As I listened to theoretical physicist Yasunori Nomura discuss the origins of the universe in a VAIENCE interview, I found myself pondering a sense of unease. It was the unease stemming from the question: Why is the universe so precisely tuned to values that allow for stars, galaxies, and life?Rather than focusing on memorizing a timeline, this interview addresses the fundamental question of why the laws of nature hold together without breaking down—and whether we should view this precision as inevitable or as a result of selection effects. I would like to explore the latter perspective, drawing on insights from quantum gravity and holography.
Taking a Comprehensive Look at the Discomfort of a “Too Perfect” Universe
According to Mr. Nomura’s perspective, it is important to note that the sequence of events leading to the birth of the universe can be interpreted in two different ways, depending on how we define the terms.Depending on whether we call the hot, high-density phase the “Big Bang” or use that term for the very beginning of the universe itself, the sequence of events before and after inflation appears reversed. When Einstein applied the General Theory of Relativity to the entire universe, a static universe did not emerge as a solution,and the conclusion of the theory—that only expansion or contraction was permitted—combined with the observational evidence from the recession of galaxies, which indicates that a high-temperature, high-density state existed approximately 13.8 billion years ago, to form the foundation of modern cosmology.Light from approximately 380,000 years later has been detected as the cosmic microwave background, confirming that the universe was hot and luminous at that time; however, prior to that, light could not travel in a straight line, so there are limits to what we can observe with light.
A rapid expansion caused by inflation occurred, and subsequently, the universe transitioned into the high-temperature, high-density Big Bang. This is the general sequence of events regarding the birth of the universe as conceived in modern cosmology.
This sentence describes a sequence of events: a phase called inflation, during which the universe expands while remaining cold until it reaches a size large enough for atoms to be observable; and the moment when the energy driving this inflation is converted into heat, causing elementary particles to be created and the universe to become hot.Inflation was proposed in 1981 by Sato, Goose, and others, and this theory has been repeatedly verified through the power spectrum of the cosmic microwave background.
At 380,000 years after the Big Bang, the universe was as uniform as a soup, with variations in density of only 1/100,000 between denser and less dense regions. The contrast—that while even the air in a room has irregularities, the entire universe was uniform to an accuracy of 1/100,000—intuitively conveys an extraordinary smoothness.The theory posits that these minute variations grew through gravity, with denser regions pulling on their surroundings, causing the differences to expand. This model—in which fluctuations grow through gravity—is established as a textbook fact.
If you change the rules even slightly, you end up with a universe of nothing. A universe with absolutely nothing—not just no stars, forests, lakes, or humans, but not even any galaxies. That’s why it appears to be crafted with such incredible precision. It’s so perfectly designed that you’d think you couldn’t understand it without invoking God.
According to Mr. Nomura, what this statement refers to is the precision required—specifically, that if the mass of an electron or the types of elementary particles were not exactly these values, neither stars nor galaxies could form. Rather than jumping straight to the conclusion that this is “too perfect” and attributing it to divine design, I prefer to interpret it as the narrowness of the conditions—where even a slight deviation in the values would prevent the structure from emerging.There is a view that, if there are many universes, the fact that we—living in a universe with favorable conditions—perceive this as a miracle is simply a selection effect, just as finding a suitable place by chance among the hundreds of billions of planets in the Milky Way is a matter of luck. The retrospective realization that theories developed in the 1980s for different reasons—such as string theory—included diverse universes also aligns with this perspective.However, while the multiverse hypothesis is suggestive, it lacks the certainty of the Big Bang theory, and the evidence is still developing. I intend to carry this question forward to the next chapter without setting aside this reservation.
The Invisible 70 Percent and Laws That Should Break
The next topic this dialogue addresses is the 70 percent of the universe that has yet to be fully understood—a vast blank space. Even if we count only the visible stars and gas, the total mass falls short of estimates derived from the motions of galaxies and galaxy clusters, and simulations cannot reproduce the current large-scale structure.The explanation that the picture only makes sense when an invisible component called dark matter is added carries both strong support—in the form of a mountain of evidence for its existence—and an honest reservation regarding the fact that its true nature remains unknown. When the current ΛCDM model is fitted to Planck observations, it results in a distribution where approximately 5/6 of the matter is dark matter,one-sixth is Standard Model matter, and approximately 68 percent of the total energy is dark energy—a distribution expressed by the values Ωm ≈ 0.315 and ΩΛ ≈ 0.685. I accepted this distribution as a fact: that the universe is predominantly composed of things invisible to the eye.
