TOPIC 2: THE SOLAR SYSTEM | GEOGRAPHY FORM 1
Solar System is the arrangement of sun, planets and other solid objects in the space in relation to the position of the sun. The planets are not arranged in a single line from the sun, they are scattered in the space.
Components of the Solar System
Below are the components that make up the solar system:
- The Sun
- Meteors; and
Importance of the Components of Solar System
Components of the Solar System are important because:
1. They produce heat and light potential for living organisms, for example the Sun
2. The provide habitat for humans and other living organisms, for example the Earth
3. They form craters which later become attractive sites for tourism activities, for example meteors which produce meteorites that fall on the Earth’s surface and form craters
The Sun is a star.
Dimension of the Sun in Relation to Other Space Bodies
Dimension of the Sun relative to other Space Bodies: The diameter of the sun is 1.4 million kilometers
Characteristics of the Sun
The Sun is composed of approximately 75% Hydrogen, 23% Helium and 3% other elements. Therefore, the elements which make up the Earth comprise only a small fraction of the materials which form the Sun.
These include Carbon, Iron, Oxygen, Silicon etc. The Sun is the only source of light and heat that the planet receives. The temperature of the Sun is estimated to be 20,000,000 degrees Centigrade.
The Term Solar Energy
Solar energy is the heat and light produced from the Sun. The Sun is the source of all energy on the Earth.
Different Uses of Solar Energy
Some of the different uses of Solar energy include:
Drying clothes, meat, fish, fruits and grains
Photosynthesis ingrowing plants to manufacture their own food
Generation of electricity
Formation of coal, gas and oil
Formation of clouds and rainfall through evaporation of water caused by the heat of the Sun
Giving power to small radios and running small telephone systems by using silicon solar batteries
Source of Vitamin D to human bodies as the bodies absorb Sunlight
For domestic purposes like cooking food, heating, water.
How the Use of Solar Energy Promotes Environmental Conservation
Utilization of Solar energy in manufacturing industries reduces the production of chlorine from industrially produced chlorofluorocarbon gases which cause depletion of the ozone layer.
The depletion of the ozone layer causes global warming. Solar energy is used as an alternative source of energy, therefore reducing the depletion of forests for charcoal and firewood.
How Solar Energy May Contribute to Emancipation of Women
REDUCED TIME BURDENS LEADING TO HIGHER-EARNING JOBS AND INCREASED ENTREPRENEURIAL OPPORTUNITIES
Women are often disproportionately responsible for household duties. This is particularly acute in rural settings, where women spend considerable time on tasks such as collecting firewood for basic cooking, heating, and lighting needs.
Access to energy allows for more efficient products—from those as basic as a solar lantern to those as advanced as a washing machine.
These products can reduce the time burdens of domestic responsibilities and create time for more productive, formal engagement in the local economy outside the home.
Empirical studies that have examined the impact of electrification on female labor rates in developing country settings reinforce this hypothesis.
IMPROVED BASELINE CONDITIONS LEADING TO GREATER ACCESS TO ECONOMIC OPPORTUNITIES
There are a multitude of studies that demonstrate that improved access to electricity improves baseline living conditions for women.
These studies show improvements to women’s health through cleaner indoor air; better nutrition and food safety due to improved refrigeration; and improved health knowledge through better access to mass media and more time to read.
Interior and exterior lighting in rural settings often means improved security for women, enabling greater mobility to engage in productive activities under safe conditions.
Anecdotal evidence also shows improved education for girls as a result of access to electricity, although most empirical studies do not show gender-differentiated impacts.
Improving these baseline conditions facilitates the ease by which women can participate in the local economy: Healthy, safe, and informed individuals are more apt to be productive.
Planets in the Solar System
Planets are bodies that revolve around the Sun.
Previously, they included Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Pluto does not qualify to be a planet anymore as it is the smallest and does not revolve around the Sun.
Therefore, there are currently officially only eight planets in our Solar System.
The word ‘Planet’ originates from the Greek word ‘Planetai’ which means ‘Wandering’ as the planets seem to move about in the Sky as wandering stars.
All planets revolve around the Sun in the same direction in orbits that are elliptical and nearly in the same plane. The time taken to complete an orbit depends on the distance from the Sun.
Relative Distance of Planets from the Earth
How far is each planet from Earth?
sually when people ask this question, what they mean is “What is the distance between the orbit of Earth and the orbit of each planet?” or “What is the closest that each planet comes to Earth?” (These are essentially the same question, because the planets can’t get any closer than their orbital spacing allows.)
