In this excerpt from her 2009 AAI lecture, noted astronomer Carolyn Porco discusses the conflict between science and religion.

Galileo's first experiments focused on very simple things. He worried about motion; he worried about how things move; why if you push it, does it keep moving. Why doesn't it suddenly just change its direction? Why doesn't it suddenly accelerate? All these things that seem so obvious to us now--this is where we were in our study of the natural world and this is where Galileo focused.

But the method that he developed, this formulation of a hypothesis, the testing of the hypothesis by experiments and comparison with the natural world, and the development of a general principle that can be used to predict the outcome of future experiments, was a giant and powerful leap forward in its approach. And I think that the moment that Galileo first came up with this idea qualifies as the most subversive moment in the history of human kind--because it was at that moment when we finally began to have the means to verifiably separate truth from falsehood. And from then on it wasn't what some powerful monarch or church figure had to say which made it truth or not, nature herself was the final arbiter.

It's interesting to think about the scientific method as it applies to the existence of god. Because if someone were to give me the task of investigating the existence of god the way I would, say, investigate the motions of the bodies in the Saturn system, and required me to bring to bear on the matter all the training I had received about how to prove or disprove an idea, and then required me to write a scientific paper or publication on the subject, I can tell you right now that it would be a paper with no conclusions. There is no physical evidence whatsoever that can be presented or examined to prove directly that god exists. No one has yet captured god and brought him back to be examined in a scientific laboratory, and of course it is very difficult to prove that god doesn't exist--simply because it is very difficult to prove a negative.

Let me give you an example of how this would work. Take the case of my proving that I do or do not have cockroaches in my house. All I really need to do if I want to prove to you that I have cockroaches in my house is find one cockroach--dead or alive--or maybe even just the droppings of cockroaches, to convince a reasonable person to their satisfaction that I have cockroaches living in my house.