|Definition: determination of the use of linguistic signs (words, symbols, connectives) for non-linguistic or linguistic objects. New definitions are not supposed to be creative, that is, they are to be derived from the use of the signs already employed. See also definability, conservativity, systems, theories, models, reference systems, context definition, explicit defnition, implicit definition.|
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Laws Definition//Meaning/Laws of Nature/Feynman: it is generally believed that laws of nature represent some kind of genuine knowledge. What does that mean?
What does F = ma mean? What is the meaning of force, mass, acceleration?
We can feel mass intuitively and we can define acceleration.
Definition e.g. "when a body accelerates, a force acts upon it".
Definitions/Feynman: such definitions cannot be the content of physics, because they are circular. Nevertheless, the Newtonian statement above appears to be the most precise definition of force.
But it is completely pointless, because no predictions can be made from it. (From no definition!).
The way in which objects behave is completely independent of the choice of definitions.
For example, we define something new:
Def "Gorce"/Fictitious Force/Terminology/Feynman: temporal change of position with a new law: everything stands still, except when a gorce is effective.
This would be analogous to the old force and would not contain any new information. (But: see below...)
Forces/Laws of Nature/Newtonian Laws/Theory/Feynman: their true content is that the force, in addition to the law F = ma, should have some independent properties.
But these specific properties have not not been described by Newton, nor by anyone else, and therefore F = ma is an incomplete law. It implies that we will find some simple properties when studying the forces. It is an indication that forces are simple. This is a good program for analyzing nature.
Laws/Laws of Nature/Theory/Feynman: if nothing but gravitation existed, then the combination of the law of gravitation and the law of force would be a complete theory.
We need further properties of the force: e.g. if no physical object is present, the force equals zero, if it is different from zero, and something is found in the neighborhood, then that must be the cause.
That is the difference to "gorce" (see above).
That power has a material origin is one of its most important properties, and that is not only a definition.
Definition/Law/Feynman: e.g. second Newtonian Law. Action equals response: that is not quite precise. If it were a definition, we would have to say that it is always precise, but it is not!
Feynman: every simple thought is approximated. E.g. chair: superposition of atoms, constant decrease and increase, depending on the accuracy of the measurement.
Mathematical definitions can never work in the real world.
Empiricism/Definition/Mach/Feynman: you can only define what you can measure.
FeynmanVsMach: whether a thing is measurable or not cannot be decided a priori solely by reasoning! It can only be decided in experiments.
((s) VsFeynman: but doesn't it need to be defined before the experiment?)
Feynman: it is clear that absolute speed has no meaning. Whether or not it can be defined is the same as the problem, whether you can prove if you are moving or not!
Definition/Temperature/Physics/Chemistry/Feynman: two different definitions:
1) Assuming the kinetic energy of the molecules is proportional to the temperature, this assumption defines a temperature scale:
"Scale of the ideal gas".
We call the correspondingly measured temperatures
2) Other temperature definition: independent of any substance:
"Great thermodynamic absolute temperature".
Vom Wesen physikalischer Gesetze München 1993
Vorlesungen über Physik I München 2001