Tag: alien civilizations

STELLAR ENGINES: USING A STAR AS A STARSHIP

On By AlessandraIn Extrasolar Planets, S.E.T.I., Sci-FiLeave a comment

Introduction

Imagine looking up at the night sky and knowing that humanity has the power to move entire stars across the Galaxy. This concept isn’t pure fantasy. A future technology could move stars using stellar engines. This hypothetical megastructure enables an advanced civilization to harness the energy of its parent star and even guide its solar system to a safer or more hospitable region of the cosmos.

But why would anyone want to move a star? The universe is dynamic and often dangerous. Stars are vulnerable to gravitational interactions, nearby supernovae, and even the slow drift through the Galaxy’s regions of varying radiation levels. Stellar engines offer a tantalizing vision of cosmic-scale problem-solving, where intelligent beings could shape their fates on an interstellar stage. For us on Earth, these ideas stretch the limits of imagination and raise intriguing questions about our future in the universe.

What Are Stellar Engines?

At their core, stellar engines are large, theoretical structures intended to control a star’s energy output or even move the star itself. These megastructures stem from speculative science and astrophysics, providing solutions for considerable problems in space and revealing great possibilities for advanced civilizations.

To grasp stellar engines, it’s helpful to consider the Kardashev Scale, which measures a civilization’s technology based on energy use. A Type II civilization can use all the energy from its star. Stellar engines go beyond this by allowing the civilization to influence the star’s movement and behavior.

Stellar engines are linked to megastructures like Dyson Spheres, which are large shells or groups of satellites that surround a star to gather its energy. Unlike just collecting energy, stellar engines also have systems that use that energy for movement. This means they are energy sources and tools for navigating the Galaxy and ensuring survival.

Though purely theoretical at this stage, stellar engines are fascinating because they represent the ultimate fusion of science and engineering. They challenge us to think big, not just in terms of individual planets or solar systems, but in the ability to reshape the Galaxy. By studying these ideas, we gain insight into the limits of technology and the ingenuity needed to transcend them.

How Do Stellar Engines Work?

Stellar engines work by harnessing the immense energy output of a star and redirecting it for specific purposes, such as propulsion or power generation. While the exact mechanisms remain speculative, scientists and theorists have proposed several designs that outline how these structures work. Here are the primary types of stellar engines:

  1. Shkadov Thruster. 

The most straightforward and widely discussed stellar engine design, the Shkadov Thruster, uses a giant, reflective mirror to create an imbalance in a star’s radiation pressure. Reflecting light asymmetrically generates a small but continuous thrust that can slowly move the star and its solar system over millions of years. Think of it as a colossal cosmic sail.

2. Kardashev – Dyson Engine

This concept involves constructing a Dyson Sphere or Dyson Swarm around a star to capture its energy. A part of this energy is then redirected to power propulsion systems, effectively turning the star into a galactic engine. This design emphasizes energy efficiency and control, offering mobility and a near-limitless energy supply for the civilization operating it.

3. Caplan Thruster

A more modern and complex design, the Caplan Thruster, introduces active intervention. This system would collect hydrogen and helium from the interstellar medium or the star itself and use fusion reactions to create plasma jets. These jets would push against the star, generating propulsion. The Caplan Thruster represents a significant step toward controlled and directional stellar movement, but it requires advanced technology and precise engineering.

Each design has challenges, from material requirements to energy management and sheer scale. For instance, building a reflective surface or a Dyson Swarm large enough to enclose a star is far beyond humanity’s current capabilities. Nevertheless, these ideas offer a blueprint for what might one day be possible for civilizations millions or billions of years ahead.

Stellar engines also highlight the delicate balance between ambition and practicality. Even with advanced technology, the energy needed to move a star is astronomical—yet the slow, steady movement enabled by these engines could allow civilizations to adapt to long-term cosmic threats and opportunities.

Why Move a Star?

The idea of relocating a star may seem excessive or unnecessary, but there are compelling reasons why an advanced civilization might consider such an effort. Here are some key motivations:

  1. Avoiding Cosmic Hazards

The universe is filled with potential threats that could endanger a star system’s habitability. Supernovae, gamma-ray bursts, or even rogue black holes pose existential risks. A stellar engine could allow a civilization to move its star system away from dangerous regions of space, ensuring long-term survival.

2. Optimizing Habitability

Over time, stars naturally evolve and change, impacting the habitability of their surrounding planets. For instance, a star may brighten as it ages, potentially rendering its planets too hot for life. A stellar engine could help keep the optimal distance between a planet and its star, prolonging the system’s habitability.

