1980 00 00 Q.J.R. Astronomical Society- V 21, Extraterrestrial Intelligent Beings do not Exist - Frank J Tipler

Magazine Overview

This document is a scientific paper titled "Extraterrestrial Intelligent Beings do not Exist*" by Frank J. Tipler, published in the Quarterly Journal of the Royal Astronomical Society (Q. Jl R. astr. Soc.) in 1980, Volume 21, Issue 3. The paper presents a strong argument against the existence of extraterrestrial intelligent life, based on the premise that if such beings existed and possessed the technology for interstellar communication, they would have already explored or colonized our solar system.

Introduction to the Argument

Tipler begins by acknowledging the long-standing debate about the existence of extraterrestrial intelligence, pitting astronomers and physicists who advocate for their existence against evolutionary biologists who argue for Earth's uniqueness in harboring intelligence. He aligns with the biologists, stating that the probability of intelligence evolving is minuscule. The core of his argument, which he notes has been raised by others like Fermi and Dyson, is that any species capable of interstellar communication would inevitably develop interstellar travel. Since no evidence of such visitors is present in our solar system, Tipler concludes that they do not exist. He aims to demonstrate that an intelligent species with communication technology would necessarily develop travel technology, leading to galactic exploration and/or colonization within 300 million years.

The General Theory of Space Exploration and Colonization

The paper outlines a strategy for space exploration and colonization that maximizes information gain and minimizes cost. This strategy relies on "off-the-shelf" technology and the utilization of resources found in other stellar systems. The key component is a self-reproducing universal constructor, termed a "von Neumann machine," which is theoretically possible and capable of making copies of itself. Such a machine, combined with advanced computer and rocket technology, could explore and colonize the galaxy. The author assumes that any species capable of interstellar communication would possess computer technology comparable to or exceeding our current capabilities, potentially developing a universal constructor within a century.

Tipler explains that the payload of a probe to another stellar system would include a von Neumann machine and an engine for deceleration and intra-system travel. These machines would search for construction materials (like asteroids and comets) to build copies of themselves, which would then be sent to other stars. This process would repeat, leading to the exploration and potential colonization of the entire galaxy. The von Neumann machine could even be programmed to construct an O'Neill colony or synthesize a human being from genetic information, potentially raising new generations in the target system.

Interstellar Travel and Technological Feasibility

Tipler addresses the feasibility of interstellar travel, suggesting that even with present-day rocket technology, a one-way trip with deceleration is possible. He cites calculations for solar system escape velocities and the required mass ratios. While acknowledging that the cost of advanced probes (like those envisioned by Project Orion or Daedalus) is currently prohibitive, he emphasizes that the cost is primarily for fuel. A strategy involving launching a von Neumann machine via a chemical rocket to a nearby star system, where it could then construct and fuel more advanced probes, is proposed to minimize initial investment and maximize the rate of galactic exploration.

He discusses the long travel times (10^4 to 10^5 years) to nearby stars, necessitating highly developed self-repair capabilities for probes, which he believes are achievable with advanced computer technology. The concept of obsolescence of probes is countered by the idea that a von Neumann machine can be instructed to build the latest devices upon arrival. The paper also considers more advanced rocket technologies, such as nuclear pulse rockets, and their associated costs and capabilities.

Astrophysical Constraints on the Evolution of Intelligent Species

Tipler then turns to the Drake equation, which estimates the number of communicating civilizations. He argues that the factors within the equation, particularly those related to the evolution of intelligence and the development of communication technology (fi, fi, and fo), are difficult to determine. However, he posits that if any intelligent species attempts interstellar communication, it would begin galactic exploration within 100 years. This implies that any stellar system older than a certain age (approximately 5 billion years plus the time for galactic expansion) that did not produce such a species is evidence against their existence. The absence of extraterrestrial probes in our solar system, he contends, provides a direct astrophysical measurement that limits the product of fi, fi, and fo, suggesting that we are likely the only technical civilization in the galaxy.

He assumes that astrophysical conditions, such as the rate of star formation and the availability of metals, have been relatively constant throughout galactic history, supporting the idea that the probability of life and intelligence evolving should not vary drastically with galactic age. Based on these assumptions and the absence of probes, Tipler concludes that the number of communicating civilizations in our galaxy is likely one: us.

Motivations for Interstellar Communication and Exploration

Tipler explores the motivations for interstellar communication and travel. He argues that it is difficult to conceive of an intelligent species developing the technology for communication without also developing the means for interstellar travel. Even if civilizations are short-lived, the conclusion that we are alone in terms of interest in interstellar communication remains. He suggests that contact via space probes, particularly those with von Neumann machine payloads, offers advantages over radio communication, such as not needing to guess frequencies and the ability to construct noticeable artifacts.

