Fine tuning and Fermi’s paradox

A “freakishly” fine-tuned universe

Ever since the time of Copernicus, the overriding worldview of scientific discovery has been that there is nothing special about Earth and humanity: the Earth is not the center of the solar system — we are merely one of several planets orbiting the Sun; the Sun is not the center of the Milky Way — it is merely one of over 100 billion stars in the galaxy; the Milky Way is not the center of the universe — it is merely one of over 100 billion galaxies in the universe; etc. Indeed, this “Copernican principle” has been assumed to apply very generally in all fields of science.

Yet some major cracks have arisen in this edifice in the past few years. Most notably, we appear to reside in a universe that is astoundingly fine-tuned for intelligent life. This counter-intuitive fact was presented and discussed at length in the new book by Australian astronomers Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe: Life in a Finely Tuned Cosmos (see also [Rees2000]). Here is a brief summary of some of these “cosmic coincidences” (see also Fine tuned):

  1. The synthesis of carbon depends sensitively on the value of the strong force.
  2. The existence of both protons and neutrons depends sensitively on the strong and weak forces.
  3. If the electromagnetic force were not roughly 1040 times stronger than gravity, the heavier elements would not form.
  4. If the neutron mass were very slightly less, the universe would be entirely protons.
  5. The cosmic microwave background is just nonuniform enough (one part in 105) to permit galaxies.
  6. The positive and negative contributions to the vacuum energy density cancel to within one part in 10120 (the cosmological constant paradox).
  7. The positive and negative contributions of the Higgs boson mass cancel to one part in 1019 to give the anomalously low value we observe.
  8. In the first few minutes after the big bang, the universe must have been flat to within one part in 1015.
  9. The overall entropy of the universe is “freakishly lower than life requires.”

Fermi’s paradox

In 1950, while having lunch with colleagues Emil Konopinski, Edward Teller and Herbert York, physicist Enrico Fermi suddenly blurted out, “Where is everybody?” Behind Fermi’s question was this line of reasoning: (a) There are likely numerous other technological civilizations in the Milky Way galaxy; (b) if a society is less advanced than us by even a few decades, they would not be technological, so any other technological civilization is, almost certainly, many thousands or millions of years more advanced; (d) within a few million years after becoming technological (an eye-blink in cosmic time), a society could have explored and/or colonized most if not all of the Milky Way; (e) so why don’t we see evidence of the existence of even a single extraterrestrial civilization?

Proposed solutions to Fermi’s paradox

Numerous scientists have examined Fermi’s paradox since it was first proposed, and have proposed solutions. Below is a brief listing of some of the proposed solutions, and common rejoinders [Webb2002, pg. 27-231]:

