Question

Which statement correctly describes mass-energy equivalence?

All energy in the universe will be converted to an equivalent amount of mass.
Mass can decrease in nuclear changes without the production of energy.
All energy in the universe is a result of mass being converted into energy.
A large amount of mass is equivalent to a small amount of energy.

Answer 1

None of the four statements is correct.

Mass–energy equivalence (E = mc²) means that mass and energy are interchangeable and that a small amount of mass corresponds to a very large amount of energy (because c² is very large). Brief notes on the options:

- "All energy ... will be converted to an equivalent amount of mass." — False: mass and energy can convert into each other, but there is no general rule that all energy must become mass.
- "Mass can decrease in nuclear changes without the production of energy." — False: the decrease in mass (mass defect) in nuclear reactions is precisely associated with the release of energy.
- "All energy ... is a result of mass being converted into energy." — False: many forms of energy (e.g., kinetic, potential, fields, radiation) are not necessarily produced by converting rest mass.
- "A large amount of mass is equivalent to a small amount of energy." — False and reversed: a small amount of mass can be equivalent to a large amount of energy.