Early Astronomy and Heliocentrism

Early Findings in Astronomy

• Ancient Greeks laid the foundation for astronomical thought, focusing on logic and observation
• Aristotle proposed a geocentric model (Earth-centered universe) based on philosophical reasoning, not empirical evidence
• Ptolemy developed the Ptolemaic model, incorporating epicycles to explain planetary retrograde motion
• Key limitation: Ancient Greeks lacked tools for direct testing, relying on philosophy

Copernicus

• Proposed a heliocentric model (Sun-centered universe)
• Published "On the Revolutions of the Heavenly Spheres," outlining how planets orbit the Sun in circular paths
• This challenged the dominant geocentric model, though initially lacked strong observational support

Galileo Galilei

• Developed telescopes for observing celestial bodies
• Major discoveries challenged the idea of heavenly perfection:
  • Moons of Jupiter (Galilean moons), proving not all celestial objects orbit Earth
  • Phases of Venus, supporting the heliocentric model
  • Sunspots and craters on the moon

Kepler's Three Laws of Planetary Motion

• First Law (Law of Ellipses): Planets orbit the Sun in elliptical paths, with the Sun at one focus
• Second Law (Law of Equal Areas): A line joining a planet and the Sun sweeps out equal areas during equal intervals of time
• Third Law (Harmonic Law): The square of a planet's orbital period is proportional to the cube of its average distance from the Sun
• Kepler's laws were based on Tycho Brahe's detailed observations

Newton's Three Laws of Motion

• First Law (Law of Inertia): A body at rest remains at rest, and a body in motion continues in motion with the same speed and in the same direction unless acted upon by an external force
• Second Law (F = ma): Force equals mass times acceleration
• Third Law (Action-Reaction): For every action, there is an equal and opposite reaction

Laws of Conservation

• Energy: Energy cannot be created or destroyed, only transformed
• Momentum: Linear momentum (p=mv) is conserved in a closed system unless acted upon by an external force; Angular momentum (L=Iω) is conserved

Universal Law of Gravitation

• Describes the force of gravity between two masses
• Formula: F=Gm₁m₂/r² (where G is the Gravitational constant, m₁ and m₂ are masses, and r is the distance between their centers)
• Applicable to planetary orbits, tides, and satellite motion

Types of Spectra

• Continuous Spectrum: Produced by dense objects, emitting light at all wavelengths
• Emission Spectrum: Consists of bright lines at specific wavelengths, formed from excited atoms in a low-density gas losing energy
• Absorption Spectrum: Formed when light passes through a cool gas, showing dark lines where certain wavelengths have been absorbed

Structure & Phases of Matter

• Matter is composed of atoms, which consist of a nucleus (protons and neutrons) and orbiting electrons
• Phases of matter include solid, liquid, gas, and plasma
• Transitions between phases occur due to changes in temperature or pressure

Interactions Between Radiation & Matter

• Radiation can be absorbed, emitted, scattered, reflected, or lead to ionization of atoms
• Examples include heating, energy release, change in direction and stripping electrons from atom.

Causes of Earth's Seasons

• Earth's axis is tilted at 23.5° relative to its orbital plane
• Seasons result from the changing angle of sunlight hitting different hemispheres as the Earth orbits the Sun

Motion of the Moon

• Moon orbits Earth in an elliptical path, taking approximately 27.3 days.
• Synchronous rotation keeps one side (near side) always facing Earth

Lunar Phases, Tides, and Eclipses

• Lunar phases are caused by the Moon's changing position relative to Earth and the Sun
• Tides are generated by the gravitational pull of the Moon and, to a lesser extent, the Sun
• Eclipses occur when the Sun, Earth, and Moon align, casting shadows

Main Properties of Telescopes

• Aperture: Diameter of the telescope, affecting light-gathering ability and resolution
• Resolution: Ability to distinguish fine details and separate closely spaced objects
• Magnification: The enlargement of an image, often limited by the telescope's aperture and atmospheric conditions
• Field of View: Extent of the sky visible through the telescope

Comparison of Telescopes Across the Electromagnetic Spectrum

• Telescopes are designed to detect different types of electromagnetic radiation (e.g., radio waves, visible light, X-rays)

Theory of Solar System Formation

• Nebular hypothesis: Explains the formation of the solar system from a collapsing cloud of gas and dust
• Stages include cloud collapse, spinning disk formation, sun formation, accretion of planetesimals, protoplanet formation, planetary differentiation

Earth's Atmospheric Layers, Temperature, and Pressure Profiles

• Atmospheric layers (lowest to highest): Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere
• Temperature and pressure profiles vary based on altitude, influenced by factors like gas composition, solar radiation absorption, and altitude.

Earth's Interior Structure

• Layers based on composition and physical state: Crust (outer, solid layer), Mantle (convective, semi-solid layer), Outer Core (liquid iron and nickel), Inner Core (solid iron-nickel alloy, hot)

Geologic Features of Terrestrial Worlds

• Surface features (craters, volcanoes, oceans, mountains) vary based on a planet's geologic activity. Factors include size, mass, internal heat, and distance from the Sun.

Role of Jovian Planets in Solar System Formation

• Jovian planets affected the distribution of gas and debris, protecting inner planets, and influencing orbital resonances

Comparison of Jovian Moons with Earth's Moon

• Jovian moons exhibit a wide range of sizes, geological activities, and possible habitability conditions, distinct from Earth's Moon

Role of "Leftovers"

• Leftover materials in the solar system include asteroids, comets, and meteoroids
• Understanding their composition and orbits helps explain the early solar system

Properties of Extrasolar Planets

• Extrasolar (exoplanets) are planets outside of our solar system

Contribution of Extrasolar Planets to Solar System Formation

• Discoveries of exoplanets challenged traditional assumptions about planetary system formation, particularly for gas giants
• Improved models like core accretion and disk instability are refined