Cosmic Paradoxes

The following sections are included:

• Foreword

• Contents

• List of Tables

• List of Figures

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One of the most dramatic achievements of nineteenth century physics¹ was the enunciation of the principle of energy conservation. Clearly, this fundamental principle has very profound consequences in every branch of physical science…

We may begin by noting that the principle of energy conservation has not been consistently honored by some prominent physicist from very early in the twentieth century…

It is remarkable¹ that there are four and only four fundamental interactions in the universe. All stable physical entities from nuclei to galaxies are held together by a combination of the four interactions: the electromagnetic, the strong nuclear, the weak nuclear and the gravitational. Two decades ago, more or less, the Physical Review Letters published a number of papers claiming evidence for a fifth interaction, analogous to but different from the conventional gravitational interaction, which was finally discarded for lack of conclusive evidence…

Up to the beginning of the twentieth century, matter and radiation were considered as distinct entities. Matter, as making up a solid, a liquid, a gas or a plasma (a fluid of ionized atoms and electrons), was seen as altogether different from electromagnetic radiation, which spans from radio waves to X-rays and beyond. It may be noted that in a hot dense plasma, like the one making up a star, as our Sun, the electrons, which are almost two thousand times less massive than the protons or the ⁴He nuclei, occupy much more volume than the much heavier protons and alpha particles…

Olber's paradox^1,2 is the riddle of the darkness of the night sky in conflict with the presumed infinity of the universe. If there were infinite stars, in infinite galaxies, in the universe, looking in any direction from the Earth's surface the line of sight should end at the surface of a star and then the whole night sky should look bright…

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The field equations of the General Theory of Relativity^{1, 2} are in principle the right dynamical equations to describe cosmic evolution. The field equations are given in terms of the Ricci tensor R_μν (which is the contracted Riemann curvature tensor), the cosmological constant Λ (originally introduced by Einstein and finally discarded), and the stress-energy tensor T_μν for all forms of matter and energy excluding gravity. R_μν and R are determined by the metric tensor g_μν together with its first and second-order partial derivatives. The metric tensor g_μν is defined implicitly by

As we have anticipated in Chapter 1, Eq. (1.1), and discussed further in Chapter 6, Eq. (6.2), Einstein's cosmological equation is

Alan Lightman and Roberta Brawer in Origins¹ (a set of interviews with leading cosmologists giving their perspective in 1990) suggest the year 1965 — the year in which Arno Penzias and Robert Wilson reported their discovery of the cosmic background radiation (CBR)— as the starting year of scientific cosmology…

The cosmological expansion is, because its scale, the most grandiose phenomenon in nature. As we have seen, it was predicted theoretically¹ by the Russian mathematicians Alexander Alexandrovich Friedmann (1888–1925) in 1921 and, independently, by the Belgian astrophysicist and Catholic priest Georges Edouard Lemaitre (1894–1966) in 1927…

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The paradox of the accelerated expansion of the universe can be stated as follows: if, after the Big Bang, expanding matter (mainly galaxies but perhaps all other kinds of mass matter) is moving radially away from the center of gravity of the finite mass universe, in the absence of any increasing counter-gravitational force, why are not galaxies seen as slowing down under the powerful central gravitational attraction?…

The critical density is the cosmic density (mass per unit volume) at which the speed of growth of the cosmic radius (Ṙ) is exactly at escape velocity, ρ_c = 3H²/8πG, where H = Ṙ/R is Hubble's parameter. At present, the actual cosmic density in our close neighborhood ρ₀, estimated on the basis of ordinary matter, luminous matter from galaxies and cosmic dust, is only about 4.5% of the critical density. Many theorists, specially inflationary theory supporters, are clearly in favor of a ratio ρ₀/ρ_c = 1 corresponding to a flat (κ = 0) universe. This 100% of total equivalent mass would include as much as 25% dark matter (of unknown provenance) and about 70% dark energy (of even more unknown nature) associated with the cosmological constant…

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The following sections are included:

• And a contingent universe is a created universe

• References

Quantum Mechanics, invented by de Broglie, Schrödinger, Heisenberg, Born, among others, to describe the physics of atoms and nuclei, is a statistical branch of physics,¹ and, as such, not very apt to describe the physics of the universe, a singular entity, absolutely unique, in spite of the current efforts to disguise it in a “multitude”, called multiverse…

The following sections are included:

• The Big Bang

• The Sun and the solar planetary system

• The Earth–Moon system

• Life

• Man

• References

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The following sections are included:

• Appendix – Physics and the Universe: From the Sumerians to the Late-Twentieth Century

• Glossary

• Author Index

• Subject Index