Where was matter before it burst into the macroscopic material of the universe? Truth be told, physicists still don’t know. But as science creeps along with every century inspiring new revelations, contemporary physics may at last have an answer—a theory of such small proportions (and so many dimensions), that it unravels the Big Bang. Theoretical physicist Michio Kaku offers string theory as an increasingly evident solution to the question of the universe—an answer that may reveal the interior of black holes, the existence of time travel, and even a glimpse of God’s creative mystery.

After spotting a comet soar above him in 1682, Edmond Halley paid a visit to the enigmatic recluse Isaac Newton. As expected, the esteemed scientist already knew exactly how the comet managed to arc across London’s sky. Its elliptical movement and direction fit perfectly within the parameters of his new though still unpublished theory—a little idea he liked to call gravity. Inspired, Halley footed the bill to publish Newton’s book Mathematical Principles of Natural Philosophy, also called his Principia, which contain his cloistered discoveries. Newton’s realization that everything, from the things found on earth to those suspended in space, were propelled by similar “forces” determined by his calculus was revolutionary and set the precedent for later advancements (and disagreements) in the history of science. 

Newton wasn’t the only visionary to conceive of a mathematical language to listen to the pulse of the universe. Compelled by the work of Michael Faraday in the 19th century, mathematician James Clerk Maxwell created vector calculus. Faraday’s prior work, captured in scribbled notebook sketches, pictured the universe as submerged in fields, which Kaku defines as “lines of force spread throughout space.” These fields are both electric and magnetic, and activity in one often produces the actuality of the other. Maxwell extended Faraday’s work on electricity and magnetism to assert an even more novel thought: The constantly flickering fields of the magnetic and the electric are actually one and the same, an electromagnetic wave. And then a lightbulb flashed. Maxwell envisioned the substance of light itself.

Yielding inventions as transformative as the steam engine, the radio, and even the cell phone you hold in your hand, the ideas of Newton and Maxwell ran far beyond expectation. Just as Newton drew inspiration from the work of Johannes Kepler and Maxwell used the findings of Faraday to ignite his own discoveries, these scientists were two shining links in a chain of scientific thought. And yet, many scientists after them believed that scientific inquiry was finished. With a world so full, they envisioned the curtain dropping amid a beautiful, unquestioned finale of discovery. Many even called it the “end of science.” But these inspired searchers had much more work to do before they could hang up their lab coats and call it a day. After all, the origins of the universe were waiting, and so their work was only just beginning.

The first inkling of Einstein’s life work arrived in a book he read as a young child. In his Popular Books on Natural Science (originally published in 1869), Aaron David Bernstein encouraged readers to watch themselves glide along the wire of a telegraph, but this puzzle eventually prompted Einstein to wonder about something else: What might happen if he were to sprint beside a ray of light? Years later, Einstein applied Maxwell’s equations to his quandary and found that nothing could overtake a bounding ray of light. In 1905, Einstein declared, “a storm broke loose in my mind” as he at last began to understand why he would never be able to win in a race against light. And with the flicker of an idea, the 26-year-old office clerk changed everything—the theories that grew from Einstein’s questions, revelations, and even some mistakes lit the darkened tunnel of science for future advancements.

The first idea to come from Einstein’s lifelong musing culminated in the theory of special relativity—his answer to the question concerning the velocity of light. Einstein employed Maxwell’s equations to find that if one were ever to sprint fast enough (or hop aboard a rocket, more likely), time would move much differently. As one draws near to the 299,792 kilometers per second that is the speed of light, time slackens its pace, space appears to compress, and one’s weight increases. Space bends and time loosens to accommodate light’s movement.

It took a near tumble from his chair for Einstein to envision his next theory—one that would act as both a bounty and a blister for the world of quantum physics to come. Einstein’s theory of general relativity invoked the concept of gravity, landing him in trouble with Newton’s seemingly stable universe. Quickly, Einstein realized that the world was not as it seemed. Newton’s conception of gravity was wrong.

When Einstein nearly crashed from his chair, he recognized something crucial. According to Kaku, Einstein saw that “gravity does not pull; space pushes.” Consider an example the author gives to envision how Einstein’s discovery differs from Newtonian gravity. Let’s say you place a large ball in the center of a bed and watch as the mattress beneath it falls inward. Then you toss a marble along the surface of the comforter and witness it move around the ball in response to the way the bed is deformed. This is essentially how gravity works—not as some cosmic “force” as Newton envisioned, but a product of a universe shaped by the objects interwoven in its frame. 

