In eighth grade, science teachers may have explained to their students that the world would end when the sun expanded to such a size that it would explode, destroying all the planets in its vicinity. Of course, more knowledgeable folks (http://wiki.answers.com/Q/When_will_our_sun_explode and http://answers.yahoo.com/question/index?qid=20080129174949AAJEYmH) have commented that the sun actually will not explode but will bulge out and essentially "melt" the earth... (although perhaps by then scientists may have discovered a way for living creatures to withstand the heat, or we will all have already annihilated each other through nuclear war or fallen to our demise through some other catastrophe).

In terms of "Judgment Day" -- there have been numerous predictions in the past that have not come true. Back in May, news channels focused on "May 21st" as the date for the end of the world (see http://www.csmonitor.com/Science/2011/0518/Judgment-Day-May-21-When-will-the-world-actually-end). Other failed predictions include October 22, 1844; 1806; December 21, 1954; 2000; October and November 1982 (http://www.csmonitor.com/Science/2011/0518/Judgment-Day-Five-failed-end-of-the-world-predictions/October-22-1844).   

Many have also been waiting for the world to end in 2012 (see: http://abcnews.go.com/International/story?id=5301284&page=1) -- as attributed to Nostradamus (http://www.december2012endofworld.com/nostradamus-2012). We still have over a year to observe whether this will happen, or whether something will happen sooner or later. At this point, that's the best answer we can offer -- the world will end... sooner or later.

One formula for calculating the air speed velocity of birds is here: http://style.org/unladenswallow (which estimates that the airspeed velocity of an unladen European Swallow is 10 meters per second).

Note that sparrows are different from swallows and, according to WikiAnswers, swallows are on average 20 g heavier then sparrows (weight varies depending on species). Also according to WikiAnswers (http://wiki.answers.com/Q/How_fast_can_a_sparrow_fly), a sparrow can fly between 16 and 19 MPH (25-30 Km/h). So swallows generally are faster than sparrows.