Newton 17th century calculated that Sirius (one of the brightest stars was 1 million times further away than the sun (1 million AU) Compared brightness of Sirius to brightness of Saturn Actual distance to Sirius = 550,000 AU

Measuring with Triangulation and Parallax Copy Measuring with Triangulation and Parallax Triangulation Method of measuring distance indirectly Done by creating an imaginary triangle between an observer and an object who’s distance needs to be discovered

Triangulation A) Create a baseline Copy Triangulation A) Create a baseline In this case line A to C B) Measure angles from the two points on the baseline In this case Angle A and Angle C C) Make a scale drawing of the triangle using a protractor and a ruler

Greeks Used triangulation 2000 years ago to calculate the distance between the Earth and Moon Baseline was 300 km Also knew they would have to take into account the curvature of the Earth.

Copy Parallax Is the apparent shift in position of a nearby object when it is viewed from two different points. Eg: Point finger close one eye then the other eye. Using Earths orbit Sightings are taken 6 months apart If a star is close enough it will appear to move relative to more distant stars