Evidence is the deciding factor in science. A hypothesis is never accepted based on the status of the person proposing it — only on reproducible experimental evidence. Scientific theories require an overwhelming amount of evidence.
Celestial sphere: an imaginary sphere surrounding Earth on which stars appear fixed. NOT real — just a conceptual model.
"Planet" comes from the Greek asters planetei ("wandering stars") — five naked-eye objects that moved relative to fixed stars: Mercury, Venus, Mars, Jupiter, Saturn.
Constellations are 2D projections of stars at vastly different distances — NOT real physical clusters. Stars in a constellation are typically far apart in 3D space. Astrology and horoscopes are not science.
Galileo (1564–1642) was the first to use a telescope astronomically (not its inventor). His four key observations supporting heliocentrism:
Tycho Brahe (1546–1601): meticulous observational astronomer who made the most precise naked-eye measurements of planetary positions ever recorded. Ironically still favored a geocentric model. His data were used by Kepler to derive the 3 laws of planetary motion.
Johannes Kepler (1571–1630) used Brahe's data:
Age of solar system: 4.56 billion years.
Materials condense from gas to solid at different temperatures based on distance from the Sun:
Planetesimals are the "Lego building blocks" of planets — small solid bodies formed by condensation. Accretion = gravity pulling these together into progressively larger bodies (protoplanets → planets). Gas giants additionally accreted huge H/He envelopes once their solid cores reached ~10 Earth masses, triggering runaway gas accretion.
Write your response, then submit to reveal the self-grading checklist. Check each point you covered to calculate your score.