Scientists say it could be 1,500 years before humans make contact with aliens, or for them to communicate with us. Astronomers from Cornell University combined two theories about the possibility of life existing on other planets to form a new one. One of these theories is the Fermi Paradox. This states that while billions of Earth-like planets exist in our galaxy, not one has made contact with Earth yet. The other, the mediocrity principle, suggests that because there is life on Earth, it will exist on Earth-like planets throughout the universe.

Researcher Evan Solomonides will present a paper on his theory. He said: "We haven't heard from aliens yet, as space is a big place, but that doesn't mean no one is out there." He said extraterrestrials could have received signals from Earth, but they may not have decoded them. He said they would need to decode and analyse 3,000 human languages to understand any messages. Signals from Earth have only reached about 8,500 stars; the Milky Way galaxy alone contains 200 billion stars. Solomonides said: "If we stop listening or looking, we may miss the signals, so we should keep looking."