Historical Context

To understand the current discourse, a brief historical overview is essential. In 1905, Einstein published a landmark paper on special relativity, positing that all motion is relative and that only the speed of light remains constant. This groundbreaking work reshaped our perspective on the universe, suggesting that both physical distances and our perception of time are malleable, yet it did not mention space-time.

Einstein's special relativity was one of four pivotal papers produced during his Annus Mirabilis, a year when he achieved much of his notable work while working at a Swiss patent office, struggling financially due to his inability to secure a teaching position.

Three years later, Einstein's former teacher, Hermann Minkowski, who had previously described Einstein as a 'lazy dog uninterested in mathematics,' contributed his own perspective. Minkowski, an advocate for geometric mathematics, proposed that Einstein's findings could be simplified by merging space and time into a singular mathematical entity: space-time.

Using the equation s² = t² - x² - y² - z², Minkowski illustrated that time could be viewed as an additional dimension that behaves oppositely to traditional spatial dimensions. In his framework, the appropriate way to measure distance in a relativistic context is through the spacetime interval, which quantifies the subjective experience of traveling between two points.

Einstein recognized the elegance of this approach and integrated it into his ambitious work on general relativity. Unfortunately, the complex mathematics involved pushed him to his limits, prompting him to seek collaboration with mathematicians like Hermann Weyl to complete his magnum opus. This endeavor once again revolutionized physics, albeit through a method that stretched Einstein's scientific understanding.

The scientific community embraced general relativity with enthusiasm, with the exception of Kurt Gödel, a close friend of Einstein and arguably the most brilliant mathematician of the twentieth century. Gödel argued that general relativity compromised the idea of equal frames of reference and required a cosmic reference frame to describe the background structure, leading to peculiar scenarios where time could loop back on itself, challenging causality.

Despite sharing these concerns with Einstein, the broader scientific community remained largely unconcerned. Temporal loops became a curiosity for students while their wider implications were largely disregarded. Einstein took these critiques seriously, spending part of his later career exploring alternative models of relativistic effects.

Over the years, the concept of space-time has become the dominant framework for discussing relativity, with the perception of it as merely a mathematical tool being largely overlooked. Now, physicists casually discuss 'block universes' without questioning the foundational assumptions.

Questioning Established Ideas

Why is it vital to revisit this historical narrative? To emphasize a crucial point: scientific advancement occurs when brilliant minds operate at the edge of their capabilities, where errors are most likely. Researchers tend to rely on familiar tools that simplify complex ideas. Once a breakthrough is achieved, others adopt these ideas without scrutiny, as questioning them offers little advantage. Everyone prefers to build on the giants' shoulders rather than challenge their footing.

However, the danger lies in failing to continually question our foundational beliefs, leading to the construction of conceptual shortcuts that impede further progress. For a century, we have struggled to reconcile relativity with quantum mechanics, and I propose that the seductive appeal of geometric reasoning plays a significant role in this stalemate.

So, what are the shortcomings of general relativity? As a mathematical framework, it is effective and stands as one of the most successful scientific theories in history, second only to quantum mechanics in terms of empirical validation. Yet, as a lens through which to view the universe's operations, general relativity encounters significant challenges.

For instance, since Einstein's era, the discovery of cosmic microwave background radiation has provided concrete evidence of a reference frame in the universe, countering the idea of absolute relativity. Any spacecraft equipped with a camera can ascertain its velocity relative to other objects in the cosmos, affirming that, at least in one observational context, velocity is not entirely relative.

Furthermore, the geometric interpretation of space-time seems incompatible with another fundamental concept in physics—the Planck length. This minuscule scale represents the point at which our conventional understanding of distance begins to falter. In general relativity, the perceived length of an object is contingent on the observer's frame of reference, which clashes with the notion of an objective minimum length. If both ideas are to coexist, the Planck length must exceed the observable universe in most conceivable reference frames, casting doubt on the Minkowski model as an absolute characteristic of reality.

