The Speed of Light

Contents

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Acknowledgments

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pp. xi-xii

Every author grows blind to the manuscript he or she writes, and so fresh eyes are always welcome. I thank an anonymous reviewer at Indiana University Press for meticulously correcting errors and proposing new directions and emphases. I similarly thank Sienna Dittmer, Ace Sorensen, Chad McKell, and Marc-Charles Ingerson...

Introduction

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pp. 1-9

Years ago I learned something that has bothered me ever since: the speed of light is constant in all inertial reference frames.¹ This is a simple fact of science, easy to state and easy to remember. Its scientific implications, however, are enormous. What is more, from a commonsensical point of view, it makes no sense. Here is how David...

1. Space, Time, and Light Speed Constancy

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pp. 10-22

Space and time are notoriously hard to define. That, perhaps, is because they seem mostly blank or featureless. Space appears expansive and three-dimensional, time linear and irreversible. We do not actually observe these qualities, however. We infer them from events that supposedly occur in space and time. It is as if space contains...

2. Special Relativity

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pp. 24-35

Einstein’s decision to assign a constant measured value to the speed of light is significant in two interrelated ways. First, it sets the motion of light apart from the motion of material bodies. The two kinds of motion are no longer comparable. Think of a vehicle moving inertially through space at 600 miles per hour. Even if this velocity...

3. Horizonal Light

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pp. 36-47

By now the constancy of the speed of light should be well established. It should also be clear that that constancy necessitates new understandings of space and time. And this latter realization prompts consideration of the claim that light moves at 186,000 miles per second. While we are used to talking about phenomena in this way, we are...

4. Experiential Light

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pp. 48-58

When two colors are perfectly blended together, constancy or homogeneity replaces difference or heterogeneity. Something like that appears to occur with light speed constancy. Light is such that we cannot see it without seeing by it, a fact that keeps us from separating light from our experience of light—the two are coincidental...

5. Relational Light

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pp. 60-69

T. S. Eliot once wrote of “a music heard so deeply that it is not heard at all.”¹ I am saying something similar about light. Light, I believe, is so deeply informative of our nature that we cannot bring it forward in a detached, informational way. Expressed differently, as the very coin of illumination and understanding, light cannot be traded...

6. Internal Relations

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pp. 70-84

The last chapter depicted light as a relational phenomenon. I have suggested that light is not a thing among other things; it is a unifying relationality that enables the identification of one thing vis-à-vis another. The constancy or steadfastness of light is a fixed basis from which various things emerge. Absent this basis, there would be no...

7. Light in a Vacuum

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pp. 86-95

Before going further, we need to remind ourselves that the speed of light as it normally figures into physics is the speed of light in a vacuum. Light slows down as it moves through physical media like glass and water, and so its speed is not constant under all circumstances. When, however, light travels in vacuo, all inertial observers...

8. Ambient Light

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pp. 96-113

Earlier we observed that motion, at first blush one of the most obvious of all experiences, is deceptively complex. This observation applies with particular cogency to light’s motion, which since Einstein cannot be straightforwardly compared to the motion of material bodies. But even before Einstein it was not obvious that light...

9. Pre-reflective Experience

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pp. 114-126

“The most incomprehensible fact about the universe is that it is comprehensible,” said Einstein.¹ This statement captures his belief that the world is congenial to our curiosity about the world. Mind and cosmos are on the same page—otherwise each would be inaccessible to the other. Einstein never said this precisely and in fact...

10. Body, World, and Light

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pp. 128-144

Often linked with James Gibson, whom he may have influenced, Maurice Merleau-Ponty sought to describe perceptual experience while eschewing talk of sense data, photons, retinas, and rods and cones (“with only myself to consult, I can know nothing about this”).¹ His insights underscore subject-object and object-object...

11. Existential Light

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pp. 146-165

Although Husserl sought to return philosophy “to the things themselves,” to a world untouched by undue philosophical complication, some argue that he failed to accomplish this. As he continued to wrestle with fundamental issues, he seems to have shifted back to the notion of mind surveying the world from a privileged...

Notes

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pp. 167-180

Bibliography

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pp. 183-189

Index

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pp. 191-197