What is meant by E= mc²?

Einstein's Big Idea homepage. E = mc2. It's the world's most famous equation, but what does it really mean? "Energy equals mass times the speed of light squared." On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing.

Explanation:

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it means energy is equivalent to the product of the mass of an object and the square of the speed of light.

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.

your answer is c! hope this : )