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Aliens & UFO's

ET’s and a new history of early civilised man

By Leonard Farra

In the 4 March 2014 online edition of Huffington Post, Astronaut Leroy Chiao was reported as posing this question:
‘If there is life out there…….why don’t they just come and show themselves’.


Updated Answer

Something extraordinary happened, on this planet, several thousand years ago. Fully developed civilisations suddenly sprang up in the Old and New Worlds and whole tribes were  on the move settling into new lands. Major changes in human life also occurred in Ancient Sumeria whose scribes claimed that their people were survivors of ‘The Flood’. All these things happened in the era around 5,000 years ago at which time there is evidence of flooding and sudden climatic change. (1)

According to Sumerian and Babylonian texts, ‘The Flood’ was caused by the Annunaki, who appear to be aliens, when they destroyed the evil people of the previous age. (2) Their Earth visit was a major influence on traditions, religions, and legends, in the Ancient Middle East, Egypt, Greece, Scandinavia, countries in Asia, parts of Africa, among Native Americans and also on remote Easter Island in the Pacific. (3) Although they were not named, by the Ancient, the Annunaki leaders are identifiable with a group of early gods who were revered throughout the world. The Maya and, possibly, Mexico’s Olmecs, regarded them as creator gods. (4) As Christianity was the religion in Europe, in the Middle Ages, they were now ancestral leaders, or heroes, and this continued right through to present times in popular adventure stories, legends, and famous films. (5)

The E.T’s, who reputedly visited this planet, were not little green men, or the monstrous creatures of science fiction, as they resembled tall white men and they wore white robes.(6) As I suggested, in an earlier article, their dazzling appearance might be the reason why priests, in many early religions, wore white robes in the service of their gods. In religious art, angels are depicted in white robes and , in the Book of Revelation, white garmented beings described as elders, are seated around a throne in Heaven when angels send down destruction on Earth (Rev.4- ).


Although this New Testament story is a prophecy of what will happen in the future , it was adopted, by the Church, from Middle Eastern legends, dating back 3,000 years, about catastrophic events which reputedly occurred in the era of the visit of the star-people.(7)
One of the E.T leaders was reputed  to have been the great civiliser of man. The Sumerians called him Ea and the Egyptians knew him as Osiris. Aztecs and Maya called him Feathered Serpent, (Quetzalcoatl ), the Incas -Viracocha and some North American Native tribes called him Michabo-the Great White One. He was also known to the Aborigines and their tribes in Eastern Australia called him Baime. When the Spaniards arrived in the New World, 500 years ago, the Aztecs, and Incas, were convinced that the white god, and his companions, had returned and, after first being mistaken for the former, Capt Cook was killed in Hawaii.

   Few people place any significance on the custom of royalty, and leaders, of carrying ceremonial staffs or on magicians using magic wands. However, rulers have been carrying staffs, or sceptres, for 5,000 years, ever since gods were shown holding them, and stories told about them suggest that they had various functions such as healing and water divining. (9) The hook, or heqa, staff ,  shown held by Ancient Egypt’s white clothed civilising god Osiris, was later adopted by the Church as the bishops’ pastoral staff.


Stories about a staff which  was planted in the ground, sometimes with star-god links, was popular in several early cultures. There were versions of it in Jewish and Christian, English, legends, among the Ashanti in West Africa and the Incas in Peru.(10)


Strange objects held by “warriors” – Tula Pyramid platform, Mexico

Animals, birds, and insects have been used in symbolism for thousands of years. The bull was a religious symbol throughout the Mediterranean Region and it was also used in rituals. In Egypt, for example, the Apis Bull was regarded as an incarnation of Osiris and a replacement was chosen when it died. (11)


Egyptian God-bull Apis. Louvre Museum


2nd Century A.D sculpture of Nandi [Bull]

the-tauroboliumTaurobolium comes from Rome the Eternal City (Clara Erskine Clement) also published 1900

