Big-bang theory

Hot big-bang theory of expanding universe includes an (incorrect) theory of nucleogenesis... 

The Big Bang Theory is the prevailing theory of the origin of the universe, and it is based on astronomical observations. According to this theory, about 15 billion years ago all the matter and energy in the visible universe was concentrated in a small, hot, dense region, which flew apart in a gigantic explosion. 

Big Bang Theory, as conceptuali2 d by NASA, 1992. (APAA/id V/orld Photos)... 

Indiana University, Bloomington Big Bang Theory Matter and Energy Particle Accelerators... 

In order to understand the Earth s character as a planet, it also is helpful to have an understanding of how the elements in our solar system were formed. Chapter 2 starts with the Big Bang theory and continues with how very small grains eventually came together and accreted to form the beginnings of what would eventually become the Earth and other planets, about 4.5 X 10 years ago (4.5 Gyr). The initial processes of the Earth s evolution involved heat... 

The Hot Big Bang theory of the Universe was pioneered by George Gamow, R. A. Alpher and R. C. Herman in the late 1940s and early 50s. They supposed that during the first few minutes of the (then radiation-dominated) Universe, matter was originally present in the form of neutrons and that, after some free decay, protons captured neutrons and successive captures, followed by /3-decays, built up all the elements (Alpher Herman 1950). 

The basic assertion of the Hot Big Bang theory is that, as one goes back to early times, one encounters almost unlimited high temperatures and densities. The basic evidence for this is threefold ... 

G. Gamow, R. Alpher and R. Herman develop Hot Big Bang theory and suggest all elements created by neutron captures in early Universe. W. Baade distinguishes two stellar populations. 

Baade revises Hubble s distance scale, so Big Bang theory not flawed by giving age of Universe less than that of the Earth. 

One scientific theory of the origin of the universe is the much misunderstood big bang theory. 

From the thermodynamic standpoint, the basic components of stars can be considered as photons, ions and electrons. The material particle gas (fermions) and the photon gas (bosons) react differently under compression and expansion. Put n photons and n material particles into a box. Let R be the size of the box (i.e. a characteristic dimension or scale factor). The relation between temperature and size is TR = constant for the photons and TR = constant for the particles. This difference of behaviour is very important in the Big Bang theory, for these equations show quite unmistakably that matter cools more quickly than radiation under the effects of expansion. Hence, a universe whose energy density is dominated by radiation cannot remain this way for long, in fact, no longer than 1 million years. 

In recent times, several cosmological models have flourished, including one of great renown, known as the Big Bang theory. This is a simple theory with considerable predictive power. The Big Bang is the exceptionally hot and dense state considered to initiate cosmology as we know it today. It explains why stars are invariably made of hydrogen... 

The theoretical edifice of the Big Bang theory rests upon three observations ... 

The theory of inflation is an attempt to extend the Big Bang theory back as close as possible to zero time. The main hypothesis is a period of ultra-rapid expansion during the first fraction of a second. This expansion of space is induced by a negative pressure. With a change in the sign of the pressure, the world is turned upside down ... 

According to the "big-bang" theory, the universe began expanding about 12 billion years ago when an incredibly dense (1096 g-cm-3), incredibly hot (1032 K) ball containing all the matter in the universe exploded. No particles more massive than protons or neutrons existed until about 100 s after the big bang. By then, the temperature had dropped to about 109 K, low enough to permit the protons and neutrons to combine to form helium nuclei. 

Nonetheless, despite its religious implications, the Big Bang was a scientific theory that flowed naturally from observational data, not from holy writings or transcendental visions. Most physicists adopted the Big Bang theory and set their research programs accordingly. A few, like Einstein before them, didn t like the extra-scientific implications of the theory and labored to develop alternatives. 

---