The Fermi Paradox

Space Aliens – The Fermi Paradox

Los Alamos Scientific Labs, Los Alamos, New Mexico.  In 1950 four nuclear physicists were walking to lunch discussing, among other things, the likelihood of the existence of extra-terrestrial intelligent
beings.  These four were very intelligent beings themselves:  Edward Teller, soon to be known as the co-inventor of the hydrogen bomb (along with Stan Ulam); Emil Konopinski, who was part of the team that built the first nuclear reactor
under the squash court at the University of Chicago; Herbert York, who would later become the first director of Lawrence Livermore National Labs; and Enrico Fermi, who had already been awarded a Nobel Prize for his work in nuclear physics. 

The men discussed a recent spate of UFO reports and an Alan Dunn cartoon facetiously blaming the disappearance of municipal trashcans on marauding aliens. The
conversation shifted to other subjects, until during lunch Fermi suddenly exclaimed, “Where is everybody?” Teller remembers, “The result of his question was general laughter because of the strange fact that in spite of Fermi’s question coming from the
clear blue, everybody around the table seemed to understand at once that he was talking about extraterrestrial life.”[ Herbert York recalls that Fermi followed up on his comment with a series of calculations on the probability of Earth-like planets, the probability of life, the likely rise and duration of high technology, etc.,
and concluded that we ought to have been visited long ago and many times over.

• There are billions of stars in the galaxy that are similar to the Sun, many of which are billions of years older than Earth.
• With high probability,
  some of these stars will have Earth-like planets, and if the Earth is typical, some might develop intelligent life.
• Some
  of these civilizations might develop interstellar travel, a step the Earth is investigating now.

Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in a few million years.

So the above arguments support the thesis that there should be space aliens among
us – but there aren’t.  That is the paradox:

The Fermi paradox
is a conflict between arguments of scale and probability that seem to
favor intelligent life being common in the universe, and a total lack of evidence of intelligent life having ever arisen anywhere other than on the Earth.

The first aspect of the Fermi paradox is a function of the scale or the large numbers involved: there are an estimated 200–400 billion stars in the Milky Way (2–4 × 1011)
and 70 sextillion (7×1022) in the observable universe.  Even if intelligent life occurs
on only a minuscule percentage of planets around these stars, there might still be a great number of extant civilizations, and if the percentage were high enough it would produce a significant number of extant civilizations in the Milky Way. This assumes the
mediocrity principle, by which the Earth is a typical planet.

The second aspect of the Fermi paradox is the argument of probability: given intelligent life’s ability to overcome scarcity, and its tendency to colonize new habitats,
it seems possible that at least some civilizations would be technologically advanced, seek out new resources in space, and colonize their own star system and, subsequently,
surrounding star systems.  Since there is no significant evidence on Earth, or elsewhere in the known universe of other intelligent life after 13.8 billion years of the universe’s history, there is a conflict requiring a resolution.
 Some examples of possible resolutions are that intelligent life is rarer than we think, that our assumptions about the general development or behavior of intelligent species are flawed, or, more radically, that our current scientific understanding
of the nature of the universe itself is quite incomplete.

The Fermi paradox can be asked in two ways. The first is, “Why are no aliens or their artifacts found here on Earth, or in the Solar System?” If interstellar travel is possible, even the “slow” kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize
the galaxy. This is relatively brief on a geological scale, let alone a cosmological
one. Since there are many stars older than the Sun, and since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all
alien civilizations, large-scale exploration of the galaxy could be possible by probes. These might leave detectable artifacts in the Solar System, such as old
probes or evidence of mining activity, but none of these have been observed.

The second form of the question is “Why do we see no signs of intelligence elsewhere in the universe?” This version does not assume interstellar travel,
but includes other galaxies as well. For distant galaxies, travel times may well explain the lack of alien visits to Earth, but a sufficiently advanced civilization could potentially be observable over a significant fraction of the size of the observable universe.  Even if such civilizations are rare, the scale argument indicates they should exist somewhere at
some point during the history of the universe, and since they could be detected from far away over a considerable period of time, many more potential sites for their origin are within range of our observation.

 What are the counter arguments to the logic that there should be extraterrestrial beings here?  There are many, but none are provable.

Extraterrestrial
life is rare or non-existent, the Rare Earth hypothesis

Those who think that intelligent extraterrestrial life is (nearly) impossible argue that the conditions needed for the evolution of life—or at least the evolution of biological complexity—are rare or even unique to Earth. Under this assumption, called the rare Earth hypothesis, a rejection of the mediocrity principle, complex multicellular
life is regarded as exceedingly unusual.

