The ShoutTitulo de la entrada Titulo de la entradaTitulo de la entrada Titulo de la entradaTitulo de la entrada Titulo de la entradaTitulo de la entrada Titulo de la entradaTitulo de la entrada Titulo de la entradaTitulo de la entrada




UNIT 1: THE EARTH AND THE SOLAR SYSTEM


1 THE UNIVERSE


The Universe is made up of all the astronomical objects that are found in space. According to the Big Bang theory, the Universe formed almost 14 billion years ago. The Big Bang was a gigantic explosion that propelled matter and energy into space to create galaxies.

Galaxies are groups of starsStars are astronomical objects that release energy in the form of light and heat. Our galaxy is called the Milky Way, and it is made up of thousands of millions of stars.

THE SOLAR SYSTEM

The Solar System is made up of the Sun and the planets and satellites that orbit, or revolve, around it.

The Sun is a star in the Milky Way. It is a medium-sized star compared to other stars in the Universe. The Sun is made up of gasesand nuclear reactions inside it release light and heat.

The planets are spherical bodies that do not release their own light. They orbit the SunTheir orbit is elliptical, like an elongated circle.

Satellites are solid bodies that orbit the planets and do not release their own lightThe Moon is the Earth’s satellite.

There are other astronomical objects in space:
- Asteroids are solid rocks that orbit the Sun.
Comets are giant balls of cosmic dust and ice. When they pass close to the Sun they begin to melt, leaving behind a long trail of dust and gas.
- Meteors are small objects that start to burn as they enter the Earth’s atmosphere.

THE EARTH

The Earth formed around 4.6 billion years ago. It is the only planet in the Solar System where life exists. This is the result of three important factors:

The Earth’s distance from the Sun means that it has the right temperature – it is not too hot or too cold for life.

- It has an atmosphere, which is a layer of gases that protects it from harmful radiation from the Sun.This includes gases like oxygen that are essential for life.

It has liquid water, which is necessary for all living things

THE SHAPE AND DIMENSIONS OF THE EARTH

The Earth is sphericalbuit is not a perfect sphere. It is widest at the Equatorand slightly flattened at both poles. The Earth’s surface is about 1,000 times the size of Spain. About 71 per cent of it is covered by water, and 29 per cent by land, in the form of continents and islands.


2. LATITUDE AND LONGITUDE

Imaginary lines called parallels and meridians are used on maps and globes of the EarthThese lines cross each other to form an imaginary grid, or network, that allows us to locate any point on the Earth’s surface.

Parallels are imaginary lines that run east to west around the Earth. The most famous parallel is the Equator, which circles the Earth at an equal distance from the poles. It divides the Earth into two equal halves, the Northern Hemisphere and the Southern Hemisphere. The Equator is the widest parallel, and the other parallels become smaller as they get closer to the poles. The Equator is at zero degrees, and the poles at 90 degrees.

 Meridians are imaginary lines that run from the North Pole to the South Pole. The Prime Meridian or Greenwich Meridian is at 0 degrees. The other meridians run 180 degrees east and 180 degrees west from the Prime Meridian.

THE GEOGRAPHC COORDINATES

It is possible to locate any given point on the Earth’s surface by establishing its geographic coordinates, which describe the exact position where a parallel and meridian meet, in degrees.
We use the coordinates for both latitude and longitude to establish a location.

- Latitude is the distance between a point on the Earth’s surface and the Equator. The Equator is at 0 degrees and the poles are at 90 degreesWe measure parallels in degrees, minutes and seconds. We add N (North) for the Northern Hemisphere and S (South) for the Southern Hemisphere.

- Longitude is the distance between a point on the Earth’s surface and the Prime Meridian. We measure it in degrees, minutes and seconds. Longitude goes from 0 degrees at the Prime Meridian to 180 degrees West or 180 degrees East.

3. THE EARTH’S ROTATION

The Earth rotates once on its axis every 24 hours. This rotation is what causes day and night and an impression of the Sun’s apparent movement across the sky.

Day and nightAt any moment in time the Sun’s light only illuminates part of the Earth’s surface, while the rest of the Earth is in darkness. This gives rise to day and night. It stops any particular part of the Earth from becoming too hot or too cold.

The Sun’s apparent movementWhen we look up at the Sun during the day, it appears to be rising in the East and setting in the West. This is not in fact caused by the Sun’s motion, but is actually because the Earth is rotating in the opposite directionThe Sun’s apparent movement is useful for orientation on the Earth’s surface. We can find the cardinal points (North, South, East and West) by observing the Sun’s movementThe Earth’s axis of rotation, connecting the North and South Poles, always points North.

