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Thorslog
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Why does inflation mean that the universe was much smaller at 380000 years after the big bang than we would predict from the Big Bang model alone? What would we expect the two sizes to be?
Well, I don't know about predicting a different size, but a universe that has an early period of inflation definitely takes longer to expand from the same seed size to the same late-time size. Not much longer, but some.Thorslog said:Why does inflation mean that the universe was much smaller at 380000 years after the big bang than we would predict from the Big Bang model alone? What would we expect the two sizes to be?
Thorslog said:Really what puzzled me was a sentence in one of Marcus Chown's books where he says that if inflation did occur then 380000 years after the Big Bang the universe would have been far smaller than if we assume expansion alone (with no inflation). I'm still not really sure what he means here.
That's not right. Inflation refers to a very specific kind of expansion, namely one that is exponential (accelerating), that occurred early on the history of the universe (prior to BBN and CMB.)mathman said:Inflation simply means the universe is expanding as a function of time. Go backwards in time and it gets smaller.
Inflation is a period of rapid expansion in the early universe, which is thought to have occurred about 10^-36 seconds after the Big Bang. It is believed to be caused by a hypothetical field called the inflaton field, which is responsible for the rapid expansion of space.
During inflation, the universe expanded exponentially, causing the space between particles to increase at a faster rate than the speed of light. This rapid expansion stretched out the fabric of space, making it less dense and causing the universe to become larger. However, once inflation ended, the universe began to cool and the inflaton field decayed, causing the expansion to slow down. This eventually led to the formation of matter and the universe becoming smaller and denser.
The 380000 year mark is significant because it marks the end of the period known as the "dark ages" of the universe. This is when the universe became transparent, allowing light to travel freely for the first time. The light from this period, known as the cosmic microwave background radiation, is what we can observe today and provides evidence for the Big Bang theory.
Inflation is thought to have smoothed out irregularities in the early universe, creating a more uniform distribution of matter and energy. This is supported by observations of the cosmic microwave background radiation, which shows a nearly uniform temperature across the universe. Inflation also provides a mechanism for the formation of galaxies and other large-scale structures in the universe.
While inflation is still a theoretical concept, there is strong evidence to support its existence. As mentioned before, the cosmic microwave background radiation provides one of the strongest pieces of evidence. Additionally, observations of the large-scale structure of the universe and the distribution of galaxies also support the predictions of inflation theory. However, more research and observations are needed to fully understand and confirm the role of inflation in the early universe.