By Futurist Thomas Frey
Why Kip Thorne’s Thought Experiment Changes Everything
Nobel laureate Kip S. Thorne once posed a deceptively simple question that haunts futurists and physicists alike: “A thousand years from now, what things will be possible and what things will not?”
It’s a fascinating framework for separating the merely difficult from the genuinely impossible, the achievable from the fantasy, the problems we’ll eventually engineer our way past from the constraints that physics itself enforces. Most people conflate “we can’t do it now” with “it can’t be done.” Thorne’s question forces us to think harder.
A thousand years is long enough that almost any engineering challenge becomes solvable if physics permits it. It’s short enough that the fundamental laws of the universe won’t change. The question strips away our current technological limitations and asks: what does physics itself allow, regardless of how difficult the engineering might be?
The answers are both more liberating and more constraining than most people imagine. We’re building our future based on assumptions about what’s possible that may be completely wrong—either wildly optimistic about things physics forbids, or tragically pessimistic about things physics permits but we haven’t figured out yet.
Getting this distinction right matters enormously, because we invest resources, make policy decisions, and shape civilization around beliefs about what tomorrow can and cannot hold.
The Things Physics Probably Permits
Start with what Thorne’s framework suggests is genuinely possible, even if we currently have no idea how to achieve it.
Faster-than-light travel? Almost certainly forbidden by the structure of spacetime itself. But near-light-speed travel? Physics permits it. Engineering a spacecraft that can reach even ten percent of light speed remains monumentally difficult, but nothing in physics says it’s impossible. A thousand years is plenty of time to solve engineering challenges.
Practical fusion power? Definitely possible—the sun proves it works. The engineering challenges are substantial but not insurmountable. A thousand years from now, we’ll look back at our current fusion struggles the way we now look at early aviation pioneers who couldn’t keep planes aloft for more than a few seconds. The physics works. We just haven’t mastered the engineering yet.
Radical life extension, possibly approaching practical immortality? Biology is just applied chemistry, which is just applied physics. Nothing in physics forbids maintaining biological systems indefinitely if we can repair damage as fast as it accumulates.
The engineering is breathtakingly complex, but complexity isn’t impossibility. A thousand years gives us time to map every biological process and develop interventions that currently seem like magic.
Artificial general intelligence that matches or exceeds human cognitive capabilities? The human brain proves it’s possible—we’re just machines made of different materials. Whether we build intelligence in silicon, quantum computers, or substrates we haven’t invented yet, physics doesn’t forbid machine intelligence.
A thousand years of computational progress makes today’s debates about whether AGI is possible look quaint.
Controlling gravity at a fundamental level? This one’s harder to call. Current physics doesn’t give us clear pathways, but our understanding of gravity remains embarrassingly incomplete. We don’t know if gravitational control is “merely” extraordinarily difficult engineering or genuinely forbidden by physics. Thorne’s framework suggests we need better physics before we can answer definitively.
The Things Physics Probably Forbids
Now consider what physics itself seems to forbid, regardless of engineering prowess.
Traveling backward in time to change the past creates causality violations that appear fundamentally incompatible with how the universe works. Not just difficult—genuinely impossible. A thousand years of engineering brilliance won’t overcome contradictions embedded in the logical structure of reality.
Perpetual motion machines that create energy from nothing violate thermodynamics so fundamentally that betting against them is as safe as any wager in science. We can get better at harnessing energy, storing it, and using it efficiently, but we cannot create it from nothing. Physics enforces that constraint absolutely.
Transmitting information faster than light appears forbidden by the structure of spacetime itself, not by engineering limitations. Quantum entanglement doesn’t help—despite popular misunderstanding, it cannot transmit information faster than light without violating causality.
A thousand years of clever engineering won’t circumvent constraints woven into the fabric of reality.
Perfect prediction of complex chaotic systems may be impossible even with unlimited computing power, not because we lack computational resources but because chaos means tiny measurement uncertainties cascade exponentially. Some things may be fundamentally unpredictable regardless of technological advancement.
