Wind and solar can deliver megawatts, but not stability. What keeps the grid alive is synchronous inertia — the spinning mass of big generators that resists shocks and buys time when things go wrong. As renewables grow, inertia shrinks, and grids from Australia to the UK are paying to buy it back. The future is not 100% renewables or 100% fossil, but a hybrid grid anchored by physics and balanced by storage and renewables.