The bull also played an important role in the bloodthirsty initiation rituals of Mithraism, in Ancient Rome, and, with related sky-god traditions, it appears in the Ancient Greek story of Theseus and the Minotaur (12). Some scholars believe that the bull was only a symbol of strength but what they overlook is that it also represented Taurus whose most famous stars, the Pleiades, are in its neck. These stars were associated with the Creation, the Flood, and the Star-People. Their appearance, at certain times in the year, was an occasion for joyful celebration and just as they were associated with the Creation, their dawn appearance often began a new era and the agricultural season. One of the Indonesian tribes claims to know where the craft of the Pleiades people landed. They also believe that they came from these stars and that they will return there when they die. (13 ) Similar beliefs are found among the Native American tribes, such as the Lakota, in whose traditions, the Pleiades are in the head of the ‘White Buffalo’ constellation.

Some early religious traditions, legends, rituals and symbolism, imply that the star-people arrived on Earth in a fleet of discs which emerged from a huge mother ship (14) and so it’s not surprising that the symbol frequently used to represent their craft appears to have been the circle and that the most prominent disc in the sky, the sun, played an important role in many festivals. Some native people, such as the North American Natchez, believed that the great civilizer, who visited their ancestors, emerged from the sun (15) and festivals were often celebrated when there was a heliacal rising of the Pleiades. Stone, and earth, circles, which have been found in most countries, also seem to have represented the ‘homes’ of the gods (16) just as temples have done for thousands of years. These circular enclosures were used for religious, and ceremonial purposes, from the Stone Age era and until comparatively recently by people who still follow their ancient traditions. (17) Archaeologists believe that the famous, ‘5,000 year old’, Stonehenge site, in Wiltshire, England,  was associated with ancestor worship but its symbolism, which was changed several times, suggests that it was dedicated to the worship of the ‘recently departed’ star people. Because they have a  different mindset, traditional researchers  have overlooked  the deeper significance of one of the important symbols, outside the main circle, as it means nothing to them, and the same comment applies to  Stonehenge’s  astronomical alignments to a group of  ‘circular earth mounds’. (18)



Twenty four miles north of Stonehenge, near the Wiltshire town of Marlborough, in ‘ crop circle country’, is the lesser known Avebury complex whose main features are the largest  stone circle in the British Isles and the 131 ft high circular Silbury Hill, the largest man-made mound in Europe, which can be seen from miles around.




Silbury Hill

The purpose of this hill has mystified researchers as excavations have revealed that it wasn’t a rich burial mound as was previously believed. Beside Silbury Hill there is a small lake. Many Ancient Egyptian temples had a sacred lake and religious sanctuaries were often built beside a river. But what’s  so special about water? Well, according to some creation stories, all that existed in the beginning was the Primeval Sea and from it emerged the Primeval Land ( the World Mountain). There were representations of  this mythical mount in several countries, such as the moat surrounded 12th century Angkor Wat in Cambodia, the Great Pyramid in Egypt, and pyramids in Teotihuacan, Mexico, and Tiahuanco in the Andes and some of the symbolism, built into these structures, was sky-god related.


Reconstructed pyramid from Chaldea  from ‘The Story of the Nations
by Zenaide A Ragozin (per Perrot and Chipiez) published 1900

Pyramids of Giza, Egypt


Great Pyramid, Giza, Egypt

Below, GeoEye’s IKONOS satellite took this image of Angkor Wat 


Since this sacred symbolism is also built into Silbury Hill, it would seem that it, and its lake, were also versions of the World Mountain. (19) Incidentally, there was also a circular mound, similar to Silbury, in pre-Colombian Mexico.(20)

On 17 November 2013, at a jungle site at La Mana, Cotopaxi Province, Ecuador, Alexander Putney, and his partner Suzanne Benoiton, made a remarkable discovery of a ‘river fronted’, triangular shaped, hill upon which there are parallel lines of shaped stones. This site, which is thought to have been part of a lost pyramid complex, is now known as the Hummingbird Pyramid and, like various other water linked pyramids, it seems to have been a version of the World Mountain which rose from the Primeval Sea. Those people who have read my books on this subject, will appreciate the deeper significance of the area’s other watery features which also suggest that this site had been specially chosen. (21)  Although the religious beliefs of the Hummingbird Pyramid’s builders are unknown, we need to bear in mind that there were Pleiades linked traditions throughout the Americas and that many of its peoples had legends of a civilising sky-god who visited their ancestors.

