# Light Travel Time Effects and Cosmological Features

This unpublished article is a sequel to my earlier paper (also posted here asAre Radio Sources and Gamma Ray Bursts Luminal Booms?“). This blog version contains the abstract, introduction and conclusions. The full version of the article is available as a PDF file.

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Abstract

Light travel time effects (LTT) are an optical manifestation of the finite speed of light. They can also be considered perceptual constraints to the cognitive picture of space and time. Based on this interpretation of LTT effects, we recently presented a new hypothetical model for the temporal and spatial variation of the spectrum of Gamma Ray Bursts (GRB) and radio sources. In this article, we take the analysis further and show that LTT effects can provide a good framework to describe such cosmological features as the redshift observation of an expanding universe, and the cosmic microwave background radiation. The unification of these seemingly distinct phenomena at vastly different length and time scales, along with its conceptual simplicity, can be regarded as indicators of the curious usefulness of this framework, if not its validity.

#### Introduction

The finite speed of light plays an important part in how we perceive distance and speed. This fact should hardly come as a surprise because we do know that things are not as we see them. The sun that we see, for instance, is already eight minutes old by the time we see it. This delay is trivial; if we want to know what is going on at the sun now, all we have to do is to wait for eight minutes. We, nonetheless, have to “correct” for this distortion in our perception due to the finite speed of light before we can trust what we see.

What is surprising (and seldom highlighted) is that when it comes to sensing motion, we cannot back-calculate the same way we take out the delay in seeing the sun. If we see a celestial body moving at an improbably high speed, we cannot figure out how fast and in what direction it is “really” moving without making further assumptions. One way of handling this difficulty is to ascribe the distortions in our perception of motion to the fundamental properties of the arena of physics — space and time. Another course of action is to accept the disconnection between our perception and the underlying “reality” and deal with it in some way.

Exploring the second option, we assume an underlying reality that gives rise to our perceived picture. We further model this underlying reality as obeying classical mechanics, and work out our perceived picture through the apparatus of perception. In other words, we do not attribute the manifestations of the finite speed of light to the properties of the underlying reality. Instead, we work out our perceived picture that this model predicts and verify whether the properties we do observe can originate from this perceptual constraint.

Space, the objects in it, and their motion are, by and large, the product of optical perception. One tends to take it for granted that perception arises from reality as one perceives it. In this article, we take the position that what we perceive is an incomplete or distorted picture of an underlying reality. Further, we are trying out classical mechanics for the the underlying reality (for which we use terms like absolute, noumenal or physical reality) that does cause our perception to see if it fits with our perceived picture (which we may refer to as sensed or phenomenal reality).

Note that we are not implying that the manifestations of perception are mere delusions. They are not; they are indeed part of our sensed reality because reality is an end result of perception. This insight may be behind Goethe’s famous statement, “Optical illusion is optical truth.”

We applied this line of thinking to a physics problem recently. We looked at the spectral evolution of a GRB and found it to be remarkably similar to that in a sonic boom. Using this fact, we presented a model for GRB as our perception of aluminalboom, with the understanding that it is our perceived picture of reality that obeys Lorentz invariance and our model for the underlying reality (causing the perceived picture) may violate relativistic physics. The striking agreement between the model and the observed features, however, extended beyond GRBs to symmetric radio sources, which can also be regarded as perceptual effects of hypothetical luminal booms.

In this article, we look at other implications of the model. We start with the similarities between the light travel time (LTT) effects and the coordinate transformation in Special Relativity (SR). These similarities are hardly surprising because SR is derived partly based on LTT effects. We then propose an interpretation of SR as a formalization of LTT effects and study a few observed cosmological phenomena in the light of this interpretation.

#### Similarities between Light Travel Time Effects and SR

Special relativity seeks a linear coordinate transformation between coordinate systems in motion with respect to each other. We can trace the origin of linearity to a hidden assumption on the nature of space and time built into SR, as stated by Einstein: “In the first place it is clear that the equations must be linear on account of the properties of homogeneity which we attribute to space and time.Because of this assumption of linearity, the original derivation of the transformation equations ignores the asymmetry between approaching and receding objects. Both approaching and receding objects can be described by two coordinate systems that are always receding from each other. For instance, if a system $K$ is moving with respect to another system $k$ along the positive X axis of $k$, then an object at rest in $K$ at a positive $x$ is receding while another object at a negative $x$ is approaching an observer at the origin of $k$.

The coordinate transformation in Einstein’s original paper is derived, in part, a manifestation of the light travel time (LTT) effects and the consequence of imposing the constancy of light speed in all inertial frames. This is most obvious in the first thought experiment, where observers moving with a rod find their clocks not synchronized due to the difference in light travel times along the length of the rod. However, in the current interpretation of SR, the coordinate transformation is considered a basic property of space and time.

One difficulty that arises from this interpretation of SR is that the definition of the relative velocity between the two inertial frames becomes ambiguous. If it is the velocity of the moving frame as measured by the observer, then the observed superluminal motion in radio jets starting from the core region becomes a violation of SR. If it is a velocity that we have to deduce by considering LT effects, then we have to employ the extra ad-hoc assumption that superluminality is forbidden. These difficulties suggest that it may be better to disentangle the light travel time effects from the rest of SR.