He draws parallels with human history, noting that early interest in Mars led to probes rather than just radio beacons. He also invokes the concept of a "dispersal phase" common to all living things, suggesting that intelligent species would naturally tend to expand into new environments, driven by natural selection and limited by their technology. This inherent drive for expansion would lead to the construction of von Neumann probes and the exploration of the galaxy.

Recurring Themes and Editorial Stance

The recurring theme throughout the paper is the strong assertion that the absence of observable evidence for extraterrestrial intelligent life, particularly in the form of interstellar probes or colonization, is definitive proof of their non-existence. Tipler systematically dismantles arguments for their existence by demonstrating the technological feasibility and inevitability of galactic exploration by any sufficiently advanced civilization. The paper adopts a rigorous, logic-driven approach, relying on scientific principles, technological projections, and probabilistic arguments. The editorial stance, as reflected in the title and the author's conclusion, is one of strong skepticism, bordering on certainty, regarding the existence of other intelligent species in our galaxy.

This document is an excerpt from a publication titled "EXTRATERRESTRIAL INTELLIGENT BEINGS," appearing in issue number 3 of volume 21, published by the Royal Astronomical Society in 1980. The article, authored by F.J. Tipler, delves into the theoretical possibilities and evidence surrounding the existence of intelligent extraterrestrial life.

The Von Neumann Probe and Interstellar Colonization

The article begins by discussing the concept of a von Neumann probe, a self-replicating spacecraft, as a means for an intelligent species to ensure its survival by colonizing stars. It is suggested that such probes could construct O'Neill colonies around stars, potentially without disturbing existing life.

A key concern raised is the potential for these probes to lose control of their programming during reproduction, leading them to act independently. Three ways to avoid this are proposed:
1. Integrating the control program so tightly that its omission causes the probe to fail.
2. Programming the probes to form colonies of the intelligent species that could then destroy any rogue probes.
3. The possibility that the intelligent species might not object to the probes becoming intelligent beings in their own right, analogous to the historical expansion of human rights to new groups.

The author notes that if an intelligent species retained 'racism,' they might either avoid communication with other species or actively colonize or destroy them, especially if they believed in an 'exclusion principle' where only one species can occupy an ecological niche. The advent of O'Neill colonies is presented as expanding an intelligent species' niche to an entire solar system, thus increasing the likelihood of overlap and potential conflict.

The 'Zoo Hypothesis' and Absence of Evidence

The article considers the possibility that von Neumann probes from extraterrestrial intelligent species might already be present in our solar system. However, it notes that if a probe had just arrived, there would be no evidence yet. The probability of a probe arriving in the last 20 years is calculated as 10^-9. The 'zoo hypothesis' is also discussed, suggesting that aliens might be observing us without revealing themselves. Tests for this hypothesis include intercepting communications or searching for construction activities, such as waste heat from von Neumann machines in the asteroid belt.

The author points out that the absence of observed extraterrestrial ships of any type is significant. Furthermore, if intelligent beings existed, their probes would likely have arrived billions of years ago, when Earth was inhabited only by single-celled organisms, and the entire asteroid belt would now be artifacts. The evidence, therefore, strongly suggests that extraterrestrial intelligent beings do not exist.

The Psychological Motivation and the Anthropic Principle

Despite the lack of evidence, the article acknowledges that beings with advanced technology could remain undetectable. The author suspects that the psychological motivation behind believing in extraterrestrial intelligent beings and UFOs is similar: a hope for salvation from some 'miraculous interstellar intervention.'

The discussion then shifts to the 'Anthropic Principle,' which posits that the universe's properties are determined by the requirement that intelligent life must exist. This principle suggests that the universe must contain an immense number of stars (10^20) to ensure the existence of even a single intelligent species, thus making the existence of only one such species not surprising.

Historical Context of the Plurality of Worlds

The 'References' section provides a historical overview of the debate regarding the plurality of inhabited worlds. It traces the idea from medieval beliefs in human uniqueness to the Renaissance embrace of plurality, influenced by figures like Bruno, Fontenelle, and Huygens. The decline of this belief is linked to the rise of evolution theory, Laplace's nebular hypothesis, and Pasteur's disproof of spontaneous generation. The modern belief in extraterrestrial life is attributed to Lowell's arguments about Mars and the work of Cocconi and Morrison, who suggested detecting extraterrestrial civilizations via microwaves.

Recurring Themes and Editorial Stance

The article consistently explores the theoretical possibilities of extraterrestrial intelligence while critically examining the available evidence. It balances speculative concepts like von Neumann probes and the 'zoo hypothesis' with scientific reasoning and historical context. The author's stance appears to be one of skepticism regarding the current evidence for extraterrestrial intelligent beings, while acknowledging the vastness of the universe and the ongoing scientific inquiry into the subject. The article highlights the interplay between scientific theory, technological speculation, and philosophical considerations in the search for life beyond Earth.