A black hole is a region of space-time which, due to the influence of gravity, nothing - including light and information - can leave. According to the General Theory of Relativity, it requires the accumulation of a sufficiently large mass in a sufficiently small volume in order to form. The black hole is surrounded by a mathematically defined surface called the event horizon, which marks the boundary of no return. It is called "black" because it completely absorbs light hitting the horizon, reflecting nothing. As black holes cannot be observed directly, their presence is inferred from their interaction with surrounding matter and with light and other types of electromagnetic radiation. The reverse of the coin shows a colourful representation of the appearance of a black hole. A real piece of meteorite is placed in the centre of the coin. The reverse of the coin is concave, which imitates the absorption of the surroundings by a black hole. The mintage of the coin is limited to 500 pieces only. The coin comes packed with a certificate of authenticity in an elegant wooden box.