The Earth in the Universe

Since ancient times, the movement of celestial bodies has attracted the

interest of human beings.

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The geocentric model

The heliocentric model

There are two theories or models to explain our situation in the Universe :

The geocentric model Ptolemy was a Greek astronomer who lived between 85- 165 A D. He was one of the first people who proposed a theory about the movement of heavenly bodies. This theory stated that the Earth was at the center of the Universe and all celestial bodies revolved around it.

The heliocentric modelNicholas Copernicus was a Polish astronomer

who lived between 1474-1543.Before his time, people believed in the Ptolemy model. He changed this belief when he introduced the heliocentric theory. He claimed that all planets including the Earth, moved around the sun.

Galileo GalileiGalileo Galilei was an Italian astronomer. He

was born at the end of the sixteenth century. He was the first person to use a telescope to look at the sky. This invention was a major step forward in the knowledge of the cosmos. His defense of the heliocentric theory offended the Roman Catholic Church and this almost cost his life. He was sentenced by the Inquisition to house arrest for the rest of his life.

What is a

galaxy?

Galaxies are huge clusters of stars, interstellar gas and dust. They may contain billions or trillions of stars and several planetary systems.

Our galaxy: The Milky Way

The universe contains billions of galaxies. The Milky Way is the galaxy in which our Solar System is located together with other stars and planets.The Milky Way has a spiral shape and has several arms.

We live at this point, it is called Orion Arm

A medium star: The Sun

The Solar System consists of

Satellites are bodies that revolve around the planets.

Asteroids are rocky fragments of variable size.

Comets are bodies of rock, ice and dust

The Solar System

A group of 8 planets, some dwarf planets and 64 satellites.

A belt of asteroids mostly between Mars and Jupiter

Comets

Planets in our Solar System

Mercury

Venus

The Earth

Mars

Jupiter

Saturn

Uranus

Neptune

The Sun

Planets have two movements: a traslation around the sun and rotation around its axis.

Traslation Rotation

Earth Movements

Earth rotates from west to east

Day or night

The rotational motion of the Earth causes what we call “night” and “day”

night

day

Invierno

Los rayos son más perpendiculares a

la superficie terrestre

Seasons are a consequence of translational motion and the tilt of Earth

´s axis

Seasons

The Moon

The moon is the only natural satellite of our planet