The term “inertia” is said to have been introduced by Johannes Kepler in his publication summarizing Copernican astronomy, EpitomeAstronomiaeCopernicanae, published around 1620. Kepler derived the term from the Latin word iners, which signifies idleness or laziness, using it to describe the inherent resistance of bodies to motion, as he believed that rest was matter’s natural state. Galileo Galilei later reconceptualized this idea, proposing that a body in motion continues in that state unless acted upon by an external force. Isaac Newton further formalized the concept, integrating Galileo’s insights into his own laws of motion. Newton’s first law states that an object requires a force to alter its state of motion or to begin moving from rest. Even today, the fundamental nature of this phenomenon remains somewhat enigmatic. For centuries, the fact that bodies do not accelerate infinitely when a force is applied has lacked a universally accepted, intuitive explanation; there is always an inherent resistance to any change in uniform motion. While the behavior of inertia is mathematically precise, a definitive, foundational explanation for the ultimate cause of this resistance to acceleration remains a subject of profound physical inquiry [1].

Newton’s reasoning remains highly interesting even today. From the outset, he considered what is now known as inertia to be an intrinsic property of bodies, which he termed visinsita: there was something within bodies that manifested as resistance when an attempt was made to accelerate them. Later, Newton posited that this resistance to acceleration stemmed from the body’s interaction with the absolute vacuum—a phenomenon he called visinertiae [1]. Newton was not alone; many researchers have sought to provide a logical explanation for inertia, a phenomenon described as a fundamental property of matter [1].

In July 2012, the discovery of the Higgs boson—the particle that supposedly imparts mass to other particles in the Standard Model, a property remarkably similar to inertia [2]-[5]—was announced at CERN (LHC). The so-called Higgs field interacts with other particles in much the same way that Newton envisioned the interaction of bodies with the absolute vacuum [2]-[5]. All these ideas regarding the Higgs field originated in work published during the 1960s by Peter Higgs, among others [6]-[11].

Regarding the experimental results from the LHC, it is worth clarifying that speaking formally about what it means to “see” the Higgs boson is complicated [6]-[11]. However, such formality is far removed from reality; the fact is that the Higgs boson can never actually be seen. This boson survives (manifests itself) for a ten-billionth of a trillionth of a second—a duration far too brief to be captured, either directly or indirectly, before it decays [2]-[11]. Given this fleeting timeframe, one might be tempted to ask whether something that exists for such a short period truly exists at all. Ultimately, how can something whose identity or manifestation is so short-lived impart mass to certain particles, especially when it is generated under conditions that are extremely difficult to achieve even with state-of-the-art technology and experimental research? These two experimental details—one concerning what is ultimately recorded in the accelerator to capture data for analysis, and the other regarding an experimental result involving such a fleeting manifestation under extreme conditions—baffle anyone studying or attempting to visualize the actual work of research teams in the field of particle physics [2]-[5][12]-[15].

At this stage, it is important to specify the key aspects of the phenomenon of inertia. Any theory regarding inertia must account for several factors associated with this phenomenon:

Resistance to a change of state—whether of rest or motion—manifests only at the very moment an attempt is made to accelerate the body.It is always antagonistic, opposing change.It is universal, meaning it is present in all material bodies.The reasons why this phenomenon remained unexplained for so long [1].

At one point, in conversation with his friend Richard Bentley, Newton speculated that there might be something divine underlying the ultimate causes of inertia—perhaps angelic figures responsible for pushing the Moon, for instance, to keep it in orbit around the Earth.

Over the years, as no adequate explanation for the ultimate causes of inertia has been found—much like with other phenomena that are difficult to explain—two trends typically emerge. On one hand, interest in the phenomenon fades, or attempts are made to overlook it. Around 1893, Ernst Mach formulated what is known as Mach’s principle, which asserts that the phenomenon of inertia arises from a body’s instantaneous interaction with the rest of the universe—specifically with distant masses that prevent its free acceleration [1]. On the other hand, there have been attempts, albeit reductive, to characterize the phenomenon as something fictitious, lacking objective reality [1].

