Anonymous

# Could someone please explain the equation e=mc2 in layman terms please?

I've searched the web and have so far found nothing in the way of what you might call a step by step "simple explanation" (if there indeed is one). I was wondering if anyone could explain this equation to me in layman's terms without writing a thesis. If possible could you add any practical applications to which this equation applies to? Thanks.

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• trai
Lv 7

The equation stands for energy (e) equals mass (m) times the speed of light (c) squared (2), or times itself. It basically means that the amount of energy anything is capable of producing is relative to its size (mass) and the limits of physics.

Say I offer you two balls, one bowling ball, and one baseball, and challenge you to pick the one you can throw the furthest. Obviously, you're gonna pick the baseball, because the amount of energy you can exert will have a much greater impact.

Sort of like that, but with a lot of complicated math.

One of the most revolutionary things that einstein did was show that mass and energy are interchangable. E=mc2 says that the Energy E, is the mass in kilograms times the speed of light squared. The energy is in joules. The thing that makes this such a massive amount of energy is the c2. light speed is around 300000 m/s so that squared is a huge number.

So the mass of the keyboard you are typing on, if converted straight into energy would power the world for a lifetime. Obviously we do not know how to convert an object to 100% energy, but massive amounts of energy are involved with even small masses.

How does this relate to our life? Well nuclear reactions produce huge amounts of energy based on this. When hydrogen atoms fuse in a nuclear fusion bomb, the resulting atom (helium) Has a (very) slightly smaller mass than the 2 seperate hydrogens. This difference in mass is converted to 100% energy. The mass difference that creates the massive energy of an atomic bomb is less than the mass of a grain of sand. So as you see, a small amount of mass can create large amounts of energy. This is what powers our sun.

The equation E=mc2 is so elegant and simple, yet so powerful.

It very simply means that anything with mass has potential energy. And there is a formula for determining how much energy can be converted from any mass: Energy = Mass x the speed of light squared.

I'm not certain of the practical examples, except to say that when a particle of mass (an atom) is split (in a nuclear accelerator) it produces huge amounts of energy.

An atomic bomb does the same thing, I think by directing a sphere of high explosives inward on a plutonium atom, thereby breaking apart and releasing its energy in the form of a nuclear explosion. So, a small number of plutonium atoms hold enough energy to destroy an entire city.

If I'm inaccurate here, somebody please correct me.

Hope that helps.

• 4 years ago

The speed of sound is approx 700mph - the speed of light is way faster (light takes approx 8 mins to get from the sun to hear and thats millions and millions of equivalent miles - you could get your calculator out and work out how long sound would take but of course, sound doesn't travel in space due to the vacuum). My understanding of the theory of relativity (and it may not be entirely accurate) is that for a body to achieve the speed of light (or "infinite" speed) you would require "infinite" energy (i.e. all the energy in the universe) and therefore would require infinite mass (i.e. all the mass or matter in the universe). As you can imagine, for a layman such as myself, that is why it is easy to agree with Einstein, that speed of light travel is not possible. Of course, noone told also those light photons that go around! The theory also goes on about: what if you were on a train at the back of the carriage, travelling at the speed of light and then moved to the front, you would in fact be travelling at faster than light speeds (which Mr E stated is impossible). Lastly, Mr E bangs on about if you were on the train doing the Speed of Light (S.O.L.) your perception would be different to someone standing by the side of the "train track" - imagine you are looking at a tree; what you are actually seeing is the light (that took 8 mins to arrive from the sun) bounce of the tree to your eyes, which sends the electric signal to your brain which tells you you're seeing a tree. Apply that example to the bystander watching the S.O.L. train - what can you see when the train is moving at the same speed as the light that needs to bounce off the train to reach your eyes? I think this is why Mr E called it the theory of relativity because of this taking into account of the relative perceptions of the train passenger and the track bystander. As I said, this is my understanding and I could be way wrong - I would recommend you read "A Brief History of Time" by Stephen Hawkings, although I've read it 3 times (last time was about 5 years ago) and I still feel like a caveman grappling with a Nintendo DS! Good luck in your journey towards enlightenment - may the force be with you!

It means that energy and matter have a definite relationship. A certain amount of mass has a discrete amount of energy that can be associated with it. The mass that is lost in fission and fusion reactions (nuclear bombs and nuclear reactors) is converted into pure energy. Since c is the speed of light 3.0 x 10^8 m/s c^2 will be 9.0 x10^16 (a very large number), it means that a little matter can be converted into a lot of energy.

• Gene
Lv 7

Well, first of all, c is the speed of light but the equation has nothing to do with speed. c is just a constant. If you take the value for c and multiply it by itself (c squared) and then multiply it by some mass say in grams,you'll get E which is energy. It says if you annihilate matter of mass m, you get a load of energy because c is a very large number. Practical applications are the sun and all stars, nuclear reactors and unfortunately nuclear weapons. They all convert matter to energy.

• PH
Lv 5

energy is normally formulated in terms of mass and force and time. This was the classical Newtonian physics.

Einstein found that energy can also be expressed in terms of mass and the speed of light quared. Since the speed of light squared is a gigantic number, a gigantic amount of energy can be generated with a tiny tiny amount of mass.

This formula is not very useful in solving practical problems, but the theory behind it, and more complicated formulas based on it ,have revolutionized physics, and led to quantum physics and better atomic theory.

In short the energy that will be created when the total mass of an object is turned into energy is equal to the product of its mass and the speed of light squared.

So, if you would like to know how much energy will be released when you turn anything with mass (ie. some plutonium, or a can of soda) straight into energy (like what happens in a nuclear explosion) you use this formula.

E is Energy

m is mass

c^2 is the speed of light

Simply put, it means energy and mass are interchangeable. Alot of energy is required to make mass (i.e. Amount of mass required multiplied by the speed of light squared).

To create 1kg of mass it requires 3 x 10^16 Joules of Energy - which is a colossal amount.

The applications of E=mc^2 are mainly used in Nuclear Fission and Fusion process, where atoms are either fused together or broken apart and some mass is converted to energy.

This is due to atoms not being the sum of their constituent parts - it takes energy to keep them together, so in each atom their is something called a 'mass-defect'.

Fusion and Fission rely upon this mass-defect to produce energy.