”„Well, that IS logical. But actually what happened during the Big Bang? What is all the scientists talking about?”¦
”„Big Bang, the process involves the creation of the world, matter, radiation and energy.”¦
The big bang was extremely hot; of that we can be fairly certain. The cosmic blackbody radiation is the testament of this fiery origin. However, to understand precisely how hot the extreme environment of the early universe was, we must explore the significance of temperature, of its counterpart, energy, and indeed, of the nature of matter itself at early epochs.
A crucial role is played by the elementary particles of nuclear physics. These particles are collectively known as hadrons. Hadrons come in many varieties, including mesons, protons, neutrons, and heavier but short-lived particles. These particles are measured not by their mass, which can become a very transient concept, but by their total rest mass energy. Rest mass energy is only fully liberated when a particle is completely annihilated.
Annihilation
is a common fate for a particle and its antiparticle”X a particle of opposite
electric charge but otherwise identical nature. The annihilation of a single
proton and antiproton yields 1 billion electron volts of energy, which is barely
enough power to run a flashlight for a billionth of a second. To make the conversion,
note that 620 billion electron volts equal 1 erg, and 10 million ergs of energy
expended for 1 second amounts to a power output of 1 watt. (The units of electron
volts are chosen for the physicist”¦s convenience, one electron volt being
equal to the energy gained by a single electron accelerated through a potential
of 1 volt.) The energy released from annihilation of one proton-antiproton pair
may not seem like a great deal of energy, until we consider a vast number of
protons and antiprotons. In fact, the efficiency of energy output per gram of
material resulting from annihilation vastly exceeds anything attainable by other
means of conversion. Annihilation is the ultimate, completely efficient energy
source. No matter remains from this conversion.
Metals begin to melt at temperatures above 1000 to 2000 degrees Kelvin (K), temperatures equivalent to energy of about one-tenth of an electron volt per atom. At the center of the sun, the temperature is 10 million degrees Kelvin, equivalent to about 1000 electron volts per atom. Ordinary chemical bonds between atoms have energies of about 1 electron volt, and the nuclear forces that bind nuclei together require energies of millions of electron volts to disrupt or to fuse the nuclei. Roughly a million times more energy is released in thermonuclear explosions than in chemical explosions, which explains why we measure the force of a nuclear explosion in megatons of TNT. Total annihilation releases more than 100 times more energy per gram of material than a nuclear explosion.
Not
only do particles annihilate and release energy, but the reverse process
may also occur: particles can be created from an intense radiation field. In
one important example of this process that is responsible for ordinary nuclei
of atoms, the resulting particles, mesons, ordinarily exist only for brief instants
in the inaccessible interiors of atomic nuclei; these particles help to hold
the nucleus together. However, in the early universe, the matter density exceeded
nuclear densities, and new states of particles may have been created.
According to modern elementary particle theories, there are a finite number of elementary particles. If this were not the case, the available energy at early times and higher densities would go into creating more and more species of particles, and the temperature would level off. In effect, at earlier times and higher energies, new types of elementary particles are soon exhausted, and the temperature increases continuously back to the Planck instant, where it attains the incredible value of 1032 degrees Kelvin. For physicists who ordinarily work with giant particle accelerators, such conditions are unattainable. The corresponding energy is 1019 GeV (billion electron volts): the largest planned terrestrial accelerators may smash particles together at energies of thousands of electron volts. The early universe offers a marvelous particle accelerator: we would need to build an array of superconducting magnets 1 light-year across to duplicate it. Although we have to take whatever is left over from this fiery past, fossil relics from near the beginning of time may be playing an important role in the universe we see today.