In this section, we will consider space and time as a part of the cognitive model created by the brain, and argue that special relativity applies to the cognitive model. The absolute reality (of which the SR-like space-time is our perception) does not have to obey the restrictions of SR. In particular, objects are not restricted to subluminal speeds, but they may appear to us as though they are restricted to subluminal speeds in our perception of space and time. If we disentangle LTT effects from the rest of SR, we can understand a wide array of phenomena, as we shall see in this article.

Unlike SR, considerations based on LTT effects result in intrinsically different set of transformation laws for objects approaching an observer and those receding from him. More generally, the transformation depends on the angle between the velocity of the object and the observer’s line of sight. Since the transformation equations based on LTT effects treat approaching and receding objects asymmetrically, they provide a natural solution to the twin paradox, for instance.

#### Conclusions

Because space and time are a part of a reality created out of light inputs to our eyes, some of their properties are manifestations of LTT effects, especially on our perception of motion. The absolute, physical reality presumably generating the light inputs does not have to obey the properties we ascribe to our perceived space and time.

We showed that LTT effects are qualitatively identical to those of SR, noting that SR only considers frames of reference receding from each other. This similarity is not surprising because the coordinate transformation in SR is derived based partly on LTT effects, and partly on the assumption that light travels at the same speed with respect to all inertial frames. In treating it as a manifestation of LTT, we did not address the primary motivation of SR, which is a covariant formulation of Maxwell’s equations. It may be possible to disentangle the covariance of electrodynamics from the coordinate transformation, although it is not attempted in this article.

Unlike SR, LTT effects are asymmetric. This asymmetry provides a resolution to the twin paradox and an interpretation of the assumed causality violations associated with superluminality. Furthermore, the perception of superluminality is modulated by LTT effects, and explains $gamma$ ray bursts and symmetric jets. As we showed in the article, perception of superluminal motion also holds an explanation for cosmological phenomena like the expansion of the universe and cosmic microwave background radiation. LTT effects should be considered as a fundamental constraint in our perception, and consequently in physics, rather than as a convenient explanation for isolated phenomena.

Given that our perception is filtered through LTT effects, we have to deconvolute them from our perceived reality in order to understand the nature of the absolute, physical reality. This deconvolution, however, results in multiple solutions. Thus, the absolute, physical reality is beyond our grasp, and any assumed properties of the absolute reality can only be validated through how well the resultant perceived reality agrees with our observations. In this article, we assumed that the underlying reality obeys our intuitively obvious classical mechanics and asked the question how such a reality would be perceived when filtered through light travel time effects. We demonstrated that this particular treatment could explain certain astrophysical and cosmological phenomena that we observe.

The coordinate transformation in SR can be viewed as a redefinition of space and time (or, more generally, reality) in order to accommodate the distortions in our perception of motion due to light travel time effects. One may be tempted to argue that SR applies to the “real” space and time, not our perception. This line of argument begs the question, what is real? Reality is only a cognitive model created in our brain starting from our sensory inputs, visual inputs being the most significant. Space itself is a part of this cognitive model. The properties of space are a mapping of the constraints of our perception.

The choice of accepting our perception as a true image of reality and redefining space and time as described in special relativity indeed amounts to a philosophical choice. The alternative presented in the article is inspired by the view in modern neuroscience that reality is a cognitive model in the brain based on our sensory inputs. Adopting this alternative reduces us to guessing the nature of the absolute reality and comparing its predicted projection to our real perception. It may simplify and elucidate some theories in physics and explain some puzzling phenomena in our universe. However, this option is yet another philosophical stance against the unknowable absolute reality.

# The Unreal Universe — Seeing Light in Science and Spirituality

We know that our universe is a bit unreal. The stars we see in the night sky, for instance, are not really there. They may have moved or even died by the time we get to see them. This delay is due to the time it takes for light from the distant stars and galaxies to reach us. We know of this delay.

The same delay in seeing has a lesser known manifestation in the way we perceive moving objects. It distorts our perception such that something coming towards us would look as though it is coming in faster. Strange as it may sound, this effect has been observed in astrophysical studies. Some of the heavenly bodies do look as though they are moving several times the speed of light, while their “real” speed is probably a lot lower.

Now, this effect raises an interesting question–what is the “real” speed? If seeing is believing, the speed we see should be the real speed. Then again, we know of the light travel time effect. So we should correct the speed we see before believing it. What then does “seeing” mean? When we say we see something, what do we really mean?

#### Light in Physics

Seeing involves light, obviously. The finite speed of light influences and distorts the way we see things. This fact should hardly come as a surprise because we do know that things are not as we see them. The sun that we see is already eight minutes old by the time we see it. This delay is not a big deal; if we want to know what is going on at the sun now, all we have to do is to wait for eight minutes. We, nonetheless, have to “correct” for the distortions in our perception due to the finite speed of light before we can trust what we see.

What is surprising (and seldom highlighted) is that when it comes to sensing motion, we cannot back-calculate the same way we take out the delay in seeing the sun. If we see a celestial body moving at an improbably high speed, we cannot figure out how fast and in what direction it is “really” moving without making further assumptions. One way of handling this difficulty is to ascribe the distortions in our perception to the fundamental properties of the arena of physics — space and time. Another course of action is to accept the disconnection between our perception and the underlying “reality” and deal with it in some way.

