One theory of atheism says that the cross in christianity is derived from the shape of the stars,so i just observed the night sky on dec 25 and this is how it looked in the east side.
Ok it may be looking gibberish, let me explain, my artistic skills are not so great so just assume that the black and white background is the night sky and yellow spot's are the important stars. The three small stars in the middle are the "orion belt", which many would be familiar with and the two stars to it's left and right, i am not sure of it's names and the bright star at the bottom is called "sirius". This is the theory, on dec 25 the orion belt will be in straight line with the sirius star and parallel to the other two stars, just joining those stars forms a cross. There is another theory relating this which deals with the birth of christ and the three kings(orion belt) guided by a star(sirius) come to meet the lord who gives them light(it's actually birth of a new year from when the sun starts to rise and days get longer than the nights) and when the phenomenon occurs these stars are in a shape resembling the cross.
So what i am trying to say is that during the olden days when people wrote about certain special things occurring in nature like these, they wrote it down as stories and as age evolved these stories became myth's and the character's involved became gods.There are many other different theories like this and this one is just a small part of the big delusion. Source for this theory is the zeitgeist documentary.
Of course, this post is written in an atheistic point if view, so any theist(especially christians) may feel offended , so warning don't read if you are a theist and i am not responsible if it hurts your beliefs and feelings.