The Beginning of Nucleosynthesis
Physicists speak of many theories of strange particles produced in the high temperature and enormous pressure of the very early universe. The first particles may have been complex and heavy. Many of the strange particles were antiparticles of others. These quickly found particles of the same species and annihilated them, producing two or three gamma rays. Each annihilating pair made photons with a total energy equivalent to the mass of the pair. This contributed to the process of breaking up the original highly energetic photons into many others of lower energy. It also broke up the strange, complex, heavy particles into the more familiar, simpler, low-mass particles. Eventually the components of ordinary atoms predominated: protons, neutrons, and electrons.
At this point nucleosynthesis began. Protons and neutrons collided with each other to form the first nuclei, but they made only the three elements of greatest simplicity and lowest weight: hydrogen, helium, and lithium. The cooling put an end to particle production about the time that nucleosynthesis began. Nucleosynthesis also requires high temperatures, though not as high as those particle production requires. The protons repel each other. They must collide with sufficient speed to overcome their mutual repulsion and get close enough to each other to stick together. The cooling continued so rapidly that nucleosynthesis stopped a few minutes after the universe began.
Light usually accompanies high-energy collisions. Cycles of darkness and light let us trace the two stages of nucleosynthesis in the universe. The first stage made the nuclei of the three simplest elements, and the second stage made the heavier elements. We have gone over the first stage in this chapter, and will treat the second in another, when we come to the second time light filled the universe.
After the first stage of nucleosynthesis stopped, the cooling continued for thousands of years. Eventually the nuclei cooled enough to capture the free electrons and form atoms. At this point the light rays could travel freely. Without free charged particles like electrons and positive nuclei there was much less scattering. The cooling continued, making the light redder and redder.
On Earth the last light of day is reddish because of increasing scattering along longer and longer paths through the atmosphere. Twilight is usually cooler because the Sun’s rays strike the Earth more and more obliquely. Toward the end of the first day there was less scattering but more cooling, for different reasons.
One cycle of darkness and light made the first atoms. The process of formation started with particles. These all came from darkness. The energetic darkness of gamma rays is a cause but also the effect of a previous cause. If we want to get back to the origin of all things, we must understand something about physical forces.
At this point nucleosynthesis began. Protons and neutrons collided with each other to form the first nuclei, but they made only the three elements of greatest simplicity and lowest weight: hydrogen, helium, and lithium. The cooling put an end to particle production about the time that nucleosynthesis began. Nucleosynthesis also requires high temperatures, though not as high as those particle production requires. The protons repel each other. They must collide with sufficient speed to overcome their mutual repulsion and get close enough to each other to stick together. The cooling continued so rapidly that nucleosynthesis stopped a few minutes after the universe began.
Light usually accompanies high-energy collisions. Cycles of darkness and light let us trace the two stages of nucleosynthesis in the universe. The first stage made the nuclei of the three simplest elements, and the second stage made the heavier elements. We have gone over the first stage in this chapter, and will treat the second in another, when we come to the second time light filled the universe.
After the first stage of nucleosynthesis stopped, the cooling continued for thousands of years. Eventually the nuclei cooled enough to capture the free electrons and form atoms. At this point the light rays could travel freely. Without free charged particles like electrons and positive nuclei there was much less scattering. The cooling continued, making the light redder and redder.
On Earth the last light of day is reddish because of increasing scattering along longer and longer paths through the atmosphere. Twilight is usually cooler because the Sun’s rays strike the Earth more and more obliquely. Toward the end of the first day there was less scattering but more cooling, for different reasons.
One cycle of darkness and light made the first atoms. The process of formation started with particles. These all came from darkness. The energetic darkness of gamma rays is a cause but also the effect of a previous cause. If we want to get back to the origin of all things, we must understand something about physical forces.
