Subject Areas: Geography, Astronomy, Trigonometry, Geometry, Analytical Geometry Other keywords: triangulation, trilateration, parallax, parsec, surveying, law of sines, law of cosines, Pythagoras, Pythagorean, GPSHow can I know how far away something is without measuring it directly?How do astronomers know how far away other planets and stars are?What is the difference between triangulation and trilateration?Use this exercise to teach answers to the above questions.