On Coordinates, Cosmic Uncertainty, and Why Time Travel Is Probably Not Happening
It Started at Two in the Morning
I could not sleep. This is, admittedly, not the most auspicious opening line for what I intend to be a serious piece of writing, but there it is. It was somewhere past two in the morning, and rather than lie there cataloguing the ordinary anxieties that tend to colonize a sleepless man’s thinking, I decided to go bigger. Much bigger. The question I landed on was, at first glance, absurdly simple: can we determine the exact position of a human being on the surface of the Earth, measured from the planet’s core outward?
The short answer, as it turned out, was yes. The longer answer unravelled into one of the more genuinely strange intellectual journeys I have taken, and I have taken a few. By the time the sun came up I had worked my way outward through the solar system, the galaxy, the structure of the cosmos, and arrived at the proposition that we are almost certainly living inside a black hole. Which is either a profound cosmological insight or evidence that I should drink less coffee after six in the evening. Possibly both.
What follows is my attempt to reconstruct that journey in some semblance of order. I will say upfront, as I have said before in other work, that I am not a scientist. I am a student of the Arts, a painter, a musician, and a writer who has always found the hard sciences rather more interesting when approached from the side door than through the front. I am… standing on the shoulders of giants , and occasionally losing my footing. Bear with me.
Where Are You, Exactly?
The question of precise terrestrial positioning has been solved with a rigor that should frankly astonish anyone who pauses to think about it. The governing framework is called the Earth-Centered, Earth-Fixed coordinate system, ECEF for short, and it places its mathematical origin at the Earth’s center of mass. Three axes extend outward from that point in mutually perpendicular directions, and every location on the planet’s surface can be expressed as a set of three numbers relative to that origin. This is the mathematical skeleton upon which GPS navigation is built. Your phone knows where you are because it is, beneath all the friendly interface design, solving a set of ECEF equations in real time.
The standard reference for this system is WGS84, the World Geodetic System of 1984, which defines the reference ellipsoid that global navigation uses as its baseline. Geodetic-grade receivers can now determine position to within a few millimeters. A few millimeters. The center of the Earth is 6,371 kilometers beneath your feet, 3,959 miles (and change) for those that use the only system to put people on the moon with, and we can locate you relative to it with the precision of a thumbnail. That is, by any reasonable measure, extraordinary.
Now here is where it starts to get interesting. The Earth is not, in fact, a rigid body. It deforms. The Moon and Sun pull on it gravitationally and the solid surface flexes upward and downward by 20 to 40 centimeters, about eight-16 inches, in a cycle that repeats roughly twice a day, this is called the solid Earth tide, and most people have no idea it exists. Scandinavia and Canada are still rising at over ten millimeters per year, rebounding from the weight of ice sheets that melted at the end of the last glacial maximum. The crust breathes seasonally as groundwater loads and atmospheric pressure shifts. In short, your precise ECEF coordinate is not a fixed number. It is a number that is continuously, measurably changing.
There was, for a period in the mid-twentieth century, a serious scientific hypothesis proposing that the Earth itself was expanding, advanced most forcefully by the Australian geologist S. Warren Carey, who argued that the fit of the continents made more sense on a smaller primordial globe. The idea got a fair hearing before plate tectonics made it unnecessary. Modern geodetic analysis has since established that any net change in the Earth’s mean radius amounts to no more than 0.1 millimeters per year — well within known elastic deformation and nowhere near the expansion Carey envisioned. The Earth deforms. It does not meaningfully grow. Good to know.
The Sun Has No Address
Emboldened by the success of the ECEF system, one might reasonably suppose that similar precision awaits us at the next scale outward. One would be wrong, and the reasons why are worth dwelling on.
The International Astronomical Union has established coordinate frameworks for the solar system, and the Jet Propulsion Laboratory’s ephemeris models locate the Sun’s center of mass with precision sufficient to navigate spacecraft across billions of kilometers. So, in the mathematical sense, the Sun does have an address. The problem is that there is nothing at that address you could put a pin in.
The Sun is not a solid body. It is a plasma body in continuous turbulent convection, and its visible surface (the photosphere) is not a surface at all in any meaningful physical sense. It is a shell of opacity, the depth at which the gas becomes dense enough to be opaque to outgoing light. Below that is convective chaos all the way down. The discipline of helioseismology has mapped the solar interior with considerable ingenuity by inverting the acoustic oscillations that ripple across the surface, in much the same way a geologist reads the interior of the Earth from seismic waves. The dominant five-minute oscillations displace the solar surface by kilometers continuously. The Sun is, in the most literal available sense, ringing like a bell… one that has never stopped sounding and that nobody struck.
