Few theories are safe if Big Bang proponents cannot explain why the early universe looks nothing like they claimed. Dark Energy is no longer necessary. Light no longer moves at a constant speed. Einstein’s great theories are incomplete. Black holes might not exist. Time itself is fundamentally different than we believed, and this might be just the beginning of a radical upheaval that will take decades to resolve.
The Big Bang is more than just a theory. Its truth or falsity is more than a purely academic question about the nature and origin of the universe. Key aspects and several conclusions have long been taken as fact independent of any theoretical discussion of the particular mechanisms involved. At a high level, this includes the belief that the universe and all the time and space contained within has a definite beginning and therefore an end. Implicit in this assumption is the idea that the universe itself evolves, that it changes over the course of billions of years, expanding outward from a singular beginning point. Reality itself was far different in the distant past. It will be different in the distant future. These “facts” have been arrived at using a combination of observation of the universe around us, however flawed in retrospect, and assumptions regarding which aspects of theories outside the Big Bang proper should also be considered strictly true. The result is a worldview and a philosophy that both contains much of modern science and reinforces the underlying assumptions at the same time. The assumptions used stem from other theories, but when applied to the Big Bang, they become more than mere assumptions. They are transformed into definitive truths. It is difficult to identify another theory that occupies the same exalted position. For example, Einstein’s great General Theory of Relativity is widely regarded as a landmark work of human genius that radically changed our view of the world, ultimately allowing the Big Bang to become ascendant though Einstein himself never believed it, but at the same time it says almost nothing about the type of universe we live in. It can be adapted to the Big Bang, or it can support an alternative model like the steady state by changing a few parameters, something which Einstein actually did. The Standard Model of Particle Physics, the second great achievement of the 20th century, is similar. It prescribes the rules for the behavior of the subatomic world, but those rules don’t really care what the actual subatomic world is composed of. The Big Bang is different in this regard. It’s as much about what’s in the universe as how it came to be and how it works.
We must look outside of physics to find a theory that functions in a similar way: The theory of evolution comes to mind. There, scientists debate the specific mechanisms of evolution, but the underlying principles that all life originated from a simple replicator in the distant past and that life changes over time are taken as fact. The discovery that evolution was false, that organisms did not share a common history, and arose independently would necessarily upend much of biology, calling into question every established relationship between life on Earth, the commonality between the origin and function of an animal’s body and our bodies themselves, and the differential analysis of DNA between species and perhaps within species. The impact would be so huge, it would be difficult to understand all of the ramifications at once. Scientists would be sorting through it for years, if not decades. The fall out from the Big Bang will be no less dramatic in its own way. Essentially everything we think we know about the universe simply might not be true. The resulting damage to physics includes both the obvious and the less than obvious. The concept of Dark Energy, for example, was only introduced as a means to explain why the expansion of the universe appeared to be accelerating over time. In 1998, two international teams of astronomers attempted to calculate the rate of the expansion, what is known as the Hubble Constant, based on the distance of certain types of supernova. They determined that distant star explosions were much fainter than they should’ve been, and believed this implied they must be much further away than we thought. This also introduced an odd wrinkle: Though we could see these parts of space, which meant that light was traveling from these distant realms, the acceleration of the expansion implied that we could never travel there. As we ventured further out, the objects would move further away even faster, like running on an ever quickening treadmill. The term Dark Energy was coined to describe the mysterious, unseen force driving this increased rate of expansion, and was believed to account for a whopping 68% of the entire universe, but if the universe isn’t expanding, there is no need for Dark Energy, and scientists were wrong about more than two thirds of what makes up reality.
The Big Bang didn’t merely say the universe was expanding over time, however. All the time and space in the entire universe was said to have been set in motion during the initial explosion, expanding outward and evolving into the future as part of a unified spacetime continuum. Simply put, the Big Bang was seen to be the beginning of everything, all time, space, and matter. It sets a “date” for the birth of the universe and gives it a specific age, some 14 billion years. Before then, there was literally nothing, or at least nothing we can observe and measure. It also suggests the universe has an end-date of some kind, either collapsing in upon itself in a Big Crunch or expanding outward into nothing, a point where matter and energy would be distributed so sparsely over such a huge area, they would essentially cease to exist in any meaningful way. The demise of the theory means three immediate things. The universe might not have a start date and hence no end date, and there is likely no need for space and time to be viewed as part of the same entity, interwoven in a formulation that actually predates relativity. If they are no longer intertwined at the birth of the universe, they do not need to be considered part of the same continuum. The prevailing version of General Relativity, however, uses equations that treat space and time as part of a four dimensional manifold, one where the interval between two spacetime events is independent of the frame of reference. This viewpoint asserted that time itself is relative, the same as length, width, and height, and that the universe has no reliable clock: There is no way, even in principle, to say if two events occurred at the same time, or which was before and after. These equations will need to be discarded in favor of a different version that treats them separately, as Einstein’s original formulation actually did.
