space & time

Matters relating to length and duration in physics and transportation

Homogeneity and isotropy of time

The homogeneity and isotropy of space are well-known. The homogeneity of time is partly known but is confused by an “arrow of time” concept that is not applicable to space and time. The isotropy of time is unknown (and usually denied) also because of confusion with an inapplicable “arrow of time” concept. I previously wrote about the …

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Multiple dimensions of time

This post is another in a series on the duality of space and time. I have emphasized that the basis for space is length and the basis for time is duration. What, then, about direction? Does direction apply to both space and time? Yes, and in the same manner. If someone says, “The hotel is 10 minutes away by …

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Space, time, and arrows

This post is a continuation on the duality of space and time. The basis of space is distance (or length) and the basis of time is duration. It must be emphasized that both distance and duration are scalars, i.e., they have magnitude but no direction. They are not one-dimensional because that would entail direction, represented by …

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Arrow of tense

The arrow of time is a concept developed by Arthur Eddington in 1927. It is an arrow that points from the past through the present into the future. One problem with this concept is that multiple futures are possible; it would have to be a many-headed arrow. Another problem is that it could just as well be pointing from the …

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Duality of space and time

Several dualities of space and time are known, but there are thought to be exceptions for the dimensions of space and the arrow of time. It turns out these are not exceptions; space and time are fully dual. To understand this first note that movement is required for the measurement of time and space, and then compare the various meanings of …

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