September 2011 Philadelphia Chapter of Pax Christi U.S.A.

Changing Paradigms: The Nature of Gravity

“Seeing is believing,” we say. What can be more obvious? Yet, what seems obvious is not always true. For one thing, we see with our brains more than with our eyes. The rays of light reflected from the observed object are focused by the lens of the eye and strike individual rods and cones on the retina. This information is transmitted to the brain through the optic nerve as a series of discrete electric impulses. It is the brain that assembles these impulses into two images, one from each eye, inverts them, and combines them into a single image.

Now begins the work of interpretation. “What is the reality which corresponds to this image? Is it solid or just a flat picture? How far away is it? How do I name it? Is it like anything else I remember seeing? How does it fit in with my understanding of the nature of reality?”

It is widely believed that we moderns get closer to the truth by using the “scientific method.” As usually described, the method has three steps: formulation of a hypothesis, carrying out an experiment to test the hypothesis, and concluding that the hypothesis is correct or needs to be modified or abandoned. While most scientific research is done in this way, the breakthroughs in science usually come from a leap beyond current beliefs, a way of thinking “outside the box.”

Logical adherence to the scientific method would seem to require the old to be abandoned once experimental evidence supports the new. In reality, the transition is slower and more complicated. At first the old is patched up with ad hoc modifications. Then as patches are put on patches, the old finally collapses and is replaced by the new.

In The Structure of Scientific Revolution (1962) Thomas Kuhn introduced the notion of a paradigm, a coherent and consistent set of beliefs and assumptions within which experiments are done and the results interpreted. A major theme of his book is that theories are not abandoned when conflicting empirical data emerges. To the contrary, acceptance of a new theory must await the changing of the current paradigm, and that can be a slow process.

An example of changing paradigms can be found by tracing the development of our understanding of why solid objects fall to earth. Why does the apple fall from the tree to the ground?

Pre-Newtonian explanations go back to the Greek philosophers of the fourth century BCE and persist into medieval times. All matter was thought to be composed of four elements: earth, water, air, and fire. The natural state of any physical body was said to be at rest, each element in its own preferred location. Earth finds rest down on the ground and water just above it. Air finds rest up toward the heavens and fire above it. Motion occurs when the elements are displaced from their preferred locations, when they are in an “unnatural” position.

The apple is mostly earth. When hanging from the tree it finds itself above air. Given the opportunity, it will fall to the ground, its preferred location. When it rains, the puddle forms on the ground, but above the earth and below air. Bubbles of air, naturally, rise above the water. Fire rises to the heavens, its natural location. The underlying concept is that anything marked by imperfection (in this case, a body not in its appropriate place) moves to get closer to a state of perfection. Inherent is the notion of a Prime Mover (God), already perfect and therefore unmovable.

The age of classical physics was ushered in by Galileo. His demonstration of the phases of Venus, the moons of Jupiter, the effect of “earthshine” on the moon, among others, was consistent only with a heliocentric model of the solar

system. The evidence was unambiguous, but the geocentric paradigm was slow to change. Condemned by the Inquisition to house arrest, he abandoned work on the forbidden topic of the nature of the heavens and concentrated on earthly phenomena. His studies on the pendulum and extensions into the motion of moving bodies led him to conclude that the normal state of a body is not rest, as the ancient philosophers taught, but straight-line movement.

With this work as a foundation, Newton formulated the three laws of motion which served as the accepted view until the twentieth century. Newton introduced the notion of gravity as a force which attracts all objects proportional to their masses and inversely to their separation. As useful as Newton’s laws were to become, up to the present day, there was a philosophical flaw: the problem of “action at a distance.” It was well understood that when a moving object collides with a stationary one, for example, it will induce movement and even acceleration. But gravity acts without the objects being in contact. How can that be? Newton satisfied himself that there were supernatural aspects to gravity and that the Creator supplies whatever is needed to make the laws work. Physicists subsequently have introduced the notion of gravitational fields, so it is the fields that overlap and interact. But exactly what is a field, beyond a basis for calculation? The problem of action at a distance persists.

Modern understanding of gravity came with Einstein’s theory of general relativity. Einstein argued in a series of “thought experiments” that a person in an accelerating rocket ship in intergalactic space would find herself pushed against the floor, just as she would by gravity. If she dropped a ball, it would drop to the floor and then bounce up, again just as it would under the influence of gravity. Since the two circumstances, accelerating through space and standing on earth, could not be distinguished, they can be considered to be identical. From this kind of reasoning, Einstein did away with the notion of gravity entirely, replacing it with the curvature of the space-time continuum. Massive objects curve space, he argued, and other bodies have their paths of motion disturbed as they pass near the massive object, not because of a force of attraction, but by falling into the curvature. Thus, the problem of action at a distance disappears, as does the concept of gravity itself. Ridiculous? Absurd? Much empirical evidence confirms general relativity. Can nature be playing such tricks on us? No, it’s just a matter of adjusting to the new paradigm.

What does all this have to do with us in the present day? Only that we are in the middle of a significant paradigm shift. We are moving from a technological, industrial age to an ecological one. From a static universe to a dynamic one. From an ego-centered consciousness to a universal consciousness. The new paradigm will stress peaceful cooperation rather than aggressive competition. It seems too good to be true. But it’s already here in small but growing pockets. We only need to switch to the new paradigm. Once we get there, we will love it.

Dom Roberti

Dom Roberti, PhD, is a member of CPF