Over thirty years ago, I was present at a series of channelled communications where information was given about the visit of the star-people, and one of the messages, channelled through psychic Gerry Sherrick, said that when their craft was approaching Earth, it resembled a huge comet with its tail stretched across the sky. (22)


This image of Comet McNaught was captured by the European Southern Observatory in Chile as both the comet and the sun were setting over the Pacific Ocean. The ocean surface appears nearly flat at this distance. Credit: European Southern Observatory

I later learned that, in 1519, when a comet appeared in the sky, and other strange things occurred, including the landing in Mexico of the fair skinned Spaniard Cortes, the Aztec Emperor Montezuma was convinced that the civilising white god, Quetzalcoatl, had returned as predicted. (23) The  Bible ,(Isa.14:29), also mentions fiery flying serpents and in Mexico, comets were called ‘flaming serpents’.(24) Could it be that this is why the snake was associated with the gods, throughout the Early World, and why this creature appeared  in so many early traditions and legends. In Ancient Egypt, and several Asian countries, special importance was placed on the cobra. It’s often found in art and there were representations of it on temples. The python was revered in Africa as was the rattlesnake in parts of the Americas. Some Native Americans, such as the Hopi, celebrate with serpent dances and snakes are depicted, with tall strange figures, among the numerous rock drawings in Utah, U.S.A. In Central America, gods were also shown emerging from the mouths of snakes. Serpents were depicted in Bronze Age rock art in Bohuslan in Sweden. (25) and snake worship was popular in parts of Early Europe.


Hearth  serpent at Pompeii

One of the surviving European serpent dances  is popular in Helston, Cornwall, England, in the form of the Furry Dance in which people dance in a snake-like procession through the town’s streets. It was also common for people to keep live snakes in their homes, in parts of Northern Europe, until the 16th century. (26)


Furry Dance

Serpent worship in Africa dates back to the mists of time and some African tribes celebrate with snake dances. In the African Dahoman kingdom of Whydah, live pythons were kept in snake houses in every village (27) and among the West African Ashanti there are ‘sky-god serpent legends’ which are remarkably similar to others in Central America. (28) Could it be, as some alternative scholars believe, that the Negroid features on many huge Olmec, stone heads, in Mexico, are evidence of an early African presence on that side of ‘The Pond’?


The Great Serpent Mound , Ohio

There is an astronomically aligned serpent mound in Ohio, U.S.A , whose winding shape is reminiscent of sky-god symbolism, and there’s also one in Scotland where people enacted their religious rituals.(29) The serpent also played a role in the sky-god traditions of the Australian Aborigines and small serpent mounds were used by the Warramunga Aborigines in their rituals. (30)


Australian Aboriginal Warramunga Ceremony.
Source: Customs  of the World which was published around 100 years ago. 

 For thousands of years, birds, and wings, have been used to represent flight and also beings from another world. There are winged gods in Assyrian religious art and angels, in Christianity, are always shown with wings. Across the Northern Hemisphere, and North America, the eagle was associated with gods.


This winged god is from Zenaid A Ragozin’s Story of the Nations (per Perrot and Chipiez) 1900


The Eagle headed figure from Chaldea is from  Ragozin  (per Smith’s Chaldea) 

In South America, the condor was a companion of the white- robed  civilising god Viracocha and there is a huge effigy of one among the  mystical drawings in Peru’s Nazca Desert. The Church adopted the dove to represent the Holy Spirit and it often appears on church windows.



This white bird was previously used by the Greeks to represent the Pleiades and it appears in several early deluge stories including the biblical version.  George Catlin, (1796- 1872), was an American traveller, and author, who painted portraits of the Native Americans, and he reported that ‘the Prairie Indians regarded the turtle dove as a messenger of the cycle of rebirth.*’(31)

*In both the Old and New Worlds, traditions relating to the beginning of a new era were often linked with the appearance of the Pleiades.

