Models of Earlier Events

To model the Big Bang cosmology at earlier times than those covered in Weinberg's First Three Minutes, certain time regimes have been proposed with the types of events which would be happening at those times.

Before 1 Planck Time

Before a time classified as a Planck time, 10^-43 seconds, all of the four fundamental forces are presumed to have been unified into one force. All matter, energy, space and time are presumed to have exploded outward from the original singularity. Nothing is known of this period.

It is not that we know a great deal about later periods either, it is just that we have no real coherent models of what might happen under such conditions. The electroweak unification has been supported by the discovery of the W and Z particles, and can be used as a platform for discussion of the next step, the Grand Unification Theory (GUT). The final unification has been called a "supergrand unification theory", and becoming more popular is the designation "theory of everything" (TOE). But "theories of everything" are separated by two great leaps beyond the experiments we could ever hope to do on the Earth.

Era of 1 Planck Time

In the era around one Planck time, 10^-43 seconds, it is projected by present modeling of the fundamental forces that the gravity force begins to differentiate from the other three forces. This is the first of the spontaneous symmetry breaks which lead to the four observed types of interactions in the present universe.

Looking backward, the general idea is that back beyond 1 Planck time we can make no meaningful observations within the framework of classical gravitation. One way to approach the formulation of the Planck time is presented by Hsu. One of the characteristics of a black hole is that there is an event horizon beyond which we can obtain no information - scales smaller than that are hidden from the outside world. For a given enclosed mass, this limit is on the order of

where G is the gravitational constant and c is the speed of light. But from the uncertainty principle and the DeBroglie wavelength, we can infer that the smallest scale at which we could locate the event horizon would be the Compton wavelength.

Equating L and λ, we obtain a characteristic mass called the Planck mass:

Substituting this mass back into one of the length expressions gives the Planck length

and the light travel time across this length is called the Planck time:

Keep in mind that this is a characteristic time, so its order of magnitude is what should be noted. Sometimes it is defined with the wavelength above divided by 2π, so don't worry about the number of significant digits.

Separation of the Strong Force

At a time around 10^-36 seconds, present models project a separation of the strong force, one of the four fundamental forces. Before this time the forces other than gravity would be unified in what is called the grand unification. The spontaneous symmetry breaking which occurs in this era would distinguish as a separate interaction the force which would hold nuclei together in later eras.

In the 1970's. Sheldon Glashow and Howard Georgi proposed the grand unification of the strong, weak, and electromagnetic forces at energies above 10¹⁴ GeV. If the ordinary concept of thermal energy applied at such times, it would require a temperature of 10²⁷ K for the average particle energy to be 10¹⁴ GeV.

Though the strong force is distinct from gravity and the electroweak force in this era, the energy level is still too high for the strong force to hold protons and neutrons together, so that the universe is still a "sizzling sea of quarks".

Inflationary Period

Triggered by the symmetry breaking that separates off the strong force, models suggest an extraordinary inflationary phase in the era 10-36 seconds to 10-32 seconds. More expansion is presumed to have occurred in this instant than in the entire period ( 14 billion years?) since. The inflationary epoch may have expanded the universe by 1020 or 1030 in this incredibly brief time. The inflationary hypothesis offers a way to deal with the horizon problem and the flatness problem of cosmological models.

Lemonick and Nash in a popular article for Time describe inflation as an "amendment to the original Big Bang" as follows: "when the universe was less than a billionth of a billionth of a billionth of a second old, it briefly went through a period of superchanged expansion, ballooning from the size of a proton to the size of a grapegruit (and thus expanding at many, many times the speed of light). Then the expansion slowed to a much more stately pace. Improbable as the theory sounds, it has held up in every observation astronomers have managed to make."

Quark-antiquark Period

As the inflationary period ends, the universe consists mostly of energy in the form of photon , and those particles which exist cannot bind into larger stable particles because of the enormous energy density. They would exist as a collection of quarks and antiquarks along with their exchange particles, a state which has been described as a "sizzling sea of quarks". This time period is estimated at 10^-32 seconds to 10^-5 seconds. During this period the electromagnetic and weak forces undergo the final symmetry break, ending the electroweak unification at about 10^-12 seconds.

Quark Confinement

When the expansion of the "primordial fireball" had cooled it to 10¹³ Kelvin, a time modeled to be about 10^-6 seconds, the collision energies had dropped to about 1 GeV and quarks could finally hang onto each other to form individual protons and neutrons (and presumably other baryons.) At this time, all the kinds of particles which are a part of the present universe were in existence, even though the temperature was still much too high for the formation of nuclei. At this point we can join the standard "big bang" model as outlined by Steven Weinberg in The First Three Minutes.