A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. It is formed when a massive star dies and its core collapses in on itself.
Black holes can vary in size, but the smallest ones are about the size of a city, while the largest ones can be billions of times more massive than our sun.
Black holes cannot be seen directly, but their presence is detected through their interaction with other matter in their surroundings. This can include the emission of high-energy radiation or the gravitational influence on nearby objects.
No, nothing can escape from a black hole once it has passed the event horizon, which is the point of no return. However, some particles can escape through a process called Hawking radiation, which is a result of quantum effects near the event horizon.
Black holes are not inherently dangerous to anything outside of their immediate surroundings. However, their immense gravitational pull can have a significant impact on their surrounding environment, such as disrupting the orbits of nearby stars and planets.