Why are we here? What is reality? Why is there something instead of nothing? Stephen Hawking and Leonard Mlodinow team up to champion science as humanity’s best hope for answering questions about our existence and the existence of our universe.

Philosophy is dead. It’s failed to keep pace with science and its amazing, rapid development—particularly in the field of physics. We must look to science for answers to our biggest questions about life and the universe. Science alone can tell us why there is something rather than nothing, why we are here, and whether the universe needs a creator. It will increasingly be the torch that leads us out of the cave of ignorance. It is important to understand the how, but it is even more critical to know the why. The curious human species has always grappled with these questions, and thankfully science is becoming increasingly capable of providing the answers.

Gravity was the first force articulated in a mathematical formula. Sir Isaac Newton published a paper on the subject in 1687. Newton maintained that all objects in the universe will attract each other in accordance with the mass of the objects. The formula he used to model this made waves in his day because people realized that at least one force in the universe can be understood mathematically. This raised questions of whether other formulas could be expressed mathematically as well.

Maxwell’s theory of electromagnetism is another landmark discovery, and perhaps the most significant for the human race from a commercial perspective. Maxwell’s equations have allowed us to use electromagnetism for all kinds of common household appliances and computers. What is more, they’ve enabled us to understand the diverse spectrum of wavelength frequencies, from radio and microwaves to gamma waves.

Einstein’s theory of relativity was another important contribution to the discussion of physical forces. He showed that Newton’s assumption that objects move along a straight path is mistaken, that objects move not in straight lines but on geodesics—that is, along curved lines. An example of this principle at work is flight trajectories. Looking at a 2D world map, the routes that planes take look circuitous, when, in fact, the curved trajectory is the shortest distance.

Newton, Einstein, and Maxwell each developed models that comprise a corpus of classical theories. Each was an attempt to develop a unified theory of everything. Unfortunately, these models do not explain phenomena at an atomic and subatomic level. To better grasp these phenomena, scientists have had to turn to quantum theories. We need quantum theories of gravity, electromagnetism, and relativity. While vital to our understanding of the universe, the classical models only get us so far. Quantum field theories will take us farther. String theory was an attempt to develop a unique theory of everything, but there are a variety of string theories, and they are incompatible with each other. Advocates still hold that these different “strands,” if you will, of string theory are all circling in on one underlying super theory, with each of these strands applicable to differing scenarios.

This underlying theory is referred to as M-theory. What does the ‘M’ stand for? No one seems to know. M-theory is a collection of theories, which, taken together, could bring us a theory of everything. It’s probably the closest we will come to realizing the physicist’s hope of a single, unified theory of everything. We’d like to ascertain the exact nature of M-theory, but it might not be possible.  

Different people groups from civilizations around the globe and across time have constructed a variety of creation narratives. These stories try to make sense of why there’s a universe and why this particular universe and not another.

Within the last century, we have made remarkable strides toward answering these questions. Recent discoveries and theories like the multiverse, M-theory, and alternative histories equip scientists to posit promising explanations.

Perhaps one of the most significant discoveries of the past century is that the universe is not static, but dynamically expanding. In 1920, Edwin Hubble became the first to notice this in an observatory in Pasadena. Based on the spectrum of light that galaxies were emitting, Hubble realized that galaxies were moving away from each other, and those farthest away were moving at the fastest rates.

This was the first clue that the universe began to exist. Trace the expansion back as far as you can and you will reach a point of unfathomably dense energy, from which propelled the emanation of what became space and time. This expansion would not affect the size of objects themselves, but just the space between them.

The idea of an initial ‘big bang’ was novel for Einstein and his contemporaries. But it was not without its detractors, as it would have meant reevaluating some basic assumptions about the universe. Even the astrophysicist who coined the term ‘big bang’ in 1949, Fred Hoyle, intended it to be pejorative. It’s since become common parlance, used matter-of-factly rather than dismissively.

