Why Interstellar Travel Is More Terrifying Than You Think | Leonard Susskind

Added: 2026-05-24

[00:00:00]Humanity dreams of reaching the stars.

[00:00:03]This is fundamental to how we think about our future, about what intelligence can accomplish, about what advanced civilizations become. We imagine spreading across the solar system first, establishing colonies on Mars and the moons of Jupiter, mining asteroids, building habitats throughout our stellar neighborhood, and then beyond to other star systems, to exoplanets orbiting distant suns, eventually to thousands of worlds, millions of worlds, colonizing the galaxy over millions of years, becoming a truly space fairing civilization that has transcended ed the limitations of a single planet and mastered the challenge of interstellar travel. This vision drives space exploration, inspires science fiction, shapes how we think about humanity's long-term survival and ultimate potential. We assume that with enough time, enough technological advancement, enough determination, interstellar travel will become routine, will become achievable, will transform from impossible dream to practical reality the way air travel transformed from fantasy to everyday experience over the course of a century. We look at the exponential growth of technology at how rapidly we've advanced from the Wright brothers to the International Space Station and we extrapolate forward imagining that the same kind of progress will eventually make the stars accessible will turn the vast distances between stellar systems into something we can cross, something we can conquer, something we can overcome through engineering and physics and sheer human ingenuity.

[00:01:50]But I've spent my career studying the deep structure of spaceime, working on relativity and cosmology and the fundamental limits that physics imposes on what's possible. And I can tell you something that most people never fully absorb, never emotionally process, never truly confront.

[00:02:12]Interstellar travel is not like any other technological challenge humanity has faced. It's not just difficult or expensive or dangerous in the conventional sense. It's something fundamentally different. Something that strikes at the very nature of space and time and causality.

[00:02:30]Something that might remain forever beyond practical capability. Not because we're not clever enough or determined enough, but because the universe itself, the structure of spaceime itself, imposes barriers that are not technological, but physical. Not engineering challenges, but fundamental limits on what matter and energy and information can do. When attempting to cross the vast emptiness between stars, the distances are incomprehensibly large, larger than human intuition can really grasp, larger than any distance we've experienced in our evolutionary history or our technological development. The nearest star system beyond our sun is Alpha Centuri, about 4.4 light years away. That means light traveling at the maximum speed that causality permits. The speed at which information propagates through spaceime takes 4.4 years to cross that distance.

[00:03:30]And light moves at 300,000 km/s.

[00:03:34]Fast enough to circle the Earth 7 and 1/2 times in 1 second. Fast enough that we don't notice any delay in everyday life. But even at this extraordinary speed, the fastest speed possible, crossing the distance to the nearest star takes over four years. and that's the nearest star. Most stars are much further away. The majority of stars in our galaxy are hundreds or thousands of light years distant. The galaxy itself is about 100,000 light years across.

[00:04:05]These distances are so enormous that even traveling at light speed, which nothing with mass can actually do, would require time scales far longer than human lifespans, far longer than civilizations persist, far longer than any organized human endeavor has ever maintained continuity. This is the first brutal reality of interstellar travel.

[00:04:29]the sheer scale of the distances involved. Distances so vast that they make Earth moon travel look like a walk across the room. Distances that dwarf everything in human experience.

[00:04:43]Distances that impose fundamental constraints on what's possible, what's achievable, what any civilization could actually accomplish when attempting to physically cross them. Let me walk you through what it would actually take to reach even the nearest stars. what the physics demands, what the engineering requires, what the human and social and civilizational costs would be. Because understanding these realities, really absorbing what they mean, reveals why interstellar travel might be fundamentally different from every other frontier humanity has crossed. why it might represent an insurmountable barrier. Not because we lack the technology, but because spacetime itself resists being crossed on these scales.

[00:05:31]Because the universe is structured in ways that keep intelligent civilizations isolated, separated, unable to truly expand beyond their local stellar neighborhoods despite all their technological capabilities.

