1. What is planet Earth like? A planet in the solar system Our knowledge of the universe has improved greatly over time. This is a result of the progress of astronomy and the use of sophisticated instruments, such as telescopes and artificial satellites. The universe is made up of galaxies, which are clusters of millions of stars. Many stars have planets and other natural objects that revolve around them and form planetar y systems. This is the case in our own solar system. The solar system is made up of: (2) A star (the Sun). Eight planets. Many satellites and other natural objects (dwarf planets, asteroids, comets, etc.). The Moon is the Earth's only satellite. 1. Planet Earth seen from space How is life on Earth possible? Earth has a number of conditions that make it the only known planet on which life exists. (1) Distance from the Sun The distance of the Earth from the Sun makes the temperature of the Earth's surface moderate. If the Earth were closer or further away from the Sun, life would be impossible because it would be too hot or too cold. Atmosphere This gaseous layer around the Earth regulates the planet's temperature: it prevents Earth from getting too hot during the day and too cold at night. The atmosphere also contains gases that are essential for living things. Water Almost three quarters of the surface of planet Earth is covered by water. This water is mostly in liquid form. Many organisms live in water. Furthermore, water is essential for the survival of all living things. Mercury SUN Venus Earth Mars Jupiter Saturn Uranus Neptune 2. The solar system WORK WITH THE IMAGES List the planets of our solar system and state where Earth is with respect to the Sun. Look at the biosphere. (3) Below which altitude do we find the greatest concentration of living things? What is the lower limit for life? List the layers of the geosphere (4) and indicate the thickness of each layer. Name one more characteristic of each layer. 10
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