What the Einstein field equations relate — the curvature of spacetime (Gμν) to the energy-momentum tensor (Tμν)

Why Einstein needed Riemannian geometry — curved spacetime requires non-Euclidean mathematics

Riemannian geometry underpins general relativity, describing curved spacetime

What gravitational lensing confirms — mass curves spacetime and bends the path of light

Gravitational lensing confirms that mass warps spacetime, bending light's trajectory

What the Schwarzschild solution describes — spacetime geometry around a non-rotating spherical mass

The Schwarzschild solution describes the spacetime geometry around a non-rotating spherical mass

How Eddington's 1919 eclipse observation confirmed general relativity — starlight bent by the Sun

Eddington's eclipse observation showed starlight bending due to the Sun's gravity, confirming general relativity

How many types of fundamental forces are represented in the Standard Model of particle physics and which gauge bosons mediate each of these forces?

Four fundamental forces: electromagnetic (photon), weak (W and Z bosons), strong (gluons), gravity (graviton, not yet confirmed)

What the cosmological constant problem is — quantum field theory predicts vacuum energy 10^120 times too large

Quantum field theory overestimates vacuum energy by 10^120 times, causing the cosmological constant problem