Most of the thousands of rock drawings, found around the world, are linear but in Bohuslan, in Sweden, parts of Africa, Easter Island, Utah and the early Mississippi culture in the U.S, and in the Canary Islands, there are figures of a ‘bird-man’. This mythical part bird part human probably represented a god. The Thunder Bird, is a supernatural bird in North American Native legends and it’s also depicted on totem poles on the North-West Pacific Coast. One might expect that it was only linked with thunder but one North American legends, which appears to be sky-god linked, suggests that the 1960’s British Sci-fi series ‘Thunderbirds’, with its space rescue vehicles, is much closer to the truth than its makers could ever have imagined. (32)

The spiral has featured  in world symbolism for thousands of years. Although it’s shown with varying numbers of winds, there is one, more complex, type that’s been found in many  countries from Ireland in the Far West to Siberia in the Far East (33), and it’s also used by the North American Hopi Indians. I have discussed this spiral, in more detail, in ‘ The Pleiades Legacy (The Old World)’, and I have shown that it appears to  be sky-god linked. There are numerous spirals among the thousands of ground drawings in Peru’s Nazca Desert and some of them are also star-god symbols (34).


Nazca Drawings – Spiral

What’s also there is a set of concentric circles that  has also been found in other countries, in prominent places, such as on a mountain top in Brazil (35). In Ancient Sumeria, it was a symbol of the god Ea and other forms of it were linked with his Egyptian, and Incan, counterparts – the gods Osiris and Viracocha.

The amazing story of the star peoples’ visit was also alluded to  in star-lore, astrology, in the symbolic layout, and astronomical alignment, of some Stone Age sites and temples, in traditions, legends, allegorical stories, festivals, Early World art, place names, early folk customs, astrology, calendars, the sudden rise of civilisation 5,000 years ago in the era of sudden climate change, and especially in sacred numbers, which I have not discussed in this article, which play an important role in unlocking the hidden history of civilised man.
So, what these various sources suggest is that 5,000 years ago, our world was visited by aliens, at  a  time of greed and conflict, in the history of man, and they came here, with their craft, in a huge mother-ship. The visitors, who the Ancients associated with the Pleiades, had the appearance of tall white men dressed in long white robes. Among the high tech equipment, that they brought with them, were multi-purpose staffs and replicas of these were adopted as items of royal regalia by many people in the Early World. The star-people had previously provided advanced technical information, for those people deemed worthy of it, and they had also taught people agriculture. Some people, however, misused the knowledge that was given to them and the ‘gods’ destroyed them with a massive flood. This flood was the subject of the  hundreds of simple deluge stories that were told around the world. When the Europeans colonised the Americas, they suppressed the Native Americans’ star-god religions and replaced them with Christianity.  However, the visit of the star –people has never been completely forgotten and some Native Americans are still awaiting their return.


