Cosmology Key Terms and Concepts

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Questions and Answers

What is the predicted temperature of the Cosmic Background Radiation (CMB)?

A few degrees Kelvin above absolute zero (correct)

Millions of degrees Kelvin

Hundreds of degrees Kelvin

Thousands of degrees Kelvin

According to the Big Bang theory, what caused the stretching of the radiation from the early universe?

The expansion of the universe (correct)

The gravitational pull of massive objects

The increasing density of the universe

The interaction of radiation with interstellar gas

Which of these is NOT a prediction made by the Big Bang theory regarding the Cosmic Microwave Background (CMB)?

The CMB should be concentrated in specific regions of the sky. (correct)

The CMB should exhibit small temperature fluctuations.

The CMB should have a nearly perfect blackbody spectrum.

The CMB should be uniformly present in all directions.

What phenomenon provides insights into the early universe's homogeneity and isotropy based on the Big Bang theory?

The uniformity of the Cosmic Microwave Background (CMB) Signup and view all the answers

What does the 'redshift' of the CMB refer to?

The stretching of the wavelengths of the CMB due to the expansion of the universe. Signup and view all the answers

What was one of the main contributions of Ptolemy's Almagest?

It provided a comprehensive explanation of the solar system, including the motion of planets, based on a geocentric model. Signup and view all the answers

Which of these statements accurately reflects Ptolemy's Almagest?

It proposed that the Earth is a point in space and has no discernible size compared to the vast distance of the fixed stars. Signup and view all the answers

What is the significance of Copernicus' Commentariolus in the history of astronomy?

It was a theoretical treatise that outlined a heliocentric model of the universe, challenging the prevailing geocentric view. Signup and view all the answers

What is one of the key differences between Ptolemy's Almagest and Kepler's Laws of Planetary Motion?

Kepler's Laws offered a more accurate description of planetary motion, while Ptolemy's model was based on circular orbits and epicycles. Signup and view all the answers

Which of the following concepts was NOT part of Ptolemy's Almagest?

The Earth revolves around the Sun, challenging the existing geocentric model. Signup and view all the answers

What is the primary cause of the redshift observed in the spectra of distant galaxies, according to the content?

The Doppler effect due to the galaxies' motion away from us. Signup and view all the answers

What is the relationship between the Hubble Law and the expansion of the universe?

The Hubble Law provides evidence for the expansion of the universe. Signup and view all the answers

What is the significance of the cosmic microwave background (CMB) in the context of the Big Bang theory?

The CMB represents the leftover heat from the Big Bang and provides evidence for it. Signup and view all the answers

Which of the following phenomena are directly related to the process of recombination in the early universe?

The decoupling of photons from matter. Signup and view all the answers

Which of the problems listed is NOT addressed by the theory of cosmic inflation?

The evolution of the universe from its initial singularity (Big Bang). Signup and view all the answers

What is the main implication of the statement that the universe expands adiabatically?

The expansion of the universe is not driven by any external energy source. Signup and view all the answers

In the context of the universe's expansion, what is 'cosmic time dilation'?

The slowing down of time as observed from distant galaxies. Signup and view all the answers

According to the content, what is the most straightforward explanation for dark energy?

The energy associated with the vacuum itself. Signup and view all the answers

What was Kepler's significant inference regarding the orbits of planets?

They are elliptical. Signup and view all the answers

Which discovery by Galileo provided evidence for a heliocentric model of the universe?

The phases of Venus. Signup and view all the answers

Tycho Brahe's model of the universe is best described as which of the following?

Geo-heliocentric. Signup and view all the answers

What assertion was made by Copernicus regarding the center of the universe?

The sun is the center of the universe. Signup and view all the answers

What observation did Tycho Brahe make that contributed to changing the understanding of the heavens?

He discovered a supernova in Cassiopeia. Signup and view all the answers

Which characteristic describes the telescopes developed by Galileo?

One with 3x and another with 30x magnification. Signup and view all the answers

What element of Copernicus's theory challenges traditional beliefs about celestial spheres?

The ratio of Earth's distance from the sun to its radius. Signup and view all the answers

What is one of the main contributions of Galileo to modern science?

Establishing the scientific method. Signup and view all the answers

What did Lemaître propose about the early state of the Universe?

It originated from a hot and dense primeval atom. Signup and view all the answers

Which of the following describes the scale factor in the context of the universe's dynamics?

It describes how the Universe expands or contracts. Signup and view all the answers

Which principle states that the Universe is both homogeneous and isotropic?

Cosmological principle. Signup and view all the answers

According to Kepler's laws, what shape do planets' orbits follow?

Elliptical orbits with the Sun at one focus. Signup and view all the answers

What did Newton's law of universal gravitation help to discover?

The relationship between mass and force. Signup and view all the answers

What does the term Ω represent in the context of FRWL Dynamics?

The ratio of the actual density to the critical density. Signup and view all the answers

What does Newton's first law state about an object at rest?

It remains at rest unless acted on by a net external force. Signup and view all the answers

What is one of the key differences between Kepler and Newton's approaches to planetary motion?

Kepler focused on mathematical laws while Newton emphasized forces. Signup and view all the answers

What characterizes a dynamic universe in the context of FRWL Cosmology?

It continuously expands or contracts over time. Signup and view all the answers

What was one of Kepler's motivations for studying planetary motion?

