case presented by Galileo. One was the absence of stellar parallax—the shift in the apparent position of the stars expected to result from their being viewed from different perspectives if the Earth were moving round an orbit in the course of the year. (We now know that this was not observable with seventeenth-century resources because the stars are so very distant from us.) Galileo placed great emphasis on the claimed confirmatory value of his explanation of the tides. We now know that he was completely