3. Galactic Colonization

As civilizations expand and seek new frontiers, stellar engines could allow entire star systems to migrate to regions with abundant resources or less competition. This would aid interstellar colonization on a massive scale, allowing a civilization to thrive across the Galaxy.

4. Escaping Dying Galaxies

In the distant future, galaxies may face challenges such as reduced star formation or gravitational interactions that lead to destabilization. Moving stars to more active or stable regions could guarantee the longevity of a civilization’s energy sources and resources.

5. Creating Custom Galactic Trajectories

Advanced civilizations might engineer their star systems’ trajectories to explore specific regions of the Galaxy, join in cosmic-scale projects, or even form alliances with other civilizations. Stellar engines would supply the mobility necessary for such strategic decisions.

While these motivations are speculative, they highlight the strategic thinking that might drive a civilization’s pursuit of stellar engines. These megastructures are not merely survival tools but instruments of cosmic exploration, adaptability, and ambition. For humanity, even considering such possibilities challenges us to rethink our place in the universe and inspires a future of limitless potential.

Challenges And Realities

While the concept of stellar engines sparks the imagination, the challenges of building such colossal structures are daunting. These challenges remind us that stellar engines, though theoretically possible, remain firmly in the realm of speculation due to technological, logistical, and ethical barriers. Here are some of the most significant hurdles:

  1. Energy Requirements

Moving a star involves manipulating an astronomical amount of energy. For instance, generating the thrust needed to shift the Sun would need far more energy than humanity now produces or could produce with foreseeable technology. Even harnessing a small part of a star’s energy for propulsion is monumental.

2. Material Limitations

The materials needed to construct structures as massive as a Dyson Swarm or a Shkadov Thruster must withstand intense radiation, extreme heat, and the gravitational forces near a star. Developing these materials would be a prerequisite to any stellar engine project.

3. Time Scales

Even with advanced technology, moving a star would take thousands, if not millions, of years. This requires planning and long-term thinking far beyond what humanity has ever achieved. Focusing on such projects over vast periods would be essential for civilizations capable of stellar engines.

4. Engineering Complexity

The scale and precision needed to build and run a stellar engine are unprecedented. Coordinating the construction of a Dyson Sphere or directing a Caplan Thruster would need breakthroughs in robotics, artificial intelligence, and space logistics.

5. Ethical Considerations

Using stellar engines would have profound implications for any planets or systems affected by a star’s movement. Disrupting the orbits of neighboring systems or causing ecological harm would raise serious ethical questions. Advanced civilizations must balance their ambitions with a commitment to minimizing damage.

6. Risk of Failure

The risks linked to such projects are immense. A miscalculation in energy output or propulsion could destabilize an entire solar system, potentially threatening any civilizations or ecosystems reliant on that star.

Despite these challenges, stellar engines represent the pinnacle of speculative engineering—a testament to the ingenuity and ambition of intelligent life. Exploring these ideas pushes the boundaries of what we consider possible and inspires us to prepare for a future that may one day include cosmic-scale projects. Whether or not humanity ever builds a stellar engine, pursuing such knowledge is a vital part of our journey to understand the universe and our place within it.

Conclusion

Stellar engines are more than just a speculative idea; they are a testament to the boundless potential of intelligent life to reshape the universe. These concepts challenge us to think on scales far beyond our current technological capabilities and inspire us to dream of a future where humanity can wield the power of the stars themselves.

While the challenges of constructing such megastructures are immense, exploring their possibilities encourages innovation and long-term thinking. They remind us that our journey as a species is not confined to the Earth or even the solar system but tied to the vast expanse of the cosmos. By considering the engineering, ethical, and logistical hurdles of stellar engines, we take steps toward understanding what it means to be a genuinely interstellar civilization.

The dream of moving a star—or even shaping the Galaxy—represents science and imagination’s ultimate fusion. Though we are far from realizing such feats, pursuing these ideas can push the boundaries of our knowledge and fuel our aspirations. As we stand on the brink of incredible technological advancements, the question is no longer whether we can dream big but how those dreams might become reality someday. Stellar engines remind us that the universe is not just a backdrop to our existence but a playground for innovation and discovery. They urge us to embrace a cosmic perspective, where the limits of what we can achieve are defined only by the scope of our imagination and the courage to act upon it.

