Are aliens real?
It's a good question. There currently isn't any evidence for life on other planets, but the universe is a big place, and it seems unlikely that out of the trillions of planets presumed to exist in our 13.8 billion-year-old universe, only Earth has ever hosted life. (This disconnect between the vastness of the universe and the lack of evidence for alien life is known as the Fermi Paradox). Thus, the search for extraterrestrials is a serious business, and scientists are getting increasingly savvy about how to look for ET.
The first efforts in the search for extraterrestrial life started well before humans had the capacity to get off our own planet. According to the Search for Extraterrestrial Intelligence (SETI) Institute, the invention of radio opened the door to the idea of transmissions from other worlds, and inventors Nikola Tesla and Guglielmo Marconi both believed they might be picking up signals from Mars in the early 1900s.
The first serious radio-based search for extraterrestrial life occurred in 1960. It was masterminded by astronomer Frank Drake, who used two radio telescopes to search for signals from planets potentially orbiting stars 10 and 12 light-years away. Project Ozma, as it was known, turned up nothing. Nor did Project Phoenix, a private effort by the SETI Institute that ran from 1995 to 2000 and searched 800 star systems within 200 light-years of Earth.
The effort continues today with the Allen Telescope Array, a 42-antenna array that can tune in to microwave frequencies from across the Milky Way. The SETI Institute is also launching an effort to detect laser pulses that far-flung intelligent aliens might have sent as messages to the cosmos.
Of course, these efforts presuppose technologically advanced alien species. Scientists are also on the lookout for simpler life-forms, and advances in uncrewed spacecraft and remote sensing technologies are allowing them to search for molecules that might indicate something is out there.
Sensitive telescopes, like the James Webb Space Telescope, can pick up tiny variations in the light coming off of faraway exoplanets, allowing researchers to detect oxygen, sulfur or other gases that might indicate that microbes are at work there. Recent efforts also may have detected the first magnetic field around a distant Earth-like planet — a prerequisite for life to survive the harsh radiation of nearby stars.
In our own solar system, robots such as the Mars rover Perseverance are collecting samples in search of fossils or molecules that might suggest that microbial life flourished on the Red Planet billions of years ago, when it was warmer and wetter. Earthbound researchers are studying extreme environments, like the deserts of Chile and the depths of ocean trenches, to help guide this search. The hunt is a long shot, but planetary scientists are optimistic that new methods will reveal that we're not alone in the universe.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.