AQA GCSE 1b-7 The Universe

1. AQA GCSE 1b-7The Universe AQA GCSE Physics pages 106 to 115 AQA GCSE Science pages 310 to 319 April 10th, 2010

2. AQA GCSE Specification THE UNIVERSE 11.7 What do we know about the origins of the Universe and how it continues to change? Using skills, knowledge and understanding of how science works: • to compare and contrast the particular advantages and disadvantages of using different types of telescope on Earth and in space to make observations on and deductions about the universe. Skills, knowledge and understanding of how science works set in the context of: • If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency. • There is a red-shift in light observed from most distant galaxies. The further away galaxies are the bigger the red-shift. • How the observed red-shift provides evidence that the universe is expanding and supports the ‘big bang’ theory (that the universe began from a very small initial point). • Observations of the solar system and the galaxies in the universe can be carried out on the Earth or from space. • Observations are made with telescopes that may detect visible light or other electromagnetic radiations such as radio waves or X-rays.

3. The Doppler Effect As the ambulance travels forwards: The sound wave in front is compressed - decreasing its wavelength - increasing its frequency The sound wave behind is stretched out: - increasing its wavelength - decreasing its frequency A B C D A B C D E ambulance sound demo

4. The Doppler Effect, discovered in 1842 by Christian Doppler, also occurs with light waves. With light waves: In front of the moving object decreasing wavelength and increasing frequency makes the light BLUER - known as BLUE SHIFT Behind the moving object increasing wavelength and decreasing frequency makes the light REDER - known as RED SHIFT

5. Galactic red-shift In 1929 Edwin Hubble discovered that the light from distant galaxies was red-shifted. He found that the red shift was proportional to the distance to a distant galaxy. Therefore the more distant a galaxy is away from us the faster it is moving away from us. Note: Hubble’s observations, and many more since, only apply to DISTANT GALAXIES. Some near by ones, for example the Andromeda Galaxy, are moving towards us.

6. The expansion of the Universe Hubble’s observations tell us that distant galaxies are receding from us and that the further they are away the faster they are moving away from us. Hence the Universe is expanding. Balloon model of the expanding Universe The space between the galaxies expands and so the galaxies grow further apart

7. Choose appropriate words to fill in the gaps below: When a wave source is _______ away from an observer the wave emitted is spread out. This is called the _______ Effect and with light it is a cause of ________. Distant galaxies show red-shift that _________ with their distance away. More distant ________ are therefore moving away from us with ________ speeds. The red-shit shown by _______ galaxies is evidence that the Universe is _________. moving Doppler red-shift increases galaxies greater distant expanding WORD SELECTION: Doppler increases moving red-shift galaxies expanding distant greater

8. Expanding Universe - 7stones Red Shift - eChalk Doppler Effect - Sound with microphone Doppler Effect - Iona Doppler Effect - Explore Science Doppler Effect (Quick Sound Demo) - Iona Doppler effect - NTNU Doppler effect - ambulance - Fendt Doppler Shift with light - eChalk Doppler Shift with sound - eChalk Doppler Shift with sound effects- eChalk Red Shift - eChalk Introduction Page to AQA Origin of the Universe Evidence of the Big Bang including Red Shift - includes applet showing the affect of expansion on wavelength Simulations

9. The expanding UniverseNotes questions from pages 106/310 & 107/311 • (a) What is a galaxy? (b) What is the name of our galaxy? • (a) What is a light year? (b) How big is our galaxy? • Copy and answer question (a) on page 106/310. • (a) What is ‘red shift’ (b) What causes red shift? (c) What is ‘blue shift’ (d) What causes blue shift? • Explain how the Doppler effect occurs with sound waves. • (a) What did Edwin Hubble discover about distant galaxies? (b) Explain how his discovery led on to the idea of an expanding Universe. • Copy and answer questions (b) and (c) on page 107/311. • Copy the Key Points on page 107/311. • Answer the summary questions on page 107/311.

10. In text questions: Because they are so far away. It is blue-shifted because its wavelength is reduced. Galaxy Y Summary questions: (a) Orbiting (b) Expanding (c) Receding (d) Approaching 2. (a) Earth, Sun, Andromeda galaxy, Universe. (b) (i) Planet, star. (ii) Red-shift, galaxy The expanding Universe ANSWERS

11. The Big Bang theory The Big Bang theory is an explanation for the origin of the Universe. It states that: • the Universe is expanding after exploding from a very small initial point. • space, time and all matter were created in the Big Bang. The latest observations indicate that the Big Bang took place about 13 500 million years ago. This theory was not generally accepted until 1965 before which an alternative explanation for the expansion of the Universe called the ‘Steady State theory’ was dominant. In this theory new matter is continually created in the gap left as the Universe expands.

12. The microwave detector used by Penzias and Wilson Background microwave radiation This radiation was first detected by Penzias and Wilson in 1965. The Big bang produced very short wavelength gamma rays. As space has expanded these rays have been stretched our so much that they now have the much longer wavelengths of microwaves. Expanding Universe

13. A map of the microwave background radiation The presence of this radiation throughout the Universe is evidence that supports the Big Bang theory.