  1. Leonard Farra. The Pleiades Legacy.
  2. Edmond Sollberger. The Babylonian Legend of the Flood. (p15)
  3. Leonard Farra. The Pleiades Legacy. (The New World).
  4.      “                “     “         “        “             “      “       “       .(p60-64)
  5.      “               “   The Pleiades Legacy. (p 14/15)
  6. E.A.Wallis Budge. The Book of the Dead. (p88)
    L. Taylor.Hansen. He walked the Americas. ( p87)
    Daniel G.Brinton. Myths of the Americas. (p196)
  7. Leonard Farra. The Pleiades Legacy.
  8. Joan Oates. Babylon. (p66)
  9. L.Taylor Hansen. He Walked the Americas. (p87)
    Leonard Farra. Genesis Seven. (p9)
  10.        “            “   The Pleiades Legacy.(The New World. (p152)
  11. E.A Wallis Budge. The Gods of the Egyptians. ( bk 1 p330)
  12. Leonard Farra.The Pleiades Legacy. (p180)
  13. Lawrence Blair with Lorne Blair. Ring of Fire.
  14. Elizabeth Van Buren. Lord of the Flame. (p51)
    Chris Wissler.Indians of the United States. (p132)
    Leonard Farra.The Pleiades Legacy. (p15)
    Francois Lenormant. Chaldean Magic, Its Origin & Development)
    Zenaide A.Rogozin, The Story of the Nations- Chaldea (p182)
    Wm.R.Fix. Star Maps. (p77)
  15. Wendell .H.Oswalt. This land was Theirs .( p472)
  16. Leonard Farra. The Pleiades Legacy (The Stone Age ).
  17. Customs of the World.(Vol.I.(p183)
  18. Leonard Farra. The Pleiades Legacy (The Stone Age).  ( p68-)
  19. Ibid. (p83)
  20. Leonard Farra. The Pleiades Legacy) ( The New World. (p26).
  22.  Leonard Farra. Genesis Seven.( p33)
  23.  Anna Benson Gyles and Chloe Sayer. Of Gods and Men.(p77)
  24.  The Penguin Dictionary of Symbols. (p226)
  25.  Peter Gelling & Hilda Ellis Davidson. The Chariot of the Sun. (p40)
  26.  James Ferguson. Tree and Serpent Worship. (p22)
  27.  G.T.Bettany. The World Religions. (p57/8)
  28.  Leonard Farra. The Pleiades Legacy. (The New World.( p24)
  29.  Customs of the World. (p164)
  30.  H.Davenport Adams. Curiosities and Superstition. (p192)
  31.  The Penguin Dictionary of Symbols. (p307)
  32.  Norval Morriseau. Legends of my People (The Great Ojibwa). (p6)
  33.  Adrian Fisher & Georg Gerstler. The Art of the Maze. (p19)
  34.  Leonard Farra. The Pleiades Legacy (The NewWorld). (p142)
  35.  Erich Von Daniken. In Search of Ancient Gods.(p77)

Copyright 2014 by Leonard Farra



Aliens & UFO's

UK UFO case to be kept secret until 2072

The UK Department of Defense has blocked the planned release of a dossier detailing the famous UFO incident.

Back in August 1990, two tourists walking in the Scottish Highlands near Calvine, Pitlochry, witnessed a strange rhombic object hovering over the nearby landscape.

They managed to take pictures of the UFO before it flew away at significant speed.

Eager to share what they saw, the couple contacted the Scottish Daily Record and shared both their story and the photos they took.

Then the journalists shared the pictures with the UK Department of Defense.

It turned out that the tourists weren’t the only ones who saw the object – the pilot of the RAF Harrier jet also witnessed the phenomenon – again near Calvine – after being forced to investigate this UFO.

Military intelligence officers sent these images to JARIC, which is the Joint Air Intelligence and Reconnaissance Center.

It is the UK’s military center of excellence when it comes to image analysis. These intelligence officers concluded that these photographs were real and that no one had the slightest idea what they were.

Several mock ups of the photos have been made, while the real things remain hidden
Several mock ups of the photos have been made, while the real things remain classified

Thirty years later, the dossier of the Ministry of Defense, including photographs, was scheduled for declassification and publication, which is typical of such documents.

However, the release has now been postponed for another 50 years for unknown reasons.

According to the 30-year rule, the file was supposed to be released on January 1, 2021, but if the ministry gets it, it won’t be released until January 1, 2072 – an 82-year closure.

“By the time the world gets to see the file, the two witnesses will be dead. It is crazy. What are the authorities trying to hide?”

A complaint lodged under the Freedom of Information Act about the National Archives withholding the documents is now under investigation by the UK information watchdog, the Information Commissioner’s Office.

The National Archives refused to comment further. The MOD refused to comment at all.

What are the authorities trying to hide?

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Aliens & UFO's

FBI decrypted documents confirm that there are giant aliens

The topic of aliens has always attracted attention. Recently, foreign media disclosed that a declassified document released by the Federal Bureau of Investigation (FBI) once again confirmed the existence of UFOs and aliens.

FBI Declassified Document: Describes UFO and Aliens

The British “Daily Star” reported that earlier this year, the FBI released the decrypted documents in 1947. The 70-page decrypted report contained a “Memorandum 6751”. The person who wrote the report was an anonymous university professor.

