© OUP: To be used solely in purchaser’s school or college 9J Gravity and space Gravity Old and new ideas 9J Gravity and space Space travel and satellites

© OUP: To be used solely in purchaser’s school or college 9J Gravity and space Gravity

© OUP: To be used solely in purchaser’s school or college 9J Keeping your feet on the ground Wherever you are on Earth, the same force keeps your feet on the ground. It holds our atmosphere around us and keeps the oceans on the Earth. What is it? You remember – it ’ s...

© OUP: To be used solely in purchaser’s school or college 9J Feel the force Gravity is a force that acts between two objects. It depends on two things. How does gravity depend on mass and distance?

© OUP: To be used solely in purchaser’s school or college 9J Galactic Gnome Inc. Galactic Gnome Inc. exports garden gnomes to planets across the Universe. What do these gnomes weigh on Earth? The company pays tax when each gnome reaches its new home planet. For every newton of weight they pay 1 Galacto. Get ready to work out some tax bills! weight = mass × (in N) (in kg) gravitational field strength (in N/kg) = 10 N/kg gravitational field strength on Earth Remember that on Earth 1 kg weighs 10 N. BIG DAN 1.1 kg DIGBY 0.4 kg BOB 0.1 kg COMMANDER 0.5 kg THE

© OUP: To be used solely in purchaser’s school or college 9J Galactic Gnome Inc. Work out the tax due for each gnome. Does a gnome’s mass change on its new planet? 1 Galacto per newton gnomeweight on Earth (N) export to planet … gravity compared with Earth ’ s tax due (Galacto) Big Dan11Sirius 7 3  Big Dan11Betelgeuse 3 1  Digby 4Kessell System  Bob 1Nebula 2 8  The Commander 5Nebula 2 8 

© OUP: To be used solely in purchaser’s school or college launch pad on Earth low Earth orbit in space between Earth and Moon on surface of Moon Distances not to scale 9J The NASA diet? An astronaut’s weight changes on a journey to the Moon. Match these weights to the astronaut’s position. 0 N730 N750 N125 N What happens at C? 750 N 730 N 0 N 125 N Why is C nearer the Moon than the Earth?

© OUP: To be used solely in purchaser’s school or college Gravity is a force, and forces are measured in newtons. TRUE! 9J Are you on solid ground? 1. Gravity is measured in newtons.2. Gravity is a force that attracts two bodies.3. Magnetism is the opposite force to gravity.4. Weight is the force of gravity acting on a body near the Earth. 5. The force of gravity on the surface of the Moon is lower than on Earth because the Moon has a smaller mass. 6.A 6 N weight on Earth would weigh only 1 N on the Moon. 7. The mass of a body changes, but its weight stays the same when the force of gravity changes. True or False? Gravity is holding you and the Earth together even now! TRUE! Magnetism is a different force from gravity. But they are both forces that act at a distance. FALSE!Your weight is a measure of how much the Earth is attracting you (and you are attracting it!). TRUE!Gravity depends upon the mass of an object. The smaller the object, the smaller its gravitational pull. TRUE! The Moon’s gravity is only one-sixth of the Earth’s. TRUE!Wrong way round! The weight changes because it depends on the gravitational force. The mass stays the same because it depends on how much ‘stuff’ there is in the body. FALSE!

© OUP: To be used solely in purchaser’s school or college Old and new ideas 9J Gravity and space

© OUP: To be used solely in purchaser’s school or college 9J The old ones are the best? They must have been very clever engineers. Would you know how to do it? But their ideas of the world and space were much more limited. Thousands of years ago people moved these enormous rocks hundreds of miles to make Stonehenge. What did a Stonehenge-builder believe about the Earth and the Sun?

© OUP: To be used solely in purchaser’s school or college 9J Stonehenge, the Sun and stars For Stonehenge-builders the Earth was flat. How clever do you think the Stonehenge-builders were? Were their ideas sensible for their time? The Sun was a giant fire and the Moon was … well, we don ’ t know exactly. We do know that these ancient people could predict eclipses with great accuracy.

© OUP: To be used solely in purchaser’s school or college 9J The Greeks have it... Pythagoras Thales AristotleAristarchus The Greeks were probably the first people to study the Earth and the Sun scientifically. It ’ s a sphere at the centre of the Universe. It ’ s a sphere rotating around a huge fire. It ’ s a sphere that turns on its axis every 24 hours and moves around the Sun with all the other planets. It ’ s a disc floating in water. Match each idea about the Earth to the correct person. It ’ s a sphere rotating around a huge fire. It ’ s a disc floating in water. It ’ s a sphere at the centre of the Universe. It ’ s a sphere that turns on its axis every 24 hours and moves around the Sun with all the other planets.