14. Choose appropriate words to fill in the gaps below: The Big Bang theory is an explanation for the _______ of the Universe. According to this theory all space, matter and _____ were created from an exploding very small _______ nearly 14 billion years ago. Since this time the Universe has been _________ causing the initial _______ rays produced at the Big Bang to have spread out to become __________. The detection of this _________ radiation in 1965 led astronomers to ________ the previous Steady State theory. origin time point expanding gamma microwaves background abandon WORD SELECTION: expanding time microwaves origin point gamma background abandon

15. Origin of the Universe - Powerpoint presentation by JAA Expanding Universe - 7stones Expanding Universe - eChalk Age of the Universe - eChalk Big Bang Time Machine - School Science Introduction Page to AQA Origin of the Universe The Big Bang Evidence of the Big Bang including Red Shift - includes applet showing the affect of expansion on wavelength Test bite on the Origin of the Universe Simulations

16. The Big Bang Notes questions from pages 108/312 & 109/313 • What is the ‘Big Bang’ theory of the origin of the Universe? • What was the ‘Steady State’ theory? • (a) What is ‘background microwave radiation’? (b) Why does this radiation give support to the ‘Big Bang’ theory? • (a) Copy Figure 3 on page 109/313 and outline the various possible futures of the Universe. (b) What determines which future will occur? • Copy and answer questions (a), (b) and (c) on pages 108/312 and 109/313. • Copy the Key Points on page 109/313. • Answer the summary questions on page 109/313.

17. In text questions: Nothing. It will be stretched even more to longer wavelengths. The expansion might reverse or it might just gradually stop. Summary questions: (a) Created (b) Expanded (c) Detected (d) Stretched 2. (a) The Universe will continue to expand. (b) The expansion will stop and reverse. The Big Bang ANSWERS

18. Light Telescope Jodrell Bank Radio Telescope The Hubble Space Telescope Looking into space Observations of the solar system and the galaxies in the universe can be carried out on the Earth or from space. Observations are made with telescopes that may detect visible light or other electromagnetic radiations such as radio waves or X-rays.

19. The Mount Palomar telescope in California, with an objective mirror of 5m (200 inches), was for many years the world’s largest telescope Optical (visible light) telescopes Optical telescopes use a concave mirror or a convex lens to collect light from distant objects. The greater the size of the mirror or lens: • the more light is collected • the more the image can be magnified • the brighter the image seen - the more detail seen in the image produced.

20. These are used to study strong radio sources such as the Sun, Jupiter, the Milky Way and many other galaxies. The structure of the Milky Way can be studied using radio waves as these waves are able to travel through gas clouds where visible light cannot. Our knowledge of what is at the centre of our galaxy has been obtained primarily by using radio telescopes. The bigger the telescope, the more detail it can map out and the further away it can detect radio sources. Radio telescopes

21. The Earth’s atmosphere affects telescopes on the ground. - It scatters the light from space objects and makes their images fuzzy. - It stops most microwaves, infra-red, ultra-violet, X-ray and gamma ray radiation. Satellites telescopes are not affected by the Earth’s atmosphere. Objects such as exploding stars and black holes can be studied with such telescopes. Also far more detailed optical images can be obtained. The Hubble Space Telescope Satellite telescopes

22. Many of the most spectacular modern images are in fact composites images taken of a number of regions of the electromagnetic spectrum. The picture below of the Whirlpool Galaxy is such an example taken by the Hubble Space Telescope. It is of the galaxy taken with ultra-violet and infra-red as well as with visible light.

23. The Crab Nebula (M1) at different wavelengths

24. What are the disadvantages of using satellite telescopes? They require rockets, for example the Space Shuttle, to be deployed – this is very expensive and dangerous. They are very difficult to maintain if something goes wrong or wears out. They are very difficult to update as technology advances. Question

25. Choose appropriate words to fill in the gaps below: Telescopes are used to observe objects in ______. There are ___________ for all regions of the electromagnetic _________ as some objects cannot be observed using ______ light only. For example the main evidence supporting the existence of _________ holes comes from the observation of X-rays. Satellites have been used in recent years as they do not have the disadvantage of ___________ distortion or being dependent on _________ conditions. space telescopes spectrum visible black atmospheric weather WORD SELECTION: spectrum black weather visible space telescopes atmospheric

26. Refracting Telescope - Fendt K Taggart's photographs taken through SLOOH - Online telescopes based in the Canary Islands & Chile BBC Bitesize Revision: Telescopes Simulations

27. Looking into space Notes questions from pages 110/314 & 111/315 • In what ways do telescopes allow us to see more in the night sky? • (a) What advantages do space telescopes have over ground based ones? (b) What are their disadvantages? • (a) What are radio telescopes used for? (b) Why should their dishes be as large as possible? • What are satellite detectors used for? • Copy and answer questions (a), (b), (c) and (d) on pages 110/314 and 111/315. • Copy the Key Points on page 111/315. • Answer the summary questions on page 111/315.

28. In text questions: A shooting star. The telescope collects more light from a star than the unaided eye does. So stars too faint to be seen with the unaided eye can be seen with a telescope. HST is in space above the atmosphere. The infra-red radiation is absorbed by the molecules of the gases in the atmosphere. Summary questions: (a) Light, radio waves. (b) Gamma rays, infra-red radiation. 2. (a) Light from objects in space has to pass through the Earth’s atmosphere to reach ground-based telescopes. The Earth’s atmosphere scatters the light slightly and ‘smudges’ the images out. HST is above the Earth’s atmosphere, so its images aren’t affected. (b) Gamma rays can’t pass through the atmosphere, so the detectors need to be above the atmosphere whereas radio waves can pass through the atmosphere. (c) (i) Massive exploding stars. (ii) Planets beyond the solar system. Looking into space ANSWERS

29. Looking into the unknown Notes questions from pages 112/316 & 113/317 • No questions.

30. How Science WorksANSWERS • Hypothesis – the Universe is much older than present evidence suggests. • Theory – the Big Bang theory for the creation of the Universe. • Prediction – the distance of the galaxies must be greater than calculated. • Political influence – Soviet Union after Stalin, influenced the thinking of scientists. • Importance of technology – the building of a new, much larger, more powerful and more accurate telescope.