Mass–energy equivalence

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The fower-metre taw sculptur o Einstein's 1905 formula E=mc2 at the 2006 Walk o Ideas, Berlin, Germany.

In pheesics, mass–energy equivalence is the concept that the mass o an object or seestem is a measur o its energy content. For instance, addin 25 kilowatt-oors (90 megajoules) o ony form o energy tae ony object increases its mass bi 1 microgram (an, accordinly, its inertia an wicht) even thou no matter haes been addit.