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the density of matter in the early universe. They have been frozen in time as
the universe transitioned from a plasma to a transparent gas of atoms during
the Recombination Era, 380,000 years after the Big Bang.
An analysis of the Cosmic Microwave Background, similar to the
frequency analysis that is routinely performed to determine the harmonic
structure of ordinary sound waves in air, reveals the fluctuations present at the
time of the Recombination Era. (See Appendix 11.1 for more details of this
procedure.) The measurements of the CMB shown in Fig. 10.9 were undertaken by the Wilkinson Microwave Anisotropy Probe (WMAP), launched by
NASA in June, 2001, and operating until 2010. The Planck space observatory, operated by the European Space Agency from 2009 to 2013, improved
on the observations made with WMAP. The results obtained from the Planck
observatory show that the universe is topologically flat at large scales to within
0.5%. This is an impressive but somewhat strange result that warrants further
explanation.
11.6 Dark Energy and the Concordance Model
of the Universe
To achieve such a flat universe requires a very precise and critical
matter/energy density. This fine tuning is disturbing because it is surprising
that any physical quantity would assume a critical value, such that the
smallest change will induce the universe either to collapse, or to expand
forever at a finite expansion rate. However, throughout the universe there
are a substantial number of quantities with values which, if modified even
slightly, would change the nature of the universe such that life as we know it
would not be possible.
An example is the strength of the strong nuclear interaction. A slight
increase (2%) in the strength of this force would have enabled all the
hydrogen in the early universe to bind into diprotons, rather than deuterium.
(A diproton is a nucleus comprised of two protons, whereas deuterium is a
nucleus formed from a proton and a neutron.) This would have drastically
altered the physics of stars, where the elements essential to life are forged. One
might say that unless these quantities had been adjusted such that human life
is possible, we would not be here to observe and measure them. As we have
seen earlier in the present Chapter, this concept is known as The Anthropic
Principle.
Putting these philosophical speculations aside for the moment, the
problem remains that visible matter accounts for only an estimated 5% of the
R. Barrett and P. P. Delsanto
the density of matter in the early universe. They have been frozen in time as
the universe transitioned from a plasma to a transparent gas of atoms during
the Recombination Era, 380,000 years after the Big Bang.
An analysis of the Cosmic Microwave Background, similar to the
frequency analysis that is routinely performed to determine the harmonic
structure of ordinary sound waves in air, reveals the fluctuations present at the
time of the Recombination Era. (See Appendix 11.1 for more details of this
procedure.) The measurements of the CMB shown in Fig. 10.9 were undertaken by the Wilkinson Microwave Anisotropy Probe (WMAP), launched by
NASA in June, 2001, and operating until 2010. The Planck space observatory, operated by the European Space Agency from 2009 to 2013, improved
on the observations made with WMAP. The results obtained from the Planck
observatory show that the universe is topologically flat at large scales to within
0.5%. This is an impressive but somewhat strange result that warrants further
explanation.
11.6 Dark Energy and the Concordance Model
of the Universe
To achieve such a flat universe requires a very precise and critical
matter/energy density. This fine tuning is disturbing because it is surprising
that any physical quantity would assume a critical value, such that the
smallest change will induce the universe either to collapse, or to expand
forever at a finite expansion rate. However, throughout the universe there
are a substantial number of quantities with values which, if modified even
slightly, would change the nature of the universe such that life as we know it
would not be possible.
An example is the strength of the strong nuclear interaction. A slight
increase (2%) in the strength of this force would have enabled all the
hydrogen in the early universe to bind into diprotons, rather than deuterium.
(A diproton is a nucleus comprised of two protons, whereas deuterium is a
nucleus formed from a proton and a neutron.) This would have drastically
altered the physics of stars, where the elements essential to life are forged. One
might say that unless these quantities had been adjusted such that human life
is possible, we would not be here to observe and measure them. As we have
seen earlier in the present Chapter, this concept is known as The Anthropic
Principle.
Putting these philosophical speculations aside for the moment, the
problem remains that visible matter accounts for only an estimated 5% of the