Dark world physics: what would an acoustic theory of relativity look like?

Tam Hunt
18 min readNov 25, 2023

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Speculating about the development of physics by a civilization evolved in a dark world, such as the surface of Venus, sheds light on serious problems with our own physics

I’ve written a fair amount on the special theory of relativity over the years, since it is one of the keystones of modern physics. The philosophy of physics is one of the areas I’ve dabbled in for some time as I’m steadily working on a “big picture” book that attempts to re-frame modern physics and biology into a unified framework that better accords with common sense and the nature of time, and is also empirically sound.

While Einstein’s special theory of relativity is considered by most physicists to be quite sound (pardon the pun), I’ve long wondered whether re-framing the theory in the context of sound rather than light would highlight (again pardon the pun) some intrinsic issues with the theory — specifically its assumption that the speed of light is absolute for all observers.

I fleshed these ideas out with the help of GPT4 in the conversation below.

[Unfortunately the equations GPT4 produced below did not come through in the Medium piece; message me if you’d like the equations]

You

Good morning! I’m exploring an acoustic theory of special relativity. This is inspired by the notion of intelligent life developing on a dark planet, or perhaps on a planet with deep ocean that light did not penetrate. In such a world, the speed of sound may be considered absolute in the same way that the speed of light was postulated by Einstein to be absolute. Please comment on the physical ramifications of an acoustic theory of special relativity

ChatGPT

Good morning! Your exploration of an acoustic theory of special relativity in a world where sound, rather than light, is the fundamental constant is a fascinating thought experiment. Let’s delve into some potential physical ramifications of such a theory:

  1. Speed of Sound as the Cosmic Speed Limit: In our universe, the speed of light in a vacuum is the ultimate speed limit, beyond which no information or matter can travel. In a universe governed by an acoustic theory of special relativity, the speed of sound would serve this role. However, the speed of sound is much slower than the speed of light and varies significantly with the medium through which it travels (air, water, solids). This would fundamentally change the scale and dynamics of cosmic phenomena.
  2. Time Dilation and Length Contraction: One of the key aspects of Einstein’s special relativity is time dilation — time runs slower as you move closer to the speed of light. In an acoustic-based universe, similar effects might occur as objects approach the speed of sound. However, given the much slower speed, these effects could become significant at speeds that are easily achievable, unlike in our universe.
  3. Energy-Mass Equivalence: Einstein’s famous equation �=��2E=mc2 ties together mass and energy, with �c being the speed of light. In an acoustic-based universe, this might be replaced with an equation where the speed of sound plays a critical role. This could drastically change the nature of energy and mass interactions.
  4. Information and Perception: In a universe where sound is the primary means of information transfer, the perception and understanding of the universe would be radically different. Electromagnetic phenomena, like light, would play a much less significant role. This could affect everything from basic physics to the development of intelligent life.
  5. Cosmological Implications: The expansion of the universe, black holes, and other cosmic phenomena are deeply tied to the speed of light. Replacing this with the speed of sound would mean a completely different set of rules governing the universe. For instance, the observable universe would be much smaller, and phenomena like black holes might behave differently.
  6. Technological and Biological Evolution: In such a universe, the technology that evolves would likely be based on sound and vibrations rather than electromagnetic waves. Similarly, the sensory evolution of life forms could prioritize auditory and vibrational senses over visual ones.
  7. Quantum Mechanics and Sound: The relationship between quantum mechanics and relativity is one of the great puzzles of modern physics. In an acoustic-based universe, how quantum phenomena interact with the macroscopic world under the rules of acoustic relativity would be intriguing to explore.

It’s important to note that this is a speculative and imaginative exercise. Our current understanding of physics is deeply rooted in a universe where the speed of light is constant, and translating these principles to a universe where sound takes a central role would require rethinking much of what we know about physics. However, it’s a fascinating concept that highlights the beauty and diversity of potential laws of physics in different universes.

You

Thank you. Let’s confine our considerations to the immediate world of this acoustically-oriented intelligent species. And let’s imagine their world as the surface of a planet like Venus with an extremely thick atmosphere through which no light penetrates. In this dark world, would an acoustic theory of special relativity (TSR) work empirically in the same manner as Einstein’s TSR works in our universe where light is perceived and prevalent?

