GCSE Astronomy — The Earth–Moon–Sun System

Led by Aristarchus of Samos

Module 3 of Edexcel GCSE Astronomy. Led by Aristarchus of Samos — the geometer who measured the relative sizes and distances of the Earth, Moon, and Sun with no telescope and no clock, only angles and shadow-cones. Tides, precession, and eclipses follow as further consequences of the same geometry.

1. Module 3

   The Earth–Moon–Sun System

   Led by Aristarchus of Samos

   The question

   What are the actual sizes and distances of the three bodies most visible to a naked-eye observer, how were those numbers first established, and what consequences does the geometry of the system have for the things you can directly observe — tides, precession, and eclipses? The spec asks the student to know the relative sizes and distances by ratio and by figure, to understand and reproduce in outline the Aristarchus–Eratosthenes measurement chain that established them, to account for tidal patterns and the slow wobble of the Earth's axis that shifts the equinoxes through the zodiac across millennia, and to analyse both solar and lunar eclipses by their four umbral contacts and the alignment that produces each.

   Outcome

   the student can apply the size and distance ratios in the Earth–Moon–Sun system, reproduce the Aristarchus–Eratosthenes chain in outline, distinguish spring and neap tides, define precession and quote its rate, and analyse both solar and lunar eclipses including the four umbral contacts of each. *(Edexcel 1AS0 Paper 1 — Topic 3, spec points 3.1–3.10)*

   Sub-units

   1. ○ 3.1 Sizes and distances in the Earth–Moon–Sun system Open this unit → ✓ ↻
   2. ○ 3.2 The Aristarchus–Eratosthenes measurement chain Open this unit → ✓ ↻
   3. ○ 3.3 Tides: spring, neap, and the lunar–solar contribution Open this unit → ✓ ↻
   4. ○ 3.4 Precession of the equinoxes Open this unit → ✓ ↻
   5. ○ 3.5 Solar and lunar eclipses Open this unit → ✓ ↻
   Begin the course → Print certificate of completion