The Rare Earth hypothesis argues that the evolution of biological complexity requires a host of fortuitous circumstances, such as a galactic habitable zone, a central star and planetary system having the requisite character, the circumstellar habitable zone, a right sized terrestrial
planet, the advantage of a giant guardian like Jupiter and a large natural satellite, conditions needed to ensure the planet has a magnetosphere and plate tectonics, the chemistry of the lithosphere, atmosphere, and oceans,
the role of “evolutionary pumps” such as massive glaciation and rare bolide impacts, and whatever
led to the appearance of the eukaryotecell, sexual reproduction and the Cambrian explosion.

No other intelligent species have arisen

It is possible that even if complex life is common, intelligence (and consequently civilizations) is not. While there are remote sensing techniques that could perhaps detect life-bearing planets without
relying on the signs of technology, none of them has any ability to tell if any detected life is intelligent. This is sometimes referred to as the “algae vs. alumnae” problem.

Intelligent alien species lack advanced technology

It may be that while alien species with intelligence exist, they are primitive or have not reached the
level of technological advancement necessary to communicate. Along with non-intelligent life, such civilizations would be also very difficult for us to detect. To skeptics, the fact that in the history of life on the Earth only one species has developed a
civilization to the point of being capable of spaceflight and radio technology, lends more credence to the idea that technologically advanced civilizations are rare in the universe.

It is the
nature of intelligent life to destroy itself

This is the argument that technological civilizations may usually or invariably destroy themselves before or shortly after developing radio
or spaceflight technology. Possible means of annihilation are many, including war, accidental environmental contamination or damage, resource depletion, climate change, or poorly designed artificial intelligence. This general theme is explored both in fiction and in scientific hypothesizing. In 1966, Sagan
and Shklovskii speculated that technological
civilizations will either tend to destroy themselves within a century of developing interstellar communicative capability or master their self-destructive tendencies and survive for billion-year timescales. Self-annihilation may also be viewed in terms of
thermodynamics: insofar as life is an ordered system that can sustain itself against the tendency to disorder, the “external transmission” or interstellar communicative phase may be the point at which the system becomes unstable and self-destructs.

It is the nature of intelligent life to destroy others

Another hypothesis is that
an intelligent species beyond a certain point of technological capability will destroy other intelligent species as they appear. The idea that something, or someone, might be destroying intelligent life in the universe has been explored in the scientific literature. A species
might undertake such extermination out of expansionist motives, paranoia, or aggression. In 1981, cosmologist Edward Harrison argued that such behavior would be an act of prudence: an intelligent species that has overcome its own self-destructive tendencies might view any other species
bent on galactic expansion as a threat. It has also been suggested that a successful alien species would be a superpredator, as are humans.

Periodic extinction by natural events

New life might commonly die out due to runaway heating or cooling on their fledgling planets. On Earth, there have been numerous major extinction events that destroyed the majority of complex species alive at the time; the extinction of the dinosaurs is the best known example. These are thought to have been caused by events such as impact from a large meteorite,
massive volcanic eruptions, or astronomical events such as gamma-ray bursts. It may be the case that such extinction events are common throughout the universe and periodically destroy intelligent life, or at least its civilizations, before the species is able to develop the technology to communicate with
other species.

It is too expensive to spread physically throughout the galaxy

Many speculations about the ability of an alien culture to colonize other star systems are based on the idea that interstellar travel is technologically feasible. While the current understanding of physics rules out the possibility of faster-than-light travel, it appears that there are no major theoretical
barriers to the construction of “slow” interstellar ships, even though the engineering required is considerably beyond our present capabilities.

It is possible, however, that present scientific
knowledge cannot properly gauge the feasibility and costs of such interstellar colonization. Theoretical barriers may not yet be understood, and the cost of materials and energy for such ventures may be so high as to make it unlikely that any civilization
could afford to attempt it. Even if interstellar travel and colonization are possible, they may be difficult, leading to a colonization model based on percolation theory. Colonization efforts may not occur as an unstoppable rush, but rather as an uneven tendency to “percolate” outwards,
within an eventual slowing and termination of the effort given the enormous costs involved and the expectation that colonies will inevitably develop a culture and civilization of their own. Colonization may thus occur in “clusters,” with large areas remaining
uncolonized at any one time.

If exploration, or backup from a home system disaster, is the primary motive for expansion, then it is possible that mind uploading and similar technologies may reduce the desire to colonize by replacing physical travel with much less-expensive communication.
Therefore the first civilization may have physically explored or colonized the galaxy, but subsequent civilizations find it cheaper, faster, and easier to travel by contacting existing civilizations rather than physically exploring or traveling themselves.
This leads to little or no physical travel at the current epoch, and only directed communications, which are hard to see except to the intended receiver.

