What Was the Universe Like Before Stars Existed? Today, the universe is filled with stars and galaxies. But there was a long period in cosmic history when none of them existed. About 380,000 years after the beginning of the universe’s expansion, the universe had cooled enough for electrons to combine with atomic nuclei, forming […]
What Was the Universe Like Before Stars Existed? Read Post »
If the early universe was unimaginably hot, how did the first atoms form? The answer begins with an important distinction: the universe did not start out filled with ordinary atoms. According to the modern Big Bang model, the universe has been expanding and cooling for about 13.8 billion years. In its early, hot state, matter
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Cosmic Inflation: How the Early Universe Expanded in a Fraction of a Second A second after the Big Bang, the universe was already expanding, cooling, and filled with an extremely hot mixture of particles and radiation. But if we move further back into cosmic history, we encounter an even more extreme possibility: cosmic inflation. Inflation
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What Happened One Second After the Big Bang? Inside the Newborn Universe One second seems almost meaningless on a human timescale. But one second after the Big Bang, the universe was already undergoing enormous physical changes. It was expanding and cooling from an extraordinarily hot, dense state. The temperature was around 10 billion kelvin, or
What Happened One Second After the Big Bang? Inside the Newborn Universe Read Post »
From Nothing to Everything? Understanding the Origin of the Universe How did everything we can see—galaxies, stars, planets and eventually life—come to exist? That question takes us to the origin of the universe, but answering it requires an important distinction. Scientists can describe a great deal about how the early universe evolved from an extremely
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What Happened Before the Big Bang? Exploring One of Science’s Biggest Questions If the universe had a beginning, what existed before it? It sounds like a simple question, but answering it is surprisingly difficult. When we ask what happened before the Big Bang, we are not simply asking what filled an empty space. We are
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