What happens if all the planets line up?

Actually it wont be "nothing major".

When all of the planets line up it will effect the earths temperature,the moons (resorting in water effects) and other natural disasters ie.earthquakes,volcanoes erupting,tornados,hurricanes etc...

The year of 2012 will have the next planet allignment...according to scientist this will take place during 21st of December,the same day the mayans predicted the world to end (or the end of Mayan calander).