The book begins by exploring ancient history regarding gravity, and the author discusses how religious views and belief in gods were shaped by the existence of gravity and its prevalence on all living beings and all matter, and old beliefs and to what lies 'above'.
Cosmologists say without gravity there would be no Earth, and that space came into existence in the Big Bang, all balled up, and that the ‘unballing-up’ we measure by what we call time. Gravity tethers the Moon to Earth, other moons to other planets, moons and planets to the Sun, the Sun to stars, stars to stars, galaxies to galaxies so is gravity a force in itself, or rather should we be asking what causes gravity? Panek asks these and many other questions, but readily admits “ I still won’t know what gravity is” by the end of the book.
He repeated the question to Kip S. Thorne, who is a theoretical physicist. “That is a meaningless question” he replied, but the author endeavors to discover what the meaningless question means through myths, facts, and fiction.
Panek relates Aristotle in the mid-fourth century BCE found himself confronting two realms, the knowable and the unknowable, the terrestrial and celestial and the mundane and the mysterious. He knew that the world was not flat by observing the singular phenomenon in which the Sun casts a shadow of the Earth on the Moon. The shape of that shadow is unmistakably a circle. He also wrote “conceived of all upper bodies as earthy and endowed with weight”, he had introduced into the conversation methodology, not mythology and he started with sense evidence and then applied logic. It is startling for Aristotle to be putting forward these theories, this is the period when humans believed the earth was flat.
Panek continues with the Polish cleric Copernicus in 1543 who published his Sun-centered system of the universe, and in 1572 Tyco Brahe first used the telescope to make extensive astronomical observations. He determined that the planets orbit the Sun in elliptical orbits. He proposed some simple laws that govern the motion of the planets and other objects. Panek continues with his history lesson introducing Kepler, Galileo, and Isaac Newton and their observations.
In the third chapter Panek finally starts to talk about gravity itself. Newton writes “the matter causing gravity must pass through all pores of the body, because if the cause of downward motion acts on an object, it must act everywhere on the object equally, it must infiltrate the body of matter, cause its effect, then move on.” The ancients knew that planets do not go about their business at a uniform rate, they speed up and slow down, Newton wrote that Kepler “knew that Mars orbit to be not circular but oval”
Everything in the Universe is in a constant state of falling toward everything else, no matter the distance. Or if you prefer, states Panek, rising toward everything else. Newton was no closer to identifying whatever was counteracting the straightforward inertial motions throughout the universe, foreordained orbits, and kept people from flying off planets.
The word ‘gravity’ had been around in variations for thousands of years and was a synonym for weight, as it had been for the ancients, “the act of falling or how fast an object falls” but Newton created the word ‘gravitation’,. Both terms sound alike but there is a difference between gravitation and gravity, gravitation is the force occurring between two bodies whereas gravity is the force occurring between the earth and a body. Newton knew he was asking a lot from his readers to believe in something they couldn’t see, taste, touch, feel or hear and to be the cause of the workings of the universe and it required more than a leap of faith but a leap of fiction.
Newton then set out to simplify what makes no sense, You don’t provide a cause for the effects of gravity, at least according to the current understanding of the workings of the universe. So rather than flail and conjecture and guess and strain to describe it, let's just take what we do know, the match between math and motions. In other words, we do not need to know how gravity works, but we know that it does work because we can see its effects, we can derive its maths, we can arrive at laws that we can generalize across the universe “It is enough” he wrote, “that gravity exists and acts according to laws we set forth”.
The author relates that Ernst Mach was a voice of reason arguing for greater rigor in the methodology of science he wrote “the theory of gravitation had disguised its philosophical shortcomings by proving its reliability and usefulness, but the philosophical shortcoming hadn’t gone anywhere, they’d just gotten respectable and has become common unintelligibility”.
In 2016 on February 11th, Panek received news of the actual detection of gravitational waves from the Laser Interferometer Gravitational-Wave Observatory LIGO.
The current understanding of the universe is not a creation myth, meaning a collection of fantasies to help explain what this place is, and what our place is within it. Instead, it's an origin story, a collection of facts that our minds have shaped into a narrative. Understanding from the beginning of this book, the author admitted we do not know what gravity is, but he has managed to give us many interesting insights, facts, and reference material throughout the book. I now realize how much a genius Aristotle and Newton were although I have written reviews of them both, I recommend this book to academics and laymen alike as I am sure they will enjoy the read.
- Gerrard Russell.