The “Dark” Void
According to Mr. Nomura’s explanation, the term “dark” does not refer to a specific identity but is a provisional name used to designate the unknown as such. Dark matter has not yet been directly detected, and the search for candidates such as WIMPs continues in experiments like XENON.Regarding dark energy as well, observations of supernovae around 1998 established that the expansion of the universe is accelerating rather than decelerating, necessitating a component that drives the universe outward. One candidate is vacuum energy—that is, the energy inherent in space itself, which remains even when all matter is removed.Its property of potentially acting as a repulsive force, depending on its sign, ties in with the explanation for accelerated expansion. However, this identification remains merely one of the leading candidates; it cannot be definitively concluded that it is vacuum energy itself. This is because other possibilities, such as quintessence, have not been ruled out. I value this caution as a sign of integrity—a refusal to hastily fill in the unknowns.
It is well known that a naive estimation of vacuum energy results in a value 10¹²⁰ times larger than the observed value—a problem known as the cosmological constant problem. The fact that the discrepancy between the value derived from theory and the value actually observed in the universe is so enormous carries significant weight that cannot be ignored when considering the true nature of dark energy.The two milestones—the discovery of Hubble’s recession in 1929 and the confirmation of accelerated expansion in 1998—will be remembered as milestones in the path researchers have taken to update our understanding of the universe through observation.
The Gap Between Two Revolutions
Another gap lies within the laws of physics themselves. The two revolutions that expanded Newtonian mechanics in the 20th century—the theory of relativity and quantum mechanics—each overturned everyday intuition in different ways, yet they have not yet been unified into a single theory in situations that require both fields simultaneously.
On the side of the theory of relativity, the starting point is the peculiarity that, while the Maxwell equations allow us to calculate the speed of light as approximately 300,000 kilometers per second—a speed equivalent to 7.5 laps around the Earth—it is not specified from whose perspective this speed is measured.Although the Galilean principle of Newtonian mechanics dictates that velocity should be relative, this framework requires that light alone be treated as having the same speed regardless of the observer. In 1905, Einstein accepted this requirement in his special theory of relativity and derived the consequence that time passes more slowly the faster an object moves.Furthermore, by recognizing the equivalence between acceleration and gravity, he expanded his theory into the General Theory of Relativity in 1915, describing gravity as a curvature of spacetime. This dialogue also candidly discusses the practical distinction between the two theories: using the Special Theory of Relativity—which involves simpler mathematics—when there is no need to deal with acceleration.
On the side of quantum mechanics, the stability of atoms serves as the starting point. From a classical perspective, electrons within an atom should lose energy and fall toward the center, yet in reality, they exist stably. This necessitated new rules, such as the discontinuous nature of states and the interference of multiple possibilities that overlap.Interference at double slits, discrete spectra, and the linearity of superposition are well-established properties of the microscopic world.
The problem lies in this division of labor: gravity is not included in standard quantum mechanics, and quantum effects are not included in general relativity. Both become equally important only in extremely dense and tiny regions, such as the center of a black hole or the beginning of the universe.Although this division of labor holds up in everyday life because gravity is extremely weak, the need for a single set of rules that encompasses both remains, in principle. I viewed this narrow realm of simultaneous demands as a gap where theories have yet to come together.The void of the “invisible component” and the void of the “gap in the laws.” By placing these two voids side by side, the vast unknown that lies behind the question of “too good to be true” comes into three-dimensional view.
The fluctuations predicted by quantum mechanics when that space expands wildly, the patterns of fluctuations actually observed 380,000 years later, and the statistical properties of those patterns all match perfectly.
This agreement also serves as a clue for returning to the starting point I mentioned earlier.The correspondence between the statistics of quantum fluctuations during that crazy expansion and the statistics of the 1 in 100,000 fluctuations visible 380,000 years later—which take the same form—shows that the idea of inflation is not merely a story, but is inscribed in the cosmos in a verifiable form.I intend to carry this correspondence forward to the next chapter as a concrete point of connection that fills in the gaps.
What Happens Where Gravity and Quantum Mechanics Meet
Conditions for Eliminating Infinity
According to Mr. Nomura’s explanation, if we naively combine the theory of relativity and quantum mechanics, the calculations diverge and break down, resulting in an infinite scattering probability. In a state where 1 plus 1 does not equal 2, and where this “garbage” of infinity lingers, the theory cannot be used as a prediction. However, under specific conditions, this “garbage” can be neatly reduced to zero.This involves a conceptual shift: viewing elementary particles not as points, but as strings drifting through 9-dimensional space. The vibration patterns of these strings correspond to different types of particles, and—much like the strings of a guitar—there is a correspondence where the arrangement of particles with specific masses required to eliminate infinity matches the vibration modes of the strings.This is a candidate for quantum gravity known as superstring theory. Mathematically, it becomes consistent in 10 dimensions, and in M-theory, the condition is known to be 11 dimensions. I understood this specification of the number of dimensions not as a matter of preference, but as a condition derived from the requirement to eliminate infinity.
