What is a parallax unit?
You can measure an inch worm with a ruler and the trail of a snail with a tape measure. Road distance can be measured in terms of speed as in miles per hour. But the scope of the sky is limitless. We cannot use ordinary earthly units to cope with its cosmic dimensions. The parallax unit is a celestial angle used to measure the distance of a star. Angles and triangles have been used to compute distances since geometry was invented. Surveyors use them to measure the curved surface of the earth. For example, suppose you know the . length of the base line of a triangle and the size of the angle at each end. The straight sides must slant upward at these angles, taper together and meet at a certain point. Froth your known base line and its two angles you can complete your triangle and give an accurate report of the length of the two sides, plus the apex angle at the top. The parallax is the apex angle at the top of an immense celestial triangle. Like . all angles, it is measured in the degre