In seeking the reasons behind the trajectory of this phenomenon, it is plausible that the mystery of inertia stems from the imprecise way the concept of “force” was incorporated into scientific knowledge, which likely hindered the development of an adequate explanation for the force of inertia. Ultimately, what is a force? How is a force defined? Newton addressed these questions, and one of his greatest contributions is said to be the definition of force via his second law: force equals mass times acceleration—that is, the agent that produces acceleration. However, describing what a thing does, or the effect it has on something else, does not constitute a complete definition.

In standard introductory physics courses, energy is defined as the capacity to perform work—specifically, the product of force and distance. A lingering question, however, is: how exactly does energy perform work? How does it exert the force necessary to do so?

This manuscript aims to answer these questions. It addresses the points raised above and explains how energy interacts with bodies to perform work—a process expected to refine the concept of force. Ultimately, it provides a clear and compelling explanation of the phenomenon of inertia.

It is impossible to determine any property of a completely isolated body—not only because it would exhibit no manifestations of any kind, but also because, ultimately, any interaction alters its properties. If the isolation is not absolute and there exists in the surroundings a field, a material body, or any agent capable of disturbing it, the body will exhibit a manifestation—such as acceleration. A force plays a role in any interaction. However, it should be clarified that for a force to accelerate a body, it must “grasp” the body in some way; broadly speaking, the force must hold onto the body. Pushing something with an open hand has led us to a misconception regarding interaction. The molecules of the body and the molecules of my hand do not come into direct contact; rather, the electromagnetic fields of the body’s molecules combine with those of my hand’s molecules to produce resultant fields that ultimately cause the acceleration. When a baseball bat strikes the ball, both deform to some extent due to the interaction. The molecules of the two bodies do not actually make direct contact; instead, their electromagnetic fields interact to produce that deformation. Literally, the notion of pushing something with one’s hand leads to a misunderstanding of the interaction process and, ultimately, of the concept of a force interacting with a body. A force is not a wall that arrives and pushes the body; it is something more sophisticated involving the interaction of fields—specifically, a superposition [12]-[20].

Ultimately, every interaction involves the action of a force. For a force to produce acceleration, it must grasp or capture the body through the interaction of fields. Forces do not push the body; rather, they immerse it in fields, and this is what produces the acceleration. A natural conclusion is that, in order to accelerate a body, the body must possess a field; otherwise, it is impossible. As will be seen in the following sections, the superposition of fields creates a pressure difference, which is what ultimately causes acceleration.

In general, the following explanation applies to cases where a force is exerted on charged, albeit neutral, bodies to produce acceleration. However, to simplify the concept of inertia and make it relatively easy to understand, we will examine the simplest case in which this phenomenon manifests.

Consider an electric charge—such as a proton—placed within an electric field [12]-[20]. This external electric field could be generated by another charged particle (an electron, a proton, or a more complex configuration) (Figure 1).

Figure 1. An electric charge q is immersed in a uniform external electric field E ¯ 0 . The radial electric field of the charge is E ¯ q = q 4 π ε r 3 r ¯ .

The aim is to provide a compelling and provocative explanation of the phenomenon of inertia and its related effects. This is accomplished without recourse to intermediary particles; instead, the concepts of force and energy play a fundamental role [13]-[15].

At this stage, in order to offer an alternative explanation of inertia, it is essential to restructure and further develop certain traditional physics concepts—such as work, energy, the electric field, electric pressure, and energy density. This approach enables the concept of inertia to be addressed conclusively within a new theoretical framework while highlighting the central role of the field.

In this description, the definition of force varies slightly; in a sense, it differs from convention and relates closely to the concept of pressure. While pressure is traditionally defined as force per unit area, the starting point here is energy rather than force. In other words, in nature and across various experimental situations, what truly exists is the field—for example, the electric field surrounding an electric charge. Grounded in this perspective, force represents the field’s action upon other bodies [12]-[20] (Figure 1).

