# Calibrating Bob's Longitudinal Light Clock (robphy) - 2019

- Author:
- robphy

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

*[a 2019 update of https://www.geogebra.org/m/HYD7hB9v#material/UBXdQaz4 ] This is the fourth of six GeoGebra files (from my GeoGebra book Relativity on Rotated Graph Paper (robphy) - MAA2016 ) that were part of my MAA MathFest 2016 talk "Introducing Spacetime Geometry: Relativity on Rotated Graph Paper". http://www.maa.org/meetings/mathfest/program-details/2016/themed-contributed-paper-sessions*

*It describes aspects of my paper “Relativity on Rotated Graph Paper”, Am. J. Phys. 84, 344 (2016); http://dx.doi.org/10.1119/1.4943251. An informal introduction is presented at https://www.physicsforums.com/insights/relativity-rotated-graph-paper/*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.] 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. So, if Alice and Bob each send a light-signal when their own clock reads 2 ticks, we expect that the "clock readings when they receive the other's light-signal" match. Which setup "Absolute Time", "Absolute Space", or "Relativity" achieves this result? (What is special about the correct setup? We'll see in a later visualization.)