What is the Inflation Theory?
The Inflation Theory proposes a period of extremely rapid (exponential)
expansion of the universe shortly after the Big Bang.
Limitations of the Big Bang Theory
While the Big Bang theory successfully explains the shape
of the cosmic microwave background spectrum and the
origin of the light elements, it leaves open a number of important
questions:
- Why is the universe so uniform on the largest length scales?
- Why is the physical scale of the universe so much larger than the
fundamental scale of gravity, the Planck length, which is
one billionth of one trillionth of the size of an atomic nucleus?
- Why are there so many photons in the universe?
- What physical process produced the initial
fluctuations in the density of matter?
The Inflation Theory
The Inflation Theory, developed by Alan Guth, Andrei Linde, and Paul
Steinhardt, offers answers to these questions and several other open questions
in cosmology. It proposes a period of extremely rapid (exponential) expansion
of the universe shortly after the Big Bang, during which time the energy
density of the universe was dominated by a cosmological
constant term that later decayed to produce the matter and radiation that
fill the universe today. The Inflation Theory links important ideas in
modern physics, such as symmetry breaking and phase transitions, to cosmology.
Predictions of the Inflation Theory
In its simplest form, the Inflation Theory makes a number of important
predictions:
- That the density of the universe is close to the critical density, and
thus the geometry of the universe is flat.
- That the fluctuations in the primordial density
in the early universe had the same amplitude on all physical scales.
- That there should be, on average, equal numbers of hot and cold spots in
the fluctuations of the cosmic microwave background temperature.
MAP will be able to test these predictions.
Further Reading:
- Guth, A.L. & Steinhardt, P.J., "The Inflationary Universe",
Scientific American, May 1984.
Back to the Introduction to Cosmology Page
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Last updated: March 29, 1996