“Memorandum 6751″ mentioned that there were flying saucers, unidentified creatures, and ” giant aliens resembling humans “.

The report stated that these aliens are like humans, “but larger in size. They are not from any planet known to people, but from the etheric.” “Ether” is a term used in ancient Greece, generally referring to the atmosphere or sky.

Sketch of flying saucer. (

There is also a description of the flying saucer in the decryption report, which refers to the fact that most of the flying saucers are loaded with alien creatures. The flying saucers have powerful radiation, are very fast, and have powerful attack capabilities.

“These flying saucers have a kind of radiant energy or light that can easily disintegrate any spacecraft that launches an attack. They can re-enter (earth) from the ether at will, or they can simply disappear from our sight without leaving a trace.”

The report states, “If one of these (flying saucers) is attacked, the attacking aircraft will almost certainly be destroyed. As far as the general public is concerned, this may lead to proximity panic and international suspicion.”

Tesla is a ” Venusian “

In recent years, due to the expiration of the confidentiality period, the FBI has published many decrypted documents on its official website, including one about the famous inventor Nicholas. Tesla (Nikola Tesla) declassified documents, caused a public heat. The document mentioned that Tesla came from “Venus” and was an “alien”.

The FBI declassified document mentioned that the famous inventor Nicholas. Tesla came from “Venus” and was an “alien”. (Public domain)

The decrypted document is called “Nikola Tesla Part03 of03”. It is the third document about Nikola Tesla decrypted by the FBI. It has 64 pages of content, some of which are blacked out and cannot be distinguished.

The remaining content that is not blacked out contains the following passage: “The people of the universe have contacted Nikola Tesla many times and told the FBI that Tesla was from Venus. Tesla was brought to the earth in 1856 to a Yugoslav couple to raise.”

The publication of this document shocked the world. Faced with a wave of discussions and doubts from netizens, the FBI did not make any response or explanation, which is even more curious.

F-18 fighters chase UFO

“The Wall Street Journal” recently reported that the non-profit organization “National UFO Reporting Center” data shows that so far this year, UFO sightings have increased by 51% over the same period last year. The center has received approximately 5,000 sightings reported.

On September 8, the United States retired Lieutenant Colonel David. David Fravor accepted the Massachusetts Institute of Technology scientist Rex. In a live webcast interview with Lex Fridman, he talked about the bizarre experience of driving an F-18 fighter jet to chase UFOs 16 years ago.

There are American pilots chasing UFOs in F-18 fighter jets. F-18 fighter data map. (Michael Dodge/Getty Images)

On November 14, 2004, a UFO was found in the waters of San Diego, California, and Frevo piloted an F-18 fighter to investigate. Both he and the pilot of the other fighter saw a white Tic Tac mint-shaped flying object.

Subsequently, the pilot Chad Underwood flew an F-18 fighter jet, caught UFO on the radar, and successfully filmed UFO video with an infrared camera.

In April this year, the Pentagon released three videos of UFOs, one of which was taken by Underwood during this operation.

12 U.S. soldiers live on alien planets

Former Minister of Defense of Canada Paul. Paul T. Hellyer once disclosed that there are aliens living on the earth and working for the US government. Many US presidents have also admitted the existence of aliens on different occasions.

In addition, some U.S. military personnel disclosed that a top-secret exchange between the U.S. military and aliens was named “Operation Zeta,” and an alien envoy came to the United States. In July 1965, 12 American soldiers secretly boarded an alien spacecraft to the planet Zeta.

Of these 12 people, 4 never returned to Earth. Of these 4 people, 2 died, 2 chose to stay on Zeta, and the remaining 8 returned to Earth 13 years later.

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Aliens & UFO's

How many extraterrestrial civilizations can exist nearby?

Still from the movie "Prometheus" 20th Century Fox

In the 12th episode of the series ” Space”, Which aired on December 14, 1980, co-author and host of the program Carl Sagan introduced viewers to the eponymous equation of astronomer Frank Drake. 

