THE SOUTHWORTH PLANETARIUM
70 Falmouth Street Portland,Maine 04103
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Founded January 1970
2021-2022: XXVII
"Put your heart, mind and soul into even the smallest acts. That is the secret of success." -Swami Sivananda
THE DAILY ASTRONOMER
Tuesday, October 12, 2021
Heavens Above, Dr. Fermi!
The serene sight of the night sky, entrancing to so many, perturbs those unsettled by the notion that we reside in a lonely galaxy: one devoid of life apart, of course, from life on Earth. For this reason, the star adorned firmament sometimes engenders a morbid fear of abandonment akin to that one experiences when reading existentialist philosophy: we are alone and must find our way without guidance.
Dr. Enrico Fermi (1901-1954), the Nobel-prize winning nuclear physicist, succinctly expressed this concern with a statement now known as "Fermi's paradox." To paraphrase, he asked, "If extraterrestrials exist, where are they?" Many people have inferred from this question the implicit assertion that no aliens exist at all. If they were around, they would have arrived by now. Their absence implies their non-existence.
And to that, we reply, "Heavens above, Dr Fermi!"
We don't know if you were actually suggesting that we Earthlings are the Milky Way's sole inhabitants or were, like so many other preternaturally brainy souls, just delighting in contemplation. However, to our mortal minds, your paradox is nothing of the sort. A paradox refers to the mutual existence of two contradictory situations. However, the galaxy could harbor life or even be choked with so much life that it has to be tucked away in every niche, nook, cranny and bloomer drawer. We could still look upon a tranquil sky each night secure in or frightened by the assurance or uniqueness. They are there. They do exist, but we just haven't found them, yet. Or, perhaps, they haven't found us.
The issue pertains to those two main facets of astronomy: space and time.
First, we assume that any life forms will evolve on a world revolving around a star. Evolution is an expensive business and requires the constant inflow of copious energy sustained over billions of years.* Only stars can produce such energy over protracted time periods.
The space separating stars in this part of the galaxy is vast, about 4 -5 light years on average. Based on the lower value in that range, we calculate that a star has approximately 268 cubic light years to itself! An unfathomable amount of space encloses stars out here along the spiral arms. As we discussed in a previous article about human dominance of the galaxy -or the infeasibility of our dominance-, we humans haven't ventured far from our planet (less than a quarter of a million miles.) Even our most far-flung robotic proves haven't yet strayed too far from home (14.2 billion miles). We will likely require many more generations of advancement before we even think of becoming a star-faring species, if we ever do. Presumably, alien races will have to go through the myriad steps leading up to starships, as well, from the simple cells to the simple scratchings on obelisks to Pythagorean-type math cults and rudimentary rocketry.
So, in answer to the question, "where are they," we offe other possibilities.
THEY HAVE NO MEANS TO TRAVEL OR TO EVEN COMMUNICATE THEIR EXISTENCE TO US
Let's review some history.
1957 - launching of Sputnik, the first artificial satellite.
1896 - the advent of radio technology. Not in widespread use until a few decades later.
3.7 billion years ago - first evidence of life on Earth.
Quite a gap.
If each century were equal to one minute, radio's development would have occurred about 1.3 minutes ago. Earth life would have started about seventy years in the past. Life has been thriving (or struggling) on terra firma for an immensely long time. Only within the last moment have we developed the ability to project radio signals into space or even to venture out into the great black yonder. Our highly attenuated radio bubble extends out only a light century.
How many stars within 100 light years of Earth? Well, based on the local density of 60 stars within 5 parsecs (16.3 light years), our radio bubble is currently enclosing about 13,000 stars: 0.00000325% of all the stars in the Milky Way. That bubble incidentally, is tenuous and therefore exceedingly difficult to detect.
Hello!? Human radio broadcasts are propagating through the Milky Way Galaxy at light speed. Even at that impressive speed, Earth's "radio bubble" encompasses a vanishingly small portion of the Milky Way
The galaxy could very well harbor millions of life-bearing worlds on which even the most advanced life forms haven't yet attained the means by which to emit broadcast signals or to propel themselves into interplanetary or interstellar space. Based on our history, the former development would have to precede the latter. Moreover, any species possessing technology comparable to our own would still be limited in their capacity to interact with other races. Their radio signals -if they even utilize that technology- would be highly attenuated and their robotic probes -if they've even deployed them- wouldn't have progressed far from their home world.
THEY ARE CAPABLE OF TRAVELING INTERSTELLAR DISTANCES AND COMMUNICATION, BUT THEY'RE IGNORING US
Recall the Star Trek phrase, "Non-interference is the prime directive." Perhaps an advanced alien race is monitoring our progress, much to the distress of even their most optimistic scientists. Well aware that their infiltration into our world would profoundly affect it, they have opted to maintain a respectable distance. A species capable of traversing interstellar distances would find the task of concealment quite easy.
THEY'VE BEEN HERE MULTIPLE TIMES, HAVE INTERFERED WITH US AND EVEN LEFT TRACES OF THEMSELVES
Remember Erich Von Däniken's book "Chariots of the Gods?" Ah, we can hear the feet kicking the undersides of desks all over campus. Of course, you remember. Von Däniken published a book in which he asserted that some of humanity's most impressive ancient monuments were either designed or even constructed by ancient astronauts. According to Von Däniken, our remote ancestors lacked the sophistication necessary to construct such objects and so would have required the assistance of smarter beings. Although Von Däniken's propositions have been criticized by a lounge full of academics from archeologists to historians and astronomers, his book started a cottage industry of books asserting that aliens have not only been loitering about throughout history, but that we should ascribe all of our advances to them. Although an intriguing idea, it is predicated on the well known "snobbery of chronology" effect whereby living humans tend to look onto dead ones as primatologists look onto apes. We should resist this tendency. For one thing, the human brain is essentially the same now as it has been for thousands of years. We should have enough faith in and respect for the past generations to recognize that they didn't need the help. Secondly, that snobbery will eventually turn on us. Who knows? Perhaps in two hundred years, all 7.8 billion of us will be known collectively as "those Big Bang imbeciles."
That having been said, it is possible that aliens have lent a helping hand, or all four of them.
It is all hypothetical.
That, Dr. Fermi, is the point.
We are still trapped in the guessing stage. Some of us insist that life abounds in the galaxy because the Universe has proven to be so prodigiously creative. Our galaxy contains hundreds of billions of stars and likely an even greater number of planets!. Thousands of stars are born every second throughout the cosmos. Just by studying one acre of Earth will one notice the stunning diversity of life forms.
Perhaps when we attain a requisite technological level we'll be welcomed into the larger galactic community and discover that our "serene" sky is like Istanbul's grand bazaar, but on a galactic scale. We'll find out..eventually.
*Now for yet another one of our annoying limitations. As we know of only one life-bearing world, we can't draw any comparisons between many life-bearing worlds to determine the average evolutionary time period. According to the fossil record -admittedly incomplete- life started on Earth approximately 3.7 billion years ago. The Universe needed every second of the intervening time period to craft life forms complex enough to start wondering about tricky matters such as evolution and astronomy. We don't know if that time span is typical, lethargic or perhaps even a bit too hasty.
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