# Matter <-> Energy converions

1. Aug 9, 2004

### Glenn

Matter <--> Energy converions

Is it accurate or inaccurate to think of matter <-->energy conversions to be a "Phase Transition" in the same way that ice to water to steam conversions are examples of phase transitions? And Why?

Thanks,
Glenn

2. Aug 11, 2004

it is accurate. Matter is energy and energy is mass. $$E = mc^2$$

3. Aug 11, 2004

### DW

You missed a coefficient.
$$E = \gamma mc^{2}$$

4. Aug 12, 2004

### pmb_phy

First off it is mass-energy conversion and not matter-energy convertsion. The former has a precise meaning while the later is foggy since "matter" has never been something that one can reasonably quantity unless you replace it with the term "mass".

Second off - It is inaccurate to think of matter-energy conversion as a phase transition. You're talking about two seperate things in mass-energy conversion wherein phase transitions you're talking about the same thing in different states. Mass should never be thought of as frozen energy.

Why? The very meaning of E = mc2 is that an increase in energy can result in an increase in mass and vice versa. There is no reason to think of that as a phase transition. For example: Suppose you blew air into a rubber balloon. Then the balloon would blow up and the surface area o the balloon would increase. Therefore, increase air - increase surface area. Or you can simply say, increase volume - increase surface area. But what you can't say is that the surface is a phase of volume or that volume and surface are two aspects of the same thing.

Pete

Last edited: Aug 12, 2004
5. Aug 12, 2004

### DW

No, it is missing the zero subscript on the energy, but means that mass is rest energy.