phys 006 hwk quiz thing

Page 1: Laws of Motion and Gravity

• Acceleration of an Object

  • An apple falling from a tree experiences acceleration due to the force of gravity acting upon it.

• Gravitation Force Changes

  • Gravitational force increases with greater mass of objects.

  • Gravitational force decreases as the distance between objects increases.

• Mass vs. Weight

  • Mass: Amount of matter in an object; remains constant.

  • Weight: Force due to gravity; can change.

  • After eating a large meal, weight increases due to an increase in mass (food).

• Momentum Comparison

  • A pickup truck has more momentum than a motorcycle if both are moving at the same speed because momentum depends on mass (pickup truck has greater mass).

• Newton's Three Laws of Motion

  • First Law: An object remains at rest or in uniform motion unless acted upon by an external force.

  • Second Law: Force equals mass times acceleration (F = ma).

  • Third Law: For every action, there is an equal and opposite reaction.

Page 2: Newton's Laws and Celestial Phenomena

• Example of Newton's Laws Application

  • Rocket launches illustrate third law: as gases are expelled downwards, the rocket moves upwards.

• Conservation of Angular Momentum

  • Observed in ice skaters spinning faster when arms are pulled in.

• Effect of Moon's Proximity to Earth

  • If the Moon were closer, ocean tides would be stronger due to increased gravitational pull.

• Light Year Definition

  • Distance light travels in one year.

• Exploding Star Observation

  • If a star exploded 20 lightyears away, we would find out in 20 years due to light's travel time.

Page 3: Solar System Formation and Planet Characteristics

• Solar System Size Scale

  • In a scale model, Earth is the size of a small bead, Neptune is about 30 meters from the Sun.

• Types of Planets

  • Terrestrial Planets: Rocky, smaller, closer to the sun (hotter).

  • Jovian Planets: Gaseous, larger, farther from the sun (colder).

• Planetary Orbit Plane

  • Planets orbit on the same plane due to the rotating protoplanetary disk.

• Solar Nebula Elements

  • Hydrogen and helium predominated; heavier elements are needed for solid cores.

• Planetesimals and Frostline

  • Inside the frostline: rocky planetesimals due to too warm for ices.

  • Beyond the frostline: icy objects more common.

• Jovian vs. Terrestrial Gas Capture

  • Jovian planets capture more gas due to larger cores and location farther from the sun.

• Formation of Jovian Moons

  • Formed from gas and dust in minidisks around Jovian planets.

Page 4: Collisions and Comets

• Solar System Collision Objects

  • Main objects: asteroids and comets.

• Comets' Lifespan

  • Spend most of their lives in the Oort Cloud, appearing as icy bodies.

• Direction of Comet Tails

  • Comet tails point away from the sun due to solar wind and radiation pressure.

• Comet Origin and Fate

  • Originate from the Oort Cloud; can disintegrate after repeated solar passes or collide with celestial bodies.

• Meteor Showers

  • Occur when Earth passes through debris from a comet's orbit.

• Evidence of Collisions

  • Indicators include craters, orbital irregularities, and debris rings around moons and planets.

Page 5: Impact Craters and Space Objects

• Tenoumer Impact Crater

  • 1.9 km diameter; too small to have global consequences.

• Near Earth Objects (NEOs)

  • Important for predicting and preventing potential impacts threatening Earth.

• NASA’s DART Mission

  • Aim: Test asteroid deflection through collision with spacecraft.

• ESA’s Hera Mission

  • Purpose: Study effects of the DART impact, improve planetary defense strategies.

Page 6: Lunar Craters and Formation Hypothesis

• Moon's Crater Count

  • Moon has more craters than Earth due to lack of atmosphere and plate tectonics.

• Moon Formation Theory

  • Giant Impact Hypothesis: Moon formed from debris after a Mars-sized collision with early Earth.

