fashion, we give up on the very idea that physics is important for our Universe! We
seek to apply laws, rules, and dynamical solutions to the phenomena we observe and
measure; that’s the key to scientifically examining and understanding the world and
Universe around us. Given that these puzzles all suffer from the same problem—a
set of initial conditions must be put in by an ad hoc method—it makes sense to
attempt to concoct a physically well-motivated explanation for these initial conditions. Ideally, whatever scenario you cook up will not only explain these puzzles, but
will make novel, additional predictions that can then be sought out and put to the test.
Historically, every new scientific idea has had to meet three criteria in order to be
universally accepted as superior to the previously prevailing idea:
• It must reproduce the full suite of successes of the prevailing theory, meaning any
replacement for the hot Big Bang with a singular beginning must successfully
give the light element abundances, the cosmic microwave background, the largescale structure of the Universe, and match the observed Hubble expansion.
• It must succeed where the prevailing theory has failed, which means it needs to
provide an explanation for these five puzzles that the Big Bang cannot provide on
its own.
• And it must make new, testable predictions for phenomena and properties that can
be measured within this Universe. These predictions must be fundamentally,
veritably, and quantifiably different from the predictions made by the alternative
theory it’s seeking to supplant.
If a scenario could be concocted that would satisfy all of those conditions,
perhaps it could either replace or augment the hot Big Bang scenario, as it was
originally formulated, to better explain the cosmic origins of our Universe.
9.4 The Inflationary Universe
By the late 1970s, many physicists and cosmologists were thinking about these
problems, with a special emphasis on the horizon and flatness problems, owing to the
robustness of the data indicating a uniform temperature and spatial flatness to the
Universe as a whole. On December 7, 1979, a young postdoc named Alan Guth
wrote the following in his notebook:
9.4.1 Spectacular Realization
This kind of supercooling can explain why the universe today is so incredibly flat—
and therefore resolve the fine-tuning paradox pointed out by Bob Dicke in his
Einstein day lectures.
9 Before the Big Bang
91
seek to apply laws, rules, and dynamical solutions to the phenomena we observe and
measure; that’s the key to scientifically examining and understanding the world and
Universe around us. Given that these puzzles all suffer from the same problem—a
set of initial conditions must be put in by an ad hoc method—it makes sense to
attempt to concoct a physically well-motivated explanation for these initial conditions. Ideally, whatever scenario you cook up will not only explain these puzzles, but
will make novel, additional predictions that can then be sought out and put to the test.
Historically, every new scientific idea has had to meet three criteria in order to be
universally accepted as superior to the previously prevailing idea:
• It must reproduce the full suite of successes of the prevailing theory, meaning any
replacement for the hot Big Bang with a singular beginning must successfully
give the light element abundances, the cosmic microwave background, the largescale structure of the Universe, and match the observed Hubble expansion.
• It must succeed where the prevailing theory has failed, which means it needs to
provide an explanation for these five puzzles that the Big Bang cannot provide on
its own.
• And it must make new, testable predictions for phenomena and properties that can
be measured within this Universe. These predictions must be fundamentally,
veritably, and quantifiably different from the predictions made by the alternative
theory it’s seeking to supplant.
If a scenario could be concocted that would satisfy all of those conditions,
perhaps it could either replace or augment the hot Big Bang scenario, as it was
originally formulated, to better explain the cosmic origins of our Universe.
9.4 The Inflationary Universe
By the late 1970s, many physicists and cosmologists were thinking about these
problems, with a special emphasis on the horizon and flatness problems, owing to the
robustness of the data indicating a uniform temperature and spatial flatness to the
Universe as a whole. On December 7, 1979, a young postdoc named Alan Guth
wrote the following in his notebook:
9.4.1 Spectacular Realization
This kind of supercooling can explain why the universe today is so incredibly flat—
and therefore resolve the fine-tuning paradox pointed out by Bob Dicke in his
Einstein day lectures.
9 Before the Big Bang
91