The Key to Physical Attraction…It’s Called “Gravity” (and “Love”)

As unlikely as it may seem, the language of science has expressions in common with the language of love. The notion of  “physical attraction”  has roots in both. We humans are selectively attracted to others during our lifetimes, yet we are constantly attracted, in reality, to everyone and every thing in the universe as revealed by Isaac Newton in his masterwork of science, the Principia. Two marbles, one inch apart on a smooth table, exert an attractive force on one another which would tend to draw them together, except that the force is too small to overcome the rolling friction on the table. Yet, on the larger scale of the sun and planets, the forces of attraction between such massive bodies are immense.

Newton & Apple_1

 “Falling” in love may happen but rarely in our personal lives, yet we are, in fact, constantly falling – even though we are not conscious of the reality. All earth-bound denizens fall constantly… toward the sun as the earth orbits our nearest star. That motion, due to gravity, of continually “falling toward the sun” works in concert with a component of planetary motion tangential to the orbit to define the path of our earth around the sun. That tangential component of motion represents the inertial path the earth would take if the gravitational attraction to the sun suddenly ceased. The concept of  “gravity” has historically been one of mankind’s greatest comprehension challenges – one of nature’s great mysteries.

 Earth Orbit_1

Early man’s curiosity as to why things apparently fall toward the center of the earth was at least temporarily assuaged (for hundreds of years) by Aristotle’s assertion some two thousand years ago that the earth’s center was the “natural center of the universe,” hence the logical place for objects to congregate (prior to Copernicus in 1543, the sun and planets were assumed to revolve around the earth). The great mathematician/scientist, Johannes Kepler, in the early seventeenth century was an early disciple of Copernicus’s sun-centered solar system and one of the first to seriously contemplate what kind of natural, physical mechanism was at play to keep the planets moving around the sun as they do. He conjectured that perhaps some form of solar, “magnetic” winds or vortices swept the planets along in their almost-circular paths. It was generally believed, prior to Newton, that whatever phenomena, or “force,” that caused apples to fall to earth was distinct and different from the celestial forces that held the heavens together. For a long time, celestial motions beyond the moon were even attributed to divine influence and motivation.

It took the genius of Isaac Newton to declare, in his 1687 milestone book on science and mathematics, that earthly gravity and heavenly forces are one and the same – hence, universal. Indeed, Newton claimed that all objects of mass in the universe attract all other objects to greater or lesser degrees via the force of universal gravitation. He stated that the nature of gravity and the equation which describes how it works is applicable everywhere and at all times – a truly “universal” law of nature! Although Newton explained the scientific version of “physical attraction,” he wisely made no attempt to explain the underpinnings of the version expressed in the language of love. Nor will we! That remains as captivating and mysterious as ever and seemingly beyond the ability of science and mathematics to explain.

But Newton really did not explain what gravity is or why it acts the way it does; he admitted so in the 1713 second edition of the Principia stating: “Non fingo hypotheses,” which, translated from Latin declares, “I feign no hypotheses!” He was criticized by his peers for his advocacy of this mysterious force-at-a-distance; they asked, “How can a body like the sun transmit, through empty space, the tremendous forces necessary to steer the planets?” His contemporary critics should have called to mind that other mysterious force which travels through space – magnetism, in the form of the magnetic field – which also has the power to attract objects. Newton was sage enough and courageous enough to stick by his contentions even though he could not explain them all. Although his famous equation does not hint at why gravity works the way it does, it describes precisely how it works – well enough to be used by NASA for its precise orbital computer computations. Despite the tremendous success of his theory of gravity and his numerical analysis of it, Newton did not – could not at that time – grasp the true essence of gravity. This is a remarkable situation which aptly reflects the reality that science will continue to inexorably peel-back, layer by layer, the deepest mysteries of our existence. Sometimes, genius like Newton’s transcends the state-of-the-art and “the possible”…for a while.

 Albert Einstein Peels Back Another “Layer” of Gravity

It took Albert Einstein’s 1916 general theory of relativity to go Newton “one better” and unmask the true face of gravity. Planets including the earth go around the sun in almost-perfect circles (ellipses) and not off into distant space not due to an explicit force of attraction between themselves and the sun as Newton proposed; Einstein showed that they are merely following a “natural path” determined by the curvature of four-dimensional space-time around the sun. That curvature is caused by the presence of the sun’s mass. All bodies of mass curve space-time in their vicinity. Einstein advanced physics immeasurably by contributing this radically unique physical interpretation of all gravitational effects. The complexity of Einstein’s mathematics in the general theory of relativity required to demonstrate this conclusively dwarfs Newton’s simple equation for an attractive force as presented in the first illustration of this post. Nonetheless, Newton’s achievement regarding gravity remains one of the greatest milestones in the history of science.

The Makers of  Universes!

George Bernard Shaw’s famous toast to Albert Einstein who was sitting near him at a tribute dinner held in 1930 at the Savoy Hotel in London, is well-known and oft-referred to. After extolling the virtues of mathematicians and scientists who, through the ages, have built “universes” instead of merely fractious empires like Napoleon and others, Shaw concluded by saying, “Ptolemy [the early astronomer/philosopher] made a universe which lasted 1400 years; Euclid [the great mathematician and founder of modern geometry] also made a universe which has lasted for 300 years; Einstein has made a universe, and I can’t tell you how long that will last!” Einstein is shown in the grainy black and white film footage clearly letting-go a big belly-laugh. Science does move relentlessly forward – always with a great assist from mathematics. Look at where we are today. Love and science do go together: To love studying the history of science and its impact on humanity is to experience what I call the “joy of science.”

Despite the phenomenal track record science has compiled while continually advancing the state of our knowledge and well-being, the greatest of all mysteries may prove to be beyond the comprehension of science: Who is the ultimate maker of universes and what can we truly know about that?

One of Einstein’s famous quotations says it beautifully: “The most beautiful emotion we can experience is the mysterious. It is the fundamental emotion that stands at the cradle of all true art and science. He to whom this emotion is a stranger, who can no longer stand rapt in awe, is as good as dead, a snuffed-out candle. To sense that behind anything that can be experienced there is something that our minds cannot grasp, whose beauty and sublimity reaches us only indirectly: this is religiousness. In this sense, and in this sense only, I am a devoutly religious man.”