Velikovsky tried to protect himself from criticism of his proposed celestial mechanics by removing the original Appendix on the subject from "Worlds in Collision", hoping that the merit of his ideas would be evaluated on the basis of his comparative mythology and use of literary sources alone. This strategy did not protect him: the Appendix was an expanded version of the "Cosmos Without Gravitation" monograph, which he had already distributed to Shapley and others in the late 1940s — and they had regarded the physics within it as egregiously in error.