Einstein chose the first route. In his groundbreaking paper over a hundred years ago, he introduced the special theory of relativity, in which he attributed the manifestations of the finite speed of light to the fundamental properties of space and time. One core idea in special relativity (SR) is that the notion of simultaneity needs to be redefined because it takes some time for light from an event at a distant place to reach us, and we become aware of the event. The concept of “Now” doesn’t make much sense, as we saw, when we speak of an event happening in the sun, for instance. Simultaneity is relative.

Einstein defined simultaneity using the instants in time we detect the event. Detection, as he defined it, involves a round-trip travel of light similar to Radar detection. We send out light, and look at the reflection. If the reflected light from two events reaches us at the same instant, they are simultaneous.
Another way of defining simultaneity is using sensingwe can call two events simultaneous if the light from them reaches us at the same instant. In other words, we can use the light generated by the objects under observation rather than sending light to them and looking at the reflection.

This difference may sound like a hair-splitting technicality, but it does make an enormous difference in the predictions we can make. Einstein’s choice results in a mathematical picture that has many desirable properties, thereby making further development elegant.

The other possibility has an advantage when it comes to describing objects in motion because it corresponds better with how we measure them. We don’t use Radar to see the stars in motion; we merely sense the light (or other radiation) coming from them. But this choice of using a sensory paradigm, rather than Radar-like detection, to describe the universe results in a slightly uglier mathematical picture.

The mathematical difference spawns different philosophical stances, which in turn percolate to the understanding of our physical picture of reality. As an illustration, let us look at an example from astrophysics. Suppose we observe (through a radio telescope, for instance) two objects in the sky, roughly of the same shape and properties. The only thing we know for sure is that the radio waves from two different points in the sky reach the radio telescope at the same instant in time. We can guess that the waves started their journey quite a while ago.

For symmetric objects, if we assume (as we routinely do) that the waves started the journey roughly at the same instant in time, we end up with a picture of two “real” symmetric lobes more or less the way see them.

But there is different possibility that the waves originated from the same object (which is in motion) at two different instants in time, reaching the telescope at the same instant. This possibility explains some spectral and temporal properties of such symmetric radio sources, which is what I mathematically described in a recent physics article. Now, which of these two pictures should we take as real? Two symmetric objects as we see them or one object moving in such a way as to give us that impression? Does it really matter which one is “real”? Does “real” mean anything in this context?

The philosophical stance in implied in special relativity answers this question unequivocally. There is an unambiguous physical reality from which we get the two symmetric radio sources, although it takes a bit of mathematical work to get to it. The mathematics rules out the possibility of a single object moving in such a fashion as to mimic two objects. Essentially, what we see is what is out there.

On the other hand, if we define simultaneity using concurrent arrival of light, we will be forced to admit the exact opposite. What we see is pretty far from what is out there. We will confess that we cannot unambiguously decouple the distortions due to the constraints in perception (the finite speed of light being the constraint of interest here) from what we see. There are multiple physical realities that can result in the same perceptual picture. The only philosophical stance that makes sense is the one that disconnects the sensed reality and the causes behind what is being sensed.

This disconnect is not uncommon in philosophical schools of thought. Phenomenalism, for instance, holds the view that space and time are not objective realities. They are merely the medium of our perception. All the phenomena that happen in space and time are merely bundles of our perception. In other words, space and time are cognitive constructs arising from perception. Thus, all the physical properties that we ascribe to space and time can only apply to the phenomenal reality (the reality as we sense it). The noumenal reality (which holds the physical causes of our perception), by contrast, remains beyond our cognitive reach.

The ramifications of the two different philosophical stances described above are tremendous. Since modern physics seems to embrace a non-phenomenalistic view of space and time, it finds itself at odds with that branch of philosophy. This chasm between philosophy and physics has grown to such a degree that the Nobel prize winning physicist, Steven Weinberg, wondered (in his book “Dreams of a Final Theory”) why the contribution from philosophy to physics have been so surprisingly small. It also prompts philosophers to make statements like, “Whether ‘noumenal reality causes phenomenal reality’ or whether ‘noumenal reality is independent of our sensing it’ or whether ‘we sense noumenal reality,’ the problem remains that the concept of noumenal reality is a totally redundant concept for the analysis of science.”

One, almost accidental, difficulty in redefining the effects of the finite speed of light as the properties of space and time is that any effect that we do understand gets instantly relegated to the realm of optical illusions. For instance, the eight-minute delay in seeing the sun, because we readily understand it and disassociate from our perception using simple arithmetic, is considered a mere optical illusion. However, the distortions in our perception of fast moving objects, although originating from the same source are considered a property of space and time because they are more complex.

We have to come to terms with the fact that when it comes to seeing the universe, there is no such thing as an optical illusion, which is probably what Goethe pointed out when he said, “Optical illusion is optical truth.”

The distinction (or lack thereof) between optical illusion and truth is one of the oldest debates in philosophy. After all, it is about the distinction between knowledge and reality. Knowledge is considered our view about something that, in reality, is “actually the case.” In other words, knowledge is a reflection, or a mental image of something external, as shown in the figure below.

In this picture, the black arrow represents the process of creating knowledge, which includes perception, cognitive activities, and the exercise of pure reason. This is the picture that physics has come to accept.

While acknowledging that our perception may be imperfect, physics assumes that we can get closer and closer to the external reality through increasingly finer experimentation, and, more importantly, through better theorization. The Special and General Theories of Relativity are examples of brilliant applications of this view of reality where simple physical principles are relentlessly pursued using formidable machine of pure reason to their logically inevitable conclusions.

