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KS4 Physics. Earth and Beyond. Contents. Earth and Beyond. The solar system. The life cycles of stars. In orbit. The Universe. Summary activities. The centre of the Universe?. Hundreds of years ago, people thought that the Earth was the centre of the Universe and that
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KS4 Physics Earth and Beyond
Contents Earth and Beyond The solar system The life cycles of stars In orbit The Universe Summary activities
The centre of the Universe? Hundreds of years ago, people thought that the Earth was the centre of the Universe and that the Sun and planets rotated around the Earth! I don’t think so! Nicholas Copernicus, was a Polish astronomer who lived in the 17th century, He studied the stars and discovered that the Earth and the other planets actually rotate around the Sun. Copernicus
Components of the solar system What types of objects make up the Solar System? 1. _____________ 2. _____________ 3. _____________ 4. _____________ 5. _____________ the Sun the planets moons asteroids comets Which of these objects are light sources? The Sun is a star and a light source. It is a massive ball of hot glowing gas and gives out huge amounts of heat and light energy.
The planets The outer planets, apart from Pluto, are made of liquefied gases such as hydrogen, carbon dioxide and ammonia. The four inner planets are small, dense and mostly made of rock. Pluto, the outermost planet, is believed to be made of rock and ice. The asteroids, between Mars and Jupiter, are pieces of rock with diameters from a few km up to 1000 km. diagram 1 not to scale
Comets Most of the planets travel around the Sun in near-circular orbits. Comets also travel around the Sun but in very elliptical orbits. For most of its orbit, a comet is a long way from the Sun. The head of the comet is a lump of ice and dust a few kilometres across. The tail only appears when the comet is near the Sun. It consist of gas and dust which are released by the heat of the Sun. diagram 1
Meteors and meteorites As the Earth moves through space, it collides with lumps of material which burn up in the atmosphere. These are called meteors and can be seen as streaks of light in the night sky. A large meteor may not burn up completely and hits the Earth with a lot of energy. This is called a meteorite. A meteorite impact is one theory to explain why the dinosaurs became extinct. diagram 1
The Sun The Sun is the star at the centre of the Solar System. It is the largest object and contains about 98% of the total mass in the Solar System. The Sun is a massive ball of hot, glowing gas and is mostly made of hydrogen and helium. It is more than 4.5 billion years old! Scientists once thought that the Sun was powered by chemical reactions but this couldn’t explain how it has managed to stay ‘burning’ for billions of years. There must be another process producing the Sun’s energy. Scientists now know that this process is nuclear fusion.
Nuclear fusion In nuclear fusion reactions, lighter atomic nuclei are joined together (fused) to form heavier atomic nuclei. This process releases massive amounts of energy. In our Sun, a typical star, hydrogen is being fused to form helium. This provides the energy for life on Earth. When all the hydrogen is used up, other elements will be fused together to make even heavier elements. Not all elements are made in this way. The heaviest elements, some of which are found in your body, can only be made when stars explode.
The Sun as our energy source The Sun is the source of energy for life on Earth. Where does this energy come from? What would happen on Earth if the Sun suddenly disappeared? The Sun is powered by nuclear fusion reactions. Atomic nuclei are joined together (fused) due to the very high pressures inside the Sun. There would be no light, all plants would die (no photosynthesis), all animals would die (no food source) and temperatures would drop. It would lead to the end of all life on Earth!
Contents Earth and Beyond The solar system The life cycles of stars In orbit The Universe Summary activities
Small stars Expands to form a red giant. Nebula collapses due to its own gravity. Lighter stars, like our Sun, follow this life cycle: Forms a star like our Sun. Outer layers of star drift away to leave a dense white dwarf. Very small nebulae form failed stars.
Massive stars Stars that are much heavier than our Sun follow this life cycle: Forms a star more massive than our Sun. Expands to form a massive red giant. Larger nebula collapses due to its own gravity. Red giant collapses violently in a supernova explosion. Very dense neutron star formed.
Really massive stars The end of the life cycle of really massive stars is different to that of massive stars. After a really massive red giant collapses in a supernova explosion, it leaves a star so dense that not even light can escape its gravitational pull. This is called a black hole! Some scientists believe that there are black holes at the centre of galaxies. If light cannot escape a black hole, then how can a black hole be observed?
Black holes X rays How can a black hole be observed? A black hole cannot be seen directly and even if it could it wouldn’t be black! A black hole is ‘seen’ by observing the effect it has on nearby matter. If there is a star nearby, matter from the star will spiral into the black hole and as it does so the matter emits X ray radiation which can be detected.
Birth of a star What is the correct order for these sentences about how a star is formed? This causes the ‘nebula’ to collapse. When the temperature and pressure are great enough nuclear fusion starts. Gravity causes a dust and gas cloud to condense into a smaller volume. Eventually gravity and the outward pressure of escaping energy is balanced. At this stage, it is called a star. As the nebula collapses, temperatures and pressures inside the nebula increase.
Comparing the life cycles of stars Use these words below to complete the life cycles of different stars: small nebula large nebula nebula massive red giant white dwarf neutron star star larger than our Sun star like our Sun red giant supernova
Comparing the life cycles of stars small nebula large nebula nebula star larger than our Sun star like our Sun massive red giant red giant supernova white dwarf neutron star
Questions about stars • What two elements make up most of our Sun? • What is a nebula? • What process has allowed the Sun to emit light and heat radiation over billions of years? • Which is the most dense, a white dwarf or a neutron star? • Describe the possible fate of a star similar to our Sun. hydrogen and helium A huge cloud of gas and dust from which a star is born. nuclear fusion neutron star red giant white dwarf
Contents Earth and Beyond The solar system The life cycles of stars In orbit The Universe Summary activities
Orbiting the Sun • What force keeps the planets in orbit around the Sun? • Which planet shown will feel this force… • a) …the strongest? b) …the weakest? the Sun’s gravity not to scale
Questions about satellites • What are the two types of satellite? • Give an example of each type? natural and artificial natural – the Moon artificial – navigation, spy, military, weather, communications 3. Why are certain satellites, such as the Hubble Space Telescope, put into space? To view the Universe above the Earth’s atmosphere which can obstruct view from Earth.