  1. They exist, but are under strict orders not to communicate with a civilization such as Earth (the “zookeeper” solution). Rejoinder: In numerous vast, diverse ET civilizations (or even in just one ET civilization), each spanning multiple planets or stars, and each consisting of millions of individuals, it is hardly credible that a galactic society could impose a global ban on communication to Earth that is absolutely 100% effective. Note that once a signal has been broadcast and is on its way to Earth, there is no way to call it back, within known laws of physics. And for a civilization that is thousands or millions of years more advanced than us, such communication would be vanishingly cheap.
  2. They exist, but have lost interest in scientific research, exploration and expansion (the “beach bum” solution). Rejoinder: Darwinian evolution strongly favors organisms that think, explore and expand. Thus it is hardly credible that every individual in every ET civilization has lost interest in scientific research, exploration and expansion, or that a global ban on such activities is absolutely 100% effective. What’s more, any ET society’s long-term existence crucially hinges on having an in-depth scientific understanding of all potential perils in its cosmic environment, including asteroids, meteorites, solar flares, supernovas, gamma ray bursts, neutron star mergers, potentially dangerous biological systems and potentially hostile neighbors.
  3. They exist, but have no interest in a primitive, backward society such as ours; to them, we are as ants (the “humans are ants” solution). Rejoinder: Perhaps 99.99% of an ET society is not interested in primitive societies such as ours. But, as before, it is hardly credible that every individual in every ET civilization has no interest. In our society, perhaps 99.99% of the public has little or no interest in ants. But many thousands do. There is even a full-fledged scientific field (myrmecology) to study ants, and researchers have meticulously catalogued and studied every known species.
  4. They exist, but have progressed to more sophisticated communication technologies (the “advanced communication” solution). Rejoinder: This does not apply to signals that are specifically targeted to societies such as ours, in a form (optical, microwaves) that could be easily recognized by a newly technological society. Again, it is hardly credible that a galactic society could enforce a global ban, over a vast array of inhabited planets, each with millions of individuals, on communication targeted to emerging technological civilizations, that is absolutely 100% effective. As noted before, once a signal is on its way to Earth, it cannot be called back, within known laws of physics. Similar diversity arguments defeat a broad range of other proposed solutions (see below).
  5. They exist, but are not aware of our existence yet — our first TV signals have only passed 80 light years’ distance (the “no evidence of humans” solution) [Reynolds]. Rejoinder: Ample evidence of an emerging technological civilization on Earth has been on display for much longer: (a) our atmosphere has contained methane, oxygen and other chemical signs of life for at least three billion years; (b) images of Earth would have shown dinosaurs and countless other large species for at least 300 million years; (c) images of Earth would have shown bipedal hominins for at least 5 million years, and humans for at least 200,000 years; (d) images of Earth would have shown large human structures (Mesopotamia, Egypt, China, Rome) for at least 5,000 years; (e) urban lights have been on display for at least 2,000 years, particularly in the past 200 years; and (f) atmospheric carbon dioxide has been on the rise for 200 years.
  6. They exist, but travel and communication are too difficult (the “technological” solution). Rejoinder: Recent dramatic and largely unanticipated developments in technology in the past few years have all but destroyed this solution: new energy sources, including various forms of fusion [Bailey2015]; new propulsion systems [Ion2016, Foster2004, Slough2013]; new space exploration vehicles [Drake2017]; fleets of nanocraft to visit nearby stars such as Alpha Centauri [Billings2016]; supercomputers (currently run at 1017 flop/s); quantum computing; artificial intelligence [AlphaGo2017,Parloff2016]; robotics; 3-D printing and nanotechnology; exoplanet search and imaging technology; gravitational lenses (see below); and von Neumann probes (see below). If we are on the verge of deploying such technologies today, what is stopping societies and even individuals that are thousands or millions of years more advanced than us?
  7. Civilizations like us invariably self-destruct before becoming a space-faring society (the “self-destruct” solution). In 200 years of technological adolescence, we have not yet destroyed ourselves through a nuclear, environmental or biological catastrophe. Further, we have developed sophisticated supercomputer simulations to foresee and control future perils. Thus it is hardly credible that societies such as ours invariably self-destruct before they become space-faring society, without any exceptions whatsoever. In any event, within a few years human civilization will spread to the Moon, Mars and elsewhere, and then its long-term survival will be largely impervious to calamities on the home planet. As before, galloping technology is destroying this solution to Fermi’s paradox.
  8. Earth is a unique planet with characteristics fostering a long-lived biological regime leading to intelligent life (the “rare earth” solution) [Ward2000]. Rejoinder: Perhaps, although many recent discoveries point in the opposite direction: the universe contains over 100 billion galaxies; the Milky Way contains over 100 billion stars; thousands of exoplanets have been found (more than 40 in the habitable zone) (see below); recent work in biogenesis indicates that the origin of life was not a particularly unlikely event (also indicated by recent fossil finds, which show life arose almost immediately after the formation of Earth, over 3.8 billion years ago) — see Origin.

  9. WE ARE ALONE, within the Milky Way galaxy if not beyond (the “solitary” solution). Rejoinder: It hardly seems credible that we are unique even in the Milky Way (with over 100 billion stars and planets), much less the entire universe (with over 100 billion galaxies). This solution may be consistent with Occam’s razor, but it is an extreme violation of the “Copernican principle,” namely the hypothesis that there is nothing special about Earth or humanity. Has the Copernican principle been completely overturned? Many recoil at this solution (including the author), but what is the alternative?

Numerous other proposed solutions and rejoinders are given at [Webb2002]. A more recent review of these issues is given in [Gribbin2011].