Human beings have not existed long enough

Humanity’s ability to detect intelligent extraterrestrial life has existed for only a very brief period—from 1937 onwards,
if the invention of the radio telescope
is taken as the dividing line—and Homo sapiens is a geologically recent species. The whole period of modern human existence to date is a very brief period on a cosmological scale, and radio transmissions have only been propagated since 1895. Thus, it remains possible that human beings have neither
existed long enough nor made themselves sufficiently detectable to be found by extraterrestrial intelligence.

We are not listening properly

There are some assumptions that underlie the SETI programs that may cause searchers to miss signals that are present. Extraterrestrials might, for example, transmit signals that have a very high or low data rate, or employ unconventional (in our terms) frequencies, which would make them hard to distinguish from
background noise. Signals might be sent from non-main sequence star systems that we search with lower priority; current programs assume that most alien life will be orbiting Sun-like stars.

The greatest challenge is the sheer size of the radio search needed to look for signals
(effectively spanning the entire visible universe), the limited amount of resources committed to SETI, and the sensitivity of modern instruments. SETI estimates, for instance, that with a radio telescope as sensitive as the Arecibo Observatory, Earth’s television and radio broadcasts would
only be detectable at distances up to 0.3 light-years, less than 1/10 the distance to the nearest star. A signal is much easier to detect if the signal energy is limited to either a narrow range of frequencies, or directed at a specific part of the sky. Such signals could be detected at ranges of hundreds to tens of
thousands of light-years distance.  However, this means that detectors must be listening to an appropriate range of
frequencies, and be in that region of space to which the beam is being sent. Many SETI searches assume that extraterrestrial civilizations will be broadcasting a deliberate signal, like the Arecibo message, in order to be found.

Thus, to detect alien civilizations through their radio emissions, Earth observers either need more sensitive instruments or must hope for fortunate circumstances: that the broadband radio emissions of alien radio technology are
much stronger than our own; that one of SETI’s programs is listening to the correct frequencies from the right regions of space; or that aliens are deliberately sending focused transmissions in our general direction.

Civilizations broadcast detectable radio signals only for a brief period of time

It may be that alien civilizations
are detectable through their radio emissions for only a short time, reducing the likelihood of spotting them. The usual assumption is that civilizations outgrow radio through technological advancement. However, even if radio is not used for communication,
it may be used for other purposes such as power transmission from solar power satellites. Such uses may remain visible even after broadcast emission are replaced by less observable technology.

More
hypothetically, advanced alien civilizations may evolve beyond broadcasting at all in the electromagnetic spectrum and communicate by technologies not developed or used by mankind. Some scientists have hypothesized that advanced civilizations may send neutrino signals. If such signals exist, they could be detectable
by neutrino detectors that are
now under construction for other goals.

They are too alien

Another possibility
is that human theoreticians have underestimated how much alien life might differ from that on Earth. Aliens may be psychologically unwilling to attempt to communicate with human beings. Perhaps human mathematics is parochial to Earth and not shared by other life, though others argue this can only apply to abstract math since the math
associated with physics must be similar (in results, if not in methods).

Physiology might also cause a communication barrier. Carl Sagan speculated that an alien species might have a thought
process orders of magnitude slower (or faster) than ours. A message broadcast by that species might well seem like random background noise to us, and therefore go undetected.

The bulk of
this article was taken from the Wilipedia article on the Fermi Paradox.  https://en.wikipedia.org/wiki/Fermi_paradox.  There are additional arguments for why we have not detected space aliens in that article, along with links to various articles on the people, the Manhattan Project, and how to build a H-Bomb, this is a very popular subject in North Korea. 

The ant hill hypothesis

One argument that I have thought of is that we are just not advanced enough to see, or detect the aliens even though they are here and watching, and maybe manipulating our lives.  I call this the ant hill theory.  We
see ants, we often manipulate or disturb their lives, but they do not know we are here and doing the manipulating.  They
are just not advanced enough to detect us; we are the ants; the space aliens are the people. 

Personally,
I think that we are better off without aliens.  Any beings that are advanced enough to make it to earth will be advanced
enough to wipe us out if they wanted to, and they might.  (See It is the nature of intelligent life to destroy others, above). 
In 1977 the USA launched two Voyager space probes.  Both
of these probes did scientific work as they passed our solar system’s outer planets, and are now both outside of the limits of our solar system and headed to interstellar space. 
They both contain a map of our sun and our planet so that any civilization that intercepts them can find us.  This is in my opinion dumb.  Not just dumb, it is potentially suicidal.  We should not invite an invading species to our front door. 
What could possibly go wrong?

Anyone who got this far reading might be interested in looking at my article No Name Place.  It concerns the names of our planet, sun, solar system, etc. 
http://www.afewthingsilearned.com/408736970

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