• Sun vs. Earth Size

  • Sun’s radius ~109 times that of Earth; ~1.3 million Earths could fit inside it.

• Sun Composition

  • 73% hydrogen, 25% helium, 2% other metals.

Page 7: Sun's Stability and Nuclear Fusion

• Sun's Stability

  • Maintains constant size due to a balance between gravitational compression and nuclear fusion pressure.

• Core vs. Surface Temperature

  • Core is hotter (intense pressure leads to fusion).

• Nuclear Fusion Definition

  • Process where hydrogen nuclei fuse to form heavier nuclei; high temperatures needed to overcome repulsion between protons.

• Photon Escape

  • Takes thousands to millions of years to escape radiative zone due to re-absorption and emission.

• Convection Process

  • Heat transfer method where hot plasma rises and cool plasma sinks, creating energy transport.

Page 8: Solar Characteristics and Wind

• Photosphere Visibility

  • Visible because it is the layer where light can escape into space, while inner layers are opaque.

• Solar Wind Definition

  • Continuous stream of charged particles (electrons and protons) emitted from the Sun.

Page 9: Magnetic Field and Solar Activity

• Differential Rotation

  • Different parts of the Sun rotate at varying speeds (equator vs poles).

• Magnetic Field Changes

  • Twisting and tangling due to differential rotation leads to solar activity (sunspots, flares).

• Sunspot Formation

  • Cooler regions formed by magnetic activity inhibiting convection.

• Coronal Mass Ejections (CMEs)

  • Threat to Earth: can disrupt power grids and satellites.

• Aurora Formation

  • Charged particles from the Sun interact with Earth’s magnetic field and atmosphere, creating colorful lights.

Page 10: Light and Electromagnetic Spectrum

• Wavelength and Energy Relation

  • Inversely related; shorter wavelengths = higher energy photons.

• Electromagnetic Spectrum Regions

  • Gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves.

• Human Eye and Color Capture

  • Cones combine red, green, blue light to perceive color, similar to astrophysical imaging.

• Emission of Light from Moons

  • Moon B with higher temperature (1500 K) emits more light and at shorter wavelengths than Moon A (600 K).

• Infrared Telescopes

  • Detect heat radiation, useful for observing star formation, exoplanets, and dust clouds.

Page 11: Exoplanets and Detection Methods

• Challenges in Detecting Exoplanets

  • Difficulty arises from distance and brightness comparison with their stars.

• Doppler Effect in Exoplanet Discovery

  • Movement in a star’s motion indicates gravitational influence from an orbiting planet.

• Transit Method

  • Easier to detect gas giants due to greater light blockage compared to smaller planets.

• Infrared Telescopes

  • Easier to observe colder planets due to their higher infrared radiation emission.

• Direct Imaging Method

  • Only method to detect planets with perpendicular orbits to the line of sight.

Page 12: Habitable Zone and Planet Formation

• Habitable Zone Definition

  • Region around a star that could support liquid water, necessary for life.

• Surprise of Hot Jupiters

  • Contrary to solar system formation theories; gas giants should form far from stars beyond the frost line.

• Exoplanet Exploration

  • Example of Kepler-186f: Earth-sized, in the habitable zone, 500 lightyears away in Cygnus.

Page 13: Main-Sequence Stars and Classification

• Main-Sequence Star Definition

  • Stars that fuse hydrogen into helium in their cores, stable due to gravity and radiation balance.

• Massive Stars Characteristics

  • More massive stars are more luminous, hotter, and bluer due to gravitational pressure leading to higher fusion rates.

• Star Classification

  • Classifications from hottest to coolest: O, B, A, F, G, K, M; O-type stars have the shortest lifetimes.

• Hydrogen Fuel Lifetimes

  • More massive stars burn hydrogen faster, resulting in shorter lifetimes despite having more hydrogen.

• Cluster Observation

  • Younger clusters contain blue stars; older clusters (red) consist of stars evolved into giants or supernovas.