Led by Johannes Kepler
About this course
The closing module of Paper 1 of the Edexcel GCSE Astronomy course is the synthesis the previous seven topics have been building toward: the laws of planetary motion that Kepler extracted from Tycho's Mars data, and the universal-gravitation explanation Newton gave them seventy-six years later.
It is led by Johannes Kepler, Tycho's mathematical assistant, who spent four years trying to fit Mars to a circle, encountered an eight-arc-minute residual that refused to disappear, and concluded that planetary orbits are ellipses with the Sun at one focus. The eight arc-minutes "could not be ignored." That refusal to round away an inconvenient discrepancy is what destroyed two thousand years of cosmology and built the science of celestial mechanics.
The student leaves the module able to state and apply Kepler's three laws, define and use aphelion/perihelion and apogee/perigee, work problems with the Third Law T²/r³ = constant, explain why the constant depends on the central body's mass, state Newton's universal law of gravitation, and explain how it derives Kepler's laws from a single inverse-square principle.
Led by Johannes Kepler
The question
What are the laws governing the motion of planets around the Sun, where did they come from, and what physical principle explains them? The spec asks the student to understand the observational contribution of Tycho Brahe and the mathematical contribution of Copernicus and Kepler to the heliocentric transition, the role of gravity in producing stable elliptical orbits, all three of Kepler's laws of planetary motion (with quantitative use of T²/r³ = constant), the orbital terms aphelion/perihelion and apogee/perigee, the inverse mass dependence of the Third Law constant, and Newton's universal law of gravitation as the unified explanation Kepler's three empirical laws ultimately rest on.
Outcome
the student can describe the observational and mathematical contributions to the heliocentric transition, state and apply all three of Kepler's laws (including quantitative use of T²/r³), define and apply the orbital terms aphelion, perihelion, apogee, perigee, account for the mass dependence of the Third Law constant, and state Newton's universal law of gravitation and how it derives Kepler's laws. *(Edexcel 1AS0 Paper 1 — Topic 8, spec points 8.1–8.9)*
Sub-units