# How does E=mc² work?

1. Aug 20, 2015

### nicholas0211510

I know the basics of E=mc² and it being mass energy, but someone told me its also used for projectiles and explosions how does it corrolate with destructive power ?

2. Aug 20, 2015

### HallsofIvy

Staff Emeritus
If you know what "$E= mc^2$" means then you should be able to work that out. It does not really have anything to do with "projectiles" since that does not change mass into energy. In a nuclear explosion some mass (typically a tiny fraction of the total mass) is converted to energy. Now what that is in "destructive energy" depends on exactly what you mean by "destructive energy". Not all of that energy "destroys" things.

3. Aug 20, 2015

### Isaac0427

e=mc^2 wasn't the only thing behind atomic weaponry, if that is what your asking. The relationship between mass and energy just helped scientists develop the atom bombs. Check out this website: http://www.einstein-online.info/spotlights/atombombe

4. Aug 20, 2015

### nicholas0211510

Ah that claifys things, and sorry I didn't specify what I ment in destruction, our convo was talking about a astroid striking earth, he said E=mc² is what is used used to measure it , it sounded suspicious so I came here to ask some more experienced people

5. Aug 20, 2015

### Isaac0427

I'm not sure how that works. Sorry.

6. Aug 20, 2015

### nicholas0211510

alright, I guess I'll just do some reading on line

Appreciate the help

7. Aug 20, 2015

### jbriggs444

E=mc2 is not what is used to measure the destructive power of an asteroid striking earth. The fellow who said it was... was mistaken.

If one wanted to determine the energy released in an impact with such an asteroid, E=1/2mv2 would be the appropriate measure.

8. Aug 21, 2015

### CWatters

The problem is the difficulty of converting mass to energy. Simply colliding an asteroid into a planet isn't going to do it. As others have said, that's not the right kind of interaction.

In an atomic explosion some of the mass is converted to energy. Google found references that suggest for the Little Boy bomb only about 600mg of 64kg was turned into energy. That's a very low percentage of the total mass but a heck of a lot of energy.