Using it, he calculated the potential number of advanced civilizations in the Milky Way that could communicate with us using the extraterrestrial equivalent of our current radio communication technology. 

Sagan’s estimate ranged from a “paltry few” to millions. If civilizations don’t always destroy themselves shortly after the discovery of radio astronomy, then the sky can literally buzz with messages from the stars,” Sagan said in his inimitable manner. And yet Sagan was pessimistic about the fact that civilizations are able to survive their own technological “Youth” – a transitional period when the development of culture, say, nuclear energy,

If aliens exist, then why don’t we “hear” them?

Life in the universe

Sagan and other scientists suggested that the emergence of life on planets should be a cosmic inevitability, since according to geological data, it arose on earth amazingly quickly: more than four billion years ago, almost immediately after our planet cooled down enough. And if, as in our world, life on other planets arose quickly and evolved, becoming more complex over time, perhaps intelligence and technology could also be ubiquitous throughout the universe.

However, in recent years, some skeptical astronomers have tried to lend more empirical weight to such claims, using a sophisticated form of analysis called Bayesian statistics. The researchers focused on two unknowns: the likelihood of life on Earth-like planets from abiotic conditions – a process called abiogenesis – and therefore the likelihood of intelligent life. But even with such estimates, astronomers disagree about what they mean for life in other parts of the cosmos.

Drake’s equation, introduced by an astronomer in 1961, calculates the number of civilizations in our galaxy that can transmit or receive interstellar messages using radio waves. It is based on the multiplication of a number of factors, each of which quantifies some aspect of our knowledge of the galaxy, planets, life, and intelligence. 

These factors include: stars with exoplanets; the number of inhabited planets in the exoplanetary system; the number of inhabited planets on which life originates, and so on.

We may never know if there is life beyond Earth.

Today we know that worlds around stars are the norm, and that Earth-like worlds are common in the universe. However, one of the biggest uncertainties in the entire chain of factors is the likelihood that life, which originated in other worlds, makes the leap from chemistry to life. Ignoring this uncertainty could lead astronomers to make some pretty bold claims.

For example, astronomers from the University of Nottingham in England recently made headlines when they calculated that our galaxy must have at least 36 intelligent civilizations capable of communicating with us. This estimate was based on the assumption that intelligent life appears on other habitable terrestrial planets approximately 4.5-5.5 billion years after their formation. 

However, it is difficult to answer questions about the probability of abiogenesis and the emergence of intelligent life, because scientists have only one information: life on Earth.

Another problem with assumptions based on what we observe locally is the so-called selection bias. Imagine buying lottery tickets and winning on your 100th try. In this case, it would be reasonable to designate the probability of winning the lottery as 1%. 

This misleading conclusion is, of course, a selection bias that occurs if you only survey the winners and none of the losers (i.e. tens of millions of people who bought tickets but never won the lottery). When it comes to calculating the probability of abiogenesis, exactly the same thing happens, since scientists simply do not have information about all the worlds where life did not appear.

Abiogenesis probability

If you apply Bayes’ theorem to calculate the probability that an event, such as abiogenesis, will occur, astronomers first come up with a probability distribution for that event — a better guess, if you will. For example, it can be assumed that abiogenesis is as likely between 100 and 200 million years after the formation of the Earth, as it is between 200 and 300 million years after that time or any other 100-million segment of our planet’s history. These assumptions are called Bayesian a priori . Statisticians then collect data or evidence and combine the previous and actual data to calculate the posterior probability.

The answer to the question of how common life is in the galaxy remains unknown

In 2012, astronomers at the Institute for Advanced Study in Princeton were the first to apply Bayesian analysis to abiogenesis. According to their approach, life on a planet like Earth orbiting a star like the Sun does not arise until a certain minimum number of years (tmin) after the formation of this world. If life does not arise before a certain maximum time (tmax), then, as its star ages (and eventually dies), conditions on the planet become too hostile for abiogenesis.

However, this study is not without its drawbacks. For example, some researchers have questioned the assumption that intelligence emerged at a specific time after abiogenesis. This prior could be another example of selection bias, a concept influenced by the evolutionary path that our own intelligence has taken.

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