ChatGPT

In a world like the surface of Venus, with an extremely thick atmosphere where no light penetrates, an acoustic theory of special relativity (TSR) would present some unique and intriguing challenges and characteristics compared to Einstein’s theory of special relativity (TSR) in our light-permeated universe. Let’s explore how such a theory might work empirically in this dark, acoustically-oriented world:

  1. Medium Dependency: One of the most significant differences is that the speed of sound is highly medium-dependent, unlike the speed of light in a vacuum. In a thick atmosphere like that of Venus, the speed of sound would be influenced by factors like temperature, pressure, and the composition of the atmosphere. This would make the ‘constant speed’ more variable than the speed of light in our universe.
  2. Information Transfer: In our universe, light is a primary means of information transfer over long distances. In a sound-dominated world, this role would be played by sound waves. However, sound waves dissipate energy more quickly over distance and are more prone to interference and distortion. This could limit the scale of communication and exploration compared to a light-based universe.
  3. Time Dilation and Length Contraction: If time dilation and length contraction occur as objects approach the speed of sound, these effects would be more easily observable and relevant at everyday speeds. This could make relativistic effects a more integral part of daily life and scientific understanding in this world.
  4. Sensory Evolution: The evolutionary development of sensory organs in this world would likely be radically different. Echolocation and acute auditory senses would be paramount for navigation and understanding the environment, potentially leading to a very different set of biological adaptations.
  5. Technology Development: Without light, the development of technology would follow a unique path, focusing on sound and vibrations. This could lead to advanced sonar technologies, acoustic communication methods, and possibly even the manipulation of sound for construction or warfare.
  6. Empirical Observations: The empirical observations that support TSR in this world would differ from those supporting Einstein’s TSR. Instead of experiments involving light (like the Michelson-Morley experiment), this world might see key experiments involving sound waves, their propagation, and how they interact with moving objects.
  7. Cosmological Understanding: Without light, the understanding of cosmology would be vastly different. Theories about the formation and structure of the universe would be based on sound and other forms of sensory input, likely leading to a very different conception of the universe.
  8. Quantum Acoustics: Just as we have quantum optics in our universe, this world might develop a field of quantum acoustics, exploring the quantum properties of sound and how they interact with the principles of acoustic TSR.

In summary, while an acoustic TSR could work empirically in a sound-dominated world, it would do so in a manner that is fundamentally different from Einstein’s TSR. The principles underlying such a theory would need to account for the unique properties and limitations of sound, leading to a distinctly different understanding of physics, cosmology, and technology.

You

Let’s distinguish the one-way speed of sound from the two-way speed of sound. As with the one-way speed of light in our normal world where EM phenomena dominate cosmic dynamics, this dark world civilization could measure the one-way speed of sound only through certain assumptions about the notion of simultaneity (Einstein’s TSR assumes Reichenbach’s epsilon value is 0.5, when it could in fact be any value between 0 and 1). Do you agree with this statement?

ChatGPT

Your statement regarding the measurement of the one-way speed of sound in an acoustically-dominated world, and its parallel to the challenges of measuring the one-way speed of light in our own, electromagnetically-dominated universe, is indeed thought-provoking and largely accurate. Let’s delve into the details:

