Big Bang Model and Temperature Revision Notes

In these revision notes for Big Bang Model and Temperature, we cover the following key points:

• What were the thermodynamic parameters at the beginning of the Universes existence?
• How temperature is related to energy in various stages of the development of the Universe?
• Which are the elementary particles of matter in various temperatures?
• How the unification of forces occurs in various temperatures?
• What attempts are done to unify all forces in nature?
• What is Planck's Energy?
• What is the cosmic chords model?

Big Bang Model and Temperature Revision Notes

The Big Bang model describes the development of the Universe,starting from the instants immediately after the explosion has occurred and events upto the present day. It also introduces possible versions about the future of this giant structure of celestial bodies. It explains the developmental stages of the universe in a chronological order and also tells us about various phenomena and events that occurred at different stages of its history.

Temperature represents one of the parameters (the other is energy) used to describe various stages of the Universe development, as different stages have had different temperatures (and energies). The energy exchanged between colliding particles is of the same order as their average kinetic energy, that is

Galaxies are considered as the elementary particles of Cosmology. At different temperatures, elementary particles (microscopic ones) behave differently. At low, normal and not very high temperatures, electromagnetic interaction prevails over the other types of interaction. Matter in an oven reaches a temperature of T = 10⁵ K (E ≈ 10 eV). The energy is sufficient to break the atomic bonds. Electrons are detached from nuclei and the oven at this point contains material in a fourth state of matter known as "plasma". It contains a mixture of positive electric charges (protons and oxygen nuclei) and negative ones (electrons).

The stages with low and moderately high temperatures are characterized by electromagnetic interaction. With the increase in temperature (at higher temperatures than 10⁴ K), the weak and strong interaction forces start to appear in the process. With the further increase in temperature, they become more and more relevant in the interaction processes between elementary particles. On the other hand, despite gravitational interaction is always present in massive particles, it becomes less influential in high temperatures.

The electroweak interaction is a process that represents the unification of two of the four fundamental forces in nature: electromagnetic and weak. It occurs at temperatures higher than 10₁₅ K. This value corresponds to the energy E = 100 GeV.

The electro-strong (electroweak strong) interaction represents a still unconfirmed model that potentially would include there out of four fundamental interactions (electromagnetic, weak and strong) occurring in the universe. When temperature reaches a value of 10²⁹ K, there is a break in symmetry similar to the case of electroweak interaction. This makes that the electro-strong interaction manifest different properties to the electroweak one.

Several attempts have been made to integrate the gravitational interaction in this list and thereby obtain a single theory consisting in the unification of all four types of interaction. To achieve this compliance, the two constants (gravitational and electromagnetic) must have the same nature (and possibly be equal). This can be achieved for values of energy E_p ≈ 10¹⁹ GeV (T = 10³² K), where E_p is known as Planck's Energy. When Universe has had such a high temperature, its dimensions have been very small. It is not possible to study it through traditional methods but only through a special quantum theory of gravitation. Scientists believe the elementary particles at this stage of the Universe have had a ring shape of microscopic dimensions (about 10^-35 m). Scientist call them "cosmic chords".