You can compute this in a rough way by assuming that the orbits are circular and coplanar, and looking at the planet-to-Sun distance for each planet.
Since the distances are so large, we usually express them in Astronomical Units (AU). (AnAUis the average distance from Earth to the Sun, about 150 million kilometers or 93 million miles.) The table below lists the distance of each planet from the Sun in AU.
Average distance from Sun in AU
|Pluto (dwarf planet)||39.48|
Other bodies in the Solar System
Characteristics of Comets, Asteroids, Meteors and Satellites
Comets are objects with leading heads and bright tails in the Sky. Sometimes they can be seen at night. They are composed of ice crystals and fragments of solid matter.
They have highly elongated orbits around the Sun. They can be seen from the Earth only when they come close to the Sun.
Asteroids are solid heavenly bodies revolving around the Sun. They are mostly found between the orbits of Mars and Jupiter.
They are in thousands and the largest has adiameter of just less than 800 Kilometres. The bodies can only be seen with a telescope because they are very far away.
Meteors are pieces of hard matter falling from outer Space. They can be seen when they come close to the earth, at about 110-145 Kilometres, whereas as a result of friction with the atmosphere, they become hot and usually disintegrated.
They fall on the Earth’s surface as large boulders known as meteorites, or a meteor if it is one. These bodies are made of Nickel, Iron and Silica.
Satellites are the moons of the Planets and they can be defined as the small bodies which rotate on their axis and revolve around the Sun.
There are only seven (7) planets which have satellites apart from 57 satellites in the Solar System. The number of satellites depends on the size and nature of the planet.
Local Incidents Linked to Meteorites
There are two known meteorites in Tanzania. One is found in Mbozi district in Mbeya region and the other is inMalampaka in the Kwimba district in Mwanza region. These falling meteorites have resulted in the formation of craters.
The Earth is the only Planet among the planets in the Solar System that is known to support life. (Pluto does not qualify as a planet any moreasit is the smallest and does not revolve around the sun).
The Earth is made up of the atmosphere (air), hydrosphere (water bodies), the solid crust, molten materials and the biosphere (living organism).
Water bodies cover about three quarters of the Earth’s surface.
The Shape of the Earth and its Evidence
There are many ways to prove that the earth is spherical. The following are some of them:
1. CIRCUMNAVIGATION OF THE EARTH:
The first voyage around the world by Ferdinand Magellan and his crew, from 1519 to 1522, proved beyond doubt that the earth is spherical.
No traveller going round the world by land or sea has ever encountered an abrupt edge, over which he would fall. Modern air routes and ocean navigation are based on the assumption that the earth is round.
2. THE CIRCULAR HORIZON:
The distant horizon viewed from the deck of a ship at sea, or from a cliff on land is always and everywhere circular in shape. This circular horizon widens with increasing altitude and could only be seen on a spherical body.
3. SHIP’S VISIBILITY:
When a ship appears over the distant horizon, the top of the mast is seen first before the hull. In the same way, when it leaves habour, its disappearance over the curved surface is equally gradual. If the earth were flat, the entire ship would be seen or obscured all at once.
4. SUNRISE AND SUNSET:
The sun rises and sets at different times in different places. As the earth rotates from west to east, places in the east see the sun earlier than those in the west.
If the earth were flat, the whole world would have sunrise and sunset at the same time. But we know this is not so.
5. THE LUNAR ECLIPSE:
The shadow cast by the earth on the moon during a lunar eclipse is always circular. It takes the outline of an arc of a circle. Only a sphere can cast such a circular shadow.
6. PLANETARY BODIES ARE SPHERICAL:
All observations from telescopes reveal that the planetary bodies, the sun, moon, satellites and stars have circular outlines from whichever angle you see them.
They are strictly spheres. Earth, by analogy, cannot be the only exception.
7. DRIVING POLES ON LEVEL GROUND ON A CURVED EARTH:
Engineers when driving poles of equal length at regular intervals on the ground have found they do not give a perfect horizontal level.
The centre pole normally projects slightly above the poles at either end because of the curvature of the earth.
Surveyors and field engineers therefore have to make certain corrections for this inevitable curvature, i.e. 12.6 cm to 1 km.
8. SPACE PHOTOGRAPHS:
Pictures taken from high altitudes by rockets and satellites show clearly the curved edge of the earth. This is perhaps the most convincing and the most up-to-date proof of the earth’s sphericity.
