# How many conservation laws ?

1. May 8, 2011

### bksree

Hi
How many conservation laws are there ?
1. Conservation of energy
2. " " momentum
3. " mass
4. " charge
????

TIA

2. May 8, 2011

### Curl

energy
momentum
angular momentum
charge
gravity
+ others I can't think of right now

mass conservation isn't really true

3. May 8, 2011

### I like Serena

color charge
weak isospin
probability density
CPT symmetry (combining charge, parity and time conjugation)
Lorentz symmetry

(ripped from http://en.wikipedia.org/wiki/Conservation_law)

4. May 8, 2011

### Staff: Mentor

Yeah, It all depends on what you mean by "mass". Converting electrons-positrons to gamma rays removes the "mass" and turns it into energy or momentum or whatever.

5. May 8, 2011

Staff Emeritus
I don't know what "conservation of gravity" even means. As for weak isospin, it is certainly not conserved, although it's third component is.

There is no answer to this question. What is conserved and what is not depends on the state you are looking at: an object in a central force orbit always has angular momentum conserved, but in a 1/r potential, it also has another quantity conserved: the Runge-Lenz vector.

Additionally, if x and y are conserved, x + ay is conserved as well, for all values of a. So if there are two, there are an infinite number.

6. May 8, 2011

### Staff: Mentor

From wikipedia, it lists a few things seperated into "exact laws" and "approximate laws".

7. May 8, 2011

### 1MileCrash

Would it then be correct to say that a conservation of matter doesn't exist, but a conservation of mass does, seeing as energy does possess mass?

8. May 8, 2011

### Staff: Mentor

As wikipedia put it, I'd call it Conservation of mass-energy.

9. May 9, 2011

### samuelarnold

The concept of mass–energy equivalence connects the concepts of conservation of mass and conservation of energy, which continue to hold separately. The theory of relativity allows particles which have rest mass to be converted to other forms of mass which require motion, such as kinetic energy, heat, or light.From WkiPedia.