# Are matter and energy interchangeable?

1. Mar 4, 2015

### kylemoely

i just read something that said they are through the mass-energy equivalence formula. The original quote was
now i wouldnt think matter and energy are interchangeable because energy doesnt take up space and i believe thats how matter is defined.

Granted this quote was from Yahoo answers so some stuff on there is good and some stuff is not.

2. Mar 4, 2015

### Staff: Mentor

This is like saying that water, ice, and steam are "interchangeable". They're interestingly different (I can't walk on water, drink ice, or pour steam) even though they're all forms of good old $H_2O$.

3. Mar 4, 2015

### Staff: Mentor

The m in that equation stands for "mass" not "matter". Mass and energy are both different properties that describe matter, and those properties are related. You do not exchange mass for energy, a system that has mass also has energy.

4. Mar 4, 2015

### Pierce610

According to Einstein in a relativistic particle the mass is a misure for its amount of the energy; if the particle loose energy, for example emitting a photon, its mass decreases by E/c^2.

5. Mar 4, 2015

### my2cts

Mass is just the energy in the rest frame of an object. The mass of an atomic nucleus or an atom is smaller than the sum of constituent masses. The difference consists of the potential energy due to mutual attraction and kinetic energy of the constituent particles. This energy will appear as heat or radiation upon formation of the composite object, and thus mass is transformed into (a different form of) energy. In this sense mass and energy are interchangeable.