What is so special about E = mc2?


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‘E= mc2’, the mass-energy equivalence, is an innovative equation by Albert Einstein in 1905. It was Einstein who showed that mass and energy are not different; these are two different representations of the same thing. In his paper, Einstein described E = mc2 as, where L is lagrangian, denoting a general form of energy and V2 for speed of light in vacuum.

Before Einstein, no one knew that mass at rest also owns energy, which is E = mc2. The enchantment of this equation is in its actual meaning. You won’t be able to find anything special about it if you don’t understand this equation.


Understanding E = mc2

The E = mc2 holds some fascinating meanings in it, which are necessary to understand to explore its excellence.

  1. The mass at rest also possesses some internal or intrinsic energy, which is equal to.
  2. The small amount of mass exhibits a large amount of energy.
  3. The equation simply tells that the change in energy of the system or an object will simply create a difference in mass.

Based on these, we will explore the excellence of this equation.

The Beauty of Science lies in it

Let’s do a short experiment without any setup. Consider two table fans, A and B of the same components. Just switch on one of the fans and keep the other as it is. The moment, the former starts working, it will have a larger mass than the later”. 

This outcome has changed the idea of the mass. Mass is not just the sum of the masses of the parts of the object, but it also appears from energy. So, how does the former fan got this energy? The former exhibited the kinetic energy (k) due to the motion the fan blades, the change in position gave potential energy (v), and the friction caused thermal energy (T). Therefore, the sum of these energies divided by c2 contributes to the extra mass.

Though this extra mass is not much (approx. 0.0000000001 kg), but this small mass can exhibit a large amount of energy (approx. 9 ´ 107 joules). This example clearly shows that a small amount of mass can produce a large amount of energy. This is the superiority of this equation. This single equation can explain the formation of the matter from energy and energy from matter.

I would like to highlight a few more examples that demonstrate how wonderfully it explains the universe. 


One such example is ‘The Big Bang’

We know that The Big Bang is the leading explanation of the evolution of the universe. The singularity exploded, an enormous amount of energy was released, and transformed to matter.

Give yourself a minute to think, “Why is it so?” – The answer is, because of Einstein’s E = mc2. The singularity had infinity mass density, which transformed into a large amount of energy. The released energy formed into different masses after the temperature cooled down. The concentration of these masses constitutes the universe. 


The next example, “The formation of stars and the sun, and the energy released.” 

A few billion years ago, the stars and the sun were formed. The question is, “How did these two forms?” “How are they able to emit such a large amount of energy?” – The answers are given by E = mc2. The sun, and other stars, was formed by the collapse of the huge gas clouds having a tremendous amount of energy.

The gravitational energy of the clouds transformed into kinetic energy. The temperature at that instant was approximately a few thousand degrees Celsius, so the high temperature also contributed to the energy.

This energy transformed into mass. Several nuclear fusions are occurring inside the center of the sphere. These nuclear fusions inside the stars release a large amount of energy, given by E = mc2, creating a difference in their masses.


Another example, I like to tell is “Binding Energy”

Let’s start the Binding Energy, “B.E. is the energy that is needed by the nucleus to separate into its constituents or you can say the energy that is needed for the nucleus to hold itself.” Now, coming to point, this binding energy is also explained by the mass-energy equivalence.

Consider an element, for simplicity, let’s take hydrogen isotope as an example, consists of one atom and one neutron. The sum of the mass of the atom and neutron is 2.01649u, which is the expected mass of. But, the experimental observations told another story.

The observed mass of came out to be 2.014102u, which is less than the 2.01649u. So, where is the missing mass? The science behind the missing mass lies in the meaning of E = mc2

The fusion of atom with neutron released a large amount of energy to produce. This released energy creates a difference in mass Dm. Therefore, E = Dmc2, simply means that Dmc2 much amount of energy has to be given to separate it to and neutron. If and neutron undergoes nuclear fusion to form, it will release Dmc2 energy, and this change in energy also changes the mass with a difference of Dm.


There are a lot of natural phenomena that could not explain without E = mc2. Moreover,       this equation is also the pillar of nuclear science and technology.

“In a nutshell, I like to conclude that this equation is strong enough to explain everything, from the simplest things of mass and energy to the universe. It is the most consistent explanation to nature” – This is the reason why it is so special. 

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