9J Gravity and space

1. 9J Gravity and space 9JGravity and space Gravity Old and new ideas Space travel and satellites

2. 9J Gravity and space Gravity

3. 9J Keeping your feet on the ground gravity 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...

4. 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?

5. 9J Galactic Gnome Inc. Remember that on Earth1 kg weighs 10 N. gravitationalfield strength (in N/kg) weight = mass × (in N) (in kg) gravitational fieldstrength on Earth THE BIG DAN1.1 kg DIGBY0.4 kg BOB0.1 kg COMMANDER0.5 kg = 10 N/kg 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!

6. 9J Galactic Gnome Inc. Work out the tax due for each gnome. 1 Galacto per newton 33 11 2 8 40 Does a gnome’s mass change on its new planet?

7. 9J The NASA diet? launch pad on Earth low Earth orbit on surface of Moon in space between Earth and Moon Distances not to scale An astronaut’s weight changes on a journey to the Moon. Match these weights to the astronaut’s position. 0 N 730 N 750 N 125 N 750 N 730 N 125 N 0 N What happens at C? Why is C nearer the Moon than the Earth?

8. 9J Are you on solid ground? Gravity is a force, and forces are measured in newtons. TRUE! TRUE! Gravity is holding you and the Earth together even now! TRUE! Your weight is a measure of how much the Earth is attracting you (and you are attracting it!). TRUE! The Moon’s gravity is only one-sixth of the Earth’s. FALSE! Magnetism is a different force from gravity. But they are both forces that act at a distance. FALSE! 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. TRUE! Gravity depends upon the mass of an object. The smaller the object, the smaller its gravitational pull. True or False? 1.Gravity is measured in newtons. 2.Gravity is a force that attracts two bodies. 7.The mass of a body changes, but its weight stays the same when the force of gravity changes. • 6. A 6 N weight on Earth would weigh only 1 N on the Moon. 5.The force of gravity on the surface of the Moon is lower than on Earth because the Moon has a smaller mass. 4.Weight is the force of gravity acting on a body near the Earth. 3.Magnetism is the opposite force to gravity.

9. 9J Gravity and space Old and new ideas

10. 9J The old ones are the best? Thousands of years ago people moved these enormous rocks hundreds of miles to make Stonehenge. 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. What did a Stonehenge-builder believe about the Earth and the Sun?

11. 9J Stonehenge, the Sun and stars For Stonehenge-builders the Earth was flat. 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. How clever do you think the Stonehenge-builders were? Were their ideas sensible for their time?

12. 9J The Greeks have it... 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. It’s a disc floating in water. It’s a sphere rotating around a huge fire. The Greeks were probably the first people to study the Earth and the Sun scientifically. Match each idea about the Earth to the correct person. 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. Pythagoras Aristotle Aristarchus Thales

13. 9J Towards a modern view After the Greeks our view of the Universe hardly changed for another thousand years. Ideas built up slowly. CopernicusThe Earth and planets orbit the Sun. Tycho BracheThe 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. Why was it so hard to work out how the Universe works?

14. 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.

15. 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.

16. 9J Gravity and space Space travel and satellites

17. 9J Space words word meaning 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 Match each word to its correct meaning. gravity solar orbit lunar ellipse geostationary orbit ellipse gravity geostationary lunar solar

18. 9J Working outwards from the Sun Earth Jupiter Saturn Neptune Uranus Mars Pluto Venus Label the planets in order, starting with Mercury nearest the Sun. Mercury Sun Distances not to scale

19. 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.

20. 9J Satellite links So the Moon is a satellite of the Earth. What’s a satellite? There are also pieces of broken spaceship and other debris in orbit, that have been trapped by the Earth’s gravitational field. Anything that’s in orbit around a larger body. Scientists put artificial satellites in orbit round the Earth too. Artificial satellites have different orbits.Can you name three types of orbit?

21. 9J Orbits N N S S N S A low-Earth orbit is closer to the Earth’s surface. The three types of satellite orbit are shown below. A geostationary orbit keeps the satellite above the same point on the Earth. Satellites travelling over the North and South poles have polar orbits. How long does a satellite in a geostationary orbit take to orbit the Earth? Which satellite has the shortest orbit time? Why?

22. 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. Research satellites measure things like the concentration of ozone or the temperature of the Earth’s oceans. Survey satellites look down on the Earth and find out about anything from mineral deposits to the size of the Sahara desert. 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?

23. 9J Satellite images This picture of volcanoes in Ecuador was taken from a satellite. What might people use images like this for?

24. 9J Satellite images for research The ‘hole’ in the ozone layer as seen by a satellite. The purple areas show the thinnest part of the ozone layer. This picture was created by putting together a number of separate images. What has caused the hole in the ozone layer?

25. 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?