For most of the 19th and 20th centuries, it was believed that there could be no life in the shadows of the Earth. The sun supplies energy and without it, there could be no life. In 1830, the ocean floor was thought to be sterile since sunlight cannot penetrate deeper than 600 metres. But in the 1950s, marine biologists observed a flatfish more than 10 kilometres under the sea. This was considered life out of place until 1977, when a community of aquatic creatures was discovered around a volcanic ocean vent at a depth of two kilometres. Since then, many lifeforms have been discovered that thrive in conditions destructive to life as it was known.