B. Space itself is changing because matter distorts it, a phenomenon that can be understood when we describe how gravity works within the context of the theory of general relativity.
Gravity, in general relativity, is explained by giving space geometrical properties, namely, by regarding it as a flexible medium distorted by matter—like a trampoline surface that is stretched and warped by a bowling ball resting or moving on it. In the case of the earth and the sun, for example, the distortion of space caused by one body influences the motion and is felt as gravity by the other.
In a simplified analogy, the flexible trampoline fabric (which plays the role of space) is curved when a bowling ball (which plays the role of the sun) rests on it. The geometry (shape) of the fabric depends on (1) the mass of the bowling ball and (2) the distance from it: (1) the more the mass, the more curved the fabric (space) becomes; (2) the closer to the bowling ball, the greater is the curvature of the fabric. The distorted fabric in turn influences the motion of a small marble (which plays the role of the earth) rolling on it. Depending on how we start the marble moving (i.e., with what initial speed and direction, and from what location), it will move on the distorted fabric by following a particular path (circle, ellipse, parabola, spiral, toward the bowling ball, etc.), and thus will appear to be attracted by the bowling ball. For example, a marble released from rest moves on the distorted fabric caused by the bowling ball and plunges onto it, like an apple falls from its tree onto the ground by moving through the distorted space caused by the earth. Newton thought the apple is attracted by the earth—although how, really, the apple knows that the earth is below in order to fall, he didn’t know. Einstein figured it out because he reimagined gravity: just as the marble is pushed by the curved fabric of the trampoline and appears to be attracted by the bowling ball, the apple is pushed by the curved fabric of space-time—by the curvature, the geometry, of space-time—and appears to be attracted by the earth. Gravity is the geometry of space-time. In the trampoline analogy the distorted fabric is gravity; and the greater the bowling ball mass, or the smaller the distance from it, the stronger gravity (the distorted space-time) becomes.
In the earth-sun case, the sun distorts the spatial fabric around it (and time, too—it passes more slowly as one gets closer to the sun, or any other object in general). Traveling at the speed of light, this distortion reaches and affects the motion of the earth—analogously, a water disturbance, a water wave, travels in the sea but with a much smaller speed. In turn, the earth traverses the distorted space as if space pushes the earth through it. Of course, the earth distorts the space around itself, too (although its smaller mass produces a much smaller distortion than that of the sun); and so do the moon, planets, stars, and galaxies. Gravity is really the twists, curves, ripples, bumps, depressions, and in general all these distortions (the changing geometry) of space-time. And each body’s motion is actually a response to the space distortions from all other bodies around it. Because these bodies are in constant motion in the universe, the pattern (the geometry) of space distortions that they create is in a state of constant flux—and so the motion of matter causes change in the geometry of space. In our analogy, as it rolls, the bowling ball transfers the warping of the trampoline surface to different locations. Because both space and time are distorted by matter, space-time in general relativity becomes a four-dimensional malleable (distortable) continuum. In turn, these space-time distortions, which we usually call gravity, influence the motion of matter.
C. In addition to its constant warping, space as a whole is also expanding according to the big bang cosmology, thereby carrying all the galaxies with it and causing them to move away from each other. Here again, motion, which in this case is a consequence of the expansion of space, produces change. Known as the expansion of the universe, this was first predicted theoretically by the solutions of the equations of general relativity, shortly after their publication in 1916. It was later confirmed experimentally by astronomer Edwin Hubble (1889–1953) in 1929 when he observed a redshift in the light emitted by the distant galaxies. The redshift is a measure of the relative velocity between a galaxy and the earth. Specifically, it means that distant galaxies are rapidly receding from us. The greater the distance, Hubble discovered, the faster the recession speed, a result known as Hubble’s law. This law is included in the big bang model.
Galaxies are not moving out into preexisting space, a common misinterpretation of the phenomenon of expansion, but they are moving away relative to each other, and what carries them is space itself as it is expanding (stretching); the result is that the size of the universe is increasing with time. Furthermore, the recession of galaxies does not make the earth the center of the universe or in any way a more special place than any other. Quite the opposite, because the universe is isotropic, the expansion would look the same from any location in the universe. In a classic analogy, imagine how any dot (i.e., galaxy) on an inflating balloon is seen receding from the perspective of any other dot as the expanding membrane (i.e., space) itself carries all dots with it. Since galaxies are observed receding from each other and the universe to be expanding, in the past they must have been closer to each other, and the universe must have been much smaller—imagine our balloon to be deflating. In the extreme case, the whole universe (all the galaxies, all matter, energy, and space, even time) is imagined to have been a mere point, its explosion of which is the premise of the big bang model. Whether such a point-like universe actually existed is still only a hypothesis, and why it exploded is still puzzling. Nonetheless, we do know that the universe must have been very, very small (if not point-like) when it exploded, as described by the big bang theory, and that it has been constantly expanding (stretching), thus changing ever since.