But there is another, alternative view of knowledge and reality that has been around for a long time. This is the view that regards perceived reality as an internal cognitive representation of our sensory inputs, as illustrated below.

In this view, knowledge and perceived reality are both internal cognitive constructs, although we have come to think of them as separate. What is external is not the reality as we perceive it, but an unknowable entity giving rise to the physical causes behind sensory inputs. In the illustration, the first arrow represents the process of sensing, and the second arrow represents the cognitive and logical reasoning steps. In order to apply this view of reality and knowledge, we have to guess the nature of the absolute reality, unknowable as it is. One possible candidate for the absolute reality is Newtonian mechanics, which gives a reasonable prediction for our perceived reality.

To summarize, when we try to handle the distortions due to perception, we have two options, or two possible philosophical stances. One is to accept the distortions as part of our space and time, as SR does. The other option is to assume that there is ahigher” reality distinct from our sensed reality, whose properties we can only conjecture. In other words, one option is to live with the distortion, while the other is to propose educated guesses for the higher reality. Neither of these options is particularly attractive. But the guessing path is similar to the view accepted in phenomenalism. It also leads naturally to how reality is viewed in cognitive neuroscience, which studies the biological mechanisms behind cognition.

In my view, the two options are not inherently distinct. The philosophical stance of SR can be thought of as coming from a deep understanding that space is merely a phenomenal construct. If the sense modality introduces distortions in the phenomenal picture, we may argue that one sensible way of handling it is to redefine the properties of the phenomenal reality.

#### Role of Light in Our Reality

From the perspective of cognitive neuroscience, everything we see, sense, feel and think is the result of the neuronal interconnections in our brain and the tiny electrical signals in them. This view must be right. What else is there? All our thoughts and worries, knowledge and beliefs, ego and reality, life and death — everything is merely neuronal firings in the one and half kilograms of gooey, grey material that we call our brain. There is nothing else. Nothing!

In fact, this view of reality in neuroscience is an exact echo of phenomenalism, which considers everything a bundle of perception or mental constructs. Space and time are also cognitive constructs in our brain, like everything else. They are mental pictures our brains concoct out of the sensory inputs that our senses receive. Generated from our sensory perception and fabricated by our cognitive process, the space-time continuum is the arena of physics. Of all our senses, sight is by far the dominant one. The sensory input to sight is light. In a space created by the brain out of the light falling on our retinas (or on the photo sensors of the Hubble telescope), is it a surprise that nothing can travel faster than light?

This philosophical stance is the basis of my book, The Unreal Universe, which explores the common threads binding physics and philosophy. Such philosophical musings usually get a bad rap from us physicists. To physicists, philosophy is an entirely different field, another silo of knowledge. We need to change this belief and appreciate the overlap among different knowledge silos. It is in this overlap that we can expect to find breakthroughs in human thought.

This philosophical grand-standing may sound presumptuous and the veiled self-admonition of physicists understandably unwelcome; but I am holding a trump card. Based on this philosophical stance, I have come up with a radically new model for two astrophysical phenomena, and published it in an article titled, “Are Radio Sources and Gamma Ray Bursts Luminal Booms?” in the well-known International Journal of Modern Physics D in June 2007. This article, which soon became one of the top accessed articles of the journal by Jan 2008, is a direct application of the view that the finite speed of light distorts the way we perceive motion. Because of these distortions, the way we see things is a far cry from the way they are.

We may be tempted to think that we can escape such perceptual constraints by using technological extensions to our senses such as radio telescopes, electron microscopes or spectroscopic speed measurements. After all, these instruments do not haveperceptionper se and should be immune to the human weaknesses we suffer from. But these soulless instruments also measure our universe using information carriers limited to the speed of light. We, therefore, cannot escape the basic constraints of our perception even when we use modern instruments. In other words, the Hubble telescope may see a billion light years farther than our naked eyes, but what it sees is still a billion years older than what our eyes see.

Our reality, whether technologically enhanced or built upon direct sensory inputs, is the end result of our perceptual process. To the extent that our long range perception is based on light (and is therefore limited to its speed), we get only a distorted picture of the universe.

#### Light in Philosophy and Spirituality

The twist to this story of light and reality is that we seem to have known all this for a long time. Classical philosophical schools seem to have thought along lines very similar to Einstein’s thought experiment.

Once we appreciate the special place accorded to light in modern science, we have to ask ourselves how different our universe would have been in the absence of light. Of course, light is only a label we attach to a sensory experience. Therefore, to be more accurate, we have to ask a different question: if we did not have any senses that responded to what we call light, would that affect the form of the universe?

The immediate answer from any normal (that is, non-philosophical) person is that it is obvious. If everybody is blind, everybody is blind. But the existence of the universe is independent of whether we can see it or not. Is it though? What does it mean to say the universe exists if we cannot sense it? Ahthe age-old conundrum of the falling tree in a deserted forest. Remember, the universe is a cognitive construct or a mental representation of the light input to our eyes. It is notout there,” but in the neurons of our brain, as everything else is. In the absence of light in our eyes, there is no input to be represented, ergo no universe.

If we had sensed the universe using modalities that operated at other speeds (echolocation, for instance), it is those speeds that would have figured in the fundamental properties of space and time. This is the inescapable conclusion from phenomenalism.