Types of Earth’s Movements
The Earth is in motion all the time. People cannot feel this motion because they move with it like all other planets. There are two types of movements of the earth, namely:
- The rotation of the Earth on its own axis
- The revolution of the Earth around the Sun
The Term Rotation
Rotation refers to thespinning of a body on its axis. The earth rotates or spins on its axis in an anti-clockwise direction, from West to East through 3600 in 24 hours. Thus for every 15 degrees of rotation, the earth takes one hour which is the same as four minutes for every 1 degree.
An axis is an imaginary line joining the N (North) and S (South) poles through the center of the Earth.
Note: The rotation of the earth is very rapid although it is difficult to feel itsmotion. At the equator, every point of the earth’s surface is traveling Eastwards at about 1600 Km per hour. At latitude 40 degrees, the speed is about 1280 Km per hr.
Evidence to Prove that the Earth Rotates
Below is evidence that proves that the Earth rotates:
During the night, stars appear to move across the sky from West to East
If one travels in a fast moving vehicle, will notice trees and other objects on both sides of the road are moving fast in the opposite direction
Rising of the sun over the eastern horizon in the morning. This shows that the point of observation, that is south, is moving by rotation from West to East
Day and Night. During the Earth’s rotations some regions face the sun while others do not face it. Thise regions facing the sun experience day time whereas the regions which are not facing the sun are in darkness (night). This proves that the earth is rotating.
Significances of Earth’s Rotation
Alternation of day and night: Rotation of the earth causes the sides of the earth which face the sun to experience daylight which is the day, whereas the side that is not facing the sun at that time will be in darkness (night).
The occurrence of tides in the ocean caused by gravitational forces of the moon and sun upon the rotation of the Earth
Deflection of winds and ocean current
Time difference between longitudes: The rotation is responsible for difference in time between different places on Earth. It causes the difference of one hour in every 15 degree interval between longitudes. The Earth rotates from West to East and takes 24 hours to complete one rotation. The difference in time is 4 minutes for each degree of longitude
The Term Revolution
Revolution is defined as the movement of one body around another. The earth revolves around the sun in an elliptical orbit. Due to the elliptical shape of the earth orbit the sun is closer to the earth at one point of the year than at another.
The farthest (maximum distance) position from the sun in orbit of the earth is called aphelion while the nearest position of the earth to the Sun is known as perihelion.
The Process of Revolution
The Earth is at aphelion each year on 4th July, when it is at the maximum distance of 152 million kilometer form the sun. The earth is at perihelion each year on 3rd January when it is at the minimum distance of 147 million kilometers.
The earth’s revolution around the sun takes a year (365¼ days) therefore the speed of revolution is about 29.6 kilometers per second. A normal year has only 365 days. The remaining fraction of ¼ day is added once in four years to make a leap year of 366 days.
The Result of the Earth’s Revolution Around the Sun
The four seasons of the year; summer, autumn, winter and spring. A season is one of the distinct period into which the year may be divided.
In the northern hemisphere the summer season months are May, June and July. Autumn months are August, September and October, winter months are November, December and January and spring months are February, March and April.
In the southern hemisphere summer season months are November, December and January. Autumn months are February, March and April.
Winter months are May, June and July and spring months are August, September and October. Equinox refers to the period when the sun is overhead at the equator.
Change in the position of the midday sun at different times of the year. As the earth revolves around the sun its position changes and makes it appear as if it is the sun moving.
Varying lengths of the day and night at different times of the year. The axis of the earth is inclined to its elliptical plane at a certain angle of 66.5 degrees.
If the axis of the earth were vertical, the sun rays would be overhead at the Equator, thus all places on the earth would always experience 12 hours of daylight and 12 hours of night
The Importance of the Parallels and Meridians
The Parallels and Meridians
Latitude refers to the angular distance North or South of the equator measured in degrees, minutes and seconds. The equator is given a value of 00.
It is an imaginary line which divides the Earth into two hemispheres. The Northern hemisphere has a latitude of 90o N and the Southern hemisphere has a latitude of 90o S.
Therefore, Parallels of latitude are particular lines joining all points on the surface of the earth and making an angle of 300o N with the equatorial plane.
How Latitudes and Longitudes are Determined
THE IMPORTANT PARALLELS
The important parallels include:
- Equator 0o
- Tropic of Cancer 23.5oN
- Tropic of Capricorn 23.5oS
- Arctic Circles 66.5oN
- The Atlantic Circle 66.5oS
Refers to the angular distance measured in degrees East and West of the Greenwich Meridian.
Prime Meridian is the line running through the poles and the Greenwich observatory near London. It is also known as Greenwich Meridian.
