Einstein redefined gravity not as a force between masses, but as the curvature of spacetime . Massive objects like stars and planets warp the "fabric" of the universe, and this curvature dictates how objects move. 3. The Standard Model: The Building Blocks

Matter is composed of quarks (which make up protons and neutrons) and leptons (such as electrons).

Objects like electrons and photons exhibit properties of both particles and waves. They are neither one nor the other exclusively, but a "quantum" entity that behaves differently depending on how it is measured.

At the atomic level, nature behaves in ways that defy everyday intuition.