The role of light in creating our reality or universe is at the heart of Western religious thinking. A universe devoid of light is not simply a world where you have switched off the lights. It is indeed a universe devoid of itself, a universe that doesn’t exist. It is in this context that we have to understand the wisdom behind the statement that “the earth was without form, and void” until God caused light to be, by saying “Let there be light.”

The Quran also says, “Allah is the light of the heavens and the earth,” which is mirrored in one of the ancient Hindu writings: “Lead me from darkness to light, lead me from the unreal to the real.” The role of light in taking us from the unreal void (the nothingness) to a reality was indeed understood for a long, long time. Is it possible that the ancient saints and prophets knew things that we are only now beginning to uncover with all our supposed advances in knowledge?

I know I may be rushing in where angels fear to tread, for reinterpreting the scriptures is a dangerous game. Such foreign interpretations are seldom welcome in the theological circles. But I seek refuge in the fact that I am looking for concurrence in the metaphysical views of spiritual philosophies, without diminishing their mystical or theological value.

The parallels between the noumenal-phenomenal distinction in phenomenalism and the Brahman-Maya distinction in Advaita are hard to ignore. This time-tested wisdom on the nature of reality from the repertoire of spirituality is now reinvented in modern neuroscience, which treats reality as a cognitive representation created by the brain. The brain uses the sensory inputs, memory, consciousness, and even language as ingredients in concocting our sense of reality. This view of reality, however, is something physics is yet to come to terms with. But to the extent that its arena (space and time) is a part of reality, physics is not immune to philosophy.

As we push the boundaries of our knowledge further and further, we are beginning to discover hitherto unsuspected and often surprising interconnections between different branches of human efforts. In the final analysis, how can the diverse domains of our knowledge be independent of each other when all our knowledge resides in our brain? Knowledge is a cognitive representation of our experiences. But then, so is reality; it is a cognitive representation of our sensory inputs. It is a fallacy to think that knowledge is our internal representation of an external reality, and therefore distinct from it. Knowledge and reality are both internal cognitive constructs, although we have come to think of them as separate.

Recognizing and making use of the interconnections among the different domains of human endeavour may be the catalyst for the next breakthrough in our collective wisdom that we have been waiting for.

# The Philosophy of Special Relativity — A Comparison between Indian and Western Interpretations

Abstract: The Western philosophical phenomenalism could be treated as a kind of philosophical basis of the special theory of relativity. The perceptual limitations of our senses hold the key to the understanding of relativistic postulates. The specialness of the speed of light in our phenomenal space and time is more a matter of our perceptual apparatus, than an input postulate to the special theory of relativity. The author believes that the parallels among the phenomenological, Western spiritual and the Eastern Advaita interpretations of special relativity point to an exciting possibility of unifying the Eastern and Western schools of thought to some extent.

Editor

Key Words: Relativity, Speed of Light, Phenomenalism, Advaita.

#### Introduction

The philosophical basis of the special theory of relativity can be interpreted in terms of Western phenomenalism, which views space and time are considered perceptual and cognitive constructs created out our sensory inputs. From this perspective, the special status of light and its speed can be understood through a phenomenological study of our senses and the perceptual limitations to our phenomenal notions of space and time. A similar view is echoed in the BrahmanMaya distinction in Advaita. If we think of space and time as part of Maya, we can partly understand the importance that the speed of light in our reality, as enshrined in special relativity. The central role of light in our reality is highlighted in the Bible as well. These remarkable parallels among the phenomenological, Western spiritual and the Advaita interpretations of special relativity point to an exciting possibility of unifying the Eastern and Western schools of thought to a certain degree.

#### Special Relativity

Einstein unveiled his special theory of relativity2 a little over a century ago. In his theory, he showed that space and time were not absolute entities. They are entities relative to an observer. An observer’s space and time are related to those of another through the speed of light. For instance, nothing can travel faster than the speed of light. In a moving system, time flows slower and space contracts in accordance with equations involving the speed of light. Light, therefore, enjoys a special status in our space and time. This specialness of light in our reality is indelibly enshrined in the special theory of relativity.

Where does this specialness come from? What is so special about light that its speed should figure in the basic structure of space and time and our reality? This question has remained unanswered for over 100 years. It also brings in the metaphysical aspects of space and time, which form the basis of what we perceive as reality.

#### Noumenal-Phenomenal andBrahman–MayaDistinctions

In the Advaita3 view of reality, what we perceive is merely an illusion-Maya. Advaita explicitly renounces the notion that the perceived reality is external or indeed real. It teaches us that the phenomenal universe, our conscious awareness of it, and our bodily being are all an illusion or Maya. They are not the true, absolute reality. The absolute reality existing in itself, independent of us and our experiences, is Brahman.

A similar view of reality is echoed in phenomenalism,4 which holds that space and time are not objective realities. They are merely the medium of our perception. In this view, all the phenomena that happen in space and time are merely bundles of our perception. Space and time are also cognitive constructs arising from perception. Thus, the reasons behind all the physical properties that we ascribe to space and time have to be sought in the sensory processes that create our perception, whether we approach the issue from the Advaita or phenomenalism perspective.

This analysis of the importance of light in our reality naturally brings in the metaphysical aspects of space and time. In Kant’s view,5 space and time are pure forms of intuition. They do not arise from our experience because our experiences presuppose the existence of space and time. Thus, we can represent space and time in the absence of objects, but we cannot represent objects in the absence of space and time.

