Final answer:
Einstein's equation E = mc² means that in nuclear reactions, some mass is converted into a significant amount of energy, as observed in processes like nuclear fission and fusion.
Step-by-step explanation:
What does Einstein's famous equation for nuclear energy, E = mc², mean? The correct interpretation of this equation is that some mass is converted into energy in a nuclear reaction. This process can be observed in both nuclear fission and fusion, where a slight difference in mass between the reactants and products results in a significant release of energy. This principle is encapsulated in the equation E = mc², where E stands for energy, m for mass, and c for the speed of light in a vacuum. This equation indicates that a small amount of mass can be converted into a large amount of energy, explaining the powerful output of nuclear reactions such as those in the sun, nuclear power plants, and nuclear weapons.