Forces Present in Empty Space
If there are no particles present, then we say that space is empty, even if it contains electromagnetic waves and gravitational field lines. At the beginning (or very soon after it) gamma-ray photons were distributed nearly uniformly in all of space. The mass equivalent of their energy (energy divided by the square of the speed of light) produced gravity.
Since electromagnetic energy has mass and produces gravity, empty space can have energy, mass, and gravity, but nothing else. If there were any massive particles the space would not be empty. However, if the energy is distributed nearly uniformly everywhere, then its mass is also distributed nearly uniformly. In that case the average strength of gravity is low because the gravitational attraction from all directions is nearly equal. Equal attraction in opposite directions cancels itself.
If the universe started as empty space, then it did not have all four forces acting at once. The strong and weak nuclear forces could not act in the beginning when there was only pure energy. They had to wait until nucleons formed. Neutrinos did not appear until the weak nuclear force was operating. Gravity was weak or nearly absent if the electromagnetic energy was nearly uniformly distributed. Strong gravity had to wait until there were fluctuations, regions with higher density or lower density than the average density.
That is why it is reasonable to think that electromagnetic forces acted first, before there were any particles. The first energy must have had the capability of forming matter. This suggests that the first energy was electromagnetic. It took the form of very energetic gamma rays uniformly distributed at all points in the universe and directed in all directions.
Before any ray of visible light could begin to vibrate, all was dark. We don’t know how long the darkness lasted because we don’t know how long the gamma rays traveled in empty space before the first collisions. Apparently the rays collided everywhere in the universe at about the same time. After that, besides waves, there were particles in the darkness, and space was no longer empty. Once there were particles, the strong nuclear force began to act. The weak nuclear force also began to act, but it took much longer to produce its effects.
In some places more rays collided than in other places. This made fluctuations in the smooth distribution of energy and particles. The fluctuations let gravity kick in. At last all four forces were acting, but electromagnetic forces came first.
Nucleosynthesis
How were the nuclei of the elements formed? We have begun to give the answer as we know it now. During the second half of the 20th century there was a long debate over this subject. Some people thought that all the 92 elements were made in the first few minutes of the universe. Others thought they were all made in the centers of the first stars. As it turned out, neither group vanquished the other. Both were partly right.
To begin with, a variety of people put forward equilibrium theories of the formation of the elements. In these theories it was generally assumed that in the early stages of the history of the universe, when all the matter was squeezed tightly together, and was presumably at very high temperature, conditions might be ripe for producing the elements by a nuclear cooking process. Such theories suffered from the difficulty that no single set of conditions of temperature and pressure would give all of the elements with the observed relative abundances, so that it was necessary to make such theories extremely complicated, with varying sets of conditions assumed to be responsible for different regions of the periodic table of the elements.[i]
[i] Truran, J. W. and A. G. W. Cameron, Chapter 23, “Nucleosynthesis,” op. cit., p. 984.
No one has found a set of conditions that could produce all the elements from pure hydrogen or from a mixture of protons and neutrons. It took two different epochs of intense pressure, heat, and light to produce all the elements. These epochs were the mornings of day one and day two.
Since electromagnetic energy has mass and produces gravity, empty space can have energy, mass, and gravity, but nothing else. If there were any massive particles the space would not be empty. However, if the energy is distributed nearly uniformly everywhere, then its mass is also distributed nearly uniformly. In that case the average strength of gravity is low because the gravitational attraction from all directions is nearly equal. Equal attraction in opposite directions cancels itself.
If the universe started as empty space, then it did not have all four forces acting at once. The strong and weak nuclear forces could not act in the beginning when there was only pure energy. They had to wait until nucleons formed. Neutrinos did not appear until the weak nuclear force was operating. Gravity was weak or nearly absent if the electromagnetic energy was nearly uniformly distributed. Strong gravity had to wait until there were fluctuations, regions with higher density or lower density than the average density.
That is why it is reasonable to think that electromagnetic forces acted first, before there were any particles. The first energy must have had the capability of forming matter. This suggests that the first energy was electromagnetic. It took the form of very energetic gamma rays uniformly distributed at all points in the universe and directed in all directions.
Before any ray of visible light could begin to vibrate, all was dark. We don’t know how long the darkness lasted because we don’t know how long the gamma rays traveled in empty space before the first collisions. Apparently the rays collided everywhere in the universe at about the same time. After that, besides waves, there were particles in the darkness, and space was no longer empty. Once there were particles, the strong nuclear force began to act. The weak nuclear force also began to act, but it took much longer to produce its effects.
In some places more rays collided than in other places. This made fluctuations in the smooth distribution of energy and particles. The fluctuations let gravity kick in. At last all four forces were acting, but electromagnetic forces came first.
Nucleosynthesis
How were the nuclei of the elements formed? We have begun to give the answer as we know it now. During the second half of the 20th century there was a long debate over this subject. Some people thought that all the 92 elements were made in the first few minutes of the universe. Others thought they were all made in the centers of the first stars. As it turned out, neither group vanquished the other. Both were partly right.
To begin with, a variety of people put forward equilibrium theories of the formation of the elements. In these theories it was generally assumed that in the early stages of the history of the universe, when all the matter was squeezed tightly together, and was presumably at very high temperature, conditions might be ripe for producing the elements by a nuclear cooking process. Such theories suffered from the difficulty that no single set of conditions of temperature and pressure would give all of the elements with the observed relative abundances, so that it was necessary to make such theories extremely complicated, with varying sets of conditions assumed to be responsible for different regions of the periodic table of the elements.[i]
[i] Truran, J. W. and A. G. W. Cameron, Chapter 23, “Nucleosynthesis,” op. cit., p. 984.
No one has found a set of conditions that could produce all the elements from pure hydrogen or from a mixture of protons and neutrons. It took two different epochs of intense pressure, heat, and light to produce all the elements. These epochs were the mornings of day one and day two.