, the earth rotates 360 degrees every
24 hours. Or you can look at it as it takes one day to complete a full circle. Divided
up into an hourly rate, the earth rotates 15 degrees every hour (360/24). This
number plays an important role in determining time zones.
The Earth is a sphere that rotates around its axis. If we draw a line passing
through the center of the Earth along its rotational axis, the line would pass through
the North and the South Pole.
Motions of the Earth
Rotation is when a planet or moon turns all the way around or spins on its axis
one time. The axis of rotation is an imaginary line going from the north pole to the
south pole. When a planet or moon travels once around an object this is considered
a revolution.
Rotation – the Earth spins on an imaginary line called ‘axis ‘from east to
west direction.
“The Earth spins on its axis once every 24 hours or 1 day.”

2. Revolution –
movement around the Sun in an elliptical orbit.
Complete r = 365 ¼ days.
Speed = 29.8 km/s
Major Divisions of the Earth
The Equator is an imaginary line perpendicular to this axis. It is equidistant
from the North and South poles, and divides the globe into the Northern
Hemisphere and the Southern Hemisphere.
Most locations on the Equator experience consistently high temperatures
throughout the year. They also experience almost 12 hours of daylight every day
during the year. On the Equinoxes –September and March – the sun is directly
overhead the Equator, resulting in exactly 12 hour days and 12 hour nights.
Often called parallels or circles of latitude, latitudes are imaginary circles
parallel to the Equator. They are named after the angle created by a line
connecting the latitude and the center of the Earth, and the line connecting the
Equator and the center of the Earth.
Latitudes specify the North-South position of a location on the globe. Locations in
the Northern Hemisphere are identified by northern latitudes and are assigned a
suffix of N for north. Southern Hemisphere locations, on the other hand, are on
southern latitudes and are assigned a suffix of S for south.
The Equator represents 0° latitudes, while the North and South Poles
represent 90° North and 90° South latitudes. In addition to the Equator, there are
four other major latitudes that are usually found on maps and globes.
 The Arctic Circle is the latitude 66° 34′ North. All locations falling North of
this latitude are said to be in the Arctic Circle. The Antarctic Circle on the
other hand, is the latitude 66° 34′ south. Any locations falling south of this
latitude are said to be in the Antarctic Circle.
Places in both these circles experience extreme weather, and experience the
midnight sun, as well as polar nights.
 The latitude 23.5° North is also known as the Tropic of Cancer. It marks
the northern-most position on the Earth, where the Sun is directly overhead
at least once a year. This happens during the June Solstice, when the
Earth’s Northern Hemisphere is tilted towards the Sun.
 The Tropic of Capricorn is the latitude that lies at 23.5° South of the
Equator. It is the southern-most position on the globe, where the sun is
directly overhead during the December Solstice.
Sometimes, latitudes north of the Equator are denoted by a positive sign.
Latitudes south of the Equator are given negative values. This eliminates the need
to add whether the specified latitude is north or south of the Equator.
Longitudes are geographical positioning markers that run from the
geographical North Pole to the geographical South Pole, intersecting the Equator.
They meet at both Poles, and specify the East-West position of a location.
Longitudes are therefore imaginary circles that intersect the North and South
Poles, and the Equator. Half of a longitudinal circle is known as a Meridian.
Meridians are perpendicular to every latitude.

3. Unlike, latitudes, there is no obvious central longitude. However, in order to
measure the position of a location based on the longitude, cartographers and
geographers over the course of history have designated different locations as the
main longitudinal reference point. Today, the meridian line through Greenwich,
England is considered as the reference point for longitudes. This line is also known
as the Prime Meridian.
The Prime Meridian is set as 0° longitudes and it divides the Earth into the
Eastern and the Western Hemisphere. All the other longitudes are measured, and
named after the angle they make with respect to the center of the Earth from the
intersection of the Meridian and the Equator.
Since a sphere has 360 degrees, the Earth is divided into 360 longitudes.
The meridian right opposite the Prime Meridian (on the other side of the Earth) is
the 180° longitude. Modern timekeeping systems use longitudes as references to
keep time. Time zones are defined by the Prime Meridian and the longitudes.
Day and Night Phenomena
For most of here on planet Earth, sunrise, sunset, and cycle of day and night
(aka. the diurnal cycle) is just a simple fact of life. As a result of seasonal changes
that happen with every passing year, the length of day and night can vary — and
be either longer or shorter — by just a few hours.
But in some regions of the world, this cycle is completely different. In these
parts, located around the Earth’s poles, the Sun does not set during certain times
of the year. And there are also seasonal periods where a single night can last many
days.
Earth’s rotation occurs from west to east, which is why the Sun always
appears to be rising on the eastern horizon and setting on the western. If you could
view the Earth from above, looking down at the northern polar region, the planet
would appear to be rotating counter-clockwise. However, viewed from the southern
polar region, it appears to be rotating clockwise.
The Earth rotates once in about 24 hours with respect to the Sun and once
every 23 hours 56 minutes and 4 seconds with respect to the stars. What’s more,
its central axis is aligned with two stars. The northern axis points outward to
Polaris, hence why it is called “the North Star”, while its southern axis points to
Sigma Octantis.
As already noted, due to the Earth’s axial tilt (or obliquity), day and night are
not evenly divided. If the Earth’s axis were perpendicular to its orbital plane around
the Sun, all places on Earth would experience equal amounts of day and night (i.e.
12 hours of day and night, respectively) every day during the year and there would
be no seasonal variability.
Instead, at any given time of the year, one hemisphere is pointed slightly
more towards the Sun, leaving the other pointed away. During this time, one