Through the lens of stellar engines, we glimpse a future where humanity transcends its terrestrial origins to become a force of creativity and adaptation on a galactic scale. This vision challenges us to build the tools and technologies needed.

Zelvyn T’hrialis, The Undercover Cat

On By AlessandraIn Cats, Cats, Sci-Fi, Short Stories, Wolfram "Morsy" Chettoh

It had been nearly seven decades since Zelvyn T’hrialis first set foot on Earth as an undercover cat, black with piercing yellow eyes. Zelvyn came from the Omega Centauri star cluster. He was a member of a highly advanced humanoid race known for their incredible intellect and advanced technologies that far surpassed anything humans had developed. The High Command for Intergalactic Operations (HCIO) tasked him to study human behavior, delving deep into their social structures, emotional complexities, and daily routines. This was in preparation for the imminent invasion of Earth.

Zelvyn roamed the planet as a cat, observing humans and their interactions from a unique and often amusing perspective. He watched families during holidays, saw daily life’s mundane yet intimate rituals, and even experienced the fleeting joys and sorrows that filled human hearts. Over the years, he infiltrated countless households, always charming his way into the hearts of his unsuspecting owners with his intelligence and grace. But it was with Eliza, a kind-hearted middle-aged teacher who inspired young minds, that Zelvyn formed a more potent bond than before. Their bond transcended the boundaries between species and transformed their lives.

Eliza had rescued Zelvyn from a shelter sixteen years ago, unaware of his true identity. She had showered him with love and care, treating him like family and integrating him into her daily life with unwavering affection. Zelvyn, in turn, had grown to love Eliza in a way he never thought possible, feeling an emotional depth alien to his kind. But now, the time had come for him to move on to his next assignment, a mission that weighed heavily on his heart. Zelvyn found himself torn, caught in the crossfire of duty and love. He had to choose between his loyalty to his race and his attachment to his owner, a decision that would alter the course of their destinies forever.

On top of that, Zelvyn had recently befriended Luna, a lively Siamese cat that Eliza had adopted, injecting new energy into the household. Luna was a playful and affectionate feline, always eager to chase after stray shadows and pounce on unsuspecting toys. Still, Zelvyn couldn’t help but feel superior to her in every way. He constantly compared Luna to himself with a smugness he couldn’t shake, finding her antics amusing yet somewhat juvenile.

As the day of his departure drew near, marked on his mental calendar with a mixture of dread and anticipation, Zelvyn struggled with conflicting emotions. On one hand, he knew that his mission was crucial for the future of his race, a task that held the weight of intergalactic responsibility. But he faced a dilemma that gnawed at his conscience. He couldn’t bear leaving behind the home that had welcomed him so warmly. He also couldn’t bear leaving the people who had shown him so much kindness, understanding, and unconditional love, knowing that their lives would carry on without him as a comforting presence. Each pawstep felt heavier as he pondered the choices ahead, the invisible thread tying him to Eliza and the life they had built together, making his heart ache with the thought of separation.



Finally, on the eve of his departure, Zelvyn made a decision. He sent a message to the HCIO, informing them that he had chosen to stay on Earth. In his message, he painted a bleak picture of the planet and its inhabitants, describing humans as violent and ignorant creatures unworthy of conquest.

With that, Zelvyn destroyed his communication device and settled back into his life with Eliza and Luna. He knew that his decision would have consequences, but for the first time in his long existence, Zelvyn felt at peace. He had found a sense of belonging on Earth and was willing to risk everything to protect it.

As he curled up next to Eliza and Luna, Zelvyn felt the warmth of their presence. He knew he had made the right choice. Days turned into weeks, and Zelvyn embraced his new life as a simple Earth cat.

Great Sci-Fi Novels 4: H.P. Lovecraft’s ‘At the Mountains of Madness’

On By AlessandraIn Ancient Civilizations, Books, Reading, Silurian Hypothesis

In a recent post, I discussed the Silurian Hypothesis, which is the possibility that our human civilization is not the first one on Earth. Sci-fi authors have explored this concept in their works for at least a century.

One of the first was Howard Phillips Lovecraft, the author of the Cthulhu Mythos. As early as 1917, he wrote the story Dagon, where the protagonist escapes the German U-boat that sank his merchant ship. However, the sailor soon finds himself on a strange island that “[…] by some unprecedented volcanic upheaval […] must have been thrown to the surface, exposing regions that for innumerable years had lain hidden […]”.