At a minimum, it allows for the idea of a universal clock, but this is the only one potential implication for our understanding of time: The Big Bang has also been used to provide time itself with a direction. The laws of physics alone do not differentiate between the past and the future. They can be run both forwards and backwards in time without bias between the two, but the real world doesn’t work that way. Time only runs in one direction. The past is completely fixed, each point in time entirely unique, and the future is not known with absolute certainty. The Big Bang, however, provides a description of the early universe that appears to solve this problem with an assist from the Second Law of Thermodynamics, entropy. Entropy is the principle that the disorder of a system only increases over time unless energy is applied. For example, if you were to divide a fish tank in half with a removable glass plate, color the left side with red dye and the right with green, and then remove the plate, the two sides would begin an inexorable process of mixing together. The fish tank would never “accidently” return to a state where the left side was red and the right was green. It would continue in a mixed state forever. Entropy is one of the few principles in physics that is non-reversible. You cannot go back or maintain a steady state unless you apply specific, directed energy to the system. Scientists believed that the moments after the Big Bang were a unique state indeed, so unique and ordered in the distribution of the elements and energy that all of time flowed forward because the universe itself was gradually moving towards a more disordered state. It was thought that the laws of physics were reversible, but their application in the universe was not because of its origin. Without the initial explosion, however, there is no reason to believe the earlier universe occupied a unique state, and there is no longer any framework that would give time itself a direction. This, combined with the breakdown of spacetime, suggests that our understanding of time is completely incorrect and needs to be entirely reimagined.
In that regard, a clue might be found in Einstein’s theories of relativity, one which ultimately led to the ascendance of the Big Bang in the first place and which might well be the biggest mistaken assumption in physics in the last century. In 1905, Einstein based his breakthrough Special Theory of Relativity on the notion that light traveled at a completely constant speed, C. He arrived at this conclusion because the speed was dictated at the time by the work of James Clerk Maxwell, who developed an equation that predicted such a constant speed. Einstein believed that the laws of physics were universal, and therefore wherever anyone was in the universe at any time in the past, however fast or far they were moving, they could use the Maxwell equation to derive the speed of light. In his view, light was essentially the measuring stick for the entire universe, supplanting time and space. Unlike everything else, nothing moved faster and it always moved the same (in the same medium). Einstein expanded on these ideas in 1915 with the publication of the General Theory of Relativity, gravity, which then became the underlying framework with which we understood the larger scale operation of the universe. Once again, light remained constant. The discovery that light from distant parts of the universe was shifted toward the red led other scientists to conclude that the stars we were observing must be moving away from us. There appeared to be no other explanation that could simultaneously account for light moving at a constant speed and the observation that it was shifted based on distance from the Earth. Either the universe had to be expanding or light couldn’t be moving at its prescribed speed. Scientists chose to assume light maintained its privileged position, but that might no longer be the case: The light from the far reaches of the universe remains shifted to the red even as it no longer appears the universe is expanding. The only explanation is to recognize that light must be losing energy via some mechanism, a currently discredited idea known as “tired” light, that we do not fully understand. As a result, Einstein must be wrong. Neither the Special nor the General Theories of Relativity strictly apply in all cases, at least at the time and distance scale of the entire universe.
This is not an easy conundrum to unravel. The speed of light appears as the constant, C, in everything from the famous “e equals mc squared” to the physics that allow for and describe a black hole. The underlying idea is that time slows as velocity increases all the way up to the speed of light, but the speed of light itself is not attainable because the equation that dictates this slowdown results in a division by zero, specifically the number one minus light squared over the speed of light squared. If you apply that to the force of gravity acting upon light, there will reach a point where the escape velocity equals or exceeds the speed of light, and hence light itself is trapped. The center of a black hole, known as a singularity, is said to be such a point where the equation returns an undefined result. The pull of gravity is so strong in that region that light itself can no longer escape, but if light doesn’t travel at a constant speed at all times, the underlying equation is no longer strictly valid in all cases. There might not be a singularity at all and hence no black holes. In fact, this might actually be a requirement if the universe truly exists in a steady state because a black hole can essentially “eat” parts of reality, taking them out of space and time entirely, from which they can never return. It’s not clear a universe that exists in a steady state can allow for black holes at all: They would ultimately consume the whole universe given enough time, though I do not believe anyone has seriously considered the question.
Interestingly, this same concept of a singularity, that is an undefined point that requires division by zero, was believed to describe the state of the universe at the instant of the Big Bang. All matter and time was said to start from the equivalent of the center of black hole. In my mind, there is an essential lesson here: Confronted with the fact that Einstein’s theories required division by zero in certain specific circumstances, producing an undefined result, scientists had two choices. They could’ve recognized that the theory was incomplete under the principle that the real world cannot return an undefined result, and invested their time and energy figuring out a formulation that eliminates the undefined state. Instead, they chose to assume that this undefined state actually exists in the real world, and from it they built an edifice that ultimately led to the Big Bang. Putting this another way: Our entire understanding of the history and structure of the universe for the past 50 years is based on an equation that doesn’t actually work. They made the exception, division by zero, into the rule and applied it to everything we thought we knew about the origin, current make up, and potential future of the universe. All of this will have to be rewritten and reconsidered now. There could be more as well: Dark Matter is said to account for approximately 30% of the mass and energy in the universe. Along with Dark Energy this meant that well over 95% of the entire universe was completely hidden from view, undetectable by any known instrument. The existence of Dark Matter was posited because galaxies rotate faster than they should according to their mass as established by General Relativity. Similar to Dark Energy, the solution was to propose that this additional mass was there, just in a form we could not see, but if Einstein’s theories fail on a universal scale, it is possible no Dark Matter is required. We simply do not know, and likely will not know for years if not decades. Physics itself is in flux and no one knows what the future holds for the first time in generations. The only thing we can say for sure: No theory or philosophy is safe as we come to understand what the world looks like without the Big Bang.