4. hemisphere will be experiencing warmer temperatures and longer days while the
other will experience colder temperatures and longer nights.
Of course, since the Earth is rotating around the Sun and not just on its axis,
this process is reversed during the course of a year. Every six months, the Sun
undergoes a half orbit and changes positions to the other side of the Sun, allowing
the other hemisphere to experience longer days and warmer temperatures.
Consequently, in extreme places like the North and South pole, daylight or
nighttime can last for days. Those times of the year when the northern and
southern hemispheres experience their longest days and nights are called
solstices, which occur twice a year for the northern and southern hemispheres.
The Summer Solstice takes place between June 20th and 22nd in the
northern hemisphere and between December 20th and 23rd each year in the
southern hemisphere. The Winter Solstice occurs at the same time but in reverse
– between Dec. 20th and 23rd for the northern hemisphere and June 20th and
22nd for the southern hemisphere.
According to NOAA, around the Winter Solstice at the North Pole there will
be no sunlight or even twilight beginning in early October, and the darkness lasts
until the beginning of dawn in early March.
Conversely, around the Summer Solstice, the North Pole stays in full
sunlight all day long throughout the entire summer (unless there are clouds). After
the Summer Solstice, the sun starts to sink towards the horizon.
Another common feature in the cycle of day and night is the visibility of the
Moon, the stars, and other celestial bodies. Technically, we don’t always see the
Moon at night. On certain days, when the Moon is well-positioned between the
Earth and the Sun, it is visible during the daytime. However, the stars and other
planets of our Solar System are only visible at night after the Sun has fully set.
The reason for this is because the light of these objects is too faint to be
seen during daylight hours. The Sun, being the closest star to us and the most
radiant object visible from Earth, naturally obscures them when it is overhead.
However, with the Earth tilted away from the Sun, we are able to see the Moon
radiating the Sun’s light more clearly, and the star’s light is detectable.
On an especially clear night, and assuming light pollution is not a major
factor, the glowing band of the Milky Way and other clouds of dust and gas may
also be visible in the night sky. These objects are more distant than the stars in
our vicinity of the Galaxy, and therefore have less luminosity and are more difficult
to see.
Another interesting thing about the cycle of day and night is that it is getting
slower with time. This is due to the tidal effects the Moon has on Earth’s rotation,
which is making days longer (but only marginally). According to atomic clocks

5. around the world, the modern day is about 1.7 milliseconds longer than it was a
century ago – a change which may require the addition of more leap seconds in
the future.
International Date Line is an imaginary line of longitude on the Earth’s surface
located at about 180 degrees east (or west) of the Greenwich Meridian.
Standard Time is a uniform time for places in approximately the same longitude,
established in a country or region by law or custom.
Local Time is the time at a particular place as measured from the sun's transit
over the meridian at that place.
Biological Time a daily cycle of activity observed in many living organisms
Calendar a chart or series of pages showing the days, weeks, and months of a
particular year, or giving particular seasonal information.
Time Zone is a region throughout which the same standard time is used.
Sidereal Day is the time between two consecutive transits of the First Point of
Aries. It represents the time taken by the earth to rotate on its axis relative to the
stars, and is almost four minutes shorter than the solar day because of the
earth's orbital motion.
Solar Day is the time between successive meridian transits of the sun at a
particular place. The time between successive passages of the mean sun across
the meridian.
Greenwich Mean Time is the mean solar time of the meridian of Greenwich
used historically as the prime basis of standard time throughout the world
—called also Greenwich time
Coordinated Universal Time is the international standard of time that is
kept by atomic clocks around the world.
Universal Time is a time standard based on Earth's rotation. It is a modern
continuation of Greenwich Mean Time (GMT)
Daylight Saving Time is the practice of setting the clocks forward one hour from
standard time during the summer months, and back again in the fall, in order to
make better use of natural daylight.
References:
http://www.universetoday.com/59707/what-causes-day-and-night/
http://science.howstuffworks.com/environmental/earth/geophysics/earth2.htm
http://www.worldatlas.com/aatlas/imagee.htm
http://www.timeanddate.com/time/