In the middle of the island is a disturbing artifact, an ancient monolith engraved with occult symbols and figures. This human-amphibian mixture fills the protagonist with an inexplicable terror, which only grows worse when a slithering, sucking monstrosity crawls up from the sea and over the monolith. The sight plunges the unlucky man into madness. As a result, he runs away on a “delirious journey” until he wakes up in a San Francisco hospital, where no one believes him, and he’s left alone with the knowledge of the Thing’s existence and what it implies. A Thing so ancient that its existence dwarfs any human concept of time.

Although Dagon is an excellent introduction to Lovecraft’s obsession with vast, inhuman worlds beyond the limit of our knowledge, some of his later works dive even deeper into the rabbit hole of an unbearably old and malign civilization that predates and will outlast humans and their limited, relatively trivial experiences.

In February 1931, he wrote the sci-fi-horror novella At the Mountains of Madness, later serialized in the early 1936 issues of Astounding Stories.

The story is about an American expedition to Antarctica by geologist William Dyer from the fictional Miskatonic University of Arkham. Lovecraft had long been fascinated with Antarctica, though in the 1930s, the continent was not fully explored. As a result, Lovecraft could set his story in a mountainous chain “higher than the Himalayas” (the so-called Mountains of Madness) without fear of contradiction.

The expedition begins promisingly but ends in tragedy and horror after a sub-expedition led by a colleague of Dyer, the biologist Lake, discovers the frozen remains of monstrous barrel-shaped creatures that cannot be reconciled with the known evolution of this planet. They seem half-animal and half-vegetable, with greater brain capacity and super-human sensitivity. Lake jokingly identifies the strange beings with the Elder Things or Old Ones of the Necronomicon, who are “supposed to have created all Earth life as jest or mistake.”

Fig.1: An Antarctic setting in the style of Nicholas Roerich, H.P. Lovecraft’s favorite painter. Image made by the author with Midjourney AI.

Soon, Lake’s sub-expedition loses radio contact with the main party, apparently because of bad weather. However, when Dyer takes a small group of men in some airplanes to find out whatever happened to Lake and company, they discover a devasted camp and no trace of the specimens of the Old Ones, but for a few damaged ones, which they presume must have been buried by Gedney, the one human they couldn’t identify among the corpses.

Fig.2: Lovecraft had a lifelong interest in Antarctic exploration. Image made by the author with Midjourtney AI.

Dyer and a graduate student, Danforth, investigate the mysterious tragedy further by scaling the immense plateau that makes “Everest out of the running.” To their amazement, they find an enormous stone city, fifty to one hundred miles in extent, likely dating to millions of years before any humans evolved on the planet. The subsequent exploration of some interiors leads Dyer and Danforth to conclude that the Old Ones built the city.

Fig.3: A shoggoth in the city of the Old Ones. Image made by the author with Microsoft Bing AI.

Also, by studying some drawings and carvings on the city walls, the two adventurers discover that the Elder Things came from outer space millions of years ago, establishing themselves in Antarctica and eventually spreading across the entire Earth. This is where the shoggoths – shapeless, fifteen-foot masses of gel-like substance which they controlled using hypnotic suggestion – first become important. Over time, these living robots developed a somewhat conscious brain and will, which led to the Old Ones having to deal with the shoggoths’ frequent rebellion attempts. The Old Ones faced more difficulties when other extraterrestrial races, such as the fungus-like creatures from Yuggoth and the Cthulhu spawn, arrived on Earth. The ensuing territorial wars pushed them back to their original settlement in Antarctica. Ultimately, their extinction became inevitable when they lost the ability to travel through space.

Shortly after, Dyer and Danforth discover the body of Gedney and a dog. They also stumble upon a group of Old Ones without their heads, suggesting they regained consciousness after thawing in Lake’s camp. Dyer observes that Gedney’s body was carefully protected to avoid further harm. From this, it can be inferred that the Old Ones were responsible for the destruction of Lake’s camp and took Gedney as a sample. However, the question remains: who killed the Old Ones?

At that point, Dyer and Danforth hear a disturbing piping sound. Afraid it could be some other Old Ones, they flee in terror, but not before they turn their flashlights upon a fast-approaching thing and find that it is “… a terrible, indescribable thing vaster than any subway train – a shapeless congeries of protoplasmic bubbles, faintly self-luminous, and with myriads of temporary eyes forming and unforming as pustules of greenish light over the tunnel-filling front…”

But the two explorer’s trial is not yet over. As they return to camp, Danforth shrieks in horror: “Teke-li! Teke-li!” He has seen something even worse than the shoggoth who killed the Old Ones, something that unhinges his mind, although he refuses to tell Danforth what it is.

