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concepts that are fundamental to the special theory of relativity

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events, clocks, and observers

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this concept is almost trivial in a sense

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part of Einstein's genius was to look at these concepts that many people took for granted

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what does it mean to observe something?

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where something happened

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when something happened

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e.g. a flash occurring at a specific place and time

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three dimensional coordinate system

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x, y, z axis

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any given event would have an x,y,z coordinate

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measuring system

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an event happens at x,y,z

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but we need a time as well

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so we need a system of time keeping

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so time is the fourth dimension

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not really as profound as it seems to be

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three spacial coordinates and time as well

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we assume we have an origin, e.g. (0,0,0,0)

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we say this is the observer at time 0

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gets to the question how we measure time

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there is a problem with that, which is that time does not move at infinite speed, but a finite speed

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light from the flash takes a while to get to the origin where the observer is

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you could figure out how far away the light is by how long it took to get to the observer

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we could also put clocks at all points

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the "photo clock principle"

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every single point in time has a clock associated with it

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we'll assume when the flash goes off, there is a photo taken recording the x/y/z/t coordinates

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a lattice of clocks

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a grid of clocks

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issue: there is an infinite number of points

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resolution: depending on the accuracy we want, we add or subtract the number of clocks