There is not much point sending out signals to search for alien life because if they are advanced enough, they will have been watching Earth for thousands of years - being able to see bonfires set by the ancient Egyptians, for example.
Frank Drake, the pioneer and founder of the search for extraterrestrial intelligence (SETI), said he is against sending out signals to find alien life because it makes no sense.
Astronomer Drake conducted the first modern search for extraterrestrial life in the 1960s. He was also behind the Drake Equation – an experiment that quantifies the number of alien civilisations in the Milky Way based on probability.
In an interview with Space.com, the 84-year-old was asked about his thoughts on sending out signals to try to make contact with otherworldly civilisations. Currently, Seti astronomers listen out for radio signals rather than actively sending them to parts of the galaxy where habitable planets could be.
A debate is going on about whether we should do this – the ethical implications are wide-ranging. Some critics say we may end up coming across extraterrestrials intent on doing us harm and that it should not for a privileged few to decide.
However, Drake says the argument is essentially null and void: "There is controversy. I'm very against sending, by the way. I think it's crazy because we're sending all the time. We have a huge leak rate. It has been going on for years.
"There is benefit in eavesdropping, and you would have learned everything you can learn through successful Seti searches. There's all kinds of reasons why sending makes no sense.
"That reminds me of something else. We have learned, in fact, that gravitational lensing works. If they [aliens] use their star as a gravitational lens, they get this free, gigantic, super-Arecibo free of charge. They are not only picking up our radio signals, but they have been seeing the bonfires of the ancient Egyptians. They can probably tell us more about ourselves than we know... they've been watching all these years."
Drake also said the search for alien life is being hampered by a lack of funding. Speaking about their current efforts, he said they are searching for bursts of optical life possibly sent out by extraterrestrial civilisations. Seti will have a new instrument to perform this search in March.
"The whole thing is designed to look for laser flashes. The assumption is — and this is where it gets to be tenuous — the extraterrestrials are doing us a favour," he said. "It does depend on extraterrestrials helping you by targeting you. These stellar beams are so narrow that you've got to know the geometry of the solar system that you're pointing it at.
"They want to communicate. They have to be intent on an intentional signal specifically aimed at us. That's a big order. So there are required actions on the part of the extraterrestrials for this to work. The big plus is that it's cheap and relatively easy to do."
Space agencies across the globe are searching for planets located in habitable zones – where they are located far away enough from and close enough to for liquid water to exist.
Earlier in 2015, researchers came across five planets potentially located in the "Goldilocks" zone that were almost as old as the universe. This means any life that had evolved there would not be extremely advanced.
Tiago Campante, from the University of Birmingham's School of Physics and Astronomy, told IBTimes UK: "Imagine there are civilisations out there with a head start of five billion years. The human race has been here for 50,000 years. It's a huge difference.
"There's an analogy. It's like you have some ants living by the side of the road and humans are building a highway next to them. How can you explain to those ants what that highway means? You cannot. We could be those ants and there could be advanced civilisations living just next to us, but we cannot detect them and cannot not understand their ways. We don't have the means or intellect."