A Scientific Discussion

Matter can be created or destroyed, matter/anti-matter annihilation gives a fairly definite answer.

But there are cases where it's slightly more difficult to answer. Nuclear fission/fusion is one example. Assume you were to take 2 protons and 2 neutrons, and mesure their mass, for this example let's say each particle weighs 1 (no unit), so the total mass is 4. Now, fuse them together to form an helium nucleus. Surely you'd expect that the nucleus would weigh 4, but it won't be the case. The nucleus will weigh slightly less than 4, with the difference between 4 and the actual mass being tranformed in energy in accordance to E=mc^2. But the number of particles is still the same! The only thing that has changed is the mass. Can we say that matter was destroyed in this case?

The answer is essentially a matter (pun intended) of what definition of matter you use, and it's pretty much the same for a number of other problems. Creation of particle/antiparticle pairs? Well, it depends on whether or not you consider said particles to be matter or not. Creation then destruction of particles through the Heisenberg uncertainty principle when applied to time and energy? Same thing, it depends of what you consider matter to be.

Jam it back in, in the dark.

Originally Posted by Cetra

Nope, matter/anti-matter annihilation is just the process of turning all matter of a system into energy. Nothing is being removed from existence. It's just a transfer of a matter state to an energy state.

True, and I never said such wasn't the case. I said that matter was destroyed. Whatever it becomes afterwards doesn't make it any less true; that matter has stopped to exist as matter.

Originally Posted by Cetra

Nope, some of the matter was converted into energy. It wasn't lost. Under the right conditions that energy can be reclaimed into matter again thus that matter hasn't been destroyed. Its state has only been changed. This is the Law of Conservation of Matter and Energy. I think some of you are reading way too far into what the law states. The sum of energy and matter of what you put into something results in a equal matter and energy sum.

Agreed again, but I still have the same objection, matter as matter has ceased to exist. That it became energy is none of my concern. Using the definition you give a bit later, that everything is either matter or energy, makes it fairly easy to see. If it's been transformed into energy, then it's not matter anymore.

My initial point was mostly that there are different definitions of matter depending on the discipline. In chemistry, matter will be mostly defined as atoms and their constituent particles, nucleons and electrons. If you fuse two atoms together, then from that definition no matter is lost, while mass did disappear. Whether or not matter was lost, or converted, or only mass as a concept distinct from matter, becomes an issue of what definition you use.

Originally Posted by Cetra

If it is not matter, its energy. If it is not energy it is matter. These are the only two states of existence in our Universe. There are no in between or ambiguous states. There is only one single definition of matter. If your 'object' doesn't fall under the matter category, then it is in an energy state.

Heisenberg uncertainty principle also deals with the wave/matter duality of electrons and the fact that we have no measurable way to detect the moment of electrons. We can only guess their probable position based on observable/measurable events. It has nothing to do with the creation and destruction of particles.

The Heisenberg uncertainty principle can be generalised so that it applies to time and energy. In a somewhat simplified way, it means you cannot be certain of the energy at a certain point in space at a certain time, or in mathematical terms, if I remember correctly, DEDt >= h (where D is a capital delta, E is energy, t is time and h is Planck's constant). What this means is that the principle of energy conservation can be violated temporarily, as long as this is done in an interval shorter than what the Heisenberg uncertainty principle allows for a particular energy level (the higher the energy, the shorter said energy can be "borrowed"). That energy, in turn, can be converted into a particle, temporarily.

These are not particles we can detect per se, as they're extremely short-lived, but we can actually detect the traces. They're usually called "resonance particles".

There's nowhere I can't reach.

Originally Posted by Cetra

Ah I think I understand the underlying problem here. It's like saying when ice metals and becomes water, the ice no longer exists. But we know this isn't true. Rather the ice exists just in a different matter state. Matter and energy share a similar concept. The problem is the Law of Conservation of Matter and Energy isn't exactly saying matter cannot be created or destroyed. The definition we get in most text books is just a simplification of the concept.

A better way to express the Law is to say something like "The sum of what you put in will always equal the sum of what you get." It's saying that in a perfectly closed reaction nothing is ever gained or lost, eg. created or destroyed.

Does that make sense?

Oh, I already understand the theory perfectly, that's no issue.

I think the problem was mostly one of semantics or definition. Science doesn't care much about what definition you give a word, as long as everyone has the same. Perhaps this wasn't the case here. I wasn't writing a lab report or anything like that, so I just used the words with the everyday definition closest to what I wanted to say, and in not so rigorous ways. I suppose it can cause misunderstandings. Mea culpa.

This thing is sticky, and I don't like it. I don't appreciate it.