Page:Astronomy for Everybody.djvu/266

We have described four methods of making this fundamental determination in astronomy, and in order that the reader may see just what degree of certainty and precision astronomical theory and measurements have reached, we give the separate results of these methods. The first column shows the parallax of the sun, which is the quantity actually used by astronomers. It is the same thing as the angle under which the equatorial radius of the earth would be seen by an observer at the distance of the sun from us. This is followed by the accompanying distance in miles.

The difference between these results is no greater than the liability of error wherever mathematical demonstrations and instrumental measurements of such extreme minuteness and complexity as these are required. From the close agreement between results reached by methods so widely different in their principles, we have a striking proof of the correctness of the astronomical views of the universe. Yet discrepancies exceeding a hundred thousand miles will not be tolerated by astronomers longer than is absolutely necessary.