All lines of longitude are semi circles of equal length. Lines of longitude are also called meridians. There are 360o in a circle, 180o lie east of the Greenwich Meridian and the other 180o west of Greenwich.
The Greenwich lines have been chosen by convention (meaning that any other lines could have served the same purpose).
CALCULATION OF TIME
The earth rotates on its own axis from West to East once every twenty four hours. This means 360oof longitude are covered in a period of 24 hours or 1o in four minutes.
There are places on a given meridian that experience midday at the same time. Time recorded along the same meridian is known as Local Mean Time (LMT).
When the local time of Accra is 2.00pm what will be the local time of Bangui 15 degrees E.
15 degrees – 0 degrees = 15 degrees
15 x 4 minutes = 60
60/60 = 1 hour
Accra 2.00 pm + 1.OO hour time difference = 3.00 pm
Importance of a Great Circle
Any circle which divides the globe into hemispheres is a great circle. The equator is a great circle and Greenwich Meridian together with Meridian 1800 make another great circle. The number of great circles is limit less.
The importance of great circles in geological applications of spherical projections is that they can represent planes. The center of a great circle is called its pole.
If you know a great circle, you can find its pole, and if you know the pole, you can find the great circle. Thus it is possible to represent a plane by a single point.
This fact is extensively used in advanced projection techniques. The perimeter of equatorial plane is called primitive circle.
CHARACTERISTICS OF GREAT CIRCLES
1. All great circles divide the earth (sphere) into two hemispheres.
2. A great circle is the largest possible circle that can be drawn on the surface of the sphere.
3. The radius of great circles is the same as the radius of the earth.
USES OF GREAT CIRCLES
Great circles are used to plot routes for ships crossing the vast oceans and aircraft flying great distance in space.
Ships and aircraft travel by following great circles in order to save fuel and time because the shortest route between two places is along the circle of the great circle which passes through them.
Importance of Parallels and Meridians
Parallels are another name for lines of latitude. You will see that these lines do not converge, or come together, anywhere on the globe.
We call these parallels because they are always an equal distance apart. The first parallel is the equator. It is latitude 0. Latitude measures distance north and south from the Equator. Parallels are lines that circle the globe.
Meridians are another name for lines of longitude. These lines are drawn on maps and globes so that people can locate places. Meridians are lines that run from the North Pole to the South Pole. Meridians are not parallel.
They converge or come together at the Poles. They number from the Prime Meridian (line 0) to 180W and from the Prime Meridian to 180E.
Calculate local time
What is the local time at Morogoro-Tanzania when it is noon at Kigali-Rwanda?
1. Note the longitudinal position between the two points Kigali 30°E and Morogoro 45°E
2. Find the difference in degrees of longitude between Kigali and Morogoro 45 degrees – 30 degrees = 15 degrees
3. Multiply the difference by 4 minutes 15°x 4 minutes = 60 minutes; 60 Ã· 60 = 1 hour
4. The time difference is to be added (+) in case of places to the East of a point. In case of place to the West, the time difference is subtracted (-).
Since Morogoro is to the East of Kigali, Morogoro time will be ahead of that of Kigali’s by 1 hour, therefore time for Morogoro will be:12.00 noon + 1 hour = 1.00 pm.
Time and Time Zone
Time zone refers to a zone where standard time is accepted throughout a longitudinal zone 150 in width.
Essence of Time and Time Zone
The importance of time zones is to avoid the problems in telling time if every place had its own time set according to the local mean time.
The timetable of various human activities such as television and radio programs would be confusing if they had to show different times.
As the time varies from place to place, different stretches of land agreed to adopt the time from certain meridian, that time is known as standard time.
East African countries agreed to adopt standard time taken from meridian of 45oE.When a whole stretch of land keeps to the same standard time that stretch of land forms a time zone.
Variation of Standard Time in a Single Country
Large countries like USA, China, etc have several standard time zones with each time zone covering about 15 degrees of longitude. There are 24 times zones in the world. The starting point for dividing the world into 24 times zones is the Greenwich Meridian. The standard time for Greenwich is known as the Greenwich Meridian time (GMT).
International Date Line
The International Date Line is the line where date is changed or calendar day begins. This line follows approximately the 1800 meridian.
Location of International Date Line
When the time is 6.00pm on Monday 25th December, at Greenwich, the time at 1800 E longitude will be 12 hours ahead of Greenwich Mean Time.
The time at 1800 E will be 6.00am on Tuesday 26th December. Therefore if one travels eastwards and crosses the date line, one will gain a day whereas one who travels westwards across the line will loose a day.