This app can be opened directly in the geogebra site using this link: https://www.geogebra.org/classic/ventqghr
Three checkboxes allow the selection of three related projections.
Without any of them being selected, we can see the basic skeleton for these projections. A fixed point (pole), a horizontal segment (scale) and a point on it which can be moved. A straight line (projector) joins the pole with the scaling point.
-Choosing the "bismar" box (blue) presents the construction for the bismar scale as presented elsewhere in this same webpage. The projection on a vewrtical (blue) line offers the measurement (Mass) af the scale. where regular points mark increasing mass values.
-Choosing the "Euclides" box (green) presents an Earth´s section (meridian) on which several points with increasing latitudes are marked.
-Choosing the "Minkowski" box (red) presents a section of a mass-shell where several points with increasing rapidities are marked.
Moving the point on the scale in order to fit the projections of the regular scales allows to see where the scale derives from regular evenly-spaced measurements.This app can be opened directly in the geogebra site using this link: https://www.geogebra.org/classic/zyktqags
Four different cross-ratios are presented (you can select them using the checkboxes)-Euclidean (green)-Minkowskian (red)-bismar scale (blue)-General (tilted plane, black)