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Ontology/Feynman: The "reality" of an object is a little bigger (roughly and intuitively spoken) than its "width" and "depth", because they depend on how we look at it.
Relativity theory: our brain has never had any experiences with speed close to c so that we could not integrate any experience, of the type that time and space are of the same kind.
It is as if we could always stand in a position and not turn in the other direction. If we could, we would see a little of the other man's time. We would "look back" a little.
Space-Time/Feynman: In a world where space and time are "mixed" (this is actually our world, seen close to speed of light), objects are more like a kind of "blob", viewed from different perspectives when we move at different speeds.
Measuring/Geometry/Feynman: there are properties which are independent of the particular type of measurement. For example, the distance between two points in a rotated coordinate system when one of the two points is in the origin.
The square of the distance is x² + y² + z².
What about space-time?
Space-Time/Geometry/Feynman: it is easy to show that there is also an invariance here:
The combination c²t² x² y² z² is the same before and after the transformation:
c²t' ² x' ² y' ² z' ² = c²t² x² y² z². ( 17.3?)
Ontology/Feynman: this quantity is something that is "real" like the distance in a sense. It is called the Def "interval" between two spacetime points.
Existence/Ontology/Feynman: if the polarization changes faster than we can measure it, we call it light. This is unpolarized, because all polarization effects are eliminated.
Vom Wesen physikalischer Gesetze München 1993
Vorlesungen über Physik I München 2001