How long after the Big Bang was the Planck time, before which our current theories are completely unable to describe conditions in the universe?
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Before the Planck time
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The Planck era refers to the time period
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Why can't current theories describe what happened during the Planck era?
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We do not yet have a theory that links quantum mechanics and general relativity.
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unify the strong force and the electromagnetic and weak forces.
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A GUT (grand unified theory) refers to theories that
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Two, gravity and the GUT force.
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How many forces operated in the universe during the GUT era?
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The electromagnetic and weak forces.
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Which forces have physicists shown to be the same force under conditions of very high temperature or energy, as confirmed by experiments in particle accelerators?
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A sudden expansion of the universe after the strong force froze out from the GUT force.
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What do we mean by inflation?
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An enormous amount of energy was released when the strong force froze out from the GUT force.
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Why might inflation have occurred at the end of the GUT era?
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Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.
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What direct evidence do we have that the weak and electroweak force?
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They combined in groups to make protons, neutrons, and their antiparticles.
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What happened to the quarks that existed freely during the particle era?
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5 minutes
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Approximately how long did the era of nucleosynthesis last?
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Hydrogen and helium and trace amounts of deuterium and lithium.
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What kinds of atomic nuclei formed during the era of nucleosynthesis?
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Why is the era of nucleosynthesis so important in determining the chemical composition of the universe?
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Except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosythesis.
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The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
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Why did the era of nuclei end when the universe was about 300,000 years old?
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It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
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Which of the following statements about the cosmic background radiation is not true?
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The end of the era of nuclei.
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Where do the photons in the cosmic background radiation originate?
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The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe.
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Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum?
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The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
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Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
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The Big Bang with a small contribution from stellar nucleosynthesis.
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Helium originates from
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The cosmic background radiation and the high helium content of the universe.
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What are the two key observational facts that led to widespread acceptance of the Big Bang model?
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the "freezing out" of the strong force from the GUT force.
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What is postulated to have caused a sudden inflation of the early universe?
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Why is the sky dark at night?
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Olbers' paradox question is:
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