A detailed account is given of a quasi-steady state cosmological model which was originally briefly described by Arp et al. We show that this model will explain the 2.73 K microwave background and the abundances of the light isotopes D, He-3, He-4, Li-6, Li-7, Be-9, and B-11. The model is based on the idea that creation takes place in little big bangs each involving about 10(16) M. distributed over all space and time, the universe itself being without a beginning. We then show that an attractive feature of this idea is that we can explain in a natural way the general outpouring of mass and energy from a wide range of extragalactic objects, ranging from protogalaxies through to high-energy events (radio galaxies and QSOs) down to small scales in the nucleus of our Galaxy. Following the introduction and discussion of earlier ideas, in sectional sign 3 we discuss the physics of creation. It is shown that unless creation of matter is included in the physical laws, the laws lack universality. Creation of matter is governed by a conservation law which operates to prevent spacetime singularities which otherwise occur in general relativity. In contrast to the classical steady state model, creation takes place only in strong gravitational fields associated with dense aggregates of already existing matter. Also unlike the classical steady state, the expansion rate H = S/S of the universe is not a constant but can vary secularly, corresponding to changes in the number and masses of the creation centers which drive the expansion. The model fits the observational facts of cosmology best when intermittent bursts of creation, occurring at intervals generally of order H-0(-1), are interspersed with longer periods of comparatively weak creation, but with the possibility that, viewed over long time intervals, the expansion is an approximately steady process with a generation length approximately H-0(-1). If such mass-creation events have slight anisotropy, they can be detected by the laser interferometric gravity wave detectors being planned now. The gravity wave background produced by them should also be detectable by the timing measurements of millisecond pulsars. Development of the theory indicates that newly created particles have a mass (3HBARc/4piG)1/2. Such Planck particles are unstable over a time scale of approximately 10(-43) s. An equipartition between radiation and matter in the decay leads to a production of approximately 5 x 10(18) baryons per Planck particle, with the square of this number, 2.5 x 10(37), the source of the large dimensionless numbers of physics and cosmology. Although most of the radiative energy goes into the kinetic energies of expansion of the particles of a Planck fireball, thereby supplying the starting point of high-energy astrophysics, the radiation field causes a decaying Planck particle to expand as a cloud of particles in which nuclear reactions take place. It is as a consequence of such reactions that the light elements are produced. Unlike the situation in big bang cosmology, beryllium and boron are synthesized as well as lithium and helium, and all with relative abundances that agree very well with solar system values (sectional sign 6). Provided that the most important creation centers have masses of order 10(16) M., agreeing with the masses of individual cells in the honeycomb structure of the observed distribution of galaxies, the random thermal energy associated with the expanding material from creation centers is in good agreement with that required to explain the genesis of the microwave background. A thermalizing agent such as metallic whiskers, with an optical depth of 10 or more at the last major creation episode, is adequate to explain the observed smoothness of the resulting background, without interfering with extragalactic astronomy at the radio and optical wave-lengths. This leads to a required present-day average intergalactic density of approximately 10(-35) g cm-3 for such particles, only a modest requirement, Although the last major creation episode occurred at a time approximately H-0(-1) ago, creation continues at the present day in the form of a cascade which passes from larger masses to smaller masses. In sectional sign 8 we discuss the likelihood that creation events can give rise to the observed properties of radio galaxies, QSOs, etc. We take as an example the properties of the well-known galaxy M87. Finally, in sectional signs 9 we give a summary of our theory and make comparisons between these new ideas and the currently favored views.
