## SXS FAQ

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• Why does E = mc2?

This famous formula was Einstein's most intriguing prediction. Einstein made two assumptions: (1) all motion is relative — you can't be moving unless you're moving relative to something else; (2) everyone measures the same speed of light. With these two assumptions, and a little math, Einstein proved that the only way these two assumptions could be consistent with each other is if the energy E of a resting body with mass m is mc2.

## Inspiration

The fault, dear Brutus,
Is not in our stars,
But in ourselves...

Julius Caesar
(I, ii, 140–141)