Rare Earth hypothesis – Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward,

The hypothesis argues that complex extraterrestrial life requires an Earth-like planet with similar circumstance and that few if any such planets exist.
The rare earth hypothesis is the contrary of the widely accepted principle of mediocrity (also called the Copernican principle), advocated by Carl Sagan and Frank Drake, among others. The principle of mediocrity concludes that the Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Hence it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the solar system, and our region of the Milky Way are very rare.

-A planet that is too small cannot hold much of an atmosphere. Hence the surface temperature becomes more variable and the average temperature drops. Substantial and long-lasting oceans become impossible. A small planet will also tend to have a rough surface, with large mountains and deep canyons. The core will cool faster, and plate tectonics will either not last as long as they would on a larger planet or may not occur at all.

-The Moon is unusual because the other rocky planets in the Solar System either have no satellites (Mercury and Venus), or have tiny satellites that are probably captured asteroids (Mars).

Search for extraterrestrial intelligence (SETI)

The search for extraterrestrial intelligence (SETI) is the collective name for a number of activities people undertake to search for intelligent extraterrestrial life. Some of the most well known projects are run by Harvard University, the University of California, Berkeley and the SETI Institute. SETI projects use scientific methods to search for intelligent life on other planets. For example, electromagnetic radiation is monitored for signs of transmissions from civilizations on other worlds. The United States government contributed to early SETI projects, but recent work has been primarily funded by private sources.

Bracewell probe

A Bracewell probe is a hypothetical concept for an autonomous interstellar space probe dispatched for the express purpose of communication with one or more alien civilizations. It was proposed by Ronald N. Bracewell in a 1960 paper, as an alternative to interstellar radio communication between widely separated civilizations.

A Bracewell probe would be constructed as an autonomous robotic interstellar space probe with a high level of artificial intelligence, and all relevant information that its home civilization might wish to communicate to another culture. It would seek out technological civilizations–or alternatively monitor worlds where there is a likelihood of technological civilizations arising–and communicate over “short” distances (compared to the interstellar distances between inhabited worlds) once it discovered a civilization that meets its contact criteria. It would make its presence known, carry out a dialogue with the contacted culture, and presumably communicate the results of its encounter to its place of origin. In essence, such probes would act as an autonomous local representative of their home civilization and would act as the point of contact between the cultures.

Since a Bracewell probe can communicate much faster, over shorter distances, and over large spans of time, it can communicate with alien cultures more efficiently than radio message exchange might. The disadvantage to this approach is that such probes cannot communicate anything not in their data storage, nor can their contact criteria or policies for communication be quickly updated by their “base of operations”.

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 space flight technology. Possible means of annihilation include nuclear war, biological warfare or accidental contamination, climate change, nanotechnological catastrophe, ill-advised physics experiments,[Note 4] a badly programmed super-intelligence, or a Malthusian catastrophe after the deterioration of a planet’s ecosphere. This general theme is explored both in fiction and in mainstream scientific theorizing.[49] Indeed, there are probabilistic arguments which suggest that human extinction may occur sooner rather than later. In 1966 Sagan and Shklovskii suggested 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

From a Darwinian perspective, self-destruction would be an ironic outcome of evolutionary success. The evolutionary psychology that developed during the competition for scarce resources over the course of human evolution has left the species subject to aggressive, instinctual drives. These compel humanity to consume resources, extend longevity, and to reproduce—in part, the very motives that led to the development of technological society. It seems likely that intelligent extraterrestrial life would evolve in a similar fashion and thus face the same possibility of self-destruction. And yet, to provide a good answer to Fermi’s Question, self-destruction by technological species would have to be a near universal occurrence.

This argument does not require the civilization to entirely self-destruct, only to become once again non-technological. In other ways it could persist and even thrive according to evolutionary standards, which postulate producing offspring as the sole goal of life—not “progress”, be it in terms of technology or even intelligence.

Iron law of wages

The Iron Law of Wages is a proposed law of economics that asserts that real wages always tend, in the long run, toward the minimum wage necessary to sustain the life of the worker. The theory was first named by Ferdinand Lassalle in the mid-nineteenth century.