(2) Transformations Cause Change
Transformations of matter and energy also cause change in the various qualities of objects (or the universe in general) via two types of processes: first, when the various particles of energy convert into particles of matter, back and forth, materializing and dematerializing; and second, when one type of material particle converts into another. An example of the former is the materialization of the energy of invisible gamma rays into an electron-positron pair, or the dematerialization of such pair into the energy of gamma rays; and an example of the latter is the conversion of two protons into a proton-neutron nucleus (a heavy form of hydrogen called deuterium), a positron, and an elusive neutrino (all common reactions in the stars energizing them with their light). Of course, more everyday-type transformations of matter and energy, such as from solid to a liquid (as the melting of ice) or liquid to a gas (as the evaporation of water), also cause change.
But things are not merely changing; they are constantly changing, a conclusion required by the uncertainty principle.
Change Is Constant
To avoid violating the uncertainty principle, motion in nature must be perpetual. If a particle could sit still, it would mean that its velocity would be exactly zero and so then would be the uncertainty in its velocity. Consequently, the product of the position and velocity uncertainties would also be zero, a result in violation of the Heisenberg uncertainty principle. The principle holds only if motion is perpetual. A particle cannot sit still, ever. This result is also supported by the third law of thermodynamics, which states that the absolute zero—the lowest temperature for which every particle in a substance would have been motionless—is unattainable (temperature is a measure of particles’ average energy of motion). Now, since the motion of particles is perpetual, so is change. Incidentally, since motion is constant, then motion is also involved even when change is caused by the transformations between the particles of matter and the particles of energy.
Support of the “constant change” view comes also from the expansion of the universe that has been happening ever since the big bang. What’s more, the space-time continuum fluctuates constantly at microscopic scales, like a turbulent sea—the distortions of space are changing violentl
y—a phenomenon resulting from efforts to reconcile the theory of general relativity with the uncertainty principle of quantum theory.
Change Is Unidirectional
But change is not merely constant; it is also unidirectional, meaning nothing is ever the same; “you could not step twice into the same river.”10 Heraclitus parallels the constant unidirectional change in nature to the ever-changing waters in a river. If the state of a river at one moment were ever the same as the state at another moment, it would have been possible for one to step twice into the same river. Since one cannot do that, nothing ever is the same, and so change is not only constant; it is also unidirectional. In fact, one “could not step twice into the same river” not only because a river’s waters are ever-changing, but also because one’s own body is also ever-changing. Everything is constantly changing, and nothing is ever the same. Parenthetically, we think we are the same individual throughout life, but I have always wondered, what happened to that 10-year-old boy that I once was? I’m obviously (physically) not the same, but am I still the same individual (being)? Einstein, we’ll see in the next chapter, claims that every moment of my existence (in some sense) still exists, and such a surreal claim has the support of the bold logic of Parmenides!
Now, according to the second law of thermodynamics, net entropy—the degree of disorder (randomness) in the universe—is always increasing. Think of the universe as a jigsaw puzzle. There are more disorderly arrangements than ordered ones (and only one of the perfect picture). Had I dropped the pieces on the floor, the likelihood to form a disorderly pattern is much higher than that of the perfect picture. This likelihood becomes ever more accurate with ever more jigsaw pieces. The universe, like the puzzle, has vastly more disorderly configurations than ordered ones, so naturally with time the universe’s entropy increases. Thus, nature is in a state of becoming, but it is a disorderly becoming.
Indeed, then, everything is constantly changing, and nothing is ever the same! Heraclitus’s doctrine of change includes everything, even the seemingly unchanging, such as a rock in its apparent state of rest or even a human body. In fact, even the gradual biological evolution by descent and variation—that the more complex life forms do not arise spontaneously but evolve from simpler ones through modifications—is a principle to be expected as a consequence of the Heraclitean theory of constant change.
Nature as a Process
Heraclitean View
A profound consequence of the Heraclitean theory of universal constant change is the view of nature as a process made up of events. For the notion of “a thing” is inconsistent with a theory of constant change. To be able to be spoken of and defined, the thing must remain absolutely the same for at least a period of time; it must have some permanence and must be identifiable. But the notions of sameness and changelessness are contradictory to a theory of constant change. Consequently, it is more appropriate to consider a thing as an event (something happening somewhere at some instant of time) and not as something permanent. Thus, what changes is not something material or initially permanent; what changes are the events. Groupings of events constitute processes, which in turn make nature the ultimate process.
Quantum View
This notion is supported by quantum theory. We will argue that microscopic particles are better understood to be events rather than permanent things.
