34.1 Cosmology and Particle Physics
2 min read•june 18, 2024
The universe is constantly expanding, with galaxies moving away from each other at increasing speeds. quantifies this relationship, while general relativity provides the framework for understanding cosmic expansion on a large scale.
The theory proposes the universe began as a singularity 13.8 billion years ago. Evidence supporting this includes the observed expansion, radiation, and the abundance of light elements in the universe.
The Expanding Universe and the Big Bang
Expansion of the universe
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- Universe constantly expanding, galaxies moving away from each other at increasing speeds
- More distant galaxies appear to be moving away faster than closer ones (Andromeda, Milky Way)
- Hubble's law quantifies relationship between galaxy distance and recessional velocity
- , represents recessional velocity, , distance to galaxy
- estimated at 70 km/s/Mpc (kilometers per second per megaparsec), measures current expansion rate of universe
- General relativity provides the framework for understanding the expansion of the universe on a large scale
Big Bang theory evidence
- Big Bang theory proposes universe began as singularity 13.8 billion years ago, has been expanding since then
- Early universe extremely hot and dense, cooled as it expanded allowing matter to form (hydrogen, helium)
- Evidence supporting Big Bang theory:
- Hubble's law and observed expansion of universe (, distant galaxies)
- (CMB) radiation
- CMB leftover heat from early stages of universe, cooled to 2.7 Kelvin due to expansion
- CMB nearly uniform in all directions, supports idea of rapidly expanding early universe
- Abundance of light elements (hydrogen, helium, lithium) matches predictions from
- theory explains the rapid expansion of the early universe, addressing certain cosmological problems
Matter, Antimatter, and the Universe
Matter vs antimatter asymmetry
- Matter and opposite forms of particles with same mass but opposite charges and properties
- Electron has negative charge, positron ( counterpart) has positive charge
- Matter and antimatter particles colliding annihilate each other, converting mass into pure energy ()
- Big Bang theory predicts equal amounts of matter and antimatter created in early universe
- Observations show universe dominated by matter, very little antimatter present (stars, galaxies)
- Observed asymmetry between matter and antimatter known as problem
- Scientists propose slight excess of matter over antimatter in early universe, allowing some matter to survive annihilation
- Exact cause of asymmetry still unknown, active area of research in particle physics and cosmology (, )
Modern Cosmology and Particle Physics
- The of particle physics describes fundamental particles and their interactions
- provides the mathematical framework for understanding particle interactions
- and are hypothesized components of the universe that explain gravitational effects and accelerating expansion
- is a theoretical extension of the Standard Model that predicts additional particles
Key Terms to Review (26)
Antimatter: Antimatter consists of particles that are counterparts to the particles of ordinary matter, but with opposite charge and quantum properties. When antimatter meets matter, they annihilate each other, releasing energy.
Antimatter: Antimatter is the opposite of ordinary matter. It is composed of subatomic particles that have the same mass as their matter counterparts but the opposite electric charge. When matter and antimatter come into contact, they annihilate each other, releasing a burst of energy in the form of high-energy photons or other particles.
Baryon Asymmetry: Baryon asymmetry refers to the observed imbalance between the number of baryons (protons and neutrons) and antibaryons in the observable universe. This phenomenon is a crucial aspect of cosmology and particle physics, as it helps explain the dominance of matter over antimatter in the universe we inhabit.
Big Bang: The Big Bang is the prevailing cosmological model that describes the early development and expansion of the universe from an initial state of extremely high density and temperature. It is the foundational theory in the field of cosmology, providing a comprehensive explanation for the origin and evolution of the observable universe.
Big Bang Nucleosynthesis: Big Bang nucleosynthesis is the process that occurred in the early universe, shortly after the Big Bang, where the lightest atomic nuclei were formed from the primordial plasma of protons and neutrons. This process is a key piece of evidence supporting the Big Bang theory of cosmology and is closely tied to the fields of particle physics and astrophysics.
Cosmic microwave background: The cosmic microwave background (CMB) is the thermal radiation left over from the Big Bang, filling the universe almost uniformly. It provides a snapshot of the infant universe approximately 380,000 years after its birth.
Cosmic Microwave Background: The cosmic microwave background (CMB) is the oldest light in the universe, a faint glow that permeates all of space. It is the remnant radiation from the Big Bang, the intense heat and energy that gave birth to the universe nearly 14 billion years ago.
CP Violation: CP violation is a fundamental concept in particle physics that describes the asymmetry between matter and antimatter. It refers to the observation that certain physical processes do not exhibit complete symmetry between particles and their corresponding antiparticles, which has important implications for the evolution of the universe.
