What did gerardus mercator accomplish

The correct answer is Mercator map projection

Gerhard Mercator (his projection was ready in 1569). Make a cartographic projection of the Earth in which the almost spherical was reproduced as faithfully as possible on the flat surface

Maps existed previously, but not with the same mathematical precision in the projection. The Mercator projection is a cylindrical projection, that is, imagine the globe, then imagine that a cylinder was placed around it, touching it in the areas close to the Equator. Next, imagine that the parts of the Earth that do not touch the cylinder are pushed from the inside out, so that the entire Earth is touching the cylinder (which becomes its own shape). Then, the cylinder receives a cut in the North-South direction, remaining open and being possible to be placed flat.

he killed a bunch of jews so no one was spending money and the stock market rose again