There are things that scientists of past had worked out - but we don't know exactly how they did so. If you know any post here please. E.G. I don't remember exactly, but it goes sumfin along the lines of an ancient Greek scientist who measured angles of shadows (or is that the duration in time) simultaneously in two places very far apart in Egypt during an eclipse- somewhere in the north and far south I tink. He used this to work out some measurement about the sieze of the earth or latitudes or something. I'd assume he had a companion....but that could be wrong (?) NO-NONE KNOWS HOW HE DID IT.