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Push a box and it resists you. That resistance is its mass. Now try to spin something, and you meet a different kind of stubbornness — one that depends not just on how much…
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Create Free Account →These ten coupled nonlinear partial differential equations describe how matter and energy curve spacetime. The left side represents the geometry of spacetime, while the right side describes the distribution of matter-energy. Einstein published them in 1915, and they remain one of the most profound achievements in theoretical physics.
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