However, this success comes at the cost of a limited scope of application. Dr. Nomura compares this to special relativity, which cannot handle acceleration. Just as special relativity is correct for uniform motion but becomes inapplicable when acceleration is introduced, superstring theory provides predictions that incorporate both gravity and quantum mechanics under limited conditions, but when these conditions are not met, there remain areas it cannot handle.It has been pointed out that many-body situations—such as black holes evaporating to produce 100 million or 10 billion particles—exceed the scope of the current formulation. I interpreted this limitation as an honest acknowledgment of the theory’s current incompleteness.
Entropy, Measured by Area
As a clue to overcoming this limitation, the dialogue delves into the entropy of black holes. Entropy is a quantity that represents the number of possible states a system can assume, and it is often described as tending toward an increase, much like ink spreading when dropped into water.From the perspective of classical general relativity alone, the region inside the event horizon is invisible from the outside and lacks any pattern, so it appears to possess no entropy. This leads to a contradiction: when an object possessing entropy is dropped into a black hole, the entropy of the entire observable universe—as seen from the outside—actually decreases.
In 1973, Bekenstein proposed a solution to this contradiction: the idea that black holes themselves possess entropy proportional to the area of their event horizon.The basis for this is the area theorem, which states that area can never decrease. If we let the areas of two black holes be A and B, and the area of the resulting merged black hole be C, then C must always be greater than the sum of A and B. This property of unilateral increase is isomorphic to the thermodynamic principle of entropy increase.It is explained that when pink water is dropped into a black hole and the black hole grows slightly larger, the increase in its area can be shown to exceed the original entropy. I interpreted this argument as an assertion that black holes are not outside the framework of thermodynamics.
It was Professor Hawking who took issue with this proposal. His skepticism stemmed from the fact that if entropy exists, there must be temperature; and if there is temperature, there should be radiation—yet black holes merely absorb matter unilaterally, he argued.Consequently, calculations were performed that patchwork-style incorporated quantum effects into general relativity, leading to the discovery that black holes possess temperature and emit radiation. This was the 1974 discovery of Hawking radiation, and the calculated temperature was consistent with Bekenstein’s entropy.The papers are known as Bekenstein’s in *Physical Review D*, Vol. 7, and Hawking’s in *Nature*, Vol. 248; the non-decrease in area is also consistently addressed within the framework of gravitational wave observations such as GW150914.
However, according to Mr. Nomura’s analysis, a profound problem emerges beyond this consistency. A black hole created by collapsing another star of the same mass would appear identical—leaving behind no information other than its mass—and since the Hawking radiation would also be identical, the difference in starting points would, in principle, vanish. This differs from the everyday irreversibility of burning a diary.In the case of a diary, information is not truly lost in the sense that, in principle, if one knew all the information—such as the positions and velocities of the molecules—one could reconstruct it by working backward through the equations.However, if Hawking’s calculations are correct, it implies that even if one starts from different initial states, the final state will be strictly the same; this was raised in the 1970s as the black hole information problem, in which the time evolution is not one-to-one and predictability is lost.I felt that the significance of this contrast lies in the fact that the loss is described not as a practical difficulty but as a fundamental loss.
Can 3 Dimensions Be Reduced to 2?
The holographic principle added a new perspective to this information problem. Its starting point lies in the puzzle that maximum entropy is proportional to area rather than volume.Normally, since the number of possible arrangements inside a box increases as it gets larger, entropy is thought to be proportional to volume. If the side length is increased tenfold, the volume should become 1,000 times larger, and the maximum entropy should also be 1,000 times greater.However, in the case of black holes, entropy scales only with area; even a 10-fold increase in size results in only a 100-fold increase in entropy. The fact that black holes—which should possess the maximum entropy in that region—only possess area-integrated entropy leads to the suggestion that the amount of information that can actually fit into three-dimensional space is equivalent to only two dimensions.
However, in the case of black holes, it appears to scale not with volume but with the area of the event horizon. This leads to the proposal that, since the amount of information contained within three-dimensional space is actually equivalent to that of two dimensions, the theory should be able to be rewritten as a two-dimensional one—and this is the fundamental idea behind the holographic principle.
This proposal extends to the view that a theory including gravity is equivalent to a theory without gravity in a dimension of one lower. The idea is that an n-dimensional theory of gravity can be rewritten as an (n-1)-dimensional theory without gravity.I viewed this operation of reducing the dimension not as an analogy to a hologram—where a three-dimensional image emerges from two-dimensional information—but as a reformulation necessitated by the way we count information.
