Tests of Big Bang Cosmology
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Tests of Big Bang Cosmology (Review)

  The Big Bang Model is supported by a number of important
  observations, each of which are described in more detail
  on separate pages:

  1. The expansion of the universe

  Edwin Hubble's 1929 observation that galaxies were generally
  receding from us provided the first clue that the Big Bang
  theory might be right.

  2. The abundance of the light elements H, He, Li

  The Big Bang theory predicts that these light elements should
  have been fused from protons and neutrons in the first few
  minutes after the Big Bang.

  3. The cosmic microwave background (CMB) radiation

  The early universe should have been very hot. The cosmic
  microwave background radiation is the remnant heat leftover
  from the Big Bang.

  These three measurable signatures strongly support the notion
  that the universe evolved from a dense, nearly featureless
  hot gas, just as the Big Bang model predicts.

WMAP's Top Ten

  1. NASA's Wilkinson Microwave Anisotropy Probe (WMAP) has
  mapped the Cosmic Microwave Background (CMB) radiation (the
  oldest light in the universe) and produced the first
  fine-resolution (0.2 degree) full-sky map of the microwave sky

  2. WMAP definitively determined the age of the universe to be
  13.73 billion years old to within 1% (0.12 billion years) -as
  recognized in the Guinness Book of World Records!

  3. WMAP nailed down the curvature of space to within 1% of
  "flat" Euclidean, improving on the precision of previous
  award-winning measurements by over an order of magnitude

  4. The CMB became the "premier baryometer" of the universe with
  WMAP's precision determination that ordinary atoms (also called
  baryons) make up only 4.6% of the universe (to within 0.1%)

  5. WMAP's complete census of the universe finds that dark
  matter (not made up of atoms) make up 23.3% (to within 1.3%)

  6. WMAP's accuracy and precision determined that dark energy
  makes up 72.1% of the universe (to within 1.5%), causing the
  expansion rate of the universe to speed up. - "Lingering doubts
  about the existence of dark energy and the composition of the
  universe dissolved when the WMAP satellite took the most
  detailed picture ever of the cosmic microwave background
  (CMB)." - Science Magazine 2003, "Breakthrough of the Year"


  7. WMAP has mapped the polarization of the microwave radiation
  over the full sky and discovered that the universe was
  reionized earlier than previously believed. - "WMAP scores on
  large-scale structure. By measuring the polarization in the CMB
  it is possible to look at the amplitude of the fluctuations of
  density in the universe that produced the first galaxies. That
  is a real breakthrough in our understanding of the origin of
  structure." - ScienceWatch: "What's Hot in Physics", Simon
  Mitton, Mar./Apr. 2008

  8. WMAP has started to sort through the possibilities of what
  transpired in the first trillionth of a trillionth of a second,
  ruling out well-known textbook models for the first time.

  9. The statistical properties of the CMB fluctuations measured
  by WMAP appear "random"; however, there are several hints of
  possible deviations from simple randomness that are still being
  assessed. Significant deviations would be a very important
  signature of new physics in the early universe.

  10. WMAP has put the "precision" in "precision cosmology" by
  reducing the allowed volume of cosmological parameters by a
  factor of 30,000. The three most highly cited physics and
  astronomy papers published in the new millennium are WMAP
  scientific papers--- reflecting WMAP's enormous impact.

Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results

  We present cosmological parameter constraints based on the
  final nine-year WMAP data, in conjunction with additional
  cosmological data sets. The WMAP data alone, and in
  combination, continue to be remarkably well fit by a
  six-parameter LCDM model. When WMAP data are combined with
  measurements of the high-l CMB anisotropy, the BAO scale, and
  the Hubble constant, the densities, Omegabh2, Omegach2, and
  Omega_L, are each determined to a precision of ~1.5%. The
  amplitude of the primordial spectrum is measured to within
  3%, and there is now evidence for a tilt in the primordial
  spectrum at the 5sigma level, confirming the first detection
  of tilt based on the five-year WMAP data. At the end of the
  WMAP mission, the nine-year data decrease the allowable
  volume of the six-dimensional LCDM parameter space by a
  factor of 68,000 relative to pre-WMAP measurements. We
  investigate a number of data combinations and show that their
  LCDM parameter fits are consistent. New limits on deviations
  from the six-parameter model are presented, for example: the
  fractional contribution of tensor modes is limited to r<0.13
  (95% CL); the spatial curvature parameter is limited to
  -0.0027 (+0.0039/-0.0038); the summed mass of neutrinos is
  <0.44 eV (95% CL); and the number of relativistic species is
  found to be 3.84+/-0.40 when the full data are analyzed. The
  joint constraint on Neff and the primordial helium abundance
  agrees with the prediction of standard Big Bang
  nucleosynthesis. We compare recent PLANCK measurements of the
  Sunyaev-Zel'dovich effect with our seven-year measurements,
  and show their mutual agreement. Our analysis of the
  polarization pattern around temperature extrema is updated.
  This confirms a fundamental prediction of the standard
  cosmological model and provides a striking illustration of
  acoustic oscillations and adiabatic initial conditions in the
  early universe.

Planck 2013 results. I. Overview of products and scientific results

  The ESA's Planck satellite, dedicated to studying the early
  universe, was launched on May 2009 and has been surveying the
  microwave and submillimetre sky since August 2009. In March
  2013, ESA and the Planck Collaboration publicly released the
  initial cosmology products based on the first 15.5 months of
  Planck operations, along with a set of scientific and
  technical papers and a web-based explanatory supplement. This
  paper describes the mission and its performance, and gives an
  overview of the processing and analysis of the data, the
  characteristics of the data, the main scientific results, and
  the science data products and papers in the release.
  Scientific results include robust support for the standard,
  six parameter LCDM model of cosmology and improved
  measurements for the parameters that define this model,
  including a highly significant deviation from scale
  invariance of the primordial power spectrum. The Planck
  values for some of these parameters and others derived from
  them are significantly different from those previously
  determined. Several large scale anomalies in the CMB
  temperature distribution detected earlier by WMAP are
  confirmed with higher confidence. Planck sets new limits on
  the number and mass of neutrinos, and has measured
  gravitational lensing of CMB anisotropies at 25 sigma. Planck
  finds no evidence for non-Gaussian statistics of the CMB
  anisotropies. There is some tension between Planck and WMAP
  results; this is evident in the power spectrum and results
  for some of the cosmology parameters. In general, Planck
  results agree well with results from the measurements of
  baryon acoustic oscillations. Because the analysis of Planck
  polarization data is not yet as mature as the analysis of
  temperature data, polarization results are not released. We
  do, however, illustrate the robust detection of the E-mode
  polarization signal around CMB hot- and cold-spots.

Big Bang Acoustics: Movie and Sound Files

Frequently Asked Questions in Cosmology