WHAT DOES ENERGY REALLY MEAN?

“Energy is the ability or capacity to do work"

That was my High school Physics teacher's favourite quote. A rather simple, and self-explanatory definition. Which in retrospect, is a fitting description of him as a person, he was bald, wears geeky glass, and always wore a suspenders. I'll love to describe other fascinating attributes of Mr Idris's personality, especially his great fashion taste a little bit, but that can wait.

source

It might interest you to know that there is much more to the simple definition of energy, and in this article, we will be exploring the concept of Energy.

Energy is the bedrock of everything you see or know right now, that's how important it is. It's everything you see around you, light, matter, gas etc. These are all the different forms of energy. Now, to understand what I mean let's go through a thought experiment. Try to think about every possible physical object in the universe right now – you will most likely find that task extremely difficult to accomplish.

If it is physical then it has mass - ‘M'.

Now think of other things that aren't physical, light may come to your mind. We know that light is a form of electromagnetic waves and we know it moves at a very fast speed

So, let's call the speed of light - ‘C'.

THE EQUATION

One of the best equations that describe energy is Einstein's E=mc^2.

source

For starters, E stands for energy, M stands for mass – a measurement of the content of matter. And ‘C’ stands for the speed of light. We also understand that the total amount of energy or matter is constant, meaning it doesn't change. Just as the infinite pleasure of knowing its Friday night, doesn't change. Yes, that's the thing the grand total never changes, its always the same, everywhere in the universe! Matter sometimes changes to some form of energy and energy could change to some form of matter too. They are both the same thing of different manifestations, unified by Einstein's theory of General Relativity.

Let's take a little time to talk about C, the speed of light – the universal speed CONSTANT, nothing ever travels faster. And why do we have to multiply the matter and the speed of light squared to get energy? This is because of all forms of energy, light waves or radiation travels at the universal constant of 300,000 kilometres, or 299,792,458 metres every second.

Atoms are the smallest indivisible part of any matter, what this means is, imagine you take an object, any given object really; and you start splitting them into halves. Even if you succeed to keep cutting out a half, you will eventually reach the smallest part (the atom). If you decide to split the atom, (which is a very bad idea) the explosion of energy that the atom will release, will come out with this same universal constant; the speed of light. But why is the speed of light "C" squared in E=MC^2?

source

It is because of kinetic energy, it is proportional to mass i.e if we increase the mass of a moving body the kinetic energy or energy of motion also increases at exactly the speed squared every second. Example: While learning how to drive, your driving instructor probably taught you that if you double your speed, the braking distance is four times longer. Imagine you are in a car on the road and your speed covers thirty meters every hour, call it point A. If you double your speed from point A to point B and apply your break – at this point there is no mechanical force pushing the car forward-it will take four times the distance before it stops. What pushes it forward after the breaks have been applied is called kinetic energy.

Personally, I started thinking about this as a kid each time I followed my mom to the market. In some parts of Nigeria, public vehicles, especially buses, never closed the door of the bus, even while driving. Sometimes they drive at very high speed and suddenly they just hit the breaks! I remember always waking up with fear each time I hear the loud sound created whenever the door slammed closed. Now I know that what happened was that the door of the bus was in motion thereby creating kinetic energy and immediately the driver hits the breaks, motion stops, the potential energy was converted to kinetic energy and that kinetic energy or motion energy. And when the door slammed, on the bus most of the energy was converted to sound, bending the iron etc.

HOW WE GET MATTER!

If the speed of a body in motion starts to get closer to the speed of light, it starts increasing in size and mass this is created from the energy that is being applied to help the body reach the speed of light. To understand this let us do a little mental experiment, Imagine you are on a fast moving train, your train is moving so fast it almost reaches the speed of light. At the speed of light, if you keep adding more energy trying to make the train go faster than its current speed, you will notice that the train will start getting heavier. It will start increasing its content of matter, you can interpret it as thus: The energy added will start locking themselves in atoms which will add more matter.

I am sure that by now you will have realised that the amount of energy stored in a single atom is unbelievably large. This is how the atomic bomb gets its amazing powers. A man created a machine that could split the atom and called it a bomb.

What is Energy... Again? Energy is what you get from multiplying a unit of mass with the square of the speed of light. Huhn? What's that? It's different from the first definition?? Well, not really, no... Not even a tad bit. But, you could say this is the mathematical definition of Energy.

SO HOW DID WE GET TO KNOW ALL THIS?

THE LAW

"Energy can not be created or destroyed, but can be transformed from one form to another”. I remember always reciting these words to myself as a kid whenever I was in the dark. I used to be afraid of the dark and always used to think a ghost would jump out of thin air. So, when I got to know about this law I began reciting it every time to comfort myself from the fear. Somehow I knew that anything that could interact with my physical body had to be a form of energy. So even if a ghost appeared from thin air it wouldn’t be able to interact with my body or harm me because it would be defying the law of Conservation of energy and therefore can’t happen – in our known universe at least.

source

We only deduce what's likely and unlikely and some things are so unlikely we call them impossible. So now we know the law that drives this thing, it is called the Law of Conservation of Energy.

HOW DID WE KNOW?

In the early 20th century, scientists were able to discover that matter itself can be created from energy and vice versa. This is just another change of form, after these discoveries, the conservation law of energy was extended to become the conservation law of matter and energy. Matter and energy can neither be created from anything nor destroyed, to the point of complete erasure from reality. Albert Einstein was the first to mathematically derive this in the formula E=MC^2.

Energy became the main theme in organizing the principles of physical research, it was responsible for linking the other studies of motion, light, heat, electricity and magnetism. After this discovery, the very science of Physics was redefined to be the reduction of all other phenomena about reality – reducing it to Mechanics. [Source: Harman 1982a, p. 158] Only after 1850 did physics become the king of all other sciences, usurping the throne of physical astronomy. [Source: Cannon 1978, p.2]. The energy was the reason. And it still is!

Just as an afterthought, below are the various types of energy

Light energy
Sound energy
Solar energy
Nuclear energy
Elastic energy
Gravitational potential energy
kinetic energy
dark energy
internal energy
Hamiltonian energy.

References:

1. 1,
2. 2,
3. [Source: Harman 1982a, p. 158]
4. [Source: Cannon 1978, p.2]