The classical economic theory that wages will tend to be at or near subsistence level. Increases above subsistence will result in population growth that produces more workers and a resulting decline in wages. Also called subsistence theory of wages.

Malthusian catastrophe

A Malthusian catastrophe (also known as Malthusian check) was originally foreseen to be a forced return to subsistence-level conditions once population growth had outpaced agricultural production.

O catastrofă malthusiană(numită și coșmarul malthusian, criza malthusiană, dezastrul malthusian sau capcana malthusiană) a fost definită inițial ca fiind condițiile de revenire forțată la un nivel de subzistență ca urmare a creșterii populației în timp ce producția agricolă nu mai este suficientă. Definițiile mai iau în considerare limitele de creștere economică, precum epuizarea petrolului. Bazat pe lucrările de economie politică ale lui Thomas Malthus (1766–1834), teoriile catastrofei malthusiene sunt foarte similare cu legea de fier a salariului. Principala diferență este că teoriile malthusiene prezic ce se va întâmpla peste mai multe generații sau secole, în timp ce legea de fier a salariului prezice ce se va întâmpla peste câțiva ani sau decenii.

Fermi paradox – “Where is everybody?”

The Fermi paradox (or Fermi’s paradox) is the apparent contradiction between high estimates of the probability of the existence of extra-terrestrial civilization and humanity’s lack of contact with, or evidence for, such civilizations. The basic points of the argument, made by physicists Enrico Fermi and Michael H. Hart, are:
• The Sun is a young star. There are billions of stars in the galaxy that are billions of years older;
• Some of these stars likely have Earth-like planets which, if the Earth is typical, may develop intelligent life;
• Presumably some of these civilizations will develop interstellar travel, as Earth seems likely to do;
• At any practical pace of interstellar travel, the galaxy can be completely colonized in just a few tens of millions of years.
According to this line of thinking, the Earth should have already been colonized, or at least visited. But no convincing evidence of this exists. Furthermore, no confirmed signs of intelligence elsewhere have been spotted, either in our galaxy or the more than 80 billion other galaxies of the observable universe. Hence Fermi’s question “Where is everybody?”.

Other common names for the same phenomenon are Fermi’s question (“Where are they?”), the Fermi Problem, the Great Silence,and silentium universi (Latin for “silence of the universe”).

The Fermi paradox is a conflict between an argument of scale and probability and a lack of evidence. A more complete definition could be stated thus:
The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist.However, this hypothesis seems inconsistent with the lack of evidence to support it.

Space probe /vs/ manned spaceflight

A space probe is a scientific space exploration mission in which a spacecraft leaves Earth and explores space. It may approach the Moon; enter interplanetary space; flyby, orbit or land on other planetary bodies; or approach interstellar space. Space probes are a form of robotic spacecraft.

Human spaceflight (or manned spaceflight or crewed spaceflight) is space travel with humans on the spacecraft. When a spacecraft is manned, it can be piloted directly, as opposed to machine or robotic space probes controlled remotely by humans or through automatic methods on board the spacecraft.

Aerial cranes or skycranes


Helicopters used to lift heavy loads are called aerial cranes or skycranes. As aerial cranes, helicopters carry loads connected to long cables or slings in order to place heavy equipment when other methods are not available or economically feasible, or when the job must be accomplished in remote or inaccessible areas, such as the tops of tall buildings or the top of a hill or mountain, far from the nearest road.

Postpartum depression (PPD)

Postpartum depression (PPD), also called postnatal depression, is a type of clinical depression which can affect women, and less frequently men, typically after childbirth. Studies report prevalence rates among women from 5% to 25%, but methodological differences among the studies make the actual prevalence rate unclear. Among men, in particular new fathers, the incidence of postpartum depression has been estimated to be between 1.% and 25.5%.Postpartum depression occurs in women after they have carried a child. Symptoms include sadness, fatigue, changes in sleeping and eating patterns, reduced libido, crying episodes, anxiety, and irritability.