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Astronomers Claim to Find the Most Distant Known Galaxies (Forwarded)
From: Andrew Yee
It is thought that when the universe was 300,000 years old it entered a period when no stars were shining. Cosmologists refer to this phase of cosmic history as the "Dark Ages." That's poorly worded. It seems to be saying that from the very start of the Big Bang until 300,000 years after it, there were stars shining, then they stop shining as the "Dark Ages" began. In fact there were no stars at all anytime before the "Dark Ages" nor during most or all of the "Dark Ages" themselves. (There was a period of time around the end of the "Dark Ages" when the first stars existed, and shined locally, but their UV light was absorbed and scattered by neutral hydrogen, preventing most of that energy from being seen from afar. But that's irrelevant to the definition of the *start* of the "Dark Ages".) Also, what's the most accurate current estimate of the end of the opaque big-bang fireball, when the Universe became transparent to visible light for the first time, allowing the background radiation (now redshifted to microwave) to be released, which I understand to be the correct definition of the start of the "Dark Ages"? I read 380,000 years recently, updated from 300,000 or 400,000 that I had read many years previously. Is that incorrect, it's back to 300,000? |
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