Dark Energy: Dark energy is a mysterious and pervasive form of energy that is believed to be the dominant component of the universe, accounting for approximately 68% of its total energy content. It is a fundamental concept in modern cosmology and has profound implications for our understanding of the universe's past, present, and future.
Dark matter: Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects. It constitutes about 27% of the universe's mass-energy content.
Dark Matter: Dark matter is a hypothetical form of matter that cannot be directly observed but is believed to make up a significant portion of the universe's total mass. It is a crucial component in our understanding of cosmology and the structure of the universe.
The term 'dark matter' refers to the fact that this type of matter does not emit, reflect, or absorb light, making it invisible to traditional astronomical observations. Its existence is inferred from its gravitational effects on visible matter and the large-scale structure of the universe.
Electroweak epoch: The electroweak epoch is a period in the early universe during which the electromagnetic force and weak nuclear force were unified into a single electroweak force. This epoch occurred approximately $10^{-36}$ to $10^{-12}$ seconds after the Big Bang.
GUT epoch: The GUT epoch is a period in the early universe, occurring between $10^{-43}$ and $10^{-36}$ seconds after the Big Bang, when the strong, weak, and electromagnetic forces were unified into a single force. It marks an important phase in cosmology where Grand Unified Theories (GUTs) are tested.
Hubble constant: The Hubble constant is the rate of expansion of the universe, typically measured in kilometers per second per megaparsec (km/s/Mpc). It quantifies how fast galaxies are moving away from each other due to the expansion of the universe.
Hubble Constant: The Hubble constant is a fundamental parameter in cosmology that describes the rate of expansion of the universe. It represents the relationship between the distance to a galaxy and its recession velocity, providing crucial insights into the evolution and age of the universe.
Hubble's Law: Hubble's law is a fundamental principle in cosmology that describes the relationship between the distance and the recessional velocity of galaxies in the expanding universe. It states that the farther a galaxy is from the observer, the faster it appears to be moving away from the observer.
Inflation: Inflation is a sustained increase in the general price level of goods and services in an economy over time. It is a fundamental concept in macroeconomics, as it measures the rate at which the purchasing power of a currency is eroded, leading to a decline in the real value of money.
Inflationary scenario: An inflationary scenario is a cosmological model proposing that the early universe underwent an exponential expansion in volume within a fraction of a second after the Big Bang. This rapid expansion helps explain the homogeneity, isotropy, and flatness observed in the current universe.
Neutrino oscillations: Neutrino oscillations are the phenomenon where a neutrino changes its flavor (type) as it propagates through space. This implies that neutrinos have mass and can transform among three types: electron, muon, and tau neutrinos.
Neutrino Oscillations: Neutrino oscillations refer to the phenomenon where neutrinos, which come in three distinct types or 'flavors' (electron, muon, and tau), can spontaneously change from one flavor to another as they travel through space. This quantum mechanical effect is a consequence of neutrinos having a tiny but non-zero mass and the mixing of the neutrino mass eigenstates.
Quantum Field Theory: Quantum field theory is a fundamental framework in physics that combines the principles of quantum mechanics and special relativity to describe the behavior of subatomic particles and the interactions between them. It provides a unified mathematical description of all the fundamental forces of nature, including electromagnetism, the strong nuclear force, and the weak nuclear force.
Redshift: Redshift is the phenomenon where the wavelength of light emitted by an object appears to be shifted towards longer, or 'redder', wavelengths. This occurs when the object is moving away from the observer, as predicted by the Doppler effect. Redshift is a crucial concept in the fields of relativity and cosmology, providing insights into the expansion of the universe and the motion of celestial bodies.
Standard Model: The Standard Model is the most comprehensive and well-tested theory in particle physics that describes the fundamental particles and the interactions between them. It encompasses three of the four basic forces in nature: the strong, weak, and electromagnetic forces, leaving out the fourth force, gravity.
Superforce: The superforce is a hypothetical force in the early universe that unified all four fundamental forces: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. This concept is pivotal in theories of cosmology and particle physics, particularly during the Planck epoch.
Supersymmetry: Supersymmetry is a proposed extension to the Standard Model of particle physics that introduces a new fundamental symmetry between bosons (force carriers) and fermions (matter particles). This symmetry predicts the existence of a superpartner for every known particle, which could help resolve some of the outstanding issues in particle physics and cosmology.
TOE epoch: The TOE (Theory of Everything) epoch is a period in the early universe when all fundamental forces were unified. This era occurred immediately after the Big Bang, roughly within $10^{-43}$ seconds.