A geomagnetic reversal is a phenomenon where the Earth's magnetic field changes direction, causing the magnetic north and south poles to switch places. This process occurs over thousands to millions of years and is recorded in the geological layers of the Earth. During a reversal, the magnetic field may weaken, which can affect navigation systems and increase exposure to solar radiation. These reversals are part of the Earth's natural magnetic cycle and have occurred many times throughout history. The last major reversal, known as the Brunhes-Matuyama reversal, happened about 780,000 years ago. Scientists study these events to understand the Earth's magnetic history and its impact on life.