If mass and energy can be changed from one to the other?

Question

If mass and energy can be changed from one to the other, what guarantees that the total amount of matter in the universe remains constant, or that the total amount of energy remains constant?

Answer 1

Energy is conserved, but not mass since mass is actually *a form* of potential energy that can be converted into other forms, like kinetic energy, via nuclear or even chemical reactions.

Answer 2

Mass is a form of energy. Before they realized this was the case, people said mass was constant and energy was constant. There are people who still say this (sometimes for simplicity, sometimes they really don't know), but it's not true. Energy is constant. Mass is a very high desnity form of energy. Just like how energy can be mechanic, electric, or thermal (to name a few), it can also be mass. Therefore, the amount of mass can change as it's converted to and from other forms of energy. But the total amount of energy is always constant when you factor in every kind of energy including mass.

Answer 3

Boy, there isn't any guaranty of const. mass or energy.

But according to E=mc^2 MASS ENERGY of universe is constant. B'coz mass can change into energy and vice versa.

okeay..

Answer 4

yes. the conservation law holds for ()mass+energy)