[00:05:46]The fundamental problem is speed, or rather the lack of speed we can achieve relative to the distances that need to be crossed. Chemical rockets, the kind we currently use for all space travel, are hopelessly inadequate for interstellar journeys. They achieve velocities measured in kilometers/s, which sounds fast until you realize that light travels 300,000 km/s, making rocket velocities less than 110,000th of light speed. At current rocket velocities, reaching Alpha Centuri would take tens of thousands of years, time scales longer than all of recorded human history, longer than our species has existed in anything resembling modern form, making such a journey completely impractical, completely beyond what any human or even posthuman civilization could realistically attempt. So clearly we need much higher velocities velocities approaching significant fractions of light speed, which immediately means we need propulsion systems far beyond anything chemical rockets can provide. Nuclear fusion, if we can make it work efficiently for propulsion, might push velocities to a few% of light speed, maybe one or two or 3%, which would reduce the journey time to Alpha Centuri to something like 150 to 200 years.

[00:07:16]This is still multiple human lifetimes, still requiring either generationships where multiple generations live and die during the voyage, or some form of suspended animation or cryogenic preservation that keeps travelers alive but not conscious during the journey, or radical life extension that allows individual humans to survive journeys lasting centuries. Each of these approaches faces enormous challenges not just technological but biological and psychological and social generation ships require maintaining a stable sustainable closed loop ecosystem for centuries.

[00:07:57]Maintaining technological and social continuity across generations who will live and die without ever seeing Earth or their destination.

[00:08:06]maintaining motivation and purpose and cohesion among populations who were born on the ship and will die on the ship without ever experiencing anything else.

[00:08:17]This is psychologically unprecedented.

[00:08:20]It's asking human beings to accept lives spent entirely in transit, to raise children knowing they'll never reach the destination, to maintain cultural and technological knowledge across generations in artificial environments, to avoid social collapse or technological regression or loss of purpose over time scales that exceed any stable civilization in human history.

[00:08:46]Cryogenic preservation, if it's even possible without fatal cellular damage, means consciousness that experiences discontinuity, that goes to sleep on Earth and wakes up centuries later at a destination, losing all the intervening time, losing connection to everyone and everything left behind, arriving at a world completely disconnected from the culture and society that sent the ship. And this assumes perfect reliability of cryogenic systems over centuries. Assumes no equipment failures, no gradual degradation, no unforeseen problems that might doom frozen sleepers to death without ever waking. All with no possibility of repair because everyone who might fix problems is frozen, creating a single point of failure that doomed the entire mission. Even with fusion propulsion, even with generation ships or cryogenics, even accepting all these enormous challenges, we're still talking about reaching only the very nearest stars, only systems within a few light years, only a tiny fraction of the galaxy, and each journey taking centuries.

[00:10:00]Expanding throughout the galaxy at these speeds would take millions of years, would require maintaining continuity of purpose and civilization across time scales that dwarf all of human existence. would create colonies so separated in time that they might as well be completely disconnected civilizations, unable to communicate meaningfully, unable to maintain any kind of unified culture or society, fragmenting into isolated populations that over millions of years would diverge into what would effectively be different species, different civilizations with no meaningful connection to their common origin. But uh maybe we can do better than fusion.

[00:10:45]Maybe we can push velocities much higher to 10% or 20% or even 30% of light speed. Before this video ends, I wanted to let you know that I've temporarily reduced the price of my ebook 12 principles for understanding the fabric of reality. It's a 110 plus page deep dive into the biggest ideas about space, time, black holes, and the true nature of reality explained in a simple and powerful way. If you've been enjoying the channel and want to go deeper, this is for you. The discount is only temporary, so check it out now using the link in the description, which would reduce journey times to decades rather than centuries.

[00:11:31]Would make interstellar travel achievable within single human lifetimes. Would transform it from multigenerational epic to something more like the age of sail voyages that crossed Earth's oceans. long and dangerous, but achievable, survivable, something humans could actually do and return from and tell others about. To reach these velocities requires even more exotic propulsion, antimatter perhaps using the energy released when matter and antimatter annihilate.

[00:12:05]Converting mass directly into energy with 100% efficiency according to Einstein's famous equation E= MC².

[00:12:14]Antimatter propulsion is theoretically possible. The physics works. The energy densities are sufficient. But the practical challenges are staggering.