TIME ZONES

We have seen that as the Earth rotates, parts of the world are in sunlight whilst others are in darkness. Solar time is not the same on all parts of the planet. We divide the Earth into 24 time zones that correspond to the 24 hours of a day. As the Earth is a sphere of 360 degrees, each time zone is 15 degrees across. There is one hour in a time zone.
 Our point of reference is the Prime, or Greenwich, Meridian at 0 degrees. As we go east through each time zone, we set the clock forward by one hour. As we go west through each time zone we set the clock back by one hour.
The meridian at 180 degrees longitude is opposite the Prime Meridian. This meridian is called the International Date Line. We put the date forward or back by a day when we cross this line.

4. THE EARTH’S REVOLUTION

The Earth’s elliptical orbit around the Sun is called a revolution. It takes the Earth just over a year to complete a full revolution.
We add an extra day to the month of February every four years to allow for the extra six hours. A year with 366 days is called a leap year.
The Earth’s revolution and its tilted axis of rotation determine:
The seasons. The changing angle of the Sun’s rays as they reach the Earth’s surface gives rise to the seasons: spring, summer, autumn and winter.

The changing length of day and nightDue to the tilt of the Earth’s axis as it orbits the Sun, each hemisphere is illuminated differently.
The Sun’s rays are vertical at the Equator at the spring equinox, and the autumn equinox. Consequently, both hemispheres receive the same amount of sunlight, and day and night have the same length.
At the solstices, the Sun’s rays are vertical at the tropics. The Sun’s rays are vertical at the Tropic of Cancer at the summer solstice in the Northern Hemisphere.
The Sun’s rays are vertical at the Tropic of Capricorn at the winter solstice in the Northern hemisphere.

CLIMATE ZONES

The tilt of the Earth’s axis of rotation influences the world’s climate zones. The Sun’s rays reach inter-tropical regions at a direct angle for most of the year. However, they reach the Earth’s surface at a much smaller angle closer to the poles. Consequently, different parts of the Earth’s surface receive varying amounts of solar energy.

The tropics are located between the Tropic of Cancer and the Tropic of Capricorn, and they receive the greatest amount of solar energyTemperatures are high throughout the year, and there is little difference between the seasons.

The two temperate zones are located between the tropics and the polar circles, in each hemisphere. In these zones, the number of daylight hours gradually falls between the summer and the winter solstices. There are four seasons.

The two polar regions are located between the polar circles and the poles, and receive little solar energy. Temperatures are always very low, and there are big differences between the length of day and night. The Sun is visible in the sky for only six months of the year at each pole, in the summer. Even then it provides very little heat because its rays hit the polar regions at a low angle.

5. REPRESENTATION OF THE EARTH

Maps are representations of all, or part, of the Earth on a flat surface. The study and practice of making maps is called cartography. We use maps in different ways: to locate a place, to identify geographical features, such as land relief or water, and to collect other types of information.

All maps have the following characteristics:

They are reduced because geographical space is represented on a small surface.

- They are simplified because they only show certain features.

They take a standard form, using specific colours and symbols defined in a key.

MAP PROJECTIONS

Maps distort the Earth’s surface because they are representations of a three dimensional object on a flat surface. In fact, globes show the Earth’s surface more accurately because they are spherical like the Earth. We use a technique called map projection to make maps:

- A cylindrical projectionProjection onto a rectangular map of the world is accurate at the equator, but distorted at the polesIt is also known as the Mercator projection.

A projection onto a plane. This is a good way of representing the poles.

- A conical projection. We can only show part of the Earth in this way.

SCALE

Scale is the ratio between a distance on the ground and its representation on a map. There are two types of scales:

-          A graphic scale is a line divided into equal parts that allows us to use a ruler to measure distances on a map.

-          A numerical scale is the relationship between a unit of distance on a map and the real distance.

HOW TO MEASURE DISTANCES ON A MAP

Using a graphic scale, we first measure the distance on the map and then compare it to the scale.
A numerical scale shows the relationship between centimetres on the map and kilometres on the ground.

MAPS AND GEOGRAPHIC TECHNOLOGIES

There are many kinds of maps. They include the following:

Topographic maps show the main natural and man-made features of an area, such as mountains, rivers and lakes, towns and roads.

Thematic maps show a particular feature of an area, using symbols or colours. They can give information such as climate, economic activities, natural resources, political frontiers and population density.

Plans are very large-scale maps of a small area, like a town or neighbourhood, and include a lot of detail.




OTHER RESPRESENTATION OF HE EARTH

Many areas of technological progress, such as computers and satellites, have made it possible to improve our representations of geographic data. A geographic information system (GIS) brings together many different types of information.

Aerial photography gives us images of the Earth from aeroplanes, while space images are taken from manmade satellites in spaceWe can use this information to see meteorological phenomena, or observe landscapes.

Remote sensing is the collection of information from a distance. It can help to predict natural disasters, such as hurricanes. Aeroplanes and satellites collect information, which is then processed by a computer. It can be converted into digital images.

- Virtual maps are created on computers. They can show great detail and may be three-dimensional.
Unit 1: The Earth and the Solar System


No hay comentarios:

Publicar un comentario