The importance of the field is evident in the example of a baseball bat striking a ball. In physical reality, this contact ultimately reduces to an interaction of fields. The field serves as the operational basis associated with other concepts, such as energy density, which in turn is linked to the concept of pressure.

In summary, the concept of a field is fundamental. A field modifies space in such a way that another body can exist and experience a force within that modified space. Given the existence of an electric field, for example, there is also an associated energy density, which is expressed as follows:

where u E represents the energy density produced by the electric field E .

Nature or experimental conditions determine the value of the field. Energy is generally defined as the capacity to perform work. Whenever a region of space contains a field, an energy density—given by the aforementioned expression—also exists. How exactly does a state described by that expression perform work [12]-[20]?

To answer this question, we briefly return to first principles and recall the definition of pressure as force per unit area. The expression for electric pressure is:

Multiplying and dividing by distance or displacement d , we obtain:

In the numerator, we have force times distance—which represents work or energy—and in the denominator, volume [12]-[20]. Consequently, this can be rewritten as energy density:

For the proposed framework, it is essential to express pressure explicitly in terms of the electric field.

From this relation, it can be concluded that whenever an electric field is present, an energy density is generated by squaring the field value. This energy density proves to be identical to pressure. This fundamental conclusion explains how energy performs work: a pressure gradient can induce acceleration in a body, thereby altering its state of rest or uniform motion [12]-[20].

To accelerate a particle, the particle must possess a charge and, naturally, a field. Particles lacking a field cannot be accelerated by another field. Material bodies are typically composed of positive and negative charges. Let us examine how a field accelerates a charged particle.

For instance, consider a particle with a charge—uniformly distributed throughout the volume of a non-conducting sphere of radius a —initially at rest and immersed in a uniform external electric field E ¯ 0 ; it interacts with this external field in the following manner (see Figure 1).

In this configuration, the field produced by the charge q is superimposed on the external field, and the resulting field is expressed as...

The first term represents the electric field produced by the charge. Here, r ¯ / r is the radial unit vector in a spherical coordinate system concentric with the sphere, such that...

Therefore, substituting into Equation (5) Equation (6), the resulting electric field is given by

Next, the square of Equation (7) is evaluated.

Substituting this expression into Equation (1), the electric pressure becomes...

In introductory physics courses, it is stated that a positive charge accelerates in the + j ^ direction under the influence of an external field. However, it can be observed that the electric pressure is greater in that direction. Therefore, one can conclude that electric pressure acts as a suction pressure; the charge tends to move toward the region of higher electric pressure—a completely unexpected result.

Due to the harmonic functions appearing in Equation (9), the pressure exerted on the electric charge differs between its + j ^ and − j ^ sides.

Under these conditions, the charge accelerates to the right in Figure 1 due to this pressure difference. If the pressure were the same on both sides of the charge, it would remain at rest instead of accelerating.

The resulting pressure profiles are shown in Figure 2.

Figure 2. An electric charge q immersed in a uniform external electric field E ¯ 0 . The radial electric field of the charge is given by E ¯ q = q 4 π ε r 3 r ¯ . The resulting pressure profiles on both sides of the charge are shown.

The contribution of both fields is required to generate acceleration. A compelling conclusion is that the pressure typically develops at the rear—relative to the direction of motion—implying that this pressure represents the inertial force opposing the body’s acceleration. Furthermore, the mere existence of an external field does not produce the pressure differential. Accelerating a charge requires both its own field and the external field; consequently, an object lacking its own field cannot be accelerated [1].

Equally significant is that this pressure consistently appears on the side opposite the charge’s acceleration. Due to field superposition, this rear pressure must always be lower than the pressure at the leading edge—which drives the acceleration—otherwise, no acceleration would occur. This mechanism is universal, applying to all material bodies, and it always opposes acceleration.

However, a scenario where the inertial force becomes zero could exist. This case would be remarkably interesting and hold practical applications. The explanation is presented below. If the pressure on the left side of the figure is set to zero, it follows that...