[00:12:24]First, you have to make antimatter, which requires enormous energy, far more energy than the antimatter will release when you use it. making the entire process energy negative, requiring massive infrastructure and enormous power sources just to produce the small amounts of antimatter needed for propulsion. Then you have to store it which means keeping it completely isolated from all normal matter because any contact means instant annihilation requires magnetic containment systems that cannot fail even briefly requires perfect reliability over years or decades or centuries. Any tiny malfunction means the entire fuel supply annihilates in an instant, releasing energy equivalent to thousands of nuclear weapons, vaporizing the spacecraft and everyone on it. And even if you solve production and storage, even if you can safely use antimatter for propulsion, the energy requirements remain staggering. Accelerating even a modest spacecraft to 10% of light speed requires fuel mass comparable to the spacecraft mass itself. And that's with perfect efficiency. With 100% of the annihilation energy going into propulsion, which is physically impossible, real rocket efficiency is always far less than perfect. And then you need to decelerate at the destination, which requires carrying even more fuel to slow down, which increases the mass that needs to be accelerated, which requires even more fuel. In a recursive problem that makes the initial fuel requirements increase exponentially, making the entire spacecraft overwhelmingly dominated by fuel mass with the actual payload, the crew and life support and equipment becoming a tiny fraction of total mass.

[00:14:25]This is the tyranny of the rocket equation. The fundamental mathematical relationship between mass and velocity that makes high-speed space travel so difficult that penalizes every increase in speed with exponentially larger fuel requirements that creates fundamental limits on what's achievable even with perfect propulsion systems and perfect efficiency. Getting to 10 or 20% of light speed might be possible with antimatter and perfect engineering. But getting to 50% or 70% becomes prohibitively difficult.

[00:15:03]Requires fuel masses. Many times the payload mass creates engineering challenges that might simply be insurmountable no matter how advanced your technology becomes. And all of this assumes you solve another enormous problem, which is protection from interstellar medium. Space between stars is not empty. It contains gas and dust, very diffuse, far thinner than any vacuum we can create on Earth. But at relativistic velocities, even this incredibly thin material becomes deadly.

[00:15:36]At 10% of light speed, a single hydrogen atom hits with the energy of a high-speed bullet. At 50% of light speed, individual atoms hit like artillery shells. Any impact with even microscopic dust grains releases energies sufficient to vaporize spacecraft material, creates cascading damage, makes the spacecraft hull effectively a blade away under constant bombardment from interstellar medium that at these speeds becomes lethal radiation and physical impacts far exceeding anything we can shield against with any known materials.

[00:16:18]This means relativistic spacecraft need enormous shields, massive protective structures that absorb or deflect interstellar impacts, adding even more mass, requiring even more fuel, making the already difficult engineering problems even harder, possibly creating fundamental limits on maximum achievable velocities, not from propulsion, but from protection. From the fact that going faster increases impact energies to levels that cannot be defended against, making the interstellar medium itself a velocity barrier, a physical constraint imposed by the structure of the galaxy, by the simple fact that space contains matter, however diffuse, that becomes increasingly dangerous as relative velocity increases.

[00:17:09]But even if we solve all of these problems, even if we achieve propulsion systems capable of reaching 10 or 20% of light speed, even if we solve the fuel and storage and shielding and reliability challenges, even if we can build spacecraft capable of crossing interstellar distances in decades rather than centuries, we encounter something even more fundamental, something that strikes at the heart of what interstellar travel means.

[00:17:39]something that most people never truly absorb when they imagine future space exploration.

[00:17:46]And that's time dilation, the relativistic effect where time passes differently for travelers moving at high velocities compared to people remaining stationary. An effect that becomes significant at just the velocities we need for practical interstellar travel.

[00:18:03]an effect that creates profound disconnection between travelers and the civilization they leave behind. Time dilation is a fundamental consequence of relativity, of the way spacetime is structured, of the fact that space and time are not separate but unified into a four-dimensional geometry where moving through space affects your motion through time. At everyday velocities, time dilation is negligible, unmeasurable in human terms. But as velocities approach significant fractions of light speed, the effect becomes dramatic, becomes impossible to ignore, becomes a dominant feature of relativistic travel that makes it fundamentally different from any journey humans have undertaken before. At 10% of light speed, time dilation is small but noticeable, about half a percent.

[00:18:58]Meaning a 40-year journey to Alpha Centuri and back at this speed would age travelers by about 39.8 years while 40 years passed on Earth. Not a huge difference, but symbolically significant. The first hint that interstellar travel separates people not just in space, but in time itself. But at 30% of light speed, time dilation reaches 5%. Meaning a 30-year journey ages travelers by about 28.5 years, a year and a half difference. Starting to create meaningful disconnection.

[00:19:37]At 50% of light speed, time dilation reaches 15%.

