Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Big Bang Theory Foundations

In courses (2)

PHYS-427: Relativity and cosmology I

Introduce the students to general relativity and its classical tests. ...

PHYS-428: Relativity and cosmology II

This course is the basic introduction to modern cosmology. It introduces students to the main concepts and formalism of cosmology, the observational status of Hot Big Bang theory and discusses major physical processes in the early Universe. ...

Description

This lecture covers the foundations of the Big Bang Theory, discussing the expansion of the universe, thermal equilibrium, temperature, conserved numbers, radiation-dominated stage, relativistic degrees of freedom, and the Friedmann equation. It also explores the prediction of the Cosmic Microwave Background (CMB) and the achievement of thermal equilibrium in an expanding universe.

Instructor

Victor Gorbenko

Official source

Ontological neighbourhood

Astronomy

Astrophysics: Physical cosmology

Related concepts (30)

Universe

The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. According to this theory, space and time emerged together 13.787billion years ago, and the universe has been expanding ever since the Big Bang. While the spatial size of the entire universe is unknown, it is possible to measure the size of the observable universe, which is approximately 93 billion light-years in diameter at the present day.

Expansion of the universe

The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion; the universe does not expand "into" anything and does not require space to exist "outside" it. To any observer in the universe, it appears that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer, on average.

Cosmic microwave background

The cosmic microwave background (CMB, CMBR) is microwave radiation that fills all space in the observable universe. It is a remnant that provides an important source of data on the primordial universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost uniform and is not associated with any star, galaxy, or other object.

Future of an expanding universe

Observations suggest that the expansion of the universe will continue forever. The prevailing theory is that the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario once popularly called "Heat Death" is now known as the "Big Chill" or "Big Freeze". If dark energy—represented by the cosmological constant, a constant energy density filling space homogeneously, or scalar fields, such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space—accelerates the expansion of the universe, then the space between clusters of galaxies will grow at an increasing rate.

Big Bang

The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the earliest known periods through its subsequent large-scale form. These models offer a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.

Related lectures (31)

Inflation and Cosmology

Explores inflation, quantum fluctuations, scalar fields, and their impact on the universe's structure formation.

Relativity and Cosmology II: Hubble Law and Universe Curvature

Covers the Hubble law derivation and cosmological parameter determination from supernova observations.

Neutrino Decoupling in Early Universe

Explores neutrino decoupling in the early universe and its implications on cosmic evolution.

Cosmic Magnetic Fields: Generation and Backreaction

Covers the generation of primordial magnetic fields and their backreaction effects in cosmology.

Nucleosynthesis and Neutrino Decoupling