by Corry Shores
[The following summarizes part of chapter 4 in Bergson's Duration and Simultaneity. Paragraph headings are my own. My personal commentary is in brackets.]
The One of Time
Henri Bergson
Duration and Simultaneity
Ch. 4. Concerning the Plurality of Times
Subheading F:
L'observateur fantasmatique
Previously Bergson further elaborated his explanation for why relativity does not imply that there are multiple times, break-ups of simultaneities, or contractions of lengths. Rather, when we fully take-up relativity theory's premise that all motion is reciprocal, we thereby conclude that there is just one duration shared by all conscious observers, no matter their relative speed.
§117 The Physicist Becomes Philosopher
Bergson will now summarize the chapter. He returns to the hypothesis of the physicist on the earth. The scientist repeats over and again the Michelson-Morley experiment. But instead of him worrying about physics calculations, the physicist will now take-up the philosophical concern regarding what is real. Hence "his gaze never leaves the moving line of demarcation that separates the symbolic from the real, the conceived from the perceived. Instead of adopting the language of relativity, the physicist will now use such terms as 'reality' & 'appearance', and 'true measurements' & 'false measurements' " (80d). Nonetheless, he will adopt the theory. By translating the theory into this philosophical language, we may better evaluate it and modify it.
§118 The Constancy of Light's Motion
[Recall what the experiment sought to find. During different times of the year, the earth moves a different speed. The light apparatus of course moves with the earth. The experimenters expected the light to also move a different speed during different times of the year. But it did not. Light travels the same speed no matter how fast its origin moves. Also, they rotated the light path so that it would be moving at different angles from the earth's direction of motion. Again, light traveled the same speed in all cases. Hence,] "The speed of light is thus the same in every direction, the same for every speed of the earth" (81a). Bergson asks, why?
§119 The Physicist's World is Immobile
The physicist solves this problem by noting that motion is relative. The earth is only in motion relative to another perspective. We just as well may make the earth itself our unmoving system to which all other motion is relative.
§120 But There May be Physicists on Other Worlds
But then someone taking the perspective of another planet would see ours as the one in motion, and hence there would be no grounds to explain the common speed of light on earth as resulting from earth's immobility.
§121 Extra-Terrestrial Physicists
But the physicist on earth replies on the basis of relativity theory. He notes that the extraterrestrial observer will still measure light as moving the same speed. This is because the earth's units of time for the extraterrestrial onlooker "appear to him longer than" they appear to the earth observer. Another reason light would prove to go the same speed is because the earth observer uses rulers whose lengths have contracted. [Consider the person on earth, who synchronizes clocks at a distance. He does so by sending light to the other one, who bounces it back. They then adjust for the time light takes to make its trip for that given distance, and they synchronize their clocks accordingly. But from the perspective of someone on another planet, the earth is in motion relative to themselves. So as long as the light does not move perpendicular to the earth's motion, the distance it travels on the trip down will be different from the distance it travels on the way back. So the earth person's clocks could not really be synchronized. One of the clocks would have to lag behind the other.] The lag between clocks increases with the speed of the earth. It does so in a way that maintains a balanced inverted proportion. The faster the speed, the greater the lag. [This lagging, in a sense, gives the light more time to travel the greater distance that the earth travels with increased speed]. So the earth observer, unaware of the lag, never notices it, and he always obtains the same speed for light, because somehow the time distortions counterbalance the effects of the earth's speed.
This is the way the earth observer would reason. The conclusions accord with the extraterrestrial's observations. But what the earth observer is saying is that he obtains the correct measurements for his own system only because his own mistakes cancel each other out. This allows him to still obtain the constant speed of light. But for the extraterrestrial observer, all the earth-physicist's measurements and calculations are incorrect. Yet, let's consider if this imagined extraterrestrial observer were to come to life, and were to take his own planet as immobile. He would likewise need to also see his own calculations as mistaken, from the perspective of the earth observer, and despite the errors, he still obtains the same speed of light.
§122 Seeing Double from Too Much Relativity Theory
The relativity theorists in a way gives us double-vision, as if by pressing down on our eyeballs so that we see double. The additional image allows us to regard our own systems as a fixed reference and still bring all the other seemingly discordant ones into accord with our own;
the first image perceived, the experiment first begun, doubles into a phantasmal image where duration slows down, where simultaneity incurvates into succession, and where, for that very reason, lengths change. This diplopia, artificially induced in the experimenter, is to reassure him, or rather, to secure him against the risk he thinks he is running (which he really would be running in certain cases) in arbitrarily making himself the center of the world, in referring everything to his personal system of reference, and in nevertheless building up a physics that he would like to be universally valid. He can rest easy from now on; he knows that the laws he formulates will be confirmed, no matter from what vantage point we view nature. For the phantasmal image of his experiment, an image which shows him how this experiment would look, if the experimental device were in motion, to a motionless observer provided with a new system of reference, is no doubt a temporal and spatial distortion of the first image, but a distortion that leaves the relations among parts of the framework intact, keeps its connections and relations being precisely what we call the laws of nature. (84b.d)
§123 The Science-Fiction Phantasy of Relativity
Nonetheless, the terrestrial observer must never forget that the other observer is imagined, all while he himself is real. And yet still, the earth physicist may imagine as many of these other phantasmal observers as he pleases, in fact he may imagine "as many as there are speeds, an infinity of them" (83a).
All will appear to him as building up their representation of the universe, changing the measurements he has taken on earth, obtaining for that very reason a physics identical with his. From then on, he will work always at his physics while remaining unreservedly in his chosen observation post, the earth, and will pay them no more heed. (83a)
§124 One Giant Leap for an Imagined Man
Yet physics moves great leaps forward by positing these imaginary observers.
§125 Relativity is a Philosophical Tool.
It Proves There is Single Time and not Multiple Time,
as Many Relativity Theorists Believe
We are located on earth. From here we posit phantasmal physicists at all other locations of the universe. But for each of these phantasmal physicists there could be a real one in its place, who likewise posits other phantasmal physicists strewn about the cosmos.
But we want to know what is real. And we would like to determine if there is single time or multiple time. To do so, "We must pay no attention to phantasmal physicists, we must take account only of real physicists" (83bc). So, do all real physicists perceive the same time?
Normally a philosopher would struggle to "declare with certainty that two people live the same rhythm of duration. He cannot even give this statement a rigorous, precise meaning" (83c). Nonetheless, relativity theory allows us to do so. What we find is that in systems moving reciprocally to each other, the observers in these systems are interchangeable; "doing away with the privileged system is the very core of the theory of relativity. Hence, this theory, far from ruling out the hypothesis of a single time, calls for it and gives it a greater intelligibility" (83c, boldface mine).
Bergson, Henri. Duration and Simultaneity. Ed. Robin Durie. Transl. Mark Lewis and Robin Durie. Manchester: Clinamen Press, 1999.
The original French version is available online at:
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