[00:19:43]Meaning a 20-year journey ages travelers by only 17 years while 20 years pass on Earth. A three-year difference significant in human terms, meaning travelers return younger than they should be, return to a world that has aged more than they have, return to find friends and family older, changed, living in a future the travelers haven't experienced. And at higher velocities, the effect becomes dramatic. At 70% of light speed, time dilation reaches about 30%. Meaning a 10-year journey ages travelers by only 7 years while 10 years pass on Earth. A three-year difference.

[00:20:25]At 90% of light speed, time dilation reaches about 56%.

[00:20:32]Meaning a 10-year journey ages travelers by only 4.4 years while 10 years pass on Earth. At 99% of light speed, time dilation reaches almost 90%. Meaning a 10-year journey ages travelers by only about 1.4 years, while 10 full years pass on Earth, creating nearly a decade of temporal disconnection from a journey that from the traveler's perspective lasted barely a year. This is not science fiction speculation. This is fundamental relativistic physics confirmed by every experiment that tests relativity observed in particle accelerators where particles traveling at near light speed live much longer than their stationary counterparts before decaying observed in precise atomic clocks flown on aircraft showing exactly the predicted time dilation.

[00:21:30]making this effect absolutely certain, absolutely real, absolutely fundamental to how spacetime works. And it creates a profound problem for interstellar travel. A problem that has nothing to do with engineering or technology, but with the very nature of what we're trying to accomplish with what it means to cross interstellar distances at the speeds necessary to make such travel practical.

[00:21:54]Because time dilation doesn't just create temporal disconnection from Earth. Doesn't just mean travelers age less than people left behind. It means travelers literally experience less time, live through fewer years, have fewer subjective days and hours and minutes between departure and arrival than people waiting for them on Earth.

[00:22:18]It means the journey is shorter for travelers than for everyone else. Means travelers effectively skip forward through time. Jump ahead in Earth's history without experiencing the intervening years. Arrive at a future they haven't lived through. Return to find the world has moved on without them. Friends have aged or died. Society has changed. Culture has evolved.

[00:22:44]Technology has advanced. Everything is different. And the travelers have no connection to these changes. No shared experience of the time that passed, no gradual adaptation to the ways things changed, just sudden discontinuity, sudden displacement into a future that for them arrived instantly, but for everyone else took decades. This creates profound psychological and social problems that have nothing to do with the journey itself. Nothing to do with the technical challenges of space travel. Everything to do with the human meaning of what's happening. The way relativistic travel tears people out of their social and temporal context. Makes them time travelers whether they want to be or not. forces them to abandon everyone and everything in their present for an unknowable future. They'll experience as sudden arrival, but everyone else experienced a slow progression. This is not something technology can fix, not something better engineering can solve. This is fundamental physics, fundamental geometry of spaceime making relativistic interstellar travel necessarily involve temporal disconnection, necessarily create time travelers, necessarily separate people not just in space but in time itself. And the faster you travel, the worse this becomes, the more dramatic the time dilation, the greater the temporal disconnection until at velocities approaching light speed, the effect becomes so extreme that the traveler's experience of time becomes arbitrarily shorter than Earth's experience, making it theoretically possible to cross enormous distances, even across the galaxy in a human lifetime from the traveler's perspective, while millions of years pass on Earth, making the traveler arrive at a galaxy that has evolved beyond recognition, where everything and everyone they knew is not just dead, but forgotten. Where human civilization, if it still exists, has transformed into something unrecognizable.

[00:24:58]Where Earth itself might have become uninhabitable. where the entire context of the journey, the entire reason for going has been obliterated by millions of years of change that the traveler skipped over, experienced as brief voyage, while actually representing geological time scales of evolution and change and transformation. This creates a fundamental paradox at the heart of interstellar travel. The faster you travel, the shorter the subjective journey time, the more practical the journey becomes from the traveler's perspective, but the greater the temporal disconnection, the more catastrophic the isolation from origin and destination, the less meaningful the journey becomes in terms of maintaining continuity with the civilization that uh that sent you. At moderate relativistic velocities, the disconnection is uncomfortable but survivable, measured in years or decades, creating challenges but not complete severance. But at high relativistic velocities, the disconnection becomes total, creates complete temporal isolation, makes the journey effectively one way. Not because you can't return, but because returning means arriving at a future so distant that return has no meaning. Everyone you knew is dead. Everything you knew is gone. You're effectively traveling to an alien future rather than returning home.