© OUP: To be used solely in purchaser’s school or college 9J Towards a modern view After the Greeks our view of the Universe hardly changed for another thousand years. Ideas built up slowly. Why was it so hard to work out how the Universe works? Copernicus The Earth and planets orbit the Sun. Tycho Brache The planets orbit the Sun, but the Sun and Moon orbit the Earth. Kepler The Earth and planets move around the Sun in ellipses. Galileo The Earth and planets orbit the Sun. The Moon orbits the Earth. Jupiter also has moons orbiting it.

© OUP: To be used solely in purchaser’s school or college 9J Quiz How much do you know about our Universe? 1.The Moon orbits the Earth in… a) a circle b) an ellipse c) a spaceship. 2. Jupiter’s gravitational pull is… a) larger than Earth’s b) smaller than Earth’s c) the same as Earth’s.

© OUP: To be used solely in purchaser’s school or college 9J Quiz 3.The Sun is at the centre of the… a) Earth b) Universe c) Solar System. 4. The stars and planets stay in their places because of… a) glue b) gravity c) speed.

© OUP: To be used solely in purchaser’s school or college Space travel and satellites 9J Gravity and space

© OUP: To be used solely in purchaser’s school or college 9J Space words Match each word to its correct meaning. gravity solarorbitlunarellipsegeostationary orbit ellipse gravity geostationary lunar solar wordmeaning the path a satellite takes around a body a ‘ flattened circle ’ shape force that pulls two bodies towards each other describes a satellite that is always above the same point on the Earth ’ s surface to do with the Moon to do with the Sun

© OUP: To be used solely in purchaser’s school or college 9J Working outwards from the Sun Label the planets in order, starting with Mercury nearest the Sun. Sun Mercury Venus Earth Mars JupiterSaturn Uranus Neptune Pluto Distances not to scale

© OUP: To be used solely in purchaser’s school or college 9J Let’s stay together Why do planets orbit the Sun? It ’ s the result of gravity. What will happen if you switch the gravity off? Explain how gravity keeps the planet orbiting the Sun.

© OUP: To be used solely in purchaser’s school or college 9J Satellite links Artificial satellites have different orbits. Can you name three types of orbit? What ’ s a satellite? Anything that ’ s in orbit around a larger body. So the Moon is a satellite of the Earth. Scientists put artificial satellites in orbit round the Earth too. There are also pieces of broken spaceship and other debris in orbit, that have been trapped by the Earth ’ s gravitational field.

© OUP: To be used solely in purchaser’s school or college N S 9J Orbits Which satellite has the shortest orbit time? Why? A geostationary orbit keeps the satellite above the same point on the Earth. N S Satellites travelling over the North and South poles have polar orbits. A low-Earth orbit is closer to the Earth ’ s surface. N S The three types of satellite orbit are shown below. How long does a satellite in a geostationary orbit take to orbit the Earth?

© OUP: To be used solely in purchaser’s school or college 9J What are satellites for? Weather satellites take pictures of weather systems moving across the globe to help meteorologists predict the weather. Communications satellites relay messages from mobile phones and television stations around the world. Survey satellites look down on the Earth and find out about anything from mineral deposits to the size of the Sahara desert. Research satellites measure things like the concentration of ozone or the temperature of the Earth ’ s oceans. The Hubble telescope is a satellite orbiting the Earth that looks out at stars and galaxies in the very distant Universe. Why does the Hubble telescope take better pictures than telescopes on Earth?

© OUP: To be used solely in purchaser’s school or college 9J Satellite images This picture of volcanoes in Ecuador was taken from a satellite. What might people use images like this for?

© OUP: To be used solely in purchaser’s school or college 9J Satellite images for research The purple areas show the thinnest part of the ozone layer. What has caused the hole in the ozone layer? The ‘hole’ in the ozone layer as seen by a satellite. This picture was created by putting together a number of separate images.

© OUP: To be used solely in purchaser’s school or college 9J Weather forecasting You can see the clouds in this weather satellite image. By putting together a sequence of images you can see the weather moving across the UK. How do you think satellite pictures help meteorologists forecast the weather?