Artificial satellites – different orbits The satellite’s orbit passes over the poles, whilst the Earth spins underneath. This allows large areas of Earth to be seen and is used for mapping and weather monitoring. geostationary orbit polar orbit Satellite stays above the same location on the Earth’s surface. This means that the speed of its orbit matches the Earth’s rotation.
Comparing orbits Complete this the table comparing the different types of orbits that artificial satellites can follow? low high fast slow 3 - 4 1 overpoles above equator weather communications
Which type of orbit? Do these uses of satellites involve a polar orbit or a geostationary orbit? communications geostationary spy polar weather polar and geostationary navigation geostationary monitoring ocean temperatures polar
Contents Earth and Beyond The solar system The life cycles of stars In orbit The Universe Summary activities
Matching words and definitions There are nine of these in our Solar System. The Earth is one. Our Sun is one. Billions of stars together - ours is called the Milky Way. The Sun, planets, moons, asteroids and comets make up this. All the galaxies and everything else. a star a planet a galaxy the Universe the Solar System
Identify the different bodies a galaxy a star the Universe
The Doppler effect Think about the noise a plane makes as it passes you. As the plane approaches, it sounds higher pitched... …as it moves away from you, it sounds lower pitched. This apparent shift in frequency is called the Doppler effect. • The same thing happens with light: • The wavelength of light emitted by approaching objects appears to be shortened (blue-shifted); • The wavelength of light emitted by receding objects appears to be increased (red-shifted).
Hubble and the expanding Universe Edwin Hubble (1889-1953) was a famous scientist who examined the light from nearby galaxies. He made two important observations: Edwin Hubble (1889-1953) was a famous scientist who examined the light from nearby galaxies. He made two important observations: • That most of the galaxies’ light was shifted towards the red end of the spectrum; • The further away a galaxy was, the more its light was red-shifted. • That most of the galaxies’ light was shifted towards the red end of the spectrum; • The further away a galaxy was, the more its light was red-shifted. • From his observations, Hubble made these conclusions: • That most galaxies were moving away from our own; • The further away a galaxy was, the faster it was moving away from us; • That the Universe must beexpanding. • From his observations, Hubble made these conclusions: • That most galaxies were moving away from our own; • The further away a galaxy was, the faster it was moving away from us; • That the Universe must be expanding.
The big-bang theory The big-bang theory states that the Universe is expanding due to a large ‘explosion’ (big bang) billions of years ago. • Evidence to support this theory includes: • The Cosmic Microwave Background Radiation (CMB), which is thought to be an ‘echo’ of the initial explosion. • Hubble’s observations about red-shifted light. • This theory gives rise to different fates for the Universe: • If the mass of the Universe is large enough, it will eventually start to contract due to gravity – closed Universe. • If the mass of the Universe is smaller, it will expand forever as there is not enough gravity to halt its expansion – open Universe.
Steady state theory The steady state theory states that the Universe is expanding and, as it expands, matter is created to maintain a uniform universal density of matter. Evidence to support this theory is Hubble’s observations about red-shifted light. However, the steady state theory has become less popular since the discovery of Cosmic Microwave Background Radiation (CMB).
Are we alone? There are 1021 stars in the universe. There must be life on planets around some of them. There are many different opinions about life in the Universe: For life to exist there must be liquid water, on a planet or moon and oxygen. If there are aliens, they would have contacted us by now. The Universe is so big, even if there are aliens, they are too far away for us to ever meet them. We are all aliens, life began on comets and asteroids and transferred to the Earth when they collided with it. Life exists on Earth and only on Earth. If there are aliens they will probably not look like you or me.
Is there life out there? Many people believe that we are not the only intelligent life in the Universe. The challenge for scientists is to find evidence of other life.
Contents Earth and Beyond The solar system The life cycles of stars In orbit The Universe Summary activities
Glossary (1) • black hole –An object in space that forms after a really massive star collapses in a supernova. Its gravity is so strong that nothing can escape its pull. • comet –A lump of rock and ice which has a very elliptical orbit around the Sun. • galaxy –A vast collection of billions of stars. • geostationary orbit –The path of a satellite that stays above the same position on the Earth’s surface and orbits at the same speed as the Earth rotates. • meteor –A lump of material from space that burns up in the Earth’s atmosphere. • meteorite– A large meteor that does not completely burn up in the Earth’s atmosphere and crashes to Earth. • nebula – A massive cloud of gas and dust in which a star is formed.
Glossary (2) • neutron star – The very dense core that remains after a massive red giant collapses in a supernova. • nuclear fusion – The process in which lighter atomic nuclei are joined together to form heavier atomic nuclei and a massive amount of energy is released. • polar orbit – The path of a satellite which passes over the North and South poles. • satellite – Any object that is in orbit around a larger object. • red giant – A star that has expanded and has a red glow. • supernova – The huge explosion that occurs when a massive red giant is at the end of its life. • white dwarf – The core that remains after the outer layers of a small red giant drift away.