Kant’s middle-ground has the advantage of reconciling the views of Newton and Leibniz. It can agree with Newton’s view6 that space is absolute and real for phenomenal objects open to scientific investigation. It can also sit well with Leibniz’s view7 that space is not absolute and has an existence only in relation to objects, by highlighting their relational nature, not among objects in themselves (noumenal objects), but between observers and objects.

We can roughly equate the noumenal objects to forms in Brahman and our perception of them to Maya. In this article, we will use the termsnoumenal reality,” “absolute reality,” or “physical realityinterchangeably to describe the collection of noumenal objects, their properties and interactions, which are thought to be the underlying causes of our perception. Similarly, we will “phenomenal reality,” “perceived or sensed reality,” and “perceptual realityto signify our reality as we perceive it.

As with Brahman causing Maya, we assume that the phenomenal notions of space and time arise from noumenal causes8 through our sensory and cognitive processes. Note that this causality assumption is ad-hoc; there is no a priori reason for phenomenal reality to have a cause, nor is causation a necessary feature of the noumenal reality. Despite this difficulty, we proceed from a naive model for the noumenal reality and show that, through the process of perception, we canderivea phenomenal reality that obeys the special theory of relativity.

This attempt to go from the phenomena (space and time) to the essence of what we experience (a model for noumenal reality) is roughly in line with Husserl’s transcendental phenomenology.9 The deviation is that we are more interested in the manifestations of the model in the phenomenal reality itself rather than the validity of the model for the essence. Through this study, we show that the specialness of the speed of light in our phenomenal space and time is a consequence of our perceptual apparatus. It doesn’t have to be an input postulate to the special theory of relativity.

#### Perception and Phenomenal Reality

The properties we ascribe to space and time (such as the specialness of the speed of light) can only be a part of our perceived reality or Maya, in Advaita, not of the underlying absolute reality, Brahman. If we think of space and time as aspects of our perceived reality arising from an unknowable Brahman through our sensory and cognitive processes, we can find an explanation for the special distinction of the speed of light in the process and mechanism of our sensing. Our thesis is that the reason for the specialness of light in our phenomenal notions of space and time is hidden in the process of our perception.

We, therefore, study how the noumenal objects around us generate our sensory signals, and how we construct our phenomenal reality out of these signals in our brains. The first part is already troublesome because noumenal objects, by definition, have no properties or interactions that we can study or understand.

These features of the noumenal reality are identical to the notion of Brahman in Advaita, which highlights that the ultimate truth is Brahman, the one beyond time, space and causation. Brahman is the material cause of the universe, but it transcends the cosmos. It transcends time; it exists in the past, present and future. It transcends space; it has no beginning, middle and end. It even transcends causality. For that reason, Brahman is incomprehensible to the human mind. The way it manifests to us is through our sensory and cognitive processes. This manifestation is Maya, the illusion, which, in the phenomenalistic parlance, corresponds to the phenomenal reality.

For our purpose in this article, we describe our sensory and cognitive process and the creation of the phenomenal reality or Maya10 as follows. It starts with the noumenal objects (or forms in Brahman), which generate the inputs to our senses. Our senses then process the signals and relay the processed electric data corresponding to them to our brain. The brain creates a cognitive model, a representation of the sensory inputs, and presents it to our conscious awareness as reality, which is our phenomenal world or Maya.

This description of how the phenomenal reality created ushers in a tricky philosophical question. Who or what creates the phenomenal reality and where? It is not created by our senses, brain and mind because these are all objects or forms in the phenomenal reality. The phenomenal reality cannot create itself. It cannot be that the noumenal reality creates the phenomenal reality because, in that case, it would be inaccurate to assert the cognitive inaccessibility to the noumenal world.

This philosophical trouble is identical in Advaita as well. Our senses, brain and mind cannot create Maya, because they are all part of Maya. If Brahman created Maya, it would have to be just as real. This philosophical quandary can be circumvented in the following way. We assume that all events and objects in Maya have a cause or form in Brahman or in the noumenal world. Thus, we postulate that our senses, mind and body all have some (unknown) forms in Brahman (or in the noumenal world), and these forms create Maya in our conscious awareness, ignoring the fact that our consciousness itself is an illusory manifestation in the phenomenal world. This inconsistency is not material to our exploration into the nature of space and time because we are seeking the reason for the specialness of light in the sensory process rather than at the level of consciousness.

Space and time together form what physics considers the basis of reality. Space makes up our visual reality precisely as sounds make up our auditory world. Just as sounds are a perceptual experience rather than a fundamental property of physical reality, space also is an experience, or a cognitive representation of the visual inputs, not a fundamental aspect of Brahman or the noumenal reality. The phenomenal reality thus created is Maya. The Maya events are an imperfect or distorted representation of the corresponding Brahman events. Since Brahman is a superset of Maya (or, equivalently, our senses are potentially incapable of sensing all aspects of the noumenal reality), not all objects and events in Brahman create a projection in Maya. Our perception (or Maya) is thus limited because of the sense modality and its speed, which form the focus of our investigation in this article.

In summary, it can be argued that the noumenal-phenomenal distinction in phenomenalism is an exact parallel to the BrahmanMaya distinction in Advaita if we think of our perceived reality (or Maya) as arising from sensory and cognitive processes.

