Sunday Science: E=mc^2

It's the world's most famous equation. It's E = mc².

But what does this mean?

It means that energy (E) is equal to mass (m) multiplied by the speed of light (c), squared.

What does it really mean?

It means that energy and mass (or matter) are interchangeable. Energy and matter are just different forms of the same thing. And, under the right conditions, energy can become matter and matter can become energy.

Under the right conditions, the energy Flash uses to run to Batman's pool party could turn into a chunk of matter - like a rubber ring.

We don't see them that way. Flash's energy and the rubber ring are completely different to us. 

​But we're wrong - energy and matter are two forms of the same thing.

The little c

So, where does the speed of light or "c" some in?

Remember when I said that energy can become matter and vice versa under certain conditions? One of those conditions is that when you convert a rubber ring or any other piece of matter to pure energy, this energy is moving at the speed of light.

This is because energy in its purest form is electromagnetic radiation (for example, the UV light filling your room) and electromagnetic radiation travels at the speed of light.

Why is the speed of light squared?

The speed of light is squared (multiplied by itself - so c x c) because of the nature of energy.

When the Flash is moving at two times the speed of Batman, Flash doesn't have two times the energy of Batman. He has four times the energy of Batman (2 x 2 =4). 

​Or, if the Flash is moving at four times the speed of Ironman, Flash doesn't have four times the energy of Ironman. He has 16 times the energy of Ironman (4 x 4 =16).

In other words, that figure is squared.

​It's worth bearing in mind that the speed of light squared is a huge number. It's 90,000,000,000,000,000.

Lego Flash only weighs 4g. But if you could turn every atom in Flash into pure energy, that would equal 360,000,000,000,000J (where J is a unit of energy called Joules).

As a frame of reference, the Hiroshima bomb exploded with an energy of about 63,000,000,000,000J.

In other words, Lego Flash has more energy than five Hiroshima atomic bombs.

No wonder he moves so quick.

Extra reading and watching

If you want to find out more about turning matter into energy and vice versa, this article from Forbes covers the basics.

Here's an excellent video from Epic Science covering that famous equation (and a great example involving Dr. Seuss)

What is Sunday Science?

Hello. I’m the freelance writer who gets tech. I have two degrees in Physics and, during my studies, I became increasingly frustrated with the complicated language used to describe some outstanding scientific principles. Language should aid our understanding — in science, it often feels like a barrier.
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So, I want to simplify these science sayings and this blog series “Sunday Science” gives a quick, no-nonsense definition of the complex-sounding scientific terms you often hear, but may not completely understand. 

If there’s a scientific term or topic you’d like me to tackle in my next post, fire an email to [email protected] or leave a comment below. If you want to sign up to our weekly newsletter, click here.

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