Diversity and Fermi’s paradox

As mentioned above, diversity arguments defeat a wide range of proposed solutions. Consider:

  • Darwinian evolution is the only known or hypothesized mechanism whereby high-information organisms and species (carbon-based or not) can form.
  • Diversity is a fundamental, inescapable law of Darwinian evolution.
  • Diversity is also a law of economics, political science, organizational behavior, and even physics (quantum superposition, sum over histories, chaos, anisotropy in the cosmic microwave background, etc.).
  • Highly conformist species, societies and organizations inevitably fail.
  • All great figures of history were nonconformists: Albert Einstein, Martin Luther King, Susan B. Anthony, Nelson Mandela, Steve Jobs. Jobs’ motto was “think different.”

In a vast, diverse society, there will be exceptions to any rule. Thus claims that “all ET are like X” have no credibility, no matter what “X” is. It is ironic that while most scientists would reject stereotypes of religious, ethnic or national groups, some seem willing to hypothesize sweeping, ironclad stereotypes for ET societies.

Exploration of the Milky Way

As mentioned above in item 6, the “technological” solution argues that exploration and communication are simply too difficult. However, in addition to the developments listed above, a distant society could deploy “von Neumann probes,” self-replicating robotic spacecraft that travel to a star system, send video and scientific data back to the home planet, and then manufacture several copies of themselves, which are launched to even more distant systems. One recent analysis of the “slingshot” scenario found that 99% of all star systems in the Milky Way could be explored in only about five million years, which, is an eyeblink in the multi-billion-year age of the Milky Way [Nicholson2013].

“Exploring” the Milky Way telescopically is even easier, by means of a “gravitational lens,” namely using the Sun as a “lens” (according to general relativity). Magnifications of up to 1015 could be attained. With such a facility, which is nearly feasible at the present time, we could obtain rather high-resolution images of distant planets, and even listen in to their microwave transmissions (or other forms of electromagnetic communication). What’s more we could also send messages to them using the same facility [Landis2016].

As mentioned above, if we are on the verge of deploying such technologies today, what is stopping societies and even individuals that are thousands or millions of years more advanced than us? Are other civilizations using gravitational lenses to see close-up images of Earth? Or even to send messages to Earth? Why not?

The grim mathematics of Fermi’s paradox

Let p be the probability that an individual on a given planet in a given year launches an interstellar exploration, m be the number of individuals on a typical planet, n be the number of planets, and t be the number of years. Then the probability P that a civilization has explored the Milky Way can be estimated as P = 1 – (1 – p)m n t. Conservative estimates for the Milky Way are m > 109, n > 1011 and t > 5 x 109. For the universe as a whole, n > 1022 and t > 1010.

In other words, if the probability of the rise of a space-faring civilization anywhere is even microscopically nonzero (given the instance of human civilization), then after billions of years, on many billions of planets, with billions of individuals, ET should be everywhere. Where is everybody?

Davies and Gribbin on Fermi’s paradox

With every new research finding of extrasolar planets, potential life-friendly environments within the solar system, and, especially, with every new advance of human technology, the mystery of Fermi’s paradox deepens. Indeed, “Where is everybody?” has emerged as one of the most significant scientific and philosophical questions of our time.

Paul Davies, a prominent British-American physicist, concludes his latest book on the topic by stating his own assessment [Davies2010, pg. 207-208]: “[M]y answer is that we are probably the only intelligent beings in the observable universe and I would not be very surprised if the solar system contains the only life in the observable universe.”

John Gribbin, a prominent British astrophysicist, concludes his recent book on the topic in these uncompromising terms [Gribbin2011, pg. 205]: “They are not here, because they do not exist. The reasons why we are here form a chain so improbable that the chance of any other technological civilization existing in the Milky Way Galaxy at the present time is vanishingly small. We are alone, and we had better get used to it.”

Fine tuning and Fermi’s paradox

If we are truly alone in the Milky Way or beyond, this greatly magnifies the paradox of universal fine tuning. Not only do we reside in an incredibly fortunate universe, but we occupy an incredibly unique time and place within that universe. Even if we are “only” extremely rare in the universe, this is a most important finding, with truly cosmic implications.

Was the universe made for us? Or is our understanding of the laws of physics fundamentally in error?

Either way, human existence is far more significant than anyone could have imagined even a few years ago.

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