We learned earlier that because of the uncertainty principle observations are disconnected events. Now, without continuity in observation, without the ability to keep a particle under continuous observation (even for the smallest time duration), how can we establish its identity or permanence? With time (and space) gaps between observations during (and within) which we cannot see what a particle is doing, how can we be sure whether, say, an electron observed at location A has moved there from location B, or whether it is really one and the same electron as that observed at location B, regardless of their proximity? We cannot! Since observations are disconnected events, consecutive observations of identical particles—such as electrons, all of which have the same intrinsic properties, for example, charge, spin, rest mass—might in fact be observations of two different particles belonging in the same family (e.g., two different electrons), and not observations of one and the same particle (e.g., the same electron) that has endured for a certain period of time. It is therefore impossible to ever determine whether the observations of two identical particles could actually be observations of one and the same particle, and consequently whether a particle endures for a period of time.
So without the ability to keep a particle under continuous observation, it is impossible to establish experimentally its identity or permanence. Because of this, the notion that a particle is an identifiable individual and a permanent thing breaks down (or, it is an ambiguous notion, to say the least). The alternative is to consider a particle to be an event.
General Relativity View
Particles, in the view of general relativity, can endure up until they convert to energy. Until then they are identifiable permanent entities because general relativity has not yet been reconciled with the uncertainty principle. Still, particles are events in general relativity, too. This is so because matter is intricately connected with the fabric of space-time (they are continuously affecting each other). So as time is constantly changing, so are, in general, the properties of space and matter. Hence, a point in the continuum of space-time is regarded as an event. And so a particle occupying a space location at an instant of time is treated also as an event. Two events are separated by their space-time interval, which involves a spatial distance and a time interval.
In conclusion, matter, energy, space, and time are all intimately linked, interacting with one another constantly, causing changing events and processes. Nature is the perfect process and therefore is in a state of becoming; nothing ever is. But what causes change in the theory of Heraclitus, and what causes change in modern physics?
Fire and Energy
A permanent primary substance of matter is contradictory to a theory of constant change. The only element of permanence in such a theory is change itself. What really causes change then? For Heraclitus it was the “everlasting fire,”11 and for modern physics the eternal energy. The strife of the opposites or the interactions of matter are fueled by fire and energy, respectively. Matter, the events as has been argued, is the result of the transformations of the fire or of the energy. Fire and energy also represent particular processes. They cause cooling and condensing or heating and rarefying or forming and dissolving. “The transformations of fire [energy] are, first of all sea [liquids]; and half of the sea is earth [solids], half whirlwind [gases].”12 And the transformations of fire, as it is with energy, occur with measure—by obeying conservation laws—since in a metaphor Heraclitus argued, “All things [matter] are an exchange [is a transformation] for fire [of energy] and fire [and energy is a transformation] for all things [of matter], as goods [as one type of matter] for gold [transforms into another type of matter or energy] and gold for goods [back and forth].”13 In another statement he writes, “This world, which is the same for all, none of the gods nor of the humans has created, but it was ever and is and will be, an everlasting fire [energy], flaring up with measure [conservation] and going out with measure [transforming back and forth between its various forms by obeying the law of conservation of energy].”14 Change, which in each respective theory is caused by fire or energy, is guaranteed to always occur since fire and energy are conserved while they are also changeable. From all these qualities fire and energy seem to qualify as the primary substance of the universe in each theory. As argued by Popper, if the world is our home, then for Heraclitus fire is not in the house, “the house [the house] is on fire,” a “somewhat more urgent message.”15 Equivalently, we can argue, the world is energy.
Fascinated by the similarities between the Heraclitean fire and energy, Heisenberg wrote: “Modern physics is in some way extremely near to the doctrines of Heraclitus. If we replace the
word ‘fire’ by the word ‘energy’ we can almost repeat his statements word for word from our modern point of view.”16 And also, “Energy is in fact that which moves; it may be called the primary cause of all change, and energy can be transformed into matter or heat or light. The strife between opposites in the philosophy of Heraclitus can be found in the strife between two different forms of energy.”17
Organization
But while everything is constantly changing, and defining a permanent fundamental particle of matter is impossible, something must endure, at least for some time. For, in all this constant change, still, definable “things” such as rivers exist and so do we, and rivers are distinct from us, and one river (or one person) distinct from another. So both we and the rivers are constantly changing, but simultaneously both we and the rivers are recognizable. “We step and do not step into the same river; we are and are not,”18 said Heraclitus. How can this be?
In a constantly changing nature, which is best regarded in terms of events, each event is different. But collections of events can endure, by creating a certain macroscopic average (an emergent reality), which, for a period of time, is a recognizable “organization”;19 the identifiable plethora that we call things may then be viewed as different organizations.
From the earlier Heraclitean quote, in the part “we step . . . into the same river; we are . . . ,” Heraclitus treats the “we” and “river” as two identifiable organizations, thus as two different and permanent things—at least for some period of time and in some region of space. Whereas in the part “. . . and do not step . . . and are not,” he seems to imply that while the “we” and the “river” appear as permanent things, these are so only on the average. In reality, neither “we” nor the “river” is ever the same.
In Search of a Theory of Everything Page 10
