Energy and our Universe - Pearson Schools

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64 2.14 Understanding our universe – how did it all happen? In this section: BTEC’s own resources Key terms P10 M5 M6 D5 D6 Red shift – light from stars that are travelling away from us comes from closer to the red end of the electromagnetic spectrum than light from the Sun. Big Bang theory – the theory that the Universe began with an explosion. Cosmic background radiation – electromagnetic energy that comes from all directions in space and is predicted to have come from the Big Bang. Our Milky Way galaxy: its shape is a spiral and the Sun is near the edge, as shown in this representation. Our Universe The Universe is made up of many different objects. So far we have looked at our Solar System, but our Sun is not the only star in the region. It is one of about 100 billion stars in our galaxy, which is called the Milky Way. The Milky Way is a spinning spiral disc. On a clear dark night without any pollution or street lights, you can see it as a ‘milkyish’ light band. Our Solar System is on the edge of the Milky Way. It takes about 220 million years for our Solar System to orbit the Milky Way, even though it is estimated to be travelling at 100 000 miles per hour. This means that it has just completed one orbit since the fi rst creatures appeared on Earth. Our galaxy is the second largest in a group of seventeen galaxies. The nearest galaxy to the Milky Way is called M31, the Andromeda galaxy. Beyond this are other clusters of galaxies, with their own stars and planets. These clusters form a shape which is a little like a honeycomb. All these clusters make up what we call the Universe. Astronomers believe that there are about 100 billion galaxies in the Universe. Activity A What is the name of our galaxy? Name one other galaxy.
Expansion of the Universe Many astrophysicists believe that the Universe is expanding. You can imagine this as bread with raisins in it rising: the raisins represent the galaxies, moving away from each other as the bread rises. Light coming from galaxies has provided evidence for this expansion. Light forms a spectrum of wavelength and frequency. The visible part of the spectrum starts with violet and ends with red. The further you go towards red, the longer the wavelength. Astrophysicists have found that light coming from distant galaxies is shifted towards the red end of the spectrum. The more distant the galaxy, the bigger the shift is. They call this a red shift. (It is also known as the Doppler effect.) A possible explanation for this red shift is that the galaxies are moving away from us. This suggests that the Universe is expanding. Unit 2: The electromagnetic spectrum is described on pages 50–51. The Big Bang theory According to the Big Bang theory, galaxies and indeed the Universe were once a fixed point that then exploded. The theory also suggests that radiation was given off during this explosion, and that this radiation should still be detected today. This radiation is called cosmic background radiation and it was detected in the 1960s. NASA confirmed this discovery in 1992, using its newly built satellite called Cosmic Background Explorer (COBE). So what next for the Universe? Cosmologists believe that the Universe could follow one of the following paths. It could continue to expand for ever. The expansion will slow down, but won’t quite stop. The expansion could come to a complete stop, forming a massive black hole (singularity). Unit 18: See page xxx for more information about black holes. Assessment activity 2.14 P10 M5 M6 D5 You are being interviewed for a job at a space technology company. You must produce a presentation on space. In your presentation: 1 List the evidence that suggests that the Universe is changing. P10 2 Describe the evidence that indicates that the Universe is changing. M6 3 Describe the strengths and weaknesses of this evidence. D6 4 Describe the Big Bang theory of how the Universe was formed M5 ; how sure are you that this theory is correct? D5 D6 Unit 2 Energy and our Universe Did you know? In the centre of our galaxy (the Milky Way) there is a black hole that is 4 million times bigger than our Sun. Activity B What does the Doppler effect tell us about our Universe? Grading tip To obtain P10 , make sure you include the red shift and the COBE as evidence that the universe is expanding. In attempting M6, remember that you need to describe how the evidence you identified for P10 suggests a changing universe. For D6 you need to discuss the evidence for and against stating that the universe is changing. 65
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Energy and our Universe - Pearson Schools

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