#gravitation

3 articles

Black Holes

How escape velocity reaching the speed of light defines an event horizon, why the Sun would be 3 km across, and what a black hole would — and would not — do to Earth.

10 min read·Jul 15, 2026

Physics

Kepler's Laws of Planetary Motion

How Kepler's stubborn refusal to ignore a tiny discrepancy in Mars's orbit produced three laws that Newton later derived from a single inverse-square force.

10 min read·Jul 14, 2026

Astronomy & Cosmology

Galaxies and Dark Matter

Vera Rubin's flat rotation curves, gravitational lensing, and the Bullet Cluster all point to the same conclusion: galaxies are embedded in vast halos of unseen mass that gravitates but does not shine.

10 min read·Jul 3, 2026