Additionally, the definition of a relativistic reference frame remains ambiguous. We are often told that light, traveling at maximum speed, experiences no time. However, significant cosmic time elapses between the emission and absorption of a photon, and numerous events transpire in other reference frames. This raises the question of whether the photon's reference frame is genuine or merely a mathematical convenience.

Perhaps the most troubling aspect is that the concept of space and time as a unified entity lacks empirical testability. The intertwining of these dimensions is not a necessity for general relativity's functionality; rather, it serves as a convenience. Alternative interpretations could achieve similar outcomes with different premises. For example, we can reframe Minkowski's equation to t² = x² + y² + z² + s².

By employing a touch of high-school algebra, we eliminate the problematic negative sign and the need for complex numbers that typically accompany relativity. While this approach necessitates a reevaluation of the meanings of t and s, is that too high a cost?

It's important to note that merely rearranging variables does not provide an alternative solution, but the lack of such explorative thinking is concerning. Time does not operate like a dimension; it does not allow for backward and forward movement. Yet, nobody seems inclined to label it as a 'monodimension' or explore the mathematical implications of a one-way dimension. Perhaps this is because it contradicts existing frameworks.

Taking the concept of space-time at face value leads us to perceive space and time as a solid construct. Initially, I found clarity in visualizing the Big Bang as layers of time radiating outward from a four-dimensional point. A rationale for the universe's finite age in this model suggests that traveling back in time would simply mean moving forward on the opposite side of the universe.

However, physicist acquaintances advised against this interpretation, noting that the rate of spatial expansion is not constant. Thus, if one adheres to the solid universe model emanating from a point, another dimension must be introduced, like a 4D vase submerged in a mysterious pond. Cosmologists resist this complexity.

Moreover, the lack of observable curvature in the universe leads cosmologists to prefer an infinitely large universe at the moment of the Big Bang, despite the untestable nature of this assertion. Consequently, we are expected to maintain the block universe concept while limiting our understanding to mathematically secure interpretations.

This selective conceptualization is troubling; it compels us to make concessions for a theory that can only be tested locally, yielding no benefit from treating it as an unqualified truth, while stifling innovative thinking.

Consider this scenario: many individuals who grasp relativity conclude that traveling faster than light would result in moving backward in time from another's perspective. This reasoning is flawed, effectively ruling out faster-than-light travel.

Setting aside the fact that general relativity permits violations of causality, as Gödel noted, let's reflect on the ramifications of this conclusion. Is it genuinely time that reverses, as a space-time diagram might imply, or is it merely an appearance?

To illustrate this, let’s examine a hypothetical faster-than-light (FTL) vehicle, akin to an Alcubierre warp drive, which works by compressing space-time in front of the ship and expanding it behind. As this ship emits light pulses during its journey, each pulse encodes a number incrementing as the ship advances. Upon approaching a planet and deactivating the drive, what does an observer on the planet witness? The ship appears abruptly, followed by a series of pulses that seem to count down in reverse order. This creates the illusion of reversed causality.

This situation is not surprising; time isn't reversing for anyone. The light pulses take longer to reach the observer. Although warp drive remains speculative, it highlights how a misleading understanding derived from a mathematical shortcut can lead to erroneous conclusions. Many of us have confidently accepted the notion that FTL travel is impossible, believing we have grasped a complex concept. Space-time diagrams can elucidate relativity—until they don’t.

A more nuanced and insidious instance of this phenomenon occurred in Scott Aaronson’s critique of Stephen Wolfram's 2002 book, A New Kind of Science. Wolfram suggested that space might be viewed as a vast network with particles as knots within its fabric. This proposition sparked controversy among scientists. While some criticisms were warranted, Aaronson's most compelling argument was that any discretized model of space, as Wolfram proposed, would inevitably yield frames of reference that do not respect causality, thereby rendering his model untenable.

