At this time (that's one tenth of a billionth of a second) the weak and electromagnetic forces were unified. In other words before 10-10 second, there were only three fundamental forces operating in the universe. These were the strong, gravitational and Electroweak forces. After 10-10 second, the full complement of four fundamental forces was present.
The time 10-10 second also marks another milestone in our discussion of the evolution of the universe. The modern particle acceleration of high energy physics can just barely reproduce the incredible concentration of energy associated with that event. This mean that from this point forward it is possible to have direct experimental checks of the theories that describe the evolution of the universe.
10-5 Second: The Freezing of Elementary Particles:
Up to those point, matter in the universe has been in its most fundamental form--quarks and lepton. The remaining freezings involve the coming together of those basic particles to create the matter we see around us. At 10-5 second, (10 microseconds), the first of these events occurred, when elementary particles were found out of quarks.
Before 10-5 second, matter existed in the form of hadrons and leptons--that is, the ordinary elementary particles we see in our laboratories today. The universe composed of these particles kept expanding and cooling until nuclei and atoms formed
Three Minutes: The Freezing Nucleus:
Three minutes marks the age at which nuclei, once formed, could remain stable in the universe. Before this time, if a proton and neutron came together to form deuterium, the simplest nucleus, then the subsequent collisions of that nucleus with other particles in the universe would have been sufficient to knock the nucleus apart. Before, three minutes matter existed only in the form of elementary particles, which consisted of a sea of high-energy radiation whizzing around between all the various species of elementary particles.
At three minutes, a short burst of nucleus formation occurred, as we discussed earlier. Thus from three minutes on, the universe was littered with nuclei, which formed part of the plasma that was the material of the early universe. Remember, though, that only nuclei of the light elements--hydrogen, helium, and lithium--were made at this time.
Before One Million Years: The Freezing of Atoms
The most recent transformation occurred gradually between the time the universe was a few hundred thousand and a million years old. At this time, the background temperature of the hot, dense universe was so great that electrons could not bound to the atomic orbits to form atoms. Even if an atom formed by chance, it subsequent collisions were sufficiently violent that the atom could not stay together. Thus all of the universe matter was in the form of a plasma, a hot fluid mixtures of electrons and simple nuclei.
This freezing marks an extremely important point in the history of the universe, because it is a point a which radiation such as light was no longer locked into material of the universe. You know from experience that light can travel long distances through the atmosphere (which is made of atoms), but light cannot travel freely through plasma quickly absorbs light and other forms of radiation. Thus when atoms formed, the universe became transparent and radiation was released. It is this radiation, cooled and stretched out, that we now see as the cosmic microwave background radiation.
The formation of atoms marks an important milestone for another reason. Before this event, if clumps of matter happened to begin forming (under the influence of gravity, for example), they would absorb radiation and be blown apart. This means that there must have been a "window of opportunity" for the formation of galaxies. If galaxies are made of ordinary matter, they could not have started to come together out of the primordial gas cloud until atoms had formed, about 500,000 after the big bang. By that time however the Hubble expansion had spread matter out so thinly that the ordinary workings of the forces of gravity would not have been able to make a universe of galaxies, clusters, and superclusters. Known as the galaxy problem," this puzzle remains the great riddle that must be answered by the cosmologists.
Another way of stating this problem is to compare the clumpiness of matter in the universe to the smoothness of the cosmic background radiation. The background radiation seems to be pretty much the same no matter which way you look in the universe. The uniformity arguers that the universe had a smooth, regular beginning. How can this statement to be reconciled with the lumpy structure we see when we look at the distribution of matter?