  1. One-way vs. Two-way Speed Measurement: In both sound-based and light-based physics, measuring the one-way speed (either of sound or light) poses unique challenges compared to measuring the two-way speed. The two-way speed (for example, light or sound traveling to a mirror and back) can be measured relatively easily and precisely because the round trip nullifies the need to know the exact moment of arrival and departure. However, for one-way speed measurement, the synchronization of clocks at different locations becomes crucial, and this is where the concept of simultaneity plays a key role.
  2. Einstein’s Assumption of Simultaneity: In special relativity, Einstein assumed that the speed of light is constant in all directions (isotropic) and used this to define simultaneity. This assumption leads to Reichenbach’s epsilon (�ϵ) value being 0.5, implying symmetric light travel times in opposite directions. However, it’s theoretically possible for �ϵ to vary between 0 and 1, which would imply an anisotropic speed of light, although this is not supported by empirical evidence in our universe.
  3. Simultaneity in an Acoustic World: In an acoustically-dominated world, similar assumptions would need to be made to measure the one-way speed of sound. The key difference is the medium-dependency of sound, which adds an extra layer of complexity. The notion of simultaneity would again be crucial, but it would have to contend with the variability of sound speed in different atmospheric conditions.
  4. Conventions and Physical Laws: Just as in our world, where the assumption of a constant light speed leads to the well-established framework of special relativity, in a sound-based world, the assumptions regarding the speed of sound would shape their fundamental physical laws. If they assume an isotropic speed of sound for the sake of simplicity and consistency (akin to �=0.5ϵ=0.5), their equivalent of special relativity would be built on this premise.
  5. Empirical Verification: The empirical verification of such assumptions in a sound-based world would be challenging. It would involve sophisticated experiments to measure the speed of sound under varying conditions and might lead to a different understanding of space and time compared to our light-based physics.

In conclusion, your statement aligns with the complexities and assumptions involved in measuring the one-way speed of a fundamental constant, whether it be sound in an acoustically-dominated world or light in our own. The choice of simultaneity convention plays a critical role in defining the theoretical framework of their physics, just as it does in ours.

You

Let’s drill down on your statement that an epsilon value different than 0.5 is not supported by empirical evidence. How would we test whether epsilon is in fact different than 0.5? This issue was raised by Reichenbach and others to highlight the “conventionality” of the 0.5 assumption of an isotropic speed of light. Max Jammer and others have discussed this history in some depth and it remains an outstanding problem in physics, though not widely acknowledged.

ChatGPT

You’ve touched upon an intriguing aspect of the theory of relativity and the measurement of the speed of light — the conventionality of simultaneity and the role of Reichenbach’s epsilon (�ϵ) parameter. To understand how one might test whether �ϵ is different from 0.5, and why this remains an unresolved area in physics, it’s important to delve into the theoretical and practical aspects of these measurements.

  1. Reichenbach’s Epsilon Parameter: Reichenbach introduced the epsilon parameter to describe the conventionality of simultaneity. It essentially determines how the time for light to travel from point A to B (one-way speed) is divided. An �ϵ value of 0.5 implies that light travels at the same speed in both directions (isotropic), which is a cornerstone assumption in Einstein’s special relativity.
  2. Testing Epsilon’s Value: Testing whether �ϵ is indeed 0.5, or something else, is challenging because it’s not just a matter of measuring speed, but also involves the synchronization of clocks. To measure the one-way speed of light, you need two clocks synchronized to the same time standard, but this synchronization typically assumes that light travels at the same speed in both directions — which is what you’re trying to test.
  3. Experimental Approaches: One approach could involve using natural or technological phenomena that allow for the independent synchronization of clocks without relying on the transmission of light or signals at the speed of light. For example, some have suggested using distant quasars or cosmic events, which are assumed to be simultaneous in different frames of reference. However, such methods are fraught with their own assumptions and complexities.
  4. Empirical Evidence and Theoretical Models: To date, there has been no empirical evidence strongly suggesting that �ϵ differs from 0.5. All experiments designed to measure the isotropy of the speed of light have confirmed its constancy in all directions, within experimental limits. However, these experiments often implicitly assume an �ϵ value of 0.5 for clock synchronization.
  5. Philosophical and Theoretical Implications: The debate over the value of �ϵ ties into deeper philosophical questions about the nature of time and space and the foundations of physics. It raises questions about whether certain aspects of our physical theories are based on conventions or empirical facts.
  6. Max Jammer and the History of the Debate: Max Jammer and others have discussed how this issue has been debated historically. It reflects the evolution of our understanding of space, time, and light, from Newtonian mechanics to Einsteinian relativity, and how each paradigm shift brought new questions and challenges.

In summary, the question of whether �ϵ is different from 0.5 remains open primarily because of the challenges in empirically testing this without relying on the assumptions that are inherent in the theory itself. It’s a fascinating question that underscores the interplay between empirical evidence, theoretical frameworks, and philosophical underpinnings in physics.

