If the Earth didn't have a magnetosphere, the planet would be bombarded with harmful radiation from the sun, known as solar wind. This radiation would damage the atmosphere, stripping it away over time. Without the atmosphere, the Earth's surface would be exposed to extreme temperatures and harsh solar radiation, making it inhospitable for most forms of life. Furthermore, the lack of a magnetosphere would also prevent the Earth from maintaining a stable climate and could lead to drastic changes in weather patterns, potentially leading to even more catastrophic consequences for life on Earth.