Spacetime in A tour of cosmology: the Big Bang, stars, galaxies, and black holes

You'll be able to explain how Einstein's equivalence principle forces mass to warp spacetime geometry, turning gravity from a force into the curvature that governs every orbit, light-bend, and clock-tick in the universe.

You'll be able to articulate why Hubble's observations mean space is expanding — not galaxies flying through space — and why that subtle distinction changes everything about the Big Bang's origin story.

You'll be able to read the Schwarzschild metric's key terms and explain why the event horizon is a point of no return in spacetime geometry, not just an extreme gravitational well.

You'll be able to trace how the Friedmann equations emerge from Einstein's field equations applied to an expanding universe, and how they encode the Big Bang, dark matter, and dark energy in a single elegant framework.