Further confirmation of the big bang came in 1965 with discovery of CMBR, or cosmic microwave background radiation. This radiation is residual from the very early universe. That being said, it would be misguided to conceive of the big bang as a literal explosion from a particular point of origin. We can use general relativity to make observations about a young universe, and how it unfurled over space-time, but it cannot tell us exactly how the universe began. Quantum theory is more helpful for understanding what was going on at the very beginning because it applies when our scope is atomic and subatomic. Go back to when the universe was a billion-trillion-trillionth of a centimeter, and quantum mechanics is helpful, whereas Einstein’s relativity breaks down.

Clarification on the word "beginning" is also important. Aristotle and other philosophers have side-stepped the question of creation by assuming the universe is eternal. Others have attributed the universe’s beginning to a creator God. The particular unfurling of the early universe involved four dimensions of space and none of time. This makes talking about the “beginning” a tricky business, as time itself didn’t exist. This leads us to conclude that the early universe was brought about by the laws of science—not by some creator. 

Universes in which life is possible are extremely rare, arguably miraculous. Our solar system, more specifically, contains numerous attributes conducive to complex life forms. Consider earth’s path around the sun. Kepler had hoped that planets in our solar system orbit in perfect circles, but went on to discover that they actually revolve on ellipses or slightly “squashed” circles.  If the shape of the ellipse on which earth orbited were too squashed, earth would come catastrophically close to the sun. Another serendipitous factor is earth’s distance from the sun. If the earth were a bit closer or further to the sun, life wouldn’t be possible. The size of the sun also makes a difference. If the sun were slightly larger, earth would get hotter than Venus; a little smaller, earth would freeze over and be colder than Mars. In either case, earth would be utterly uninhabitable. Earth fits squarely into what scientists call the “Goldilocks’ Zone”: the narrow range of conditions in which a place is inhabitable, where it’s not too hot, not too cold, but “just right.” 

As with the discovery of the universe’s beginning, many are tempted to attribute the apparent fine-tuning of the universe to a creator who has intentionally designed it to be so. Before we conclude that we are a special species, it is important to keep in mind not just the chance, but the likelihood of planets within other galaxies supporting life. Add in the real possibility of the multiverse and we see that it is not only conceivable, but very likely that we are far from the special planet at the center of the universe as we would like to think. This detracts from the idea that a God has intentionally created earth to be a singular planet on which life emerges.

Do these creatures have free will? If we came across an alien, we might wonder if it’s a complex robot or a complex creature with a mind of its own. In the case of a robot, it doesn’t have free will because we can predict its actions. With complex beings, however, we are forced to concede free will because it is a helpful model. Our predictive abilities are limited when dealing with staggering complexity. We have a hard time predicting the interplay between three particles, and human beings are comprised of trillions of particles, making behavioral predictions all but impossible. Free will is a useful fiction we must maintain until we can develop equations complex enough to accurately predict behavior. But this is admittedly a monumental and perhaps impossible hurdle.

Physical laws describe how the universe operates, but they cannot tell us the why behind the existence of something rather than nothing, or why humans are part of that something rather than nothing. Here again, God the creator is the easy escape clause, but this creates (pun intended) a problem of infinite regress: if God created the universe, then who created God? And then what created that Being that created God? We are now able to answer questions within a scientific framework instead of resorting to a mystical explanation that raises more questions than it answers.

We now know that the universe spontaneously gave birth to itself. It is because of this spontaneous self-creation that we have something instead of nothing. This is the explanation for the existence of our universe; it is why we’re here. We now know that the laws of nature, specifically the law of gravity, gave rise to the universe’s spontaneous emergence. The universe’s energy must stay at a net zero. As energy is required to form matter, it would seem inconceivable that anything—let alone an entire universe—would emerge from nothing. Gravitational energy, however, is negative, which would balance out the positive energy needed to create matter. Thus, we have the possibility of a universe coming from nothing, a possibility that has clearly been actualized.