In an acceleration experiment, it is theoretically possible to reduce inertial pressure, thereby enabling significantly more effective particle acceleration. This finding holds strong potential for specific applications in particle accelerators and spacecraft propulsion.

In any scenario involving object acceleration, eliminating inertia—the force opposing free acceleration—remains highly desirable, although generating a suitable field to achieve this may present substantial technical challenges.

When the accelerated particle is already moving at a velocity v ¯ , significant differences arise, as the field expressions are modified by relativistic effects [19]-[21]. Specifically, the charged particle’s own field becomes...

where γ is defined as...

The particle’s field remains radial but is no longer isotropic; it now exhibits an angular dependence. The field lines become less dense at the front and rear relative to the direction of velocity. In other words, the field weakens along the longitudinal axis and intensifies in the transverse direction [21].

Equation (13) shows that when v ¯ = 0 , it reduces to the expression for the electric field of a charge at rest. Substituting Equation (6) into Equation (13) and adding the external field, the resulting net field becomes...

Squaring this expression and substituting it into Equation (1) yields...

Two observations can be made here: first, along the longitudinal axis—both ahead of and behind the charge—the expressions in Equation (15) become...

and

..., respectively, and the resulting difference is given by...

Equation (17) represents the inertial force. The second observation is that, at relativistic speeds, continuing to accelerate the particle becomes increasingly difficult. This difficulty arises because the electric pressure differential between the forward and rear hemispheres decreases at high velocities; indeed, it is precisely this pressure difference that drives the particle’s acceleration.

The counter-pressure from Equation (17)—which represents the inertial force—is always present. At very high speeds, the Lorentz factor γ in Equation (18) suppresses this differential pressure, causing it to approach zero as the velocity approaches the speed of light. Consequently, as the electric field of the moving charge diminishes along the longitudinal axis, the external field required to sustain the same pressure gradient must increase. Furthermore, because γ increases asymptotically with velocity, accelerating the particle in this high-velocity limit becomes substantially more difficult due to the reduction in the charge’s field values ahead of and behind the moving particle [21].

Following a rigorous analysis, an innovative perspective arises: the possibility that inertial force has always been present but was marginalized in the history of physics due to a flawed interpretation of the concept of force. In light of this, the Standard Model’s Higgs boson—which is posited to influence the inertia and mass of only a specific subset of particles—might fall outside the natural scope of particle physics. The arguments supporting the Higgs mechanism appear overly intricate and somewhat contradictory. Specifically, the hypothesis of a “universal molasses” that hinders particle acceleration at low velocities yet becomes negligible at relativistic speeds directly contradicts both Newton’s first law—as no such friction exists—and Albert Einstein’s theory of special relativity, which precludes an absolute reference frame and establishes that relativistic mass scales with velocity. If the interaction between a particle and the Higgs field were velocity-dependent, the field itself would constitute an absolute reference frame, a conclusion that fundamentally violates relativistic covariance.

In this study, using established physical foundations such as energy density and pressure, we have mathematically demonstrated that particle inertia is an emergent property closely linked to field configurations. Because both energy density and pressure are fundamentally derived from the field, it follows that the field constitutes the most fundamental concept in nature.

This framework offers a novel theory on the mechanism of inertial force, explaining it through the interaction of a particle’s intrinsic field with an external field. In other words, inertia arises during acceleration as a direct consequence of field superposition. Accelerating a body possessing its own field is only possible through the application of an external field; to be accelerated, the particle’s field must couple with or be “captured” by another field. Ultimately, the field remains the primary element, while inertia, energy, and pressure are secondary concepts dictated by its geometry.

Furthermore, this entire formulation eliminates the need to introduce mediating agents for particle interactions. Postulating a mediating boson requires a secondary explanation for the interaction between the force-carrier and the particle itself, unnecessarily complicating the description of elementary particle dynamics. In this regard, Newton’s initial intuition was correct: there is an intrinsic quality within the particle itself that resists acceleration. This study suggests that “something” is simply its own intrinsic field.