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| Pregunta | Respuesta |
| P2h - The Big Bang | . |
| The expanding Universe | Scientists have used their observations to develop a theory called the Big Bang. The theory states that about 13.7 billion years ago all the matter in the Universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion, and it is still expanding today. |
| Evidence | Evidence for the Big Bang includes: - all the galaxies are moving away from us - the further away a galaxy is, the faster it is moving away. |
| Red-shift | You may have noticed that when an ambulance or police car goes past, its siren is high-pitched as it comes towards you, then becomes low-pitched as it goes away. This effect, where there is a change in frequency and wavelength, is called the Doppler effect. |
| Continue... | This happens with light, too, and is called 'red-shift'. Our Sun contains helium. We know this because there are black lines in the spectrum of the light from the Sun where helium has absorbed light. These lines form the absorption spectrum for helium. |
| REDSHIFT | USE TEXT BOOK AND BBC BITESIZE TO REVISE REDSHIFT |
| A stars life | The swirling cloud of gas and dust is a nebula. Nebula clouds are pulled together by gravity, and as the spinning balls of gas start to get hot, it glows. This protostar cannot be seen because of the dust clouds. Gravity causes the star to become smaller, hotter and brighter. After millions of years, the core temperature is hot enough for nuclear fusion to take place. As hydrogen nuclei join together to form helium nuclei, energy is released and the star continues to shine while there is enough hydrogen. |
| Stars (continue) | Small stars shine for longer than large stars even though they have less hydrogen. They use it up at a slower rate and what happens at the end of a stars life depends on its size. |
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