If the sun were to suddenly disappear, it would have catastrophic effects on life on earth. Without the sun's energy, the Earth's temperature would rapidly drop, and all photosynthesis would cease. As a result, plants and other life forms would die off, leading to mass extinctions. In addition, without the sun's light, it would be dark all the time and most animals would struggle to survive. The lack of sunlight would also drastically reduce the amount of oxygen in the atmosphere, making it difficult for humans and other animals to breathe. Ultimately, the Earth would become an uninhabitable place without the sun's energy.