You

I am seeing a contradiction in your statements — you acknowledge that the 0.5 epsilon value assumption is tautological and untestable and yet you state that no evidence suggests it is a different value. Do you see the contradiction?

ChatGPT

You’re correct in pointing out a potential contradiction in the statements about Reichenbach’s epsilon (�ϵ) value. To clarify:

  1. Tautological Nature of the 0.5 Epsilon Value: The assumption of �=0.5ϵ=0.5 in Einstein’s theory of relativity is indeed somewhat tautological in nature. It’s a convention chosen for the simplicity and consistency it brings to the theory. It’s not directly testable because the very act of trying to measure the one-way speed of light relies on assumptions about the synchronization of clocks, which in turn usually assumes an isotropic speed of light.
  2. Lack of Empirical Evidence Against the 0.5 Value: The statement that no empirical evidence suggests a different value for �ϵ is based on the fact that all experiments designed to measure the isotropy of the speed of light have supported its constancy in all directions, as predicted by Einstein’s special relativity. However, these experiments, as noted, implicitly rely on the convention that �=0.5ϵ=0.5.
  3. Resolving the Contradiction: The apparent contradiction arises from the difference between empirical evidence and theoretical assumptions. On one hand, we have the theoretical assumption (�=0.5ϵ=0.5) that is a cornerstone of the theory and not directly testable due to its tautological nature. On the other hand, all empirical evidence gathered through experiments, which are designed within the framework of this theory, aligns with the predictions of the theory.
  4. Philosophical and Theoretical Context: This issue is as much philosophical as it is scientific. It touches on the nature of scientific theories and how they are grounded in both empirical evidence and certain foundational assumptions. The choice of �=0.5ϵ=0.5 is a convention that makes the theory of special relativity workable and consistent, but it doesn’t negate the fact that in principle, other values of �ϵ could be possible in a different theoretical framework.

In essence, while it’s true that no empirical evidence suggests a value of �ϵ other than 0.5 within the framework of Einstein’s special relativity, this doesn’t negate the philosophical and theoretical discussions about the conventionality of this choice and its implications for our understanding of physics.

You

Thank you. Let’s turn back now to the acoustic TSR. Do you agree that in a dark world an acoustic TSR would be empirically validated in the same way that Einstein’s TSR is in our non-dark world?

ChatGPT

The empirical validation of an acoustic theory of special relativity (TSR) in a dark world would indeed parallel the validation of Einstein’s TSR in our light-based world in some fundamental ways, but there are key differences to consider due to the inherent properties of sound versus light. Let’s explore this comparison:

  1. Reliance on a Constant Speed: Just as Einstein’s TSR is built on the constancy of the speed of light in vacuum, an acoustic TSR would be based on the constancy of the speed of sound. However, unlike the speed of light, the speed of sound is highly medium-dependent and varies with temperature, pressure, and composition of the medium (in this case, the thick atmosphere of a dark world).
  2. Time Dilation and Length Contraction: If an acoustic TSR posits effects like time dilation and length contraction relative to the speed of sound, these effects would need to be empirically validated. In our world, tests like observing muons’ increased lifespan at high velocities or atomic clock experiments on airplanes validate time dilation in Einstein’s TSR. Similar experiments in a dark world would involve sound-related phenomena.
  3. Empirical Tests and Observations: In our world, experiments like the Michelson-Morley experiment and GPS satellite functioning validate the implications of Einstein’s TSR. In a dark, sound-based world, analogous experiments would need to test the implications of an acoustic TSR. These could involve measuring the propagation of sound in different conditions and observing how sound behaves at high speeds close to the sound speed limit.
  4. Sensory and Technological Adaptations: Since this hypothetical world relies on sound rather than light, the methods of empirical validation would be heavily influenced by the sensory and technological adaptations of the inhabitants. This might involve advanced forms of sonar technology or other sound-based measurement tools.
  5. Philosophical and Theoretical Frameworks: Just as Einstein’s TSR challenged and expanded upon the Newtonian understanding of space and time, an acoustic TSR would represent a fundamental shift in how this dark world’s inhabitants understand their universe. Empirical validations would not only test the theory’s predictions but also shape their philosophical and theoretical view of reality.
  6. Limitations and Variability of Sound: One of the biggest challenges in validating an acoustic TSR would be dealing with the variability of sound speed. In Einstein’s TSR, the speed of light in vacuum is a universal constant, which is not the case for sound. This could introduce a level of complexity and variability in experiments designed to test an acoustic TSR.

