43) Approximately how soon might we expect an immediate response from a civilization that received the signal we sent to the globular cluster M13 (25,000 light-years away) in 1974?

37) Europa is located outside the Sun’s habitable zone and yet may be habitable. How can this be?

31) What kind of radiation we mostly search for in SETI data?

45) Suppose there are a million inhabitable planets in our galaxy, that one in ten are habitable, that one in a thousand planets with life at some point had an intelligent civilization, and that one in a hundred civilizations that has ever existed is in existence now. Given this, how many civilizations are in existence now?

34) The lack of large impact craters on the surface of Europa is consistent with

20) Why are there no impact craters on the surface of Io?

4) Which of the following cannot be determined with the Doppler technique?

50) Discoveries of extrasolar planets have shown us that

4) Which of the following cannot be determined with the Doppler technique?

39) Which of the following factors influence the surface habitability of a planet?