[00:26:27]This suggests there might be an optimal velocity for interstellar travel. Not the fastest possible velocity, but some moderate relativistic speed where journey time is short enough to be practical, but time dilation is small enough to maintain some connection to origin, maybe 30 or 40% of light speed. Fast enough to reach nearby stars in decades.

[00:26:51]Slow enough that time dilation doesn't completely disconnect travelers from the civilization that sent them. But even at these optimal velocities, the challenges remain enormous. The disconnection remains significant. The isolation remains profound, suggesting that interstellar travel necessarily involves accepting temporal displacement, accepting disconnection, accepting that crossing interstellar distances means leaving behind not just places but times. means stepping out of your era into someone else's future means losing temporal continuity with everything and everyone you're trying to connect with.

[00:27:34]And there's another layer of isolation that's even more fundamental, even more disturbing, which is communication delay. The simple fact that even if we achieve relativistic travel, even if we establish colonies on distant worlds, even if we create some kind of interstellar civilization, those colonies cannot communicate meaningfully, cannot coordinate, cannot maintain unity or uh shared culture or common purpose across the light years that separate them. Because communication is limited by light speed just like travel is. Signals take years or decades or centuries to cross interstellar distances. Making realtime conversation impossible.

[00:28:23]Making any kind of interactive communication impossible.

[00:28:28]Making each colony effectively on its own, making its own decisions.

[00:28:32]Developing its own culture.

[00:28:34]unable to get advice or instruction or coordination from Earth or from other colonies because the delays are so long that anything timesensitive requires local decisionm.

[00:28:47]Anything important happens before anyone else can know about it. Creating inevitable divergence, inevitable independence, inevitable fragmentation of any interstellar civilization into isolated populations that over time become separate civilizations, separate cultures. eventually separate species as evolution and genetic drift and deliberate modification create populations that can no longer interbreed, that no longer share common biology or common culture or common purpose. This means interstellar expansion, if it happens at all, necessarily means civilizational fragmentation. Necessarily means losing unity. Necessarily means creating separate isolated populations that over time diverge into something that can no longer meaningfully be called a single civilization. making the dream of a unified galactic civilization, a Federationstyle future where different worlds cooperate and communicate and maintain shared values and common purpose. Physically impossible, prevented not by lack of desire or lack of effort, but by the simple geometry of spaceime, by communication delays that make unity impossible, that force independence and isolation. that create separate evolutionary and cultural trajectories that over millions of years produce not one civilization spanning the galaxy, but millions of separate isolated civilizations that happen to share common ancestry, but have no meaningful ongoing connection. This brings us to what might be the deepest question about interstellar travel, which is whether it's actually worth doing. Whether the costs and challenges and isolation and fragmentation are justified by whatever benefits might come from establishing colonies on distant worlds. And this is not obvious.

[00:30:58]This is something that requires serious thought about what we're actually trying to accomplish, what we hope to gain.

[00:31:06]why we think spreading across the galaxy is desirable or necessary or worth the enormous investment of resources and the acceptance of all the profound problems that interstellar travel creates. The usual arguments for interstellar expansion focus on survival, on not keeping all of humanity's eggs in one basket, on making our species immune to extinction from local disasters like asteroid impacts or super volcanoes or nuclear war or climate catastrophe. And this argument has force. Redundancy is good. spreading across multiple worlds means no single catastrophe can eliminate all of humanity, creates backup copies of human civilization that can survive and continue even if Earth is destroyed. But this argument doesn't require interstellar travel. It's satisfied by colonizing our solar system, by establishing self-sustaining settlements on Mars or the moons of Jupiter or O'Neal cylinders in Earth orbit, creating redundancy without facing the vastly greater challenges of crossing light years. achieving the survival benefit without the temporal disconnection and communication delays and civilizational fragmentation that interstellar expansion necessarily creates. Another argument is resources accessing materials and energy and living space beyond what Earth and our solar system provide. But again, this doesn't require interstellar travel. Our solar system contains more resources than humanity could use in millions of years. More metals in the asteroid belt than will ever need. More energy from the sun than all of civilization could consume. More potential living space in orbital habitats than exists on Earth.

