It is estimated that there are between 100 and 200 billion galaxies in the observable universe, according to BBC Sky at Night Magazine. Each galaxy contains at least 100 to 200 billion planets. With this vast number of planets in the universe, scientists consider that there might be some life form on at least one of those planets. As to why the Earth has still not encountered other alien lifeforms, scientists have proposed numerous explanations. One of these is the Dark Forest theory.

The idea of the Dark Forest came from the science fiction novel The Dark Forest by Chinese author Liu Cixin. The novel discusses the best way to interact with potentially hostile life.

The Dark Forest theory presents an analogy that our universe is like a dark forest filled with unknown things. The Earth is a hunter lurking in the dark while making sure that no sound is produced. Inside the forest are other hunters, analogous to extraterrestrial species hiding from one another. This theory suggests that if another hunter within the forest finds a hunter, they will immediately kill each other to ensure survival.