Furthermore, and this is the cool part, the Sun’s center of mass does not even sit at the Solar System’s barycenter. Jupiter is massive enough, at certain points in its orbit, to displace the barycenter outside the solar photosphere entirely. The Sun executes a slow, irregular orbit around this shifting point, a motion that is perfectly real and measurable. The thing we call the center of the solar system is not a fixed location. It wanders.
The honest conclusion is this: the solar center of mass exists as a real, instantaneous, physically meaningful point at every moment. There is just nothing anchored to it. It is like asking for the precise center of a wave breaking on a beach. The point exists. Finding it by any direct means is another matter entirely.
And the Galaxy Is Worse
Locating the Sun within the Milky Way presents a problem with no good analogue at smaller scales. We are inside the object we are trying to map. Every survey conducted from Earth is made from a single embedded vantage point, surrounded by dust and gas that obstruct the view in ordinary light across most of the galactic disk. It is, to turn a phrase, rather like trying to map a forest from within it, in dense fog, using only sound.
The Sun’s distance from the galactic center, which sits at the location designated Sagittarius A (Sgr A*), has been refined progressively over decades. Current estimates place it at around 26,000 light-years, though the uncertainty band remains several hundred light-years wide. The GRAVITY Collaboration, using interferometric observations of stellar orbits around Sgr A*, has produced the most precise recent measurements. The Sun also sits slightly north of the galactic midplane, by perhaps 50 to 100 light-years, even this modest offset carries genuine uncertainty.
The Sun does not follow a clean circular orbit around the galactic center either. It oscillates vertically through the galactic plane on a period of roughly 70 million years, and its orbital velocity carries its own measurement uncertainties. The Local Standard of Rest, the reference frame defined by the average motion of neighboring stars, is a statistical construction rather than a physical landmark. One cannot locate oneself precisely on a map that is itself still being drawn.
The Milky Way’s large-scale structure, its arm positions, bar orientation, total mass distribution, remains genuinely contested in the contemporary literature. So not only are we uncertain about our position within the galaxy; we are uncertain about the structure of the galaxy within which we are uncertain of our position. This is, admittedly, not the most reassuring state of affairs.
The Supercluster and the Moving Floor
Every uncertainty established at each prior level propagates outward. An imprecise solar position within the Milky Way corrupts our galactic center position, which corrupts our Local Group position, which undermines any claim to precise supercluster coordinates. The errors stack rather than cancel.
At the supercluster scale an entirely new class of problem enters the analysis. The Hubble expansion becomes dominant. Galaxies are not merely moving through space. The space between them is stretching. This introduces a fundamental ambiguity in what the word position can even mean across cosmological distances. Astronomers distinguish between a galaxy’s peculiar velocity, its actual motion relative to the background expansion, and its recession velocity, the apparent motion produced by the expansion of space itself. Disentangling these two components at the boundaries of large structures is a genuine and ongoing observational challenge.
The Laniakea Supercluster, the structure within which the Milky Way resides, was not even coherently defined until 2014, when Tully and colleagues mapped it in Nature using peculiar velocity field analysis rather than positional data. Its boundaries are defined by watershed lines in the cosmic flow field. They are dynamic rather than geometric. If the structure’s edges are velocity flows rather than physical surfaces, what precisely does it mean to have a position within it?
To compound matters, the entire Local Supercluster is streaming toward a mass concentration called the Great Attractor, partially hidden behind the galactic plane in the direction of Centaurus. Its nature and precise location remain incompletely resolved. We are moving toward something we cannot fully see, at a velocity we cannot precisely measure, from a position we cannot exactly specify. I have been in military situations that felt less disorienting than this.
The Big Bang Had No Address Either
Having traced the cascade of uncertainty outward from a GPS coordinate through the solar system, the galaxy, and the supercluster, one arrives at what might appear to be the end of the line: the Big Bang itself. Surely, one thinks, we can measure our position from the point of cosmic origin. The universe began somewhere. Why not there?
Here the inquiry hits bedrock, and the bedrock is considerably stranger than the inquiry anticipated. The Big Bang was not an explosion within pre-existing space, a detonation at some locatable point from which matter expanded outward. It was an expansion of space itself. Every point in the observable universe was, at the initial moment, coincident with every other point. There is no origin coordinate to measure from, because every location in the universe can claim with equal geometric validity to be the site of the Big Bang. Mind blown.
I will admit that this took me a few minutes to sit with at two in the morning. My bed, the screen upon which you read this is the site of the Big Bang. The galactic center is the site of the Big Bang. A galaxy twelve billion light-years distant is the site of the Big Bang. All equally. There is no “there there,” as Gertrude Stein did not intend but accidentally summarized rather well.