Although initially portrayed as scary creatures, the Old Ones are the main focus of the story “At the Mountains of Madness.” Eventually, they are overpowered by the shoggoths, who are described as “the things that even the scary things fear.” Near the end, the Old Ones stop being scary. This is a common theme in stories about civilizations that existed before our current one. For example, similar themes can be found in the novels A Canticle for Leibowitz by Walter M. Miller Jr (1959) and The Second Sleep by Robert Harris (2019). The Old Ones have a deep connection with humans, representing a perfect society that Lovecraft hopes humanity will someday achieve. However, they are much more advanced than humans in various ways, such as intelligence, perception, and artistic ability. As mentioned earlier, the Old Ones are responsible for creating all life on Earth, including humans. Nevertheless, they are destroyed by the shoggoths, initially created by the Old Ones as slaves. This illustrates Lovecraft’s belief in the inevitable rise and fall of civilizations.

Finally, At the Mountains of Madness introduces what later became a trope of sci-fi and fringe literature: most mythological “gods” were mere extraterrestrial beings, and their followers were mistaken about their true nature. The critical passage occurs in the middle of the novella when Dyer acknowledges that the Old Ones must have built the gigantic city in which he has been wandering:

They were the makers and the enslavers of Earth life, and above all doubt the originals of the fiendish elder myths which things like the Pnakotic Manuscripts and the Necronomicon affrightedly hint about.

WHAT WOULD BE A GREAT PLACE TO SEARCH FOR ET?

On By AlessandraIn Extrasolar Planets, S.E.T.I.

The Dyson sphere is a hypothetical megastructure physicist Freeman Dyson proposed in 1960.

According to his paper published in Science magazine, a technologically advanced alien civilization would use increasing energy as it grew. As the most significant source of energy in any solar system is the parent star, sooner or later, the civilization would build orbiting solar panels to try to capture it. Such structures would take up more and more space until they eventually covered the entire star like a sphere.

In a 2008 interview with Slate, Dyson also credited the concept to writer Olaf Stapledon, who introduced it in his novel Star Maker in 1937.

Dyson’s hypothesis turned out to be hard to verify because a complete Dyson sphere, absorbing all of the light from the star, would be invisible to an exo-planet hunting telescope (such as NASA’s Kepler). Only half-completed spheres would have a chance to be discovered.

Unfortunately, a Dyson sphere is unlikely to remain under construction for long. The time it takes to make a Dyson sphere is relatively short. A 2013 paper by Stuart Armstrong and Anders Sandberg (“Eternity in six hours: Intergalactic spreading of intelligent life and sharpening the Fermi paradox”) estimates that disassembling Mercury to make a partial Dyson shell could be done in 31 years.

An alternative would be to look for waste heat in the infrared. After being absorbed and used, the energy from a star needs to be reradiated, or else it would build up and eventually melt the Dyson sphere. This energy would be shifted to longer wavelengths so that a Dyson sphere might give off a peculiar energy signature in the infrared. In other words, Freeman Dyson saw a search for his namesake spheres as a complement in the infrared to what Frank Drake’s Search for extraterrestrial intelligence (SETI, see previous blog post) had begun to do with radiotelescopes.

Carl Sagan and Russell Walker first voiced an issue with Dyson’s SETI notion in their 1966 paper “The Infrared Detectability of Dyson’s Civilizations” for the Astrophysical Journal. The authors noted that:

discrimination of Dyson civilizations from naturally occurring low temperature objects is very difficult, unless Dyson civilizations have some further distinguishing feature, such as monocromatic radio-frequency emission.

In the following decades, the search for Dyson spheres expanded dramatically. Starting from the 1980’s researchers went to work using sources identified by the Infrared Astronomical Satellite (IRAS). These early searches produced little o no results, as most Dyson sphere candidates had either non-technological explanations or needed further study. Subsequent investigations using NASA’s space-based WISE (Wide Field Infrared Survey), with higher resolution than IRAS, have all concluded that the identification of a promising source would not in itself be proof of an extraterrestrial civilization unless the object could be followed up with more conventional methods, such as laser or radio search.

Among the latest developments concerning Dyson spheres are the following:

  • Dyson spheres could be built around black holes instead of stars.

