# Question about Energy Interactions.

1. Jul 30, 2014

### neomahakala108

is it true that:

'as energies interact, they change properties, possibly creating massive matter in the process or vice versa'

?

2. Jul 31, 2014

### Matterwave

Where did you read this? This sentence doesn't make sense as stated.

3. Jul 31, 2014

### neomahakala108

it's deduction of mine, i wanted to verify it with experts for truth.

4. Jul 31, 2014

### Matterwave

Ok, then my opinion is that it doesn't make sense as stated.

5. Jul 31, 2014

### neomahakala108

how it would make sense then?

6. Jul 31, 2014

### Matterwave

As I don't know what you're trying to say, I probably can't fix the statement. I can give a possible alternative.

There is a small probability, when two photons of sufficient energy interact, that they can undergo reverse annihilation and create an electron positron pair.

7. Jul 31, 2014

### neomahakala108

thanks for that.

8. Jul 31, 2014

### Staff: Mentor

No, because energy doesn't interact. It is not a "thing". It is a quantity that objects possess.

9. Jul 31, 2014

### neomahakala108

thanks for that.

however,

if matter is form of energy...

this seems contradicting with idea of energy particles.

----

1. 'matter is form of energy'

2. 'energy doesn't interact. energy is not a "thing". it is a quantity that objects possess'.

two above mentions seems to contradict each other from my perspective, even if i can see the difference between 'form of energy' and 'energy'.

Last edited: Jul 31, 2014
10. Jul 31, 2014

### bhobba

It is

That is true as well. But in no way contradicts the first thing.

A modern understanding of energy may help:
http://physwiki.ucdavis.edu/Classic..._Mass_and_Energy/Noether's_Theorem_for_Energy

Without going into the details, because it's highly mathematical, not only does energy conservation follow from Noether's beautiful theorem, but that matter is a form of energy as well.

But so no one thinks I am wimping out here is an outline of the reasoning.

First for Noether's Theorem you need a Lagrangian. It must be relativistically invariant. The only reasonable one is a constant A times an infinitesimal amount of proper time or A dtau. Taking the classical limit, in units with the speed of light C=1, we find, interestingly, A = m - the mass of the particle. If you chug through the math, and apply Noether's theorem, it turns out the quantity that it says is conversed, because of time invariance, which by definition is energy, is Einsteins famous E=M (c squared is missing because we have C=1 for simplicity).

You can find the full detail in Landau - Classical Theory Of Fields - Chapter 2.

But this is just so you know I am not wimping out - the detail is out there in standard textbooks.

So mass is just a great big hunk of energy, and is conserved.

Thanks
Bill

Last edited: Jul 31, 2014
11. Jul 31, 2014

### neomahakala108

but is it true that energies do not interact?

if mass is energy form, and two mass particles collide, one breaking another... then somehow they did interact, and changed spread in space of mass (E=M).

sorry for my stupidity and ignorance, trying to learn.

12. Jul 31, 2014

### Staff: Mentor

I'd say that matter and fields possesses energy, but they are not energy itself. It is the collision of matter or excitations of fields that produce new matter, not the collision of energy. Saying energy interacts is like saying momentum or velocity interacts and produces new things.

13. Jul 31, 2014

### neomahakala108

i read that from a certain perspective, particle of light, a photon, has a size, about half a fermi: 0.5·10-15m, 'since you start to feel it pushing back against you if you go to close', which happens at about that size.

this is also interaction.

---

also:

'when two electric charges interact, the presence of one causes a force to act on the other and as a result both start moving...'

it's quote / paraphrase from book about Quantum Physics, with references to Classical Physics for more complete understanding

Last edited: Jul 31, 2014
14. Jul 31, 2014

### bhobba

Although mass is a dirty great big hunk of energy, you cant draw the conclusion that's the only property it has and when things interact its energy that interacts.

Matter has properties of mass, energy, and other things (such as say charge and spin), but that's not to say those properties are what interacts.

Our deepest theory, Quantum Field Theory, describes interactions as the exchange of virtual particles, but what's going on is subtle and not amenable to the type analysis implied by the quotes you have been giving:
http://profmattstrassler.com/articl...ysics-basics/virtual-particles-what-are-they/

Thanks
Bill

Last edited: Jul 31, 2014
15. Jul 31, 2014

### neomahakala108

thanks for that.

and thanks for that...

this changed my Mind-State and a way of thinking already.