Einstein’s insight shattered science and compelled the curious to look for even more bizarre explanations of the universe. But there was still an issue even this farsighted genius simply couldn’t wrap his head around—one that continues to baffle physicists today. Discontent with the way gravity seemed to be separate from Maxwell’s equations for light, Einstein sought a “unified field theory,” an early predecessor to a theory of everything. But Einstein didn’t realize that things would have to get a whole lot smaller before physicists could even dream of capturing it all. It was time for physics to sink into the subatomic.

Despite Einstein’s questions, the world of physics continued to turn, spiraling right into the 20th century phenomenon we know as quantum mechanics. Over a scientifically dense period of time, physicists encountered new realms of matter that were far less certain and even more fantastic than they could have ever foreseen. One of the forebears of this new field was physicist Max Planck who in 1900 first envisioned that at increasingly minute levels of matter, energy exists in “quanta,” or tiny points that function at something called “Planck’s constant.” Planck’s constant is the tiniest unit of material energy, and it compels the movement of subatomic particles (rather than our macroscopic reality), a world filled with what physicists call “quantum corrections.” The quantum captured physicists from all corners, and as reality of the small and the large grew more nebulous, the trek toward everything stretched into greater focus.

The insights of the 20th century were abundant, but one of the period’s greatest scientific triumphs (and eventual shortcomings) was the creation of the Standard Model. The Standard Model takes physicists back to the first explosive glimmers of the Big Bang, detailing the way the four forces of the universe worked together before falling out of symmetry. These forces consist of gravity, electromagnetism, the weak nuclear force, and the strong nuclear force. But despite new insights into realms of the subatomic, Einstein’s search for a unified field theory still remains. Reducing the world of gravity to the subatomic equivalent, the graviton, has been consistently perilous.

Many physicists find this attempt at a theory of everything far too clunky to describe the beauty of the universe. Despite probing the tiniest depths of the atom to the realm of quarks, there’s still something missing. Physicists thought they had an answer in 2012 when the 17 mile-long Large Hadron Collider (LHC) in Geneva, Switzerland discovered the Higgs boson. This supposed “God particle” turned out to be just another fundamental component of the Standard Model, leaving physicists in the lurch. Today, the mystery remains as gravity defies physicists’ attempts to insert its grandeur into the minute calculations of the subatomic. The claims of string theory, on the other hand, may at last yield the equation physicists have been seeking.

Quantum physics is surely bizarre, but the claims of string theory are even weirder than Schrödinger’s elusive cat. First studied in 1968 when a handful of physicists found a startling equation from an 18th century mathematician, string theory is contemporary physicists’ closest answer to a theory of everything. Its equations posit a universe of wriggling strings that give birth to the various particles of quantum physics such as quarks, neutrinos, and photons. But that’s not all the numbers have to tell us—string theory also resolves one of the greatest dilemmas in the history of science. String theory’s equations predict the existence of gravity with a particle called a graviton. That claim makes it the most likely theory of quantum gravity and a possible answer to Einstein’s quest for a unified field theory. Though physicists have yet to prove this strange theorem, its equations continue to arrive, granting the world a glimpse of what could be everything.

One of the most crucial components of string theory is supersymmetry, first found by physicists Bunji Sakita and Jean-Loup Gervais. In previous theories, when physicists tried to add gravity into their quantum equations, doing so yielded strings of errors. Gravity simply would not fit within their quantum corrections, which spit out “divergent” or infinite answers when gravitons smashed into each other. In the equations of string theory, on the other hand, strings that bump into each other produce two types of particles called fermions and bosons. When physicists peer at the mathematics of this supersymmetric situation, they see that the resulting fermion and boson are equal opposites. Together they bypass the problem of an infinite answer and provide physicists with a viable equation.

In 1995, the physicist Edward Witten threw yet another dimension into the original 10 of string theory, providing it with the 11 that physicists calculate today. Witten’s M-theory posited the existence of another dimension composed of membranes that fold down into the many dimensions of strings. This bizarre addition resolves an issue within string theory that proposes five mathematical outcomes. The membrane of M-theory helpfully manifests each of these five outcomes as it becomes reduced to strings. Put simply, M-theory consists of the totality of string theory. Though its assertions are highly contentious and unproven by experimental evidence, physicists continue to probe its multi-dimensional world for a single theory of everything.

