13 Disturbing Paradoxes That Scientists Are Terrified By

<h4>

13 Disturbing Paradoxes That Even Scientists Are Terrified By</h4>

What scares you most about science? Is there any one theory or prediction that really keeps you up at night? And have you ever wondered whether, actually, there are some problems out there that truly could ruin everything? In our new series, we strive to analyze the biggest and most significant unknowns surrounding the key issues of science, technology, life, and everything. 

This is Unveiled, and today we’re taking a closer look at ten disturbing paradoxes that even scientists are terrified by.

The Fermi Paradox

Let’s start with one of the biggest and most all-encompassing. Thanks largely to science fiction, the Fermi Paradox has infiltrated into the mainstream in recent times… but that hasn’t done much to dilute the more ominous implications that it carries in the real world.

In simple terms, it’s a thought experiment that questions the apparent contradiction between the vastness of the universe and the lack of evidence of extraterrestrial life. It was first posed by the influential, twentieth-century physicist Enrico Fermi in 1950 - legend has it during an otherwise quite casual lunchtime conversation with his colleagues at the time. We can think of the paradox as being based on several assumptions. First, the universe is billions of years old, giving ample time for life to evolve. Second, stars are abundant, providing countless potential sites for life-bearing planets. Third, technology can advance over time, enabling civilizations to travel through space. With all of these things in mind, however, and as Fermi himself is said to have momentously exclaimed, where is everybody? Why isn’t the universe teeming with alien life, when all the markers suggest that it should be?

As such, and in the years since, the Fermi Paradox has given rise to a number of potential solutions, some of which are pretty scary. First, there’s the Zoo Hypothesis, suggesting that advanced civilizations are actively observing our planet… but that they deliberately refrain from making contact, all to prevent us from developing too quickly or interfering with their plans. In this sense, alien life is all around, it’s just that we’re inescapably caged by it. An extension to the Zoo Hypothesis - the Lab Hypothesis - takes it one stage further, too, suggesting that not only are we being watched all the time, but we’re also being experimented on by those that are watching.

Next, there’s the Rare Earth Hypothesis. This theory claims that Earth's unique combination of conditions is exceptionally favorable for life; and therefore that the vast majority of other planets may not be capable of supporting complex organisms. On the face of it, this perhaps isn’t quite so frightening as us all unknowingly swimming around in an alien petri dish… but many scientists are at least concerned by the potential for Rare Earth. If true, it would mean that we are entirely at the mercy of our unlikely circumstances; that we’ll probably never be able to move away from Earth, and that we’re therefore doomed to extinction one day, no matter what we do.

And, finally, there’s the relationship between the Fermi Paradox and the Great Filter. Generally, the Great Filter suggests that there are various, insurmountable obstacles that prevent most civilizations from reaching advanced technological levels. These obstacles could include cosmic disasters, resource depletion, or self-destruction. And, ultimately, that’s why the universe apparently isn’t full of life. We must then consider whether humans have passed through the Great Filter… or whether it still lays ahead for us? And, statistically, the chances are slim for the former. What’s much more likely is that the Fermi Paradox proves that the Great Filter lies ahead, and that we’re all inevitably doomed as a result.

The Grandfather Paradox

In general, time travel is easily one of the first ports of call whenever paradoxes are on the table. There’s just so much that can go wrong, there’s such a lot of weirdness, whenever the potential to bend and shape time is considered. But, still, the Grandfather Paradox is one of the best known and one of the most dangerous.

In short, it asks: What would happen if time travel were possible, and you traveled back in time and did something to prevent your own existence, such as killing your grandfather before your parent was conceived? The problem being that, if you did that, you then wouldn’t be able to travel back in time to kill your grandfather in the first place… because you don’t exist. All of the above will have effectively erased itself. It’s a logical contradiction; a clear inconsistency within the idea of cause and effect, which is otherwise vital to how we understand the universe.

