Aliens could be trying to get through to us right now and we might not even know it. Even if another intelligent species were trying to transmit a message to Earth, a weak radio signal from some distant galaxy could get lost in the chaos of light and noise from cell phones, wifi, TV and radio broadcasts, satellites, microwaves, traffic jams, and cities that never sleep.
That signal also has to contend with disruptive cosmic phenomena like black hole collisions and fast radio bursts being zapped through space before it reached a network of SETI (search for extraterrestrial intelligence) radio telescopes.
"By far the biggest challenge in radio SETI is what we call radio frequency interference,” UC Berkeley SETI Research Center director Andrew Siemion told Seeker. “Because we use our own technology as an example of what we should be looking for, we in fact find many, many examples of our own technology, and those examples actually pollute the signal that we see, especially with radio telescopes.”
How exactly would we be able to tell an extraterrestrial signal apart from all this visual and auditory pollution? The Wow! signal that was thought to be first contact for years was actually revealed to be the radio frequency emitted by the hydrogen gas from two comets. Hypersensitive instruments have been set off more than once by triggers that were much closer than scientists thought, including that one infamous case where the source of what was assumed to be a hello from aliens was actually no further than the visitor center of the observatory — a microwave oven without proper shielding had probably been heating up someone’s frozen pizza.
It has only been in the last 50 or 60 years that SETI technology has received a boost from advances in astrophysics and technology that have made it possible to know what we’re looking for in the search for far-out signals. Now that AI exists and computer brains can be taught what to look for, we can analyze data faster and search through more types of signals. We are now able to search 10 billion radio channels as opposed to the hundred or two hundred that could be investigated when SETI investigations first started. Scientists may even be getting closer to finding out which part of the electromagnetic spectrum we should be watching if we expect a signal from another planet.
"Technology exhibits a very high degree of what we call coherence, which means that ultimately electrons usually move in a very regular way through some piece of technology,” said Siemon. “That property of coherence is fundamentally the way in which we tell the difference between a natural astrophysical object and an example of technology.”
Meaning, signals from another civilization out there should be distinct and exhibit consistency. The only question is exactly what distinction we should expect. Because scientists are now able to experiment with different parts of the electromagnetic spectrum and run tests on suspicious signals, every one of them has been ruled out by some kind of interference, but that doesn’t mean aliens are doomed to stay in sci-fi. SETI has only gone through a couple thousand star systems so far, which is nothing when you realize there are over a hundred billion stars that could be hiding something.
Maybe this will make you put down your smartphone for a while.