One way contemporary physicists seek proof for string theory is through the search for dark matter, an element that makes up 26.8% of all matter in the universe and yet has never been witnessed. Using Newton’s equations, physicists found that the visible matter in the universe isn’t adequate for entire galaxies to remain in place; there must be something else. Dark matter keeps galaxies firm and prevents them from spiraling away from each other; it may also consist of particles that help justify the claims of string theory. Now, leagues of physicists are steeped in underground labs, searching for a substance that may reveal a glimpse of string theory’s multidimensional secrets—an enigma that might decode various other wonders, from black holes to the Big Bang.

Blockbuster hits have capitalized on the most mysterious, mind-boggling conundrums thrown about in pseudo-scientific lingo—but these seemingly fantastic fragments of physicists’ imaginations aren’t entirely fictional. And the quest for a theory of quantum gravity, (for which string theory is a strong contender) may simultaneously unwind questions about black holes, time travel, and most importantly, the beginning of the universe.

The iconic genius Stephen Hawking is most notable for his work delving into the inky depths of black holes. These cosmic craters consist of two kinds, one of which is born from the death of a giant star in a process called a supernova, and the other of which is found at the core of galaxies. What confused Hawking was how a black hole, believed to consume everything that passed through the threshold of its event horizon, could contradict the laws of quantum physics; in the subatomic realm, nothing is truly definite. Eventually, Hawking posited the existence of “Hawking radiation,” a kind of radiation that keeps particles partly intact even after they’ve succumbed to the grasp of a black hole, remedying the inconsistency between black holes and particle physics.

Hawking’s speculations didn’t end at the event horizon of a black hole, though. Petitioning other scientists to puzzle over the possibilities of time travel, he issued the search for something he termed “the chronology protection conjecture.” Hawking called for others to search for concrete evidence against the existence of time travel, showing that the laws of physics were inconsistent with its claims. Unfortunately (or fortunately for those aspiring time travelers), Hawking’s rally against time travel ended in silence. So if you’re still dreaming of building your very own DeLorean or traveling to some beloved bygone age, you may still have a shot.

If you want to journey back to the first sparks of the early universe, though, you may not even need a time machine. In the 1970s, physicists Alan Guth and Andrei Linde used quantum principles to predict what must have occurred at the Big Bang. With the findings of the Standard Model, the physicists contrived the theory of “inflation,” in which the universe itself functioned like a subatomic particle. Guth and Linde’s inflation theory argues that the universe underwent a period of enormous growth in which various universes, including our own, broke into view, like particles glimmering in and out of sight. Hawking’s notion of “space-time foam” parallels this theory, claiming that the universe is a simple “quantum fluctuation,” or a tiny point in a larger cosmic backdrop.

What sets our universe apart from the many possible points in spacetime is that it simply continued to grow. Like an ever-stretching balloon, it became large enough to accommodate life itself. These revelations in quantum physics, gravity, and the search for a theory of everything expand the understanding of scientists and lead the wider culture to ponder the nature of creation—a question that goes even deeper than the breadth of cosmic space.

Will science ever prove or deny the being of God? In the poignant words of Einstein himself, “did God have a choice in creating the universe?” These questions, traversing fields even more abstract than theoretical physics, percolate beneath every mathematical equation and physics theorem, waiting for a day when they may perhaps receive an answer. Years before the word “quantum” even entered scientific thought, the 13th century theologian Saint Thomas Aquinas devised a series of proofs. One of these is called the “cosmological proof,” and it argues for the existence of God on the basis that the universe requires a “First Mover,” or a “First Cause.” Despite centuries of developments in science and quantum physics, Aquinas’s cosmological proof still stands; the propellant of the Big Bang is still (and perhaps forever) unknown. The question of God cannot be solved with an equation.

Even though a theory of everything may never answer the question of a divine Creator, it still brings greater understanding to a universe of startling depth and delicacy. As physicists continue to whittle down their equations into a form that encapsulates the forces of gravity, electromagnetism, the weak nuclear force, and the strong nuclear force, they may eventually arrive closer to an explanation that works. According to Kaku, a theory of everything, a final response to Einstein’s call for a unified field theory, will account for the growth of our universe from a swarm of quantum fluctuations, making life a necessary product of a mathematical equation.

String theory may explain our universe with a handful of multidimensional strings, or it may not. Only time, experimentation, and mathematical equations will tell. But like flickering subatomic particles, possible components to a theory of everything crop up every day. The history of science itself is the tale of this burgeoning question. In physicists’ journey toward an answer to the question of the universe, science is not simply a stretching toward discovery, but a reaching toward recovery—a return to the beginning of everything.

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