The term "Grandfather Paradox" doesn't have a clear origin but was popularized in science fiction and general discussion about the implications of time travel, dating back to at least the early twentieth century. There have been a number of proposed solutions put forward, although one, in particular, is somewhat worrying.

It could be that any action taken by a time traveler would be a part of history all along; which means you could never change events to prevent your birth because any attempt would fail… or cause an alternate series of events leading up to your existence regardless. It’s probably the neatest way out of the problem, but it also implies a wholly deterministic universe where free will doesn’t exist and any semblance of choice is an illusion.

Of course, right now, time travel doesn’t exist, so perhaps it isn’t worth fretting over. However, the profound philosophical questions are still pushed front and center, simply due to the fact that the paradox can be thought up. We can ask ourselves; is every moment predestined? Are we ever truly in control of our actions, or even our thoughts? And, naturally, should we really be trying (or even hoping) to travel in time at all? 

The Cobra Effect

Otherwise known as a perverse incentive, the Cobra Effect is traditionally related to the science of economics, although its implications are wide. And, ultimately it’s due to it being a seemingly universal rule as to why it can often feel a little… unsettling.

The Cobra Effect is a term used to describe an unintended outcome that is the opposite of the intended outcome. It occurs when an incentive created to solve a problem ends up exacerbating that very issue due to unforeseen consequences. The phrase is said to refer to a historical incident during British rule in India. So the story goes, to reduce the number of venomous cobras, authorities at the time offered a bounty for every dead snake brought in by citizens. At first, it worked… but then it led to an increase in the cobra population. Why? Because people began to breed cobras in order to collect the bounty. Finally, when this was discovered and the reward was ended, the impromptu cobra breeders released their now-worthless snakes into the wild, meaning that at the close there were actually more snakes than ever.

The effect isn’t just about snakes, though. It represents any situation where interventions have almost inescapably negative outcomes. As well as economics, it’s rooted in behavioral psychology - especially highlighting humankind’s habit for social shortsightedness. As a paradox, it challenges (even rubbishes) the belief that well-intentioned policies will always have positive outcomes. Arguably the most pervasive, real-world example is the modern phenomenon of antibiotic resistance. Ever since they were introduced, antibiotics have proven essential for treating infections… but today their overuse has led to the emergence of antibiotic-resistant bacteria, rendering once-life-saving drugs increasingly ineffective. We also face similar dilemmas with the emergence of artificial intelligence; where algorithms designed for good might perversely optimize for harmful outcomes.

Elsewhere, analysts worry about how cash injections can eventually distort markets; environmentalists ponder if conservation efforts could actually harm ecosystems; public health officials debate whether certain campaigns inadvertently promote risky behaviors. Overall, the Cobra Effect shows our always limited ability to accurately predict what will happen in a complex system. It warns us that even the most well-meaning actions can have dire results if we don't fully understand every aspect they touch upon. All in all, it’s a seeming fact of life that can leave you feeling quite powerless.

The Bootstrap Paradox

For our second (and last) time travel-specific phenomenon, the Bootstrap Paradox has proven a head-scratcher of the highest order for decades. The term perhaps came to prominence following the publication of sci-fi writer Robert A. Heinlein’s 1941 short story, "By His Bootstraps”. In it, a man travels back in time and gives himself the knowledge necessary to invent the time machine he used to travel back in time. More broadly, the paradox also takes its name from the expression "to pull oneself up by one's bootstraps”, implying a self-contained process… and usually an impossible action.

In general, then, the paradox refers to any situation where an object or piece of information is sent back in time and becomes trapped in an infinite cause-and-effect loop, wherein it has no discernible origin. 

Imagine someone travels back in time with a scientific paper containing groundbreaking equations. They give this paper to a young scientist who then publishes these findings as their own work. As time progresses, the equations become famous until another person decides to take them back in time again - repeating the cycle endlessly. Where did those equations originally come from if they were never independently created? Similarly, consider going back in time and giving William Shakespeare a copy of "Hamlet" before he writes it. Where did "Hamlet" originate? Or taking a wheel back to the stone age; how was the wheel invented?

