Understanding E=mc^2: Explained in Plain English | Junior's Dilemma

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In summary, E = mc^2 is a well-known and important equation that shows the equivalence between energy and mass, with the speed of light in a vacuum as a crucial factor. This means that a small amount of mass can produce a large amount of energy, as seen in the atomic bomb. The speed of light is significant because it is a constant that relates energy and mass.
  • #1
linux kid
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I have read the wikipedia article on this but my mind just can't seem to comprehend the meaning of this equation. I maybe unconsciously thinking too hard...but I'm still junior...

Someone please explain the meaning to me in plain English. :)

PS: BTW, did this equation lead to the discovery of nuclear technology?
 
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  • #2
I'm not sure what wiki article you read, but here is an easily understood description:

E = mc^2 is an important and well-known equation, which states an equivalence between energy (E) and mass (m), in direct proportion to the square of the speed of light in a vacuum (c2).
http://en.wikipedia.org/wiki/E=mc²

Essentially, this means a small amount of mass, will give us enormous amounts of energy. For example the atomic bomb, which is e = mc^2 in action.
 
  • #3
ranger said:
I'm not sure what wiki article you read, but here is an easily understood description:

E = mc^2 is an important and well-known equation, which states an equivalence between energy (E) and mass (m), in direct proportion to the square of the speed of light in a vacuum (c2).
http://en.wikipedia.org/wiki/E=mc²

Essentially, this means a small amount of mass, will give us enormous amounts of energy. For example the atomic bomb, which is e = mc^2 in action.

But "small" is a relative term. :confused: What about a 3lb mass?

PS: that is the one I read.
 
  • #4
You should have all mass in kg. Why don't you try converting 3lb to kg and plug it in the equations and see what numbers you get. To give you can idea of the scale you are dealing with, the atomic bombs dropped in Japan were 63 TJ (Hiroshima) and 84 TJ (Nagasaki), Encyclopedia Americana. And by todays standards, these are small.
 
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  • #5
I know the equation. I just don't know why/how it works. Why the speed of light?
 
  • #7
Because that's how much energy you get out of each bit of mass. So if you convert 1 kg of mass (= 2.2 lbs) to energy... you'll get
1 kg * c^2 of energy.

That's 1 kg * (3.0*10^8 m/s)^2 = 9 * 10^16 J of energy, or 9000 TJ. Compare that with those bombs.

To put that into perspective: most humans weigh more than 50 kg.

What e=mc^2 means is that mass is a form of energy and energy is a form of mass. They're different forms of the same thing.

Are you looking for how that equation was obtained? If so, here's the one from the Wikipedia article. I think we did it a simpler way in class, but it's in my pencil-and-paper physics notes.

http://en.wikipedia.org/wiki/E=mc2#Derivation
 

Related to Understanding E=mc^2: Explained in Plain English | Junior's Dilemma

1. What does E=mc^2 mean?

E=mc^2 is the famous equation proposed by Albert Einstein in his theory of special relativity. It explains the relationship between energy (E), mass (m), and the speed of light (c).

2. How did Einstein come up with E=mc^2?

Einstein derived this equation by combining the principles of special relativity, which states that the laws of physics are the same for all observers in uniform motion, and the principle of mass-energy equivalence, which states that mass and energy are two forms of the same thing.

3. What does each variable in E=mc^2 represent?

The variable E represents energy, measured in joules (J). The variable m represents mass, measured in kilograms (kg). The variable c represents the speed of light, which is approximately 299,792,458 meters per second (m/s).

4. How does E=mc^2 relate to nuclear energy?

E=mc^2 explains the principle of mass-energy equivalence, which is the basis for nuclear energy. In nuclear reactions, a small amount of mass is converted into a large amount of energy, as predicted by this equation.

5. Can E=mc^2 be applied to everyday situations?

Yes, E=mc^2 can be applied to everyday situations, such as the energy released by the sun, the energy produced by our bodies, and the energy used in nuclear power plants. However, the effects of this equation are most noticeable at high speeds or in extreme conditions.

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