[00:33:04]Making resource scarcity not a compelling reason to cross lighty years when abundance exists in our local stellar neighborhood. The resources argument for interstellar travel assumes we exhaust our solar system. But doing that would require such massive industrialization, such enormous energy use, such vast populations that we'd have capabilities far beyond what interstellar travel requires, making the need obsolete before it arises. A third argument is exploration. the inherent human drive to see what's beyond the horizon, to explore new worlds, to satisfy curiosity about what else is out there, to make discoveries that can only be made by going there. And this argument has real force. Humans do explore, do want to see what's beyond, do find meaning and purpose in expanding frontiers. But exploration doesn't require colonization, doesn't require permanent settlement, doesn't require creating self- sustaining populations on distant worlds. Exploration can be done with automated probes, with sophisticated robots, with artificial intelligence sent to observe and report back.

[00:34:23]Achieving the discovery and knowledge benefits without the enormous human cost, without risking lives on uncertain journeys, without accepting the temporal disconnection and isolation that human interstellar travel creates. And there's a deeper question, which is whether establishing distant colonies actually benefits humanity or whether it just creates isolated populations that rapidly cease to be human in any meaningful sense that diverge and evolve and transform until they're separate species with no real connection to Earth, making interstellar expansion, not the spreading of human civilization, but the fragmentation and eventual dissolution of human civilization into countless separate lineages that over millions of years become as different from each other as different animal species sharing common ancestry but no longer meaningfully part of a single civilization or single species or single story. If this is what interstellar expansion produces and physics suggests it might be then maybe we shouldn't want it. Maybe the dream of spreading across the galaxy is actually a dream of fragmenting and dissolving humanity into forms that rapidly become alien to each other, making the whole endeavor a kind of slow suicide of human unity and human identity and uh human civilization.

[00:35:51]Perhaps the most terrifying reality about interstellar travel is not that it's technologically difficult, not that it requires vast resources or exotic propulsion or radical new physics, not that the uh engineering challenges are enormous or the dangers are severe.

[00:36:09]Perhaps the most terrifying reality is that interstellar travel, even if achievable, even if we develop the capabilities to cross light years at significant fractions of light speed, fundamentally changes what it means to be human. Fundamentally severs the connections that make civilization possible. Fundamentally creates isolation and fragmentation that might be worse than staying on Earth. that might represent the end of humanity as a unified species rather than the expansion and flourishing that science fiction imagines. The universe itself may be structured in a way that keeps intelligent life permanently separated, not through hostile conditions or dangerous environments, but through the simple geometry of spaceime. Through distances too vast to cross without accepting profound temporal disconnection. Through communication delays too long to maintain unity, through time scales that guarantee divergence and fragmentation.

[00:37:12]through the inexurable logic of relativity and light speeded limits and the sheer scale of the galaxy creating isolation that no technology can overcome because the isolation isn't technological but geometric.

[00:37:25]built into the fabric of spaceime itself, making the cosmos not a place for civilization to expand into, but a place where each civilization remains forever isolated in its local stellar neighborhood. Unable to truly reach others, unable to maintain unity across interstellar distances, unable to escape the isolation that spacetime imposes on everything that tries to cross the vast emptiness between stars. And humanity may someday build extraordinary technologies, may master antimatter propulsion and fusion drives and perhaps even approaches to relativistic velocities.

[00:38:06]May develop generation ships or cryogenic preservation or radical life extension. May solve all the technical challenges that currently make interstellar travel impossible. may reach nearby stars and established colonies and technically achieve what we currently only imagine. While still discovering that the cosmos was never designed to let civilizations truly escape their isolation. That the distances and time scales and communication delays create fundamental barriers to meaningful expansion. That the universe keeps intelligent life separated not through active hostility but through passive indifference.

[00:38:47]Through the simple fact that spacetime is structured in ways that make true interstellar civilization impossible that create isolation as fundamental property of cosmic geometry that ensure every intelligent species that arises remains forever bounded by light speed limits and relativistic effects and sheer scale making the dream of galactic empire not a future possibility but a fundamental impossibility. Making the loneliness of intelligence not a temporary condition but a permanent feature of how the universe works.

[00:39:23]Making the silence of the cosmos not a mystery waiting to be solved but a direct consequence of space-time geometry that prevents the kind of expansion and communication and unity that we imagine advanced civilizations achieving. Ensuring that we remain as we've always been, isolated on our world, looking up at stars that remain forever beyond meaningful reach, forever separated by distances that physics itself ensures we cannot truly cross.