A concrete example of this proposal was the AdS/CFT correspondence discovered by Maldacena in 1997. By studying superstring theory in anti-de Sitter space with a distant boundary, he demonstrated a correspondence in which an n-dimensional gravitational theory is equivalent to a specific n-1-dimensional theory that does not include gravity.This led to the conclusion that superstring theory exhibits holographic properties. At this point, I came to accept the view that superstring theory and holography are not two opposing concepts, but rather the names of a theory and a property, respectively.
However, there are limitations to its applicability to concrete examples. Since this correspondence holds in a specific space with a boundary—and our universe is believed not to have such a boundary—it cannot be applied directly. Removing the boundary-dependent formulation and finding a mapping that satisfies holography even in the absence of a boundary is considered the key to completing quantum gravity. Opinions diverge on this point.There are two coexisting viewpoints: one that sees clues within superstring theory itself, and another that believes we must go beyond the framework entirely; it is said that determining which is correct is still a work in progress. I felt it was more honest to acknowledge this coexistence without rushing to a conclusion.Regarding the information problem as well, while views have emerged in recent years suggesting that holographic principles are resolving the issue by showing that the original problem does not exist, this is qualified by the caveat that a complete formulation has not yet been achieved. This sense of caution is maintained throughout the entire dialogue.
Toward a Perspective That Still Cherishes the Earth, Though It Could Be Blown Away
Mr. Nomura’s background is recounted not as a grand narrative of genius, but as a series of personal encounters. He recalls that his encounter with a high school physics teacher—who gave intensive lectures on the theory of relativity and quantum mechanics, subjects not covered on entrance exams—was the catalyst that set him on the path to physics.He also recounts an anecdote from his time at the University of Tokyo’s Department of Physics and its graduate school: while showing a postdoctoral researcher from the United States around Tokyo Tower and other sites, he would pose a question, only to have it return amplified a hundredfold in the form of intense discussions—an experience that raised his standards as a researcher to a whole new level.He also reflects on how he mistakenly took the exceptional case of becoming an assistant professor at Harvard around the age of 30 as the norm, which in turn drove him to pursue his studies with even greater intensity. I interpreted this account not as a mystification of talent, but as a process in which his environment and the people he encountered raised his standards.
Building on that, the perspective this conversation ultimately arrives at is that understanding the vastness of the universe does not lead to a fall into nothingness, but rather transforms into a sense of tenderness.
“Earth is nothing more than a speck of dust that would blow away with a single breath. That’s precisely why it’s so fragile. If we don’t cherish it, we could destroy it in the blink of an eye. Since humans are such fleeting beings, we must live our lives cherishing that very fact—and it is precisely because space research reveals how insignificant we are that we come to cherish it all the more.”
The solar system is a minuscule entity within the galaxy; the galaxy itself is just one among countless galaxies; and even the universe may be just one among many. Faced with this vastness, the question arises: don’t the worries of Earth and humanity become utterly trivial?Mr. Nomura, however, takes the opposite view: he argues that precisely because we are as fragile as dust, we are vulnerable to destruction, and if we do not cherish what we have, it will be destroyed in the blink of an eye. I felt that this reversal lies at the heart of the new perspective that space research brings.The fact that the more the world expands, the smaller we become is reinterpreted not as a basis for nihilism, but as a basis for raising awareness of our fragility.
The teleological perspective often suggested by the term “fine-tuning”—that is, the interpretation that the universe is tuned for our benefit—is also known as a cognitive trap that is easily confused with the selection effect.Setting aside the discussion of the selection effect as outlined by Bostrom, I believe it is more honest toward the precision revealed by the cosmos to accept the sense of “too perfect” not as evidence of a designer’s intent, but as a result of two facts: the narrowness of the conditions and the observer’s position.The idea of inflation is etched into the cosmos in a verifiable form; a void called “dark matter” still accounts for 70 percent of it; and the gap between gravity and quantum mechanics is exposed at the extreme point of black holes.When we take in this whole picture, what remains is not an attitude of awe born of the universe’s incomprehensibly high precision, but rather an attitude that brings close to hand the fact that it is precisely because it is so precise that it is fragile.
The world appears in a new light.The fact that a fluctuation of one in 100,000 became a galaxy is not a memory of the past, but a memory of continuity—a structure that exists right here and now, grown from an infinitesimally small difference. The perspective of entropy, measured by area, and the holographic view that three dimensions might be rewritten as two, provide an opportunity to recalibrate our take for granted notion of space.And the realization that Earth is as fragile as a feather in the wind leads not to a declaration of powerlessness, but to a simple imperative: if we do not cherish it, it will be destroyed. I wish to embrace this imperative not as a distant reverence for the depths of the universe, but as a daily renewal in which I carefully tend to the fragility at my feet.
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