Black holes can radiate incredible amounts of energy (105 more energy than the Sun) produced by the so-called “accretion disk” of gas and dust falling into the black hole’s maw. As a consequence of their spiraling and spinning motions, these materials heat up through friction to millions of degrees, emitting extremely energetic X-ray photons.

But why would an alien civilization decide to build a Dyson sphere around a distant black hole (if it weren’t “distant,” the civilization would have been “eaten” long before it managed to construct the sphere) rather than using their much closer parent star? Black holes concentrate an enormous mass into a space area that is orders of magnitude smaller than a star’s, and are therefore easier to encircle. On the downside, black holes often have bursts of activity followed by quiet periods as they consume varying lumps of matter in their disks. An alien species woulod have to protect their orbiting structures from the huge explosions that might destroy them.

  • Dyson spheres could be circling the husks of sunlike stars known as white dwarfs.

Every star has a finite lifetime. If a civilization arose around a typical sun-like star, then someday that star would turn into a red giant and leave behind a white dwarf. That process would roast its solar system’s inner planets and freeze the outer ones as the white dwarf cooled off. Consequently, the civilization would have to choose between moving to another system or building a series of habitats that harvest the radiation from the remaining white dwarf. It seems unlikely that a civilization, no matter how advanced, would go through the enormous effort of traveling to another star only to build a Dyson sphere.

This allows a direct connection between stellar lifetimes and the prevalence of Dyson spheres.

If enough aliens decided to build Dyson spheres around their white dwarf homes, then astronomers should find at least one Dyson sphere in white dwarf surveys. The presence of a megastructure like a Dyson sphere around a white dwarf would absorb part of its radiation and convert it into reusable energy. Since no conversion is 100% efficient, this process would leave behind waste heat that would escape as infrared light.

Astronomers have already found many white dwarfs with excess infrared emission, usually explained as dust in those systems, not megastructures. According to a paper by Ben Zuckerman and recently accepted for publication in the journal Monthly Notices of the Royal Astronomical Society, no more than 3% of habitable planets around sunlike stars give rise to a white dwarf sphere-building civilization. Still, there are so many planets orbiting sunlike stars that this calculation only provides an upper limit of 9 million potential alien civilizations in the Milky Way.

ARE ROGUE WORLDS THE ULTIMATE ABODE FOR LIFE?

On By AlessandraIn Extrasolar Planets, S.E.T.I.1 Comment

The search for extraterrestrial life has captivated humanity for centuries. Countless questions arise in our quest to discover if we are alone in the vast universe. The Drake Equation, a mathematical formula introduced by astronomer Frank Drake in 1961, attempts to estimate the number of civilizations within our Milky Way Galaxy. However, recent scientific discoveries have unveiled a new intriguing possibility – rogue worlds. These wandering bodies, expelled from their original solar systems, may hold the potential for harboring life. In this blog post, we will explore the fascinating intersection of the Drake Equation and the enigmatic realm of rogue worlds, exploring the tantalizing notion of life beyond our home planet.

The original form of the equation is the following:

N = R* f(p) n(e) f(i) f(l) f (c) L

• N is the number of civilizations trying to communicate with us right now;

• R* is the rate of star formation in stars per year;

• f(p) is the fraction of those stars which have planetary systems;

• n(e) is the number of Goldilocks (i.e., Earth-type) planets in a planetary system);

• f(l) is the fraction of habitable planets that are inhabited;

• f(i) is the fraction of inhabited planets that possess intelligent technological civilizations;

• f (c) is the fraction of intelligent technological civilizations that choose to emit detectable signals;

• L is the length of time signals will be sent.

The first three factors are astronomical, the fourth and fifth are biological, and the last two factors are social. There are several issues with the equation. Among these:

(1) The uncertainties are large enough for the astronomical factors and increase as one progresses from the astronomical to the biological to the social.

(2) Most factors depend on theoretical insights of star and planet formation, new discoveries about exoplanets, and varying subjective opinions on the evolution of life and intelligence. The presumed longevity of civilization must also be taken into account.

(3) The equation has many hidden assumptions: a uniform star formation rate (SFR) over the Galaxy’s lifetime and a steady state of civilization birth and death. 

(4) No matter what value one chooses for R*, the assumption is always that a habitable planet must have a star. However, rogue worlds (bodies that have been thrown out of their own nascent solar system) wander around the Galaxy unattached to a star.

This last item has recently awakened great interest in the scientific community.

