After thinking about it for quite some time, I've decided that, in my opinion, the Hubble Ultra Deep Field is the most important picture ever taken. While many argue that non-repeatable and awe-inspiring human events should be the root of "the most important picture," the HUDF shows that no matter how significant those pictures might seem, they are absolutely nothing on the scale of what really exists out there. A grain of sand on an infinite beach. I have never encountered any other picture that comes close to inspiring the simultaneous fear, awe, and wonder that this picture inspires. Thoughts?
What about the WMAP? It studied the CMB radiation and gives us evidence of the big bang, a flat euclidean universe, the amount and type of matter in the universe, and even more!
Sure, the ultra deep field is cool, but in importance the WMAP picture is waaay more important.
