773972
Descrição
FlashCards por freedomtaker98, atualizado more than 1 year ago
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Criado por freedomtaker98
aproximadamente 10 anos atrás
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| Questão | Responda |
| The Origins of the Universe | The Universe seems to be expanding; all of its galaxies appear to be moving away from each other. There are a few pieces of evidence for this: |
| 1) Light from other galaxies is Red-Shifted | Different elements absorb different frequencies of light, and each one leaves a pattern of dark lines at the frequencies where light is absorbed. When we look at light from distant galaxies, we see the same patterns but at slightly lower frequencies than normal- they have shifted to red end of the spectrum. This is called Red-Shift and is part of the Doppler Effect. |
| An example of Red-Shift | |
| The Doppler Effect is the perceived change in frequency and wavelength of a wave [I actually knew that :)] | This means that when something that emits waves moves towards or away from you, the wavelength and frequency *seem* different compared to when the source of the wave is stationary. When the wave is moving away the frequency will seem lower and its wavelength shorter- and vice versa. This happens with longitudinal waves (sound) and transverse waves (light, microwaves). |
| An example of the Doppler Effect | |
| 2) The further away a galaxy is, the greater its Red-Shift | Measurements of red-shift in faraway galaxies suggest that all the galaxies are moving away from us very quickly, in every direction you look in. More distant galaxies have great red-shifts than nearer ones, meaning they are moving away faster than nearer ones, providing evidence that the whole Universe is expanding. |
| The Big Bang Theory | As galaxies are moving away from us and the Universe seems to be expanding, something must have set both of these things going. Most likely a big explosion- the Big Bang. |
| According to the Big Bang Theory, all the matter and energy in the universe must have been massively compressed into one tiny space, before exploding from the single point and expanding. | This expansion is still going on today. Based on the current rate of expansion, the universe is estimated to be about 14 billion years old. Other theories for the beginning of the universe exist too, however. |
| The Steady State theory suggests that the universe has always existed as it does now and always will do, based on the idea that the universe appears basically identical everywhere. | The theory explains the apparent expansion of the universe by suggesting that matter is created in the spaces as the universe expands. There is a rather large problem with this theory however. |
| The discovery of Cosmic Microwave Background Radiation (CMBR) is strong evidence that the Big Bang theory is the more likely theory. | CMBR is a low frequency electromagnetic radiation that has been detected as coming from all parts of the universe. This radiation is largely in the microwave part of the electromagnetic spectrum. The Big Bang Theory is the only theory that can explain CMBR. Just after the Big Bang, while the universe was still extremely hot, everything in the universe emitted very high frequency radiation. As the universe expanded and cooled, this radiation has dropped in frequency and is now seen as microwave radiation. |
| While the Big Bang Theory is generally agreed upon as how the universe began, it does have limitations. | For example, there are some aspects of the universe that the theory cannot explain; the theory predicts that the universe's expansion should be slowing down, but it in fact appears to be speeding up. It also doesn't explain what caused the explosion, or the conditions were like before the explosion, or even if there was a 'before the explosion'. It is more likely that the theory will be adapted to account for these weaknesses than forgotten, however, as it explains so much so well that it would be hard for scientists to completely drop it. |
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