# Relativity, Gravity, and the Origin of the Three Equivalence Principles

**Sub-title: ***The Origin of Rest Mass*

**Note:** It is very important to know that the author involves or mentions the weak and the strong equivalence principles only in regard to their post-modern modifications. The classical and modern understanding of these principles do not transfer into post-modern physics.

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Some days ago, as I walked home from the bank, I pondered about the universe, and there was this very obvious smile on my face that anyone close by could notice.

Now, *what thought made me smile?* Simple, it was the connection between relativity, gravity, and the three equivalence principles in the universe.

I was thinking about the connection between gravity as the acceleration limit of the universe and how it results in the three equivalence principles in the universe.

And now, in this article, I want to share with you what my thoughts on the universe were on that beautiful afternoon.

So, in this article, when I refer to the three equivalence principles, it should be clear that I’m referring to *the weak equivalence principle, the** strong** equivalence principle, and the universal equivalence principle.* The latter is what simply unifies the former two equivalence principles.

Now, we are learning from post-modern physics that the three equivalence principles are the simple results of the new discovery that no body can accelerate greater than gravity.

No body can accelerate greater than gravity.Click To Tweet

So, we are learning for the first time of the true relativistic origin of rest mass and initial mass to be due to the fact that no accelerating body can accelerate greater than gravity.

This is a profound truth that completes our understanding of the universe and of the theory of relativity as its foundation was laid down in the 1900s.

We have learnt from modern physics that as a result of the principle of relativity, we cannot move faster than light. But now, we are also learning from post-modern physics that due to the principle of relativity, we cannot accelerate faster than gravity.

This is one of the beautiful consequences of the generalization of the principle of relativity to include gravity and accelerated frames or non-inertial reference frames.

Thus, light and gravity are respectively the speed and acceleration limits of the universe. This is the true generalization of relativity, and like I said, this completes our understanding of relativity and the universe.

Light and gravity are respectively the speed and acceleration limits of the universeClick To Tweet

So, today, we are now learning the true origin of the three equivalence principles which is simply because no body can accelerate greater than gravity.

While ideally, this article should be about how the relativity principle in regards to gravity is responsible for the universal equivalence principle since the universal equivalence principle naturally sums or embodies the weak and the strong equivalence principles, it is however not much of a deviation to mention the other two equivalence principles.

This is important especially when we bring our focus on the weak equivalence principle. We are learning in post-modern physics that rest mass is as a result of the unaccounted proportion by which gravity accelerates greater than an accelerating body.

So, we now understand why the rest mass of a body is constant in the universe. The mystery of the constancy of rest mass is related to the mystery of the constancy of the speed of light.

Listen: gravity accelerates greater than any accelerating body by a proportion of acceleration that is related to rest mass, and this is why rest mass is constant.

To help us understand the constancy of rest mass, we just have to look at the constancy of the speed of light. Let’s imagine that a body were to be in uniform motion.

Now, according to the principle of relativity, such a body would observe light zap past it at a constant speed regardless of the speed of the body.

Now, imagine that the speed of light was related to mass, won’t such a mass be constant? Yes, it would. However, we know that the speed of light is not related to mass, but this is not the case with gravity, where we now have to deal with acceleration and not uniform speed.

So, when this our body accelerates, it realizes that just as it cannot travel faster than light, so also can it not travel faster than gravity. Thus, we have a case where the accelerating body cannot accelerate greater than gravity.

But unlike light, the acceleration of gravity is related to mass, and the proportion by which gravity accelerates greater than the accelerating body is what is specially related to rest mass in the universe.

This is why rest mass is constant. It is for the exact same reason why the speed of light is constant, which is the principle of relativity. This post-modern discovery, therefore, ends the debate in some circles if the speed of light is a fundamental constant. Yes, it is, just as the rest mass of a body is a constant.

Rest mass is constant for the exact same reason why the speed of light is constant, which is the principle of relativity.Click To Tweet

The long-hidden connection between light and gravity (or rest mass) can only be revealed by the principle of relativity, and as relativity shows, no accelerating body can travel faster than both light and gravity.

A special reference is made to an accelerating body in this case because for the case of uniform motion, the body won’t be able to travel faster than only light. Gravity only becomes involved when we are dealing with accelerated motion.

This article is, therefore, showing us how the principle of relativity is responsible for the existence of rest mass in the universe. I thought about this some time ago and it made me very happy!

Furthermore, this article is calling us to consider something pretty simple and which our predecessors in science overlooked or didn’t consider at all.

That is, *if we think that a body cannot travel faster than light, why stops us from also thinking that a body cannot travel faster than gravity?* And while light imposes a speed limit on moving bodies, gravity imposes an acceleration limit on moving bodies.

We must understand these distinct limits imposed on motion by light and gravity as their underlying fundamental connection in the universe.

Light is not the only traffic law in the universe, gravity is also a traffic law or a travel limit for all accelerating bodies in the universe.

So, this is where we see the big picture between relativity, gravity, and the three equivalence principles.

The new discovery that rest mass is as a result of the fact that no accelerating body can accelerate greater than gravity opens up our understanding to the broader picture of how this simple truth is responsible for the three equivalence principles.

The pure acceleration of a body is related to inertial mass, while the acceleration or the value by which the acceleration of gravity is higher than that of an accelerating body is related to rest mass.

So, now, by the inverse square law, these two forms of mass are related to acceleration and a crucial factor in post-modern physics called *rest gravity*.

This is how we come to the profound discovery of the universal equivalence principle which informs us that the weak equivalence principle and the strong equivalence principle are equal.

Until next time,

I will be here.

– M. V. Echa