What we do have is the cosmic microwave background radiation, the thermal afterglow of the early universe, redshifted down to microwave frequencies, which arrives at Earth uniformly from all directions and forms a shell around the observable horizon at roughly 46 billion light-years in every direction. This is a boundary of observability set by the finite speed of light and the age of the cosmos. Every observer in the universe sits, by definition, at the center of their own observable universe. Including us. Including everyone.
I had actually proposed something similar to this in my 2004 paper on time travel ethics, that the microwave radiation might represent the overpressure wave of the Big Bang expanding outward like a nuclear detonation. The modern picture is considerably more sophisticated, but the intuition that the CMB marks something fundamental about the geometry of everything was not entirely wrong. I will take that.
I should note here, because it bears directly on the argument, and because the timing is almost absurdly fortuitous, that a paper published in Physical Review Letters in March 2026 by Liu, Quintin, and Afshordi of the University of Waterloo and the Perimeter Institute has proposed what they call Quadratic Quantum Gravity as an ultraviolet completion of the Big Bang. Standard cosmology requires inflation — the rapid early expansion of the universe — to be driven by a separate theoretical apparatus, an inflaton field bolted onto Einstein’s equations by hand to make the numbers work. The Waterloo team found that inflation can emerge naturally from gravity’s own quantum structure, without any additional ingredients, by adding quadratic curvature terms to the gravitational action in a way that remains mathematically consistent at the extreme energies present at the universe’s birth. This matters for the argument here because it is one more piece of evidence that our standard picture of the early universe is a work in progress rather than a settled account. The model also predicts a minimum level of primordial gravitational waves detectable by forthcoming experiments such as LISA, which would make it testable in a way that earlier quantum gravity frameworks were not. I mention it with appropriate qualification: published in a first-rank journal, carrying genuine observational predictions, and not yet confirmed. Interesting times.
I want to address something that readers familiar with my Codex of the Outer Realms may have noticed building across this section. The paper’s argument that the Big Bang has no locatable origin coordinate, and its proposal that the cosmic microwave background may constitute the event horizon of a parent universe, implies a prior condition, something structurally anterior to our spacetime from which our universe was generated. One might reasonably ask whether this sits comfortably alongside the Codex’s treatment of Azathoth as the primordial void, the condition that precedes and underlies all causal structure. I have looked at this carefully, and the answer is that the tension resolves itself rather elegantly. The Heretical Shape of the Universe states directly that there is no fixed center, only the pressure that arises when systems behave as though a center were real — which is, almost word for word, what the paper’s cosmology concludes about the Big Bang’s non-locatability. More pointedly, the Azathoth volume of the Codex describes him as the anti-origin where reason moves yet arrives nowhere, creation beneath his pulse not genesis but repetition without source, a cycle without inception. A cycle without inception is precisely what the black hole cosmology implies: an infinite regress of parent universes, each generating the next, with no first cause and no original coordinate. The Codex was written as philosophy rather than physics, but both arrived, by different roads, at the same structural conclusion. I find that more satisfying than any deliberate reconciliation I could have engineered.
We Cannot Even Agree on How Fast We Are Expanding
The expansion rate of the universe is expressed as the Hubble constant, H-zero, relating recession velocity to distance: approximately 70 kilometers per second for every 3.26 million light-years. This sounds precise enough. The difficulty is that the two best methods of measuring it disagree, and the disagreement has not gone away as the measurements have improved. It has gotten worse.
The Planck satellite‘s analysis of the cosmic microwave background gives a Hubble constant of about 67.4 kilometers per second per megaparsec. The cosmic distance ladder, using Cepheid variable stars and Type Ia supernovae as standard candles, consistently returns values nearer 73. Both methods are now mature enough that simple measurement error cannot comfortably explain the gap. The statistical discrepancy exceeds five sigma, which is the threshold at which physicists start taking something very seriously indeed. This is known as the Hubble tension, and it may eventually require a fundamental revision to the standard cosmological model.
Then there is the matter of dark energy. In 1998, the supernova survey teams of Perlmutter, Schmidt, and Riess established that cosmic expansion is not merely continuing but accelerating. Something is actively driving the universe apart with increasing vigor. This something is attributed to the cosmological constant, a term Einstein introduced into his field equations and then famously called his greatest blunder, before the universe had the audacity to vindicate it. Dark energy constitutes roughly 68 percent of the total energy content of the cosmos by current estimates. We have no idea what it physically is. Needless to say, this makes any calculation of our cosmic position rather more complicated than one might prefer.
