Parallax is the observed displacement of an object caused by the change of the observer's point of view. In astronomy, it is an irreplaceable tool for calculating distances of far away stars. When you ...

Galileo's 1610 telescopic observations of Venus's phases provided evidence supporting a heliocentric model, as these phases could only occur if Venus orbited closer to the Sun than Earth. Stellar ...

IN this school-book of three hundred and twenty-six pages the authors have arranged a course on trigonometry which should be most useful to those studying this subject for the first time. The book may ...