electromagnetic waves - At its closest approach, Mars is 56 million km from earth. How long would it take to send a radio message from a space probe of Mars to earth when the planets are at this closest distance?

Astronomical unit - What is the astronomical unit (AU), and how is it useful for Astronomers. How are the distances measured in our solar system. What is the relationship between the light year and the AU?

comets and asteroids - What knowledge do comets and asteroids provide to studies of the origin of the solar system?

cratering, volcanism - 3. Impact cratering, volcanism, tectonics, and erosion are the four major processes that affect planetary surfaces. Briefly explain any two. (Please provide all references and complete Urls)

General Astronomy Questions - a. Light is one form of electromagnetic radiation. What are electromagnetic waves and what other types are there besides light? Compare their wavelengths. b. How can the temperature, composition, and motion of an object be determined from its light spectrum? c. What are three ways astronomers learn about the interior of the Sun and thus infe...