Atmospheric reentry is the process by which a spacecraft or object returns to the Earth's atmosphere from space. During this phase, the object encounters air resistance, which generates intense heat due to friction. This heat can reach temperatures exceeding 1,500 degrees Celsius, requiring special heat shields to protect the spacecraft and its occupants. Successful atmospheric reentry is crucial for missions involving human spaceflight, such as those conducted by NASA or SpaceX. Proper calculations and designs ensure that the spacecraft slows down safely and lands in a designated area, minimizing risks to both the crew and the environment.