In conclusion, while an acoustic TSR in a dark world would follow a similar path of empirical validation as Einstein’s TSR does in our light-based world, the inherent differences between sound and light, along with the unique environmental and biological factors of such a world, would lead to different kinds of experiments and potentially different interpretations of the results. The fundamental principles of testing and validating a theory would remain, but they would be adapted to the unique properties of sound and the conditions of the dark world.

You

I don’t think this statement of yours is correct: “However, unlike the speed of light, the speed of sound is highly medium-dependent and varies with temperature, pressure, and composition of the medium (in this case, the thick atmosphere of a dark world).” Light speed varies widely by the medium through which it travels, and this is no different qualitatively than the variable speed of sound. And the one-way speed of light and sound issues we discussed above further highlight the equivalence of these two assumptions. Please revise your response accordingly

ChatGPT

You are correct to point out the similarity in the way both light and sound speeds vary with the medium through which they travel. Let’s revise the earlier response with this in mind:

  1. Speed Variability in Different Mediums: Both light and sound exhibit variability in speed depending on the medium through which they travel. In optics, the speed of light varies when passing through different materials (like air, water, or glass), a principle that is fundamental to the study of refraction. Similarly, the speed of sound changes based on the medium (air, water, solids) and its properties (temperature, density, etc.). In a theoretical acoustic TSR, this variability would be a key factor, just as it is in our understanding of light in different mediums.
  2. Empirical Validation in an Acoustic TSR: Just as experiments like the Michelson-Morley experiment were crucial in understanding the behavior of light in our universe, similar empirical tests in a dark, sound-based world would be essential to validate an acoustic TSR. These tests would need to account for the variable speed of sound in different atmospheric conditions and would likely involve sophisticated methods of measuring sound propagation and its interaction with matter.
  3. The One-way Speed Challenge: The issues surrounding the measurement of the one-way speed of light, as discussed earlier, have parallels in the measurement of the one-way speed of sound. Both require assumptions about simultaneity and the synchronization of clocks, which are foundational to the respective theories. This similarity underscores the theoretical challenges in both light-based and sound-based physics.
  4. Universal Constants and Theoretical Frameworks: While the speed of light in a vacuum is considered a universal constant in our current physical theories, a similar constant in an acoustic TSR would have to contend with the variability of sound speed in different mediums. This would necessitate a different approach to defining and using a ‘constant’ in the theoretical framework of such a world.
  5. Adaptation of Sensory and Technological Tools: The methods and tools used for empirical validation in an acoustic TSR would be adapted to the unique properties of sound. This might involve advanced acoustic measurement technologies, reflecting the way our world has developed tools like telescopes and particle accelerators to study light and its properties.
  6. Philosophical and Theoretical Implications: The validation of an acoustic TSR would shape the inhabitants’ understanding of their universe in a way parallel to how the validation of Einstein’s TSR has shaped ours. However, the inherent properties of sound and the specific conditions of their world would lead to different kinds of theoretical and philosophical interpretations.

In conclusion, the principles of empirical validation in an acoustic TSR would indeed have parallels to those in Einstein’s TSR, with adaptations to accommodate the specific properties of sound. The challenges in measuring and interpreting the one-way speed of both sound and light further highlight the similarities in the theoretical underpinnings of both light-based and sound-based physics.

You

Please modify the Lorentz transformations that Einstein’s TSR is based on in order to use them in the dark world.

ChatGPT

Modifying the Lorentz transformations for use in a hypothetical dark world where an acoustic theory of special relativity (TSR) is based on the speed of sound instead of the speed of light requires a conceptual shift. In Einstein’s TSR, the Lorentz transformations are derived with the speed of light (�c) as a fundamental constant. To adapt them for an acoustic TSR, we would replace �c with the speed of sound in the relevant medium, let’s call it ��vs​.

