What Einstein Missed, Part 2 — Negative Mass and the Arrow of Time
Extension of the Spacetime Penetration Velocity Hypothesis
A note on terminology. In the previous essay I used the term 'spacetime traversal velocity.' From this essay onward I replace 'traversal' with 'penetration' to more accurately carry the meaning of the original Korean term '돌파' — to break through layers rather than merely cross them.
Prologue
I wanted to break entropy.
In the Parkinson's essay I arrived at the conclusion that the reason time flows, the reason humans age, and the reason Parkinson's progresses are one face of entropy. I closed that essay with this sentence. "Entropy is humanity's current limit but will not be its eternal limit." It was a confession left without a mechanism.
I stopped. There was no way to stop aging, Parkinson's, or Alzheimer's. Each disease had its own surface problem, and beneath every surface stood a common wall. The wall was entropy. I had only named the wall. I had not broken through it.
After writing that sentence the wall kept returning to my thoughts. Naming it did not make it lower. I thought for several hours. There had to be a way to break entropy somewhere, but I could not catch hold of what it was. In the end I failed to finish the thought and went to sleep.
When I woke up, negative mass had risen in my mind.
The question was simple. If mass is the origin of time, what happens with negative mass.
Part 1 — The Question and the Current Landscape
The question
In the previous essay 'What Einstein Missed,' I arrived at the following conclusion. Gravity is not a force. Gravity is velocity. Spacetime is not a single continuum but a layered structure. Every object penetrates spacetime, and the value that describes the state of that penetration is spacetime penetration velocity. Mass is the ability to create spacetime penetration velocity. Light does not experience time because it has no mass. Without mass there is no time. Therefore mass creates time. Mass is the origin of time.
This conclusion was a bold claim in itself. Standard relativity says 'time flows more slowly for massive objects,' but it does not say 'mass is the origin of time.' I took that one step further.
Taking one step further produces the next step. If mass creates time, what does negative mass create.
What current physics knows and does not know
Negative mass has been close to a taboo concept in physics. In 1928, when Dirac solved the electron equation, half of the solutions pointed to negative energy. Rather than discarding these solutions, Dirac reconstructed them as antiparticle interpretations. Negative energy was reinterpreted not as actual matter but as the sign of antimatter. In 1957, Bondi calculated that when negative mass exists alongside positive mass, runaway motion occurs in which both particles accelerate together in the same direction forever. This result made negative mass a stranger object, but kept it as a mathematical possibility.
The experimental breakthroughs are recent. In 2017, a team at Washington State University cooled rubidium atoms to near absolute zero to form a Bose-Einstein condensate, then rotated them with a laser. At sufficient velocity the rubidium atoms behaved as if they had negative mass. When pushed, they moved as though bouncing off an invisible wall. In 2018, a team at the University of Rochester used molybdenum diselenide semiconductors and confined light to produce negative effective mass in a polariton system. In 2025, Bormashenko and colleagues reported conditions under which negative effective mass and negative effective density emerge in systems driven by entropic forces grounded in polymer elasticity.
These experiments are all effective mass. They are collective phenomena in which particles behave like negative mass inside specific systems, not cases of an independent object possessing negative gravitational mass in itself. If a rubidium atom is measured outside the condensate, it still has positive mass.
There is movement on the cosmological side as well. In 2018, Farnes proposed a modified ΛCDM model that unifies dark energy and dark matter into a single negative mass fluid. The claim is that continuously created negative mass accelerates cosmic expansion and flattens galaxy rotation curves. In 2024, analysis combining DESI baryon acoustic oscillation measurements with CMB data yielded results in which the sum of neutrino masses converges toward negative values. Various interpretations are being proposed.
There is also a rejected direction. The hypothesis that antimatter has negative gravitational mass was rejected in 2023 by the ALPHA experiment at CERN. Antihydrogen fell at the same rate as ordinary matter. Antimatter has positive gravitational mass.
What remains is this. True gravitational negative mass has never been observed. Only effective negative mass is being reproduced. The physics of true negative mass is an empty space.
Part 2 — Four Angles
Angle 1. Negative mass creates negative time
If mass is what creates time, then negative mass creates negative time.
This is not rhetorical play but a direct consequence. If time flows forward because mass has positive value, then time flows backward when mass has negative value. The sign of mass determines the sign of time.
The observation that light experiences no time because it has no mass supports this claim. When the magnitude of mass is zero, the magnitude of time is also zero. The two quantities move in the same direction. When mass crosses zero into negative values, time also crosses zero into negative values.
What happens in a region containing an object with negative mass. Around it, time is generated in reverse. Exactly symmetrically to how the environment around a positive mass object forms so that time flows forward, the environment around a negative mass object forms so that time flows backward.
How should this consequence be received. Existing physics treats the direction of time as a fixed law. The direction of entropy increase, the direction of cosmic expansion, and the direction of causality all run the same way. This fixedness was physics' premise. But if mass is the origin of time and mass can carry a sign, then the direction of time itself becomes a function of mass distribution. The direction of time is not given but made.
If mass creates time and negative mass creates negative time, two kinds of regions can exist. We, humanity, are in the positive time layer. A world where time flows forward. The world we live in. And there is a negative time layer. A world where time flows backward. A world we cannot directly know.
Angle 2. A physical mechanism for entropy reversal
The direction of entropy is the direction of time. This is the only way current physics defines the arrow of time. Energy spreads and order moves toward disorder. This direction is the flow of time. Current physics does not explain the arrow of time beyond this.
If mass creates time, and if the sign of mass determines the sign of time, then the sign of mass determines the direction of entropy. In regions of positive mass, entropy increases. Because time flows forward. In regions of negative mass, entropy decreases. Because time flows backward.
