01:750:109 Chapter Notes - Chapter 13.3: Galaxy Formation And Evolution, Alan Guth, Atomic Nucleus
Inflation
●3 most pressing about universe:
○Where do structures like galaxies come from?
■Successful models of galaxy formation start from the assumption that gravity
could collect matter together in regions of the early universe that had slightly
enhanced density
○Why is the large-scale universe nearly uniform?
■Not exactly uniform since cosmic microwave background show that there is a
slight variation within a few parts in 100,000 but it is remarkable enough that
we would not expect it to have occurred by pure chance
○Why is the geometry of the universe flat?
■Observational efforts to measure the large-scale geometry of the universe have
not yet detected any curvature. As far as we can tell, the large-scaled geometry
of the universe is flat suggesting a precisely balanced geometry that would be
unlikely to have arisen by chance
●Process of science demands that we seek natural explanations for the natures of the universe
Did the universe undergo an early episode of inflation?
●Idea of inflation emerged when physicist Alan Guth was considering how the separation of the
strong force from the GUT force at the end of the GUT era might have affected the expansion of
the universe
●Some theories of high-energy physics predict that this separation of forced would have released
enormous amounts of energy and Guth realized that this energy could have caused the universe
to expand dramatically, perhaps by a factor of 10^30 in a time of less than 10^-36 second
●This period of rapid expansion is what scientists refer to as inflation
and it can explain the 3 key
mysteries as follows
Structure: Giant Quantum Fluctuations
●On very small scaled, the energy fields at any point in space are always fluctuating
●The distribution of energy through space is very slightly irregular, even in complete vacuum
●The tiny quantum "ripples" that make up the irregularities can be characterized by a wavelength
that corresponds roughly to their size
●In principle, quantum ripples in the very early universe could have been the seeds for density
enhancements that later grew into galaxies
●But wavelengths of original ripples were far too small to explain density enhancements like
those that left imprints on the cosmic microwave background
●Inflation would have dramatically increased the wavelengths of these quantum fluctuations
●Rapid growth of universe during prd of inflation (end of GUT) would have stretched tiny ripples
from a size smaller than that of an atomic nucleus to the size of our solar system, making them
Document Summary
Successful models of galaxy formation start from the assumption that gravity could collect matter together in regions of the early universe that had slightly enhanced density. Not exactly uniform since cosmic microwave background show that there is a slight variation within a few parts in 100,000 but it is remarkable enough that we would not expect it to have occurred by pure chance. Observational efforts to measure the large-scale geometry of the universe have not yet detected any curvature. As far as we can tell, the large-scaled geometry of the universe is flat suggesting a precisely balanced geometry that would be unlikely to have arisen by chance. Process of science demands that we seek natural explanations for the natures of the universe. Idea of inflation emerged when physicist alan guth was considering how the separation of the strong force from the gut force at the end of the gut era might have affected the expansion of the universe.
