Relativity for Ten Year Olds

Here is a short bit of prose from my upcoming book, "Breathing For Clouds." I hope you enjoy it.


“Daddy, what does E=mc(2) mean?”

“Do you want the long answer or the short answer?”

“Both,” she said with a grin. She knows how to wind me up, that one does, and sometimes I think she asks me these questions just to hear me talk.

“The short answer is this: Energy and Mass are two aspects of the same universal stuff, and that famous equation is the relationship between the two, how much of one equals how much of the other, and viceversa.”

“No way.”

“Total way.” I wound up. “Albert Einstein first put the most famous scientific formula in the world on paper in 1905 as one small part of his general theories of relativity. Einstein had discovered, and was trying to explain, an intimate relationship between mass and energy. Energy is the ability to make something happen, mass is the physical weight of a material object. You with me so far?”

“So mass is the car, and energy is the gas to make it go.” The kid is a genius.

“That’s a great way to put it simply, kiddo. Now, it seems logical that energy is energy, and mass is mass, period. But Einstein discovered that energy and mass are two interchangeable aspects of the same thing, which all of the big-brained science guys running around in lab coats; the finest minds at humanities disposal, and they call it mass-energy for simplicity’s sake.”

For the mathematically unchallenged (I’m pleased to say that she got this part easily) if m stands for an amount of mass, and E stands for the equivalent amount of energy, the equation says you can determine that amount simply by multiplying m by a number represented as c(2). The number c(2) is incomprehensibly large – it is the square of the velocity of light – so you can get an enormous amount of energy from a tiny speck of mass.

“Energy equals mass times the square of the speed of light?” At first, she looked pleased, then puzzled. Umm, so….what?”

So what? This is the finest thinking that any human being has ever come up with so far, that’s so what.” I grinned at her, and she grinned right back. “The reason that this is not more in your face and on the news in everyday life (with one huge exception) is that most of the common, daily, energy-producing adventures we experience, such as turning food into energy or burning coal and gasoline are all chemical reactions. In all chemical processes the amount of mass converted to energy is miniscule, I mean tiny, I mean it’s harder to measure it than it is worth.”

At her look I continued. “OK, even if I blow off a stick of dynamite, definitely a chemical reaction, which lets off a lot of energy, enough to blow something up, comes from half a billionth of a gram of matter, twenty trillionths of an ounce of stuff actually converts to make all that BOOM!” Of course, I poked her.

“If you could somehow gather up all the gas and powder and bits of paper that made up the stick of dynamite it would be almost impossible to measure any difference!”

“But that, and almost everything else, is a chemical reaction. Remember the exception I mentioned earlier? That’s nuclear reaction.”

“Bombs and stuff.”

“Well, yeah, but also the fusion reaction that fuels the sun. See, all the mass in the universe exists in atoms, right?” She nodded. “Molecules are made of atoms and elements are made of molecules, and when they are close together it’s a solid, farther apart things are liquid, even farther apart and they are gas, right?” Nod again. "So if all of the matter in existence is in the atom, by converting the mass of the atom directly, you get LOTS more energy, billions of times more. Like in bombs, or the burning of a star.”


“Totally. Now what makes atom bombs the all time champion of matter to energy conversion is the chain reaction. Each atom that rips apart makes two other atoms rip apart and they do it and so on, and so on. So when you get billions of atoms all releasing their energy at once, each one billions of times larger than any chemical reaction, you get a really big BOOM!” She was ready for the poke and parried it easily.

“Not all nuclear reactions are bombs and suns. If you control the conversion rate of the atom to energy flow, you can get steady power, like at a nuclear power plant, so we get electricity for lights, TV, and stuff. That’s what’s in it for you.”

“So Einstein was a big brain.”

“Oh yeah. You know, he had fifteen sets of identical clothes, from the sweaters to the socks, so he never had to worry about what to put on, he just grabbed the next clean set.”

“So Einstein was big geek, like you Dad.”

“That’s the nicest thing you’ve ever said to me.”

©2014 Christopher Reilley
I would love to know what you thought about this piece. Please consider leaving a comment.

Popular Posts