UNIT 1. EARTH IN THE UNIVERSE.

What’ the Universe?
The Universe is all the matter, energy, space an time that exists. It is about 15.000 million years old:

●       it is expanding.

●       It began with a huge explosion, the Big Bang.

●       It made up of:

1. galaxies: groups of stars, gas and cosmic dust which gravity holds together.
2. globular cluster: large groups of stars.
3. nebulae:accumulation of cosmic matter and gas.
   1.      2. What are galaxies made of?

Astronomical objects are the different components of a galaxy. We can distinguish between:

•        Stars: astronomical objects that emit light. They are burning balls of gas that reléase large amounts of energy.

•        Planets: don’t emit their own light and orbit around a star. Are made of rock, metal, ice and gas.

•        Satellites: astronomical objects that orbit a planet and are smaller than a planet.

•        Comets are small astronomical objects made of ice, dust and rock that orbit the Sun.

•        Asteroids are small objects that orbit the Sun and made of metal and rock.

•        Meteorites are asteroids or comets which fall to Earth.

1.      3. The Milky Way.

The Milky Way is our Galaxy. It’s a large spiral galaxy and our own solar system is in one of its spiral arms. It has a diameter of around 200.000 light years.

2.THE EARTH’S MOVEMENTS.

The Earth is constantly moving in two different ways: rotation and revolution.

2. 1. Rotation.

Earth spins on its axis in an anti-clockwise direction (west to east). The Sun rises in the East and sets in the West.

Has a length of 24 hours.

The Earth’s axis is tilted at and 23.5ºC. This explains:

•        Sucession of day and night.

•        Regulation of the temperature of the planet.

2. 2. Revolution.

The Earth orbits around the Sun on an elliptical path.

Length: 365 days and 6 hours, because of this we have a leap year, a year with 366 days every four years.

Consequence:

The apparition of the Seasons of the year:

•        When the North Pole is tilted towards the Sun’s rays the days in the Northern Hemisphere are longer and warmer; its summer, meanwhile in the Southern Hemisphere its summer.

•        In spring and autumn, neither pole is tilted away from the Sun and days and nights has the same lenght.

2. 3. Equinox and solstices.

Equinox is the time of the year when the Sun's rays falls perpendicular to the Equator. There are two:

•        Spring equinox (21-22 March) it is the start of the spring in the Northern Hemisphere and of the autumn in the Southern Hemisphere.

•        Autum equinox (September 22-23) it is the start of the autumn in the Northern Hemisphere and of the spring in the Southern.

Solstice is the time of the year when the Sun's rays hits one of the hemispheres directly. There are two:

•        Summer solstice (June 22-23) it is the longest day of the year and the start of the summer in the Northern Hemisphere and of the winter in the Southern.

•        Winter equinox (December 21-22) it is the shortest day of the year in the Norhtern Hemishphere and the start of the winter. In the Southern is the start of the Summer.

2.      4. The Moon.

The Moon is Earth’s only natural satellite. The light of the Moon is a reflection of the Sun’s lifht, because of this the part of the Moon lit up depends on the position of the Moon, the Earth and the Son.

There are four phases of the Moon that happen over 29.5 days:

·        New moon: the Moon is completely dark.

·        Fist quarter: a half of the Moon is lit and the lit part is growing

·        Full moon: the Moon is completey lit.

·        Third quarter: a half of the Moon is lit and the lit part is decreasing.

4. PARALLELS AND MERIDIANS.

To locate any point on earth we draw a series of imaginary lines to create a grid. There are two types: parallels and meridians.

A parallel is a imaginary circle we draw around Earth perpendicular to its axis. The most important ones are:

•        Equator its divides Earth into the Northern and Southern Hemispheres.

•        The Tropic of Cancer in the Northern Hemisphere and the Tropic of Capricorn in the Southern Hemisphere.

•        The Artic Circle in the Northern Hemisphere and the Antartic Hemisphere in the Southern Hemisphere.

We can distinguish several climate zones on Earth limited by paralles:

•        A hot zone between the Equator and the Tropics is the hottest región.

•        Two temperate zones between the tropics and Artic and Antartic circles.

•        Two cold zones within the Artic and Antartic circles.

Meridians are imaginary lines that we draw from the Northern to the Southern Hemispheres.

The main meridian is the Greenwich Meridian that divides Earth into the Western and the Eastern Hemisphere.

Latitude and longitude.

•        Latitude is the distance north or south from the Equator of any point on Earth. Can be North or South. The maximum latitude is 90º (degrees).

•        Longitude is the distance east or west from the Greenwich Meridian of any point on Earth. The maximum longitude is 180º.

Every degree is divided into 60 minutes and a every minute into 60 seconds.

5. TIME ZONES.

A time zone is an area of the Earth where everyone share the same time. Because the Earth takes 24 hours to complete a full rotation the Earth is divided in 24 time zones.

As a reference to measure we use the Greenwich Meridian (Greenwich Mean Time). Each time zone to the west of the Greenwich Meridian is behind the GMT and each time zone to the East is ahead the GMT.

6. REPRESENTING THE EARTH.

The most accurate way to represent the Earth is on a globe because is a sphere, but we need to project the Earth on to a flat Surface.

A map projection is a technique that allow to represent the curve of the Earth on a flat surface.

There are three types of map projections, but all of them have distortions:

•        Cylindrical projection: projects the whole globe on to a cylinder using the Equator as a line of contact. Land masses near the Equator are accurate but the ones near the poles are distorted.

•        Conic projection: Projects a half of the globe on to a cone using the tropics as a line of contact. Represents the temperate zones most accurately.

•        Azimuthal projection: Project a part of the globe on to a flat surface. We use the poles as the points of contact and it’s ideal for mapping the polar regions.

The most commonly uses projections today are:

•        Mercator projection maintains the shape of land masses and seas, but away from the Equator land masses appear bigger that they really are.

•        Gall-Peters projection maintaint the true sizes of the contintents but distorts their shape.

7. MAPS.

•        A map is a reduced representation of the Earth, or a part of the Earth, usually on a flat surface.

•        Cartography is the study and practice of making maps.

•        Cartographer is a person who makes maps.

Scale.

The scale is the relationship between the size of something on a map and its real size. We uses to kinds of scale:

•        Numerical scale is a fraction. The numerator represents a measurements on a map and the denominator represent what that measurement is equal to it in reality.

•        Graphic scale is a line divided into equal segments. Each segment shows us the relationship between measurement on the map and the distance in reality.

The key of a map lists and explain all the symbols of a map.

8. DIFFERENT TYPES OF MAPS.

We use different type os maps to do different things. The main types are:

•        Topographic maps: maps that show the physical geography of a landscape in a great detail:

Show relief using contour lines: lines joinig points of equal elevation in relation to sea level.
Show rivers, lakes and seas along with elements of human geography.
·        Thematic maps show different types of data (population, vegation, etc) connecting it to the geographical área. There are different types: demographic, political, etc.

The national map of Spain is the National Topographic Map produced by the Instituto Geográfico Nacional (IGN). Has a scale of 1:50.000