Led by Hipparchus of Nicaea
About this course
The fourth module of the Edexcel GCSE Astronomy course is the largest in Paper 1 — twenty-one spec points covering the entire structure of astronomical timekeeping, from the difference between a sidereal and a synodic day to the eighteenth-century chronometer that finally solved the longitude problem.
It is led by Hipparchus of Nicaea, the second-century-BCE astronomer Ptolemy called "a lover of truth" — the first to compile a reliable star catalogue, the discoverer of the precession of equinoxes (by comparing his measurements with those of Timocharis a century and a half before), and the establisher of the Western tradition of high-precision astronomical timekeeping. He is the right scholar for this material because every piece of it follows from his core question: how accurately do we have to measure time before the small irregularities of the heavens become visible?
The student leaves the module able to distinguish all of astronomical timekeeping's varieties (sidereal and synodic days, sidereal and synodic months; AST, MST, LMT, GMT, UT), build and apply the Equation of Time, determine local noon and longitude by shadow-stick, account for equinoxes and solstices, work with time zones, and outline both the lunar-distance and horological methods for finding longitude at sea.
Led by Hipparchus of Nicaea
The question
What does it mean to "tell the time" astronomically — and how many different times can the same instant be? The spec asks the student to navigate the difference between sidereal and synodic days, between Apparent and Mean Solar Time, between local time and Greenwich Mean Time; to build and apply the Equation of Time; to find local noon and longitude with nothing more than a shadow-stick and a chronometer; to account for equinoxes, solstices, and the annual variation in sunrise; and to understand the eighteenth-century longitude problem and the two methods (lunar-distance, horological) that solved it.
Outcome
the student can distinguish all the varieties of astronomical time named in the spec, build and apply the Equation of Time, determine local noon and longitude by shadow-stick, account for equinoxes and solstices and the seasonal variation in the Sun's apparent path, work with time zones and Greenwich Mean Time, and outline the two methods that solved the longitude problem at sea. *(Edexcel 1AS0 Paper 1 — Topic 4, spec points 4.1–4.21)*
Sub-units