Book SummaryThe God Equation, by Michio Kaku

1-Page Summary1-Page Book Summary of The God Equation

The science of physics is a fractured field. It studies the universe on the largest and smallest scales imaginable, from the beginning of time to the far distant future. Physics explores the underlying forces of nature, from the gravity that holds stars and planets together, to the electromagnetic attraction that drives chemistry and powers civilization, down to the microscopic forces that hold atoms together and break them apart.

Each of these aspects of nature functions by its own mathematical rules, some of which contradict each other, suggesting that our theories are incomplete and maybe flat-out wrong. For centuries, scientists have sought a resolution, which some call “the God equation”—a single theory that would unify physics, cancel out its contradictions, and provide one simple, underlying equation from which we can derive a complete understanding of the universe.

In The God Equation, published in 2021, theoretical physicist Michio Kaku suggests that an approach called...

The God Equation Summary First Steps Toward Unification

Since the birth of classical physics, the greatest advancements in knowledge have come from bringing together different fields of study. In short, a theory is considered more powerful if it explains multiple phenomena at once. Kaku shows how even the early steps in physics united what were thought at the time to be wildly different areas of study, such as the motion of objects on the Earth and in the sky, as well as an unexpected unity between electricity, magnetism, and light. These examples show that a persuasive theory doesn’t just explain the subject being studied, but also reveals insights seemingly unrelated to the topic at hand. One such insight we’ll cover in this section is that the laws of nature are symmetrical, a concept that Kaku repeatedly invokes.

It all goes back to Isaac Newton, who from 1666-1687 worked out the first mathematical theory to explain the laws governing the motion of objects, as well as the “law of universal gravitation” that explained both how objects fall to Earth and how the planets orbit around the sun. Kaku says this was a breakthrough moment in science because Newton had shown through...

The God Equation Summary Einstein’s Relativity

Thanks to Newton’s and Maxwell’s equations, physicists at the start of the 20th century believed there wasn’t much left to explore. But Kaku points out that there was a problem—under certain conditions, Newton’s and Maxwell’s theories were incompatible with each other. After explaining the nature of the problem, we’ll discuss how Albert Einstein solved it by reimagining Newton’s laws of motion and then rewriting Newton’s law of gravitation.

The contradictions between Newton’s and Maxwell’s laws appear when you consider objects moving near the speed of light. Suppose a cat is chasing a laser pointer at 600 million miles per hour. The beam of light from the laser pointer passes the cat at 671 million miles per hour. How fast would the beam of light appear from the cat’s point of view? Newton says that speeds add and subtract—the cat would see the laser beam moving at only 71 million miles per hour. However, Maxwell’s equations suggest that the speed of light never changes. No matter how fast the cat is chasing the pointer, it will always perceive the ray of light to be moving at 671 million miles per...

The God Equation Summary Quantum Mechanics

While Einstein was solving the riddles of gravity and motion, another field of exploration—quantum mechanics—was opening up. Scientists studying the building blocks of matter discovered that on the level of the atom, the laws of nature follow a strange set of rules known as quantum mechanics. In this section, we’ll trace the road to quantum mechanics from attempts to explain how objects radiate heat, to the discovery that some subatomic particles also behave like waves instead of matter, and finally to a unification between the new quantum theory and Maxwell’s light equations.

In the early 1900s, our model of the atom was like a miniature solar system with a tiny, dense nucleus of protons and neutrons surrounded by orbiting electrons. However, theoretical physicist Max Planck noticed something strange about atomic behavior when he investigated the light given off by hot materials. According to equations based on Newton’s laws of motion, the atoms in hot materials vibrate faster than those at cooler temperatures, and they release their excess energy in the form of light. However, the math didn’t add up—the...

The God Equation Summary The Standard Model

Though scientists have yet to figure out the unifying theory—Kaku’s “God Equation”—physicists have made a great deal of progress using an intermediate step toward that theory referred to as the Standard Model. In this section, we’ll go over the basis of the Standard Model as well as its theoretical problems, including cumbersome mathematics, a mismatch between the theory and the observable universe, and its current inability to account for the force of gravity.

Beginning in the 1970s, physicists stitched together the equations for the strong nuclear force, the weak nuclear force, and electromagnetism to produce what’s now called the Standard Model. This mathematical expression of those fundamental forces presumes that in the extreme conditions that existed moments after the Big Bang, all of the forces acted as one and only diverged as the universe cooled.

(Shortform note: In Astrophysics for People in a Hurry, Neil deGrasse Tyson goes into more detail about the universe’s first moments and their importance to a unified theory of physics. Tyson explains that [at the instant of the...

The God Equation Summary The Promise of String Theory

Though physicists have yet to reconcile relativity, gravity, and quantum mechanics, Kaku argues we may already know what form the eventual solution will take. The answer comes from the field of string theory, which Kaku himself has been working to advance for all of his professional career. In this section, we’ll explain what string theory is, how it suggests higher orders of symmetry in the universe, and why it appears that the universe we see is merely a projection of something much greater.

The basic assertion of string theory is that all particles can be described as vibrations on subatomic strings that constitute the basis of energy and matter. Kaku writes that each different type of particle is produced by a different vibration. One of string theory’s strong appeals is that its equations produce gravitons as being the lowest string vibration, removing the conflict between Einstein and quantum mechanics. String theory also supports physicists’ long-held belief that in the beginning, there was one unifying force in the cosmos by showing that the particles transmitting those forces are symmetrically interchangeable since they’re all just different frequencies of the same...

Shortform Exercise: Reflect on the Path of Scientific Progress

Kaku relates the history of physics by explaining the natural world while at the same time trying to bring scientific theories under one unifying banner. While working toward a unified and preferably simple theory of everything, scientists have produced theories that are increasingly complex and difficult for the layman to grasp. Think back on the theories presented in this guide and how well you grasp their underlying concepts.

The implications of Einstein’s relativity—that time and space can stretch and bend—have been verified by experiments for over 100 years. When such seemingly implausible theories are confirmed by experiments, does it make it easier for you to accept it as fact, even if you don’t understand the math behind it? Why or why not?