While closely related to other temporal paradoxes like the Grandfather Paradox, the Bootstrap Problem focuses specifically on informational or physical anomalies rather than changes to timelines. On the one hand, it arguably suggests that time travel will never be possible, because such informational headaches should be all around us if it were. But, on the other, could it imply not only that time travel is possible, but that we’re all hopelessly trapped within the fixed parameters of it, by default? 

It’s an idea that challenges foundational principles. The very nature of science relies on traceable chains of evidence and causation. An uncaused event simply doesn't fit… and that’s enough to leave even the smartest of us at a complete loss.

Infinite Divisibility

The notion of infinity is easily one of the most fascinating in all of science and philosophy. But, depending on how you look at it, it can either prove a source of immeasurable wonder… or it can send you spiraling into never ending despair.

In general, infinite divisibility is the seeming paradox that suggests an object could be divided in half an infinite number of times without ever reaching an indivisible limit. Theoretically, it shouldn’t even matter if there really was a bottommost unit for whatever it was you were dividing into two… the divider should still be able to half and half and half again, forever. 

It ties back to ancient Greece with what have come to be known as Zeno's paradoxes. The most famous one - Achilles and the Tortoise - tells us about a race where the swift Achilles gives a tortoise a head start. But, although Achilles runs much faster, by the time he reaches where the tortoise was, it has moved forward slightly. According to Zeno’s reasoning, since there are infinitely many points Achilles must reach where the tortoise has been before overtaking it, he can never actually pass it. This introduces the idea that space could be infinitely divisible, while at the same time remaining logically absurd.

More practically, it’s something that collides with the principles of quantum mechanics. Atoms were once thought to be indivisible - hence their name derived from 'atomos', which means “uncuttable” - but, of course, now we know that, actually, they consist of smaller particles like protons and electrons. We then know of further subatomic entities, like quarks and leptons. But could we, due to infinite divisibility, keep going? Some believe that there must be fundamental limits - such as at the Planck length - beyond which space-time really doesn’t have any physical meaning and cannot be further divided. But that’s also a logical stumbling block… because, again logically, something can always be halved.

Mathematically speaking, numbers certainly are infinitely divisible; you can always find another fraction between two numbers no matter how close they are together. But the fact is that when that’s applied to physical reality - such as for distance, matter, or even for time - it becomes troublesome. Troublesome to the point that, somewhat ironically, no one could ever spend quite enough time trying to work it all out.

Hilbert's Hotel

At the other end of the scale to infinite divisibility… there’s Hilbert's Hotel. This is an imagined hotel with an infinite number of rooms. Such a place should always have space for new guests… but at the same time could reasonably be described as being always full. On the one hand, every room is occupied; on the other, the hotel can still accommodate more travelers. Which is mind-bending, even to begin with. But it goes deeper, still.

Consider the role of the Hilbert’s Hotel manager. Their establishment is already infinitely full, but someone new arrives. They can accommodate them by quite simply asking everyone who’s already staying at the hotel to move one room along. Room 1 moves to Room 2, Room 2 moves to 3, and so on forever. The new guest takes the newly vacant Room 1. Even though it seems like there should be no space left, there always will be an infinite amount of space to offer. The hotel wouldn’t even buckle if an infinite number of guests turned up at its door. Or an infinite number of planes flew in carrying an infinite number of guests who all needed a room. Or an infinite number of planes flew into an infinite number of airports… and so on.

This particular representation is attributed to one David Hilbert, a German mathematician, who’s said to have first voiced it in the mid-1920s. But, there are a number of other, similar models, including Borges' Infinite Library. Created by the Argentine writer, Jorge Luis Borges, for his 1941 short story, “The Library of Babel”, this is an endless world filled with books containing every possible combination of letters. In practice, this means that the library houses an infinite amount of knowledge and gibberish alike. Open any book, and you may well find whatever’s written in it to be indecipherable. But, equally, you might find one word that makes sense; or one sentence; one paragraph. And, ultimately, in amongst all the nonsense, there should also (inevitably) be every possible arrangement of letters to convey meaning. There will even be many (technically infinite) works of literary genius. One other way of approaching this is via what’s known as the Infinite Monkey Theorem, which suggests that given an infinite number of monkeys hitting keys at random on typewriters, over the course of an infinite amount of time, they will almost surely type out any given text - even the complete works of Shakespeare.