#### Sensing Space and Time, and the Role of Light

The phenomenal notions of space and time together form what physics considers the basis of reality. Since we take the position that space and time are the end results of our sensory perception, we can understand some of the limitations in our Maya by studying the limitations in our senses themselves.

At a fundamental level, how do our senses work? Our sense of sight operates using light, and the fundamental interaction involved in sight falls in the electromagnetic (EM) category because light (or photon) is the intermediary of EM interactions.11

The exclusivity of EM interaction is not limited to our long-range sense of sight; all the short-range senses (touch, taste, smell and hearing) are also EM in nature. In physics, the fundamental interactions are modeled as fields with gauge bosons.12 In quantum electrodynamics13 (the quantum field theory of EM interactions), photon (or light) is the gauge boson mediating EM interactions. Electromagnetic interactions are responsible for all our sensory inputs. To understand the limitations of our perception of space, we need not highlight the EM nature of all our senses. Space is, by and large, the result of our sight sense. But it is worthwhile to keep in mind that we would have no sensing, and indeed no reality, in the absence of EM interactions.

Like our senses, all our technological extensions to our senses (such as radio telescopes, electron microscopes, red shift measurements and even gravitational lensing) use EM interactions exclusively to measure our universe. Thus, we cannot escape the basic constraints of our perception even when we use modern instruments. The Hubble telescope may see a billion light years farther than our naked eyes, but what it sees is still a billion years older than what our eyes see. Our phenomenal reality, whether built upon direct sensory inputs or technologically enhanced, is made up of a subset of EM particles and interactions only. What we perceive as reality is a subset of forms and events in the noumenal world corresponding to EM interactions, filtered through our sensory and cognitive processes. In the Advaita parlance, Maya can be thought of as a projection of Brahman through EM interactions into our sensory and cognitive space, quite probably an imperfect projection.

The exclusivity of EM interactions in our perceived reality is not always appreciated, mainly because of a misconception that we can sense gravity directly. This confusion arises because our bodies are subject to gravity. There is a fine distinction betweenbeing subject to” and “being able to sensegravitational force. The gravity sensing in our ears measures the effect of gravity on EM matter. In the absence of EM interaction, it is impossible to sense gravity, or anything else for that matter.

This assertion that there is no sensing in the absence of EM interactions brings us to the next philosophical hurdle. One can always argue that, in the absence of EM interaction, there is no matter to sense. This argument is tantamount to insisting that the noumenal world consists of only those forms and events that give rise to EM interaction in our phenomenal perception. In other words, it is the same as insisting that Brahman is made up of only EM interactions. What is lacking in the absence of EM interaction is only our phenomenal reality. In the Advaita notion, in the absence of sensing, Maya does not exist. The absolute reality or Brahman, however, is independent of our sensing it. Again, we see that the Eastern and Western views on reality we explored in this article are remarkably similar.

#### The Speed of Light

Knowing that our space-time is a representation of the light waves our eyes receive, we can immediately see that light is indeed special in our reality. In our view, sensory perception leads to our brain’s representation that we call reality, or Maya. Any limitation in this chain of sensing leads to a corresponding limitation in our phenomenal reality.

One limitation in the chain from senses to perception is the finite speed of photon, which is the gauge boson of our senses. The finite speed of the sense modality influences and distorts our perception of motion, space and time. Because these distortions are perceived as a part of our reality itself, the root cause of the distortion becomes a fundamental property of our reality. This is how the speed of light becomes such an important constant in our space-time.

The importance of the speed of light, however, is respected only in our phenomenal Maya. Other modes of perception have other speeds the figure as the fundamental constant in their space-like perception. The reality sensed through echolocation, for instance, has the speed of sound as a fundamental property. In fact, it is fairly simple to establish14 that echolocation results in a perception of motion that obeys something very similar to special relativity with the speed of light replaced with that of sound.

#### Theories beyond Sensory Limits

The basis of physics is the world view called scientific realism, which is not only at the core of sciences but is our natural way of looking at the world as well. Scientific realism, and hence physics, assume an independently existing external world, whose structures are knowable through scientific investigations. To the extent observations are based on perception, the philosophical stance of scientific realism, as it is practiced today, can be thought of as a trust in our perceived reality, and as an assumption that it is this reality that needs to be explored in science.

Physics extends its reach beyond perception or Maya through the rational element of pure theory. Most of physics works in thisextendedintellectual reality, with concepts such as fields, forces, light rays, atoms, particles, etc., the existence of which is insisted upon through the metaphysical commitment implied in scientific realism. However, it does not claim that the rational extensions are the noumenal causes or Brahman giving raise to our phenomenal perception.

Scientific realism has helped physics tremendously, with all its classical theories. However, scientific realism and the trust in our perception of reality should apply only within the useful ranges of our senses. Within the ranges of our sensory perceptions, we have fairly intuitive physics. An example of an intuitive picture is Newtonian mechanics that describenormalobjects moving around atnormalspeeds.

When we get closer to the edges of our sensory modalities, we have to modify our sciences to describe the reality as we sense it. These modifications lead to different, and possibly incompatible, theories. When we ascribe the natural limitations of our senses and the consequent limitations of our perception (and therefore observations) to the fundamental nature of reality itself, we end up introducing complications in our physical laws. Depending on which limitations we are incorporating into the theory (e.g., small size, large speeds etc.), we may end up with theories that are incompatible with each other.

