Have you heard any of the stories lately about strange or mysterious radio signals coming from outer space? About every six months or so, a burst of excitement and discussion explodes around the world as reports come in from some telescope or probe and the unexplained nature of its observations. Whether is is an unusually strong signal from a sun-like star or a repeated pattern that seems too precise to be natural. But the question remains, Are we alone? No astronomer has ever wanted to rush out and claim that they have found aliens, however the astronomer that does find aliens will be cemented in history for generations to come.
In the 1960s, astrophysicist Jocelyn Bell Burnell was working with her adviser, Antony Hewish, with his brand new radio telescope near Cambridge, England. After scanning the sky, they recorded an unusual signal: A source in the sky was sending frequent, repeated bursts, separated by an eerily precise 1.33 seconds. The signal was so precise. Unaware of what this was, they named their source "LGM," which stands for "little green men." The LGM hypothesis started to weaken when they found multiple sources of the same. Finally, the theorists discovered that the signals were not caused by little green men, but rather little white neutron stars, wrapped in incredibly strong magnetic fields, beaming jets of radiation into space like a lighthouse. They now have a specific name: pulsars.
Another interesting encounter happened in 1977, astronomer Jerry Ehman was listening with a radio telescope operated by Ohio State University. After its scientific mission, the telescope was dedicated to SETI observations. And one night, a massive, bright, continuous signal fell into the telescope's narrow field of view. For 72 seconds, the source shouted into the radio telescope at a peculiar frequency: 1,420 megaherz, the frequency that neutral hydrogen naturally emits via a spin-flip transition of its electron. It was a very well known and distinct frequency, a cosmological calling card. Ehman was extremely impressed, but it has yet to be seen again.
In all of these cases, it is easy for speculation to overrun evidence. The public is ready and waiting for alien transmissions. We talk to each other with radio, and if the SETI Institute or other groups pick up a weird radio signal, maybe it's aliens talking to us, people surmise. The hypothesis that aliens are causing a mysterious radio signal is almost always incorrect. This is because intelligent creatures can create almost any signal they want. When a natural astrophysical explanation is not the strongest or the most convincing, there's often a temptation to wonder if aliens are behind it. If we cannot rule aliens out completely, why not believe they exist?
However, it's a very, very big leap to go from "We don't know what's causing this signal," to "Maybe aliens are causing this signal." Astronomers love their radio telescopes because they get useful science accomplished, but there are always a myriad of unexplained phenomena in the universe. That is exactly the reason astronomers remain employed; because there is so much out there that we simply don't understand. Maybe one day we will find the answers, but I personally hope they are all as cute as E.T.
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