One of the most common tropes of science fiction is the encounter with extraterrestrial life, especially intelligent life, i.e., aliens. Most of the time, this really has been relegated to *just* science fiction, i.e., not science. However, like many topics of science fiction, this one might now be on the edge of being taken seriously by scientists. That isn’t to say no one has considered the possibility. The Drake Equation is discussed in most introductory astronomy courses, so many a current or former college student is aware that astronomers have for a number of decades now considered the possibility of intelligent aliens.
In his newest popular book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, Dr. Avi Loeb of Harvard has considered the possibility that we may have already encountered aliens. His hypothesis is that the interstellar object, dubbed Oumuamua, is most likely not an exotic comet or asteroid. And by “exotic”, I mean “very exotic,” since one recently espoused theory was that the object was/is a chunk of solid hydrogen. In a newer version of this same hypothesis now released in the press after the publication of Dr. Loeb’s book is that maybe the comet was solid nitrogen, making it maybe slightly less exotic since a solid nitrogen chunk should last longer than a solid hydrogen chunk. Anyway, after carefully considering such possibilities, Loeb dismisses natural explanations and concludes that Oumuamua was an extraterrestrial light sail. A light sail is thin metallic sheet used to convert the momentum of light hitting it into the momentum of the spacecraft its attached to. In the simplest version, these are small solar sails. However, for interstellar travel these sails would have to be larger, and probably encounter light from a strong pulsed laser. This isn’t just total conjecture. It seems to fit some aspects of the data, such as reflectivity, dimensions, and acceleration as it left the Solar System.
So, what should we make of this? I think its a sound application of the scientific process. Even if Oumuamua and other similar objects prove ultimately to be natural, its not unreasonable to consider more seemingly bizarre possibilities so long as they fit the data. They only seem more bizarre to us because we let our mind fill up with all of the past science fiction films we’ve seen. In reality, solid hydrogen or nitrogen is pretty bizarre to consider as well since we know of no such objects. But this is how science progresses. We consider the known, then take a look at some of these more oddball hypotheses as the known ideas get rejected since the known ideas just can’t fit the data. Do I really think its a derelict alien space ship? Most of my mind wants to cry out “No way!” But I think we need to seriously consider this.
As Loeb says, if intelligent life exists out there (and he suggests that it very likely does), then we will encounter ET eventually. If not now, then in 10 years, 100 years, or mroe. So, we should be ready and consider *all* of the ways alien life can manifest itself.
Anyway, its an interesting and fun read!
Also, if you like considering such things, read my (Steve Bloom) own book, The Physics and Astronomy of Science Fiction, available from the publisher, McFarland Publishing, or any of your favorite online retailers such as Amazon or Barnes and Noble.