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5 Cosmology and Fundamental Physics
Pages 47-57

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From page 47...
... In summarizing the main areas relevant to space astronomy and astrophysics, this chapter focuses on the following themes: · Origin and evolution of the universe; · Contents of the universe; and · New astrophysical windows and cosmic mysteries. ORIGIN AND EVOLUTION OF THE UNIVERSE According to the big bang model, the universe began as a hot, formless sea of quarks and other fundamental particles of nature.
From page 48...
... Further evidence for an explosive beginning to the universe comes from the abundances of the light elements D, 3He, 4He, and 7Li. According to the hot big bang model these elements were produced by nuclear reactions when the universe was only a few seconds old.
From page 49...
... · What is the origin of the cosmic microwave background radiation? Were there other big bangs?
From page 50...
... The Keck telescope has provided a measurement of the temperature of the universe at a much earlier time, confirming a fundamental aspect of the big bang model that the temperature of the universe decreases as it expands and is providing the means to measure the abundance of deuterium in very old hydrogen clouds to compare with predictions of the big bang model. Future Directions for Understanding the Origin and Evolution of the Universe Cosmologists anticipate major advances in their understanding of the origin and evolution of the universe.
From page 51...
... 4. Searching for deviations from a blackbody cosmic microwave background radiation spectrum at radio wavelengths.
From page 52...
... Other Constituents The photons of the CMBR remained unknown until 1964. Possible other undiscovered constituents include superheavy magnetic rnonopoles, cosmic strings, and the tiny, exploding primordial black holes predicted by Stephen Hawking.
From page 53...
... The x-ray observations of clusters, which probe the amplitude of mass fluctuations, have been an important complement to galaxy redshift surveys, which probe the amplitude of the fluctuations in galaxy numbers. The most accurate determination of the abundance of ordinary matter, between 1% and 10% of the critical density, comes from measuring the cosmic abundance of D, 3He, 4He, and Li, the light elements synthesized a few seconds after the big bang.
From page 54...
... Possible explanations of the mysterious objects range from coalescing neutron stars and black holes at cosmological distances, to magnetic flares on the surfaces of neutron stars in large galactic halos.
From page 55...
... Recent Developments in Understanding New Windows and Cosmic Mysteries The construction of a network of ground-based, kilometer-scale, laser-interferometric gravitational wave observatories in the United States and Europe (the LIGO and VIRGO projects, respectively began in the past decade with the first observations planned for 2000-2001. These instruments will be most sensitive to gravita tional waves in the 10- to 500-Hz band and will be capable of detecting the final orbital decay and coalescence of binary systems containing neutron stars or black holes at cosmological distances.
From page 56...
... In the frequency band between 10 - and 10-i Hz, known or predicted sources of gravitational waves include binary systems of normal stars, white dwarfs or neutron stars in the Milky Way, formation or coalescence of massive black holes in galactic nuclei, and a cosmological background of waves. Observation of massive black hole mergers offers the opportunity to map the space-time structure in the vicinity of a black hole and thereby to test general relativity in a strong-field regime.
From page 57...
... Many types of measurements can contribute to resolution of the questions concerning dark matter. Among these are mapping of the anisotropy of the cosmic microwave background radiation, study of gravitational tensing by objects ranging from MACHOs to distant galaxy clusters, measurement of the hot, x-ray-emitting gas in galaxy clusters, precise measurement of the primordial abundances of the light elements, and a direct search for new species of particles.


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