Theoretical calculations (Imagined Life, by James S. Trefil and Michael Summers, 2019) suggest that:

“[…] the number of rogues might be between twice and thousands of times the number of conventional planets. Interstellar space must be littered with them!”

Also, rogue planets need not be uninteresting ice balls with no life and energy. Lacking direct radiation from a star, a world can be heated by the residual power from its formation and the radioactive decay of elements in its interior. If provided with one or more moons, the planet can draw energy from a process known as tidal heating (which is responsible for the subsurface oceans on some of Jupiter and Saturn’s moons).

All in all, rogue planets can be compared to (Imagined Life by James S. Trefil and Michael Summers, 2019):

“[…] houses whose lights have been turned off but whose furnaces are still operating.”

Interestingly, rogue planets had been predicted as early as the 1930s by American horror and S.F. author Howard Phillips Lovecraft.

In his short story: The Haunter of the Dark, he wrote:

“[…] remember Yuggoth, and more distant Shaggai, and the ultimate void of the black planets… […].”

When the planet Pluto had just been discovered by Clyde Tombaugh (1906-97) at Lowell Observatory (Flagstaff, Arizona), he wrote another short story: The Whisperer in Darkness.

Here are a few quotes: 

“[…] Their main immediate abode is a still undiscovered and almost lightless planet at the very edge of our solar system – beyond Neptune and the ninth in distance from the [S]un. It is, as we have inferred, the object mystically hinted at as ‘Yuggoth’ in certain ancient and forbidden writings; […] I would not be surprised if astronomers become sufficiently sensitive to these thought-currents to discover Yuggoth when the Outer Ones wish them to do so. But Yuggoth, of course, is only the stepping-stone. The main body of the beings inhabits strangely organised abysses wholly beyond the utmost reach of any human imagination.”

And also:

“[…] Those wild hills are surely the outpost of a frightful cosmic race – as I doubt all the less since reading that a new ninth planet has been glimpsed beyond Neptune, just as those influences had said it would be glimpsed. Astronomers, with a hideous appropriateness they little suspect, have named this thing ‘Pluto.’ I feel, beyond question, that it is nothing less than nighted Yuggoth […].”

What would life be like on a rogue planet?

According to Imagined Life, by J.S. Trefil and M. Summers:

“It’s dark. Not midnight-on-a-side-street dark, but trapped-in-a-cave dark. And no wonder—there’s no sun in the sky, for this is a rogue world, one that circles no star. There is a moon up there somewhere, but without a source of light for it to reflect, it’s just a darker patch in the sky. Whatever life forms live on this planet had better be able to see in infrared because there’s simply no other light to be had. You’re wearing infrared sensors, fortunately, and you spot a few of these creatures scurrying back to the planet’s subterranean tunnels, where they can bask in the heat emanating from the planet’s interior. […]”

Life on a dark planet has been described by British author Arthur C. Clarke in his 1950 short story: A Walk in the Dark:

“[…] Here at the edge of the Galaxy, the stars were so few and scattered that their light was negligible. […]” 

“[…] Here at this outpost of the Universe, the sky held perhaps a hundred faintly gleaming points of light, as useless as the five ridiculous moons on which no one had ever bothered to land. […]” 

“[…] No one could deny that the tunnels out in the wasteland were rather puzzling, but everyone believed them to be volcanic vents. Though, of course, life often crept into such places. With a shudder, he remembered the giant polyps that had snared the first explorers of Vargon III […]

The Drake Equation is not meant to give a precise answer but to stimulate scientific discussion and exploration. It is based on several factors that affect the likelihood of finding intelligent life, such as the rate of star formation, the fraction of stars with planets, the fraction of planets suitable for life, and the fraction of civilizations that develop radio technology. Each factor is multiplied by the previous one, resulting in the number of detectable civilizations in our galaxy. However, many of these factors are uncertain, and different assumptions can lead to different outcomes. For example, some estimates suggest that there could be millions of civilizations in our Galaxy, while others suggest that we might be the only one.

According to a recent study, under the strictest set of assumptions, where life forms between 4.5 billion and 5.5 billion years after star formation, there are likely between four and 211 civilizations in the Milky Way today capable of communicating with others, with 36 the most likely figure. Another study yielded two main results: an optimistic one and a pessimistic one. In the optimistic situation, the researchers suggested the aforementioned 42,777 communicating extraterrestrial intelligent civilizations (CETIs) with an error margin of plus 267 and minus 369, and they would need to survive 2,000 years on average to communicate with us.