At this juncture, two facts become clear: first, general relativity does not inherently uphold causality; second, Minkowski space-time should be regarded as a localized approximation of reality, as most reference frames cannot be effectively described in a universe that accommodates quantum mechanics. Yet, how many noticed this nuance versus those who felt vindicated by Aaronson's critique, considering it yet another reason to dismiss Wolfram's ideas?

Stephen Wolfram is a multifaceted figure, and opinions about him vary widely. However, he deserves credit for his persistent exploration of innovative approaches to fundamental physics. Aaronson also merits recognition for his genuine engagement with the ideas; his analysis of Wolfram’s work sheds light on the operational frameworks required for discrete models of space.

This tendency to prioritize established ideas over novel theories has profound implications for scientific progress. Take, for instance, the causal set program, which I find to be one of the more promising avenues for quantum gravity. Causal set theorists strive to quantize reality by mapping the event structure—identifying how specific events influence others. While their efforts are commendable, they confront immense challenges, as their approach is built upon certain untestable assumptions from mainstream physics. They inherently accept Minkowski space-time as foundational, which complicates efforts to model gravitational distortion and photon existence within their framework. Personally, I found this immensely challenging.

An alternative approach I propose is to conceive of a network resembling space that evolves over time and examine whether a locally coherent event structure can emerge from it.

So, if space-time is an inadequate framework, what is a better alternative? The straightforward answer is to recognize that time constitutes a distinct phenomenon compared to space. However, this realization does not fully address the challenges presented by relativity. We must still account for time dilation as one accelerates and how space distorts under mass influence. I will defer a comprehensive proposal to future discussions, but I hope to provide a glimpse of a more productive way to approach our universe.

Regarding time dilation, one strategy that aligns with string theorists' methods involves compact dimensions. We can conceptualize the space-time interval that represents our subjective experience of time as encapsulated within a confined space. In this model, the faster one travels, the less subjective time is experienced. Objects either perform work traversing the universe or engage with one another. While this approach presents challenges, it also has advantages, particularly concerning mass, which is intricately tied to particle movement within confined spaces. This is advantageous because, in classical general relativity, one must grapple with two distinct definitions of mass (relativistic and rest mass) without a means to reconcile them—a mere assumption we are expected to accept.

To conceptualize how space deforms, I highly recommend a brief YouTube video that clarifies the impact of gravity. It illustrates that visualizing gravity's effect is straightforward: space collapses toward a mass, akin to an edible rug being drawn into a hungry mouth. The larger the mass, the more space it consumes. This is the essence of general relativity, building upon the foundation laid by special relativity. It’s time to abandon the overly simplistic bent sheet metaphor that is often invoked; this is the reality of what occurs.

But why engage in these complexities, you may wonder, if the mathematical framework of general relativity is functional? After a century of theoretical stagnation in physics, we owe it to ourselves to think creatively and embrace risk. Furthermore, quantum mechanics consistently suggests that quantum effects may be non-local. If this hypothesis holds, then a geometric perspective of the universe is fundamentally flawed. Geometry serves as a valuable tool, yet it relies on our intuition regarding mathematical continua, which cannot be trusted in fundamental physics. We should anticipate that geometry emerges from physical interactions rather than being a precondition.

For years, physicists have maintained that a thorough understanding of the science necessitates comprehension of the math. What if the reverse is true? What if the current mathematical constructs are so convoluted that they obscure our physical intuition, much like they did for Einstein? I propose that if our understanding is limited to the mathematics, we may, in fact, grasp nothing substantial. Perhaps the path forward requires us to adopt a posture of humility and a willingness to set aside the geometric cleverness that has carried us this far. In essence, the future of physics might resemble the ambitious dreams of a clerk in a Swiss patent office, tempered by a healthy dose of humility.

The first video titled Does the Past Still Exist? discusses the philosophical implications of past events in the context of time and space, challenging conventional understandings of temporal existence.

The second video, Has The Future Already Happened?, explores the concept of time and its implications on future events, raising questions about determinism and the nature of time itself.