This question has puzzled human minds going back to the ancient Greeks over 2000 years ago. Is there intelligent life elsewhere in the Universe?  Or are we alone? In 1950, the physicist Enrico Fermi asked the question: “If the Universe is so large and so old, where is everybody?” This has become known as the Fermi Paradox.

Yet after all these centuries of wondering and after decades of using SETI* to listen for signals from other civilizations emanating from the deep cosmos, we only know two fundamental facts:  we have no concrete evidence that intelligent aliens have ever visited our planet or have ever tried to contact us; and, second, we have no evidence that there is any life outside Earth, intelligent or not.

Now astrophysicist Ethan Siegel picks up where Fermi left off with Are Aliens Plentiful, But We’re Just Missing Them?

Siegel discusses how we are and can use energy to contact (or at least look for) intelligent life elsewhere.

For 6 decades SETI has been using radio and other telescopes to listen for or identify electromagnetic signals, which include any form of light of any wavelength that would indicate the presence of intelligent life.

But Siegel reminds us we have other alternatives as well. As of last year we detected the first gravitational waves in the Universe coming from black holes and colliding neutron stars. So if intelligent beings are sending signals by gravitational waves, we are developing the ability to create sophisticated equipment to receive those signals.

Another possible vehicle to identify intelligent life is searching for neutrino signals especially if they are created by non-stellar fusion. Fusion power emits a very specific neutrino (or antineutrino) signature as a by-product, which indicates it is not a natural process of stars. As Siegel says, “so long as they’re making power, we can find them.”

Of course all of us will continue looking for space probes, either robotic, computerized, free-floating or inhabited, which has made its way towards Earth. Yet, for all our “UFO sightings” and conspiracy theories, we have no evidence any such probe has ever found its way to our part of the galaxy.

Siegel sends us out to look for aliens on a positive note: “Perhaps someday — perhaps even someday soon — the Universe may have the most pleasant surprise of all in store for us: the news that we aren’t alone, after all.”


* Search for Extraterrestrial Intelligence


As an aside, there are some who believe that we are alone in the Universe, that life itself is very difficult to create, and intelligent life almost an impossibility.  For those views see The Great Filter Might Be What’s Preventing Aliens from Reaching Us and Where are all the Aliens?

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