Why This Distinction Matters Desperately
The difference between “physics permits it but we haven’t solved the engineering” and “physics forbids it fundamentally” determines where we should invest resources, what futures we should prepare for, and which dreams we should pursue versus abandon.
We waste enormous effort chasing impossibilities when we conflate the two categories. We abandon achievable goals prematurely when we mistake engineering difficulty for physical impossibility.
Consider energy policy. If fusion power is merely difficult engineering rather than physical impossibility—and physics strongly suggests it is—then investing heavily in solving fusion makes sense even if progress seems frustratingly slow. We’re not betting against physics, just racing our own engineering capabilities.
Conversely, investing in perpetual motion or over-unity devices is wasting resources on physically impossible goals regardless of how appealing they sound.
Consider space exploration. If near-light-speed travel is physically permissible but extraordinarily difficult to engineer, we should be laying groundwork now for capabilities that might take centuries to mature. If faster-than-light travel is physically forbidden, we should stop treating interstellar colonization as something that becomes easy once we “figure out FTL” and instead plan around the constraint that stars are genuinely far apart in ways no technology can shortcut.
Consider artificial intelligence development. If machine intelligence matching human cognition is physically permissible—and everything we know about physics and computation suggests it is—then concerns about “whether” AGI is possible distract from the more important questions about “when” and “how we prepare for it.”
The physics says it’s coming. The only question is timeline and implementation details.
The Humility Physics Demands
Thorne’s thousand-year framework also teaches humility about our current understanding. Things we confidently declare impossible might just be difficult. Things we assume are inevitable might violate constraints we haven’t discovered yet.
The history of physics is littered with confident proclamations that turned out to be embarrassingly wrong.
Heavier-than-air flight was “obviously impossible” until the Wright brothers did it. Nuclear energy was “moonshine” according to leading physicists just years before we built reactors. Quantum computing was considered impossible until we built quantum computers.
We’re reliably terrible at distinguishing between “we don’t know how” and “physics forbids it.”
But we’re also prone to wishful thinking in the opposite direction, treating science fiction technologies as inevitable just because we can imagine them. Teleportation, antigravity, faster-than-light travel—these populate our fiction so thoroughly that many people assume they’re merely awaiting engineering breakthroughs rather than potentially violating physics fundamentals.
What We Should Be Asking
Thorne’s question pushes us toward better questions than “what will the future bring?”
Instead we should ask: What does physics permit that we’re not pursuing because we’ve conflated difficulty with impossibility? What technologies are we betting on that physics may actually forbid? Where are we investing resources based on science fiction rather than science?
A thousand years is long enough that nearly any engineering challenge becomes solvable if physics allows it. It’s short enough that the fundamental structure of reality won’t change.
The constraints we face in a thousand years will be the constraints physics itself imposes, stripped of our current engineering limitations.
After all, understanding what physics permits versus forbids determines which dreams are worth pursuing and which are pleasant fantasies that will never manifest regardless of effort invested. That distinction matters more than we typically acknowledge.
Final Thoughts
Kip Thorne’s thousand-year question offers a razor for cutting through hype, wishful thinking, and defeatism alike. It forces us to think clearly about what’s genuinely impossible versus merely difficult, what physics permits versus what physics forbids, and where we should be investing resources based on reality rather than fantasy.
The future we build depends on getting this distinction right.
Invest in solving the merely difficult and we potentially achieve breakthroughs that reshape civilization. Waste resources chasing the genuinely impossible and we squander opportunities to address achievable goals. Abandon the difficult because we mistakenly think it’s impossible and we consign ourselves to futures smaller than physics permits.
A thousand years from now, humans—or whatever we’ve become—will look back at our current debates about what’s possible with the same mixture of amusement and frustration we feel reading Victorian proclamations that heavier-than-air flight violated natural law.
The question is whether we’ll be remembered as the generation that distinguished physics constraints from engineering challenges, or as the one that confused the two and wasted centuries pursuing impossibilities while abandoning achievable dreams.
The physics doesn’t care what we believe. But our civilization’s trajectory depends entirely on understanding what physics actually permits within its inviolable constraints. Thorne’s question helps us see that distinction clearly, and seeing clearly might be the most valuable capability futurists can cultivate.
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