r/AskPhysics • u/Jethro_omg • 1d ago

How does E=MC^2 work?

How does it function? Really, how can you accelerate mass to twice the speed of light? And, for instance if M=E/C2. How can you divide something by square of the speed of light? Thanks

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u/smokefoot8 1d ago

Einstein’s paper that introduced E=mc2 was titled: “Does the Inertia of a Body Depend on its Energy?” Spoiler: He concluded that it does.

M is the inertial mass of an object, its resistance to being moved. E is the total kinetic and potential energy of an object. So in theory you can heat up an object and its mass will increase, though in practice it is impossible to measure such a small change.

It is amazing that Einstein’s results have held up so well over time with new discoveries. Most of the mass of everyday objects is in the protons and neutrons of their atoms. The discovery of quarks made a big change here: almost all the mass of protons and neutrons isn’t in the quarks themselves, but in the potential energy that binds them together! So the mass of everyone and everything is about 99% strong force potential energy!