# Understood this equation e=mc2

1. Jul 4, 2009

### Valo130

I think i have understood this equation ( don`t be to hard on me, only 15 and have just started to read physics ).

As i understand it says the following :

Energy can be turned into mass, and mass can be turned into energy.
It also says how much energy you get if you turn mass into energy.

Is this right?

2. Jul 4, 2009

### Alewhey

Re: e=mc2

Essentially yes, but it might be better to think of it as saying that mass *is* energy - that is, mass is one manifestation of energy, just like heat or light, and can in principle be turned into other types of energy.

This is clearer if we define c=1 (yes, we can do that!), leaving simply E = m.

3. Jul 4, 2009

### Valo130

Re: e=mc2

I understand how you can do matter into energi, when it meets anti-matter and... explodes.
But how do you do energy into matter?

4. Jul 4, 2009

### Alewhey

Re: e=mc2

One example is nuclear fusion when creating elements heavier than iron. I'm not sure of the precise process (no doubt it is very complicated) but basically two lighter atom smash into each other at immense energies and fuse together, putting some of the energy into mass. This process only occurs in supernova.

5. Jul 4, 2009

### Staff: Mentor

Re: e=mc2

A photon above a certain energy threshold can create an electron-positron pair when it collides with something.