I also want to note something that tripped me up at three in the morning and that I think deserves more attention than it usually gets. When we observe a galaxy at a distance of twelve billion light-years, we are not seeing it as it is now. We are seeing it as it was twelve billion years ago, because that is how long its light took to reach us. The actual present-day distance of that galaxy, accounting for the expansion that has continued during the light’s transit, is considerably greater. There is no snapshot of where everything presently is. There is only a layered record of where everything was at various historical moments. The universe, as we observe it, is a palimpsest rather than a photograph.
The Block Universe and the Promise of a Map
I want to turn now to a philosophical framework that has direct bearing on where this argument is heading, specifically the question of time travel, which has occupied my thinking in one form or another for over twenty years.
The block universe, or eternalist, position in the philosophy of time holds that all moments of spacetime possess equal ontological reality. Past, present, and future are coordinates within a four-dimensional manifold, not sequential states of a process that flows in one direction. The year 1066 exists as surely as this present moment. It is simply elsewhere in the block, at a different temporal coordinate, rather than genuinely gone. The physicist Lee Smolin has argued forcefully against this view, contending that time is real and fundamental rather than an illusion produced by our position within a static block; his book Time Reborn makes the case at length. I find the question genuinely open.
The reason the block universe matters here is that it is philosophically seductive for time travel. If past moments exist with the same ontological weight as the present, then to travel through time is not to access something that no longer exists. It is to navigate to somewhere that exists as fully as the room in which one currently sits. The block universe does not merely permit time travel in principle. It demands it, in the sense that there is a real address to go to.
The catch, and this is where the two-in-the-morning cascade of thought becomes genuinely uncomfortable, is that navigation requires coordinates, and coordinates require a stable reference frame. Everything established in the preceding sections of this essay demonstrates that the universe provides reference frames of radically diminishing stability as one moves outward in scale.
Why You Cannot Get Back to Last Tuesday
To return to a specific past moment, even granting the block universe entirely, one requires a precise four-dimensional address: three spatial coordinates and one temporal. The analysis above establishes that the spatial coordinates of any past moment are, practically speaking, irrecoverable.
The Earth occupied a different position relative to the Sun. The Sun occupied a different galactic longitude and latitude. The galaxy occupied a different position relative to the supercluster centroid. The supercluster itself was configured differently relative to the Shapley Attractor. Space has expanded and altered its geometry since every historical moment, because space expanding is what it does. The reference frames against which any past coordinate might be specified did not exist in their present forms. WGS84, the BCRS, galactic coordinate systems, these are human constructions mapped upon a dynamic reality.
The ECEF coordinate of your present chair in 1066 AD does not correspond to your present chair. It corresponds to a point in space somewhere in the vicinity of nothing in particular, because the planet has moved, the solar system has moved, the galaxy has moved, and space itself has expanded between all of those positions. This is not a navigational inconvenience. It is a fundamental feature of a universe in which there is no fixed external reference frame.
I want to note here that this argument is actually an extension of something I touched on in my 2004 paper, where I observed that getting to the past on Earth was the genuinely hard problem, even granting wormhole travel. What I did not fully appreciate then was that the spatial displacement problem is not merely one of calculating travel distance. It is a problem that exists because the universe has no anchor… no fixed point from which past coordinates could be defined with the precision that time travel would require. The block universe may be perfectly real. The addresses within it have been scrambled by fourteen billion years of expansion, orbital mechanics, and cosmic rearrangement.
Unless We Are Inside a Black Hole
This is where the two-in-the-morning thinking took a turn I did not anticipate, and which I want to present carefully because it sounds considerably more outlandish than it is.
The proposal is this: our universe may be the interior of a black hole belonging to a parent universe, and the cosmic microwave background radiation, rather than being merely an observational horizon, may constitute the actual event horizon of that black hole as seen from within.
I want to stress that this is not a fringe notion dreamed up by the sleep-deprived. The hypothesis has legitimate theoretical pedigree extending back to 1972, when the physicist Raj Pathria noted deep mathematical correspondences between the Schwarzschild metric of a black hole exterior and the metric of a closed universe at maximum scale factor. It was developed with particular rigor by Nikodem Poplawski of the University of New Haven, whose Einstein-Cartan torsion cosmology proposes that every black hole generated by gravitational collapse creates a new universe within its event horizon. Lee Smolin‘s cosmological natural selection framework, proposed in 1992 and elaborated in The Life of the Cosmos in 1997, advances a related argument. More recently, a 2025 analysis of over two hundred early galaxies observed by the James Webb Space Telescope found that roughly two-thirds rotate clockwise, when only half would be expected to do so by chance. One compelling explanation is that our universe inherited a preferred rotational axis from the spin of its parent black hole.
