Everyone has seen this equation, and everyone knows this is Einstein's famous "mass equals energy" equation.

But what does it mean exactly? As always, its best to see it in an example. Because Einstein's work was with light and energy, the best example is the Sun. Our Sun produces energy through fusion - the combining of 4 hydrogen atoms to make a helium atom plus a few extra parts. When comparing the mass of 4 hydrogen atoms to a helium atom, there is some mass loss:

Keep in mind that this is EACH reaction. In the Sun, there are millions of these reactions occurring.

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