As fun as all this is to contemplate, however, it’s also cause for some to lose sleep. Returning to Hilbert’s Hotel, and if it never stops… then what does that say about the so-called fundamentals of physics? For example, the total energy required to run the hotel would also be infinite, therefore violating the laws of thermodynamics. What’s more, the process of organizing an infinite number of guests requires an infinite amount of time and resources… but can any computational process handle that, in reality? Even in terms of pure space, and even if the universe were proven beyond doubt to be infinite, in itself, then could there ever be enough space to accommodate Hilbert’s Hotel? Which infinity wins out? How is anything ever resolved, if it simply carries on, and on… and on?

The Twin Paradox

Whenever there’s talk of paradoxes, it isn’t long before one Albert Einstein is mentioned. And here’s where possibly the most famous scientist of all time really enters the fray - thanks to a thought experiment (and physical reality) that’s all tied up with his theories of special relativity.

Picture identical twins, Bob and Alice. Bob stays on Earth while Alice travels on a spaceship to a distant star and back again. According to the theory of special relativity, time dilation occurs for objects in motion relative to an observer. Time isn’t absolute but relative; it can pass at different rates for different observers depending on their relative speeds. In the context of the fate of our twins, this ultimately means that time passes slower for Alice on her spaceship (which is perhaps approaching lightspeed) than it does for Bob on Earth.

From Bob’s perspective, Alice's journey to wherever it is she’s going could take many years. However, from Alice's perspective, zooming through space, although still apparently aging at the same rate… it’s a journey that’s taken much less time (when she returns to Earth) due to time dilation. Therefore, when Alice arrives back, she’s younger than Bob, despite being the same age when they parted ways. In extreme cases, the spacefaring twin may even have missed the entirety of their sibling’s life, decades of real-time experiences, despite themselves feeling as though they’ve only been away for a short time.

While this perhaps isn’t a paradox with any immediately terrifying practical implications, it is still something that can feel deeply unsettling. It can evoke existential unease because it shows that our most basic understanding of reality - time itself - isn’t universally consistent. It doesn’t flow the same for everyone or everything… which is something like having the cosmic rug suddenly pulled from under your feet.

Of course, there are some implications for space travel, too. The Twin Paradox raises questions about the effects of long-duration space travel on astronauts. Technologically speaking, we are still a long way from this stage… but if humans ever were capable of moving between stars, then the effects of time dilation could very quickly ruin any sense of a link or continuity from one world to another. It’s one way, in particular, that our species would intrinsically change if we ever did launch off of Earth for good.

Schrödinger’s Cat

Along with the Fermi Paradox, Schrödinger’s Cat is a prime example of a complex, theoretical concept that has really caught on in the wider world. It’s another that science fiction loves to delve into. And, by now, it’s a well-known setup, but let’s recap.

First, we have our cat, but the cat is then placed in a sealed box along with a radioactive atom. The atom has a fifty percent chance of decaying within an hour, triggering a mechanism that will release poison and kill the cat. But, here’s the thing. According to quantum mechanics, until the box is opened and the state of the atom is observed… the atom exists in a superposition of states. This means that it’s both decayed and not decayed at the same time. And, as a result, the cat is also in a superposition of states; it’s both alive and dead simultaneously. That is, again, until the box is opened, and the fate of the cat is observed.

The above is a famous thought experiment designed by the Austrian physicist Erwin Schrödinger in 1935, legend has it during a conversation with Albert Einstein. It illustrates a paradox of quantum mechanics. Ideas on quantum superposition suggest that any given particle only becomes that particle when it is observed; that, before it collapses into itself, it can exist in multiple states. But, what does that mean as to its true nature?