In Poplawski’s framework, a repulsive force generated by the interaction of torsion and fermion spin prevents the formation of a genuine singularity within a collapsing body. Matter reaches an extreme but finite density, undergoes a bounce, and expands rapidly. This bounce corresponds to the Big Bang of the resulting universe, and the rapid early expansion it generates reproduces the characteristics of cosmic inflation without any additional theoretical machinery. The model also resolves the singularity problem that has long been a headache for standard Big Bang cosmology: in Poplawski’s version, there is no point of infinite density, only a very dramatic bounce.
Now, why does this matter for the coordinate problem established above? Because a black hole event horizon, unlike any structure within the universe, possesses genuine geometric meaning as a causal boundary. It is not a statistical construction. It is not a velocity-field watershed. It is a mathematically precise surface defined by the local spacetime geometry. The parent universe, if such exists, observes our black hole’s event horizon as a fixed location in its own spacetime. From that external frame, our entire universe has a definable position and history. The cascade of positional uncertainties traced through the solar system, the galaxy, and the supercluster all occurs within the horizon. The horizon itself is the outermost fixed surface. It is the wall of the container.
The Geometry of the Trap
The proposal that the CMB constitutes the event horizon of a parent black hole carries an implication that I find simultaneously elegant and rather final with respect to the time travel question.
The interior geometry of a black hole is not merely spatially bounded. It is temporally directed. Within a black hole’s event horizon, the roles of space and time are exchanged in a specific and consequential way. All future-directed paths lead toward the central singularity. There is no trajectory within the horizon that leads back across it. Causality inside the horizon is absolutely one-directional. This is not an engineering problem. It is not a matter of insufficient energy or inadequate technology. It is a structural feature of the interior spacetime geometry, as fundamental as the requirement that time increases rather than decreases.
Poplawski has observed that the arrow of time in a universe generated within a black hole would be inherited from the parent universe through the asymmetry of matter flow across the event horizon. Our universe’s temporal directionality is not an arbitrary or unexplained feature on this model. It is a legacy of the causal structure of the parent spacetime, transmitted through the formation event. We did not choose the direction of time. We inherited it.
For the time travel question, this is rather decisive. The block universe framework may well describe the correct metaphysical structure of reality. All moments may exist with equal ontological standing. The event horizon hypothesis provides something the earlier analysis could not: a genuine fixed reference from which coordinates within the block might in principle be anchored.
The structure that provides the fixed reference, however, is precisely the structure that enforces the one-way temporal geometry of the interior. The block may be fully real. Navigation through it contrary to the direction of the temporal arrow may be structurally forbidden by the same geometry that constitutes the block’s walls. One finds the map. The map is the prison.
Conclusions, or What I Worked Out Instead of Sleeping
The line of thinking I have traced in this paper began with my ceiling, thinking of the stars beyond, satellites, and a GPS coordinate. It arrived, in the small hours of the morning, at the proposition that we are probably living within the interior geometry of a black hole, subject to its causal rules, unable to precisely locate ourselves within its four-dimensional structure, and almost certainly unable to navigate backward along the temporal coordinate even if we could. Depressing.
In my 2004 paper I concluded that time travel should not be attempted on ethical grounds, that the potential for damage to the present from even well-intentioned meddling with the past was too great to justify the attempt. I pretty much still stand by that conclusion. What the intervening twenty years of thinking have added is a deeper reason for the same position. The ethical argument says time travel should not be done. The geometric argument advanced here says it’s probably not possible to do in the first place, because the universe’s own structure forbids backward temporal navigation at the causal level… man’s technical prowess cannot overcome this.
The block universe, if it is the correct metaphysical picture, preserves every past moment at a real address within the four-dimensional manifold. Fourteen billion years of expansion, galactic motion, and cosmic rearrangement have rendered those addresses practically irrecoverable. And the interior geometry of the black hole we appear to inhabit enforces the one-way temporal direction with a rigor that no engineering has any obvious means of circumventing, so, where science fails, faith must persevere.
I find this conclusion simultaneously frustrating and rather magnificent. The universe is, in this reading, both a perfect record of everything that has ever happened and a structure that makes that record functionally inaccessible. It keeps its own history with perfect fidelity and denies us the means to read it directly. The void, as I have written elsewhere, was never empty. It turns out it was a black hole all along, and we have been living out its interior geometry since before the first atom cooled.
I think I was asleep by half past four.
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