This is a physical mechanism for entropy reversal. Until now, entropy increase has been treated as an inescapable law. A refrigerator decreases its internal entropy but increases the entropy of its surrounding environment by even more. A living organism decreases the entropy of its own body but total system entropy still rises. Local decrease is possible, but fundamental reversal is impossible. This has been the consensus.
If negative mass exists, this consensus collapses. A negative mass region is not a local but a fundamental entropy-decreasing region. In such a region, disorder returns to order, diffused energy gathers again, and aged cells become young again.
In the Parkinson's essay I stopped before entropy. I presented only the direction, without a mechanism, and ended there. This angle fills that empty seat. The candidate for a physical mechanism that breaks entropy is precisely negative mass.
Angle 3. The symmetric layered structure of the negative mass world
The previous hypothesis claimed that spacetime is a layered structure. What we experience in daily life is the surface layer. Beneath it there are hidden layers, which reveal themselves only when spacetime penetration velocity becomes extreme. The reason a black hole's interior is a structure of overlapping layers rather than a singularity, and the reason two entangled quantum particles are far apart in the surface layer but at the same point in the hidden layer, both follow from this layered structure.
If negative mass exists and creates negative time, symmetry suggests that the negative mass world has the same structure. If our world has a surface layer and hidden layers, the negative mass world has a surface layer and hidden layers. When the magnitude of negative spacetime penetration velocity becomes sufficiently large — when negative mass takes sufficiently large values — the hidden layers of that world reveal themselves. The same structure as what happens in our world occurs symmetrically.
If this is correct, the universe is not a single layered structure but two mirror-image layered structures. A layered structure with positive mass and forward time. A layered structure with negative mass and reverse time. Each has its own surface and its own depth. The two structures are mirror images of each other, but they are not in direct contact.
Angle 4. The re-measurement of mass formulas
One thing must be made clear.
What we call mass, and every formula that describes it, has been derived from observations of positive mass. Newton's F=ma is the formalization of the result of applying force to objects with positive mass and measuring the acceleration. Einstein's E=mc² states the equivalence between positive mass and energy. The field equations of general relativity describe the spacetime curvature created by positive mass. The Higgs mechanism is a theory of how positive mass arises. Every historical verification of these formulas took place within the regime of positive mass. Galileo's falling body experiment, Cavendish's gravitational measurement, Eddington's eclipse observation, LIGO's gravitational wave measurement — all were events involving positive mass.
If negative mass appears, every formula for mass must be measured again in terms of negative mass. Because all current mass formulas were measured in terms of positive mass.
Here comes a common objection. Can we not simply substitute negative numbers into the formulas. Put a negative value for m in F=ma, and the directions of force and acceleration reverse. Bondi did this calculation in 1957, and runaway motion came out. Mathematically, the signs are handled.
But this objection misses the heart of the matter. Substituting a negative number into the mathematical form of a formula, and whether the form of the formula itself is valid in the case of negative mass, are different matters. The form of a formula is a product of measurement. If all measurements were made within the regime of positive mass, the form of the formula itself may be a special result of that regime. In the case of negative mass, the form of the formula may differ.
This is not a speculation but a structural demand. If positive mass and negative mass are physically distinct regimes, the laws of each regime must be independently measured and formalized. Extending the laws of one regime to the other by merely flipping signs presupposes that the two regimes are essentially the same. This presupposition has not been verified.
Part 3 — The Place I Arrived At
If negative mass is the mechanism of entropy reversal, then the problem of stopping aging, the problem of reversing the flow of time, and the problem of stopping the progression of Parkinson's all seek their answer in the same place. The three problems are one face.
Beta-amyloid and tau accumulating in Alzheimer's. Alpha-synuclein aggregating into Lewy bodies in Parkinson's. TDP-43 misfolding in ALS. Huntingtin protein forming strands in Huntington's disease. All of these are local entropy increase in proteins. And aging itself. DNA damage accumulates, mitochondria age, cellular cleanup systems slow, collagen denatures. All local entropy increase.
Current medical approaches deal with the surface mechanisms of each disease. They create antibodies that remove beta-amyloid. They develop immunotherapies to clear alpha-synuclein. They supply dopamine, inhibit cholinesterase, selectively remove senescent cells. All of these approaches clear the consequences of entropy increase. They do not reverse the increase itself. They are what happens beneath the wall called entropy.
If negative mass becomes a controllable resource, this entire picture changes. If time can be made to flow in reverse locally — at the cellular level, at the molecular level — the very category of 'wear' dissolves. There is no need to clean up. It suffices to reverse the progression. Back to before alpha-synuclein aggregated. Back to before the neuron died. Back to before the cell aged.
This is not a fantasy because the internal logic of this hypothesis points in that direction. If mass creates time, if negative mass creates negative time, and if entropy can therefore carry a sign, then local entropy reversal is not theoretically forbidden. It is only technologically impossible for now. Impossibility and prohibition are different things.
This is the place I arrived at while wanting to break entropy.
Part 4 — What Remains
True gravitational negative mass has not yet been observed. The verification of this hypothesis is the task of the future. The fact that effective negative mass is being reproduced in laboratories may serve as a starting point. But the distance between effective mass and true gravitational mass is large. How to close that distance remains the task of experimental physics.
How the hidden layers of the negative mass world reveal themselves, what form the formulas of negative mass take. This essay does not answer. The questions are left standing.
This essay points in a direction. If entropy is the direction of time, if time is the product of mass, and if mass can carry a sign, then entropy is a quantity that can be reversed. When it will be reversed, how it will be reversed, who will reverse it — these are questions for the next generation.
Entropy is humanity's current limit but will not be its eternal limit.
References
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An Seungwon / Wonbrand / https://wonbrand.co.kr