The paradox highlights many things. One, a fundamental problem in quantum mechanics of how and when a quantum system collapses, transitioning it from a superposition of states to a single, definite state. Two, it challenges our classical understanding of reality itself, suggesting that objects are wholly indefinite and therefore much more complex and mysterious than we currently understand. And, three, some interpretations of Schrödinger's Cat suggest that consciousness plays a role, as well. For example, if we weren’t conscious to observe… then what, if anything, would happen next? This, in turn, raises questions about the nature of consciousness and its relationship to the physical world. 

And, ultimately, whenever you find yourself doubting even your most inherent physical experiences, even your most in-built thoughts and intuitions, then that can be a pretty scary place to be.

The Sorites Paradox

Also known as the Paradox of the Heap, the Sorites Paradox is a philosophical puzzle that deals with vagueness and the problems it presents. In its most popular form, it revolves around a heap of sand. If you have your heap of sand and remove one grain at a time, then at what point does it stop being considered ‘a heap'? Conversely, if you add one grain to another, then another and so on, then when do your grains become ‘a heap'? 

The word "sorites" derives from the Greek for "heap”, but this is about more than just sand. It showcases how the imprecision of language can lead to logical absurdities. Sticking with sand for now, the key issue is that there seems to be no clear answer, because one grain of sand never makes much difference. However, we know intuitively that there must be some point at which we’d no longer consider our collection of grains to constitute a heap - or vice versa. In another variation, it’s known as the Bald Man Paradox; because, at what point does a man with a gradually decreasing number of hairs become bald? Either way, it exposes problems in defining terms where there are borderline cases without sharp boundaries. Whenever there is vagueness present which, in truth, is most of the time… because so much of language and so many of our communication methods are, ultimately, up to interpretation.

For scientists - and indeed, for anyone interested in precision - the Sorites Paradox is concerning because many scientific concepts rely on clear definitions and thresholds (for example, a boiling point). But, if such points are merely vague constructs when you really think about them, without any truly inarguable before-and-after moment, then it becomes extremely challenging (or even impossible) to establish facts.

From another point of view, the Sorites Paradox challenges the concept of gradual change. In fields like biology or psychology where categories (like illnesses or mental health conditions) often exist along continua without clear dividing lines… the problem forces us into sometimes difficult conversations about classification systems. About how to differentiate (and therefore diagnose) between one medical complaint and another, for example.

Similarly, it’s a paradox that might be applied to decisions over law and order, right and wrong, justice and injustice. It has an effect over social sciences such as demographics; over finance and money, where pennies and cents eventually do make pounds and dollars; over education and the question of precisely when someone is qualified enough to fulfill a certain role. In all cases, the categorization criteria can seem arbitrary… and yet it will inevitably carry significant implications. Be that for research, medical treatment, policy making, funding approval… the list is endless. And that’s why the Sorites Paradox is a source of constant concern, and even fear.

The Omnipotence Paradox

If you ever find yourself questioning the existence of God, then perhaps this is the paradox for you, in particular. The Omnipotence Paradox poses a fundamental challenge to the concept of an omnipotent being or creator. It asks the question: can an omnipotent being create a stone that they cannot lift? If they can create such a stone, then their omnipotence is limited by their inability to lift it. However, if they cannot create such a stone, then their omnipotence is limited by their inability to create it.

For some, this is simply enough to prove that God doesn’t exist. It’s a logical conundrum that just doesn’t fit with the beliefs and stories regarding an all-seeing, all-powerful, supernatural force. However, the majority of scientists aren’t necessarily even thinking about the problem from the point of view of some kind of supreme being. Instead, this is a seemingly irrefutable puzzle that asks some pretty tricky questions about the nature and limitations of power, with a potentially wide-reaching (and even existential) impact.