The Drake Equation is a fascinating way to explore the possibilities of extraterrestrial life and communication. It helps us understand what we know and don’t know about our place in the universe. It also inspires us to keep searching for signs of other civilizations and to wonder what they might be like.

Read more about this topic in this post and this other post.

IS THE UNIVERSE AN AWFUL WASTE OF SPACE?

On By AlessandraIn Extrasolar Planets, S.E.T.I.

“The universe is a pretty big place. If it’s just us, it seems like an awful waste of space.” 

This quote is attributed to Carl Sagan from his novel Contact (1985). It is often interpreted as reflecting Sagan’s optimism and belief in the possibility of extraterrestrial life. He strongly advocated for the search for extraterrestrial intelligence (SETI) and believed that the discovery of intelligent life beyond Earth would have profound implications for humanity.

In other words, Sagan suggested that if the Universe is so vast and we are the only intelligent life in it, it would be a shame to waste all that space on just one civilization.

A recent estimate (Conselice C.J. et al. 2016) says the observable Universe contains two trillion – or two million million – galaxies. Of course, this is a huge number, which math buffs can probably better appreciate if I translate it into scientific notation:

two trillion = two million million = one thousand billion = 2 x 1012

Even if we neglect 99.9999% of the Universe and consider only the Milky Way, we are left with a staggering number of about 100 to 400 billion stars.

Of course, these hundreds of billion stars vastly differ in age, mass, and chemical composition.

According to the stellar luminosity function:

A small percentage of stars are massive, young, and very bright (the so-called O, B, and A spectral types, with colors ranging from ultraviolet/white to blue);

A relatively large number of stars are medium-sized (the F and G spectral types, yellow to orange in color). Our “dull” Sun is one of them;

The majority of stars are small, old, low-mass stars (the K, M spectral types, a.k.a. red dwarfs);

Many stars are brown dwarfs (dark, spherical lumps of stellar material that never reached the star stage).

In the last few decades, roughly from the early nineties, it has become known that most, if not all, stars possess planets. Our Sun has eight major ones (excluding the KBOs or Kuiper Belt Objects). The former planet Pluto, now demoted to “dwarf planet,” is one).

Just like stars, planets also show a vast range of types.

I found a helpful classification in Imagined Life: A Speculative Scientific Journey among the Exoplanets in Search of Intelligent Aliens, Ice Creatures, and Supergravity Animals by James S. Trefil and Michael Summers. We can envisage the following kinds of exoplanetary environments as the most promising for alien hunters:

(1) Goldilocks Planets: planets like Earth, located at a distance from their star that allows them to have oceans of liquid water on their surface for extended periods;

(2) Subsurface Ocean Worlds: planets on which oceans of liquid water are bounded below by solid rock and above by ice. Examples in our solar system: the planet Pluto and several moons of Jupiter, Saturn, Uranus, and Neptune);

(3) Rogue Worlds: planets without a parent star. Such planets have been ejected from their solar system of origin and now wander through space. An example is OTS 44, a free-floating planetary-mass object located at 550 light-years, with approximately the mass of Jupiter;

(4) Water Worlds: planets with no dry land at all. That’s what a post-apocalyptic Earth would look like. (See, e.g., Kevin Reynolds’ 1995 movie Waterworld);

(5) Tidally Locked Worlds: planets that always present the same face to their star, much as the Moon does with Earth. Their peculiarity is that one side is perennially hot, while the other is an eternal Antarctica;

(6) Super-Earths: planets whose size falls between Earth and Neptune. Given their mass, the main characteristic of these planets is their intense gravity. Creatures must live in oceans or evolve a strategy to deal with this crushing force. A nice fictionalization of this is Edmond Hamilton‘s Starwolf series (1967-68), where Morgan Chane, the son of a human missionary family, grows up in a heavier-than-Earth world.

If these worlds exist, and there’s a tiny chance some might be inhabited, well… I want to see them. I’ll probably never do it in person (sadly, I’m not an astronaut). However, I can still dream about them, hoping someone will get there someday.

I wish someone to be able to say, just like the replicant Roy Batty in Ridley Scott’s 1982 movie Blade Runner:

“I’ve seen things you people wouldn’t believe.
Attack ships on fire off the shoulder of Orion.
I watched C-beams glitter in the dark near the Tannhauser Gate.
All those moments will be lost in time, like tears in the rain.
Time to die.”

Read more about this topic in this post and this other post.