an update of https://www.geogebra.org/m/HYD7hB9v#material/UBXdQaz4[br]( from Relativity on Rotated Graph Paper (robphy) - MAA2016 )

[i][a 2019 update of https://www.geogebra.org/m/HYD7hB9v#material/UBXdQaz4 ][br][br]This is the fourth of six GeoGebra files [br](from my GeoGebra book [url=https://www.geogebra.org/m/HYD7hB9v#]Relativity on Rotated Graph Paper (robphy) - MAA2016[/url] ) [br]that were part of my MAA MathFest 2016 talk[br]"Introducing Spacetime Geometry: Relativity on Rotated Graph Paper".[br][url=http://www.maa.org/meetings/mathfest/program-details/2016/themed-contributed-paper-sessions]http://www.maa.org/meetings/mathfest/program-details/2016/themed-contributed-paper-sessions[/url][br][br][/i][i]It describes aspects of my paper “Relativity on Rotated Graph Paper”, Am. J. Phys. 84, 344 (2016); [url=http://dx.doi.org/10.1119/1.4943251]http://dx.doi.org/10.1119/1.4943251[/url]. [br]An informal introduction is presented at[br][url=https://www.physicsforums.com/insights/relativity-rotated-graph-paper/]https://www.physicsforums.com/insights/relativity-rotated-graph-paper/[/url][/i][br][br][br]Here it is already assumed that light travels at speed c, independent of the speed of the source. [With our choice of units, this means that all light-signals are drawn at 45-degrees.][br][br]The Principle of Relativity requires that if inertial observers Alice and Bob conduct identical experiments on each other, the outcomes should not allow them to be distinguished.[br]So, if Alice and Bob each send a light-signal when their own clock reads 2 ticks,[br]we expect that the "clock readings when they receive the other's light-signal" match.[br][br]Which setup "Absolute Time", "Absolute Space", or "Relativity" achieves this result?[br](What is special about the correct setup? We'll see in a later visualization.)