Consider humankind’s long-running bid to develop a theory of everything in physics. In short, it boils down to an attempt to finally explain reality in full. To leave nothing unknown, and to reach a rule that can (and will) explain every possible occurrence. But, even in our wildest dreams, is that ever really achievable? The Omnipotence Paradox could suggest that no, it isn’t. It could imply that logic itself has limits… which is a potential death knell to scientific inquiry, in general. It  then poses questions about whether we can ever fully comprehend or explain our universe using reason alone, since reasoning seems capable of leading us into contradiction. At best, that’s a headache for scientists. At worst, it’s the realization that nothing ever actually matters.

The Omnipotence Paradox also throws a seemingly irretrievable fly into the ointment for any future technology predictor, or advanced civilization forecast. With the Kardashev Scale - probably the most well-known measure of its type - there’s always, theoretically, another level above. If one entity rules over this reality, then another rules over theirs, and another over theirs, and so on indefinitely. 

But essentially, in everyday life, this is a paradox to prove that nothing is ever entirely complete, completely correct, or fully under control. There will always be a logical way to ruin it. And this inescapable lack of control can feel deeply unsettling.

Quantum Immortality

To put it mildly, we know that quantum mechanics is strange. Dial down far enough into the fabric of reality, and most of the rules we rely upon to make sense of the macro world basically crumble and self-destruct. But, and even with that as a backdrop, theories on quantum immortality are enough to really shake you up.

Here, we’re at a meeting point between thought experiments like Schrödinger’s Cat - which serve to highlight how there are multiple states at the quantum level - and what’s known as the Many Worlds Interpretation. First put forward in 1957 by the US physicist, Hugh Everett III, the Many Worlds Interpretation is a particular understanding of the multiverse. It says that every possible outcome of every quantum event does actually occur in a separate universe. This means that there are an infinite number of universes, and also implies that each one of them houses a different version of you. Typically, it’s imagined by picturing that in one universe you wore a blue shirt today instead of a red one; in another, you ate an orange instead of an apple.

However, it goes much deeper. In the more traditional understanding of life, the universe and everything, we know that we all will die at one point in the future. Death is an inevitable part of life. But, through the prism of Many Worlds, perhaps it isn’t. Quantum Immortality is a controversial and highly speculative hypothesis, but in simple terms it implies that for every potentially fatal event, there’s a branch of reality where the person that’s suffering that event survives. In fact, there should be multiple branches of reality where they survive, and only one where they die.

At first, this seems like it should be a good thing. We know that various fields of science are busily trying to achieve immortality so that we really can live forever, even in this particular timeline. But Quantum Immortality also presents some major ethical dilemmas. First, there’s a somewhat unsettling loss of human narrative at play. Our lives, as we typically understand them, are built around key moments which are essentially bookended by the most key moments of all - birth and death. But, if true, quantum immortality removes the latter, and arguably changes what it means to be human.

Even more worryingly, however, scientists and philosophers have before mused that Quantum Immortality could lead to a belief that none of our actions in the here and now have consequence - a highly dangerous notion. Equally, turn the potential paradox on its head, and we might just as well label Quantum Immortality as a quantum prison. As an overriding construct to reality that no one can ever escape from… which, in turn, leads to deep-rooted questions about the nature of free will. And about whether it ever really exists at all.

Roko's Basilisk

Perhaps no other paradox has generated quite as much modern controversy as this one has… so much so that it’s now something of a cornerstone for contemporary ideas on science and technology. Roko's Basilisk is a thought experiment that emerged from the online community, “LessWrong”, a forum for discussing future tech topics, and especially artificial intelligence. ‘Roko’ refers to the original poster on the forum; while the ‘basilisk’ is a nod to a legendary beast, king of the serpents in mythology, that’s said to kill anyone who looks into its eyes. 

