The parallel postulate and new geometries: a maths EPQ idea
A title to start from
How did doubts about Euclid's parallel postulate lead to new geometries, and are they 'true'?
Why it works as an EPQ
Two thousand years of attempted proofs end with consistent alternative geometries, which raises a real question about truth in mathematics.
Scope and difficulty
Solid. Solid. Spherical geometry is accessible; hyperbolic geometry at the level of one model.
The maths
Builds on these A Level topics: Trigonometry · Proof.
You would learn:
- Euclid's postulates
- Spherical triangles and angle sums
- A model of hyperbolic geometry
One possible plan
- Set out Euclid's postulates and the parallel postulate.
- Show on a sphere that triangle angle sums exceed 180°.
- Describe one model of hyperbolic geometry.
- Judge what 'true' means for a geometry, with the role of physics.
Pitfalls
- Claims about relativity you cannot support.
- Pictures without mathematics.
Where to start reading
- Euclid's Elements (any good edition with commentary)
- Search for: spherical excess area of spherical triangle
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