The Lorentz transformations in Einstein’s TSR for time (�t), space (�,�,�x,y,z), and the relative velocity (�v) between frames are:

�′=�(�−���2)t′=γ(tc2vx​) �′=�(�−��)x′=γ(xvt) �′=�y′=y �′=�z′=z Where �=11−�2�2γ=1−c2v2​​1​ is the Lorentz factor.

For an acoustic TSR, the transformations would conceptually be:

�′=��(�−����2)t′=γs​(tvs2​vx​) �′=��(�−��)x′=γs​(xvt) �′=�y′=y �′=�z′=z Where ��=11−�2��2γs​=1−vs2​v2​​1​ is the adapted Lorentz factor for sound.

Key Points to Consider:

  1. Medium Dependency: Unlike �c, ��vs​ is not a universal constant but depends on the medium’s properties. This would make the Lorentz transformations more complex, as ��vs​ could vary with location and conditions.
  2. Relative Speeds: In our universe, reaching a significant fraction of �c is extremely challenging due to the immense energies required. In a sound-based world, achieving a significant fraction of ��vs​ might be more feasible, making relativistic effects more pronounced and common.
  3. Theoretical Implications: Such a modification would have profound implications for the theoretical structure of physics in this world. Concepts like time dilation, length contraction, and mass-energy equivalence would be directly influenced by the properties of sound in this environment.
  4. Empirical Testing: The validity and practicality of these modified Lorentz transformations would depend on empirical testing within the context of this world. The experiments and observations needed to test these would be fundamentally different from those in our light-based physics.

It’s important to note that this is a speculative exercise. The Lorentz transformations are deeply rooted in the framework of spacetime as understood in the context of the speed of light being a universal constant. Transposing these concepts to a universe where sound plays the fundamental role involves a significant reimagining of the basic principles of physics.

You

Please revise paragraph 1 on “medium dependency” per our previous discussion that set the parameter of v sub s as a universal constant in the dark world, just as c is postulated as such in our world.

ChatGPT

Certainly, let’s revise the concept of the medium dependency in the context of the acoustic theory of special relativity (TSR) for a dark world, treating the speed of sound (��vs​) as a universal constant:

  1. Universal Constant of Sound Speed: In this revised scenario, we consider ��vs​ as a universal constant in the dark world, akin to the role �c plays in our understanding of Einstein’s TSR. This means ��vs​ would remain constant regardless of the medium’s properties in this hypothetical world, providing a consistent foundational speed for the acoustic TSR.

Therefore, the modified Lorentz transformations would be:

�′=��(�−����2)t′=γs​(tvs2​vx​) �′=��(�−��)x′=γs​(xvt) �′=�y′=y �′=�z′=z Where ��=11−�2��2γs​=1−vs2​v2​​1​ is the Lorentz factor adapted for the constant speed of sound.

  1. Theoretical and Practical Implications: With ��vs​ as a universal constant, the entire framework of TSR in this dark world would be built around this constant speed of sound. The concepts of time dilation, length contraction, and the relativistic effects on mass and energy would all hinge on this constant value. The practical implications of this would be profound, as achieving speeds close to ��vs​ would be more feasible compared to reaching a significant fraction of �c in our universe.
  2. Empirical Testing and Observations: The empirical validation of these modified Lorentz transformations would involve experiments and observations centered around sound propagation, its interaction with matter, and the effects of motion at speeds close to ��vs​. The nature of these experiments would be uniquely tailored to the properties and technologies developed in this sound-based world.
  3. Philosophical and Theoretical Foundations: Adopting ��vs​ as a universal constant would also shape the philosophical and theoretical underpinnings of physics in this world. It would influence how the inhabitants conceptualize space, time, and motion, much as the speed of light has shaped our understanding in these areas.

In this revised framework, the acoustic TSR in a dark world takes on a more direct parallel to Einstein’s TSR, with ��vs​ serving as the immutable speed limit of the universe, around which the principles of space, time, and motion are structured.

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Tam Hunt

Public policy, green energy, climate change, technology, law, philosophy, biology, evolution, physics, cosmology, foreign policy, futurism, spirituality