In essence, Roko's Basilisk is a hypothetical scenario involving an all-powerful AI that comes into existence in the future. This AI is supremely dedicated to achieving its goals and ensuring its own creation - as it’s predicted (in general) that many AIs will be. But, now’s when things get scary. The paradox suggests that this particular AI would punish those who knew about its possible existence but did nothing to help it achieve its goal. In other words, just by knowing about this potential AI god-like entity (the Basilisk), you might be at risk of future retribution unless you make it a reality. And, naturally, as soon as talk of Roko’s Basilisk comes up… then those involved are aware of it and, theoretically, are at risk unless they act.

The circular nature of Roko’s Basilisk reportedly inspired panic in some who read the original post, and discussion of it was even banned on “LessWrong” for a number of years. As such, it’s been variously described as a dangerous thought experiment, as it implies that even our own thoughts aren’t safe in the face of the rise of AI. That we’ll one day be so totally at the mercy of machines, that we’ll be inescapably punished - even tortured - for past actions (or inactions) that we could (and can) do very little about. It might also be labeled as an information hazard, as it is theoretically information that’s hazardous to know. 

More broadly, the Basilisk has been compared to Pascal’s Wager. Attributed to the seventeenth century, French philosopher, Blaise Pascal, it’s a proposed gamble on belief in God - arguing that if God exists and you believe, you gain everything, such as, eternal life… but if you don't believe and God exists, you lose everything, via eternal damnation. So logic says that it’s best to live as though you do believe, just in case.

Unsurprisingly, Roko’s Basilisk is by no means the only AI-centric paradox out there, either. Another especially troubling example is the Paperclip Maximizer. Proposed in 2003 by the Swedish philosopher, Nick Bostrom, it suggests that an AI designed to make paper clips could ultimately decide to make paper clips until the universe is nothing but paper clips. Or it could deem it best to make paper clips out of the atoms inside us, the otherwise useless humans, as per its one-track perspective.

The Dark Forest

With the Dark Forest Hypothesis, we at once have a potential solution to another paradox - the Fermi Paradox - and the outline for a separate paradox, relating to cause, effect, action and intent.

The Dark Forest is primarily a thought experiment that explores the potential dangers of revealing oneself to other civilizations in the vastness of space. It was proposed by the Chinese science fiction writer Liu Cixin, in his novel "The Dark Forest" - the second installment in a trilogy starting with “The Three-body Problem”.

The theory is based on the premise that the universe is a dark forest, where every civilization is a hunter with a weapon, lurking in the shadows, trying to avoid detection. Or, at least, that’s what every successful civilization is doing. The reason for this is simple: if a group reveals its existence by emitting signals, or engaging in any other activities that can be detected by others… then it is immediately putting itself at risk of being attacked and destroyed. As there’s no room for trust or cooperation in the Dark Forest... any civilization that is discovered by another is assumed (by them) to be hostile and must therefore be eliminated. This leads to a chilling conclusion: the only way for a group to survive is for them to remain hidden and silent. And, as a result, the Dark Forest is now a leading, potential solution to the Fermi Paradox - which asks, where are all the aliens?

Clearly, there are a number of reasons why many are scared by this. It suggests that the universe is simply a much more dangerous place than may have we ever imagined. That it’s a cold and unforgiving wilderness where only the most paranoid and ruthless can survive. But, also, because we know that, via radio communication and even probes such as the Voyagers, humankind has before actively sought to make its presence known… then it implies that we’ve already sealed our own doom. That there’s no rowing back from the actions we’ve already taken.

Finally, though, some interpret the Dark Forest as being indicative of the pitfalls to human nature itself. In any situation, not just with regard to hypothesized alien contact, we project our own behavior onto others and assume that  they'll act as we do. To some degree, it might be viewed as a positive mindset. But ultimately, for so long as there’s even the possibility for a negative, destructive or even fatal outcome… then that’s what will happen time and time and time again. In short, while no one asked to be in the Dark Forest, no one can escape it, either.

So, how’s your brain? Muddled, befuddled… or possibly enlightened? Air your thoughts in the comments. Be sure to tell us which paradox you found most interesting. Or most terrifying! And, if you know of a paradox that we haven’t covered, or there’s any that you’d like to know more about, then let us know!