Earth & Space Education PDF

The Planets The Earth, Sun & Moon The solar system formed about 5,000 million years ago. It consists of the Sun, the Planets, their moons, asteroids and comets. In our Solar System, all 8 planets orbit the Sun which sits in the centre. Space Travel An asteroid is a piece of rock left over from the t...

The Planets The Earth, Sun & Moon The solar system formed about 5,000 million years ago. It consists of the Sun, the Planets, their moons, asteroids and comets. In our Solar System, all 8 planets orbit the Sun which sits in the centre. Space Travel An asteroid is a piece of rock left over from the time when the solar system formed it moves in an orbit around the sun. Comets are objects that are made out of mostly frozen gas, with small amounts of dust. They are often called dirty snowballs! The roughly spherical shape of the Earth can be confirmed by many different types of observation from ground level, aircraft, and spacecraft. The shape causes a number of phenomena that a flat Earth would not. The Solar System Our solar system formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova. When this dust cloud collapsed, it formed a solar nebula—a spinning, swirling disk of material As time passed, material began to clump together due to gravity, forming many objects called planetesimals. Over the course of millions of years, they collided with each other to form the planets and moons. There are thousands of satellites orbiting Earth. The Moon is the only natural satellite of Earth and is not a planet. It orbits the Earth approximately once every 30 days and is 239,000 miles away from the Earth. Ancient astronomers first thought that the Earth was the centre of the universe, and that everything else moved around it in circles. We call this the geocentric model We now know that the sun is at the centre of the universe and the planets move in circles (orbits) around it.. This is called the heliocentric model Phases of the Moon The Moon is not a light source. It does not create its own light. We can only see the Moon because it reflects light from the Sun. The Moon takes approximately 30 days to complete its orbit around the Earth, after which the lunar cycle repeats itself. Day and Night The sun appears to rise and set because of the Earth's rotation on its axis. The Earth makes one complete turn every 24 hours and it rotates toward the east. it is night in some parts of the world while it is day in other parts. The world is divided into 24 different time zones. One for each hour in a day.