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Questions and Answers
Who proposed the Planetesimal Theory?
Who proposed the Planetesimal Theory?
- James Jeans
- Thomas Chrowder Chamberlin (correct)
- Forest Ray Moulton
- Harold Jeffreys
The Tidal Theory suggests that planets formed from solid particles condensing.
The Tidal Theory suggests that planets formed from solid particles condensing.
False (B)
Name one drawback of the Planetesimal Theory.
Name one drawback of the Planetesimal Theory.
Hot material from the sun expands and dissipates rather than contract.
The Tidal Theory was proposed by ____ and Harold Jeffreys.
The Tidal Theory was proposed by ____ and Harold Jeffreys.
Match the following theories with their proponents:
Match the following theories with their proponents:
What is the first step in the formation of the solar system according to the nebular theory?
What is the first step in the formation of the solar system according to the nebular theory?
The nebular theory suggests that the solar system formed from a comet.
The nebular theory suggests that the solar system formed from a comet.
Name one drawback of the nebular theory.
Name one drawback of the nebular theory.
The process that forms celestial bodies from clumps of dust and grains is called __________.
The process that forms celestial bodies from clumps of dust and grains is called __________.
Match the following theorists with their corresponding contributions:
Match the following theorists with their corresponding contributions:
Which gases are primarily found in a nebula?
Which gases are primarily found in a nebula?
The encounter theory states that planets were formed from collisions with other celestial objects.
The encounter theory states that planets were formed from collisions with other celestial objects.
What is a planetesimal?
What is a planetesimal?
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Study Notes
Nebular Theory
- Solar system formation occurred approximately 4.5 billion years ago from a nebula, which is a giant cloud of gas and dust.
- Key components of a nebula include hydrogen, helium, and ionized gases.
- Formation involves three major steps: cloud collapse, formation of protoplanetary disk, and growth of planets.
Steps of Solar System Formation
- Cloud Collapse: Initiated by a shockwave from a supernova or the influence of a nearby star; gravity causes the center of the cloud to collapse as gas pressure fails to support its mass, leading to a spinning, denser region.
- Formation of Protoplanetary Disk: Metals and silicates form near the sun due to higher boiling points, leading to the creation of terrestrial planets with a limited metallic element reserve affecting their size.
- Growth of Planets: Dust and grains accumulate into clumps, forming planetesimals, which colliding together lead to the development of the planets.
Critiques of the Nebular Theory
- Particles surrounding Saturn repel each other, conflicting with the idea that dust would coalesce into planets.
- The theory fails to comply with angular momentum principles, suggesting the sun should spin faster than it does.
- Does not adequately consider the unusual rotation of Uranus and Venus, which rotate clockwise unlike other planets.
Proponents of the Nebular Theory
- Emmanuel Swedenborg (1688–1772)
- Immanuel Kant (1724–1804)
- Pierre-Simon Laplace (1749–1827)
Encounter Theory
- Proposes planets formed from material ejected from the sun during interaction with another celestial object, like another star.
- Divided into two forms: planetesimal theory and tidal theory.
Planetesimal Theory
- Suggests a passing star nearly collided with the protosun, causing it to eject material that condensed into planetesimals.
- Earth initially formed from a solid mass smaller than its current size.
- Supported by Thomas Chrowder Chamberlin and mathematically analyzed by Forest Ray Moulton.
Critiques of Planetesimal Theory
- No longer widely accepted due to evidence that hot solar material expands and dissipates rather than contracts.
- The passing star’s gravitational pull would disperse dust and gas rather than enable formation of planets.
Tidal Theory
- Suggests solar system formation resulted from a near-collision with a passing star, condensing hot gas into planets instead of planetesimals.
- Proposed by James Jeans and Harold Jeffreys in 1918.
Critiques of Tidal Theory
- Hot material from either star cannot contract, preventing the formation of planets successfully.
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