Our argument is that some of these complications (and, hopefully, incompatibilities) can be avoided if we address the sensory limitations directly. For instance, we can study the consequence of the fact that our senses operate at the speed of light as follows. We can model Brahman (the noumenal reality) as obeying classical mechanics, and work out what kind of Maya (phenomenal reality) we will experience through the chain of sensing.

The modeling of the noumenal world (as obeying classical mechanics), of course, has shaky philosophical foundations. But the phenomenal reality predicted from this model is remarkably close to the reality we do perceive. Starting from this simple model, it can be easily shown our perception of motion at high speeds obeys special relativity.

The effects due to the finite speed of light are well known in physics. We know, for instance, that what we see happening in distant stars and galaxies now actually took place quite awhile ago. A moreadvancedeffect due to the light travel time15 is the way we perceive motion at high speeds, which is the basis of special relativity. In fact, many astrophysical phenomena can be understood16 in terms of light travel time effects. Because our sense modality is based on light, our sensed picture of motion has the speed of light appearing naturally in the equations describing it. So the importance of the speed of light in our space-time (as described in special relativity) is due to the fact that our reality is Maya created based on light inputs.

#### Conclusion

Almost all branches of philosophy grapple with this distinction between the phenomenal and the absolute realities to some extent. Advaita Vedanta holds the unrealness of the phenomenal reality as the basis of their world view. In this article, we showed that the views in phenomenalism can be thought of as a restatement of the Advaita postulates.

When such a spiritual or philosophical insight makes its way into science, great advances in our understanding can be expected. This convergence of philosophy (or even spirituality) and science is beginning to take place, most notably in neuroscience, which views reality as a creation of our brain, echoing the notion of Maya.

Science gives a false impression that we can get arbitrarily close to the underlying physical causes through the process of scientific investigation and rational theorization. An example of such theorization can be found in our sensation of hearing. The experience or the sensation of sound is an incredibly distant representation of the physical causenamely air pressure waves. We are aware of the physical cause because we have a more powerful sight sense. So it would seem that we can indeed go from Maya (sound) to the underlying causes (air pressure waves).

However, it is a fallacy to assume that the physical cause (the air pressure waves) is Brahman. Air pressure waves are still a part of our perception; they are part of the intellectual picture we have come to accept. This intellectual picture is an extension of our visual reality, based on our trust in the visual reality. It is still a part of Maya.

The new extension of reality proposed in this article, again an intellectual extension, is an educated guess. We guess a model for the absolute reality, or Brahman, and predict what the consequent perceived reality should be, working forward through the chain of sensing and creating Maya. If the predicted perception is a good match with the Maya we do experience, then the guesswork for Brahman is taken to be a fairly accurate working model. The consistency between the predicted perception and what we do perceive is the only validation of the model for the nature of the absolute reality. Furthermore, the guess is only one plausible model for the absolute reality; there may be different suchsolutionsto the absolute reality all of which end up giving us our perceived reality.

It is a mistake to think of the qualities of our subjective experience of sound as the properties of the underlying physical process. In an exact parallel, it is a fallacy to assume that the subjective experience of space and time is the fundamental property of the world we live in. The space-time continuum, as we see it or feel it, is only a partial and incomplete representation of the unknowable Brahman. If we are willing to model the unknowable Brahman as obeying classical mechanics, we can indeed derive the properties of our perceived reality (such as time dilation, length contraction, light speed ceiling and so on in special relativity). By proposing this model for the noumenal world, we are not suggesting that all the effects of special relativity are mere perceptual artifacts. We are merely reiterating a known fact that space and time themselves cannot be anything but perceptual constructs. Thus their properties are manifestations of the process of perception.

When we consider processes close to or beyond our sensor limits, the manifestations of our perceptual and cognitive constraints become significant. Therefore, when it comes to the physics that describes such processes, we really have to take into account the role that our perception and cognition play in sensing them. The universe as we see it is only a cognitive model created out of the photons falling on our retina or on the photosensors of the Hubble telescope. Because of the finite speed of the information carrier (namely light), our perception is distorted in such a way as to give us the impression that space and time obey special relativity. They do, but space and time are only a part of our perception of an unknowable realitya perception limited by the speed of light.

The central role of light in creating our reality or universe is at the heart of western spiritual philosophy as well. A universe devoid of light is not simply a world where you have switched off the lights. It is indeed a universe devoid of itself, a universe that doesn’t exist. It is in this context that we have to understand the wisdom behind the notion that “the earth was without form, and void'” until God caused light to be, by saying “Let there be light.” Quran also says, “Allah is the light of the heavens.The role of light in taking us from the void (the nothingness) to a reality was understood for a long, long time. Is it possible that the ancient saints and prophets knew things that we are only now beginning to uncover with all our advances in knowledge? Whether we use old Eastern Advaita views or their Western counterparts, we can interpret the philosophical stance behind special relativity as hidden in the distinction between our phenomenal reality and its unknowable physical causes.

#### References

1. Dr. Manoj Thulasidas graduated from the Indian Institute of Technology (IIT), Madras, in 1987. He studied fundamental particles and interactions at the CLEO collaboration at Cornell University during 1990-1992. After receiving his PhD in 1993, he moved to Marseilles, France and continued his research with the ALEPH collaboration at CERN, Geneva. During his ten-year career as a research scientist in the field of High energy physics, he co-authored over 200 publications.
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