Background: Among the many methods astronomers have devised to measure the distance to planets, stars and neighboring galaxies, the most reliable are radar and parallax. Radar measures how long it takes a radio signal to reach earth, or bounce off an object. Because the speed of the signal is known, the distance to the planet or object can be calculated. Modern telescopes gather information from light that is not visible (electromagnetic radiation in the nonvisible spectrum, such as x- rays).
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.