belial wrote:
Bad Wigins wrote:
What things are is what physics is about. Isn't it? Is that somehow offensive?
So if you say a thing is a "particle," it might as well be a very tiny rock, for all you mean, because that's all the concept conveys ontologically. "Energy" might as well be fire. Something with kinetic energy is burning rubber. Something with thermal energy is hot, that's fire. A wave in space-time is a burning nothing.
Modern physics is a doomed creation of overspecialization in academics. Study philosophy - metaphysics - before physics or you'll have hopeless tunnel vision.
Labels, like "particle," have no inherent meaning (a rose by any other name). Structure is provided by other properties, like relations and functions. For instance, a set is an object defined by the member-of relation such that an element a is in a set X if (a,X) is in the member-of relation. A set in which a, b, and c are in the member-of relation may be denoted by the label {a,b,c}. This is just a label, but this label may be used in mathematical equations that impose some structure, e.g., the set denoted by {a,b,c} is a subset of the set denoted by {a,b,c,d}, i.e., ({a,b,c},{a,b,c,d}) is in the subset relation.
Generally, in physics, a set of functions are provided that map inputs to outputs, e.g., given some initial state, output a final state. This is what we call "prediction", that is, it makes a prediction about what will be observed given some observed initial input.
Because you seem hopelessly confused, I will take a bit of time to rumminate further on the philosophy of science in the context of the above. What use is prediction? This is a necessary component of scientific inquiry. Suppose we have a set of hypotheses A, and suppose exactly one of the hypotheses in this set is true and the remaining are false. To remove elements (hypotheses) from A, we perform experiments that generate observations and remove any elements that are not compatible (an incorrect prediction). This is called falsification. Typically, A is infinite, or at the very least has more than one element, and we often like to impose a partial order on the elements in A s.t. if a,b in A and a < b, we prefer hypothesis a to hypothesis b even though both are compatible with all previous observations. This order is where notions like Occam's razor come into play, which is an informal way to order the elements, but more mathematically rigorous orderings may be based on non-computable measures like Kolmogorov complexity for which Occam's razor is a crude though useful approximation.
Back to physics. In quantum mechanics, there are no distinct objects, only continuous fields as described by Schrodinger's partial differential equation. For all but the most trivial systems, the equations are intractable, although this is changing as we develop more efficient approximate algorithms and better hardware. Instead, we often resort to more classical mathematical structures that are easier to work with in which abstractions like distinct objects are available.