Five Questions

1) What effects do centrifugal forces have on planets?:  We have these huge objects spinning at speeds that are very fast, given their diameters, but we never really note the effects of their spinning. As another question, do you get any Doppler effect around the edges of very large stars that are spinning rapidly relative to us?

  Centrifugal forces cause some planets, most notably gas giants like Jupiter, to bulge outwards.  However, the centrifugal acceleration on a planet like Earth is very small, less than 0.01 m/sec², so it is rarely noticed.

2) What, exactly, is gravity?:  How is it that two things as relatively small and far apart as the sun and the earth can be attracted enough that one would orbit the other?

  Gravity is, in fact, the bending of space-time.  Space-time, it would seem, is not 'flat'; gravity is often compared to a funnel, where you can roll an object in a circular path and it will continue to roll indefinitely, until friction causes it to stop.

3) Why are suns generally monocolored, but when a star blows up you get many different colors?:  Or are suns really monocolored at all?

  Suns radiate light in all regions of the spectrum; they appear whitish because these different wavelengths combine and are averaged, and are percieved as white.  When a star blows apart, its pieces separate, so the different frequencies are not averaged as they would be if they were seen in a single point.  But the greatest reason for the appearance that exploding stars appear very colorful is that they are viewed through filters that enhance the color differences so that details about the stars can be seen.

4) Why are most of the planets orbiting the sun coplanar?:  One would think that most of the planets' orbits would be in entirely different planes, but for some reason, the orbits seem to be basically, but not entirely, coplanar. Also, does this relation also apply to planetary moons?, are most moon orbits that we know of also coplanar, or are they different, and why?

  This question remains unanswered.

5) What are 'black holes'?:  I know that they were once thought to be stars so massive that gravity held all light from escaping them, but this would theoretically lead to a massive energy build-up that would cause them to blow up even more spectacularly than a supernova (if they are still active stars, under that much gravity). Also, I have heard that energy has been detected coming out of black holes; is this true, and if so, doesn't it negate the previous belief?

  Black Holes are blocks of matter so dense and massive that nothing can escape from them, not even light.  It is believed that at the center of black holes, there is an 'undefined' point in space-time, a point that does not exist; this, of course, cannot be proved because it is impossible to send information out of a black hole.  The energy 'coming out of' black holes is actually radiation from particles right around the event horizon, the point beyond which nothing can escape from the black hole.  A particle/antiparticle pair appear in the region around the event horizon; normally, they would anhillate each other, but one sometimes appears inside the event horizon while the other appears outside it.  The one cannot escape the black hole; the other does escape, and is detected as radiation.