E = mc2

 

Einstein's Big Idea

1. On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing.

Einstein Revealed

It's difficult to separate the enormous legacy of E = mc² from Einstein's legacy as a whole. 

 

After all, the equation grew directly out of Einstein's work on special relativity, which is a subset of what most consider his greatest achievement, the theory of general relativity. But I'm going to give it a try anyway.

The equation explained

1. First, though, a capsule explanation of "energy equals mass times the speed of light squared" might be helpful. 
2.  
3. On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing. 
4.  
5. Under the right conditions, energy can become mass, and vice versa. We humans don't see them that way—how can a beam of light and a walnut, say, be different forms of the same thing?—but Nature does.
6.  
7. So why would you have to multiply the mass of that walnut by the speed of light to determine how much energy is bound up inside it? 
8.  
9. The reason is that whenever you convert part of a walnut or any other piece of matter to pure energy, the resulting energy is by definition moving at the speed of light. 
10.  
11. Pure energy is electromagnetic radiation—whether light or X-rays or whatever—and electromagnetic radiation travels at a constant speed of roughly 670,000,000 miles per hour.

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