physics

Space-time duality

Space and time are dual concepts. They are complementary to one another as an inverse binary symmetry. They go together as space with time in classical physics or time with space or spacetime as in relativistic physics. Parallel terms: Space Time 3D space +reference time 3D time + reference length vector space + scalar time […]

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Terms for rates of motion

The scalar space of a motion is the arc length along the curve it traces out. The scalar time of a motion is the travel time along the route it traces out. The time rate is “The rate at which something takes place over time.” The space rate is the rate at which something takes

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Odologes

An odologe (o′∙do∙loje) is a constant-rate length-measuring device synstancialized with a common waypoint. It is a new coinage from odo(s), path + (horo)loge, clock. In short, it is a clock that shows length instead of time. The simplest odologe takes time from a clock and multiplies it by a conversion speed to produce a length.

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Why space and time are not different

Many differences are proposed between space and time. This post briefly indicates how all of them are a matter of convention, and so not real. For details, consult posts on this blog. (1) There are three space dimensions but only one time dimension. Directionality can be associated with either length or time (duration). 3D time

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Ten meanings of time

Carlo Rovelli’s “Analysis of the Distinct Meanings of the Notion of “Time” in Different Physical Theories” (Il Nuovo Cimento B, Jan 1995, Vol 110, No 1, pp 81–93) describes ten distinct versions of the concept of time, which he arranges hierarchically. Here are excerpts from his article: We find ten distinct versions of the concept

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Space and time involution

J. C. C. McKinsey, A. C. Sugar and P. Suppes (hereafter MSS) wrote “Axiomatic foundations of classical particle mechanics”, (Journal of Rational Mechanics and Analysis, v.2 (1953) p.253-272), which is also described in Suppes’ Introduction to Logic (Van Nostrand, New York, 1957), pp.291-322 (see here). It is only a partial axiomatization of Newtonian mechanics but is

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Centers of motion

Bodies with space-time orbit by gravitation around their barycenter, the center of mass. The word barycenter is from the Greek βαρύς, heavy + κέντρον, center. The barycenter is one of the foci of the elliptical orbit of each body. For the two-body case let m and M be the two masses, and let r and

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Observers and travelers again

This post continues the ones here and here. Realism considers what is perceived with full consciousness as reality. Apperception and reality correspond to each other. The role of theory is to clarify this correspondence, not to deny it. So realists understand observation to be correct, not to be altered by theory. Anti-realism considers what is

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Speed vs. velocity

For some background, see here and here. Velocity is defined as: “The time rate of change of position of a body; it is a vector quantity having direction as well as magnitude.” Speed is defined as: “The time rate of change of position of a body without regard to direction; in other words, the magnitude

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