Labels:text | screenshot | font | number OCR: FACT FILE IN ORDER FOR A BLACK HOLE to form around the Earth, the planet would have to be compressed until it had a diameter of just 1 cm (0.4 in). The boundary of a black hole is called the event horizon. Once inside the event horizon, nothing can escape from the hole. The force of gravity at the event horizon is so powerful that if a book weighing 1 kg (2.2 lb) on Earth were brought to within 6 m (20 ft) of it, the book would weigh 1,000 billion tonnes (1,100 billion tons).