To uncover the divine laws governing planetary motion. Signup and view all the answers

What was the universe mainly composed of at 10⁻⁶ seconds after the Big Bang?

A dense soup of quarks, gluons, photons, electrons, and neutrinos Signup and view all the answers

Which of these events happened first in the early universe?

The separation of the strong nuclear force and the electroweak force Signup and view all the answers

What is the significance of the 'cosmic neutrino background'?

It is the remnant radiation from the Big Bang, similar to the cosmic microwave background Signup and view all the answers

Why couldn't heavier elements form during primordial nucleosynthesis?

The universe cooled too quickly, preventing heavier nuclei from forming Signup and view all the answers

What is a 'standard candle' in astronomy?

A type of star that has a known intrinsic brightness, used to determine distances Signup and view all the answers

What is the significance of Henrietta Leavitt's discovery about Cepheid variable stars?

It enabled the measurement of distances to other galaxies Signup and view all the answers

What is the Doppler effect and how does it relate to astronomy?

It explains the change in color of light waves due to the motion of celestial objects Signup and view all the answers

Which of the following best describes why a distant ambulance's siren sounds lower pitched as it moves away?

The siren's sound waves are stretched as the ambulance recedes Signup and view all the answers

Study Notes

Key Terms

Cosmology: The ultimate archaeological science that examines the deepest realms of the universe.
Isotropy: The universe looks the same from all angles, regardless of the observer's location.
Cosmological principle: The universe is homogeneous and isotropic.
Cosmological constant (Λ): A component in Einstein's equations.
Omega (Ω): A crucial parameter in Friedmann-Lemaître-Robertson-Walker (FLRW) dynamics, used to determine the universe's geometry.
- Ω = 1 (critical density): Universe is flat.
- Ω > 1 (closed universe): Universe has positive curvature.
- Ω < 1 (open universe): Universe has negative curvature.
Redshift: The stretching of light waves due to the universe's expansion, causing the light to shift towards the red end of the spectrum.
Blackbody: A perfect object that absorbs all incident light and radiation, re-emitting it based on its temperature.

Timeline

Mesopotamian cosmology: Described a flat, circular Earth within a cosmic ocean.
Rigveda: Contains cosmological hymns.
Anaximander (6th century BCE): Proposed that the universe originated from an indefinite, boundless substance (aperion).
Pythagoras (6th century BCE): Developed a geocentric worldview believing the Earth is a sphere.
Democritus (460-370 BCE): Proposed atomic theory, stating that matter is composed of indivisible particles.
Plato (428-348 BCE): Developed a geometric worldview based on mathematical principles and Platonic Solids.
Aristotle (384-322 BCE): Proposed a geocentric model with 55 celestial spheres.
Seleucus (2nd century BCE): Proposed a heliocentric model, one of the first to do so.
Aristarchus (310-230 BCE): Developed a heliocentric model, one of the first to calculate size/distance to the moon and sun.
Archimedes (287-212 BCE): Made calculations of Earth's circumference using measurement of shadows.
Eratosthenes (276-194 BCE): Calculated the circumference of the Earth.
Apollonius: developed epicycle theory
Hipparchus (190-120 BCE): Made trigonometric tables and determined precession of the equinoxes.
Ptolemy (2nd century CE): Developed the geocentric model in his Almagest, which dominated for centuries.
Copernicus (1473-1543): Proposed a heliocentric model.
Kepler (1571-1630): Developed the laws of planetary motion.
Galileo (1564-1642): Provided support for the heliocentric model and made astronomical observations.
Newton (1643-1727): Developed the laws of motion and universal gravitation.
Friedmann & Lemaître: Independently discovered the expanding universe based on Einstein's general relativity equation.

Modern Concepts

Dark energy: A mysterious force driving the accelerating expansion of the universe (makes up 73%).
Baryonic matter: Ordinary matter like stars, planets, and humans (makes up 5%).
Dark matter: An unseen form of matter that interacts gravitationally with ordinary matter but does not emit light (makes up 25%).
Cosmological principle: The universe looks the same from all points of view.

Big Bang theory

The universe began with an extremely rapid expansion from a hot, dense state.
Evidence for the Big Bang includes Olber's Paradox, Hubble expansion, the cosmic microwave background (CMB), and helium abundance.
Key stages (after 3 minutes):
- Quark soup
- Neutrino decoupling
- Formation of protons and neutrons
- Primordial nucleosynthesis
The universe was too hot for atoms to form until ~380,000 years later.
The Big Bang is not fully understood but provides the foundation of the currently accepted standard model of cosmology.

Additional Concepts

Epicycle theory: An ancient model used to explain the apparent retrograde motion of planets.
Distance measurement: Techniques like using cepheid variable stars and the redshift of light from distant galaxies.
Doppler effect: How changes in the frequency of sound/light depend on the relative motion of the source and observer.
Inflation: A period of extremely rapid expansion in the very early universe.
Fundamental forces of nature: Gravity, electromagnetism, strong and weak nuclear forces.

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Description

This quiz covers essential terms and concepts in cosmology, examining how the universe is structured and behaves. Explore key ideas such as isotropy, the cosmological principle, and the implications of redshift. Test your knowledge on the fundamental aspects of the universe's dynamics and properties.