Q13 – Flashcards
Unlock all answers in this set
Unlock answersquestion
To date, physicists have investigated the behavior of matter and energy at temperatures as high as those that existed in the universe as far back as ________ after the Big Bang.
answer
10 to power of ((-10)) second
question
Why can't current theories describe what happened during the Planck era?
answer
We do not yet have a theory that links quantum mechanics and general relativity.
question
What do we mean by inflation?
answer
a sudden expansion of the universe after the strong force froze out from the GUT force
question
What direct evidence do we have that the weak and electromagnetic forces were once unified as a single electroweak force?
answer
Particle accelerators on Earth can reach energies equivalent to the high temperatures of this
era and have produced particles predicted by the electroweak theory.
question
Why is the era of nucleosynthesis so important in determining the chemical composition of the universe?
answer
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 nucleosynthesis.
question
Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations. Four of the five statements below are real. Which one is fictitious?
answer
The cosmic background radiation is expected to contain spectral lines of hydrogen and helium,
and it does.
question
Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum?
answer
The background radiation came from the heat of the universe, with a peak corresponding to the
temperature of the universe.
question
What are the two key observational facts that led to widespread acceptance of the Big Bang model?
answer
the cosmic background radiation and the high helium content of the universe
question
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
answer
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
question
Why might inflation have occurred at the end of the GUT era?
answer
An enormous amount of energy was released when the strong force froze out from the GUT force.
question
Why did the era of nuclei end when the universe was about 300,000 years old?
answer
The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
question
Why do we think tiny quantum ripples should have been present in the very early universe?
answer
Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.
